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Accelerating nitriding is an interesting topic in chemical heat treatment of ferrous parts. In order to have a deeper understanding of the catalysis principles of rare earth in nitriding, a Q235 carbon steel and a Q235RE steel micro-alloyed with rare earth elements La and Ce were nitrided respectively by plasma nitriding and gas nitriding. The microstructure, phase constitution, and composition of the nitrided specimens were analyzed. The hardness profile of nitriding layer and the brittleness of surface compound layer were measured. The results demonstrate that the Q235RE specimens obtained a higher hardness and deeper effective hardening layer than the Q235 specimens without rare earth microalloying. The rare earth catalysis effects were presented as the acceleration of nitrogen diffusion and the inhibition of nitride precipitation in the diffusion layer of the Q235RE specimens. In addition, the surface compound layer of the Q235RE specimens showed higher toughness and better adhesion to the matrix than that of the Q235 specimens, which is considered to be strongly related to the rare earth elements diffused into the compound and the enhanced residual compressive stress in the layer. • La-Ce rare earth elements microalloying has a significant catalytic nitriding effect on Q235 low-carbon steel. • La-Ce can inhibit the precipitation of needle-type Fe4N nitride. • RE-containing Q235RE specimens have higher hardness and depth of the effective hardening layer. • RE-containing Q235RE specimens have better toughness in the compound layer. [ABSTRACT FROM AUTHOR]

In this study, a rust/phytic acid (rust/PA) conversion layer was prepared on rusty mild steel by dipping rusty steel panels into a phytic acid solution. After treating with phytic acid, the free phosphate group in the conversion layer chelated with Fe3+ and generated insoluble salt, which could form a new dense conversion layer. The dense rust/PA conversion layer effectively strengthened the interfacial bonding between the coatings and rusty metal substrate and exhibited good corrosion protection and defect healing abilities. [ABSTRACT FROM AUTHOR]

After carburizing and quenching, the low-carbon alloy steel 12Cr2Ni4A exhibits high strength and good toughness, making it widely used in the manufacture of aeronautic gears. However, the stress generated during the carburizing and quenching process can lead to plastic deformation, which can severely affect the machining accuracy of aeronautic gears. Therefore, understanding the evolution of internal stress and the distribution of residual stress during quenching, influenced by carburizing, is crucial for effectively controlling such deformation. In this study, the influence of carbon content on material performance parameters was considered. A linearly reinforced thermo-elastic-plastic constitutive equation coupled with phase transformation was established to address the non-uniform variation of the dynamic behavior of quenching phase transformation after carburizing. Based on the secondary development interface of the finite element software Abaqus, phase transformation dynamics and thermos-elastic-plastic mechanics were introduced to realize the accurate modeling and simulation calculation of the carburizing quenching stress field. The proposed model for calculating carburizing quenching stress was verified by measuring the residual stress and analyzing the microstructure of the carburizing and quenching cylindrical specimens. The results show that, compared with direct quenching, in the carburizing quenching of cylindrical specimens, martensitic transformation first occurred in the subsurface region, then in the core, and finally in the surface layer. During the carburizing quenching process, larger tensile stress was generated on the surface, increasing the risk of quenching cracks. The transformation stress caused by carburization was the main reason for the spoon-shaped distribution of residual stress, and a higher carburization depth could lead to a smaller surface residual compressive stress and a larger depth of the maximum residual compressive stress layer. This study elucidates the coupled mechanism of phase transformation and internal stress evolution during the carburization quenching process, providing a choice of process parameters for the optimal carburization quenching conditions required for maximum fatigue life stress distribution. [Display omitted] • A method for modeling carburizing quenching is proposed. • The stress evolution of quenching and carburizing quenching is analyzed. • Transformation stress is the main driver of spoon-shaped stress distribution. • Carburization heightens the risk of longitudinal quenching cracks in the workpiece. [ABSTRACT FROM AUTHOR]

Corrosion-resistant hydrophobic magnetite coatings on mild steel surfaces were developed by immersion method. The effect of steel surface roughness (R a) on its hydrophobicity was systematically studied using contact angle measurement (CAM), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The corrosion resistance of hydrophobic magnetite coatings was evaluated using a potentiodynamic polarization test. The durability of the coatings was assessed in air, tap water, and 3.5 wt% NaCl environments. Hydrophobic magnetite coating with a water contact angle of 146-152° showed excellent resistance to corrosion, longevity in atmospheric air, and significant self-cleaning properties. The primary focus of this study was to develop a quick and simple immersion technique to create hydrophobic surfaces on mild steel. Results suggest that surface roughness plays a significant role in surface hydrophobicity, and enhancing the hydrophobicity of mild steel improves its corrosion resistance. • Superhydrophobic surface was prepared on mild steel samples using a simple immersion method. • Surface roughness affects hydrophobicity and thus, the overall performance of the coated surface. • A high static contact angle of 152° and a low contact angle hysteresis of 2o is achieved. • Superhydrophobic surface showed excellent corrosion resistance, durability, and self-cleaning behavior. [ABSTRACT FROM AUTHOR]

An investigation into how Panthenol affects the corrosion of mild steel in 1 M hydrochloric acid was carried out, specifically its adsorption behaviour and the mechanism by which it inhibited corrosion and for this electrochemical analysis techniques, weight loss, scanning electron microscopy, atomic force microscopy, contact angle measurements has been used. Also, the theoretical study which includes study of global reactivity descriptors E HOMO , E LUMO , energy gap (∆E) etc. and molecular dynamics (MD) simulations in aqueous phase have been used to simulate the real situation. This study confirmed a high inhibition efficacy of 90 % at a concentration of 400 ppm. The electrochemical analysis demonstrated that as the concentration of Panthenol increased, there was an apparent reduction in the value of j corr and an upsurge in the value of R ct. In case of potentiodynamic polarization, the value of j corr came out to be 144 μA cm−2 and in electrochemical impedance spectroscopy, the value of R ct came out to be 125.32 Ω cm2 at 400 ppm. The surface morphological investigations revealed the deposition of an extensively protective coating on the mild steel surface. Calculated values of roughness (average and root mean square in nm) in the present study shows a reduction in roughness (in the acid the values were 401 nm, 518 nm respectively and acid with Panthenol, the values were 56.9 nm and 82.5 nm, respectively). In quantum chemical calculations, the calculated value of ΔE came out to be 5.098, validating the strong tendency of inhibitor to retard the corrosion. The investigation revealed that Panthenol is an effective and environmentally friendly inhibiting agent of corrosion for mild steel in a 1 M HCl solution. Additionally, the theoretical findings reiterated the experimental results obtained in this study. [Display omitted] [ABSTRACT FROM AUTHOR]

The preparation of Ti-alloy coating on the steel surface via laser cladding is very easy to form Fe-Ti phase and large tensile residual stress, which is not conducive to the performance of Ti-alloy coating. Here, Ti-6Al-4V coating (TC4-coating) was prepared on the mild steel substrate using laser cladding technology with Ni-alloy as the interlayer, and the Fe-Ti phase inside was completely suppressed. Increasing the powder feeding rate and scanning speed can change the undercooling of the alloy melt and the preferred growth orientation of the grains, while limiting the abnormal grain growth and grain boundary segregation, which is beneficial for grain refinement and equiaxed crystal formation. Reducing the scanning speed and powder feeding rate can increase the molten pool lifetime, thereby increasing the dilution rate of the coating and facilitating the formation of Ti 2 Ni phase. The abundant Ti 2 Ni inside the coating gives the TC4-coating greater microhardness (>500 HV0.1) and better corrosion resistance (I corr of 7.00 × 10−8 A·cm−2). Grain refinement of the coating texture caused by the increase of powder feeding rate and scanning speed, as well as the high content of β-Ti phase and martensite structure, can improve the adhesion and shear strength of TC4-coating (386 ± 31 MPa). [Display omitted] • Ni interlayer can effectively inhibit the Fe-Ti phase and improve the performance of TC4-coating. • Ti 2 Ni endows the TC4-coating greater microhardness and better corrosion resistance. • β-Ti phase, martensitic structure and fine grains are conducive to improving the mechanical properties of TC4-coating. [ABSTRACT FROM AUTHOR]

In this study, a high entropy alloy (HEA) coating of CoCrFeNiMnTi 0.3 with good mechanical and tribological properties has been successfully manufactured on a mild carbon steel by the powder-bed arc additive manufacturing (PBAAM) technique. The HEA coating is consisted of a face-centred cubic (FCC) solid solution phase together with a small amount of in-situ formed fine TiN and TiO 2 precipitates. The HEA coating has quite uniform chemical composition, microstructure, and hardness. The average Vickers microhardness is about 185.6 ± 3.1 HV 0.1 in the HEA coating while 148.9 ± 3.4 HV 0.1 in the mild carbon steel substrate. Besides, in comparison with the substrate, the PBAAM manufactured CoCrFeNiMnTi 0.3 HEA coating always shows a lower friction coefficient and specific wear rate for a given wear testing temperature from RT to 800 °C. Particularly, the friction coefficient and specific wear rate of the HEA coating is only about 71.63 % and 3.68 %, respectively, of that of the mild carbon steel substrate at 800 °C. It can be concluded from the findings in this work that cladding a protective CoCrFeNiMnTi 0.3 HEA coating on the mild carbon steel by PBAAM technique is beneficial into reducing both friction and wear, and thus is an effective strategy to significantly improve the application potential of mild carbon steel. • CoCrFeNiMnTi 0.3 HEA coating has been successfully fabricated by the powder-bed arc additive manufacturing method. • CoCrFeNiMnTi 0.3 HEA coating exhibits an average Vickers microhardness of about 185.6 HV. • Average friction coefficient of CoCrFeNiMnTi 0.3 HEA coating decreases from around 0.639 at RT to 0.356 at 800 oC. • CoCrFeNiMnTi 0.3 HEA coating always exhibits lower friction coefficient and wear rate than mild carbon steel substrate. [ABSTRACT FROM AUTHOR]

