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Austenitic-ferritic steel, as suggested by its name, has an equal fraction of austenite and ferrite phases, also known as duplex stainless steels (DSS), are one of the highly used materials for subsea pipelines applications. The presence of slurries is inevitable in subsea pipelines. This technical work elucidates the slurry erosive wear behavior of duplex stainless steel and the impact of the addition of niobium (Nb) on the phenomena. Vacuum induction melting was used to produce duplex stainless steel, and its Nb added casts. The aim of the work is to compare both castings' for erosive wear behavior using a slurry jet erosion tester. Computational thermodynamic software Thermo-calc was used to investigate the presence of numerous phases in the system. X-ray diffraction (XRD) has confirmed the formation of niobium carbide in the steel, indicated by Thermo-calc. The effect of slurry velocity (30, 40, and 50 m/s) and impingement angle of slurry (30°, 45°, and 90°) on wear characteristics of these castings were analyzed using volume loss measurements, optical profilometry, and scanning electron microscopy (SEM). The erosion rate of both the materials increased with increasing velocity, whereas erosion was more at shallow angles of impact and increased significantly at the slurry jet's normal incidence. Refinement of austenitic grains in the ferritic pool hints at an increase in heterogeneous nucleation in Nb-doped samples; at the same time, the samples have shown increased hardness and superior erosion resistance against the slurry jet impact.

The aim of this paper is to investigate the mechanical properties of Nickel Aluminium Bronze (NAB) alloying with Niobium (Nb) and Yttrium (Y) rare earth metals. NAB alloy frequently used in the aqueous solution as well as less widely used deployed materials were studied. To avoid failures due to aqueous environment. Niobium (Nb) and Yttrium as chosen alloying addition with NAB. The Nb and Y rare earth element which acts as stabilizing element to existing NAB system to optimize the mechanical properties. The NAB with alloying elements processed in the vacuum induction furnace by means of predetermined parameters. After casting, the samples were tested for the mechanical properties like tensile and Brinell hardness to ensure improvements with the master NAB system. At the same time, the characterization techniques SEM and EDAX with mapping analysis confirmed the chemical proportions of the elements in the developed NAB with proposed NAB (Nb) and NAB (Y) alloys. A comparative study is to be made for the NAB with Nb and Y under aqueous environment based for the developed alloys.

An investigation was carried in Nickel Aluminium Bronze (NAB) alloyed with Niobium (Nb) and Yttrium (Y) to study the effect of the microstructure for onshore applications. Nickel Aluminium Bronze is broadly used in aqueous atmospheres due to their good mechanical and corrosion resistance properties. The presence of destructive species in aqueous water initiates the corrosion of the engineering modules is inevitable. In-order to optimize the corrosion resistance Nb and Y were added as (1%, 2% & 3%) respectively in the master NAB. The specimens were exposed to the immersion test in NaCl solution. To create the behavior of corrosion and succeeding erosion, altered immersions hours were selected as 8, 16, 24, 32, 40, 48 and 54 h. The mass loss measurements were obtained after the completion of the individual specified time to calculate corrosion rates (CR). Solid particle erosion (SPE) investigations were also carried out on the developed alloys. The size of the particle which is used in the investigation is 50 µm. Corrosion rate was calculated and it is correlated with the immersion time. Scanning electron microscopy (SEM) investigations were observed for the corroded and eroded specimens.

Duplex stainless steels (DSS) exhibit excellent corrosion resistance and mechanical properties to the severe environments and hence are used in many engineering applications such as oil and marine industries, chemical storage, nuclear power plants, and many more. These are used as valves, fittings, and pipes to suck the crude oil in oil fields. Austenite (γ) and ferrite (δ) phases constitute the microstructure of DSS. However, one needs to control both the phases towards making it lucrative in desired applications. Investigations on tribological behavior of cast DSS are limited. The current work focuses on optimizing the wear parameters for slurry jet erosion and analyzing their effect on wear of the 5A DSS. Grey relation analysis (GRA) and Taguchi design of experiments have been used for optimization. Slurry jet erosion tester was used investigate the response of the material to various designed experiments. Worn-out surfaces morphologies and wear mechanisms were revealed using Scanning electron microscopy (SEM), whereas white light interferometer was used to understand 3D morphologies the surfaces.

