The shear impact wear behavior of Ti compound coatings

Abstract

The failure behavior of Ti compound coatings was evaluated under normal and shear impact conditions at room and elevated temperatures. Monolayers and combined multilayers of TiAlN and TiAlCN were deposited onto high speed steel by a cathodic arc ion plating process. The shear impact loading mode was obtained by rotating the coated disk specimen at a speed of 0.8 m s −1 under repetitive normal impact loading of 10 N using a CoWC ball indentor with a frequency of 5 Hz. The impact resistance under normal impact loading appeared to be higher in the order TiAlN, TiAlN/TiAlCN and TiAlCN in accordance with the adhesive strength measured by HRC indentation tests. Meanwhile the addition of shear force during repetitive normal impact loading by specimen rotation reduced significantly the failure resistance of all the films, both at room temperature and 600°C, with a change in failure mode. It was observed through progressive failure analysis with increasing repetitive loading cycles that the failure under shear impact loading was accelerated owing to the promotion of crack formation as well as laminated fragmentation by increasing tensile and shear stresses at the ball trailing zone resulting from tracking forces during repetitive instantaneous impacting and sliding. The propensity for failure became more severe owing to substrate softening for all the coatings as the temperature increased to 600°C.