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A technique of surface modification used to produce thick coatings with enhanced surface characteristics by developing highly resistive layers on the substrate is known as cladding. It plays a great role to increase the service life of industrial elements. It is broadly applied in chemical, mining, nuclear, power generation, and marine industries. There were a lot of studies done targeting Gas Tungsten Arc Cladding because of its advantages such as user-friendly, low cost, high deposition rate, low dilution, high reliability, etc. The four key features added to the substrate after claddings are dilution of a substrate, microstructure, microhardness, and tribological properties. Considering these features, the current article presents an overview of the Gas Tungsten Arc Cladding technique. The key goal is to reflect on the investigations conducted in the previous decade based on the wear, oxidation, and corrosion performance of cladding surfaces and their key observations. In addition, the effects of Gas Tungsten Arc Cladding process parameters, the substrate-clad materials combination, microstructural improvements, common advantages, and limitations associated with the technique are also presented. New research and industrial people on weld cladding would benefit from the outcomes of this article.

A great deal of investigation on gas tungsten arc cladding (GTAC) is focused on the study of enhancements in the microstructure, mechanical and tribological features of the cladding. The selection of right process parameters is a critical issue for the researchers. Decision makers in the industries must analyze a wide variety of parameters based on a set of contradictory criteria. Several multi-criteria decision-making (MCDM) techniques are now available to add values in selection of these parameters. The application of the TOPSIS and MOORA techniques to identify the best configuration of processing parameters in the gas tungsten arc cladding (GTAC) process is investigated in this work. The best processing parameters set for the multiple performance attributes should be welding current: 70 amp, speed: 240, argon flow: 13 and standoff distance 3.5 (TOPSIS-PCA) and welding current: 50, speed: 300, argon flow: 13 and standoff distance 3.5 (MOORA-PCA).A comparison of MOORA-PCA and TOPSIS-PCA demonstrates the superiority of TOPSIS over MOORA technique. The prediction accuracy of the TOPSIS-PCA hybrid approach model is found better than MOORA-PCA technique.

In this paper, the effect of rare earth oxide additive on coating material deposited by laser cladding process on various engineering materials has been discussed. The purpose of rare earth oxide additive in the coating composition is to improve the various properties like mechanical, tribological, and chemical properties. The main rare earth oxides are La2O3, CeO2 and Y2O3, which are generally used in laser cladded coatings. The limited amount of addition of these rare earth oxide compound may leads to improvement in hardness, wear and corrosion resistance of coating. The attractive properties of rare earth oxide is grain refinement, conversion of coarse structure to fine dendritic structure, creating grain boundary movement hindrance of dislocation in the material which leads to its application as nutrients in the coating material. The main purpose of coating is to enhance the surface properties of material like hardness, corrosion resistance and wear resistance. When rare earth oxide are added to the coating then it creates extra enhancement in the above properties. The laser cladding is widely used in modern manufacturing technology due to its very attractive properties like good metallurgical bonding with substrate, less dilution, minimum distortion, less heat affected zone and fast solidification and high cooling rate. In this review article the coating developed by laser cladding on various conventional engineering materials like ferrous materials, magnesium alloys, titanium alloys, aluminium alloys and nickel based super alloys with rare earth oxide addition are described.

This present research paper discusses about the fabrication of metal matrix composite coating on AZ31B magnesium alloy substrate with Al, Co and TiN mixed precursor powders by gas tungsten arc (GTA) cladding process. Firstly, Co and TiN powders were mixed properly in the ratio of 1:1. Thereafter, three samples with different compositions of 20 wt% (Co + TiN)), 25 wt% (Co + TiN)), 30 wt% (Co + TiN)) and balance aluminium powder were developed by preplaced technique. The samples were heated by TIG torch at the optimized parameter as current of 110 Amp, voltage of 25 V, welding speed of 4.23 mm/s and thermal energy of 3.12 kJ/cm. After melting and solidification metallurgical bonding between coating and substrate occurs. The microstructure and chemical composition of the coated samples were analysed by field emission scanning electron microscope (FESEM) and energy dispersive spectroscopy (EDS) respectively. The micro hardness of coated samples were analysed by Vickers micro hardness testing. It was found that with increase in percentage content of Co + TiN the amount of microhardness increases. Furthermore, it was found that the value of maximum microhardness was 422 HV0.1, which was nearly seven times higher than that of the magnesium alloy substrate (64 HV0.1).

