Recent Advances in Hardmetal Thin Films and Diamond-Like Carbon Coatings for Friction Stir Welding Tools

Abstract

Friction stir welding (FSW) is solid-state welding of similar or dissimilar materials through a blend of frictional heat and plastic deformation of workpiece materials. In the present scenario, the welding of dissimilar high-strength materials is substituted by the FSW process due to its distinctive features over the conventional welding process. The FSW process’ significant difficulty in welding high-strength materials is the wear of non-consumable welding tool pins. This tool wear is due to continuous contact of the tool with the workpiece materials. In this chapter, an overview of FSW operation, critical process variables, the effect of these process variables on tool wear and mechanical properties of the weld joint, coating of hard thin material on tool surface by various methods, evaluation of coating properties (mechanical and tribological), and characterization of coating materials (SEM, TEM, EBSD, XPS, Raman spectroscopy) have been reviewed. This chapter also explores recent advances in hardmetal thin films and diamond-like-carbon (DLC) coatings and their effect on FSW tool wear, mechanical properties, and microstructural characterization of the weld joint.