learning, process and facility development, and engineering application precursor work before they could be introduced into products. A clear lesson learned in this regard is the need to transition materials development from “technology push” to “technology pull” as quickly as possible so that all the requirements of the end application are identified early.
The amount of effort required for a new material introduction, especially for a new class of materials like TiAl, is beyond the level that any industrial company alone can support over the lengthy development process. Collaborative industry-government efforts were key to sustaining the needed “constancy of purpose” required to introduce new materials and processes into applications.
In the period of the 1970s through the early 1980s, little direct GE work was done; there was considerable Air Force funding of work at government laboratories, universities, and Pratt and Whitney, including work to produce and rig test low-pressure turbine (LPT) blades and other engine components.
In the mid- to late 1980s, gamma TiAl research and development (R&D) continued work at Pratt and Whitney, government laboratories, and universities. Alloy development work was funded both internally and by the Air Force at GE’s Global Research Center (GE GRC). GE alloy 48Al-2Cr-2Nb resulted from a chemistry matrix that was part of the internally funded work.
With respect to the criticality of the government-funded work, it is unlikely that GE would have pursued gamma TiAl without the precursor efforts or the parallel funding for alloy development work at GE GRC.
The end result of the 1980s’ alloy work was the establishment of GE 48-2-2, a material that has a nominal room temperature elongation of approximately 2 percent and environmental resistance so that it does not require coatings for applications up to approximately 800ºC. These are significant characteristics, as they make GE 48-2-2 attractive from an engineering and manufacturing standpoint. For comparison purposes, competing gamma TiAl alloys typically had nominal ductilities that were less than 1 percent and required environmental barrier coatings for extended use in the operational environment.