This Small Business Innovation Research Phase I project is aimed at development of a novel, low-cost process for manufacturing environmental barrier coatings (EBCs) for ceramic matrix composites (CMCs) in aviation gas turbines. A key limitation for CMC adoption is the unavailability of inexpensive, truly gas impervious EBCs to provide required CMC engine service life. While novel EBC compositions have been identified, methods of depositing thin, dense gas impervious coatings with these compositions have largely been vapor-based processes that are expensive, inefficient (non-line-of-sight) and slow (low deposition rates). Efforts to utilize low-cost, and fast plasma spray processes, familiar to the turbine industry, have had some success, but still need major improvements. As an enabling technology for CMC adoption into aircraft gas turbines, the proposed EBC processing technology, solution precursor plasma spray, has the potential to fuel wider adoption of CMCs into aviation gas turbines. The EBC market itself, driven by such a wider adoption of CMCs, can grow to over $300 Million by 2025. The efficiency gains due to such wider adoption of CMCs can substantially lower fuel consumption and greenhouse gas emissions by up to 15% in new aircraft.The intellectual merit of this project is illustrated by the fact that it is the first demonstration of solution precursor plasma spray (SPPS) for EBC processing. The unique ability of the SPPS process to achieve very thin, high-density coatings is driven by the very small splat sizes of the solution-derived particles relative to powder-based processes. The SPPS process offers a route to get coatings similar to what is feasible with vapor based processes, but at much faster coating rates and lower cost. In the SPPS approach, a liquid chemical precursor, containing the desired cations, is atomized into the plasma jet. The injected solution evaporates and the resulting chemicals are pyrolyzed, followed by melting and deposition of targeted oxides as splat of sizes less than 5 microns compared to 30-125 microns with the conventional air plasma spray process. This makes the deposition of thin, dense coatings possible. In Phase I, the feasibility of depositing thin, dense state-of-the art EBC compositions on silicon carbide substrates will be demonstrated, and preliminary durability of the coatings will be demonstrated. The deposition of EBCs with thickness less than 50 micron and with density greater than 95% will be demonstrated.
