Microstructural evolution and mechanical properties of deep-penetration vacuum laser beam welded GH4169 superalloy

A thick-section GH4169 superalloy joint for safety-critical hot-section components was welded via a novel vacuum laser welding process. This process utilizes a vacuum environment to enhance laser welding penetration ability. The microstructure and mechanical properties of the deep-penetration welded GH4169 superalloy were systematically investigated. The volume fraction of brittle Laves precipitate reached an exceptionally low level due to lower heat input and faster cooling rate involved in vacuum laser beam welding. The results indicated that a more than 17.5 mm-deep defect-free laser weld with a sound weld appearance was prepared. The yield strength and ultimate tensile strength of the weld joint in the as-welded condition were 434.6 and 775.9 MPa, respectively. Post-weld heat treatment promoted the precipitation of γ″ phase, which greatly improved the strength of the joint.