Recent Developments in Friction Stir Welding Tools for Weld Bead Defects Minimization – A Review

Friction stir welding (FSW) is considered one of the most prominent methods for joining ductile materials. In this process, joining occurs in a plastic state without melting the base metals. Therefore, there is a lack of solidification cracking and shrinking of friction stir weld joints. Although, the improper stirring action of the FSW tool reduces the frictional heat input and flow of plasticized material, which deteriorates the weld joint quality. Insufficient and excessive heat input both results in the formation of weld flaws. The FSW is assisted with various new supporting tools to reduce weld flaws. The main objective of this paper is to provide collective information regarding supportive tool systems employed with FSW for the mitigation or elimination of weld flaws. FSW tool systems such as non-rotational shoulder assisted FSW, counter-rotating twin tool, reverse dual rotation, self-reacting tool, and in-situ rolling tool, and their impact on the weld joint formation is presented in this article. This paper also presented an overview of the remarkable effect of optimizing the FSW process parameters and the influence of tool pin profiles on weld joint quality. From this review, it is concluded that various FSW supporting tool systems significantly reduce the weld flaws.