Characterization and evaluation of AlCrN coated FSW tool: A preliminary study

Stemming from the success recorded in the cutting tool industries, the use of physical vapor deposition (PVD) coatings for friction stir welding (FSW) tools is a promising approach to improve their performance and useful lives and hence the economics of the process. In this study, the authors present the results of the first phase of an on-going study to test various metallurgical hard coatings for FSW tools using cathodic arc PVD coating technique for welding structural materials. Aluminum alloy 6061-T6 and alloy steel 4140 grade were chosen as workpiece and FSW tool material, respectively for this preliminary study. The tribological properties of AlCrN coating were evaluated. The tool wear and weld quality resulting from FSW were analyzed and compared for coated and uncoated tools. AlCrN coated sample exhibited improved wear resistance with weight loss of about 87% lesser compared to uncoated sample. FSW performed on 6 mm thick 6061-T6 Al alloy plate showed that AlCrN coated FSW tool produced full penetration weld with no major defects. Also, no delamination of the coating was observed and no trace of the coating was detected in the weld for the FSW paramters employed. Examination of the tools after the FSW showed that the coated tool experienced less reduction in the tool pin dimension as compared to the uncoated tool.