Microstructure and properties of Ta-reinforced NiCuBSi + WC composite coating deposited on 5Cr5MoSiV1 steel substrate by laser cladding

Abstract

Mixtures of Ni-based self-fluxing alloy + WC powders are widely used to prepare wear-resistant coatings on workpiece surfaces, and the particle size and distribution of the WC reinforcing phase affect the wear resistance and uniformity of the coatings. Here, to improve the wear resistance of the shield machine cutter ring, Ta was used as the reinforcing phase for the NiCuBSi + WC composite powders for the first time, and the wear-resistant coatings were prepared on the surface of 5Cr5MoSiV1 steel by laser cladding. The effect of Ta addition on the structure and properties of the coating was investigated, and the mechanism of Ta modification was analyzed. The results show that a good metallurgical bonding is formed between the steel substrate and the coating. Without the addition of Ta, the main reinforcing phases in the coating are large spherical WC particles and small flocculated WC and W2C particles, and the binding phase is Ni-Cu. The distribution of spherical WC large particles in the coating is not uniform, and there are Ni-based columnar crystal regions without the reinforcing phase. The addition of Ta consumed some of the spherical WC particles in the coating and took away some of the C of the WC particles to synthesize TaC in-situ, generating long rod-shaped W2C particles and embedding them in the coating, improving the uniformity of the hardness distribution of the coating. The wear resistance of the coating is 2.3 times higher than that without the addition of Ta, which is expected to improve the wear resistance of the cutter ring of the shielding tunneling machine.