In this study, we prepared WC-CoNiFe and WC-Co with different grain sizes by sintering-hot isostatic pressing (SHIP) and evaluated their fracture behavior. The results showed that WC-CoNiFe has a higher fracture toughness (between 13.16 and 17.82 MPam^1/2) than WC-Co (between12.08 and 16.21MPam^1/2). Moreover, fracture toughness and fatigue crack growth (FCG) were closely related to the corresponding microstructural characteristics. The fracture toughness increased via ductile ligament bridging and crack deflection as the mean free path of the binder phase (λ_Co) increased, or the contiguity of the carbide phase (C_WC) decreased. The fatigue fracture mode showed a transition from a cleavage-like brittle fracture to a ductile dimple-like fracture. The fatigue sensitivity of cemented carbides was positively related to the fracture toughness. As the fracture toughness increased, cemented carbides exhibited a transition from ceramic-like material to metal-like material. Considering two important controlling parameters of FCG behavior, the effect of maximum stress intensity factor (K_max) on FCG was dominant compared to the stress intensity factor range (∆K). However, the difference in the relative influence of these two parameters diminished as the fracture toughness increased. Moreover, with the rise in K_max value, we defined three stages of the FCG process: crack initiation, stable crack growth, and unstable crack growth. The results suggest that CoNiFe medium entropy alloy is a promising material for application as a binder phase of cemented carbides with high toughness.

在这项研究中，我们通过烧结热等静压（SHIP）制备了具有不同晶粒尺寸的WC-CoNiFe和WC-Co，并评估了它们的断裂行为。结果表明，WC-CoNiFe的断裂韧性（在13.16和17.82 MPam ^1/2之间）比WC-Co（在12.08和16.21MPam ^1/2之间）更高。此外，断裂韧性和疲劳裂纹扩展（FCG）与相应的显微组织特征密切相关。断裂韧性增加经由延性韧带桥接和裂纹偏转作为粘合剂相（的平均自由路径λ_有限公司）增加，或者碳化物相的邻接（Ç _WC）减少。疲劳断裂模式显示了从乳状的脆性断裂到延性的酒窝状的断裂的转变。硬质合金的疲劳敏感性与断裂韧性呈正相关。随着断裂韧性的增加，硬质合金表现出从类陶瓷材料过渡到类金属材料的转变。考虑到FCG行为的两个重要控制参数，与应力强度因子范围（∆K）相比，最大应力强度因子（K _max）对FCG的影响占主导地位。但是，随着断裂韧性的增加，这两个参数的相对影响的差异减小了。而且，随着K _max的增加值，我们定义了FCG过程的三个阶段：裂纹萌生，稳定的裂纹扩展和不稳定的裂纹扩展。结果表明，CoNiFe中熵合金是一种有前途的材料，可用作具有高韧性的硬质合金的粘结相。