In the present study, the microwave irradiation approach was used to synthesize two methylimidazolium-based ionic liquids (MImILs), specifically 1-Heptyl-3-methylimidazolium bromide [HMImBr] and 1-Benzyl-3-methylimidazolium bromide [BzMImBr]. Several spectroscopic methods have been used to characterize the produced compounds. Gravimetric and electrochemical techniques were employed to examine their ability to prevent corrosion of the mild steel in a 0.5 M sulfuric acid solution. Amongst all the evaluated ionic liquids, [BzMImBr] having an aromatic ring instead of hexyl ((–CH 2) 5 –CH 3) hydrocarbon of [HMImBr] manifests better inhibition efficiency of 95.49 % at 1000 ppm concentration. The experimental ionic liquids negatively impact both the anodic and cathodic Tafel reactions, exhibiting mixed-type inhibition properties, as demonstrated by the findings of the potentiodynamic polarization investigations. Through their adsorption employing their electron-rich centres, the examined ionic liquids create a corrosion-protective covering, and their adsorption follows the Langmuir isotherm model. Negative values of ΔG ads indicate the spontaneous nature of [HMImBr] and [BzMImBr] adsorption, whereas values between −20 and −40 KJ mol−1 indicate the physio-chemisorption mode of adsorption. Energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and field emission-scanning electron microscopy (FE-SEM) techniques were used to assess and evaluate surface morphology. The DFT-based analysis indicates that aromatic rings played a significant role in the charge sharing (donation and acceptance) in [BzMImBr]. [Display omitted] [ABSTRACT FROM AUTHOR]

In the present work, a novel anti-corrosion coating material was developed using diphenolic resin and multiwalled carbon nanotube (MWCNT) based nanofillers. In this concern, phenylmethylene diphenolic resin (PMD) and its 2-(4-methylbenzyl) oxirane derivative (PMDD) were synthesized using phenol and benzaldehyde. Silver-decorated MWCNT (MWCNT-Ag) and polyaniline (PANI) synthesized on MWCNT-Ag (MWCNT-Ag/PANI) were also fabricated and employed as filler materials to enhance the anti-corrosion performance of PMDD. The resins were analyzed by LC-MS and FT-IR, and the nanofillers were characterized using XRD, SAED, EDX, TEM, and XPS techniques. The synthesized PMD and PMDD and different weight percentages of fillers blended PMDD were coated on the mild steel (MS) sample using doctor blade method. The surface morphology and roughness of the coatings were examined by SEM and AFM analyses. The anti-corrosion ability of the coated samples was assessed by electrochemical impedance spectroscopy (EIS) and salt spray testing (SST). All the results showed an excellent anti-corrosion performance of PMDD by the incorporation of 0.2 wt% of MWCNT-Ag/PANI. Withstanding the 5 wt% NaCl salt spray atmosphere for about 144 h and >460 days in 3.5 wt% NaCl solution reflects its strong barrier property and long-term durability. The cross-linking of resins, blockade of defects by nanofiller and an additional protective layer developed by conductive PANI make the coating material efficient and durable in highly corrosion environments. [ABSTRACT FROM AUTHOR]

Hydrophobic coatings have generated growing interest in mitigating the deterioration of metals against corrosion due to their water-repellency properties. For organic-inorganic hybrid (OIH) coatings derived from Sol-Gel, enhancing their hydrophobicity is an efficient way to limit the diffusion of corrosive species to the substrate through the mesopores and low-density zone. This research successfully applied crack-free multicomponent Sol-Gel coating based on zirconium oxide and silicate on mild steel. By doping Octadecyltriethoxysilane (ODTES) with an alkyl group (C18), the coating's hydrophobicity was tailored either on its surface or within the mesopore structure. It was proved in the first place that the enhancement of corrosion resistance is mainly due to the microcapillary effect rather than the surface wettability. Moreover, the effect of the alkyl group addition depends strongly on the coating's microstructure, which is determined by the Sol composition. The most promising composition arose from balancing the coating's density and hydrophobicity. So-prepared samples showed a low current density with increasing potential, which is four orders of magnitude lower than that of the bare substrate. Until a critical potential, denoted E c , the corrosion species were driven by the electrostatic force to the underlying metal. [ABSTRACT FROM AUTHOR]

This study examines the wear resistance of a new amorphous coating fabricated by APS thermal spraying using industrial grade pig iron. The coating's performance is evaluated under varying plasma power conditions at three distinct loads of 40, 50, and 60 N. Scanning electron microscope (SEM) micrographs are analyzed to measure the porosity and thickness of each coating. The average porosities (%) of S1-S4 and S5-S8 coatings are 07 ± 03 and 14 ± 04, respectively. The rates of wear between reference mild steel and among all coatings at three different loads are evaluated, compared, and correlated with plasma powers to arrive at optimal level of plasma power. The plasma power of 30–35 kW corresponding to the least wear rate is found to be optimal at three different loads. Further, the generated debris particles are subjected to morphological and phase analysis by scanning electron microscopy and Fourier-transformed infrared spectroscopy. Detailed microstructural analysis of worn surfaces indicates that the wear modes include delamination, abrasion, and oxidation • The sliding wear response of a novel pig‑iron based amorphous coating was studied. • The sliding wear response of each coating was recorded at three different normal loads. • Optimal values of the plasma power are reported for the coatings. • The wear rates of all the coatings were measured/calculated and compared. • Correlations among load, coating thickness, porosity and plasma power are provided. [ABSTRACT FROM AUTHOR]

The applications of mild steel in harsh service environments are limited due to its poorer mechanical properties and less favorable corrosion resistance. In this work, a martensitic stainless steel cladding layer is manufactured on the surface of the mild steel via heterogeneous double-wire arc directed energy deposition (DED). Two gas metal arc (GMA) torches are used, with heterogeneous metal wires of ER316L and ER70-G as raw materials. The wires, with wire feed speeds of 5.6 m/min and 2.4 m/min, respectively, melt together to form a common molten pool, which solidifies to create a cladding layer. The formation characteristics, microstructure, mechanical properties, and corrosion resistance of the cladding layer are investigated. The results reveal a well-formed cladding layer without macroscopic defects. The microstructure of the cladding layer is composed of martensite and austenite. Compared with the mild steel substrate, the cladding layer exhibits a 170 % increase in microhardness, a 160 % increase in strength, and a 1070 % increase in corrosion resistance. The results of this work contribute to the high-efficiency and low-cost preparation of a high-strength, high-hardness, and corrosion-resistant Fe-based cladding layer (F-BCL) on mild steel. • Fabricating a martensitic stainless steel cladding layer on mild steel • Two heterogeneous wires of ER316 and ER70-G are used. • Martensite and austenite constitute the microstructure. • Mechanical properties and corrosion resistance are significantly improved. [ABSTRACT FROM AUTHOR]

The co-deposition of natural particles was studied in zinc electroplating on mild steel in the acidic sulfate bath aiming a composite coating. Despite most papers reported the effect of natural extracts in such process, the evaluation of natural particles adhered to the coating was not explored yet. The process efficiency, surface morphological changes, and corrosion resistance were evaluated in different concentrations of avocado seed powder (ASP, Persea americana), cocoa bean shell powder (CBSP, Theobroma cacao), and garlic peel powder (GPP, Allium sativum). In general, the current efficiency was not significantly influenced by the presence of any natural particles, reaching values over 90 %. The presence of natural particles impacted the active sites on the substrate surface, modifying the grain growth assessed by scanning electron microscopy (SEM) analysis. The GPP samples showed better visual aspect and higher compactivity. By Fourier transform infrared spectroscopy analysis, such natural particles are constituted by molecules of long carbon chains with chemical groups – amines, carboxylic acids, and phenols. Hence, the presence of natural particles in the coating layer led to different responses in the contact angle test, where GPP samples showed higher wettability (θ < 90°), followed by ASP and CBSP samples (θ > 100°). Such behavior indicates a greater bath penetration during the electroplating process in the presence of more hydrophilic particles, which may have resulted in the refined deposits of the GPP samples. The concentration of 0.330 g/L GPP presented higher impedance modulus (6548.3 Ω.cm2 at 0.03 Hz) in the electrochemical impedance spectroscopy (EIE) and reduced the anodic ionic current density at least four times in the scanning vibrating electrode technique (SVET). The same was observed in the salt spray test (SST) adapting ASTM B117 , which revealed to be sensitive enough to indicate that the 0.330 g/L GPP sample showed greater corrosion resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Damage caused by corrosion triggered metallic constructs to be malfunction and collapse, which resulted in financial loss. For this reason corrosion preventing coatings is applied to preserve the worth of industrial assets. Polyaniline (PANI) is one of the members of conducting polymers to use as protective coatings. However, certain co -additives like natural compounds have significantly uplifts the effectiveness of polyaniline (PANI). Herein, the incredible properties of gum rosin (GR) that boost the inhibitory performance of PANI are presented. The PANI patched with GR was synthesized by inverse emulsion polymerization. The UV–Visible and FTIR analysis confirms the synthesis of PANI-gum rosin (PANI-GR) composite, whereas, the thermogram of synthesized composite shows outstanding thermal stability to 533 ° C. SEM analysis reveals a bi-layered morphology with porous PANI layer which is superimposed by fibrous layer of gum rosin. PANI-GR was soluble in numerous common organic solvents, including chloroform, methanol, n-heptane, toluene, DMSO, NMP, and acetone the maximum solubility potential was observed to be 7.8 % (w / v). The corrosion preventing ability of the PANI-GR composite was evaluated through OCP, EIS and Tafel analysis. A significant uplift was found in the OCP potential (E OCP) to −0.38 V which might be due to the existence of a PANI-GR layer with prominent anticorrosive properties. The synthesized PANI-GR composite layer reveals a significant reduction in the corrosion of mild steel surfaces with corrosion efficacy up to 92 % in a diprotic acidic medium. In a nut shell, the potential of PANI-GR composite is demonstrated here in order to resolve problems of PANI, leading to significantly save the country assets. • Ecologically friendly and Novel PANI-GR composite • Superior solubility in common organic solvents • Significant uplift in the OCP potential (E OCP) • Extraordinary corrosion prevention ability up to 92 % [ABSTRACT FROM AUTHOR]

