Effect of WC content on microstructure and properties of high-speed laser cladding Ni-based coating

• By high-speed laser cladding technology, the decomposition degree of WC is weakened. • The composite coating with high content of WC (60%) is prepared. • Three decomposition mechanisms of WC particles are deeply revealed. Ni/WC composite coatings with different compositions were prepared on the surface of 304 steel by high-speed laser cladding (HSLC). The microstructure and phase composition of Ni/WC composite coatings were analyzed, and the hardness and wear resistance of Ni/WC composite coatings were tested. The results show that the HSLC coatings have good surface formation without defects such as pores or cracks, and WC is uniformly distributed in the coating. WC particles hinder the dendrite growth, and the dendrite structure in the coating is significantly refined with the increase of WC content. The main phases of the coating is Ni 3 Fe, and the W and C elements diffuse into the coating, forming strengthening phases such as W 2 C and Cr 23 C 6 . Although WC particles are decomposed, the strengthening effect of the second phase is not weakened, and the decomposed WC produces fine grain strengthening and solid solution strengthening effects, thus producing multiple strengthening mechanisms for the coating. With the increase of WC content, the hardness and wear resistance of the coating are gradually improved. However, when the WC content is in the range of 30–60%, the wear resistance of the coating do not present significant change. The main wear mechanisms are adhesive wear, abrasive wear and oxidation wear.