Investigations on wear characteristics of Stellite coating by micro-plasma transferred arc powder deposition process

This paper reports on investigations of wear characteristics of the Stellite 6 coating on AISI 4130 steel substrate using micro-plasma transferred arc (µ-PTA) powder deposition process. Effects of plasma power, powder mass flow rate and travel speed of worktable have been studied in terms of secondary dendritic arm spacing, microstructure, dilution, line scan analysis and microhardness for enhancement of wear resistance of the Stellite coating. Travel speed of worktable was found to be the most important parameter affecting wear characteristics of Stellite coating. Its higher value gives smaller secondary dendritic arm spacing (SDAS) value and minimum dilution with almost no transfer of iron to Stellite coating. Analysis of microstructure, energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD) patterns revealed that the produced Stellite coating had a lamellar structure consisting of α-Co and ε-Co phases, chromium-rich carbides (Cr23C6 and Cr7C3) and tungsten-containing compounds (W2C). These carbides are responsible for imparting the higher hardness and wear resistance to the Stellite coating. Analysis of microhardness and wear found that higher travel speed of worktable also results in a lower coefficient of friction, specific wear rate coefficient and wears volume and higher microhardness. It can be concluded from this work that micro-PTA process has a capability to selectively deposit a thin and sound quality coating of Stellite on metallic substrates thus providing the techno-economic solution to their wear problems.