Surface Friction and Interfacial Wear Mechanisms in CeO2-Ni/WC Cladding Layers on 45 Steel

This study investigates the insufficient surface hardness of medium-carbon 45 steel and the drawbacks associated with conventional surface modification techniques (e.g., cracking in laser cladding, weak bonding in thermal spraying, restricted thickness in chemical deposition). Series CeO2-Ni/WC composite claddings (with CeO2 content ranging from 0.5 to 2.0 wt %) were fabricated via vacuum cladding. The cladding with 0.5 wt % CeO2 (NWC5) exhibited the lowest porosity (0.0673%) and finest grain size (12.06 nm) and demonstrated the highest microhardness (1042.74 HV0.2) and elastic modulus (269.06 GPa), respectively. The interfacial friction coefficient (0.343–0.444) was significantly reduced compared to the surface friction coefficient (0.562–0.617). Wear track analysis revealed that the width in the cladding layer-to-substrate transition zone (CTSZ) was 22.1–43.2% wider than that in the substrate-to-cladding layer transition zone (STCZ). This disparity is attributed to stress concentration induced by the abrupt hardness change across the CTSZ, promoting the formation of a three-tiered step structure (with a step height difference of 2.1–4.1 µm). In contrast, the progressive hardness series in the STCZ facilitated a smoother wear surface. The dominant wear mechanism was identified as a combination of abrasive and oxidative wear. This study provides a theoretical foundation for optimizing such high-reliability components.