This study explores the novel application of Asphodelus Tenuifolius aerial extract (ATAE) as a corrosion inhibitor for mild steel in a 0.5 M HCl acidic environment. By utilizing techniques such as electrochemical measurements, gravimetric analysis, SEM, and CA assessments, the inhibitory potential of ATAE has been comprehensively evaluated. The results revealed a concentration-dependent enhancement in corrosion resistance, classifying ATAE as a mixed-type inhibitor by measuring the anodic (β a) and cathodic (β c) polarization slope values of 108.89 and −129.33 mV/dec. The peak inhibition efficiency was observed at 250 ppm, reaching an impressive IE% of 94.40 % at 298 K (Kelvin). The electrochemical analysis demonstrated a significant increase in charge transfer resistance (R ct) and polarization resistance (R p) values, coupled with a decrease in Constant Phase Element (CPE.Y o) value to 162.94 μF, indicating heightened corrosion inhibition potential. Additionally, Theoretical calculations emphasized a strong interaction between ATAE and mild steel surface, characterized by a low energy gap (ΔE), indicating excellent anti-corrosion abilities at the micro-level. This study positions ATAE as a promising corrosion inhibitor, offering insights for further research in corrosion prevention strategies using a sustainable corrosion inhibitor. [Display omitted] • The corrosion inhibition property of Asphodelus Tenuifolius aerial extract (ATAE) has been investigated. • ATAE acted as a mixed type inhibitor with 94.40 % efficacy at 250 ppm, as per galvanostatic polarization technique. • SEM and EDS studies revealed the development of defensive coating on the metallic surface. • MD and MC simulation studies have been used to predict the reaction site in a molecule. • The experimental results perfectly correlated with theoretical results. [ABSTRACT FROM AUTHOR]

The C content of the steel matrix has significant influence on the growth mechanism, microstructure and properties of the chromized layer. However, the relevant research literature is scarce. In this paper, seven kinds of low carbon alloy steels with C content ranging from 0.08 wt% to 0.45 wt% were selected as matrix for chromizing experiments under the same parameters. The effects of matrix C content on the growth mechanism, growth rate, structure and properties of the chromized layer were discussed. The results show that the chromized layer is composed of outer porous (Cr, Fe) 23 C 6 and (Cr, Fe) 7 C 3 carbides layer and inner dense Fe Cr phase layer for matrix with C content lower than or equal to 0.2 wt%. While when the matrix C content is >0.2 wt%, the chromized layer becomes three-layer structure: the surface (Cr, Fe) 23 C 6 phase layer, the middle (Cr, Fe) 7 C 3 phase layer and the bottom Fe Cr solid solution phase layer. The structure and thickness of Cr 23 C 6 phase layer formed in the early stage of chromizing play a decisive role in the inward diffusion of surface adsorbed Cr atoms and the growth rate of the permeated layer. With the C content of the matrix increases from low(0.08wt%C) to high(0.45wt.%C), the dense layer phases in chromized samples gradually changes from Fe Cr alloy phase with BCC structure to (Cr, Fe) 23 C 6 and (Cr, Fe) 7 C 3 carbides. And the wear resistance of the chromized layer increase. However, when the matrix C content is above 0.4 wt%, the structure and phases of the chromized layer are almost not affected by the matrix C content, so are the thickness and wear resistance. The results are helpful to the selection of steel matrix composition for chromizing and the optimization of chromizing process. • The C content of matrix has an important effect on the growth mechanism of the chromized layer. • The initial formed Cr 23 C 6 phase layer plays a decisive role in the growth rate of the chromized layer. • When the matrix C content is above 0.4 wt%, the properties of chromized layer are almost not affected by the matrix C content. [ABSTRACT FROM AUTHOR]

This study used PEO treatment and a TaOH-rich electrolyte to coat AISI 1020 low-carbon steel to enhance its anti-corrosion and wear properties, targeting its usage as a medical device. The effect of time, duty cycle, frequency, and Ta(OH) 5 concentration on the chemical and phase composition, topography, wettability, and roughness of the obtained coatings were addressed. The results indicated that the Fe-based oxide coatings had a rough and super-hydrophilic surface. The phase composition of the coatings was formed mainly of Ta 2 O 5 , hematite (Fe 2 O 3), and a minor amount of rust (Fe(OH) 2), with the chemical analyses also indicating the presence of some absorbed molecules. Once the best PEO parameters were established (200 V, 5 min, 60 %, 1000 Hz, and 40 g/L Ta(OH) 5), the previous mechanical, corrosion, and wear tests evidenced the positive effect of the chemical species deposited in the surface when compared to the substrate. In this way, PEO treatment applied on AISI 1020 low-carbon steel in a TaOH-rich electrolyte can be an adequate alternative to produce low-cost materials for medical devices, especially as a potential substitute for stainless steel and titanium-based alloys in surgical instruments. [Display omitted] • PEO parameters affected the surface characteristics of low-carbon steel differently. • PEO treatment induced the formation of Fe 2 O 3 and diminished Fe(OH) 2 on the surface. • Fe 2 O 3 and Ta 2 O 5 protected the surface against corrosion in saline solution. • PEO-treated sample had superior wear resistance due to adhesive mechanisms. • PEO-treated low carbon steel can be a proper alternative for use as medical devices. [ABSTRACT FROM AUTHOR]

The Fe Ti brittle phase is a key factor affecting the performance of titanium alloy coatings. Reducing the Fe Ti brittle phase in the texture is one of the effective ways to prepare titanium alloy coatings with excellent performance. This work uses laser cladding technology to prepare Ti-6Al-4V coatings with excellent mechanical properties and corrosion resistance on the surface of mild steel. The relationship between the cladding process, microstructures, and performances of Ti-6Al-4V coating has been revealed. Low laser power and high powder feeding rate are beneficial for the formation of a more complete microstructure of Ti-6Al-4V coating, which can significantly reduce keyholes and microcracks at the Fe Ti interface zone. The shear strength of the 1000 W-1.5 r/min specimen is the highest (88.8 ± 7.1 MPa), and the high-angle grain boundaries (HAGBs) of Ti are used as the blocking site for cracks to prevent the propagation. The 1000 W-1.5 r/min specimen has a corrected E corr (−0.3145 V vs. Ag/AgCl) and smaller I corr (0.3182 μA·cm−2), exhibiting excellent corrosion resistance. When the Ti-6Al-4V coating is intact, the TiO 2 passivation film formed on the surface can effectively prevent the corrosion process from progressing. When there are through cracks caused by residual stress in the Ti-6Al-4V coating, the electrolyte solution can reach the Fe Ti interface zone through microcracks to corrode the Fe in the substrate, leading to coating failure. The research results provide valuable reference for the preparation of titanium alloy coatings with excellent performance on the surface of mild steel. [Display omitted] • The increase of powder feeding rate is beneficial to the formation of dendrites and equiaxed grains. • The increase in HAGBs of Ti is conducive to improving the shear strength of Ti-6Al-4V coating. • The increase in LAGBs of β-Ti on the surface can improve the corrosion resistance of coating. • The decrease in LAGBs of Fe Ti phase can improve the corrosion resistance of coating. [ABSTRACT FROM AUTHOR]

Ultrasonic impact technology was applied to improve the property of laser cladded CoCrFeNiMo x (x = 0, 0.25, 0.5, 0.75) high entropy alloy coatings on the surface of low-carbon steel. The phase structures and the microstructural characteristics were studied in detail through X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The microhardness distributions, wear resistance, and corrosion resistance of the samples are illustrated using a microhardness tester, a micro-friction and wear tester, and an electrochemical test system. Single FCC phase solid solution was identified to be the main phase structure, with the interdendritic σ phase precipitating with the increasing Mo content. Although ultrasonic impact treatment did not change the phase composition of the high-entropy alloy (HEA) cladding coatings, evident plastic deformation and broken σ phase appeared near the surface of the impacted layers. Through the combined effects of dislocation, fine-grain, and dispersion strengthening, the microhardness of the CoCrFeNiMo x coatings was improved after ultrasonic impact treatment. In addition, ultrasonic impact treatment decreased the surface roughness and increased the wear resistance, and the main wear mechanism of the impacted layers changed from fatigue spalling to abrasive wear. The wear mass of the ultrasonically impacted layers was approximately 92 % of the laser cladded CoCrFeNiMo x coatings. Furthermore, ultrasonic impact treatment improved the corrosion resistance of the HEA coatings. • Microstructure examinations in CoCrFeNiMo x cladding coatings before and after UIT were conducted. • UIT brings out the refined grains, dislocation multiplication and broken σ phase. • UIT enhanced hardness, wear and corrosion resistance of cladding CoCrFeNiMo x coatings. [ABSTRACT FROM AUTHOR]

