Study on Microstructure and Properties of Ni60A Coating by Laser Cladding on 42CrMo4 Steel Surface

Ni60A multi-layer and multi-pass coatings were prepared on the surface of quenched and tempered 42CrMo4 steel by adopting the coaxial powder feeding laser cladding technology, achieving dense and defect-free forming of the cladding layers. Microstructural analysis shows that the overall control effect of the white etching layer formation on the substrate after cladding is excellent, and the heat-affected zone (HAZ) is relatively narrow, indicating an ideal control effect. A clear composition gradient is formed between the cladding layer and the substrate, with a good metallurgical bonding interface. Mechanical property tests reveal that the average hardness of the cladding layer is 2.27 times higher than that of the substrate; however, the HAZ exhibits softening fluctuations, yet it still achieves significant hardening compared with the substrate.. The tensile properties of the cladded samples show a certain degree of decrease compared with the base material. Fracture analysis indicates that the cladding layer undergoes brittle fracture, while the HAZ also generates intergranular brittle fracture due to composition changes and stress concentration. In contrast, the base material maintains ductile fracture.