Friction welding of AISI 304: effect of friction time on micro-structure, micro-hardness and tension-compression properties

During direct drive friction welding could relatively predicting the micro-structural and mechanical properties of friction-welded joints by controlling the welding conditions; friction time is an important coefficient that effects on these properties, present study focused on the effect of that time on micro-structural and mechanical phenomena during that process. The process achieved in different friction time, while welding joints investigated by macroscope, microstructure, scanning electron microscope, tensile, compression and micro-hardness tests. The micro-hardness tests were performd along the interface and axial direction. Thus, the tensile tests carried out on the standardized test piece with effective diameter of 6 mm and compression tests were extracted at welded center in three angles of 0°, 45° and 90° with test specimen of 4 mm diameter and 6.5 mm length. The results showed that with increasing friction time could be found hard zone at the interface of welded joint because of extended of high plastically deformation zone, which will responsible on decreasing some useful mechanical properties such as ultimate tensile strength and yield compression strength. However, tensile fracture position occurred adjacent to the interface at the thermo-mechanical deformation zone in the rotating side for all welding pieces, where the micro-hardness attenuated at that region.