Progressing the anti-corrosion performance of thin-film coatings has always been the focus of researchers. In this research, a novel high-resistance inorganic coating against corrosion was developed. For this aim, the steel plates treated with the Mn ion-containing zinc phosphate conversion coating were prepared and then covered with a layer of crystalline MOF nanoparticles. A robust self-healing effect was provided by the cerium cations loaded into the MOF thin coating, pores. FE-SEM, BET, XRD, and XPS were applied as the main analyses to characterize the successful formation of the conversion coating and the MOF grown on its layer. The uniformly grown MOF single crystals (particle size: 200–300 nm) could cover the porosities of the zinc phosphate coating so that no rust was detected after 600 h of keeping the sample in a very aggressive environment (salt spray chamber). Also; based on PDP results, the modified coating (ZPMnMOFCe) showed a sixty-fold drop in the corrosion rate compared to the uncoated plate. Meantime; after 24 h of exposure, its log| Z | 10mHz was two orders of magnitude higher than that for the untreated mild steel. [Display omitted] • A cerium-loaded Zn-MOF was developed on zinc phosphate conversion coating as a self-healable monolayer thin coating. • XRD and FE-SEM results showed the successful growth of MOF on the ZPMn coating. • Characteristic signals of the Ce after loading in ZPMnMOF coating was clearly shown in the XPS of the ZPMnMOFCe coating. • EIS and PDP results proved the extraordinary corrosion protection performance belongs to MS/ZPMnMOFCe sample [ABSTRACT FROM AUTHOR]

The present study successfully applied Ni Cu and Ni-Cu/Al 2 O 3 composite layers on St37 steel substrates using sodium citrate and potassium oxalate as complexing agents. The alloyed Ni Cu and composite Ni-Cu/Al 2 O 3 coatings were scrutinized for their physical, mechanical, chemical, electrochemical, and tribological properties using various techniques including XRD, SEM/EDS, microhardness test, PDP, EIS, FESEM/MAP images, and dry tribological pin-on-disk wear analysis. The XRD patterns of the Ni-Cu/Al 2 O 3 composite coatings disclosed the presence of FCC crystal structure in both Ni and Cu phases, as well as the successful formation of Ni-Cu/Al 2 O 3 nanocomposite coatings on mild steel substrates. Incorporating Al 2 O 3 particles resulted in a 48 % increase in microhardness compared to Ni Cu coatings. Furthermore, Ni-Cu-Oxalate coatings exhibited a higher microhardness with respect to Ni-Cu-Citrate coatings. Varying the type of complex species in the Ni-Cu/Al 2 O 3 -Citrate coatings led to a 9.7 % increase in microhardness in regard to Ni-Cu/Al 2 O 3 -Oxalate coatings. The pin-on-disk wear analysis revealed that the Ni-Cu/Al 2 O 3 -Citrate coatings had a 35 % lower friction coefficient compared to Ni-Cu/Al 2 O 3 -Oxalate coatings. The composite Ni Cu coatings with reinforcing Al 2 O 3 particles exhibited superb wear resistance compared to the alloyed Ni Cu coatings. The morphology of the coating's surface was found to be more uniform and adhesive for the Citrate coating compared to the irregular-shaped Oxalate grains. The Ni-Cu/Al 2 O 3 -Oxalate and Ni-Cu/Al 2 O 3 -Citrate coatings demonstrated an outstanding improvement in specific wear rate approximately 94.1 % and 62.7 %, respectively, with respect to the Ni-Cu-Oxalate and Ni-Cu-Citrate coatings. The worn path analysis substantiated that the composite Ni-Cu/Al 2 O 3 and alloyed Ni Cu coatings were subjected to mixed adhesive, abrasive, plastic deformation, and delaminated wear mechanisms. Finally, the composite Ni-Cu/Al 2 O 3 -Citrate coatings showcased superior hardness, a more uniform and adhesive microstructure, and brilliant anti-wear properties. [Display omitted] • Using complexes of citrate and oxalate, Ni Cu coatings were successfully applied. • Composite coatings complexed with citrate had a higher porosity than composite coatings complexed with oxalate. • Citrate-complexed coatings absorb Al2O3 particles more efficiently than oxalate-complexed coatings. • Ni Cu alloyed coatings complexed with oxalate have a higher microhardness than citrate coatings. [ABSTRACT FROM AUTHOR]

Vanadium carbides are known as efficient reinforcing components for surface layers of steel parts. They provide good tribological characteristics of material under sliding friction conditions and against dry abrasive particles. Since wear conditions usually are quite severe, a thick coating is needed to provide the reliable protection of the part. The majority of currently used surfacing technologies ensure the coatings of insufficient thickness. For this reason, the non-vacuum electron beam cladding which is able to provide thick coatings is a reasonable alternative to other surfacing methods. This paper presents an analysis of the microstructure, micro- and nanohardness, elasticity, and tribological characteristics of coatings formed by non-vacuum electron-beam surfacing of vanadium and graphite-containing powder mixtures. In the course of the study, coatings with the average thicknesses of 1.8, 2.5, 2.6, 3.4 mm were formed on the surface of blanks made of medium‑carbon steel. Hardness of cladding layers was significantly improved compared to the low-carbon steel (by the factor of 5–7). The wear resistance of coatings under conditions of sliding friction was 5.8 times higher than the wear resistance of the base metal after quenching and tempering; the wear resistance of coatings under conditions of friction against fixed and loosely fixed abrasive particles was ∼2 and ∼4.8 times higher, respectively. Surface hardening of steel alloyed with vanadium and carbon derives from the presence of a martensitic matrix, ledeburite precipitates and a high volume fraction (14.5–29.5 vol%) of vanadium carbide particles of a dendritic form, which act as rigid barriers. • V+C powder mixtures were cladded on steel by non-vacuum electron-beam processing. • Cladding layers obtained on steel surface reached 2.6 mm. • The microhardness of the layer alloyed with V and C was 10...15 GPa. • VC dendrites, ledeburite, and martensite contributed to hardening of the layers. • Wear resistance of coatings was 5.8 times as high as that of low tempered steel. [ABSTRACT FROM AUTHOR]

In this study, NiCrSiB-SiC composite coatings were prepared on 16Mn low-carbon steel by vacuum cladding technology using SiC and NiCrSiB mixed powders as raw materials for enhancing their wear resistance. The effects of different content of SiC particles on the microstructure evolution, mechanical and abrasive wear properties of the coatings were investigated. The results showed that SiC particles in all the NiCrSiB-SiC composite coatings with different SiC contents were completely decomposed into C and Si under the catalysis of Ni-based alloy. The out-diffused Si into the coating mainly led to the formation of the Ni 3 Si eutectic phase, while the out-diffused C introduced M 7 C 3 , M 3 C 2 , M 2 (C, B) and other hard phases. Besides, C also diffused to the substrate, leading to a carburizing effect, which remarkably enhanced the mechanical properties of the substrate. In the NiCrSiB-SiC composite coatings with high SiC content, the decomposition of SiC led to the remaining graphite phase. However, once the concentration of SiC was over high, excess graphite would deteriorate the compactness and adhesion of the coating, weakening its wear performance. The nanoindentation and abrasive wear experiments revealed that the composite coating with 5 wt% SiC particles had lower elastic modulus (E), higher hardness (H), H / E , and H 3/ E 2, and its wear volume was only 1/10 of that of the substrate, indicating the best mechanical and wear properties. The excellent wear performance can be attributed to the combination of the in-situ formed carbides and borides hard reinforcing phases and the tough coating matrix composed of Fe and Si dissolved γ-Ni and Ni 3 Si eutectic phase. • NiCrSiB-SiC composite coatings with different SiC contents are prepared on 16Mn by vacuum cladding. • SiC particles are decomposed at 1293 K due to the catalysis of Ni-based alloy. • Decomposition product Si leads to formation of Ni 3 Si at low SiC content and Ni 31 Si 12 at high SiC content. • Decomposition product C leads to carbides M 7 C 3 , M 3 C 2 , M 2 (C, B) and a carburized layer at coating/substrate interface. • Coating with 5wt.% SiC has higher H , H / E , H 3/ E 2 and wear resistance than other coatings, the wear volume is 1/10 of 16Mn. [ABSTRACT FROM AUTHOR]

The current research focus is to design a robust micro/nano-structured superhydrophobic epoxy coating to improve the wetting and anti-corrosion behavior of Q355 mild steel in harsh environment and obtain desired properties of self-healing and self-cleaning. Modified attapulgite (APT) and cerium nitrate based high-performance corrosion inhibitor ODA/PDA/APT-Ce3+ (OPA Ce3+) coatings were synthesized by the addition of dopamine (DA) and octadecylamine (ODA) which resulted in excellent corrosion inhibition by enhancing the corrosion protection performance of metal alloy and improving the water contact angle of the synthesized epoxy based OPA Ce3+ coating to more than 160°. While wettability and corrosion protection were strongly associated with cerium nitrate and DA content, the surface microstructure of coated steel samples were relevant to attapulgite quantity. Moreover, the OPA Ce3+ surface coating demonstrated good self-healing properties to counter chemical deterioration in harsh environment after being exposed for several hours to 3.5 wt% sodium chloride, acidic and alkaline solution. It was able to regain its superhydrophobic properties following hot air flow over the coating surface. The OPA Ce3+ epoxy coatings displayed long-lasting and outstanding self-healing performance in terms of its wettability and electrochemical stability. • OPA-Ce3+ epoxy based superhydrophobic coatings has been synthesized. • Significantly increase wettability and anti-corrosion properties of the surface. • Coating displayed self-healing property after deterioration under chemical attack. [ABSTRACT FROM AUTHOR]

