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Abstract

It is an objective of the present invention to provide low thermal expansion alloys having excellent high temperature mechanical properties, the oxidation resistance, and the electrical conductivity by modifying the basic Cr--W--Fe alloy in order to meet various industrial demands including prolonging the life of plant machinery being operated at high temperature and a scaling-up solid oxide fuel cell, so that the coefficient of thermal expansion can be approximated to those of stabilized zirconia. In order to achieve these objectives, Co is added to Cr--W--Fe system alloy possessing an excellent thermal matching characteristic to stabilized zirconia in order to enhance the high temperature mechanical properties without changing original properties of thermal matching, the oxidation resistance and the electrical conductivity. Cr and Al are added in order to further improve the oxidation resistance and to approximate the coefficient of surface thermal expansion to that of stabilized zirconia. Furthermore, by adding at least one element properly selected from the element group comprising of Ti, Zr, and Hf, the electrical resistance can be reduced; if Hf element is co-added with B element, the hot working characteristics can be especially improved. Any combination of Co, Al, and (Ti,Zr,Hf) can be appropriately chosen and added to the basic Cr--W--Fe system alloys. B element can be added in order to prevent the grain boundary segregation of W element. In order to improve a further resistance against the high temperature oxidation, one or more than two elements properly selected from the element group comprising of Y, Hf, Ce, La, Nd, and Dy can be added to the basic Cr--W--Fe system alloy.

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First Claim