微缺陷对热喷涂涂层接触疲劳性能的影响

采用超音速等离子喷涂设备在45号钢基体上制备了三种含有不同微缺陷的NiCrBSi合金涂层。使用球盘式接触疲劳实验机对涂层的接触疲劳性能进行了测试,建立了Weibull失效概率图;使用扫描电子显微镜对涂层的微观结构和失效形貌进行了表征;比较了三种涂层的接触疲劳寿命及涂层的主要疲劳失效模式。结果表明,涂层内的微缺陷主要由微孔隙和微裂纹构成,涂层接触疲劳寿命的长短与这些微缺陷含量的多少成反比,涂层的孔隙率为2.5%,1.3%和2.1%,对应的接触疲劳寿命分别为7.77×105,8.99×105,7.81×105周次。同时,涂层微缺陷含量较少时涂层的失效模式主要以剥落失效为主;涂层微缺陷含量较多、结合强度较差时主要以分层失效为主;涂层内存在较大的孔隙可致使涂层的提早失效,同时涂层表面磨损失效的概率增加。

Influence of Microdefect on Rolling Contact Fatigue Performance of Thermal Spraying Coating

Three kinds of NiCrBSi alloy coatings with different micro-defect types were sprayed on 1045 steel.Rolling contact fatigue(RCF) life of the coating was investigated using a ball-on-disc tester and the map of Weibull distribution failure probability was plotted.SEM was adopted to observe the microstructure and fatigue trace of the coatings.In addition,the contact fatigue life and main failure mode of different coatings were compared and the failure mechanism was investigated as well.The results showed that micro-defects in the coating were mainly composed of micro-pores and micro-cracks.Contact fatigue life of the coating was in inverse proportion to the content of micro-defects.Contact fatigue life of coating were 7.77×105,8.99×105,7.81×105 cycle,with the porosity of the coatings 2.5%,1.3% and 2.1%,respectively.It also can be seen that,when the content of micro-defects was low,the main failure mode of the coating was spalling failure while with the increasing of micro-defects and the decreasing of combined strength the main failure mode changed into the interfacial delimitation failure.The large pores existing in the coatings may result in the early failure of the coating,at the same time increase the wear failure probability.