Linear Friction Welding of Similar and Dissimilar A36 Mild Steel and AISI304 Stainless Steel

The application of Stainless Steel (SS) and Mild Steel (MS) is a popular pair across several industrial sectors including aviation, automobile, and nuclear power. The joining of this dissimilar pair with good joint integrity in varied shapes and sizes is critical and challenging. The Linear Friction Welding (LFW) is an effective solid-state joining technique to address this issue. The reports the results on microstructural features and mechanical properties of SS-SS as well as SS-MS dissimilar LFW joints. A comparison of similar and dissimilar LFW joint is also presented to showcase the joint evolution. The joints were fabricated using LFW under varying forging pressures. To analyze the microstructural evolution in the weld zone and at weld interfaces Scanning Electron Microscopy (SEM), optical microscopy, and Vickers hardness testing were employed. The grain size in the weld centre zone (WCZ)of MS was refined from 7.11 µm to 3.59 µm and the pearlite content was found to be higher as compared to the base metal (BM). A distinct chevron-shaped flow pattern was observed at the interface of a similar weld. This pattern is driven by the severe thermomechanical extrusion of highly sheared viscoplastic layers during welding. Furthermore, SEM analysis revealed homogeneous carbon diffusion near the WCZ in both welds. The hardness profile of the welds was closely correlated with these microstructural features. The highest hardness of 491 HV was measured in WCZ in dissimilar and 354.5 HV in similar welds. The macrostructure and flash formation were found to be directly influenced by the BM properties and applied forging pressure.