Enhancement of the mechanical characteristics for Inconel 700 alloy using friction stir welding with a unique tool shape

For the first time, a systematic study of the influence of tool geometry on the friction stir welding (FSW) process of Inconel 700 through response surface methodology (RSM) for modeling purposes was investigated. The tool design implemented two distinct pin probe geometries: a threaded pin with three intermittent flat faces (D1) and a fully threaded cylindrical pin (D2). The present study primarily examines the effects of these varying pin geometries on FSW performance in Inconel 700 joints. Additionally, experimental analyses, i.e., Vickers hardness number (VHN), ultimate tensile strength (UTS), and surface roughness (SR), were conducted to evaluate key mechanical properties. The response surface methodology (RSM) was evaluated as a suitable approach for determining the weld properties, with mathematical models achieving confidence levels of 93% and 98% for the D1 and D2 tool configurations, respectively. Meanwhile, the D1 pin geometry produced superior mechanical properties, i.e., UTS from 630 to 662 MPa, VHN from 93 to 110 HV, and improved surface finish compared to the D2 configuration, highlighting the design's effectiveness in enhancing FSW joint quality.