涡轮叶片热障涂层残余应力的光激发荧光压电光谱全域检测系统研制

Thermal barrier coatings (TBCs) represent the most feasible engineering solution in the enhancement of the operating temperature of gas turbine engines. The development of scientific based techniques capable of evaluating manufacturing quality and operating conditions of TBCs has always been a key issue in the aero-engine industry. During operation at elevated temperatures, oxidation takes place at the interface between the ceramic top coat and the intermetallic bond coat and a thermally grown oxide (TGO) layer is formed. Due to the mismatch in thermal expansion coefficients, residual stresses developed in the TGO during thermal cycling, which eventually lead to spallation failure of TBCs. Currently, photoluminescence piezospectroscopy (PLPS), despite being the most academically proven nondestructive technique for the measurement of TGO stress, is unable to be carried out with fast and accuracy on large curved surfaces of typical gas turbine blades. With this key technical deficiency in-mind, the proposed application intends to develop a new type of “full-area scanning photoluminescence piezo-spectroscopy system for TBCs residual stress measurement on curved surface of turbine blades.” Approaches involve interlinking mechanical 4-axis auto-focusing stages with optical auto-focus assisting module, constructing stress maps from measurement results, and carrying out data analysis; all with an ultimate goal of realizing a new industrial defect detection and lifetime prediction system for TBCs.

热障涂层（TBCs）作为目前提高航空发动机服役温度最切实可行的方法，其制备质量和服役状况的科学检测是航空领域亟需解决的关键问题。热障涂层在服役过程中，高温氧化发生在陶瓷层和粘结层的界面处并形成氧化层(TGO)。TGO生长所致的热生长应力以及TBCs各层材料热力学系数差异引起的热失配应力都集中发生于TGO界面处，成为导致TBCs界面失效的关键因素。目前，光激发荧光压电光谱（PLPS）法是TGO残余应力检测最为科学有效的无损检测方法，但是该检测方法面对涡轮叶片这类大面积曲面样品时无法进行快速可靠的全域应力测试，数个测试点的应力状况难以描述整个涡轮叶片的服役状况。基于此，本项目致力于研制一种“涡轮叶片热障涂层残余应力的光激发荧光压电光谱全域检测系统”，通过光学对焦与4轴机械载台的联动配合，完成大面积曲面试样的应力测试和云图成像，结合数据分析，最终实现热障涂层的质量无损检测与寿命预测。

热障涂层(TBCs)是高温部件上用于提供基底热防护。涂层在服役过程中，热失配应力和热生长应力常集中于热生长氧化物层（TGO）处，热障涂层内应力的积累为裂纹的产生，扩展与合并提供了驱动力，造成涂层失效剥落，即TGO层成为热障涂层体系最易失效的区域。因此，TGO残余应力分布状况是判断涂层状态的重要指标。研究热障涂层TGO层应力状态较为成熟的方法是光激发荧光压电光谱(PLPS)法，但现阶段TGO残余应力PLPS检测设备仍依赖以机械载台进行对焦，以机械方式对大曲面复杂结构叶片进行检测将变得极为耗时，无法对叶片进行全域范围的检测能力。本计画致力于研制一套PLPS全域检测设备，用于残余应力的采集与分析。该设计通过光学辅助对焦与四轴载台相结合的方法，对涂层进行全域残余应力检测与分析。.本计画：.1. 探究了文献中PLSP检测设备在涂层样品检测所需克服的科研等工程性问题，结合相关光学部件等研制思路，针对关键性工程问题，提出PLPS全域检测的设计方案。.2. 基于Blender软件，对PLPS全域检测设备开展模拟验证，通过模拟全域检测设备的工作方式，确定最佳工作方案。并在Blender中对PLPS全域检测设备整体工作流程进行模拟，探究设备参数对检测结果的影响。.3. 通过EB-PVD制备平面和曲面涂层样品，结合SEM设备探究基底曲率对柱状晶生长方向的影响，并通过PLPS全域检测系统，对样品TGO残余应力进行检测分析及分布云图的绘制进行验证。