Understanding the diffusion wear mechanisms of WC-10%Co carbide tools during dry machining of titanium alloys

The diffusion wear between a WC-10%Co tool and a Ti54M titanium alloy was investigated by studying the reaction between both the materials using a diffusion couple and studying their behavior during a machining test. In addition to the scanning electron microscopy (SEM) study, electron probe microanalysis (EPMA) was conducted to quantitatively analyze the chemical composition in the reactive layers after different holding times at 1100 °C. The diffusion couple revealed a rapid formation of TiC carbides at the interface. The layer growth is parabolic and is mainly toward the Ti54M side. The formation of three affected zones was observed. On the tool side, the two affected zones displayed a continuous decrease in the WC content, as well as a significant enrichment in the Co amount with no WC in the Co rich zone and a decrease in the W and C contents. On the Ti54M side, the tool elements diffused into the alloy material, with the diffusion lengths of C and Co being much longer than that of W. The solubilities of C and Co remained low while that of W was almost 8-9 wt%. The WC dissolution and compositional modification caused a degradation in the mechanical integrity of the tool surface, leading to crater damage. The machining experiments validated this mechanism and tool elements could be found in the adhered titanium layer.