This paper discusses about the recent advancements in laser cladding and alloying processes used for surface property enhancement of magnesium and its alloys. Laser cladding and alloying is advanced manufacturing method used for surface modification of metallic materials in the modern industries. The cladding process is surface modification technique, which is used for deposition of thick layer of advanced materials on surface of conventional materials to improve the surface properties like, wear resistance, hardness, oxidation resistance, corrosion resistance, biocompatibility and heat resistance. The advanced materials generally used for cladding operations are transition metals, alloys, ceramics, composites, nanomaterials, rare earth oxide and some solid lubricant additives. The conventional substrate materials are steel, cast iron, titanium alloy, aluminium alloy, magnesium alloys and copper alloys. Laser cladding is most widely used coating technique because of its attractive properties such as low dilution rate, good metallurgical bonding between coating and substrate, less distortion, narrow heat affected zone, high solidification and cooling rate. In this article magnesium alloy is considered as substrate material and the various coating materials used for its surface modification are explained. Also, the effects of various laser process parameters on phase composition, microstructure, elemental composition, mechanical properties, tribological properties and corrosion resistance are discussed. The characterization techniques such as XRD, SEM, EDS, Vickers microhardness test, wear and friction test, corrosion test used for coating analysis are described. Furthermore, the problem arises in laser cladding and alloying on magnesium alloy and their possible remedies are discussed.

This present review article discusses about the effect of solid lubricant additive in surface composite coating deposited by laser cladding and alloying process. Wear and friction is challenging problem in moving machinery parts subjected to rubbing action or sliding motion. Therefore to reduce the wear and friction of sliding machinery parts, coated layer is deposited on the surface of machine component to prevent from surface damage due to wear. Laser cladding and alloying is advanced manufacturing technology by which hard and wear resistant coating material is deposited on the surface of soft conventional materials by use of high power laser energy as heat source to provide good metallurgical adherence between coating and substrate materials. The coating materials generally used for enhancing the friction and wear resistance properties of conventional materials are advanced ceramics, advanced composites, nanomaterials and advanced alloys like high entropy alloys. When solid lubricants are added to these coating materials in limited amount then the friction and wear properties of developed surface improves. The solid lubricant additive in coating materials can reduce the friction coefficient and wear rate of materials. The solid lubricant materials acts as anti-friction and anti-wear agent in the coating materials. The most commonly used solid lubricants are h-BN, CaF2, MoS2, WS2, BaF2 and graphite. In this article the effect of these solid lubricant material on wear resistance and friction coefficient of coated surfaces produced by laser alloying and cladding techniques are described. The various engineering materials used for manufacturing of moving or sliding parts are ferrous materials, titanium alloys, aluminium alloys, magnesium alloys and copper alloys. In this article the coating deposited on these materials with solid lubricant additives by laser cladding and alloying process are reviewed. The problem arises during developing solid lubricant additive coating and its remedies are described.

