Method for making an abradable article

Claim 2

In a method of making an article having an environmentally resistant, abradable surface portion, the steps of: (a) providing a powder mixture of two powdered alloys each having a base of elements M, Cr and Al in which M is the least one element selected from the group consisting of Co and Ni, the mixture having a total mixture composition consisting essentially of, by weight, 10-35% Cr, 4-10% Al, from a small but effective amount up to about 0.09% Y, 2-6% Si with the balance M and incidental impurities, and further characterized by the substantial absence of B; a first of the powdered alloys having a solidus and a liquidus, consisting of 50-70 wt% of the mixture and having a melting range higher than a second of the powdered alloys; the first alloy characterized by the substantial absence of Si and the presence of Y in an amount, up to 0.15 wt.%, which will provide the Y content in the total mixture composition; the second of the powdered alloys having a solidus and a liquidus, consisting essentially of the balance of the mixture, being characterized by the substantial absence of Y, and consisting essentially of, by weight, 8-12% Si, 1.5-4% Al, 10-30% Cr, with the balance M and incidental impurities; (b) compacting the mixture at a compacting temperature below the solidus of the second of the powdered alloys to provide a preform; (c) disposing the preform on a surface of the article; (d) heating the preform and surface in a non-oxidizing atmosphere at a processing temperature above the liquidus temperature of the second powdered alloy and below the liquidus temperature of the first powdered alloy of the mixture; and (e) holding the preform and surface at the processing temperature for a time sufficient to liquid phase sinter the powder mixture, to interdiffuse elements of the first and second powders, and to bond the preform to the article surface.

Claim 3

The method of claim 1 in which the powder mixture is provided to generate a preform after compacting, and in which the processing temperature is in the range of 980°-1100° C.

Claim 4

The method of claim 1 in which, after compacting the mixture to provide a preform and before disposing the preform on the surface, the preform is presintered in a non-oxidizing atmosphere at a presintering temperature below the solidus of the second of the powdered alloys.

Claim 5

In a method of repairing an outer portion of an article comprising the steps of: removing at least part of the outer portion of the article to provide a repair receiving surface; selecting from the powder mixture of claim 1 a replacement powder mixture which will provide a replacement outer portion having a solidus above the incipient melting temperature of the article; disposing the replacement powder mixture on the repair receiving surface; heating the replacement mixture and repair receiving surface in a non-oxidizing atmosphere at a processing temperature above the liquidus temperature of the second powdered alloy and below the liquidus temperature of the first powdered alloy of the mixture; and holding the replacement mixture and repair receiving surface at the processing temperature for a time sufficient to liquid phase sinter the powder mixture, to interdiffuse elements of the first and second powders, and to bond the replacement mixture to the repair receiving surface.

Claim 6

The method of claim 4 in which the replacement powder mixture is compacted at a compacting temperature below the solidus of the second of the powdered alloys to provide a preform, prior to disposing the replacement mixture on the repair receiving surface.

Claim 7

The method on claim 4 in which the replacement powder mixture is preliminarily bonded together into tape form with a bonding mixture which decomposes without substantial residue at the processing temperature.

Claim 8

The method of claim 2 wherein the thickness of the preform after compacting the powder mixture is about 0.1".

Claim 9

In a method of making an article having an inner portion of a superalloy selected from a group consisting of Co-base and Ni-base superalloys and having an incipient melting temperature, and an environmentally resistant, abradable outer portion metallurgically bonded with the inner portion, the outer portion consolidated and liquid phase sintered from a powder mixture of two powdered alloys each comprising a base of elements M, Cr and Al in which M is at least one element selected from a group consisting of Co and Ni, the mixture having a total mixture composition consisting essentially of, by weight, 10-35% Cr, 4-10% Al, from a small but effective amount up to about 0.09% Y, 2-6% Si with the balance M and incidental impurities, and further characterized by the substantial absence of B, a first of said powdered alloys consisting of 50-70 wt% of said powdered mixture characterized by the substantial absence of Si and the presence of Y in an amount, up to 0.15 wt.%, which will provide the Y content in the total mixture composition having a solidus and a liquidus, and having a melting range higher than a second of said powdered alloys, a second of said powdered alloys, consisting essentially of the balance of said mixture, being characterized by the substantial absence of Y, and consisting essentially of, by weight, 8-12% Si, 1.5-4% Al, 10-30% Cr, with the balance M and incidental impurities, the steps of: compacting the powder mixture of the outer portion at a compacting temperature below the solidus of the second of the powdered alloys to provide a preform; disposing the preform on a surface of the inner portion; heating the preform and surface in a non-oxidizing atmosphere at a processing temperature above the liquidus temperature of the second powdered alloy and below the liquidus temperature of the first powdered alloy of the mixture; and holding the preform and the surface at the processing temperature for a time sufficient to liquid phase sinter the powder mixture, to interdiffuse elements of the first and second powders, and to bond the preform to the surface of the inner portion.

Claim 10

In a method of making an article having an inner portion of a superalloy selected from a group consisting of Co-base and Ni-base superalloys and having an incipient melting temperature, and an environmentally resistant, abradable outer portion metallurgically bonded with the inner portion, the outer portion consolidated and liquid phase sintered from a powder mixture of two powdered alloys each comprising a base of elements M, Cr and Al in which M is at least one element selected from a group consisting of Co and Ni, the mixture having a total mixture composition consisting essentially of, by weight, 10-35% Cr, 4-10% Al, from a small but effective amount up to about 0.09% Y, 2-6% Si with the balance M and incidental impurities, and further characterized by the substantial absence of B, a first of said powdered alloys consisting of 50-70 wt% of said powdered mixture characterized by the substantial absence of Si and the presence of Y in an amount, up to 0.15 wt.%, which will provide the Y content in the total mixture composition having a solidus and a liquidus, and having a melting range higher than a second of said powdered alloys, a second of said powdered alloys, consisting essentially of the balance of said mixture, being characterized by the substantial absence of Y, and consisting essentially of, by weight, 8-12% Si, 1.5-4% Al, 10-30% Cr, with the balance M and incidental impurities, the steps of: compacting the powder mixture of the outer portion at a compacting temperature below the solidus of the second of the powdered alloys to provide a preform; disposing the preform on a surface of the inner portion; heating the preform and surface in a non-oxidizing atmosphere at a processing temperature above the liquidus temperature of the second powdered alloy and below the liquidus temperature of the first powdered alloy of the mixture; and holding the preform and the surface at the processing temperature for a time sufficient to liquid phase sinter the powder mixture, to interdiffuse elements of the first and second powders, and to bond the preform to the surface of the inner portion.

Claim 11

The method of claim 8 in which the article formed is a turbine shroud.

Claim 12

The method of claim 8 in which the processing temperature is at least about 50° C. above the liquidus of the second powdered alloy and below the incipient melting temperature of the inner portion of the article.

Claim 13

The method of claim 8 wherein the outer portion of the article has a thickness of at least about 0.05".