等离子喷涂层的磨损/疲劳竞争性寿命演变规律研究

Plasma spray coatings are commonly used to resist wear and contact fatigue failure due to the high hardness and bonding strength. When the contact conditions of dual faces are "pure sliding" and "pure rolling", the corresponding failure modes are "wear" or "contact fatigue". Traditionally, the wear life and contact fatigue life of coatings are often studied individually, but sliding and rolling often coexist in actual serving condition, and the failure mode simultaneously contains wear and contact fatigue. Therefore, the service life is a kind of competitive life, which can be obtained by the competition of wear life and contact fatigue life. The present study will accurately simulate a series of contact conditions including "pure rolling", "rolling+sliding" and "pure sliding" through changing the slip ratio on a late-model wear/contact fatigue competitive life tester. The characteristic parameters of acoustic emission signals which can suitably characterize the failure process of wear and contact fatigue will be investigated; the feedback of typical characteristic parameters of acoustic emission signals to the competitive failure process of wear and contact fatigue will be explored; the competitive failure mechanism of coatings under the associated effects of high free energy and various interfaces will be revealed; the competitive life estimation model of coatings will be established. The results will accurately estimate the competitive life of coatings under the contact condition of "rolling+sliding".

等离子喷涂层因其高硬度和高结合强度，常用于抵抗磨损及接触疲劳失效。当涂层所处的接触状态分别为"纯滑动"和"纯滚动"时，其对应的主要失效模式分别为"磨损"和"接触疲劳"，传统的研究通常是对涂层的磨损寿命和接触疲劳寿命进行孤立研究，而涂层服役的实际工况通常是"滚动+滑动"共存的接触状态，失效模式为磨损与接触疲劳共存并相互竞争的关系，其服役寿命也是由磨损寿命和接触疲劳寿命关联竞争而得到的竞争性寿命。本研究拟基于新型磨损/接触疲劳竞争性寿命试验机，通过改变滑差率，准确模拟"纯滚动"、"滚动+滑动"和"纯滑动"几种接触状态，研究适合表征涂层磨损及接触疲劳失效过程的声发射信号特征参量，探索典型声发射信号特征参量与涂层磨损和接触疲劳竞争性失效过程的反馈规律，揭示涂层在高自由能和多界面性关联作用下的竞争性失效机理，建立涂层的竞争性寿命预测模型，最终实现对"滚动+滑动"接触状态下涂层竞争性寿命的准确预测。

等离子喷涂层因其高硬度和高结合强度，常用于抵抗磨损及接触疲劳失效。针对涂层“滚动+滑动”接触状态下的实际服役工况，本课题主要采用等离子喷涂设备在调质45#钢基体上分别制备了纳米Al2O3-TiO2复合陶瓷涂层、NiCr-Cr3C2金属陶瓷涂层以及FeCrBSi铁基合金涂层、NiCrBSi镍基合金涂层，通过正交试验或者均匀化试验得到了每种涂层的最优喷涂工艺参数；随后采用多种检测手段和分析方法表征了涂层的微观组织、力学性能、摩擦学性能；利用研制的RM-1型接触疲劳试验机，结合声发射监测仪系统研究了涂层在不同滚动/滑动接触状态下的竞争性失效行为和寿命演变规律。此外，对等离子喷涂层表面自由能与摩擦学及接触疲劳性能的影响进行初步探索，并探索了火焰重熔和热等静压后处理对喷涂层组织结构和疲劳/磨损竞争性失效机制的影响。.结果表明，（1）喷涂参数对等离子喷涂层的组织、力学性能和摩擦学性能具有显著影响，不同涂层组份表现出不同的组织结构和性能；（2）RM-1型对辊式接触疲劳/磨损多功能试验机能够实现对“纯滚动”、“滚动/滑动共存”和“纯滑动”等接触状态的模拟，因此可以作为对涂层耐磨性能和接触疲劳性能进行综合评价的综合实验平台；（3）滑差率对涂层的接触疲劳性能有影响，在“滚动/滑动”接触状态下，涂层的竞争性寿命服从Weibull分布，随着滑差率的增加，涂层的疲劳寿命下降，寿命的离散度增加，并且涂层在不同滑差率下表现出不同的失效形式；（4）接触应力也对涂层的接触疲劳性能有影响，随着接触应力的增加，涂层的平均寿命减小；（5）不同的涂层组份具有不同的表面自由能，涂层的表面自由能与涂层的摩擦学性能和接触疲劳寿命有着某种对应关系；（6）火焰重熔和热等静压处理可以显著改善涂层的内部组织和提高力学性能，并可进一步改善涂层的耐磨性和接触疲劳性能。