Developments for gas turbine components[edit]

The use of CMCs in gas turbines permit higher turbine inlet temperatures, which improves engine efficiency. Because of the complex shape of stator vanes and turbine blades, the development was first focused on the combustion chamber. In the US, a combustor made of SiC/SiC with a special SiC fiber of enhanced high-temperature stability was successfully tested for 15,000 hours.^[31] SiC oxidation was substantially reduced by the use of an oxidation protection coating consisting of several layers of oxides.^[32]

The engine collaboration between General Electric and Rolls-Royce studied the use of CMC stator vanes in the hot section of the F136 turbofan engine, an engine which failed to beat the Pratt and Whitney F-135 for use in the Joint Strike Fighter. The engine joint venture, CFM International is using CMCs to manufacture the high-temperature turbine shrouds.^[33] General Electric is using CMCs in combustor liners, nozzles, and the high-temperature turbine shroud for its upcoming GE9X engine.^[34] CMC parts are also being studied for stationary applications in both the cold and hot sections of the engines since stresses imposed on rotating parts would require further development effort. Generally, development continues of CMCs for use in turbines to reduce technical issues and cost reduction.

After US$1.5 billion in investment and 20 years of research and development, by 2020 GE Aviation aims to produce per year up to 20 t (44,000 lb) of CMC prepreg and 10 t of silicon carbide fiber. Chemical vapor deposition can apply coatings on a laid-able fiber tape in large quantities and GE managed to infiltrate and cast parts with very high silicon densities, higher than 90% for cyclic fatigue environments, thanks to thermal processing.^[35]