合金成分和涂层对WC-Co硬质合金疲劳性能的影响

Effects of Alloy Composition and Coating on Fatigue Properties of WC-Co Cemented Carbide

本文采用三点弯曲疲劳试验,研究了Cr_(3)C_(2)/TaC添加剂、原料WC粒度、CVD涂层处理对WC-Co硬质合金疲劳性能的影响,通过光学显微镜、超景深显微镜、扫描电子显微镜研究了硬质合金疲劳断口形貌和失效机理。实验结果表明:采用Cr_(3)C_(2)添加剂合金基体疲劳性能优于TaC添加剂合金。采用TaC为添加剂时,粗晶粒WC合金疲劳性能优于细晶粒WC合金。采用Cr_(3)C_(2)为添加剂时,WC原料粒度对合金疲劳性能影响不明显。合金基体试样疲劳断口呈凹凸不平状,裂纹源起源于近表层的基体组织缺陷。在硬质合金基体外涂覆CVD涂层会导致其疲劳性能显著下降,且疲劳断口呈平整状,裂纹起源于涂层,裂纹扩展由涂层向基体扩展。在硬质合金外涂覆CVD涂层不会影响基底材料的断口断裂形式,断口断裂形式主要以沿晶断裂为主。

In this paper,the effects of Cr_(3)C_(2)/TaC additive,the particle size of raw material WC and chemical vapor deposition(CVD)coating treatment on the fatigue properties of WC-Co cemented carbide were studied by a three-point bending fatigue test.The fatigue fracture morphology and failure mechanism of the cemented carbide were investigated by an optical microscope,a super-depth-of-field microscope and a scanning electron microscope.The experimental results show that the fatigue properties of the alloy matrix with the Cr_(3)C_(2)additive are better than those with the TaC additive.When TaC is used as an additive,the fatigue properties of coarse-grained WC alloys are better than those of fine-grained WC alloys.When Cr_(3)C_(2)is used as an additive,the particle size of raw material WC does not significantly influence the fatigue properties of the alloy.The fatigue fracture of the alloy matrix sample is uneven,and the crack originates from the matrix defects near the surface layer.A CVD coating on the cemented carbide substrate can significantly reduce its fatigue properties,and the fatigue fracture is flat.The crack originates from the coating and propagates from the coating to the substrate.The CVD coating on the cemented carbide does not affect the fracture form of the substrate,with intergranular fracture dominating as the fracture form.