Tailoring approach to predict the microstructure of thermal barrier coatings by adjusting the distribution of splat morphologies

采用APS工艺，用不同的方法收集了大气等离子喷涂氧化铝和YSZ(氧化钇稳定的氧化锆片)，并由不同的研究人员进行了研究。关于飞行中的粒子和衬底条件对所获得的片状形貌的影响是一致的。然而，影响条件之间的相互作用的影响仍然不明确。此外，在所研究的片状形貌分布与所产生的涂层内的气孔和裂纹特征之间没有建立明显的关系。由于TBC面层涂层的效率主要取决于孔洞的密度、形态和分布以及分段裂纹的密度，因此每个应用领域都有结合所需的气孔和裂纹特征的最佳规格。因此，本研究的主要内容是收集YSZ板材，并在不同条件下采用实验设计方法制备相应的涂层。拼板的收集将通过创新的自制光束快门设置实现，该设置仅在研究所可用。拟议的工作计划首先通过详细的碎片分析确定碎片形态的一系列分布，并在这些分布与相关条件之间建立明确的关系。然后，必须在已识别的片状形貌分布和由此产生的气孔和裂缝特征之间建立通常有效的关系。此外，通过研究导致所需微结构同时共存的条件之间的相互作用，识别片状形貌和分段裂纹的分布被优化。尽管优化过程将增强控制涂层孔隙率的片状形貌的分布，但可实现的孔隙率水平在技术上仍然受到限制。因此，在YSZ喷雾粉末中添加造孔剂，以使气孔率达到较高水平。原料粉中造孔剂体积分数最高可达50%。在进行实验时将使用混合变化法。利用横截面涂层的扫描电子显微镜图像，研究了在涂层中添加造孔剂对获得的涂层孔隙率的影响。最后，应在所有这些条件和所获得的显微组织特征之间建立直接关系。所获得的结果将使我们能够生产具有预定微结构特征的APS涂层，并提高重复性

Atmospheric plasma sprayed Alumina and YSZ (Yttria stabilized zirconia) splats have been collected by different methods using APS process and investigated by different researchers. There is an agreement on the influence of in-flight particle and substrate conditions on the obtained splat morphologies. However, the impact of the interactions between the affecting conditions remains ill-defined. Furthermore, no clear relationships were established between the investigated distributions of splat morphologies and the resulted characteristics of pores and cracks within the produced coatings. Due to the fact that the efficiency of a TBC top coating depends mainly on the density, morphology and distribution of voids as well as on the density of segmentation cracks, there are optimal specifications that combine the required characteristics of pores and cracks for each field of application. In turn, the exerted thermal and mechanical loads determine the optimal required combinations.Therefore, the main aspect of this study is to collect YSZ splats and to produce the corresponding coatings under different conditions using DoE (Design of experiments) approach. The collection of splats will be achieved by means of the innovative and self-made beam shutter setup, which is available exclusively at the institute. The proposed work plan starts by identifying series of distributions of splat morphologies through a detailed splat analysis and establishing well-defined relationships between these distributions and the associated conditions. Afterwards, generally valid relationships have to be established between the identified distributions of splat morphologies and the resultant characteristics of pores and cracks. Furthermore, identifying the distributions of splat morphologies and segmentation cracks are optimized by investigating the interactions between the conditions that lead to the simultaneous coexistence of the desired microstructure. Even though, the optimization process will enhance the distributions of splat morphologies that control the coating porosity, the achievable level of porosity remains technically limited. Therefore, it is intended to add pore formers to YSZ spraying powders in order to increase the porosity to higher levels. The feedstock powders consist of up to 50 vol.% of pore former. A mixture variation will be utilized in conducting the experiments. SEM images of cross-sectional coatings will be used to investigate the effect of adding pore former on the obtained porosity within the obtained coatings. Finally, a direct relationship should be established between all these conditions, and the obtained microstructural features. The obtained results should allow us to produce APS coatings with predefined microstructure characteristics and enhance the reproducibility