This review paper discusses about the deposition of coating with high entropy alloy on metallic materials by laser energy based surfacing process. The purpose of coating is to deposit a hard and wear resistant layer of expansive material on the surface of workpiece material without altering the bulk properties of the workpiece to increase its surface properties. The coating with high entropy alloy shows excellent surface characteristics like corrosion resistance, wear resistance and oxidation resistance at high temperature. Due to high power density and fast cooling rate, laser cladding is most suitable technique for synthesis of coating with high entropy alloy. Coating with high entropy alloy is generally developed on titanium alloy, magnesium alloy, aluminium alloy, copper alloy and ferrous alloy by laser based cladding process. In this paper effects of laser process parameters on high entropy alloy coating developed on various industrial materials has been discussed. The various laser parameters which affect the properties of coating with high entropy alloy are laser power density, laser scanning speed, feed rate of powder, argon flow rate, and frequency. The high entropy alloy exhibits effect due to high entropy, effect due to slow diffusion, cocktail effect and effect due to severe lattice distortion, which leads to tailoring of microstructure and exhibits to excellent surface hardness, corrosion resistance and wear resistance. This paper describes about the brief review on benefits of high entropy alloy coating, challenges arises, suggested remedies for future research work and its applications in aerospace, automobile, marine and chemical industries.

In the present research work Ni + TiB2 metal matrix composite coating was deposited on AA6061 aluminium alloy substrate using nickel and titanium diboride as precursor by gas tungsten arc cladding process. The TIG torch was used as heat source to melt the preplaced powder mixture. The mixture of TiB2 and Ni powders were taken as 10 wt% and 90 wt% respectively. The three level of currents were used as variable parameters to melt the pre-placed powder layer viz. 120Amp, 140Amp and 150Amp. The microstructure of coated layer was investigated by field emission scanning electron microscope (FESEM) and the chemical composition of the coated layer was detected by energy dispersive spectroscopy (EDS). From the microstructural study it was found that the coating exhibits good metallurgical bond between coated layer and substrate. For analyzing the micro-hardness of coated layer Vickers micro hardness testing was performed along the cross-section of the coated samples. The maximum microhardness value of coated layer was 1233 HV, for sample cladded at current of 150 Amp. It was observed that increase in micro hardness value of coated sample was about 11 times higher than that of the aluminium alloy substrate (110HV). It was found that with increase in applied current, amount of microhardness of coated sample increased.

This article studies the cyclic oxidation behavior of WC-10Co-4Cr powder coatings obtained by plasma spraying on AISI316L austenitic stainless steel in an ambient air at 850°C for 50 cycles. Weight change observations of coated samples have been used to establish the oxidation kinetics, and the outcomes for the uncoated and coated specimens were compared. Utilizing scanning electron microscopy (SEM) and X-ray diffraction (XRD) the coating's microstructure has been identified before and after oxidation. XRD, SEM and energy dispersive spectroscopy (EDS) were utilized to analyse the scales surface-morphology of coated austenite steel samples following the oxidation cycle. The uncoated AISI 316L Steel had severe spalling, peeling-off, and sputtering from its oxide scale. Additionally, the scale is rich in Fe2O3, which contributed to the large weight gain. The findings showed that coatings outperform uncoated materials in terms of oxidation resistance. The coating lowered the weight gain of austenite 316 steel by 84.34%. It was discovered that the protective WO3 and Cr2O3 phase generated on the oxide scale provided higher oxidation resistance.

