Understanding the formation of limited inter-lamellar bonding in thermal sprayed ceramic coating

The thermal sprayed coatings exhibit a lamellar structure and the lamellar bonding is one of the most important factors controlling the mechanical, thermal and electrical properties of the coatings. However, it is not clear why only limited lamellar bonding exists in a thermal spray coating. In our previous study, it was found that there exists a critical bonding formation temperature for depositing ceramic splats. Moreover, the critical bonding temperature is related to the interface temperature prior splat solidification which is determined by the glass transition temperature of splat material. In the present study, the critical bonding temperature and the relationship were used to understand the limited bonding ration. A numerical simulation model involving heat transfer among depositing splat was proposed to explain the bonding formation in the coatings based on the necessary condition that the splat-substrate interface temperature prior splat solidification should be higher than intrinsic glass transition temperature.