Modelling damage and fracture evolution in plasma-sprayed ceramic coatings: effect of microstructure

Ceramic coatings are thin layers bonded to substrates (typically metal ones) for protection from wear, chemical attack and high-temperature environments. They have been increasingly used in industry for many years. However, stresses induced by the properties mismatch between coatings and substrates, as well as brittleness of ceramics, may lead to failure of coatings in service, and hence they have been the principal problem encountered with ceramic coatings. It has been known that the microstructure of ceramic coatings has a significant effect on their mechanical and thermal properties. However, there has been neither a standard account for the effect of microstructure on damage and fracture evolution in coatings nor an adequate quantitative description of that effect. Little is known about crack nucleation processes at the microscale, while extension of damage and fracture mechanics to microstructures has become an urgent concern. These challenges await serious studies. Thus, the purpose of this research was to investigate damage and fracture evolution in ceramic coatings under mechanical and/or thermal loading, as well as to study the effect of microstructure on properties of ceramic coatings and their behaviour under loading, by means of numerical and experimental studies. [Continues.]