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硬质合金的平均晶粒度影响着合金的使用性能,而硬质相粒度分布对合金性能的影响较少报导.本文选用经典工艺制备的4批粘结相质量分数6％、平均晶粒度为1.6 μm、不同WC晶粒离散度试样,1批网状合金试样,l批粘结相质量分数8％、平均晶粒度为1.6 μm、WC晶粒高离散度试样,通过Palmqvist压痕实验测定其断裂韧性来研究WC晶粒离散度对硬质合金断裂韧性的影响.结果表明,经典试样WC晶粒离散系数由0.425 8增大至0.533 7时,断裂韧性由15.7 MPa·m1/2降至11.6 MPa· m1/2,维氏硬度基本保持1 420 HV30左右;粘结相含量、平均晶粒度及维氏硬度相同的网状结构硬质合金,其WC离散系数为0.653 6时,Palmqvist压痕断裂韧性高达16.0 MPa·m1/2;粘结相质量分数为8％的试样,其WC离散系数为0.612 1,维氏硬度为1 350 HV30,断裂韧性仅为12.5 MPa·m1/2.离散度小的硬质相分布及特别的微观结构设计都可以在不降低硬度的情况下提升合金的韧性.

The properties of cemented carbide are affected by the average grain size,but the research reports concerning the effect of the distribution of hard phase particles on the properties of cemented carbide are few.For this purpose the fracture toughness of cemented carbide samples was determined by Palmqvist method,and the effect of the dispersion of WC grain on the fracture toughness of the cemented carbide was investigated.Wherein four batches of samples produced by traditional process comprise Co content of 6wt％ with average WC grain size of 1.6 μm and different dispersion of WC grain,respectively;a batch of sample has cellular structure;another batch of sample comprises Co content of 8wt％ with average WC grain size of 1.6 μm and higher dispersion of WC grain.The result shows that when the dispersion of WC grain in the traditional grade cemented carbide increases from 0.425 8 to 0.533 7,the fracture toughness decreases from 15.7 MPa·m1/2 to 11.6 MPa·m1/2,while the hardness remains unchanged at about 1 410 HV30.For the cellular sample with the same Co content,average gain size and hardness as above,the dispersion of WC grain is 0.653 6,and the fracture toughness is up to 16.07 MPa ·m~ In the case of the sample with Co content of 8wt％,the dispersion of WC grain is 0.612 1,the hardness is 1 350 HV30,while the fracture toughness is only 12.5 MPa·m1/2.The result indicates that lower dispersion of hard phase grain and special microstructure can enhance the fracture toughness of the cemented carbide without loss of hardness.