Transition in Tensile Deformation Behavior of Fe-Cr-C/Low-Carbon Steel Wire Arc Additive Manufactured Joint Before and After Solid Solution Heat Treatment

The valve disk, composed of low-carbon steel, was susceptible to bond fracture during the long-term service. Wire arc additive manufacturing (WAAM) served as an alternative technique for part repairs. To achieve strong bonding, a dissimilar welding material (12Cr-0.3C) was selected for WAAM application. To reduce residual stress, a solid solution treatment was conducted. Results indicated that the untreated fused zone (FZ) group exhibited superior formability and a complex microstructure, heat-affected zone (HAZ) showed both coarsening and refinement of α', and the base metal (BM) displayed hardness akin to the solid solution with notable fluctuations. Solid solution treatment eradicates retained austenite, with α' and carbides prevailing in the matrix, leading to a decrease in FZ's ultimate strength. HAZ is absent, α' is present, and pearlite is evenly distributed. The BM side displays activated slips prior to fracture, with a low strain (20%) indicating the tensile direction. High strain (30%) activates multiple slip systems in the untreated group but not in the solid solution group. The tensile test revealed the yield strength of the solid solution group to be 242.4 MPa, whereas that of the untreated group was 507 MPa. A subtle difference in elongation exists between the untreated group (37%) and the solid solution group (32.3%). The primary concern is plastic fracture, which is influenced by the size and prominence of microvoids.