Process for producing a corrosion resistant duplex coating

Claim 2

The process of claim 1 wherein each of the materials in step (a) is selected from one of the groups consisting of nickel, aluminum, cobalt, iron, chromium, copper, molybdenum, tungsten, niobium, tantalum, titanium, zirconium, vanadium, hafnium, magnesium, zinc, antimony, calcium, manganese, palladium, nichrome, iron-chromium alloys, iron-chromium intermetallics, cobalt-chromium alloys, cobalt-chromium intermetallics, iron-chromium alloys containing rare earth additions, nickel-chromium alloys containing rare earth additions, cobalt-chromium alloys containing rare earth additions, copper-aluminum alloys and copper-aluminum intermetallics.

Claim 3

The process as in claim 3 wherein the material of the article is selected from a group consisting of steel and cast iron; wherein in step (a) one of the materials is aluminum and the other material is selected from a group consisting of iron-chromium alloys, nickel-chromium alloys and cobalt-chromium alloys; and wherein in step (b) said primary coating is alumina.

Claim 4

The process of claim 1 wherein an additional step is added after step (c) as follows: d. subjecting the duplex coated article to an oxidizing atmosphere, a carburizing atmosphere, a nitriding atmosphere, a boriding atmosphere, or a siliciding atmosphere for a time period and at a temperature sufficient to react the medium in the atmosphere with segmented areas on the surface of the undercoat that are exposed to the exterior through the porosity of the primary coAting thereby providing a layer of the reacted medium on said exposed areas.

Claim 5

The process of claim 4 wherein after step (c) the following step is added: d. subjecting the duplex coated article to an oxidizing environment for a time period and at a temperature sufficient to oxidize segmented areas on the surface of the undercoat that are exposed to the exterior through the porosity of the primary alumina coating thereby providing an oxidized layer on said exposed areas.

Claim 6

The process of claim 5 wherein the medium in the atmosphere is present in a sufficient amount and under a sufficient partial pressure so as to effectively react the medium with one of the materials on the exposed areas of the undercoat surface.

Claim 7

The process as in claim 3 wherein in step (a) the two materials are aluminum, and a cobalt-chromium alloy containing rare earth additions; and wherein in step (b) said primary coating is MgZr03.

Claim 8

A process for producing a corrosion resistant duplex coated article comprising: a. depositing an undercoat of at least two materials, each of which is selected from one of the groups consisting of metals, alloys, and intermetallics, onto an article such that the materials are simultaneously deposited in a substantially unreacted state; b. heating said coated article in a non-contaminating atmosphere at a temperature and for a time period sufficient to cause the substantially unreacted materials in the undercoat layer to react or diffuse together thereby forming a substantially sealed, nonporous undercoat layer; and c. depositing a primary coating selected from at least one of the groups consisting of metals, metal alloys, intermetallics, metal oxides, metal carbides, metal nitrides, metal borides, metals silicides, and cermets, onto the substantially sealed undercoat layer thereby producing a duplex layer having excellent corrosion-resistant characteristics.

Claim 9

The process as in claim 9 wherein each of the materials in step a) is selected from the group consisting of nickel, aluminum, cobalt, iron, chromium, copper, molybdenum, tungsten, niobium, tantalum, titanium, zirconium, vanadium, halfnium, magnesium, zinc, antimony, calcium, manganese, palladium, nickel-chromium, iron-chromium alloys, iron-chromium intermetallics, cobalt-chromium alloys, cobalt-chromium intermetallics, iron-chromium alloys containing rare earth additions, nickel-chromium alloys containing rare earth additions, cobalt-chromium alloys containing rare earth additions, copper-aluminum alloys and copper-aluminum intermetallics.