The Study Of Crystal Type And Composition Of Cobalt Phase In Hardmetal Through Electrolysis Corrosion

In order to effectively study the Co phase of WC-Co hardmetal, electrolysis corrosion was used to partially or completely remove WC grains from as-polished surface of hardmetals with various WC grain sizes to obtain a near-pure Co phase layer. The morphology, crystal type and composition of this Co phase layer had been studied using SEM, XRD, EDS and WDS analysis. The XRD patterns showed that the Co phase of typical commercial hardmetals is mainly of fcc type and a small amount of hcp-typed Co phase appears in coarse grade hardmetals. However, significant hcp-typed Co phase was observed in as-polished surface of coarse grade hardmetals, due to the fact that grinding process can lead to the phase change of fcc-Co→hcp-Co. The WDS results showed that the Cr content in Co phase of ultra-coarse hardmetal can be determined accurately with the help of electrolysis corrosion.