Enhanced oxide whisker growth on peeled Al-containing stainless steel foil

A method of forming a metal foil of a ferritic stainless steel alloy containing 15 to 25 weight percent Cr, 3 to 6 weight percent Al, optionally 0.3 to 1.0 weight percent Y and the balance Fe, said foil having densely spaced oxide whiskers on a surface thereof, said method comprising

• forming by metal peeling a severely cold-worked foil having an irregular surface, and
• heating the peeled foil in air to a suitable temperature of between about 870.degree. and about 970.degree. C. for Y-free alloys or between about 870.degree. C. and about 930.degree. C. for Y-containing alloys for a time sufficient to grow said oxide whiskers on said surface.

A method of growing densely spaced oxide whiskers on a surface of a metal foil of a ferritic stainless steel alloy consisting essentially of 15 to 25 weight percent Cr, 3 to 6 weight percet Al, 0.3 to 1 weight percent Y and the balance Fe, said method comprising

• metal peeling the alloy to form a severely worked foil having an irregular surface, and
• heating the peeled foil in air to a temperature of between about 870.degree. C. and about 930.degree. C. for a time sufficient to grow said oxide whiskers on said surface.

A method of preparing a metal foil surface to receive a coating, said metal foil comprising a ferritic stainless steel alloy containing Al, said method comprising

• forming a metal foil from a cylindrical billet of said alloy by rotating the billet, peeling a continuous strip from the billet surface with a suitable cutting tool and pulling said strip away from the billet surface to form the foil, and
• heating the peeled foil in an oxygen-containing gas at a temperature and for a time sufficient to grow on a surface thereof oxide whiskers that substantially cover said foil surface and are capable of substantially improving the adhesion of a subsequently applied coating.

A method of preparing a metal foil surface to receive a coating, said metal foil being formed of a ferritic stainless steel alloy composed predominantly of iron and comprising 15 to 25 weight percent Cr and 3 to 6 weight percent Al, said method comprising

• forming a severely cold-worked metal foil from a cylindrical billet of said alloy by rotating the billet, peeling a continuous strip from the billet surface with a suitable cutting tool and pulling said strip away from the billet surface to form the foil, said foil having an irregular surface, and
• heating the peeled foil in air at a suitable temperature between about 870.degree. C. for a time sufficient to grow on the foil surface high aspect ratio alumina whiskers that substantially cover said foil surface and are capable of substantially improving the adhesion of a subsequently applied coating.

A method of preparing a metal foil surface to receive a coating, said metal foil being formed of a ferritic stainless steel alloy consisting of 15 to 25 weight percent Cr, 3 to 6 weight percent Al, 0.3 to 1.0 weight percent Y and the balance Fe, said method comprising

• forming a severely cold-worked metal foil from a cylindrical billet of said alloy by rotating the billet, peeling a continuous strip from the billet surface with a suitable cutting tool and pulling said strip away from the billet surface to form the foil, said foil having an irregular and severaly worked surface, and
• heating the peeled foil in air at a temperature between about 870.degree. C. and about 930.degree. C. for at least eight hours to grow on the foil surface alumina whiskers on the order of 3 microns high that substantially cover said foil surface and are capable of substantially improving the adhesion of a subsequently applied coating to the metal foil.

A peeled metal foil formed of a ferritic stainless steel alloy containing Al and having a surface that is substantially covered by densely spaced alumina whiskers.

A peeled metal foil formed of a ferritic stainless steel alloy composed predominantly of iron and containing 15 to 25 weight percent Cr and 3 to 6 weight percent Al, said foil having a surface that is substantially covered by alumina whiskers.

A metal foil formed by a metal peeling process of a ferritic stainless steel alloy consisting of 15 to 25 weight percent Cr, 3 to 6 weight percent Al, 0.3 to 1.0 weight percent Y and the balance Fe, said foil having a surface that is substantially covered by high aspect ratio alumina whiskers.

