Heat resistant Ni-Mo alloy is produced by heat treating a conventional alloy, of compsn. (by wt.) 74-65% Ni, 26-30% Mo, max. 2% Fe, max. 1% Co, max. 1% Cr and max. 1% Mn, at 650-750 (pref. 690-710) deg.C for 1-96 (pref. 48-72) hrs. The alloy is esp. useful as a self-lubricating material for mfr. or coating of drive components, operating at 400-600 deg.C and a sliding friction pressure of 5-20N/sq.mm., as well as rotating shafts, bearings and seals, in contact with the same alloy, not work sheets (e.g. x38CrMoV51 or x40CrMoV51), high speed steels (e.g. DIN 1.3207, 1.3243 or 1.3342) and martensitic chromium steels (e.g. DIN 1.4112 or 1.4122). Heat treatment of the alloy (NiMo28) gives a hardness of up to 41HRC which is maintained at up to 600 deg.C. At above about 400 deg.C and under friction conditions, the alloy surface forms a soft oxide contg. Ni oxide and Mo oxide, which is self-regenerating, adherent and resistant to hot oxidising gases. The alloy can be shaped by casting, machining or working since it is relatively soft before heat treatment and heat treatment can be carried out in air followed by cooling in air.
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