Due to the health hazard, emanating from chromium trioxide based coating processes, the longtime approved hard chromium platings have to be replaced by alternative coating systems in future. Therefore, the development of PVD coatings, which protect mild steel substrates from both, corrosive and tribological stresses, is a key demand for the PVD coating industry. These coatings have to achieve comparable properties for wear protection and corrosion resistance like chromium platings and also must fulfill the current sustainability criteria in terms of environment protection and health. Recently, the authors developed a TiMgGdN coating system with improved corrosion properties for steel substrates. The superior corrosion properties of TiMgGdN was initially discovered for surface protection of magnesium alloys, which is the most corrosive construction metal (Hoche et al., 2014). In the present work, the TiMgGdN coating concept was applied to mild steel substrates. The coating composition and the deposition parameters were varied to optimize the coatings for steel substrates. The coatings were deposited by using both, DC and HiPIMS sputtering. The influences of the chemical composition, the deposition parameters, the substrate roughness and the sputter mode on the corrosion properties were examined. The coatings were characterized concerning their microstructural, mechanical and chemical properties. Salt spray tests as well as electrochemical measurements were carried out to examine the corrosion properties of the coated specimens. Furthermore, the electrochemical properties as well as the open circuit potentials of the coating materials themselves were determined. [ABSTRACT FROM AUTHOR]

Duplex stainless steels (DSS) show good mechanical properties, wear, corrosion resistance and fatigue strength. In order to decrease operational costs in paper and pulp industry, DSS is employed through weld overlay coatings on mild or low carbon steel components. In this work, the aim was to evaluate the DSS weld overlay properties obtained through deposition of ER 2209 duplex stainless steel alloy on a mild steel plate (ASTM A 516 Gr 60). The deposition was performed through GMAW/CMT welding process. The coatings were deposited using four heat inputs: 0.53, 1.01, 1.27 and 1.74 kJ/mm. Moreover, microstructural characterization by optical microscopy showed that heat input influences ferrite/austenite phase balance. Secondary austenite that precipitates due to the welding process in DSSs are Widmanstätten austenite (WA), grain boundary austenite (GBA), partially transformed austenite (PTA) and intragranular austenite (IGA). The amount of secondary austenite increases with welding energy input. The secondary austenite improves abrasive wear resistance while corrosion resistance is the lowest when welding energy is 1.74 kJ/mm. • Duplex stainless steel weld overlay coatings were produced by GMAW/CMT process • Energy input allow the variation of the coatings microstructure • Hardness of the coatings were higher than the rolled S32205 duplex plate • it was obtained coatings with same or better corrosion resistance than the rolled duplex plate [ABSTRACT FROM AUTHOR]

To enhance corrosion resistance of zinc phosphate coatings on mild steel, boron nitride nanosheets (BNs) were introduced into zinc phosphating bath. The effects of BNs on the phase composition, surface morphology and corrosion resistance of phosphate coatings were investigated by varying the concentration of BNs (0.15–0.60 g/L) in the phosphating bath. Results show that the presence of BNs could effectively reduce the crystal sizes of phosphate crystals and thus make BN-incorporated phosphate coatings denser and finer than pure phosphate coatings. Moreover, BN-introduced phosphating bath yields heavier phosphate coatings (25.10 g·m−2). In the electrochemical corrosion measurements, BN-incorporated phosphate coatings display the corrosion current of 3.21 × 10−6 A/cm2, which is one order of magnitude lower than the ones without BNs. Moreover, the time against corrosion of copper sulfate dropping prolongs to 328 s for BN-incorporated samples, which is an increase of 182.75% compared with pure ones. Unlabelled Image • Boron nitride nanosheets (BNs) were incorporated into zinc phosphate bath. • The introduction of BNs results in denser and finer phosphate coatings. • Corrosion resistance of BN-incorporated phosphate coatings are enhanced. [ABSTRACT FROM AUTHOR]

Ti and its alloys exhibit combination of unique properties for biomedical applications, however their poor tribo-electrochemical behaviour is a major concern. Therefore, TiN coatings were deposited on cp-Ti (grade 4) by sputtering technique aiming the improvement of its tribocorrosion behaviour. The properties of the coated samples, using different TiN deposition times, were characterized by using grazing incidence X-ray diffraction, FIB-SEM, and nanoindentation. The corrosion behaviour was studied by electrochemical impedance spectroscopy and potentiodynamic polarization in 9 g/L NaCl solution at body temperature. Tribocorrosion tests were employed under open circuit potential by using a ball-on-plate tribometer with 1 N normal load, 3 mm total stroke length, 1 Hz frequency, and 1800 s sliding duration. The results suggested that the TiN coatings deposited during 80 min presented better corrosion and tribocorrosion behaviour as compared to the bare metal and TiN coatings deposited during 30 min. • Deposition time affected mechanical and structural properties of TiN films. • Increased Ti 2 N phase ratio improved the corrosion and tribocorrosion performance. • Increased coating thickness was favourable for tribocorrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, titanium‑chromium oxide (TCO) coatings were investigated aiming to produce a functional hard-corrosion resistance coating based on the well-known properties of the individual TiO 2 and Cr 2 O 3 oxides. The TCO coatings were deposited on low carbon steel and Si substrates using reactive magnetron sputtering from a crystalline TiCr target. Amorphous TCO coatings with increasing oxygen content up to 65 at.% were obtained by rising the oxygen flow rate during the reactive deposition. Coatings deposited using constant O 2 flow rate of 1.5 (6.2% of oxygen) were selected to evaluate the corrosion resistance, hardness and to determine the effect of annealing treatments. Electrochemical evaluation was done using impedance spectroscopy and potentiodynamic polarization in 3.5 wt% NaCl solutions showing a significant protection efficiency. The coatings were heat treated at different temperatures (200, 400, 500, 600 and 800 °C) for 2 h in air. The coatings were analyzed by X-ray photoelectron spectroscopy to obtain the composition, X-ray diffraction (XRD) and scanning electron microscopy for microstructural and morphological characterization, respectively. The XRD results show that the heat-treated coatings maintained the X-ray amorphous structure up to 500 °C. Above this temperature, the coatings crystallize forming large Cr 2 O 3 crystals segregated to the surface leaving an amorphous TiCr bottom layer. • Amorphous Ti-Cr-O coating reached 30 GPa hardness. • Annealing at and above 500 °C led to segregation into Cr 2 O 3 and TiO 2. • Amorphous Ti-Cr-O coatings were deposited on low carbon steel. • The corrosion of the steel was significantly reduced under simulated sea water. [ABSTRACT FROM AUTHOR]

TiN-TiB 2 composite coatings were fabricated on a low carbon steel by using argon arc cladding (AAC) with the mixture of titanium powder and boron nitride powder. The effect of the Ti + BN contents on the phase, microstructure, and properties of composite coatings was investigated by means of XRD, TEM, SEM, hardness tests, and wear tests. The experimental results show that the main phase TiN and TiB 2 were formed due to the reaction between titanium and boron nitride during the AAC process. The composite coatings had no holes, cracks, or other defects and metallurgical bond with the steel substrate. The morphologies of particle-shaped, needle-shaped and rod-like of in situ synthesis particles phases were found in the composite coatings. The microhardness of the composite coatings (1100-) increased with the increase of the Ti + BN contents due to the presence of reinforcement (TiN, TiB 2) and gradually increased. The friction coefficient and wear loss of the composite coatings is far lower than the 35CrMnSi steel substrate. Besides, argon arc coating using the mixed powders of 30 wt%(Ti + BN)-70 wt%Ni has better anti-wearing effects during the dry sliding wear. • The TiN+TiB 2 reinforced Ni-based composite coating was synthesized by argon arc cladding. • The composite coatings had a higher hardness and a lower friction coefficient than • 35CrMnSi steel • An excellent wear resistance has been achieved in the composite coatings. • Optimum content of (Ti + BN) in composite coating is 30 wt%. [ABSTRACT FROM AUTHOR]

A simple ultrasonic dip-coating process was utilized to fabricate sodium silicate thin films on aluminum alloy substrates, and their chemical and corrosion properties were investigated as a function of their concentration in the solution. The attenuated total reflectance Fourier transmission infrared spectroscopy (ATR-FTIR) and energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Na, Si, and O in the films. The polarization resistance (R p) of the as-received aluminum substrates was found to be 10 ± 2 kΩ·cm2 in 3.5 wt% NaCl solutions. In comparison, sodium silicate thin films prepared from 1 M solution exhibited a large R p of 593 ± 32 kΩ·cm2. The corrosion protection efficiency was calculated from the corrosion current, which was found to be 99.52%. This study shows that sodium silicate thin films can be used as a protective coating against corrosion to aluminum substrates under aqueous NaCl environments. Unlabelled Image • Ultrasonic dip coating process to get sodium silicate thin films on aluminum • Compositional analysis confirmed the presence of Na, Si, and O. • High polarization resistance of 593 ± 32 kΩ·cm2 was obtained. • Corrosion inhibition efficiency was found to be 99.52%. [ABSTRACT FROM AUTHOR]

