Abstract
Pulsed Nd:YAG laser welding of 17-4 martensitic precipitation hardening (PH) stainless steel (SS) is investigated. In order to achieve optimum laser welding parameters, bead on plate (BOP) welding was conducted on 17-4 PH SS. No crack was detected in the weldments, and microstructure of weld metal was δ-ferrite in the martensite matrix. Resistance to cracking of weldment was correlated to the presence of δ-ferrite in the weld metal, and using pulsed Nd:YAG laser as a low heat input welding method. Four HAZs were distinguished and microstructure evaluation in each zone is discussed. In the second part of this research, pulsed Nd:YAG laser welding of similar 17-4 PH SS in butt joint configuration was performed. Microstructure characterization and mechanical properties of weldment in as-welded and aged in 550 °C for 30 min conditions were investigated and compared. Aging caused precipitation of copper-rich clusters and increasing hardness of weld metal and homogenizing the hardness in HAZ. Tensile test results demonstrated that the failure occurred in the base metal and showed features of ductile fracture.
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