PurposeThe purpose of the experimental investigation was to optimize the process parameters of the fused deposition modeling (FDM) technique. The optimization of the process was performed to identify the relationship between the chosen factors and the tensile strength of acrylonitrile butadiene styrene (ABS) and carbon fiber polylactic acid (PLA) thermoplastic material, FDM printed specimens. The relationship was demonstrated by using the linear experimental model analysis, and a prediction expression was established. The developed prediction expression can be used for the prediction of tensile strength of selected thermoplastic materials at a 95% confidence level.Design/methodology/approachThe Taguchi L9 experimental methodology was used to plan the total number of experiments to be performed. The process parameters were chosen as three at three working levels. The working range of chosen factors was the printing speed (60, 80 and 100mm/min), 40%, 60% and 80% as the infill density and 0.1mm, 0.2mm and 0.3mm as the layer thickness. The fused deposition modeling process parameters were optimized to get the maximum tensile strength in FDM printed ABS and carbon fiber PLA thermoplastic material specimens.FindingsThe optimum condition was achieved by the process optimization, and the desired results were obtained. The maximum desirability was achieved as 0.98 (98%) for the factors, printing speed 100mm/min, infill density 60mm and layer thickness 0.3mm. The strength of the ABS specimen was predicted to be 23.83MPa. The observed strength value was 23.66MPa. The maximum desirability was obtained as 1 (100%) for the factors, printing speed 100mm/min, infill density 60mm and layer thickness 0.2mm. The strength of the carbon fiber PLA specimen was predicted to be 26.23MPa, and the obtained value was 26.49MPa.Research limitations/implicationsThe research shows the useful process parameters and their suitable working conditions to print the tensile specimens of the ABS and carbon fiber PLA thermoplastics by using the fused deposition modeling technique. The process was optimized to identify the most influential factor, and the desired optimum condition was achieved at which the maximum tensile strength was reported. The produced prediction expression can be used to predict the tensile strength of ABS and carbon fiber PLA filaments.Practical implicationsThe results obtained from the experimental investigation are useful to get an insight into the FDM process and working limits to print the parts by using the ABS and carbon fiber PLA material for various industrial and structural applications.Social implicationsThe results will be useful in choosing the suitable thermoplastic filament for the various prototyping and structural applications. The products that require freedom in design and are difficult to produce by most of the conventional techniques can be produced at low cost and in less time by the fused deposition modeling technique.Originality/valueThe process optimization shows the practical exposures to state an optimum working condition to print the ABS and carbon fiber PLA tensile specimens by using the FDM technique. The carbon fiber PLA shows better strength than ABS thermoplastic material.

Background: The availability of potent immunosuppressants has paved the path towards decreased incidence of graft rejection and long term survival of the renal transplant recipients. But, with the increased life span of the patients and long term use of immunosuppressants, there has been an increase in various skin conditions; ranging from various infections to some life-threatening cutaneous malignancies. Objectives: This study was carried out to determine the pattern of different cutaneous manifestations in renal transplant recipients at Tribhuvan University Teaching Hospital, to identify the infectious and non-infectious skin manifestations in these patients and their relation with the duration of transplantation. Methodology: The present study was a hospital based cross-sectional descriptive study conducted at Tribhuvan University Teaching Hospital, Kathmandu; Department of Internal Medicine, Transplant Outpatient department and Outpatient department of Department of Dermatology from June 2013 to May 2014. A total of 114 renal transplant recipients were enrolled in the study. Results: A total of 114 renal transplant recipients with a mean age of 37.56±11.10 years were studied. The immunosuppressive regimen consisted of combinations including tacrolimus, prednisolone, mycophenolate mofetil/azathioprine along with supportive medications like antivirals, antibiotics and antihypertensives. Out of all those studied, 60 patients had a total of 61 cutaneous manifestations. The mean duration from date of transplantation to presentation to the transplant OPD for infectious dermatoses was 688.4 days (1.88 years) and for iatrogenic dermatoses was 67.5 days. The most common cutaneous manifestation was acne (41%) followed by fungal infections (27.9%) consisting of pityriasis versicolor (n=9), dermatophytosis (n=6) and candidiasis (n=2); viral infections (18%) consisting of verruca (n=4), herpes zoster (n=4) and herpes simplex (n=3); bacterial infections (4.9%) consisting of folliculitis (n=2) and erythema chronicum migrans (n=1). Gingival hyperplasia was observed in a single patient. Other cutaneous manifestations like seborrheic dermatitis and xerosis were also observed in 2 patients each during the study. Conclusion: Renal transplant recipients are susceptible to acquire various cutaneous manifestations as a result of long term immunosuppression and also due to adverse effects of the drugs used. This knowledge helps the transplant physicians for regular dermatologic screening of these patients for early diagnosis and treatment of the skin lesions.