AlCoCrNi alloy was modified by adding Mo to increase its corrosion resistance. Mo was successfully added to the alloy using mechanical milling. All the five constituents of the alloy were milled in a high-energy planetary ball-mill for 20 h. The effective concentration of Mo in the alloy was 10%. At equal intervals, samples were taken for phase formation studies using X-ray diffractional analysis (XRD). The micro-structural characterization was carried out to confirm the homogeneity of the alloy using Field emission scanning electron microscopy (FESEM). The resultant high entropy alloy (HEA) powder was thermally sprayed over a 316l substrate using High-velocity Oxy-fuel (HVOF) technique. Corrosion characteristics of the coating were studied using potentio-dynamic polarization (PDP) test under standard condition. The corrosion properties of the coating were compared with conventional NiCrSiB corrosion resistant coating. The AlCoCrMoNi HEA system offers better resistance to corrosion than NiCrSiB coating.

Nanocrystalline powders of 4 mol.% GdO1.5-4 mol.% SmO1.5 doped ZrO2 (4Gd4SmSZ) has been synthesized by co-precipitation process. Their phase transformation and crystalline growth behavior was investigated by Thermo gravimetric-Differential Thermal Analysis (TG-DTA), X-ray Diffraction (XRD), Raman spectroscopy and High-Resolution Transmission Electron Microscopy (HR-TEM) after calcinations at different temperatures. The XRD, Raman spectra and HRTEM results confirm the nature of tetragonal zirconia (t-ZrO2). The prepared 4Gd4SmSZ powders, remains in the single metastable tetragonal phase over the whole calcination temperature ranging from 873 K to 1273 K for 2 h. The crystallite size varies from 11.98 nm to 18.90 nm with increase of temperature from 873 K to 1273 K. The activation energy of the prepared powders at low temperature is considerably lesser than that at a higher temperature. The annealed 4Gd4SmSZ powders had shown excellent phase stability at 1573 K for 100 h. Keywords: Zirconia, Coprecipitation, Rare earth oxide, Phase transformation, Tetragonal, Activation energy

The effect of cerium addition on AZ91 magnesium alloy and its influence on stress corrosion cracking (SCC) were studied using constant load proof ring testing NaCl-K2CrO4 and ASTM D1384 solutions at 70 and 80% of yield stress, respectively. The investigation revealed that the optimum grain refinement of desired phases occurred with 0.5% addition of cerium. The addition levels of cerium above 1.5 wt.% to AZ91 alloy resulted in premature failures due to poor SCC resistance in both solutions (K2CrO4 and ASTM D1384 solutions). The microstructural studies of the experimental alloys were characterized by using optical and scanning electron microscopy. The elemental compositions of cerium-added AZ91 magnesium alloys were studied by energy-dispersive spectroscopy. The results indicate that the mode of SCC failure was found to be transgranular in nature along with secondary cracks containing cleavages which resulted from the hydrogen embrittlement and anodic dissolution phenomena. The AZ91 alloy with 0.5 wt.% cerium exhibits better mechanical properties and high stress corrosion resistance.

Nickel-based superalloys are used widely in the critical areas of applications such as aerospace, marine, power and many process industries. In this study, solid particle erosion behavior of cast nickel-based CY5SnBiM was analyzed at room temperature. The velocity and angle of the study were set to 59 m/s, 92 m/s and 124.137 m/s, and 30°, 45°, 60° and 90°, respectively; this resembles the exact industrial valve applications. Macrographs were taken to identify the wear scar of material at different angles and different velocities. X-ray diffraction (XRD) was carried out on the material to observe the nature of precipitates. Scanning electron microscopy (SEM) was carried out to identify the plowing action on the material by the erodent in the case of lower angle due to ductile nature of the material. In the case of higher angle, it develops deep pits and craters due to rebounding of erodent particles.

Aluminium composite with VAL12 as matrix and La2O3 as dispersoids fabricated through liquid metallurgy route involving liquid forging operation through squeeze casting process in the present investigation. The frictional characteristics of as-cast aluminium composites are studied under dry sliding wear tests by varying the service factors. The samples prepared were examined for its uniform distribution of the reinforcement, phases formed using advanced characterization facilities. Taguchi orthogonal array method is employed in designing the experiments, and the responses are recorded in terms of wear rate and frictional coefficient. The mechanistic studies are carried out by analyzing the wear surface morphology using SEM. Predominantly AMMC shows delamination and abrasion at higher loads due to thermal softening and adhesive mechanisms at lower loads. Load and sliding distance majorly characterize the wear behavior of the AMMCs under un-lubricated sliding conditions.

