Twin hot-wire arc welding additive manufacturing deposition of high tungsten Stellite-6 hard-facing coating: Processing, microstructure and wear properties

In order to gain the advantages of excellent wear properties of hard-facing stellite-6 alloy, a single layer of high tungsten Stellite-6 coating was deposited onto St37 and Mo40 steel substrates using a twin hot-wire arc welding additive manufacturing process. The wire rods used were initially manufactured by a powder metallurgy route (ball milling + spark plasma sintering + extrusion) from pure raw materials. A comparative study was carried out in terms of microstructure, phase composition, hardness and wear resistance. Stellite-6 coatings were found to be metallurgically well-bonded to both substrates with proper penetration and no cracks or pores. The dendritic microstructure of Stellite-6 coating deposited on St37 substrate (S6-1) was finer with higher percentage of eutectic structure (35.3 %), higher concentration of Tungsten (W) and less amount of Iron (Fe). Consequently, S6-1 coating showed higher hardness and wear resistance due to the finer dendritic size, more and uniform distribution of Chromium (Cr-) and W-rich carbides in inter-dendritic areas and less Fe dilution.