Abstract
It has been recognized for some time that, with progressive increase in the working temperature of gas turbines, metallic alloys may no longer be adequate for rotor or stator blading. The use of more refractory but more brittle materials, i.e. ceramics and ceramic-metal mixtures (cermets) has been suggested. The paper is concerned with the evaluation of the major properties involved, viz. creep strength, fatigue strength, resistance to thermal fatigue (i.e. to repeated thermal shocks), oxidation-resistance, and impact-resistance. The materials evaluated include oxides, oxide–metal cermets, carbides, carbide-metal cermets, molybdenum disilicide, and silicon nitride. The equipment for determining the effects of alternating and steady mechanical stresses up to 1200° C. is described. The relative merits of the test materials are discussed. It is concluded that the resistance to thermal fatigue and to impact of the ceramics and cermets is inferior to that of metallic alloys in current use.
Notes
* Manuscript received 14 August 1958. Contribution to a Symposium on “The Powder Metallurgy of Ceramic-Metal Materials” to be held in London on 17 December 1958.