GB723899A - Improvement in protective coating for molybdenum and molybdenum base alloys - Google Patents

Abstract

In a method of forming an oxidationresistant coating on a molybdenum or molybdenum-base alloy article suitable for use at high temperatures, a coating containing metallic aluminium and silicon is applied and the article heated under non-oxidizing conditions to form a coating and diffusion may be effected by dipping into a molten bath of aluminium and silicon at at least 1350 DEG F., or the aluminium-silica alloy may be sprayed on to the article which is then heated under non-oxidizing conditions, for example in dry hydrogen, to above 1400 DEG F. Three coatings may be applied, the first and third consisting primarily of aluminium and the second being a silicon-containing alloy applied by spraying. The sprayed coatings may also include molybdenum, chromium, iron or nickel. Suitable coating alloys are Al 95 per cent, Si 5 per cent; Mo 37 per cent, Si 32 per cent, Ni 30 per cent; Al 33 per cent, Cr 21 per cent, Mo 21 per cent, Si 22 per cent; and Si 70 per cent, Al 30 per cent.