The present study is the first report on the possibility of blast furnace (BF) pig iron-based corrosion resistant and very hard composite (glass + crystalline) coating on a mild steel. The BF metal is of very lean and cheap alloy chemistry and its coating on the mild steel has been found to show similar corrosion resistance as shown by the stainless steel (SS) coating on the mild steel. The BF coating has been made through high velocity oxygen fuel (HVOF) thermal spray process at different powder feed rates of 30, 40, 50 and 60 g/min. The microstructural characterization of coatings reveals good inter-splat bonding with low porosity in the range of 3 to 5%. The corrosion potential of the BF coatings is significantly negative than that of the mild steel substrate as well as the SS coating suggesting that the BF coatings could provide sacrificial protection to the mild steel substrate in addition to the comparable corrosion resistance as shown by the SS coating in freely aerated 3.5% NaCl solution. It has been found that the corrosion resistance of these BF coatings is significantly higher than the conventional galvanized coating, allowing them to be a promising and better sacrificial coatings than the galvanized one. The high corrosion resistance of the BF coatings could be attributed to its partially amorphous structure, presence of high C, Si and P, and relative portion of the insoluble α-FeOOH phase compared to the soluble γ-FeOOH phase in the rust, indicated protection parameter of the rust (α/γ*). • Composite coating on mild steel is made by HVOF process from blast furnace iron. • Structure of the coating consists of mixture of amorphous and crystalline phases. • The coating shows low porosity, very high hardness, good corrosion resistance. • The coating shows both sacrificial and barrier protection to mild steel. [ABSTRACT FROM AUTHOR]

Stellite alloys are of great interest in industries due to a unique combination of high temperature mechanical strength, outstanding wear and corrosion resistance. Different thermal spraying processes are used for deposition of Stellite alloys on industrial components. However, the investigations on the structure–property relationship of these alloys produced via different deposition process are limited. This study focuses on the microstructure, oxidation, and tribo-mechanical properties of Stellite 21 deposited by cold gas spraying (CGS) and high velocity oxy-fuel (HVOF) process on a low carbon steel substrate. The coating cross-section was characterized by SEM and optical microscopy. The coatings were further characterized by using nanoindentation, adhesion, and ball-on-disk wear tests. Moreover, XRD tests were run on the powder and the coatings to reveal possible phase transformation during spraying, as well as during wear and oxidation tests. The results showed no phase transformation in the as-sprayed CGS coating, besides higher values of porosity and oxide phase in the HVOF coating. However, an fcc-to-hcp phase transformation occurs at the surface layer of both types of coating during the ball-on-disk wear test. The presence of continuous oxide networks in HVOF coatings leads to delamination during the wear test. Overall, the CGS Stellite 21 coatings exhibit better performance than HVOF coatings in wear and oxidation tests. • The differences in the microstructure of CGS and HVOF sprayed Stellite 21 is studied. • Martensitic transformation occurs at the tribo-layer of coatings during wear test. • The continuous oxide networks in HVOF coatings leads to delamination of splats. • In CGS, the tribo-layer removal is hindered due to the absence of oxide networks. • Good adhesion of dense CoCr 2 O 4 layer prevents the surface oxidation proceed in CGS. [ABSTRACT FROM AUTHOR]

Due to its low density and high strength, magnesium has increasing potential in the lightweight area, especially as a material for structural components. To address the corrosion problem, which is the main issue with using Mg alloys in the automotive industry, as well as to address wear problems, a new technique that uses an asymmetric potential pulse waveform to form nanocrystalline PEO (plasma electrolytical oxidation) coatings on Mg substrates, especially on sheet Mg plates, is developed in this study. The results of the analysis of PEO coatings on different sheet Mg alloy plates, which are characterized by electrochemical analysis methods including electrochemical impedance spectroscopy and potentiodynamic polarization are presented in this study. Furthermore, the coatings are characterized regarding their morphology and wear resistance, while varying the coating thickness by different processing times. A further improvement of the applied waveform by an on-top modification of the pulse signal leads to higher corrosion resistance as well as to a better performance in the tribological testing. Unlabelled Image • Ultraceramic® process, characterized by an asymmetric waveform, provides high corrosion and wear protection on Mg alloys. • High-resistance low-porosity PEO coatings can be adapted to any Mg alloy. • Coatings with a thickness of around 10 and 25 μm lead to a high performance in term of corrosion and wear resistance. • Optimization by on-top modulation of waveform signal improves the PEO coating's corrosion resistance on new E-Form alloy. [ABSTRACT FROM AUTHOR]

Electroless nickel-phosphorous (NiP) coatings were produced on low carbon steel substrates for a total plating time of 3 h. Different preparation modalities were pursued. Multilayered coatings were produced by stacking three layers of the same composition by successive electroless plating with rinsing steps in between. On the other hand, coatings termed 'monolayered' for the sake of comparison were deposited by one step electroless process, with and without undergoing bath replenishment of the electrolyte during plating. All the samples were subjected to thermal annealing at 400 °C for 1 h under argon atmosphere. The results show that the multilayer approach prevents crack propagation in the as-deposited coatings because the interfaces between layers block the advance of defects. Bath replenishment during monolayered coatings production creates pseudo-interfaces similar to those of the multilayered case but they are ineffective in terms of corrosion protection. Un-replenishment of the electrolyte promotes a change in the coating's microstructure from lamellar to columnar which severely worsens their performance. Upon annealing, the presence of interfaces, along with the recrystallization of the metallic matrix, promotes an upgrading of the corrosion performance of the multi-layered coatings. The corrosion products spread laterally at the interface where they stockpile. At a certain point, the accumulation of these by-products provokes the exfoliation of the outermost layer exposing the layer underneath to the corrosive media, thereby delaying the advancement of the corrosion attack. The results of this study highlight the importance of the plating approach selection, as well as the need for proper electrolyte maintenance during the production of high-performance electroless coatings. Unlabelled Image • Monolayered and multilayered NiP electroless coatings were produced from a proprietary low phosphorous nickel electrolyte. • The multilayered coatings were characterized by well-defined interfaces due to process interruption. • Interfaces of multi-layered coatings block crack propagation and corrosion progress. • Multilayered coatings exhibit enhanced corrosion resistance in comparison to monolayered coatings. [ABSTRACT FROM AUTHOR]

This paper illustrates a composite design of thin hard AlNi 3 coating on soft stainless steel for making the improved impact resistance. The coating layer with a thickness of 0.21 ± 0.01 mm is plasma sprayed on the top and bottom surfaces of the machined AISI 304 stainless steel. It is composed of the brittle intermetallic compounds of AlNi 3 phase toughened by solid-solution elements of Cr, Fe and Si. It has a higher hardness (900 ± 90 HV 0.2) than that of the stainless steel substrate (250 HV 0.2). The machined and coated samples were subjected to impact loadings at different gas gun pressures operated by split Hopkinson pressure bar. For comparison, quasi-static compression tests were also conducted. Then, the mechanical data and plastic deformation under various rate loadings are achieved. The confinement effects of thin hard coating on dynamic plastic deformation of soft stainless steel are revealed. The inherent mechanisms are clarified. It is full of interest to develop a valid route of improving the impact-resistant performance of soft materials by composite design. • Thin hard coating layer is plasma sprayed on the surfaces of stainless steel. • 16% decrease in strain along the axial direction is achieved in the coated samples. • 100% increase in barreling ratio along the lateral direction is achieved in the coated samples. • The inherent mechanisms for the improvement in impact resistance are clarified. • A route of improving the impact resistance of soft materials by composite design is proposed. [ABSTRACT FROM AUTHOR]

Abstract Cold spraying of Stellite 21 powder on low carbon steel is performed to investigate the effect of traverse speed on the deposition efficiency (DE) of high-temperature alloys. Based on the simulation of particles' impact temperature and velocity, the initial experiments are performed at different gas pressures (32 and 40 bar), temperatures (800 and 730 °C), and stand-off distances (10, 25, and 40 mm) at a constant traverse speed of 20 mm·s−1. The experiments showed that high pressure, temperature, and short stand-off distance are preferred. The wipe test results indicated a potential of high DE at lower deposition flux over the substrate surface area at the first layer deposition. Thus, new tests are carried out at different traverse speeds ranging from 20 to 400 mm·s−1 to adjust the deposition flux over the surface area of the substrate. The effect of traverse speed on DE and coating characteristics such as porosity and microhardness is studied as well. The results showed that the lower DE at lower traverse speed is related to the erosion of bonded particles due to the subsequent particles' impact. By increasing the traverse speed from 20 to 300 mm·s−1, the DE increased more than twice. Induction time extension at higher traverse speed led to lower DE at 400 mm·s−1. Graphical abstract Unlabelled Image Highlights • Stellite 21 coating was successfully cold sprayed onto the steel substrate. • The high temperature of the gas was more favorable for Stellite 21 deposition. • Varying the traverse speed influences the DE, microhardness, porosity, and roughness. • Lower DE at low traverse speed was related to the erosion of bonded particle. [ABSTRACT FROM AUTHOR]

Abstract In this research, titanium carbide was fabricated onto carburized AISI 1020 steel through thermo-reactive diffusion (TRD) with salt bath processing at 900 °C for 3 h. The researchers investigated the microstructure and the wear resistance of the as-obtained coating. Results showed that the as-received coating was of 7.5 ± 0.3 μm with surface micro-hardness of approximately 1885 ± 121 HV 0.025. The coating presented excellent adhesion to the substrate as evidenced by a bonding force between the coating (carbide layer) and substrate of approximately 52 N. During the sliding test, its friction coefficient (0.45–0.56) tended to decrease in the final stage. In comparison with the bare substrate, the specific wear volume loss for the titanium carbide–coated specimen decreased by 78%. Highlights • TiC coating was achieved on carburized AISI 1020 by thermo-reactive diffusion at 900 °C for 3 h. • The adhesion of the interface was enhanced by a narrow inter-diffusion region of titanium (from TRD) and iron. • The specific wear volume loss for the titanium carbide–coated specimen is decreased by 78%. [ABSTRACT FROM AUTHOR]

