针对激光熔覆层易形成非平衡组织以及其内部的残余应力易导致熔覆层变形、开裂等问题,采用回火热处理来改善420马氏体不锈钢熔覆层的综合性能,研究了回火温度对熔覆层显微组织、力学性能及耐腐蚀性能的影响。结果表明:原始熔覆层主要由马氏体、奥氏体和M23C6碳化物组成,经200 ℃和400 ℃回火后,试样中新生成了逆转变奥氏体;回火温度对试样的力学性能有一定影响,低温(100 ℃、200 ℃)和中温(400 ℃)回火态试样的抗拉强度(约为1800 MPa)和显微硬度(约为530 HV)与原始态试样相当;随着回火温度升高,试样的延伸率逐渐增大,但高温(600 ℃)回火态试样的强度和硬度显著下降,其延伸率略有降低;400 ℃回火态试样的综合力学性能最佳,但其耐腐蚀性能较原始态试样和市售420马氏体不锈钢420MSS略有下降。

Some problems, such as distortion and cracking, can be observed in the laser cladding layers because of their non-equilibrium microstructure and residual stress. Herein, the tempering heat treatment is used to improve the comprehensive properties of a 420 martensitic stainless steel coating. Further, the effect of tempering temperature on the microstructure, mechanical properties, and corrosion resistance is investigated. The results denote that the as-cladded specimen mainly comprises martensite, austenite, and M₂₃C₆ carbide and that reversed austenite can be observed after the tempering treatment is conducted at 200 ℃ and 400 ℃. The tempering temperature affects the mechanical properties. The tensile strength (approximately 1800 MPa) and microhardness (approximately 530 HV) of the as-tempered specimens at low (100 ℃ and 200 ℃) and medium (400 ℃) temperatures are comparable with those of the as-cladded specimen. Furthermore, the elongation of the specimens increases with the increasing tempering temperature. However, the strength and microhardness considerably decrease and the elongation slightly decreases after high-temperature tempering treatment (600 ℃). Therefore, the as-tempered specimen at 400 ℃ exhibits optimum comprehensive mechanical properties but slightly lower corrosion resistance when compared with those of the as-cladded specimen and the commercial 420MSS martensitic stainless steel.