Effects of La2O3 mass fraction on microstructure and friction-wear performances of WC − 10Co4Cr − Al2O3 coatings by laser cladding

Abstract

In order to improve the hardness and wear resistance of cold work molds, La₂O₃-reinforced WC − 10Co4Cr − Al₂O₃ coatings were fabricated on Cr12MoV steel by laser cladding (LC). The morphologies, grain sizes, and phases of obtained coatings were analyzed using a digital microscopic system (DMS) and X-ray diffraction (XRD), respectively. The effects of La₂O₃ mass fraction on the tribological performance and wear mechanism of WC − 10Co4Cr − Al₂O₃ coatings were analyzed using a ball-on-disk wear tester. The results show that the La₂O₃-reinforced WC − 10Co4Cr − Al₂O₃ coatings are composed of WC, W₂C, Al₂O₃, La₂O₃, LaAlO₃, and Fe − Cr, AlP₃Si, LaCoO₃, and LaP phases, and the hardness of obtained coatings increases with the increase of La₂O₃ mass fraction. The average coefficients of friction (COFs) of WC − 10Co4Cr − Al₂O₃ − 3%La₂O₃, − 6%La₂O₃, and − 9%La₂O₃ coatings are 0.57, 0.52, and 0.46, respectively; and the corresponding wear rates are 63.18, 47.1, and 27.99 μm³•s⁻¹•N⁻¹, showing that the friction reduction and wear resistance of WC − 10Co4Cr − Al₂O₃ − 9%La₂O₃ coating are the best among the three kinds of coatings, and the grain refinement and dispersion strengthening by the addition of La₂O₃ are the main factor affecting its wear resistance.