发动机零件腐蚀后表面麻坑缺陷的分析

一个发动机零件在钎焊后进行腐蚀工序时基体材料非钎焊部位表面局部出现麻坑缺陷，为了分析缺陷产生的原因，进行了缺陷再现模拟试验。通过对缺陷的观察、金相检查，电镜检查，能谱检查和分析，认为钎焊时在焊缝正面熔化后多余的钎料在金属基体表面流淌铺展，在毛细作用下放置在耐火砖上钎焊的零件其焊缝反面的基体表面有熔化的钎料铺展开来。与此同时，覆盖的钎料又通过毛细作用渗入到金属基体的表面层的晶界内，破坏了金属基体耐HNO3等强氧化性溶液的腐蚀能力，使零件产生腐蚀麻坑缺陷。由此对钎焊夹具进行了改进，解决了零件腐蚀后表面麻坑缺陷的问题。

Pit Defect Analysis on Surface of Part in an Engine after Corrosion

On a part of engine, pit defect was found locally on the surface of non-brazing position of metal base after brazed and corrosion. The analog test of defect recurrence was taken in order to analyze the reason of defect. It was found that extra melting solder spread on the face of weld of metal base while brazing, and by capillary action, there is melting solder spread on the back of weld of metal base which was placed on the fireclay brick. At the same time, the laying solder infiltrated the grain boundary of the metal base surface by capillary action, which damaged the corrosion resistant of strong oxidizing liquor such as HNO3 on metal base and arose pit defect by corrosion. The improved methods of the clamp were also proposed to avoid similar events.