Wear properties and microstructure of Ni-based cermet layer by laser cladding

Key words:  laser cladding  Ni-based cermet  microstructure  micro-hardness  wear resistance

Abstract:

Laser cladding of self-made Ni-based ceramic layer was prepared on a 45 steel surface by transverse flow CO₂ laser. The morphology, phase composition, microstructure, micro-hardness and wear properties of the layer were investigated. Results show that the formability of cladding layer is excellent. There are Ni-Fe solid-solution, Fe₂B, WC, M₇C₃ and M₂₃C₆ carbides in the coating. Dentrite is highly developed on the bottom of the cladding layer. In the microstructures of the central and top zone there are plenty of grains with long strip shape, and a few chrysanthemum-like grains are distributed on the substrate, but the grains of the top zone are finer and denser. There is an interface transition region, where coarser dendrites grow in the direction vertical to the bonding interface. The micro-hardness of cladding layer is about 600 HV0.2, and it has no significant fluctuations along the horizontal direction. The friction coefficient, the wear weight loss and the wear degree are significantly reduced compared with 45 steel, and the anti-wear characteristic is remarkably improved.