GB600068A - Improvements in iron-base alloys - Google Patents

Abstract

An iron-base alloy has the following composition: Cr 15.0-25.0 per cent, Ni 15.0-25.0 per cent, Co 10.0-25.0 per cent, Mo 1.0-3.5 per cent, W 0.5-7.5 per cent, one of Nb, Ta and V 0.5-2.5 per cent, or more than one of these elements in an aggregate amount of 0.5-3.0 per cent, N2 0.05-0.25 per cent, Mn 0.1-2.0 per cent, Si 0.1-1.0 per cent, C 0.01-1.0 per cent but preferably not exceeding 0.35 per cent, Fe the remainder together with incidental impurities, the aggregate of the elements other than iron being less than 75 per cent. The metals Nb, Ta or V or the aggregate content of them may be wholly replaced by Al in an amount from 0.5 to 2.0 per cent, or they may be partly replaced by Al in which case the aggregate content of the said metals and Al does not exceed 3.0 per cent. The alloys may be used for hot-worked, welded or cast articles which in normal use are exposed to elevated temperatures, e.g. above 1,200 degrees F. the alloys being capable of withstanding a tensile stress of at least 10,000 lbs. per square inch for at least 1,000 hours at 1,500 degrees F. The alloys may be used for turbine blades, wheels or other parts exposed to high temperatures. An alloy example is referred to containing 21 per cent Cr, 21 per cent Ni, 21 per cent Co, 1 per cent Nb, 0.28 per cent C, 0.11 per cent N2, 0.5 per cent Si, 1.5 per cent Mn, 3 per cent Mo, 2 per cent W with remainder Fe in a condition resulting from forging, heating for 1/2 hour at 220 degrees F. quenching in water, heating for four hours at 1,500 degrees F. and air cooling.