MoSi<sub>2</sub> and Other Silicides as High Temperature Structural Materials

Abstract

There has been a revival of interest in MoSi;? and other refractory silicides, hitherto used for heating elements and coatings, as high temperature structural materials. With their high melting point and excellent high temperature oxidation resistance, silicides as a class of intermetallics, have potential for developing temperature capability beyond nickel base superalloys. Though metal like in their physical properties, silicides are in general brittle at room temperature. This drawback is being addressed through a variety of in-situ and artificial composite approaches. This paper attempts to provide a perspective on these approaches with a review of current activities. To provide a background, the development strategies for high temperature structural materials are discussed, followed by an overview on formation of silicides. The relevant mechanical and physical properties and environmental resistance of silicides are compared using superalloys as the benchmark, to help assess the risks versus benefits. Finally, the paper concludes with a brief summary of primarily fiber reinforced MoSi2 composites and ductile phase reinforced in-situ composites based on other silicides. The unavailability of suitable fibers and interface coating for conventional composites and containerless solidification for in-situ composites are identified as the principal problems. Superalloys 1992 Edited by S.D. Antolovich, R.W. Stusrud, R.A. MacKay, D.L. Anton, T. Khan, R.D. Kissinger, D.L. Klarstmm The Minerals, Metals & Materials Society, 1992