Cermets with low coefficient of thermal expansion

A cermet comprises grains 12 selected from W, Ti, Mo, Nb, V, Si, Hf, Ta, Cr - carbide, nitride, carbonitride, boride and mixtures thereof, a grain binder alloy 14 formed from of elements selected from Co, Ni, Fe, W, Mo, Ti, Ta, V, Nb, C, B, Cr and Mn, wherein the binder alloy has a coefficient of thermal expansion of less than about 10 ppm/{C within the temperature range of 100-700{C. The binder alloy may be iron based and comprise 10-30 weight % cobalt and 10-40 weight % nickel. The cermet may comprise 5-30 weight % binder alloy. The grains and binder alloy may be disbursed in phase (22, Fig. 5) consisting of Co, Ni, Fe, W, Mo, Ti, Ta, V, Nb, alloys thereof and alloys with elements selected form B, Cr and Mn. Also a cermet comprising a hard material selected from the carbides, nitrides carbonitrides and borides of Group IVA, VA and VIA elements in a binder formed from a mixture of elements selected from Co, Ni, Fe, W, Mo, Mn, Cu, Al, Nb, C, Ti and Ta wherein the binder has a coefficient of thermal expansion as above and the cermet comprises a repeated arrangement of structural units each of which has an ordered microstructure (Fig. 6).