Selective oxidation induced wear degradation in cemented carbides

Understanding the wear micro-mechanisms of metallic binders is a prerequisite to designing durable cemented carbides for drilling applications. Here we studied the oxidational wear behaviors of WC-based composites encompassing particularly the CoAl binder (& alpha; phase, comprised of 5.7 wt% Al and bal. Co) and the CoFeAl binder (B2 phase) with same Al content. Unlike the oxidation of Co in the CoAl, selective oxidation of Al occurred unexpectedly in the CoFeAl, which weakened the binder integrity and aggravated the wear losses. Such unique behavior was rationalized computationally, where the Al2O3 formation was attributed to the low energy barrier to Al diffusion in the B2 structure. These findings could lay a useful basis for future development of robust cemented carbides.