In a monolith-type catalytic converter of the type suitable for the high temperature treatment of automotive exhaust gases, said converter comprising a structural member comprising a metal foil and having gas-conveying passageways therethrough, said foil being composed of an Al-containing ferritic stainless steel alloy and carrying a catalyst-impregnated alumina coating, the improvement wherein

• the foil comprises peeled metal foil having an oxidized surface that is formed of and substantially covered by densely spaced oxide whiskers, and
• the coating is applied onto said oxide whiskers thereby improving adhesion of said coating to said foil.

In a monolith-type catalytic converter of the type suitable for the high temperature treatment of automotive exhaust gases, said converter comprising a structural member having gas-conveying passageways therethrough and comprising a metal foil carrying a catalyst-impregnated alumina coating, said foil being composed of a ferritic stainless steel alloy comprising 15 to 25 weight percent Cr, 3 to 6 weight percent Al, and predominantly Fe, the improvement wherein

• the foil comprises peeled metal foil having a surface that is substantially covered by densely spaced, high aspect ratio alumina whiskers, and
• the coating adheres to said alumina whiskers thereby improving the adhesion of said coating to said foil.

A method of manufacturing a coated metal structural member comprising,

• providing a substrate comprising an Al-containing ferritic stainless steel alloy and having an oxidized surface that is substantially covered by oxide whiskers, and
• applying to the whisker-covered surface a coating that penetrates between the whiskers and thereby becomes tightly bonded to the substrate.

A method of manufacturing a catalytically coated metal foil structural member, said method comprising,

• providing a foil substrate comprising a ferritic stainless steel alloy containing 15 to 25 weight percent Cr, 3 to 6 weight percent Al, optionally 0.3 to 1.0 weight percent Y and the balance Fe, and having an oxidized foil surface comprising densely spaced oxide whiskers, said substrate being formable into the desired shape of the structural member,
• applying a coating comprising gamma alumina to the whisker-covered surface, and
• impregnating said alumina coating with a catalyst to form a spall-resistant, catalytically coated foil that is formable into the desired structural member.

A metal foil formed of a ferritic stainless steel alloy containing aluminum and having a surface that is substantially covered by densely spaced alumina whiskers.

A catalyst-bearing structure for treating gases brought into contact with the surface thereof, said structure comprising

• a metal foil composed of an aluminum-containing ferritic stainless steel alloy and having an oxidized surface comprising densely spaced oxide whiskers, and
• a coating overlying the oxide whisker surface and tightly bonded to the foil by said whiskers, said coating comprising a gas-treating catalyst.

A catalytic converter for the treatment of automotive exhaust gases and comprising a foil structural member having gas-conveying passageways therethrough, said member comprising

• an aluminum-containing ferritic stainless steel alloy foil having a surface that is substantially covered by densely spaced oxide whiskers, and
• a catalyst-bearing coating overlying the oxide whisker surface, whereby said whiskers improve adhesion of said coating to said foil.

A catalytic converter suitable for treating of automotive exhaust gases, said converter comprising a wound foil member having gas-conveying passageways therethrough and comprising

• a metal foil composed of a ferritic stainless steel alloy comprising 15 to 25 weight percent Cr, 3 to 6 weight percent Al, optionally 0.3 to 1.0 weight percent Y and the balance Fe,
• said foil having an oxidized surface that is substantially covered by densely spaced, high aspect ratio alumina whiskers, and
• a catalyst-impregnated alumina coating applied to said whisker-covered surface and tightly bonded to the foil by the whiskers.

A metal foil formed of a ferritic stainless steel alloy containing aluminum and having an oxidized surface comprising densely spaced whiskers and suitable for receiving and tightly bonding an applied coating.

A metal foil formed of a ferritic stainless steel alloy containing aluminum and having an oxidized surface that is formed of and substantially covered by densely spaced whiskers on the order of 3 microns high.