Microstructure and mechanical properties of austenitic stainless steel welded with Co-based wires in cryogenic temperature environment

The microstructure of 316 L austenitic stainless steel, welded with Co -based wires (Stellite 6 and Stellite 12), is closely related to its phase transformation, fracture, and cryogenic mechanical properties. The analysis involved tensile tests, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). The results indicated that significant two -stage train hardening occurred in the matrix specimen at cryogenic temperatures, with a tensile strength of 1494 MPa compared to 578 MPa at room temperatures. This phenomenon was primarily attributed to the formation of numerous martensite particles, accompanied by fine twin lamellae. Ductile fracture predominated in the failure process of matrix specimens, under all temperature conditions. Co -based welding wires demonstrated strong metallurgical bonding with matrix materials. Specifically, the specimen welded with Stellite 6 exhibited an excellent combination of yield strength (596 MPa), tensile strength (887 MPa), and elongation (16%) at cryogenic temperatures. The cryogenic failure mechanism of the welded specimens involved a dimple and quasi -cleavage composite fracture. This work offers effective guidance for the use of 316 L austenitic stainless steel as a valve material in cryogenic environments.