Structural and Thermal Properties of Ignition Resistant Coatings for Reusable Rocket Engines

Abstract

This thesis relates my investigation of an environmental barrier coating formulation, first developed for Russian RD-180 engines, which prevents ignition due to particle impact on ox-turbopump turbine. Ignition resistant environmental barrier coatings are of particular interest for reusable rocket systems, which have recently suffered oxygen compatibility failures. The study details the fabrication and characterization of the bulk material for use in a thermomechanical model to predict spallation during a flight cycle. From experimentation, the coating has been determined to be a three-phase metal-ceramic composite composed of nickel, cerium borate, and barium alumino-borate glass. These phases have been verified through thermodynamic modeling using FactSage. Thermal properties are similar to IN-718, while mechanical properties such as modulus and density are significantly lower. Initial studies of the crack propagation mechanisms suggest possible toughening of the composite due to the percolation of the ductile phase nickel. When compared to the theoretical stresses and energy release rates at the interface, the coating is expected to survive modern flight conditions. microstructural modification via experimental characterization and numerical analysis of delamination, could make these coatings suitable for modern reusable rocket engines.