The Influence of WC Content on the Microstructure and Wear Resistance of Laser Cladded WC/Co-Ni Matrix Composite Coating
W. He and X. Chen
A WC/Co-Ni composite coating was prepared on the surface of high-speed steel by laser cladding technology. The effects of WC content on the microstructure, phase composition, microhardness and wear resistance of the coating were comparatively analyzed. The results showed that the surface of WC/Co-Ni composite coating was flat and uniform, with no obvious defects such as pores and cracks, and a benign bond was formed between the coatings. The cladding layer is dominated by WC, M12C (Fe6W6C, Co6W6C, Mo6Co6C) eutectic structure and γ-(Ni, Fe) phase. When the content of WC was 90%, the distribution of WC particles was uneven, there were more voids and microcracks in the surrounding tissue, and local segregation appeared in the coating. When WC content was 70%-80%, the precipitated tissue distribution was uniform, and Cr23C6, (Fe, Co, Mn)2C and other phases were added, which enhanced the hardness and wear resistance of the coating. When WC content < 60%, WC particles were completely dissolved in the coating and the size of precipitated tissue gradually decreased. In terms of properties, the average hardness of the Co60/WC reinforcement layer decreased with the decrease of WC content, from 1221.31HV0.2 to 1066.58HV0.2, a decrease of 12.67%, while the hardness distribution of the coating tended to be uniform, and the overall standard deviation of hardness decreased from 153.26HV0.2 to 25.61HV0.2, a decrease of 83.29%; Under the same friction condition, the wear amount of the cladding layer decreases first and then increases with the decrease of WC. When WC content is 80%, the wear resistance of the coating reaches the best. The wear mechanism of the cladding layer is mainly abrasive wear, and the adhesion wear area gradually expands with the decrease of WC.
Keywords: laser cladding, transition layer, WC/Co-Ni composite coating, WC content, microstructure, microhardness, wear resistance