Heat resisting nickel alloys using directional solidification - to ppte. lamellar intermetallic cpds. which increase strength

摘要

Nickel base alloy contg. molybdenum plus addns. 1 of the elements Co, Cr, Al, Si and B, in a concn. such that by directional solidification in a temp. gradient, a two- or multi-phase composite material is formed in which a single- or multi-component phase is embedded parallel to the direction of solidification in a matrix of nickel mixed crystals. The intermetallic phase is pref. (a) the sigma phase (Ni-Cr-Mo) or the rho phase (Ni-Cr-Mo); (b) the Laves phase Mo (Ni1-xSix)2; (c) Mo2NiB2; and the alloy may contain Mo fibres. The alloy may also contain the following maxima in atom % 10% Ti, 0.5% Zr, 0.05% Fe, 10% W, 4% Ta, 2% Hf, 0.03% Y, to increase strength and corrosion resistance, plus 2% max. Si or B in excess of that in cpds. (b) or (c). The heat resisting alloys obtd. are used e.g. for gas turbine applications. They have increased strength and corrosion resistance, e.g. when Si is added it is present in the reinforcing lamellae so the ductility of the matrix is not impaired.