Experimental Study to Assess Fracture Toughness in SPS Sintered WC–10% Co Hardmetal by Modifying the Palmqvist Test

Abstract

Hardmetals are widely used as cutting, machining, and drilling tools for rocks due to their excellent properties of hardness, fracture toughness, and wear resistance over a wide temperature range. This study proposed to evaluate the fracture toughness of WC–10% Co carbide, sintered via spark plasma sintering—SPS, through the Vickers indentation measures, using a modification of the Palmqvist test, which is widely used to assess the toughness of cemented carbides, and to compare this result with the results of six different conventional models: Shetty, Niihara, Laugier, ISO 28079, Hanyaloglu, and Lankford. The model to assess the toughness proposed in this study showed similarity with the Palmqvist test. However, there were considerable differences in the KIC values for the different models, such as 13.36 MPa·m1/2 and 4.44 MPa·m1/2 for the same application load. Comparing the values of the conventional fracture toughness and proposed fracture toughness, the greatest difference between the fracture toughness values was found in the Lankford equation, which varied by 14.74%. The Hanyaloglu equation showed a smaller difference between the fracture toughness values, with a greater variation of 3.61% and lower variation of 1.54%. Adequate results of hardness were obtained, with a maximum of 20.93 ± 0.25 GPa, minimum of 15.76 ± 0.63 GPa, and densification of 99.14 ± 0.47 g/cm3.