Abstract

Polysilazane-based ceramic coatings have ever-increasing applications in critical and high-power engineering. This paper analyzes the effects of the substrate grain size, the curvature of the coating-substrate interface and the pore-free coating layer on the plastic strain localization and fracture of the porous ceramic coating–polycrystalline substrate structures under compressive loading applied to the coated surface. Models for generating pore and polycrystalline structures of the coating and substrate are developed, with the experimentally observed microstructures of the coated steel being taken into account in calculations explicitly as the initial data of the boundary-value problem. Numerical results obtained by the finite-difference method show that the crack-initiation strain depends on the substrate grain size exponentially. A comparison between the models with serrated and plane coating-substrate interfaces suggests that in the former case, coating cracking initiates near the humps of the interface concavities and the top and bottom pore surfaces, while in the latter case, two sites of cracking nucleation can be distinguished, namely, close to the pores – in the fine-grained substrate, and near the coating-substrate interface – in the case of coarse grains. The results indicate that it is preferable to use the coated specimens characterized by a serrated coating-substrate interface.

摘要

基于聚硅氮烷的陶瓷涂层在关键和高功率工程中的应用越来越多。本文分析了基体晶粒尺寸、涂层-基体界面曲率和无孔涂层对多孔陶瓷涂层-多晶基体结构在施加于涂层表面的压缩载荷作用下塑性应变局部化和断裂的影响。 . 开发了用于生成涂层和基材的孔隙和多晶结构的模型，在计算中明确考虑了涂层钢的实验观察微观结构，作为边界值问题的初始数据。通过有限差分法获得的数值结果表明，裂纹起始应变与基体晶粒尺寸呈指数关系。锯齿状和平面涂层-基材界面模型之间的比较表明，在前一种情况下，涂层开裂在界面凹面和顶部和底部孔表面的隆起附近开始，而在后一种情况下，两个开裂形核位置可以区分，即靠近孔隙 - 在细晶粒基材中，以及在涂层 - 基材界面附近 - 在粗晶粒的情况下。结果表明，优选使用以锯齿状涂层-基材界面为特征的涂层试样。可以区分两个开裂成核的位置，即靠近孔隙——在细晶粒基材中，以及在涂层-基材界面附近——在粗晶粒的情况下。结果表明，优选使用以锯齿状涂层-基材界面为特征的涂层试样。可以区分两个开裂成核的位置，即靠近孔隙——在细晶粒基材中，以及在涂层-基材界面附近——在粗晶粒的情况下。结果表明，优选使用以锯齿状涂层-基材界面为特征的涂层试样。