A new Metallic Thermal Barrier Coating System for Rocket Engines: Failure Mechanisms and Design Guidelines

Abstract

To protect liquid rocket combustion chamber walls, a coating may be applied on the hot gas side. Recently, a new metallic coating system, applied with high-velocity oxyfuel spray, has been developed. To investigate the damage mechanisms of these coatings under large thermal loads, laser cycling experiments were performed, where the coating surface is heated up with a high-power laser to get a large temperature gradient, similar to the conditions in the combustion chamber. In these laser cycling tests, different damage mechanisms like large-scale buckling of the coatings or vertical cracks were observed. The main aim of this paper is to understand the failure mechanisms and to identify critical loads leading to coating failure. Tensile tests, laser cycling experiments and finite element simulations were carried out to determine critical elastic strains for crack initiation and gain a better understanding of the mechanisms and the critical loads for buckling.