Copper coated, iron-carbon eutectic alloy powders

Claim 1

A method for preventing solid state carbon diffusion in powder metallurgy techniques at elevated temperatures, comprising: a. prepare at least a first hypoeutectic carbon iron based powder collection and a second hypereutectic carbon metal powder collection, each containing dissolved carbon with said first collection having a carbon content exceeding the carbon content of said second powder collection by at least 0.5% by weight, b. impart a thin envelope about substantially all particles of one of said powder collections, said envelope being comprised of a metal having a melting point lower than but substantially close to the melting point of said one powder collection, said metal being characterized by having a diffusivity for carbon therethrough in the solid state and being completely soluble in said one powder collection when the latter is in the molten state, said diffusivity being such that the carbon content of said second powder collection will not recede to below the eutectic point for said second collection during substantially the time involved in heating said second collection to the liquidus temperature, said envelope metal constituting from .1-1.5% by weight of said one powder collection, c. intimately and homogeneously mix said powder collection to form an admixture, and d. heat said admixture to provide an increase in temperature of the collections up to substantially the initial liquidus temperature for said first powder collection, said envelope preventing a carbon diffusion from one collection to the other during said temperature increase below the liquidus temperature, and hold said heated condition at about the liquidus temperature for said one powder collection to dissolve said envelope metal and to permit diffusion alloying and carbon exchange between said powder collections.

Claim 2

A method for preventing solid state carbon diffusion in powder metallurgy techniques at elevated temperatures, comprising: a. prepare at least a first hypoeutectic carbon iron based powder collection and a second hypereutectic carbon metal powder collection, each containing dissolved carbon with said first collection having a carbon content exceeding the carbon content of said second powder collection by at least 0.5% by weight, b. impart a thin envelope about substantially all particles of one of said powder collections, said envelope being comprised of a metal having a melting point lower than but substantially close to the melting point of said one powder collection, said metal being characterized by having a diffusivity for carbon therethrough in the solid state and being completely soluble in said one powder collection when the latter is in the molten state, said diffusivity being such that the carbon content of said second powder collection will not recede to below the eutectic point for said second collection during substantially the time involved in heating said second collection to the liquidus temperature, said envelope metal constituting from .1-1.5% by weight of said one powder collection, c. intimately and homogeneously mix said powder collection to form an admixture, and d. heat said admixture to provide an increase in temperature of the collections up to substantially the initial liquidus temperature for said first powder collection, said envelope preventing a carbon diffusion from one collection to the other during said temperature increase below the liquidus temperature, and hold said heated condition at about the liquidus temperature for said one powder collection to dissolve said envelope metal and to permit diffusion alloying and carbon exchange between said powder collections.

Claim 6

A method making iron alloys, comprising: a. providing a low carbon iron base powder and an iron alloy powder containing essentially a eutectic amount of carbon, b. thinly coat the surfaces of each particle of at least said alloy powder with a metal effective to act as a substantial barrier against carbon diffusion when said alloy powder is in the solid state, said barrier metal having a melting point lower than said iron alloy powder, c. intimately and homogeneously blend said base and coated alloy powders, d. compact said blended powders to a self-supporting green strength, and e. heat said compact to the liquidus temperature of said alloy powder and maintain said liquidus temperature for a period of time to permit carbon and alloy diffusion to take place between the powders to a stabilized value.

Claim 7

A method making iron alloys, comprising: a. providing a low carbon iron base powder and an iron alloy powder containing essentially a eutectic amount of carbon, b. thinly coat the surfaces of each particle of at least said alloy powder with a metal effective to act as a substantial barrier against carbon diffusion when said alloy powder is in the solid state, said barrier metal having a melting point lower than said iron alloy powder, c. intimately and homogeneously blend said base and coated alloy powders, d. compact said blended powders to a self-supporting green strength, and e. heat said compact to the liquidus temperature of said alloy powder and maintain said liquidus temperature for a period of time to permit carbon and alloy diffusion to take place between the powders to a stabilized value.

Claim 13

A method of making powdered parts, comprising: a. providing an iron-carbon-alloy powder in a particle size range of -100 +325 having a hypereutectic amount of carbon, b. coating said iron-carbon-alloy powder with copper by subjection to abrasive action of copper elements impacted with the particles of said iron-carbon-alloy powder, c. mixing said coated iron-carbon-alloy powder with a base iron powder having a hypoeutectic amount of carbon and having a lower carbon content than said iron-carbon-alloy powder, d. compacting said mechanically mixed powders under ambient temperature conditions and under a pressure of 30 tsi to a density of 6.6 g./cc. rendering a compact having a green strength of at least 1200 psi, e. subjecting said compact to liquid phase sintering under a protective atmosphere at a temperature in the range of 2060°-2100° F for a period of 20 minutes, f. allowing said sintered product to cool, and g. reheating said cooled sintered shape and hot working said shape at a temperature of about 1800° to a desired configuration and to a density of substantially 100%.

Claim 14

A method of making powdered parts, comprising: a. providing an iron-carbon-alloy powder in a particle size range of -100 +325 having a hypereutectic amount of carbon, b. coating said iron-carbon-alloy powder with copper by subjection to abrasive action of copper elements impacted with the particles of said iron-carbon-alloy powder, c. mixing said coated iron-carbon-alloy powder with a base iron powder having a hypoeutectic amount of carbon and having a lower carbon content than said iron-carbon-alloy powder, d. compacting said mechanically mixed powders under ambient temperature conditions and under a pressure of 30 tsi to a density of 6.6 g./cc. rendering a compact having a green strength of at least 1200 psi, e. subjecting said compact to liquid phase sintering under a protective atmosphere at a temperature in the range of 2060°-2100° F for a period of 20 minutes, f. allowing said sintered product to cool, and g. reheating said cooled sintered shape and hot working said shape at a temperature of about 1800° to a desired configuration and to a density of substantially 100%.

Claim 18

A method of making powder parts comprising: a. preparing a hypereutectic carbon master alloy powder having the particles thereof provided with alloyed iron-carbon constituent, each particle having a thin protective coating of copper present in an amount no greater than 1.5% of the total master alloy powder, b. mechanically mixing said master alloy powder with a base iron powder having a carbon content less than 0.3% carbon, c. compacting said mechanical mixture to form a compact with a density of about d. sinter said compact in a protective atmosphere and at a temperature in the range of 2060°-2100° F, and said mechanical mixture having a liquidus in the range of 2066°-2100° F and a melting range less than 50° F.

Claim 19

A method of making powder parts comprising: a. preparing a hypereutectic carbon master alloy powder having the particles thereof provided with alloyed iron-carbon constituent, each particle having a thin protective coating of copper present in an amount no greater than 1.5% of the total master alloy powder, b. mechanically mixing said master alloy powder with a base iron powder having a carbon content less than 0.3% carbon, c. compacting said mechanical mixture to form a compact with a density of about d. sinter said compact in a protective atmosphere and at a temperature in the range of 2060°-2100° F, and said mechanical mixture having a liquidus in the range of 2066°-2100° F and a melting range less than 50° F.