Duplex stainless steel (DSS) is having an equal fraction of ferrite and austenite. Chromium, Nickel, Molybdenum, and few minor alloying elements constitute a DSS system, which makes metallurgy of the system complex. Proper heat treatment is need of the hour when it comes to expecting desired properties from the material, subjected to a specific working environment. DSS is one of the favourite choices for oil and gas industries. This study focuses on optimizing the heat treatment parameters and heat treating the as-cast 5A DSS and investigating microstructural evolution of the material subjected to various quenchants such as brine, water, and polyethylene glycol. Heat treatment temperatures, quenching media, and the quenching time have been selected in accordance with ASTM standards. Thermocalc TCFE8 database is being used for understanding the material response to various heat treating temperatures.

Niobium addition to base alloy significantly reduces the formation of deleterious phases, in particular, sigma phase when the material is sensitized at 900 °C. In this paper, hyper-duplex stainless steel with 0.47% of Niobium (Nb + CD3MWN - 7A) was casted using induction melting furnace and then heat-treated under two different heat treatment temperatures of 1160 °C and 900 °C to explore the properties such as microstructure and hardness for further study. The erosion test was carried out in air-jet erosion tester at room temperature with different erodent velocities. The study was done with a constant impact angle of 45°. Microstructure analysis was carried on two different heat-treated samples as well as on eroded samples using scanning electron microscope coupled with energy-dispersive analysis spectroscopy to confirm the presence Niobium carbide precipitation in sensitized sample at grain boundaries. Erosion test results showed that erosion rate is lower in sensitized sample when compared to solutionized sample because of their higher hardness in sensitized sample.

In this work multi-component equiatomic and non-equiatomic AlCoCrCuFeTix hexanary high-entropy alloys (HEA) was synthesised through mechanical alloying. The prepared powder was sintered via spark p...

Nanocrystalline samaria (8 mol%) doped zirconium oxide (8SmSZ) was synthesized using reverse co-precipitation technique, the calcination temperature ranging from 873 K to 1273 K for 2 h. XRD structural analysis results confirm the tetragonal(t) nature of the synthesized 8SmSZ nanocrystalline powder. The calculated crystallite size of tetragonal zirconia calcined at 873 K is around 9.0±0.5 nm and with increase in calcination temperature the size increases to 16.0±0.8 nm (1273 K). Thermogravimetric-Differential thermal analysis (TG-DTA) was carried out to study the crystallisation kinetics and growth behaviour of the 8SmSZ. The activation energy for the crystallisation of tetragonal ZrO2 formation in the 8SmSZ powder was found to be 308.1 kJ/mol by a non-isothermal DTA method. The growth morphology parameter was found to be n=2 indicating two-dimensional growth. The phase stability of the samples after annealing at 1573 K for 100 h was investigated by Raman spectroscopy and it was found that samaria doped zirconia exhibits better phase stability. These preliminary results confirmed the higher phase stability at elevated temperature thereby confirming its suitability in thermal barrier coating (TBC) applications.

Nanocrystalline powders of ZrO2–8mol%SmO1.5 (8SmSZ), ZrO2–8mol%GdO1.5 (8GdSZ), and ZrO2–8mol%YO1.5 (8YSZ) were prepared by a simple reverse-coprecipitation technique. Differential thermal analysis/thermogravimetry (DTA/TG), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM) were used to study the phase transformation and crystal growth behavior. The DTA results showed that the ZrO2 freeze-dried precipitates crystallized at 529, 465, and 467°C in the case of 8SmSZ, 8GdSZ, and 8YSZ, respectively. The XRD and Raman results confirmed the presence of tetragonal ZrO2 when the dried precipitates were calcined in the temperature range from 600 to 1000°C for 2 h. The crystallite size increased with increasing calcination temperature. The activation energies were calculated as 12.39, 12.45, and 16.59 kJ/mol for 8SmSZ, 8GdSZ, and 8YSZ respectively.

Equi-atomic and non equi-atomic multi-component systems were synthesized through different routes to form high-entropy single solid solution. One such high-entropy alloy (HEA) with hexanary composition AlCoCrCuFeZn x was synthesized using mechanical alloying. The effect of zinc variation on the crystal structure and phase formation was characterized using XRD, FESEM with EDS and TEM. The synthesis resulted in both equi-atomic and non equi-atomic nano crystalline AlCoCrCuFeZn with a crystallite size less than 10 nm.