A nickel base superalloy, having either columnar or equiaxed grain structure, which has significantly improved resistance to hydrogen embrittlement, and to fatigue in air is disclosed. The superalloy consists essentially of, in weight percent, about 0.006-0.17 carbon, about 6.0-22.0 chromium, up to about 17.0 cobalt, up to about 9.0 molybdenum, up to about 12.5 tungsten, up to about 5.0 titanium, up to about 6.7 aluminum, up to about 4.5 tantalum, up to about 2.5 hafnium, up to about 18.5 iron, up to about 3.25 rhenium, up to about 1.25 columbium, remainder nickel. The microstructure of the superalloy consists essentially of a plurality of fine, discrete carbide particles, .gamma.' precipitates in a .gamma. matrix, and is essentially free of script carbides, .gamma./.gamma.' eutectic islands and porosity.