Experimental characterization and fatigue behavior of thermally and mechanically treated 316L stainless steel MIG-welded joints

The improvement and optimization of post-weld treatments in the case of austenitic 316L stainless steels are, to a large extent, a condition of the service life of the associated structures. In this regard, mechanical brushing and heat treatment are post-weld techniques dedicated to the assembly of mechanically welded structures applicable in the aeronautics, food, and transport sectors. In this study, two techniques are applied to welded joints: mechanical brushing and heat treatment at high temperature. The base material is austenitic stainless steel with molybdenum (AISI316L) in sheet of 5-mm thick. The adopted welding process is Arc Welding under Metal Inert Gas (MIG). Monotonic Tensile test, micro-hardness measurement, low cycle fatigue, micro-hardness measurement, and MES (scanning electron microscopy) observation were conducted in order to qualify the welded, brushed, and heat-treated weldment. Compared with the welded and brushed samples, the treatment with heat annealing specimen maintains the longest lifetime and the lowest consolidation stress ± 0.4% imposed strain rate and 10−3/s as displacement speed. The annealing heat treatment has a softening effect on the welded structure during the test of the cycle fatigue; this is consistent with the micro-hardness levels measured in the weldment.