Study of Infrared Thermography on Tensile Behavior of Laser Beam Welded 316LN Austenitic Stainless Steel

In this investigation, the tensile behavior of laser beam welded 316LN austenitic stainless steel was studied by infrared thermography (IRT) and compared with the base metal tensile behavior. Initially, microstructural characterization of base metal and weld bead was carried out by optical microscopy (OM). Base metal comprises an average grain size of 60 µm and LBW exhibited refined grains at the fusion zone. Very narrow HAZ around 15 µm was recorded at LBW interface. Tensile samples were prepared as per ASTM standard E8, and the test was conducted at room temperature of 26.5 °C. A strain rate of 4.4 × 10−4 s−1 was used during the tensile test of the base metal and LBW samples. Temperature variations of the base metal and weld bead were recorded by an infrared camera at different stages of deformation. Compared to LBW sample base metal sample deformed more and displayed the percentage of elongation as 64.14%, whereas LBW sample displayed less percentage of elongation around 53.2% due to lesser deformation as compared to the base metal. This is attributed to grain refinement during rapid solidification of LBW process at fusion zone. High temperatures were recorded on the base metal (39.2 °C) and center of the LBW fusion zone (30.8 °C) before just the time of fracture. This high temperature of the base metal over LBW sample indicates that the base metal deformed more compared to laser beam welded sample.