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Investigation of HVOF processed carbide based coating on AISI-4340

Presently, materials exhibiting good strength properties especially grade 4340 steel is employed in aerospace sectors in landing mechanism. The components are usually coated by hard chromium to obtain better corrosion and wear resistance. During hard chromium coating, harmful hexavalent chromium is produced posing serious threat to health and environment. To bring about modification in the surface properties of engineering parts, thermal based coatings are deployed. The HVOF (High-velocity-oxygen-fuel) technique paves the way for replacing the conventional coatings. The objective of this study is to conduct a comparative analysis involving Tungsten carbide and Chromium carbide-based coatings deposited by HVOF technique on AISI 4340 steel. The structural and mechanical properties were characterised with the help of EDAX and SEM. The Vickers micro hardness tester is used to evaluate the hardness of coating. Wear resistance of the substrate is analyzed using Pin-on-Disc testing method. The effect of surface modification on attributes like hardness, surface morphology and wear behaviour is examined. The results confirmed the coating with Tungsten carbide exhibited enhanced performance in all aspects of attributes compared to chromium carbide.