Mechanical evaluation of WC-Co materials with varying microstructures

• Published in: International journal of refractory metals & hard materials 2022-04, Vol.104 (C), p.105809, Article 105809
• Main Authors: Pittari, John J., Swab, Jeffrey J., Wright, Jared, Atwater, Katherine
• Format: Article
• Language: English
• Subjects: Cobalt; Constraining; Dependent variables; Flexing; Flexural strength; Flexure strength; Fractography; Fracture toughness; Grain size; Hardness; Inclusions; Indentation; MATERIALS SCIENCE; Mechanical properties; Metallurgy & Metallurgical Engineering; Milling (machining); Surface finishing; Tensile strength; Tungsten carbide; Uniaxial tensile strength; Weibull analysis
• ISSN: 0263-4368; 2213-3917
• DOI: 10.1016/j.ijrmhm.2022.105809

Tungsten carbide‑cobalt materials are useful in a variety of extreme applications due to a desirable blend of properties, yet the technology has not significantly changed since their initial development in the 1920s. The mechanical properties of this class of materials is highly dependent on two variables, the size of the tungsten carbide grains, and the amount of binder phase present in the final body. In this study, the amount of binder phase is isolated across three commercial materials from the same manufacturer with three different grain sizes to investigate the effect on mechanical properties. The mechanical properties investigated are indentation hardness, flexure and tensile strength, as well as fracture toughness. In general, an increase in hardness and tensile strength with decreasing grain size was observed, while the fracture toughness showed the opposite trend with toughness increasing with increasing grain size. The flexure strength results did not show a correlation to grain size. Fractographic analysis identified the dominant strength-limiting flaw for each sample, which largely were in the form of porosity. Other flaws types, such as inclusions from the milling process, clusters of large grains, and machining cracks from the surface finishing process, were also identified. Weibull analysis was performed and deemed appropriate for analysis of these materials, but strength-size scaling was not conducted due to the variability in the strength-limiting feature between the different specimen geometries. •Mechanical properties of WC with 12% Co but different microstructures•Hardness and uniaxial tensile strength increased with decreasing grain size•Fracture toughness increased with increasing grain size•Flexure strength did not correlate with grain size•Fractography showed significant variations in the strength-limiting features