导齿盖腐蚀疲劳裂纹分析

Corrosion Fatigue Crack Analysis of Guide Gear Covers

导齿盖材料为42CrMo中碳调质钢,零件经过渗锌热处理表面防护。该零件在海洋性气候环境下服役过程中发生腐蚀疲劳开裂,裂纹位于其侧面与上表面相交的棱边处,此处为导齿盖暴露面,裂纹源区存在腐蚀坑等较明显的腐蚀特征。采用宏微观形貌分析、能谱分析、化学成分检测、金相组织分析和力学性能分析等手段对导齿盖裂纹进行了检测分析,得出结论:导齿盖服役环境中存在S、Cl等腐蚀性元素介质,对零件的暴露面造成了腐蚀,导齿盖在使用过程中受到交变载荷作用,发生了腐蚀疲劳,超出了材料腐蚀疲劳极限,导齿盖疲劳裂纹不断扩展进而失效。

The material of guide gear cover was made of 42CrMo medium carbon quenched and tempered steel,and the parts were galvanized and heat-treated for surface protection.The corrosion fatigue crack occurred during the service of the part in the marine climate environment,and the crack was located at the edge where the side intersected with the upper surface,where the exposed surface of the guide tooth cover was located,and there were corrosion pits and other obvious corrosion characteristics in the crack source area.The cracks of the guide gear cover were detected and analyzed by means of macro and micro morphology analysis,energy spectrum analysis,chemical composition detection,metallographic structure analysis and mechanical property analysis,and it was concluded that the existence of corrosive elements such as S and Cl in the service environment of the guide gear cover caused corrosion to the exposed surface of the parts,and the corrosion fatigue occurred under the alternating load during the use of the guide gear cover,which exceeded the corrosion fatigue limit of the material,and the fatigue crack of the guide tooth cover continued to expand and then the guide tooth cover failed.