Suppressing η‐phase development in steel‐cemented tungsten carbide: A spark plasma sintering study

Abstract

Abstract We describe the phase stability of a cemented tungsten carbide prepared using a high‐vanadium tool steel as the cementing/binder phase and confirm suppression of (Fe, W) 6 C η‐phase formation, attributed to the preferential formation of a V 0.78 W 0.22 C 1− x phase that exists as islands within the Fe‐rich binder matrix. The samples were prepared using spark plasma sintering (SPS), starting from commercially available WC and A11‐LVC tool steel powders. The starting powders were ball milled adding 10, 15, and 20 vol.% steel. An A11‐LVC tool steel was chosen as a low‐cost hard steel (49 HRC) that does not contain Ni or Co but has a high vanadium (~9 wt.%) and carbon (~1.75 wt.%) content. Our results show that sintering by SPS can produce high‐density (>98%) WC‐steel specimens in which the matrix wets the WC grain surfaces and formation of the brittle η‐phase is avoided. The η phase is often regarded as embrittling and undesirable, and its presence can result in degradation of mechanical properties. Microhardness values for the WC‐10 and WC‐15 vol.% steel samples were 12.3 ± 1.2 and 13.0 ± 0.9 GPa, respectively, whereas the fracture toughness values were 8.83 ± 0.48 and 8.81 ± 0.61 MPa·m 1/2 , respectively.