基于纳米压入原理的亚稳态涂层残余应力定量检测基础研究

It is well known that the residual stress has significant influences on the service life and reliability of remanufactured components. Recently, residual stress determination using the methodologies based on nano indentation technique has attracted extensive attentions, but no breakthrough has been achieved in the key theory. One reason is that the real contact area of indentation can't be accurately obtained for the significantly deformation of the metastable coating material around the indentation. Another reason is that the reference samples with absolutely no stress are needed in the existing residual stress calculation theory models, but they can't be obtained in practical engineering application. Therefore, the nano mechanical integrated test system with the nano indentation and the atomic force microscope is used as the experimental platform in this research. Firstly, it will correct the existing classic model on the indentation contact area by extracting and calculating the real area of the bulging deformation around indentation on the micro/nano scale. Secondly, it will realize the precise loading of the tensile or compressive stress by designing the quantitative and controlled device instead of the dependence on the stress-free reference sample. Based on the results of the study, the main aim is to establish the mathematical mapping model between the real indentation contact area and the residual stress in the metastable remanufacturing coating and to realize the quantitative determination for the residual stress.

机械装备再制造工程中所涉及的各类涂层，由于残余应力的存在，显著影响其使用寿命和可靠性。纳米压入技术被引入对典型亚稳态再制造涂层残余应力的检测，但关键的理论问题尚未突破：一方面对于压痕周围有显著凸起变形的亚稳态非弹性材料，其压痕的真实接触面积无法准确获取；另一方面目前计算残余应力的理论模型都需要无应力的参考试样，但实际工程中却无法得到绝对无应力的试样。因此，本课题以集纳米压痕仪、原子力显微镜于一体的纳米力学综合测试系统为实验平台，首先通过准确提取与计算压痕四周微纳米量级的凸起变形面积，实现对现有经典压痕接触面积模型的修正；其次通过创新设计一种定量可控的等双轴应力施加与测量装置，实现拉应力或压应力的精确施加，取代对无应力参考试样的依赖。基于上述研究结果，建立起典型亚稳态非弹性再制造涂层的压痕真实接触面积与涂层残余应力之间的映射数学模型，实现对再制造涂层残余应力的定量检测。

零件再制造后形成的涂层通常为二元多相亚稳体系，其表界面具有独特的材料结构和物理化学特征，且在制备过程中容易累积残余应力。涂层中的残余应力对再制造零件表界面服役特性具有极大的影响，会显著降低整个再制造产品的使用寿命和可靠性。因此，再制造涂层的残余应力已成为涂层应用及安全服役过程中一个不容忽视的问题。本项目基于亚稳态涂层残余应力的产生过程的复杂性及多变性，系统地研究了几类亚稳态涂层的残余应力。项目按照预期研究计划执行，研究过程顺利，已经完成的主要研究内容有：开展了几类典型再制造涂层设计与制备工艺的研究，对涂层进行了微观结构与性能表征，为分析亚稳态涂层的表界面结构特征及结构演化对残余应力的影响提供了基础数据和理论支撑；根据典型亚稳态涂层残余应力的测试以及组织结构表征结果，重点研究了温度、稀土添加以及第二相添加等对亚稳态涂层表界面特征的影响，明确结构设计与服役环境对亚稳态涂层残余应力的影响，阐明了残余应力的变化对亚稳态涂层耐磨性的作用规律，为多元多层复杂涂层的设计提供理论依据；利用自主设计的新型等双轴残余应力施加装置对亚稳态涂层施加不同状态和大小的残余应力进行纳米压痕实验，精准计算压痕凸起变形面积，对压痕真实接触面积模型进行修正，完成压痕的真实接触面积与残余应力之间的映射理论模型的建立，并利用X 射线衍射法检测残余应力，辅助验证并完善修正后的残余应力理论模型；借助有限元软件平台和分子动力学软件，模拟纳米压痕的实际过程中亚稳态涂层内部的应力分布情况以及纳米压痕加载/卸载各阶段的涂层变形情况，为亚稳态涂层的制备及应用过程中的应力控制提供了理论基础和实验依据。同时，基于上述研究成果申请国家发明专利7项，授权3项，授权实用新型专利1项，完成相关学术论文30余篇，其中已发表SCI论文17篇、EI论文7篇、送审6篇。