Friction welding influence on microstructure, microhardness and hardness behavior of CrNiMo steel (AISI 316)

For joining high Cr, Ni and Mo austenitic stainless steel (AISI 316) by direct drive friction welding (DDFW), with friction welding conditions: rotation speed of 3000 r/min, friction time of 10 s, friction pressure of 130 MPa, forge time of 5 s and forge pressure of 260 MPa. The results of microstructure showed that the temperature at the interface reached 819 ℃ while forge applied between 357−237 ℃, which subdivided welded joint into four distinct regions of highly plastically deformed zone (HPDZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and the base metal, with grain size about 10 µm, 100 µm, 90 µm and 30 µm respectively. These regions were created due to dynamic recrystallization (DRX) at the interface and thermo-mechanical deformation with heat diffusion in the neighboring regions. Whereas, high level of microhardness about 300 HV0.1 and hardness roughly 240 Hv10 at the interface due to HPDZ creation while low level of 240 HV0.1 for microhardness and moderately of 205 HV10 for hardness in neighboring regions.