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为了提高钢制零件的抗腐蚀性能,表面镀镉防护工艺已在航空工业中广泛应用。然而镉是一种低熔点金属,它的扩散激活能很低(镉在钢的表面扩散活化能为13500卡)。当温度超过镉熔点(322℃)的四分之三时,镉元素就会在与之紧密接触的部位以自扩散的方式渗入钢件晶界,导致钢件脆化。本文针对某型机连接螺栓发生的多次断裂事故,用金相、电镜等手段进行分析验证,确认系固体镉脆所致,说明选用镀镉防护措施时必须十分谨慎,否则可能带来灾难性破坏。
In order to improve the corrosion resistance of steel parts, cadmium plating surface protection technology has been widely used in the aviation industry. Cadmium, however, is a low melting point metal that has a low diffusion activation energy (the activation energy of cadmium diffusion on the steel surface is 13,500 calories). When the temperature exceeds three-fourths of the melting point of cadmium (322 ° C), cadmium infiltrated into the steel grain boundaries in a self-diffusing manner at the close contact parts, causing the steel to embrittle. In this paper, a number of machine-made bolts fracture occurred several times, by means of metallographic, electron microscopy and other means of analysis to verify the Department of cadmium solid caused by the Department of cadmium, indicating the choice of cadmium protective measures must be very cautious, otherwise it may bring catastrophic damage.