Effect of Tempering Temperature on Microstructure and Properties of Laser-cladded Martensitic Stainless Steel Layer

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 degrees C. and 400 degrees C. 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 degrees C. and 200 degrees C.) and medium (400 degrees C.) temperatures arc 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 degrees C.). Therefore, the as-tempered specimen at 400 degrees C. 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.