Abstract The oxide films on Q235 low carbon steel as a cathode were quickly prepared by cathodic plasma electrolytic oxidation (CPEO) in 80 vol% glycerol electrolyte within 9 min. The morphology, composition and microhardness of oxide films were analyzed. The corrosion behaviors of bare steel and CPEO films were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The optical emission spectroscopy (OES) was collected and the electron temperature in plasma discharge envelope was calculated. It was found that the CPEO oxide films contained FeO phase, Fe 2 O 3 phase and some dispersed carbon particles. The plasma discharge envelope contained many active carbon, iron and oxygen species. The electron temperature in the plasma discharge region was over 5000 K and meanwhile the surface temperature of steel is over 1000 °C. The CPEO oxide film on Q235 steel grew linearly with 10.89 μm/min. The CPEO treated Q235 low carbon steel had a good corrosion resistance with lower corrosion current density and higher impedance. Highlights • The CPEO film on Q235 steel grows linearly and oxidation reaction rate reaches 10.89 μm/min. • Electron temperature in discharge region is over 5000 K and surface temperature of steel is over 1000 °C. • Active carbon, iron and oxygen species in plasma envelope enhance rapid growth of oxide film. • CPEO treatment improves corrosion resistance of carbon steel by decreasing corrosion current and increasing impedance. [ABSTRACT FROM AUTHOR]

Abstract Alloys used to fabricate water turbines for power generation are subjected to cavitation wear in an environment propitious to corrosion. Refurbishing by build-up welding of such gigantic infrastructures is time consuming and costly. Therefore, efforts are being deployed to develop coatings that would extend the time span between water turbine overhauls. In that sense, Fe 3 Al-TiC coatings are being studied in collaboration with the largest hydroelectricity producer in the World to determine if they could eventually be utilized as a coating material for their water turbines. Fe 3 Al-TiC coatings containing various volume fractions of reinforcing TiC particles were deposited on a mild steel substrate using the high-velocity oxy-fuel (HVOF) technique. The feedstock powders were produced by combustion synthesis. Fe 3 Al coatings, containing different volume fractions of sub-micrometer TiC particles (30 mol%, 50 mol%, and 70 mol%), were prepared. Dry-sliding wear resistance (pin-on-disk) of the coatings was characterized using a Al 2 O 3 counterface having a diameter of 6.33 mm. Al the sliding wear tests were conducted at room temperature with sliding speeds ranging from 0.04 m/s to 0.8 m/s. It was found that an increase in the TiC content from 30 mol% to 50 mol% increases wear resistance by 11% and 75% for sliding speeds of 0.1 m/s and 0.8 m/s, respectively. Moreover, further increase in TiC content to 70 mol% provided coatings with wear rates one order of magnitude lower than those measured for Fe 3 Al-50 mol% TiC coatings. It was also found that for Fe 3 Al-30 mol% TiC coatings, the wear rate increases with increasing sliding speed up to 0.3 m/s. Further augmentation of the sliding speed to 0.8 m/s resulted in an abrupt reduction of the wear rate. The maximum wear rate of each series of coatings shifted to lower speeds with increasing TiC content. For the Fe 3 Al-50 mol% TiC and Fe 3 Al-70 mol% TiC series, the principal wear mechanism changed from adhesive wear to abrasive wear with increasing sliding speed. For the Fe 3 Al-30 mol% TiC series, the main wear mechanisms was abrasive wear and its occurrence was independent of the sliding speed. Results showed that, when using feedstock powders produced by combustion synthesis, HVOF coatings exhibited about 1.5 to 20 times higher wear resistance compared to the feedstock with identical composition produced by high-energy ball milling. Highlights • Fe 3 Al reinforced with sub-micrometer particles TiC particle was produced by thermal explosion combustion synthesis. • Compared with coatings prepared with high-energy ball milling, the dry-sliding wear rate is reduced by 1.5 to 20 times. • The results form this research offer a promising avenue for the production of HVOF coatings resistant to dry-sliding wear. • This type of feedstock is cost-effective and yields improved resistance to dry-sliding wear. [ABSTRACT FROM AUTHOR]

Abstract Nickel-Phosphorus/Crab shell particle (NiP/CSP) composite coatings were prepared with different weight dispersions of CSP (0.5 g/l, 1.0 g/l, 1.5 g/l, 2.0 g/l, 2.5 g/l and 3.0 g/l) on mild steel using electroless coating process. Fabricated coatings were post treated with heat treatment and Nd:YAG laser treatment process and followed by a comparative study on surface morphology, surface hardness, phase structure, and friction-wear property with as-plated NiP and NiP/CSP composite coatings. The result showed the relative changes in the surface morphology of NiP/CSP composite coatings after Nd:YAG laser treatment. Dendrite structure was observed for laser treated coatings and its formation was affected by the incorporation of CSP in the NiP matrix. FeNi 2 P phase was formed for laser treated coatings in addition to the Ni 3 P and Ni 12 P 5 phases. Higher surface hardness of 966 Hv 0.05 and 941 Hv 0.05 was achieved for laser treated NiP and NiP/CSP composite coatings compared to the heat treatment process and as-plated condition. On comparison with various weight dispersions, higher surface hardness of 941 Hv 0.05 was obtained for NiP/CSP (2.5 g/l) composite coatings as a result of the high diffusion of Fe element from substrate to the surface. Low friction coefficient was seen for the heat treatment process followed by the as-plated and laser treatment process. The formation of FeNi 2 P phase caused an increase in the friction coefficient for laser treated NiP and NiP/CSP composite coatings. However, there was an improvement in the wear resistance of laser treated coatings compared to the as-plated and heat treated coatings. Highlights • NiP/CSP composite coatings prepared with various wt. dispersions of CSP. • Comparative study is made between as-plated, heat treated and laser treated coating. • Formation of dendrites was affected after CSP reinforcement. • Numerous pores across the cross section of laser treated coatings was reported. • FeNi 2 P phase have increased the friction coefficient with reduced wear rate. [ABSTRACT FROM AUTHOR]

MnCrCoFeNiCu high entropy alloy (HEA) coatings with varying volume fractions of carbon nanotube (CNT) were electrodeposited on mild steel. Morphology, phase constitution, wettability, surface oxide chemistry and corrosion of coatings were examined. Coating morphology became finer with initial CNT incorporation and then transformed to rougher surface for higher CNT volume fractions. Pristine HEA coating contained mixture of body centre cubic (bcc) and face centre cubic (fcc) phases. With the CNT addition phase homogenization happened and for the HEAC3 coating (from electrolyte with 5 mg/L concentration of CNT) single phase bcc microstructure was obtained. The phase mixture however re-evolved for the higher CNT incorporation due to CNT agglomeration and reduction in the metal-CNT interfaces. Water contact angle was 127° for HEA_C3 coating. All the HEA-CNT coatings exhibited higher corrosion resistance than the pristine HEA coating, corrosion rate trend was however not monotonic with CNT volume fraction and maximum corrosion resistance was observed for the HEA_C3 coating. Surface oxide chemistry of exposed sample showed stabler oxide over the HEA-CNT coatings when compared to the oxides of the pristine HEA coating. Higher corrosion resistance of the HEA_C3 coating was due to compact morphology, hydrophobicity, phase homogenization and evolution of stable surface oxides. • MnCrCoFeNiCu HEA-Carbon Nanotube (CNT) composite coatings were electrodeposited over mild steel. • Composite coatings showed higher corrosion resistance than pristine HEA coating. • Electrochemical property of composite coating was highly sensitive to the CNT volume fraction. • Optimum CNT volume fraction yielded highest corrosion resistance. • Optimum CNT volume fraction yielded relatively stable surface oxide phases. [ABSTRACT FROM AUTHOR]

This study investigated the microstructure and corrosion behavior of the cold-sprayed Zn11Al3Mg zinc alloy coating through analysis of phase composition, microstructures, and electrochemical behaviors. The results demonstrate that the CS-Zn11Al3Mg coating primarily consists of a finely structured ternary eutectic phase of Zn/Mg 2 Zn 11 /Al, with uniformly distributed submicron-sized Al phases. Additionally, a small amount of coarse Zn/Mg 2 Zn 11 eutectic phase coexisted with MgZn 2 was also observed. The enhanced corrosion resistance of the coating was obtained when compared with cold sprayed Zn coating. The rapid sacrificial dissolution of Mg Zn intermetallic compounds was observed in saline solution, leading to localized corrosion in the coating layer. Fortunately, the cooperative interaction of dissolved Mg2+ and Al3+ promotes the formation of protective corrosion products, namely Zn 5 (OH) 8 Cl 2 ·H 2 O and Zn/Mg-Al layered double hydroxides, provided long-term corrosion protection for mild steel. • Zn11Al3Mg alloy coating was deposited on mild steel by cold spray technique. • The coating predominantly consists of a finely structured ternary eutectic. • Enhanced corrosion resistance was obtained when compared to Zn coating. • Formation of protective corrosion products (LDHs and Zn 5 (OH) 8 Cl 2 ·H 2 O) was promoted. [ABSTRACT FROM AUTHOR]

