Periodic Cracking of Thermal Barrier Coatings for Improved Interfactial Thermal Fracture Resistanace: Experiments and Analysis

9908187 Kokini陶瓷热障涂层在高温应用中，如航空航天和飞机发动机、燃气轮机和柴油发动机，具有提高效率、燃油经济性、耐用性和性能的潜力。在这些应用中，涂层经受变化的高温和温度梯度，这可最终导致涂层的分层和剥落。涂层表面裂纹的存在已被证明可以增加其寿命。此外，最近的实验和分析结果表明，改变这样的裂纹的周期性和长度/厚度比可以减少在厚涂层中的界面裂纹扩展，其经受高表面温度和大的温度梯度。这些结果表明，通过在制造过程中引入周期性裂纹系统，应该可以减少使用中的界面裂纹。 这打开了使用通过等离子喷涂产生的厚热障涂层的可能性，这将在热负荷下提供显著更大的热保护和更长的寿命，并且还提供更大的设计灵活性和降低的加工成本。因此，本研究的目的是：（a）了解热障涂层界面裂纹在热喷涂过程中产生的表面裂纹下对高热流密度的响应;（B）使用受控实验和分析模型来确定裂纹长度、周期性、厚度结合随时间变化的涂层材料行为，在不同的热边界条件下对界面的热断裂进行了研究 *

9908187KokiniCeramic thermal barrier coatings offer the potential for improved efficiency, fuel economy, durability and performance in high temperature applications such as aerospace and aircraft engines, gas turbines and diesel engines. In these applications, the coatings are subjected to varying high temperatures and temperature gradients, which can ultimately result in delamination and spalling of the coating. The presence of surface cracks in the coating has been shown to increase its life. Furthermore, recent experimental and analytical results have shown that changing the periodicity and length/thickness ratio of such cracks can decrease interfacial crack propagation in thick coatings which are subjected to high surface temperatures and large temperature gradients. These results suggest that by introducing a periodic crack system during manufacture it should be possible to reduce interface cracking in service. This opens up the possibility of using thick thermal barrier coatings produced by plasma spraying, which would provide significantly greater thermal protection and longer life under thermal loads and also give greater design flexibility and reduced cost of processing. Thus, the objectives of the proposed research are: (a) to develop an understanding of the response of interface cracks in thermal barrier coatings subjected to high heat fluxes in the presence of surface cracks introduced during the thermal spray process; (b) to use controlled experiments and analytical models to determine the effects of crack length, periodicity, thickness, combined with time-dependent material behavior of the coating under different thermal boundary conditions on the thermal fracture of the interface.***