Background: Mucocutaneous manifestations in HIV infections are common. However, they have not, so far, been studied in Nepal. The aim of this study was, therefore, to describe mucocutaneous manifestations in Nepalese HIV patients. Materials and Methods: The following is a hospital-based, descriptive, cross-sectional study conducted in the Department of Dermatology and Venereology and Antiretroviral Treatment (ART) Center of Tribhuvan University Teaching Hospital (TUTH) from May 2017, through October 2018. Patients aged 16 years and above diagnosed with HIV were included in the study, for whom history and clinical examinations were performed. The study variables were age, sex, a clinical diagnosis of dermatological problems, clinical stages of HIV/AIDS, as per the World Health Organization (WHO) classification criteria, and the CD4 count. Results: A total of 52 patients were included in the study. The mean age upon presentation was 38.77 ± 10.9 years. The mean CD4 count was 464.27 ± 255.13. Females were more affected than males (female:male = 1.4:1). Mucocutaneous manifestations were the following: fungal infections (10; 19.3%), viral infections (6; 11.6%), parasitic infestations (3; 5.8%), bacterial infections (4; 7.7%), sexually transmitted infections (2; 3.8%), seborrheic dermatitis (3; 5.8%), idiopathic pruritus (3; 5.8%), recurrent oral ulcers (3; 5.8%), urticaria (3; 5.8%), pruritic papular eruptions (2; 3.8%), eczemas (2; 3.8%), acne (2; 3.8%), angular cheilitis (2; 3.8%), xerosis cutis (2; 3.8%), and others (5; 9.6%). Conclusions: The study showed that fungal infections are common in HIV patients, followed by viral infections and parasitic infestations. Seborrheic dermatitis, idiopathic pruritus, recurrent oral ulcers, and urticaria were found to be common inflammatory skin diseases in HIV.

Due to its better mechanical qualities and corrosion resistance, metal inert gas weld hardfacing is popular in both the manufacturing and research sectors and also contributes to longer machine element service lives. It is defined as a method of achieving desired surface attributes by employing welding procedures on structural materials with relatively low qualities and low cost, known as substrate materials. The weld hardfacing helps with two important aspects of improving material qualities: first, it improves characteristics of the material that depend on the surface (such as corrosion and wear resistance), and second, characteristics that rely on the mass, such as hardness, and durability. This article reviews several studies that have been done so far on various substrates in the area of metal inert gas weld hardfacing to improve microstructure, corrosion, and mechanical characteristics. According to past researchers, various MIG welding parameters play a crucial role and can be optimised to get desirable output such as enhanced tribological, mechanical, and corrosion properties. The writers have made an effort to address the recommendations for future work in this field. Present and future researchers on hardfacing using welding would benefit from the outcome of this paper, which is also useful to many industries.

In this work, Fe-TiB2 composite coating was produced on AISI 304 stainless steel by TIG coating technique. The effect on microhardness and coating morphology were investigate by variation of TiB2 percentage in Fe matrix. The FESEM and EDAX analysis were carried out to explore the coating morphology and interfacial bonding. The Vickers microhardness test was carried out at 100 gf load to assess the coating strength against penetration, and maximum hardness value noted 606 HV0.1 for S3 (30% TiB2). Overall, coating characteristics were good, the microhardness increased 2.66 times as compared to the substrate (227 HV0.1), and developed a uniformly distributed (TiB2) and crack free coating.

Introduction: Novel Coronavirus disease has caused a substantial halt to the ongoing world in every aspect. There are medical and social implications of the disease. Cutaneous manifestations have been reported to be a part of the disease as well. Dermatologists globally are in dilemma with the clinical practice because of the fear of acquiring the disease. Objectives: This article aims to recommend best practice measures that can be followed in local scenario for re-opening up of dermatological services in the context of Nepal. Materials and Methods: A preliminary draft for guidance on Dermatological services based on recommendations of American Academy of Dermatology, International league of Dermatological societies, National recommendations from Ministry of Health, Nepal was sent to a panel of national experts to determine the level of consensus in first week of April, 2020. A preliminary survey was sent to all the members of Society of Dermatologists, Venereologists, and leprologists of Nepal on first week of June and a second draft was subsequently formed which was sent again to experts and revised based on the opinions of national experts. Results: A total of 19 experts participated in the preparation of draft and reached a national consensus after a series of revisions in preliminary draft. Conclusion: Agreements regarding the opening of practice in dermatology discipline have been summarized. Recommendations have been made for opening of dermatological services – opening of outpatient department, performing dermatosurgical and cosmetic procedures as well as strategies on triage of patients and use of masks.

