Tungsten carbide-cobalt hardmetal

The combination of tungsten carbide and cobalt is responsible for the so-called hardmetal disease. 

All these findings very clearly demonstrate that only the combination of cobalt with tungsten carbide is a necessary condition to induce severe alveolitis leading to fibrosis. The pulmonary response produced by hardmetal dust is much more pronounced than that caused by pure cobalt or cobalt compounds, while WC alone shows almost no effect. Hardmetal disease is not a consequence of one of the hardmetal components but is a result of interaction between Co and WC particles, producing toxic activated oxygen species, presumably hydroxyl radicals. 

WC-Co hardmetal is a sintered material consisting of brittle tungsten carbide (WC) crystals bonded by a tough cobalt-based binder. Figure 1 shows the microstructure of a typical commercial WC-Co hardmetal. 

A nozzle opening of a sandblaster may suffer severe wear during operation. This can be countered by using hot-pressed boron carbide (B4C), which is expensive but is very hard and has a long lifetime in this application. Sintered alumina or hardmetal (a cermet of tungsten carbide sintered with some cobalt or nickel metal) show more wear but are suitable as well and cheaper to make. 

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