Co-enhancing the Mechanical Property and Corrosion Resistance of Selective Laser Melted High-Strength Stainless Steel via Cryogenic Treatment

Abstract

The mechanical properties and corrosion resistance of selective laser melted high-strength martensitic stainless steel were enhanced by cryogenic treatment. The microstructure of the martensitic stainless steel contained fine martensite lath due to fast cooling rate. Simultaneously, there were bulk austenite formed at the boundary of molten pool and thin austenite film distributed at martensite laths. After cryogenic treatment, the content of austenite decreased from 25 to 19.2%, and Cu-rich precipitates were refined to 1-3 nm during subsequently aging due to decreasing of lattice constant, which were benefit for the hardness and tensile strength of the selective laser melted 15-5PH martensitic stainless steel without negatively influencing on the plasticity. Simultaneously, the electrochemical tests showed that the pitting potential and passivation film stability gradually increased after cryogenic treatment. Finally, the effect of cryogenic treatment on microstructure for selective laser melted high-strength martensitic stainless steel was discussed.