喷涂层接触疲劳损伤的声发射研究

用超音速等离子喷涂设备在45钢基体上制备了铁基合金涂层。以球盘式疲劳试验机为平台,研究了涂层的接触疲劳损伤行为,探测并分析了涂层在不同应力水平下疲劳损伤的声发射反馈信号。结果表明,涂层的接触疲劳损伤过程主要包括弹塑性变形、裂纹萌生和缓慢扩展、裂纹亚临界扩展、裂纹失稳扩展4个阶段。裂纹萌生和缓慢扩展阶段是决定疲劳寿命长短的主要阶段。接触应力越大,裂纹亚临界扩展时间和失稳扩展时间越短。涂层的最终失效模式可以根据裂纹失稳扩展阶段声发射幅值的最大值来判断,发生点蚀失效时幅值最大值约为82.4 dB,剥落失效时幅值最大值约为90.2 dB,分层失效时幅值最大值约为91.3 dB。

Study on contact fatigue damage of sprayed coatings by acoustic emission

Fe-based alloy coatings were prepared on 45 steel by a supersonic plasma spraying device.The contact fatigue damage behavior of the coatings was investigated on a ball-on-disk fatigue tester.The feedback signals of acoustic emission in the process of fatigue damage of the coatings under different stress levels were detected and analyzed.Results show that contact fatigue damage process of the coatings is composed of four stages,which are elastic and plastic deformation,crack initiation and slow propagation,sub-critical crack growth and crack unstable growing.The fatigue life of the coatings mainly depends on the crack initiation and slow propagation.The higher the contact stress,the less the life of sub-critical crack growth and crack unstable growth.The final failure mode of the coatings can be characterized by the peak value of acoustic emission amplitude in the stage of crack unstable growth.The peak values of acoustic emission amplitude are about 82.4 dB for pitting failure,90.2 dB for spalling off,and 91.3 dB for delamination failure of the coatings.