(57) A castable nickel base alloy is hot corrosion and oxidation resistant and has high temperature strength, including stress rupture strength at 760°C (1400°F) and 982°C (1800°F). The alloy contains, by weight: from 12 to 22% chromium, from 3 to 12% of at least one of up to 5% molybdenum, up to 10% tungsten and up to 2% vanadium, up to 6% tantalum, up to 2% columbium, from 2 to 6% aluminium, from 1 to 6% titanium, up to 5% cobalt, up to 2% iron, from 0.015 to 0.15% carbon, from 0.03 to 0.3% boron, up to 0.1% zirconium and balance nickel.