热喷涂技术是再制造工程的支撑技术,热喷涂涂层是再制造领域中常见的表面涂覆层,其初始质量和服役寿命为人关注.本文以等离子喷涂为例,研究了与工艺相关的涂层完整性和与服役条件相关的涂层寿命和失效机理.以不同H_2流量、功率和送粉量为条件,研究了工艺参数对涂层孔隙率和微观力学性能的影响.以接触疲劳过程为手段,研究了涂层寿命预测方法和寿命衰退机理.结果表明,工艺参数可以不同程度地影响涂层的结构完整性,通过优化设计可以大幅提高涂层质量;基于大样本空间建立的S-N曲线可以直观预测涂层接触疲劳寿命,机理分析表明,点蚀、剥落和分层失效诱因不尽相同,分别由粗糙接触、近表面缺陷和剪切应力导致.
Thermal spray technique is one of the key techniques in remanufacture engineering. The thermal sprayed coatings are commonly used in remanufacturing applications,their initial performance and service lifetime are critical to the success of remanufacturing.In the present paper, structural integrity,lifetime and failure mechanism of plasma sprayed coatings were investigated.The influences of hydrogen gas flow,spraying powder and powder feed rate on porosity in coatings and their mechanical properties were described.The rolling contact fatigue(RCF) experiment was conducted to develop a method of life time prediction and to reveal the failure mechanism for plasma sprayed coatings.The results show that the structural integrity of coatings can be obviously influenced by spraying process and an optimal design of spraying process can remarkably promote the coating performance. For this purpose,the S-N curve was established based on the large sample space to be used to easily predict coating lifetime.It is found that corrosive pitting,spalling and hierarchical failure are the main failure modes,those results from asperity contact,subsurface defect propagation and shear stress distribution,respectively.