Functionally Graded WC-Reinforced Stainless-Steel Composites via Casting: Microstructure and Wear Performance

This study presents an effective route for producing functionally graded metal matrix composites with enhanced abrasion wear resistance by incorporating ex situ Fe–WC preforms into austenitic stainless-steel castings. The preforms, produced by cold-pressing mixed WC and Fe powders, were positioned in the desired locations in sand molds and reacted in situ with the molten steel during casting. This process generated a metallurgically bonded reinforcement zone with a continuous microstructural and compositional gradient, characteristic of a Functionally Graded Material (FGM). Near the surface, the microstructure consisted of a martensitic matrix with WC particles and (W,Fe,Cr)6C carbides, while towards the base metal, it transitioned to austenitic dendrites with an interdendritic network of Cr- and W-rich carbides, including (W,Fe,Cr)6C, (Fe,Cr,W)7C3, and (Fe,Cr,W)23C6. Vickers hardness measurements revealed surface-adjacent values (969 ± 72 HV 30) approximately six times higher than those of the base alloy, and micro-abrasion tests demonstrated a 70% reduction in micro-abrasion wear rate in the reinforced zones. These findings show that WC dissolution during casting enables tailored hardness and abrasion wear performance, offering an accessible manufacturing solution for high-demand mechanical environments.