Abstract: An austentic steel component is fused to a ferritic steel component with a filler alloy specifically formulated to have a thermal coefficient of expansion similar to that of the ferritic steel, a creep rate intermediate between that of the ferritic and austenitic steels, a rupture strength at least as great as that of the ferritic steel, and a carbon activity intermediate that of the ferritic and austenitic steels. Suitable filler alloys have the following general compositions: (1) 1-3% nickel, 11-13% chromium, 1.6-2.0% molybdenum, 0.07-0.1% carbon, 0.5-0.9% manganese and 0-1.5% tungsten, balance iron, and (2) 41-56% nickel, 3.5-10.0% chromium, 1.6-2.5% molybdenum, 0.03-0.1% carbon and 0.5-2.0% manganese, balance iron.