A Numerical Study on Generation Mechanism of Vertical Cracks in Top Coat of TBCs During APS Deposition

Abstract

Clarification of crack generation mechanism in the top coat of the thermal barrier coatings (TBCs) during atmospheric plasma spray process is important to improve the reliability of TBC. In this study, finite element analyses of stress and strain during the deposition process were conducted with layer-bylayer method to understand the cracking behaviors. Stress relaxation by generation of vertical cracks was expressed as an elasto-plastic behavior of the coating. The effects of pre-heating temperature of the substrate and plasma power on crack development were analyzed by changing of the initial and atmospheric temperatures in simulation, respectively. The simulation results of radial strain explained the experimental results of crack monitoring by non-contact laser acoustic emission method.

Restrained TGO growth in YSZ/NiCrAlY thermal barrier coatings by modified laser remelting

“…Increasing the temperature of the superalloy substrate can reduce the temperature gradient along the TBC system during the APS process and thereby minimize the size of cracks in the ceramic topcoat, which may also be effective during the laser remelting process [25][26][27].…”