Introduction: Most healthcare providers recognize that urticaria is frequently difficult to treat but many do not realize the substantial negative impact, chronic urticarial (CU) has on patient’s quality of life (QoL). The questionnaire specifically developed to measure health related quality of life in chronic urticaria is the Chronic Urticaria Quality of Life (CU-Q2oL) questionnaire. This questionnaire has helped to define the effects and impact on patients. Objective: To assess the impact of chronic urticaria on quality of life at tertiary level hospital in Nepal. Materials and Methods: This was a hospital based cross-sectional study conducted in the Department of Dermatology and Venereology, Tribhuvan University Teaching Hospital, Kathmandu, Nepal, over a period of one year involving 230 patients in the study. A detailed history along with the complete cutaneous examination was carried out in all patients. Results: All the 230 patients (100%) had symptoms of wheals and pruritus while eye swelling and lip swelling was present only in 20% and 25% respectively. Highest Mean scores were seen of pruritus (4.34) and wheals (4.29). Highest mean score was achieved by domain of pruritus (4.31) followed by domain of sleep (2.31), life activities (2.22), limits (2.05), looks (1.76) and swelling (1.4). Conclusion: Chronic Urticaria impacts the quality of life by affecting various aspects in patient’s life. CU-Q2oL questionnaire could reveal the involvement of various such aspects, which were seldom realized by the patients themselves. Patients had worst quality of life with symptoms of pruritus and wheals.

TiC – Fe composite coating was produced on AISI 1020 steel by the tungsten inert gas (TIG) cladding process to increase the hardness and wear resistance properties of the substrate. In this paper authors have investigated the effect of process parameters on the microstructure and hardness value of the coated layer. In this TIG cladding process the variable parameter is only current, whereas the other parameters such as scanning speed, standoff distance, and voltage and gas flow rate are fixed. Fe and TiC powders were mixed in the proper ratio of 80wt% - 20wt% and 90wt% - 10wt% respectively. The microstructure and micro-hardness value of the samples were investigated by the scanning electron microscope (SEM) and Vickers micro hardness tester. The result of SEM shows the distribution of the coating powder in the cladded zone. Micro hardness profile shows the variation of the hardness value in the cladded zone as well as in the substrate. The hardness value decreases with increase in distance from top surface of the cladded layer, which is due to difference in cooling rate. Also, the hardness value of cladded layer decreases with increase in current from 140A to 150A. The maximum hardness value of cladded layer was achieved as 262 HV0.05with 140A current and composition of 90 wt.% - 10wt% (Fe - TiC), which was nearly two times higher than that of the as received AISI 1020 steel substrate. Keywords TIG, Microstructure, Micro hardness, Titanium Carbide (TiC), Iron (Fe) powder.

The present paper describes about the Al-Ni-Al2O3 composite coating, which was developed on AA1100 aluminium alloy by gas tungsten arc (GTA) cladding method. The coating was developed by use of different composition of Al, Ni and Al2O3 mixed powders. Scanning electron microscopy (SEM) with energy dispersive x-ray (EDS) and x-ray diffractometry (XRD) were used to examine the microstructure and phase formation of the coating. Vickers microhardness and dry sliding wear test were used to study the mechanical and tribological properties of the coated layer under various normal loading conditions. It was observed that the increase in percentage composition of Al2O3 improved the metallurgical and mechanical properties of the coated layer. It was found that due to the development of Al2O3 reinforced intermetallic matrix composite the hardness and wear resistance of coated layer increased as compare to the AA11000 aluminium alloy substrate. It was also found that due to these phases the coefficient of friction of coated layer was lower than the substrate and the wear resistance of coated layer was higher than that of the substrate. The maximum hardness of coated layer was found to be nearly 26 times higher than that of the AA1100 aluminium alloy substrate. Also, the wear resistance of coated layer was nearly five to eight times higher than that of the AA1100 aluminium alloy substrate.

