重熔涂层的组织结构演变及其协同性疲劳失效机制和寿命预测研究

In the light of the disadvantages of plasma spray coating, such as poor combination between coating and substrate, internal porosity and other defects, remelting treatment can solve these problems to a great extent and improve the contact fatigue resistance of plasma spray coating. But at present the study of contact fatigue performance of remelted coating is still not much and carried out under pure rolling conditions, however the actual service condition of remelted coating is often rolling sliding contact state, whose failure mode is actually contact fatigue under the synergistic effect of wear, and its service life is determined by contact fatigue under the synergistic effect of wear. This study will accurately simulate different rolling sliding contact state on contact fatigue/wear multi-function tester by changing the slip ratio. The experimental process will be dynamically monitored with acoustic emission monitor. The influence of remelting treatment on structure evolution and mechanical properties of plasma spray coating will be studied, the interface characteristics of re melting coating / substrate will be studied, the fatigue failure mechanism of the remelted coating under the synergistic effect of wear will be revealed, the feedback law of the typical characteristic parameters of acoustic emission signals to failure process of the remelted coating will be explored and the prediction model of fatigue life under the synergistic effect of wear of the remelted coating will be built. Eventually the accurate prediction of the remelted coating’s synergistic fatigue life which is more close to actual working conditions will be realized. This study has important scientific significance and value of engineering application.

等离子喷涂层与基体结合较差，内部含有孔隙、裂纹等缺陷，而进行重熔处理可在很大程度上解决这些问题，提高涂层的耐接触疲劳性能。但是目前针对重熔涂层接触疲劳性能的研究还很少且是在“纯滚动”条件下进行的，而重熔涂层实际的服役工况经常是“滚滑”接触状态，此时的失效模式其实为磨损协同接触疲劳的关系，其服役寿命也是由磨损协同接触疲劳而决定。本研究拟基于接触疲劳/磨损多功能试验机，通过改变滑差率，以声发射监测仪为动态监测手段，准确模拟不同“滚滑”接触状态，研究重熔处理对等离子喷涂层组织结构演变和力学性能的影响规律，研究重熔涂层/基体间的界面特性，揭示重熔涂层在磨损协同作用下的疲劳失效机制，探索典型声发射信号特征参量对其失效过程的反馈规律，建立表征重熔涂层在磨损协同作用下的疲劳寿命演变规律的预测模型，最终实现对更为接近实际工况的重熔涂层协同性疲劳寿命的准确预测，本课题的研究具有重要的科学意义和工程应用价值。

等离子喷涂层内部含有孔隙、裂纹等缺陷，与基体结合较差，而进行重熔处理可在很大程度上解决这些问题，提高涂层的接触疲劳性能。但是目前针对重熔涂层接触疲劳性能的研究还不多且是在“纯滚动”条件下进行的，而重熔涂层实际的服役工况经常是“滚/滑”接触状态，此时的失效模式其实为磨损协同接触疲劳的关系，其服役寿命也是由磨损协同接触疲劳而决定。本课题研究中设计了几种粉末成分，采用等离子喷涂技术在45钢表面分别制备了Ni基合金涂层、Fe基合金涂层和NiCr-Cr3C2金属陶瓷涂层，然后分别采用几种重熔工艺（钨极氩弧、感应加热和火焰）对它们进行了重熔处理，在此基础上，研究了重熔处理对等离子喷涂层组织结构和性能的影响，重点研究了重熔涂层在磨损协同作用下的疲劳寿命和疲劳失效机制。此外，还对等离子喷涂8YSZ和La2Zr2O7/8YSZ热障涂层激光重熔前后的高温性能和失效机理进行了探索研究。.结果表明，(1) 重熔处理能有效地去除等离子喷涂Ni基合金涂层、Fe基合金涂层以及NiCr-Cr3C2金属陶瓷涂层中的氧化夹杂、孔隙和微裂纹等微缺陷，使涂层的孔隙率显著降低甚至基本消除，并使得涂层与基体之间由机械结合变为冶金结合；重熔后涂层的显微硬度、弹性模量和断裂韧性明显提高。(2)在摩擦磨损试验中，重熔涂层表现出了优于喷涂层的耐磨性能，因此利用喷涂+重熔技术在钢表面制备涂层可有效提高工件的耐磨性。（3）在不同的滑差率下，几种重熔涂层的滚/滑接触疲劳性能均远优于相应的喷涂层，重熔涂层的疲劳寿命大幅度延长，且寿命分散度也明显降低；喷涂层的滚/滑接触疲劳失效形式主要为界面分层，而重熔涂层的主要为点蚀和剥落。此外，获得了喷涂层和重熔涂层在滚/滑接触疲劳条件下的p-N曲线图，可以用来预测两种涂层在不同接触疲劳寿命值对应的失效概率。（4）激光重熔处理能有效提高等离子喷涂8YSZ和La2Zr2O7 / 8YSZ 热障涂层的高温性能。因此，通过喷涂+重熔工艺可以获得综合性能优异的重熔涂层，本研究具有一定的科学意义和工程应用价值。