Microstructure and properties of laser cladding WC/Ni composite coatings with different compositions

Abstract This study addresses the issue of cracking in WC/Ni60 cladded layers with high WC content. The effects of different WC contents on the formation quality, microstructure, and microhardness of WC/Ni15 cladded layers, as well as the influence of various nickel alloys (Ni15, Ni35, and Ni60) on Ni+20% WC cladded layers, were investigated. The results show that as the WC content increases, the microstructure of WC/Ni15 cladded layers becomes denser and finer, with the formation of W-rich compounds and carbides such as Ni2W4C and W2C, resulting in an increase in hardness. When the WC mass fraction reaches 50%, cracks and larger pores appear in the WC/Ni15 cladded layer, and the higher viscosity of the melt pool causes W-rich compounds to be uniformly distributed throughout the layer. At a WC mass fraction of 20%, the pores in the cross-sections of WC/Ni15, WC/Ni35, and WC/Ni60 cladded layers decrease sequentially. The microstructure transitions from cellular to dendritic, the dendrite spacing decreases, and hardness increases, with W-rich compounds mainly concentrated at the top of the cladded layer. In the Ni60+20% WC cladded layer, the increase in borides leads to the formation of cracks. The Ni15+40% WC cladded layer, however, does not exhibit cracks and has a hardness comparable to that of the Ni60+20% WC cladded layer. Under the same conditions, adding a high content of WC particles to Ni15 powder results in a crack-free cladded layer with higher hardness, making it more favorable for industrial applications of WC/Ni cladded layers.