In the present study, various compositions of TiB2-Co coating were deposited on AISI 1020 mild steel by tungsten inert gas cladding method. In this work, various heat energy of TIG with a fixed travelling speed of 1.5 mm s−1 was used to deposit the coating layer. The aim of this study was to investigate the optimal heat input of TIG to develop a thick layer in terms of coating microstructure and bonding quality. The influence of cobalt addition and current variation on microhardness and wear properties of the cladded layer was also investigated. The metallographic examination and microstructural analysis were investigated by x-ray diffraction, scanning electron microscope (SEM) and energy dispersive spectroscopy. The microhardness and wear rate have been analyzed by Vickers microhardness and dry sliding wear test, respectively. The investigations reveal that the influence of heat input on the wear resistance and hardness of the coated layer was significant. The microhardness value increases with increase in wt.% of TiB2 coating powder when TIG parameter is constant. The microhardness value also increases with decrease in heat input of the TIG when composition of the coating is kept constant. The maximum microhardness value was achieved up to 2563 HV0.1 which was 15 times higher than the substrate hardness value of 170 HV0.1. From the wear test result, it was noticed that the minimum wear rate found was 8.24 × 10–8 g Nm−1 for the coating composed by lower heat input (720 J mm−1) and higher wt.% of TiB2 (90 wt.%).

Recurrent pyogenic granuloma with satellitosis is an uncommon condition with majority of cases resolving within one year after treatment. We report a case of recurrent pyogenic granuloma in a middle aged man who kept on relapsing at different point of time despite treatment with electrocoagulation, cryosurgery and oral methotrexate. The case highlights the unusual presentation of relatively common condition of pyogenic granuloma.

In this work, an experimental investigation of surface mechanical properties like microhardness, wear resistant and coefficient of friction (COF) of coated surface of AISI 304 stainless steel were carried out. GTA coating method was used to fabricate Titanium-Silicon carbide (Ti-SiC) metal matrix composite (MMC) coating on the surface of AISI 304 steel to improve its surface mechanical properties. Ti-SiC coating was accomplished through GTA process with heat input 663 J/mm and keep 3 mm distance from tungsten electrode tip to the substrate with the help of semi-automatic moving tractor. FESEM analysis was performed at cross section of the coated layer to explore the distribution of SiC particle in Ni matrix and interfacial bounding of MMC with substrate. Maximum microhardness was recorded 639 HV0.1 and 575 HV0.1 for 30% SiC and 20% SiC constituents in coated layer respectively, whereas average microhardness of the substrate was noted 237 HV0.1 by Vickers microhardness tester. Relative wear resistant was registered 3.4 and 2.3 times that of the steel substrate against 400 grades SiC paper, by pin on disc tribometer. Coefficient of friction (COF) was recorded with the help of data acquisition system (DAS) attached with tribometer..

