I agree, RR, a fascinating bit of technology in materials research.
I also read that GE will be evaluating CMC turbine nozzle guide vanes and HP turbine blades on their GE9X test rig. But I doubt these more demanding applications will make it onto the GE90 engine model for the 777X.
According to GE Aviation, testing phase of CMC's in the 9X engine occurred in 2014. The company also says there will be CMC materials in the combustor and turbines on the new GE9X.
From specifications (pre design-lock, but current as of June 2015):
Ceramic matrix composite (CMC) material in the combustor and high-pressure turbine.
I also believe your comment about CMC materials eliminating the need for film cooling of turbine inlet nozzle guide vanes and HP turbine blades may not be entirely correct.
I think they have made a breakthrough, Riff. Quote from GE technical:
The material has two hugely winning attributes for aviation: it’s one- the weight of metal, and it’s also heat-resistant and doesn’t need to be air-cooled.
The go on to talk about how traditional turbine blades are laser drilled for air cooling passages and how the CMC eliminates this cooling requirement.
Regarding hot section temps, apologies if my comment was misleading. I agree, one firm goal is indeed to reduce overall temperatures for emissions standards, however engine hot section
components will operate at much higher temps than ever before thanks to the new materials. That is what I intended to say.
The latest reference I could find on the NASA doc you linked was 2010. Perhaps tech has advanced considerably since publication?
Weight is a big one for sure, RR. The strength requirement of the turbine disk is one area where the lighter CMC blades will save weight and already the composite fan blades and case currently reduce engine weight without sacrificing performance or safety.