Textures and residual stresses are generated during electrodeposition of chromium coatings, which directly affect the performance of the coating. In this work, the variations of texture, hydrogen content, residual stress, microhardness and corrosion resistance of chromium deposited from hexavalent [Cr(VI)] chromium bath using direct current deposited technique were investigated. Electrodeposition experiments were carried out on the low carbon steel substrate by varying the key variable current density. The macrotexture of the coatings was studied by XRD. The crystal orientation and dislocation density were analyzed by EBSD. Residual stress was measured by the indentation method. The research demonstrated that a single preferred orientation on the (222) plane was found at current densities of 20 A/dm2, 35 A/dm2 and 50 A/dm2. At 40 A/dm2, a mixed preferred orientation on the (222) + (211) planes was discovered. Furthermore, the formation of the chromium coating texture was affected by the variation of hydrogen content, for higher hydrogen promoting grain growth along the (222) crystal plane. Notably, the microstructure-property relationship was developed. At the single preferred orientation of (222) plane, the corrosion resistance was more favorable. At the mixed preferred orientation of (222) + (211) planes, the coating surface achieved higher microhardness, but formed higher residual stress and more microcracks. Moreover, the better electroplating parameter was proposed. At 35 A/dm2, the coating had the fewer microcracks and the better overall performance. The higher microhardness of 753 HV was found. The more favorable corrosion resistance was discovered, with the breakdown potential and passive current density of 804.7 mV and 2.220 × 10−6 A/dm2. The lower residual stress of 61 MPa was found, which was about 81 % lower than the maximum stress. It was significant in industry for the enhancement of the service life of substrate and the optimization of the chromium coating process. • A single preferred orientation was found at 20 A/dm2, 35 A/dm2 and 50 A/dm2. • At 40 A/dm2, a mixed preferred orientation was discovered. • The formation of the texture was affected by hydrogen content. • High hydrogen facilitated grain growth along the (222) plane. • At 35 A/dm2, the better overall performance was found in the coatings. [ABSTRACT FROM AUTHOR]

Cu-Sn-Zn coatings have been widely used in industry for their unique properties, such as good conductivity, high corrosion resistance and excellent solderability. To further improve the mechanical performance of Cu-Sn-Zn coatings, powder-enhanced method was applied and Cu-Sn-Zn-TiO 2 nano-composite coatings with different TiO 2 concentration were fabricated. The microstructure of Cu-Sn-Zn-TiO 2 nano-composite coatings were investigated by X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The mechanical properties of coatings including microhardness and wear resistance were studied. The results indicate that the incorporation of TiO 2 nanoparticle can significantly influence the properties of Cu-Sn-Zn coatings. The microhardness of Cu-Sn-Zn coating was increased to 383 HV from 330 HV with 1 g/L TiO 2 addition. Also, the corrosion resistance of coating was enhanced. The effects of TiO 2 nanoparticle concentration on the microstructure, mechanical properties and corrosion resistance of Cu-Sn-Zn-TiO 2 nano-composite coatings were discussed. [ABSTRACT FROM AUTHOR]

The failure mechanism of hot-dip aluminized (HDA) low carbon steel with nickel interlayer under static loading was studied. The nickel interlayer was plated using electric method with a current density of 1.8 A/cm 2 for 10 min in Watts bath, followed by hot-dipped in molten pure aluminum (>99.5%) for 10 s at 700 °C. The specimens were smoothly deposited with 2 mg/cm 2 of NaCl/Na 2 SO 4 salt mixture, with a portion of 50/50 wt% ratio. The tensile test in hot corrosion, induced by salt mixture, was carried out by applying a static load at 750 °C. The results show that the intermetallic layer of Ni/Al exhibits high adhesion and formability while the elongation of gauge length rising to 7%. Owing to the inter-diffusion between Ni/Al, the intermetallic layer gradually changes to laminar structure with higher nickel content which also contributes to enhance the performance. However, hot corrosion induced by salt mixture reduces the amount of aluminum on the outer layer lowering the thickness of Ni/Al intermetallic layer. As the perpendicular cracks formed, the salt mixture penetrates to the interface between substrate and coating layer causing the oxidation of the carbide and accelerating the phenomenon of break away. Overall, the HDA with nickel interlayer on low carbon steel improved the lifetime to about 5 times compared to bare material. [ABSTRACT FROM AUTHOR]

A superhydrophobic TiO 2 coating was prepared on mild steel to protect/increase life span of the steel by a simple one step electrophoretic deposition (EPD) technique followed by post-deposition treatment with methylhydrogen polysiloxane (trade name KF-99) and heat treatment. Superhydrophobicity was developed at some critical concentration (20 wt% solution) of KF-99. The water contact angle of bare steel, TiO 2 coated phosphated steel substrate (PSS) and TiO 2 coated PSS post treated with KF-99 (20 wt% solution) were 11°, 41.7° and 160.7°, respectively. The corrosion resistance of the superhydrophobic coating was estimated by Tafel polarization measurement. The potentiodynamic curves clearly demonstrated that the corrosion rate of superhydrophobic coating was an order of magnitude lower than bare mild steel in 3.5 wt% NaCl solution. The E corr and I corr values for the superhydrophobic TiO 2 PSS coating post treated with KF-99 were − 380 mV and 0.09 μA respectively, compared to − 930 mV and 120.22 μA for bare steel and − 820 mV and 20.41 μA for TiO 2 coated (PSS) untreated with KF-99. It clearly shows significant improvement in corrosion resistance properties of the superhydrophobic TiO 2 coated PSS. The coating also exhibited very strong adhesion to the surface with a nano-indentation hardness value of 0.5 GPa. The superhydrophobic coating with excellent corrosion resistance thus developed is a promising candidate for wide range of industrial applications. [ABSTRACT FROM AUTHOR]

In the present study, ferrosilicon-aluminium coating was successfully deposited on the surface of low‑carbon steel using mechanical alloying (MA) technique. The coating structures after MA and annealing were studied using X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy disperse X-ray spectroscopy (EDX) and electron backscatter diffraction (EBSD). The roughness and hardness of the coatings were measured by Surfcorder SE300 and microhardness tester, respectively. The coating thickness after mechanical alloying is in the range of 65 μm to 100 μm and the surface roughness is around 11.581 μm. Phase analysis showed that ferrosilicon-aluminium coating was composed by FeSi 2 , Si and Al 0.8 Si 0.2 phases. While the thermal annealing led to the formation of FeAl 3 Si 2 and Fe 2 Al 3 Si 3 phases. Further cross-sectional observation of annealed samples showed that the coating consisted of four layers structures with the thickness of each layer depended on annealing temperature. The first top layer was composed of porous structure of FeAl 3 Si 2 and Fe 2 Al 3 Si 3 phases. The second and third layers possess a dense structure consisting of Fe 3 Al 2 Si 3 and Fe 2 Al 5 phases, respectively. The fourth layer at the coating/substrate interface was rich in Si, namely Si-rich layer. As annealing temperature increased, the thickness of Fe 3 Al 2 Si 3 and Si-rich layer increased, but the thickness of Fe 2 Al 5 layer decreased. The optimum microhardness value of ferrosilicon-aluminium coating after mechanical alloying and diffusion layer of annealed samples were 481 HV and 1170 HV, respectively. [ABSTRACT FROM AUTHOR]

Low-carbon, low-alloy δ-TRIP steel is a research topic of interest because it meets the lightweight requirements of automotive steel. To bolster its use as automotive steel, the present study focused on the galvanizing process of δ-TRIP steel. Samples were submitted to simulated annealing prior to hot-dip galvanization. The surface morphology of five groups of samples marked with different dew points were detected using scanning electron microscopy (SEM). The element distribution in the oxide layers of four groups of samples were detected using glow discharge optical emission spectroscopy (GDOES), and oxide layer structures of two representative groups of samples were analyzed using transmission electron microscopy (TEM) techniques. The results showed that the dew point affected the oxide layer structure of δ-TRIP steel. Increasing the dew point led to an extraordinary oxide layer of pure overflowing Fe platelets in the δ-TRIP steel. The present study is expected to prompt further developments in galvanized δ-TRIP steels. [ABSTRACT FROM AUTHOR]

WC-Co coatings have been extensively used in the applications requiring high abrasion and erosion resistance. However, they are not known to have significant corrosion resistance. In this regard, WC-(W,Cr) 2 C-Ni is a possible candidate material to replace WC-Co for applications requiring a combination of superior tribological and corrosion performance. In the present study, WC-(W,Cr) 2 C-Ni coatings are deposited on mild steel (MS) substrates using Detonation Spray Coating (DSC) technique and compared with the properties of WC-12Co coatings. The microstructure and phases present in the feedstock as well as coatings are analyzed. The major part of matrix phase is (W,Cr) 2 C phase in WC-(W,Cr) 2 C-Ni feedstock and coatings with traces of Ni-Cr phases. High speed nanoindentation testing was used to map the hardness of the feedstock and coatings. The average hardness value of (W,Cr) 2 C phase is found to be around 15 GPa with a range from 12 to 20 GPa. Three body abrasive wear and corrosion properties of the coatings were evaluated and correlated with the corresponding microstructure and mechanical properties. While the wear resistance of WC-(W,Cr) 2 C-Ni coating is marginally better than WC-12Co coatings with the presence of (W,Cr) 2 C hard phase as a matrix phase and the presence of Ni and Cr and its associated phases in WC-(W,Cr) 2 C-Ni coatings are responsible for exhibiting nobler corrosion potential and significantly reduced corrosion current densities therefore confers superior corrosion resistance compared to WC-12Co coatings. [ABSTRACT FROM AUTHOR]