In this study, Titanium (Ti)-Titanium diboride (TiB2) metal matrix composite (MMC) cladding layers were fabricated on an AISI 304 stainless steel substrate by the gas tungsten arc (GTA) cladding process. The composite cladding layer was produced using different powder mixtures: 85 wt% TiB2−15 wt% Ti, 75 wt% TiB2−25 wt% Ti, and 65 wt% TiB2 −35 wt% Ti. During cladding, the GTA process currents were used in the range of 70 A to 90 A with 10 A interval differences and the scan speed in the range of 1.1 mm sec−1 to 1.9 mm s−1 with 0.4 mm s−1 interval differences. All samples were investigated for mechanical properties, microstructure, and phase analysis by Vickers microhardness, scanning electron microscopy (SEM), Energy dispersive x-ray spectroscopy (EDX), and x-ray diffraction (XRD) respectively. The x-ray diffraction (XRD) findings indicate that the composite coatings consist of TiB2, TiB, Ti, Fe3C, B4C, and NiTi phases. The presence of elements B, C, Ti, Cr, Mn, Fe, and Ni in the coating was confirmed by x-ray energy dispersive spectroscopy (EDX). The maximum microhardness value of the composite coating was enhanced in the range of 1639 HV0.1 to 3781 HV0.1, whereas the microhardness of the AISI 304 stainless steel substrate was 194 HV0.1. The average wear rate of the coated samples was determined in the range of 11.09 × 10−9 g N−1-m−1 to 27.63 × 10−9 g N−1m−1, whereas the average wear rate of the AISI 304 steel substrate was 88.414 × 10−9 g N−1m−1. It can be concluded that the maximum micro-hardness of the composite coating increased by 9-19 times than that of the nominal substrate (AISI 304 stainless steel). Also, the wear resistance of the composite coating enhanced by 8 times as compared to AISI 304 steel substrate. It is demonstrated in this study that the processing current, TiB2 content, and scanning speed have significant effect on the microstructure, mechanical, and tribological features of the cladding layers under consideration.

Coating of surface is a cost-effective way to make materials, equipment, and machine components with desired surface characteristics including high hardness, resistance against erosion, wear and corrosion. To obtain the necessary characteristics, several coatings are employed. The surface characteristic of the AISI1045 steel is not optimum, despite its desired strength, resistance against wear, hardness or corrosion. Thermal spraying is currently a leading way in which materials are avoided for days to wear abrasively, corrosion at high temperatures, erosive wear and stress because of increased material life in use. Spraying using high-velocity oxygen fuel (HVOF) is a kind of thermal spraying noted for its resistance against wear, micro-hardness and thick micro structured coatings. The aim of this review paper is to provide a state-of-the-art about the research done by various scholars to improve physical, mechanical, wear, erosion and corrosion characteristics of AISI 1045 by the application of different or combination of coating powders utilising the HVOF Spray method.

The main objective of the present work was to enhance the mechanical properties of AISI 1020 steel by depositing the TiB2-TiO2 composite coating on it with the help of the tungsten inert gas (TIG) cladding process. The semi-solid mixture of 50 wt% of TiB2 and 50 wt% of TiO2 was preplaced on AISI 1020 steel and a TIG torch was used as heat source to melt the preplaced layer as well as substrate layer to produce the new coating layer. Characteristics of the cladded layer were examined using Vickers microhardness tester, energy dispersive spectroscopy (EDS), scanning electron microscope (SEM) and x-ray diffractometer (XRD). The TIG currents have shown a significant influence on the microstructure and mechanical properties of the coated layer. Metallography result also shows that the input current of the TIG cladding has considerable effect on the microstructure and quality of the coating. Microstructural changes in the clad layer were studied in detail. The Vickers micro-hardness value of the coated layer increases with decrease in input current and maximum microhardness was achieved about 568 HV0.05 which was about 3.5 times higher than that of the substrate (157 HV0.05). The dry sliding abrasive wear test was performed against EN31 hardened alloy steel as counter body by pin-on-disc tribometer with sliding distance of 1036 meters. The coating produced at lower TIG current (110 A) exhibits minimum average wear rate 1.46 × 10−6 g N−1m−1 while coating processed at higher TIG current (155 A) exhibits higher average wear rate 2.18 × 10−6 g N−1m−1. It was also concluded that the wear rate of the TiB2-TiO2 coating decreases with decreasing processing current and minimum wear rate (1.46 × 10−6 g N−1m−1) obtained up to 2.5 times lower as compare to wear of AISI 1020 mild steel substrate (3.65 × 10−6 g N−1m−1) which makes the TiB2-TiO2 coating suitable for application as wear resistance components. The average coefficient of friction also decreases with increasing TIG current and found maximum (0.76) and minimum (0.58) for the coating deposited at 110 A and 155 A current, respectively.