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本文研究了钴含量7～30％(体积)、WC晶粒度0.5～3.5μm范围内常规WC-Co硬质合金组织结构对断裂韧性和断裂的影响。采用缺口和裂纹两种试样测定合金的断裂韧性;用体视金相学方法铡定合金的显微组织结构参数,并统计了断裂模式的分布。结果表明:合金的断裂韧性主要取决于钴的含量、分布及钴相平均自由程。根据断裂过程分析,导出裂纹扩展能量释放率与组织结构间的关系式为:G_(IC)=(0.417～0.457)σ_sλ。该类合金脆断的主要微观原因是WC/WC型晶间开裂和WC晶粒穿晶断裂。断口表面,WC/WC型晶间开裂分数与组织结构间的关系为:(F)_(WC/WC)=γ(1-V_(Co))~2/D_(WC)。试验表明,合金的断裂韧性采用缺口试样进行测定是可行的,缺口和裂纹两种试样能量释放率间的关系为:G_(IC(ρ))=G_(IC)+2.1ρ。
In this paper, the effect of conventional WC-Co cemented carbide structure on fracture toughness and fracture in the range of 7-30% of cobalt content and 0.5-3.5μm of WC grain size was studied. The fracture toughness of the alloy was measured by using both notch and crack specimens. The microstructural parameters of the alloy were determined by stereolithography and the distribution of fracture modes was calculated. The results show that the fracture toughness of the alloy mainly depends on the cobalt content, the distribution and the mean free path of cobalt phase. According to the analysis of the fracture process, the relationship between the energy release rate of the crack propagation and the structure of the structure is derived as follows: G IC = 0.417-0.457 σ sλ. The main microscopic reasons for the brittle fracture of these alloys are WC / WC type intergranular cracking and WC grain transgranular fracture. The relationship between the fracture surface of WC / WC type and the microstructure of the fracture surface is: (F) _ (WC / WC) = γ (1-V_ (Co)) ~ 2 / D_ (WC). The experimental results show that the fracture toughness of the alloy is feasible to measure with the notched specimen. The relationship between the energy release rate of the two specimens is as follows: G (IC (ρ)) = G IC + 2.1ρ.