Effect of post-weld heat treatment on microstructure and 350 ℃ high-temperature plasticity of ER308L deposited metal

Using tungsten argon arc welding to prepare ER308L stainless steel deposited metal, and the effects of solution treatment at 1 050 ℃ for 2 hours on its microstructure and high-temperature tensile properties at 350 ℃ were studied. The results show that solid solution treatment promotes the partial dissolution of δ ferrite into γ austenite, reduces the δ/γ phase interface, simplifies the complex dislocation structure, and transforms the columnar grains of austenite into smaller equiaxed ones. The average grain size decreased from 384 to 81 μm. Solid solution treatment also reduces the ferrite content from 12.2% to 4.88%, and changes the morphology from skeleton and lath to granular, making the structure more susceptible to yield deformation. These changes significantly improve the high-temperature plasticity of the deposited metal and reduce the yield strength. After solution treatment, the high-temperature elongation of the deposited metal increased from 29% to 38%, the yield strength decreased from 322 to 128 MPa, and the hardness decreased from 210 to 138 HV₅.