High Temperature Duplex Coating

The goal of this SBIR research is to demonstrate the feasibility of using Korolon TBC in hot gas path components of gas turbines through mechanical and thermal characterization of the coating and feasibility study of a novel micromachining technology for drilling the cooling holes. Korolon is a novel coating that has a similar thermal conductivity as the currently used zirconia and is more erosion resistant. Our coating has been evaluated for corrosion and durability at elevated temperatures and harsh environments. The coating is applied at room temperature and cured at elevated temperatures. This novel coating is deposited directly on Ni-based superalloys without the need for a bond coat. In Phase I, we propose to determine the coating thickness needed for turbine applications, modify the coating deposition process to allow deposition of thick coatings, evaluate coating/substrate adhesion strength and perform limited thermal conductivity tests to verify the thermal properties. Additional thermal and durability testing will be performed in Phase II. Coated test coupons will be subjected to thermal cycling tests in Phase II and the coating durability will be evaluated through several tests such as erosion and indentation by sharp indenters. The coating deposition process will be further optimized and final coating composition will be applied to turbine blades, and will be evaluated with an industrial or government laboratory partner in Phase II. Another important issue that will be investigated further in Phase II is micromachining of cooling holes and patterns using the recently developed MiTi ultra high speed micromachining system. This system is capable of microgrinding of small 0.1 to 1.0 mm features and through holes at speeds near half a million rpm in metals and ceramics. Commercial Applications and Other Benefits: The use of more efficient and durable thermal barrier coating will lead to increased engine efficiency by maximizing inlet temperature and/or reducing the amount of cooling air required for airfoils. The increased engine efficiency translates to reduction of fuel usage, thus reducing our reliance on imported fossil fuels and preserving our natural gas resources. The coating technology developed in this program will have several civilian and military applications, aside from gas turbine engines.