Friction time effect on joint strength of AISI 316 using continuous drive friction welding

The present study investigates the influence of friction time on the microstructural and mechanical properties of friction-welded joints for Ni-Cr-Mo steel (AISI 316) using the continuous drive friction welding (CDFW) process. The research encompasses macro- and microstructural analysis, microhardness measurements along the axial direction and at the interface, tensile testing with effective diameters of 4 mm and 6 mm, and compression testing at angles of 0°, 45°, and 90° using specimens with dimensions of 4 mm in diameter and 6.5 mm in length. Additionally, impact tests were performed in symmetric and non-symmetric positions. The findings reveal that increasing friction time leads to the formation of a pronounced flash on the stationary side compared to the rotating side. Microstructural analysis shows fine grains in the highly plastically deformed zone (HPDZ) at the interface and elongated grains in the thermo-mechanically affected zone (TMAZ). At longer friction times (10 s), microhardness values reached approximately 300 HV0.1 at the welding interface, decreasing to 240–230 HV0.1 in adjacent regions. At shorter friction times (6.5 s), microhardness values were moderately lower, ranging from 260 HV0.1 to 240 HV0.1 at the interface and neighboring areas. For 6 mm diameter specimens, ultimate tensile strength (UTS) decreased with increasing friction time, reaching its lowest value at 8.5 s, while 4 mm diameter specimens exhibited a linear reduction in UTS with longer friction times. Compression tests demonstrated the highest yield strength at 0°, with values decreasing as friction time increased, indicating anisotropy in AISI 316 under friction time influence. Impact strength declined in non-symmetric positions compared to symmetric ones as friction time increased.