Pure Ni transition layer enables enhanced WC retention and wear resistance in high-WC Ni60 composite coatings

To address the performance degradation of Ni60/60 %WC composite coatings beyond the critical WC content, this study introduces a pure Ni transition layer between the coating and 42CrMo substrate. Systematic investigations reveal that the pure Ni transition layer effectively inhibits Fe diffusion from the substrate into the coating and restricts W migration from the coating to the substrate, increasing the WC retention rate by 15.26 % compared to the single-layer coating and bringing the actual WC content close to the initial powder addition. The coating with the pure Ni transition layer achieves an average hardness of 1357.6 HV_0.2 (3.8 times that of the substrate) and forms a gradient hardness distribution. Wear tests show that its wear rates at 25 °C and 600 °C are only 27.67 % and 18.39 % of those of the single-layer coating, respectively. The enhanced high-temperature wear resistance is attributed to the reinforcement of the WC/W₂C hard phase and the lubrication of the NiO-WO₃ oxide film. This work provides a viable solution for applying high-WC wear-resistant coatings in harsh high-temperature industries such as mining machinery and petroleum metallurgy.