注塑机过胶圈在使用中因磨损失去密封性而失效。采用电镜及光镜对失效件进行了检验。结果表明 ,注塑机过胶圈失效属于接触疲劳破坏。过胶圈表层存在的严重网络状氮化物 ,在工作压力下易开裂而成为裂源 ,加之对胶圈截面硬度梯度大、硬化层薄和材料的疲劳强度较低 ,最终导致其早期疲劳失效。 Plastic injection molding machine ring in use due to wear and tear loss of sealing failure. The failed parts were tested by electron microscope and light microscope. The results show that the failure of the plastic injection molding machine belongs to contact fatigue failure. The severe network nitrides that exist on the surface of the apron are apt to crack under the working pressure and become the source of cracks. In addition, the hardness gradient of the cross section of the apron is large, the thickness of the hardened layer is thin and the fatigue strength of the material is low, leading to early fatigue failure.