Effect of Temperature and Velocity on Microparticle Erosion/Deposition into Environmental-Barrier-Coated Ceramic Matrix Composite for Aeroengines

Abstract

Ceramic matrix composites (CMCs), especially SiC/SiC, have garnered significant attention owing to their remarkable mechanical properties at higher temperatures. For protection of the substrate from oxidation, the SiC/SiC CMCs inherently require environmental barrier coating (EBC). Because aeroengines must function under a wide range of conditions and environments, the coated CMC must be sufficiently resistant to various damage modes. Among these, the effect of microparticles is one of the limiting factors for durability and performance of components, particularly when the engine is operated in dusty areas. The main goal of this experimental research is to investigate and determine the surface damage behaviour of the coated CMC caused by micro sand particles. The data were surveyed across a fairly broad range of exposed temperatures and velocities, and covered conditions relevant to advanced hot section designs. In the experiments, silica or alumina sand entrained in the gas stream was jet-blasted from the nozzle and then impinged on the target CMC+EBC coupon. Owing to the broad testing range, the damage mode and extent of damage varied considerably by condition. The obtained data were then reorganised and compared with several previously proposed particle impact models. This is to first understand and obtain a complete picture of all the probable consequences in the expected design and off-design conditions, and second, to determine the validity of, and deviations from the conventional modelling with the present CMC+EBC material, which will be useful in the next component design phase.

Solid particle erosion in ceramic matrix composites and environmental barrier coatings: A perspective

“…77 A recent study showed that the melting and crystallization properties of synthetic CMAS compositions is highly dependent on the CaO:SiO 2 ratio where the initial onset of melting occurred as low as ∼1050 • C while full melting temperatures could occur as high as 1,500 • C. 78 This suggests that SPE can still occur at operating temper-atures as high as 1500 • C. As a result, the gas temperature, particle composition, and particle velocity/kinetic energy will determine the mode of damage: only erosion, erosion plus deposition, only deposition, or no erosion nor deposition. 79 Current techniques for evaluating CMAS corrosion of EBCs have been focused on static loading where the CMAS is applied to the surface at ambient temperature and then melted/reacted in a furnace. 80 In application, CMAS deposition, and correspondingly, SPE and the synergistic effects between the two modes (erosion-corrosion) are dynamic in nature.…”

“…Erosion-corrosion studies have been performed for TBCs, but this area remains largely unexplored for EBCs. It is worth noting that Okita et al 79 performed an initial investigation on the effect of temperature and velocity for microparticle erosion/deposition on an EBC/CMC using crushed quartz particles. The results showed general agreement with a critical viscosity model where deposition dominated below the critical viscosity of quartz (silica) and erosion dominated above the critical viscosity.…”

“…This suggests that SPE can still occur at operating temperatures as high as 1500°C. As a result, the gas temperature, particle composition, and particle velocity/kinetic energy will determine the mode of damage: only erosion, erosion plus deposition, only deposition, or no erosion nor deposition 79 …”

“…Erosion‐corrosion studies have been performed for TBCs, but this area remains largely unexplored for EBCs. It is worth noting that Okita et al 79 . performed an initial investigation on the effect of temperature and velocity for microparticle erosion/deposition on an EBC/CMC using crushed quartz particles.…”