Oxidation resistant cobalt base alloy

Claim 2

In cobalt base superalloys of the type which consist essentially of from 10% to 30% of a material chosen from the group consisting of nickel and iron and mixtures thereof, from 5% to 15% of a material chosen from the group consisting of tungsten and molybdenum and mixtures thereof, from 1% to 5% of a material chosen from the group consisting of tantalum and columbium and mixtures thereof, from 0.05% to 0.06% carbon, chromium, aluminum, balance cobalt, the improvement which comprises: controlling the chromium level between about 18 and about 30%, and controlling the aluminum level between about 3.5 and 8.0% so as to promote the formation of an alumina layer under oxidizing conditions; providing hafnium in an amount from about 0.5 to about 2.0% and yttrium in an amount from about 0.02 to about 0.1%, to promote adherence of the alumina layer; whereby exceptional high temperature oxidation and corrosion resistance results.

Claim 3

A combustion chamber for use in gas turbine engines fabricated from a wrought material which consists essentially of: from about 18 to about 27% Cr, from about 10 to about 20% of a material selected from the group consisting of Fe and Ni and mixtures thereof, from about 8.0 to about 12.0% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 3.5 to about 5.0% Al, from about 0.5 to about 2.0% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, from about 0.25 to about 0.45% C, up to about 0.5% B, balance essentially Co.

Claim 4

A combustion chamber for use in gas turbine engines fabricated from a wrought material which consists essentially of: from about 18 to about 27% Cr, from about 10 to about 20% of a material selected from the group consisting of Fe and Ni and mixtures thereof, from about 8.0 to about 12.0% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 3.5 to about 5.0% Al, from about 0.5 to about 2.0% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, from about 0.25 to about 0.45% C, up to about 0.5% B, balance essentially Co.

Claim 5

An oxidation and corrosion resistant cobalt base superalloy consisting essentially of: from about 18 to about 30% Cr, from about 10 to about 30% of a material chosen from the group consisting of Ni and Fe, and mixtures thereof, from about 5 to about 15% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 1 to about 5% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.05 to about 0.6% C, from about 3.5 to about 8.0% Al, from about 0.5 to about 2% Hf, up to about 0.5% Ti, from about 0.02 to about 0.1% Y up to about 0.5% B, balance essentially Co.

Claim 6

An oxidation and corrosion resistant cobalt base superalloy consisting essentially of: from about 18 to about 30% Cr, from about 10 to about 30% of a material chosen from the group consisting of Ni and Fe, and mixtures thereof, from about 5 to about 15% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 1 to about 5% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.05 to about 0.6% C, from about 3.5 to about 8.0% Al, from about 0.5 to about 2% Hf, up to about 0.5% Ti, from about 0.02 to about 0.1% Y up to about 0.5% B, balance essentially Co.

Claim 7

A superalloy as in claim 3, useful for production in wrought form, which consists essentially of: from about 18 to about 27% Cr, from about 10 to about 20% of a material chosen from the group consisting of Ni and Fe and mixtures thereof, from about 8 to about 12% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.25 to about 0.45% C, from about 3.5 to about 5.0% Al, from about 0.5 to about 2.0% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, up to about 0.5% B, balance essentially Co.

Claim 8

A superalloy as in claim 4, which consists essentially of: from about 18 to about 25% Cr, from about 13 to about 17% Ni from about 8 to about 10% W from about 2 to about 4% Ta from about 3.7 to about 4.6% Al.

Claim 9

A fabricable wrought cobalt base superalloy intermediate article useful for the production of further articles for use where strength and resistance to oxidation/corrosion at elevated temperature is required, said wrought intermediate article consisting essentially of, from about 18 to about 27% Cr, from about 10 to about 20% of a material chosen from the group consisting of Ni and Fe, and mixtures thereof, from about 8 to about 12% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.25 to about 0.45% C, from about 3.5 to about 5% Al, from about 0.5 to about 2% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, up to about 0.5% B, balance essentially Co.

Claim 10

A fabricable wrought cobalt base superalloy intermediate article useful for the production of further articles for use where strength and resistance to oxidation/corrosion at elevated temperature is required, said wrought intermediate article consisting essentially of, from about 18 to about 27% Cr, from about 10 to about 20% of a material chosen from the group consisting of Ni and Fe, and mixtures thereof, from about 8 to about 12% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.25 to about 0.45% C, from about 3.5 to about 5% Al, from about 0.5 to about 2% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, up to about 0.5% B, balance essentially Co.

Claim 11

A process for producing a fabricable wrought cobalt base superalloy sheet including the steps of: a. providing alloy constituents which consist essentially of: from about 18 to about 27% Cr, from about 10 to about 20% of a material chosen from the group consisting of Ni and Fe, and mixtures thereof, from about 8 to about 12% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.25 to about 0.45% C, from about 3.5 to about 5% Al, from about 0.5 to about 2% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, up to about 0.5% B, balance essentially Co; b. melting the constituents under vacuum and casting the melted constituents into ingots, c. electro slag remelting the cast ingots, d. homogenizing the remelted ingots at a temperature of from about 2200° to 2300° F for from about 12 to about 36 hours, e. forging the homogenized ingots at a starting temperature of from about 2100° to about 2200° F, f. hot rolling the forged material at a starting temperature of from about 2100° to about 2200° F, g. solution heat treating the hot rolled material at a temperature of from about 2200° to about 2300° F for a time of from about 15 minutes to about 16 hours.

Claim 12

A process for producing a fabricable wrought cobalt base superalloy sheet including the steps of: a. providing alloy constituents which consist essentially of: from about 18 to about 27% Cr, from about 10 to about 20% of a material chosen from the group consisting of Ni and Fe, and mixtures thereof, from about 8 to about 12% of a material chosen from the group consisting of W and Mo and mixtures thereof, from about 2 to about 4% of a material chosen from the group consisting of Ta and Cb and mixtures thereof, from about 0.25 to about 0.45% C, from about 3.5 to about 5% Al, from about 0.5 to about 2% Hf, up to about 0.5% Ti, from about 0.02 to about 0.07% Y, up to about 0.5% B, balance essentially Co; b. melting the constituents under vacuum and casting the melted constituents into ingots, c. electro slag remelting the cast ingots, d. homogenizing the remelted ingots at a temperature of from about 2200° to 2300° F for from about 12 to about 36 hours, e. forging the homogenized ingots at a starting temperature of from about 2100° to about 2200° F, f. hot rolling the forged material at a starting temperature of from about 2100° to about 2200° F, g. solution heat treating the hot rolled material at a temperature of from about 2200° to about 2300° F for a time of from about 15 minutes to about 16 hours.