Effects of rotational speed and dwell time on the hardness and porosity percentage in FSCW process

Abstract

The Friction Stir Chip Welding (FSCW) process has been introduced as a novel method for repairing deep and cavity-type defects in aluminum components, in which machining chips are used as a filler material. In this study, the main objective was to investigate the effects of tool rotational speed and dwell time on the hardness and porosity percentage of the stir zone. For this purpose, a full factorial design of experiments was performed with two levels for each parameter; hence, four process combinations were tested. Using the analysis of variance (ANOVA) technique, the main effects and interactions were evaluated. The results showed that tool rotational speed is the most significant parameter on hardness and porosity. Increasing the speed from 1250 to 1600 rpm significantly increased the hardness, which was attributed to higher heat generation, reduced voids, and greater grain refinement in the stir zone. The interactions between rotational speed and dwell time were positive and strong. The influence of dwell time increased significantly at higher rotational speeds; specifically, at 1600 rpm. Increasing the dwell time produced the greatest reduction in porosity and the highest increase in hardness.