Mechanical and tribological characterization of AlCrN coated spark plasma sintered W–25%Re–Hfc composite material for FSW tool application

Abstract

In this study, the mechanical and tribological properties of cathodic arc physical vapor deposited AlCrN coating on spark plasma sintered W–25%Re–HfC composite tool material were investigated. AlCrN coated and uncoated W–25%Re–HfC samples were tested using pin-on-disk wear test configuration to evaluate the coating performance. Scratch test result shows that the adhesion strength of the coating is about 25 N, which indicates that the coating exhibited good adhesion to the composite material. Specific wear rate of the coated sample is 10 times lower than that of the uncoated sample under identical conditions. The high wear rate of the uncoated W–25%Re–HfC sample is due to extensive abrasive wear. However, the coated sample is dominated by oxidation wear mechanism leading to the formation of dense Al2O3 and Cr2O3 oxides with good wear resistance properties. The improved wear resistance of the coating is attributable to the combined excellent mechanical properties, high adhesion to the substrate, low coefficient of friction and the formation of protective oxides. This study demonstrates by way of tribological analysis the feasibility of improving the life and performance of expensive FSW tools by the application of cathodic arc AlCrN PVD coating. Keywords: Friction stir welding, PVD AlCrN coating, FSW tool wear, W–Re alloy