The evolution of multi and hierarchical carbides and their collaborative wear-resisting effects in CoCrNi/WC composite coatings via laser cladding

This study successfully prepares CoCrNi-xWC (x = 0, 5, 15, 25 wt%) composite coatings by laser cladding. The phase composition, microstructure, mechanical properties, and wear resistance of the composite coatings are then analyzed. In particular, the evolution and synergistic effects of the multi and hierarchical carbides derived from the decomposition of the original WC are discussed in detail. The phase composition changes from a single FCC phase to FCC and complex multiple carbide phases of WC-rich carbides + Cr-rich carbides. The microstructures are typical dendritic structures, multi and hierarchical carbides appear in the interdendritic region, and many eutectic carbides begin to emerge. Multiple carbides make up large amounts of clusters, and eutectic carbides play a continuous bridging role between the W-rich, Cr-rich carbides and the FCC solid solution. The microhardness of the coatings increases from 191.8 to 503.4 HV, while the mechanical properties of the interdendritic region are better than those of the dendritic region. Thus, the collaborative wear-resistant effects of multiple carbides provide effective protection against wear. Multi and hierarchical carbides in the CoCrNi/WC composite coating can significantly improve its mechanical properties and wear resistance.