Microstructure Of Cemented Carbides Research Articles

Controlling WC/Co two-phase microstructure of cemented carbides additive-manufactured by laser powder bed fusion: Effect of powder composition and post heat-treatment

In this study, an attempt is made to control the WC-Co two-phase microstructures by laser powder-bed fusion (LPBF) process using cemented carbide powders with different compositions of WC-25Co (mass%) and WC-17Co (mass%) and post heat-treatment at 1380 °C. The as-built cemented carbide samples had different microstructures from those of the cemented carbides fabricated by conventional manufacturing methods. The microstructures of the as-fabricated WC-25Co and WC-17Co cemented carbides were characterized by two types of regions. Region 1 consisted of W2C and W3Co3C phases, including numerous pores and defects. Region 2 consisted of WC and Co phases. Post heat-treatment of the LPBF-built WC-25Co sample at 1380 °C led to the formation of a defect-free WC-Co two-phase microstructure. In contrast, the W3Co3C phase remained in the LPBF-built WC-17Co sample even after heat treatment. The addition of carbon to the WC-17Co powder prevented the formation of the W3Co3C phase in the cemented carbide processed by LPBF and subsequent heat treatments. The addition of carbon to the WC-17Co powder had a slight effect on the hardness of as-fabricated samples, but reduced the hardness of heat-treated samples. The reduced hardness was attributed to the increased volume fractions of the WC and W3Co3C phases.

Microstructure and mechanical properties of WC Ni–Si based cemented carbides developed by powder metallurgy

In this paper the influence of the Ni binder metal and silicon as an additional alloying element on the microstructure and mechanical properties of WC-based cemented carbides processed by conventional powder metallurgy was studied. Microstructural examinations of specimens indicated the presence of a very low and even distributed porosity and the presence of islands of metal binder in the microstructure of the cemented carbides. Furthermore, despite the addition of silicon and carbon in the cemented carbides, it was not observed the presence of small fractions of undissolved SiC and free graphite nodules in their microstructure. Vickers hardness and Flexural strength tests indicated that the cemented carbide WC–Ni–Si with 10 wt.% of binder presented bulk hardness similar to the conventional WC–Co cemented carbides and superior flexure strength and fracture toughness.