智能传感复合涂层的设计制备与服役行为机理

Surface coatings are usually used to improve the wear-resistance and fatigue resistance of substrate. However, the present wear-resistance and fatigue resistance coatings do not possess dynamic perception and self-monitoring function for the gradual (sudden) change damage in serving process. The objective of the present study is to endow surface coatings with dynamic perception function through innovation design. Smart sensor-based composite coatings which possess not only excellent wear-resistance and fatigue-resistance but also self-perception and self-monitoring are attempted to be prepared by supersonic plasma spraying technique. The piezoelectric ceramic (BaTiO3，PbTiO3，PZT) is firstly sprayed as latent perception function coating onto the substrate, and then FeCrBSi coating is sprayed as wear-resistant and pole coating onto the perceptional function coating. Through the high temperature of spraying process, the piezoeletric material completes the structural phase change. The piezoeletric state can be excited through polarization, which can endow the force-electricity function. The surface wear-resistance coating, perceptional function coating and substrate corporately complete the smart sensor function of "stress…apperceive…translate…feedback" in serving process. Through fatigue damage test and analysis of combined mechanism between coatings' interface, the response mechanism of crack change rule and electric signals can be explored. The relations between electric signals, contact loads and crack state are established, and then the dynamic and real-time monitoring of the fatigue damage process of smart composite coatings can be realized.

表面涂层常用于提高基体的耐磨、抗疲劳性能。但是，目前的耐磨、抗疲劳涂层均不具备服役过程中对渐（突）变损伤的动态感知或自我监测功能。本研究将通过创新设计，赋予表面涂层动态感知功能。拟利用超音速等离子喷涂技术制备"智能传感"复合涂层，既赋予其耐磨抗疲劳性能，又赋予其自我感知，自我监测功能。首先在基体表面喷涂压电陶瓷（BaTiO3、PZT等）作为潜在传感层，然后在传感层上喷涂FeCrBSi等合金材料作为表面耐磨及电极层，通过喷涂过程中高温的环境，完成压电材料的结构性相变，通过极化激发传感层的压电状态，赋予其力-电转变的特殊功能。表面耐磨层、传感层和基体共同作用完成零件服役过程中 "受力…感知…转化…反馈" 的智能传感功能。通过疲劳磨损试验及分析涂层间界面结合机理，探索裂纹变化规律与电信号响应机制，建立电信号、接触载荷和裂纹状态之间的有机联系，实现智能复合涂层对疲劳损伤过程的动态实时准确监测。

压电陶瓷是一种能将机械能和电能相互转换的材料，由于其良好的物理化学性能，广泛应用在振荡器、传感器以及各类水声、超声等方面，遍及日常生活的方方面面。因此，深入开展对等离子喷涂压电陶瓷涂层的研究，将对挖掘其性能、扩展其使用范围有重要的理论意义和实用价值。喷涂技术是制备零件基体表面涂层的关键技术之一。传统对涂层疲劳磨损失效的判断主要是依靠涂层局部断裂后噪声和产生的机械振动等信号的采集分析，这是一种涂层失效后进行的判断，涂层服役过程中，其动态损伤无法实时感知，采用热喷涂技术制备压电涂层对涂层在服役过程中的损伤实施监测是一个新研究方向。本项目主要研究了喷涂方法制备PZT、PZT-PMN以及PbTiO3压电涂层。. 结果表明，通过对PbTiO3、PMN-PZT和PZT陶瓷涂层工艺的探索，得出通过超音速等离子喷涂制备的涂层组织结构致密，孔隙率较低，具有良好的力学性能及一定的介电性能。通过正交试验优化了陶瓷喷涂工艺，超音速等离子喷涂工艺参数对三种压电涂层综合性能的影响主次顺序依次为：Ar气流量>喷涂距离>喷涂电流>喷涂电压，且在该工艺条件下制备的涂层力学性能优于传统等离子喷涂。分析了涂层在极化过程中孔隙影响电子及离子在不同界面的传导，进而使得其本身的介电常数下降，而且涂层中存在空隙时明显阻碍了电子及离子的移动，同样降低了单位体积中电偶极距之和，进而导致介电性质下降，建立了孔隙率影响其介电性能的基本机理。PZT涂层的介电性能稳定，居里温度约为370℃，极化电压为4kV/mm，极化温度为120℃，极化时间为25min，经极化后PZT涂层压电常数d33可达72pC/N。PMN-PZT涂层的介电性能稳定较稳定，随着频率的增加，介电常数值降低，居里温度升高。极化电压为3kV/mm，极化时间为28min,极化温度为140℃为PMN-PZT涂层的最佳极化条件，此时PMN-PZT涂层压电常数d33最高可达27pC/N。材料的自振频率为325 kHz。