Microstructure and properties of Invar steel/06Cr19Ni10 steel by laser welding and TIG welding

To obtain good dissimilar material welded joints between Invar steel (4J36) and 06Cr19Ni10 steel, the forming characteristics, microstructure, and mechanical properties of laser welding and TIG welding joints were systematically compared. Laser welding (power: 2 700 W, speed: 1.2 m/min) and TIG welding (current: 65–75 A, voltage: 12 V) were adopted, and the weld morphology, microstructure, hardness distribution, tensile properties, bending properties, and impact energy were analyzed. Results indicate that both processes produce defect-free welds. Laser-welded joints form fine columnar crystals due to the high cooling rate, with a microhardness of 140–150 HV, which is higher than that of TIG-welded joints of approximately 121 HV. The tensile strength of laser-welded joints is 431 MPa, accounting for over 95% of the Invar steel base metal, with fractures occurring in the Invar steel base metal zone. This outperforms TIG-welded joints, which have a tensile strength of 395 MPa and fracture in the weld zone. Both welded joints pass the 180° bending test without cracks. The impact absorption energy of laser-welded joints (26.1 J) is higher than that of TIG-welded joints (25.5 J). The fine-grained microstructure and ductile fracture dimple characteristics indicate that laser-welded joints have better comprehensive performance. This study provides data support and a theoretical foundation for the welding of dissimilar materials in aviation applications.