WC-12~22wt%Co 초경합금에서 미세조직 인자가 인장 성질에 미치는 영향

Cemented carbide is a kind of composite material in which fine particles of carbide are embedded into the matrix of a binder metal. It has a long service life because of its superior mechanical properties. In this study, the overall tensile behavior of a cemented carbide, WC-Co, was investigated by considering its characteristic microstructure parameters. Tensile strength and strain to fracture were evaluated by measuring the stress-strain curves of a standard tensile specimen. Scanning Electron Microscopy (SEM) was used to analyze both the average size and contiguity of WC carbide particles, as well as the mean free path of the Co (cobalt) binder. Specific correlations between mechanical and microstructural features were examined and elucidated for various volume fractions of the binder metal. The Co content and the mean free path of the Co binder were in a proportional relationship, and tensile strength showed an opposite tendency to Co content. Regarding Young’s modulus and strain, it was confirmed that a large difference appears depending on the crystal structure of the Co phase. Furthermore, by probing topology of the fractured surface of the tensile specimen it was determined that the existence of irregular voids could contribute to the statistical variance in the measured values. (Received December 28, 2020; Accepted January 28, 2021)