Impact welding of wrought and additively manufactured 15-5 PH stainless steel

摘要

Vaporizing foil actuator welding (VFAW), a form of solid-state impact welding, is a promising technology for rapid repair of metal components. The adverse heat effect associated with this process is miniscule, so it can potentially be used to repair heat-treated components, without requiring post-weld heat treatment, thus saving significant cost and time. This work explores the feasibility of impact welding 15-5 PH stainless steel, a high-strength, heat-treatable alloy. Both wrought and additively manufactured (AM) materials were investigated for comparison. Target plates with machined grooves were used to provide the welding angles. Each target plate had 6 grooves, and each groove had a unique pitch angle: 8°, 12°, 16°, 20°, 24°, and 28°. This way, 6 welding angles can be investigated simultaneously within one welding experiment. Quality of weld was judged by peel testing, and corresponding microstructures and speed-angle welding parameters were noted. Impact velocities of 706 m/s and 700 m/s were obtained for wrought and AM flyers, respectively, using 12 kJ input energy. In peel testing, the AM weld outperformed the wrought weld at all welding angles. The highest peel load was 496 N, obtained at the 12° AM weld. The corresponding weld cross section showed a continuously bonded weld interface, characterized by clear wavy features and highly worked grains. The wavy features helped strengthen the bond by providing mechanical interlocking and by arresting cracks. The highly worked grains provided strengthening by Hall-Petch effect and strain hardening. These features correlated with high peel loads and were seen as desirable. In contrast, features which correlated with lower peel loads included voids (found at lower angles) and adiabatic shear bands (found at higher angles). By proper selection of welding parameters, desirable microstructures and properties could be obtained, and impact welding of both wrought and AM 15-5 PH stainless steel was demonstrated to be feasible, for the purpose of rapid component repair.