Patent ID: 6013142
Filing Date: 2000-01-11
Classification: C21D,C22F

Abstract:
A process for heat treating, at a selected heat treatment temperature, a solid substrate constituted of an aluminum alloy that is solid but is susceptible to High Temperature Oxidation at the heat treatment temperature when in direct contact with a gaseous atmosphere containing water vapor, sulfur, or both, said process comprising steps of:(I) coating the surface of the solid substrate at a coating temperature with a liquid containing a combination of (i) a material that is chemically stable and non-reactive with any of the constituents of the liquid at the coating temperature but that, in isolation, releases a fluorine-containing gas at the heat treatment temperature and (ii) a binder material, so as to form an adherent liquid layer over the substrate;(II) forming a solid coated substrate by drying the liquid layer formed in step (I) while it remains in place over the substrate, to produce from said liquid layer an adherent solid coating, at least part of which will not melt, soften, and/or decompose at the temperature of heat treating so much as to spontaneously eliminate contact between the surface of the substrate and at least one of a solid or a liquid phase derived from said adherent solid coating;(III) forming a coated and heat treated substrate by bringing the solid coated substrate produced in step (II) to the selected heat treatment temperature; and(IV) cooling the coated and heat treated substrate produced in step (III), while at least one of a liquid and a solid phase derived from said adherent solid coating remains in direct contact with the surface of the substrate, to a temperature at which the substrate is no longer susceptible to High Temperature Oxidation when in contact with the ambient natural atmosphere.