Process for applying thermal barrier coatings to metals and resulting product

Claim 1

A method of coating a metal substrate with a protective coating which comprises: (a) providing a substrate metal to be coated, (b) providing an alloy or mixture of (1) zirconium and/or hafnium, and (2) at least one other metal M 2 which does not form a stable oxide at an elevated temperature in an atmosphere having a very small partial pressure of oxygen, and which forms an alloy with at least one component of the substrate on heat treatment of the coated material, the zirconium and/or hafnium constituting not less than 50% by weight of the alloy or mixture, M 2 being present in substantial amount but not exceeding 50% by weight of the alloy or mixture, (c) applying such alloy or mixture to a surface of the substrate (1) by dipping the substrate in a molten alloy or mixture of zirconium and/or hafnium and M 2 or (2) by applying a slurry in a volatile liquid of zirconium and/or hafnium and M 2 in finely divided form either as the separate metals or as an alloy of the metals, then vaporizing the solvent and fusing the metals; (d) effecting selective oxidation of the zirconium and/or hafnium at an elevated temperature in the coating without substantial oxidation of M 2 , (e) said method resulting in a coating which is bonded to the substrate, said coating having an outermost dense layer of zirconium and/or hafnium oxide substantially free from M 2 , an intermediate layer containing zirconium and/or hafnium oxide and M 2 and an innermost layer of M 2 alloyed with one or more metals from the substrate.

Claim 2

A method of coating a metal substrate with a protective coating which comprises: (a) providing a substrate metal to be coated, (b) providing an alloy or mixture of (1) zirconium and/or hafnium, and (2) at least one other metal M 2 which does not form a stable oxide at an elevated temperature in an atmosphere having a very small partial pressure of oxygen, and which forms an alloy with at least one component of the substrate on heat treatment of the coated material, the zirconium and/or hafnium constituting not less than 50% by weight of the alloy or mixture, M 2 being present in substantial amount but not exceeding 50% by weight of the alloy or mixture, (c) applying such alloy or mixture to a surface of the substrate (1) by dipping the substrate in a molten alloy or mixture of zirconium and/or hafnium and M 2 or (2) by applying a slurry in a volatile liquid of zirconium and/or hafnium and M 2 in finely divided form either as the separate metals or as an alloy of the metals, then vaporizing the solvent and fusing the metals; (d) effecting selective oxidation of the zirconium and/or hafnium at an elevated temperature in the coating without substantial oxidation of M 2 , (e) said method resulting in a coating which is bonded to the substrate, said coating having an outermost dense layer of zirconium and/or hafnium oxide substantially free from M 2 , an intermediate layer containing zirconium and/or hafnium oxide and M 2 and an innermost layer of M 2 alloyed with one or more metals from the substrate.