Under certain conditions, higher jet-engine thrust can be obtained by an increase in operating temperatures. The availability of suitable materials for turbine-bucket and sheet-metal parts is one of the factors limiting the extent to which higher operating temperatures can be realized.
In this paper, data on mechanical properties, physical constants, and surface and structural stability are presented, which are believed to be representative of the highest caliber of materials currently available. Other materials exist which have similarly attractive properties. The turbine-bucket materials considered are X-40, HE1049, J-1570, two molybdenum-base alloys (0.3 per cent columbium molybdenum and 0.5 per cent titanium molybdenum), and one cermet (K162B). Sheet alloys considered are Inco 702, Hastelloy C, Incoloy T, and L-605.
For turbine buckets, the nickel- and cobalt-base alloys discussed have properties that make them candidates for application up to possibly 1700 F. The molybdenum and cermet materials appear to have possibilities for application at 1800 F and higher, provided certain inherent disadvantages associated with their use can be overcome.
The sheet alloys discussed can be applied at temperatures up to 2100 F within certain stress and time limitations. For high stress applications involving exposure of sheet metal to temperatures exceeding 1800 F, it will be necessary to resort to cooling, insulative ceramic coatings, or protectivelycoated molybdenum alloy sheet. Though development of the latter is believed to be a considerable way off, it represents the only hope at present for significantly stronger sheet-metal alloys for temperatures in excess of 1800 F.