Effects of La content on microstructure and tribological properties of laser clad Ni60/WC/La2O3 composite coatings on Cr12MoV

The Ni60/WC/La2O3 composite coatings with 0-2 wt% La2O3 content were prepared on Cr12MoV substrates by laser cladding. The microstructure and tribological properties of the coatings were studied in detail. The results revealed that WC particles were partially dissolved to form new carbides with lower hardness. The dissolution mechanisms were consisted of dissolution-diffusion, diffusion-nucleation, and penetration-dissolutionnucleation. The wear mechanism of C0-C3 coatings with La2O3 contents of no more than 1.5% was dominated by oxidative wear, while that of C4 coating with a La2O3 content of 2% was dominated by abrasive wear. The best performance of the coatings was obtained at a La2O3 content of 1.5 wt%. The hardness reached 1024.3 HV0.2, which was 3.64 times higher than that of the substrate. And the wear loss was 2.5 mg, which was 88.8% lower than that of the substrate.