Direct Drive Friction Welding Influence on Metallurgical, Mechanical, and Electrochemical Properties of AISI 316

This study examines the influence of direct drive friction welding (DDFW) on Cr-Ni-Mo steel (AISI 316) with a focus on metallurgical, mechanical, and electrochemical properties. Different friction times, ranging from 5.5 s to 12 s, were investigated while keeping other conditions constant. Temperature measurements, Macro-microstructure, microhardness, tensile tests, tensile fracture morphology, and electrochemical tests were performed. The results show that the maximum temperature (Tmax) exhibits a slight increase with an extended friction time. The temperature variation ranges from 826 °C to 879 °C for friction times of 5.5 s and 12 s, respectively, thus, the welded joint is divided into four distinct regions: highly plastically deformed zone (HPDZ), thermo-mechanically affected zone (TMAZ), heat-affected zone (HAZ), and the base metal, with grain sizes of approximately 10 μm, 100 μm, 110 μm, and 25 μm, respectively. The HPDZ is responsible for the microhardness elevation at the interface, while the TMAZ and HAZ are responsible for the microhardness attenuation in the neighboring region and weak in tension. The ultimate tensile strength (UTS) related to AISI 316 decreases from 104.50 to 94.57% for 5.5 s and 12 s, respectively, and the ductility related to AISI 316 decreases from 58.21 to 54.05% for 5.5 s and 12 s, respectively. Tensile fractures occurred at the TMAZ with a ductile fracture mode and cleavage features with irregular forms of microcavities throughout the fingerprints. The results of the electrochemical test clearly indicate that the weld zone (WZ) exhibits superior corrosion resistance compared to the base metal (BM), AISI 316. Further analysis of the results revealed that the TMAZs are more susceptible to pitting than the HAZ. Thus, only a few micro-pits are observed in the HPDZ compared to the pitting state in the TMAZs.