High impact strength power metal part and method for making same

Claim 2

A copper infiltrated ferrous powder metal part infiltrated with copper or a copper alloy characterized as having after infiltration an overall density of at least 7.50 g/cm 3 and a diffusion depth of copper into the steel matrix of less than about 4 micrometers as determined by chemical etching or less than about 8 micrometers as determined by electron dispersive X-ray analysis, wherein said ferrous metal is plain carbon steel having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 3

The metal part of claim 1 wherein said diffusion depth is less than about 3 micrometers as determined by chemical etching or less than about 5 micrometers as determined by electron dispersive X-ray analysis.

Claim 4

The metal part of claims 1 or 2 wherein said ferrous metal is plain carbon steel having a combined carbon content in the range of about 0.25% to about 1.05%.

Claim 5

The metal part of claim 1 having an overall density of at least 7.50 g/cm 3 , a residual uninfiltrated porosity of not more than 10 volume percent, and a maximum pore size of the residual uninfiltrated porosity of less than about 120 micrometers, said porosity and pore size values being taken from the worst field of view in a functionally critical area of said metal part.

Claim 6

The metal part of claim 4 having a Charpy unnotched impact strength of greater than 50 ft. lbs. and an ultimate tensile strength greater than 60 ksi.

Claim 7

The metal part of claim 1 having an impact strength, as measured by the unnotched Charpy test, of greater than 13 ft. lbs., and a tensile strength of greater than 125 ksi.

Claim 8

A process for infiltrating ferrous powder metal parts with a copper or copper alloy infiltrant to yield an impact strength as measured by the unnotched Charpy test, of greater than 50 ft. lbs., and an ultimate tensile strength of greater than 60 ksi, comprising the steps of: (a) pressing a ferrous powder metal to a density of at least about 80% of theoretical density; (b) sintering said powder metal; and (c) infiltrating said powder metal with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis, wherein said ferrous metal is plain carbon steel having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 9

A process for infiltrating ferrous powder metal parts with a copper or copper alloy infiltrant to yield an impact strength as measured by the unnotched Charpy test, of greater than 50 ft. lbs., and an ultimate tensile strength of greater than 60 ksi, comprising the steps of: (a) pressing a ferrous powder metal to a density of at least about 80% of theoretical density; (b) sintering said powder metal; and (c) infiltrating said powder metal with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis, wherein said ferrous metal is plain carbon steel having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 10

The process of claim 7 wherein said sintering is carried out under vacuum conditions or under a hydrogen atmosphere.

Claim 11

The process of claim 8 including the step of heat treating said metal part by austenitizing and tempering.

Claim 12

The process of claims 8 or 9 wherein said ferrous metal is plain carbon steel having a combined carbon content in the range of about 0.25% to about 1.05%.

Claim 13

The process of claims 8 or 9 wherein said infiltrant is copper alloyed with an alloying constituent selected from the group consisting of iron, tin, zinc, silver, lithium, silicon, manganese, chromium, zirconium, and combinations thereof.

Claim 14

A copper infiltrated ferrous powder metal part as claimed in claim 1 prepared by the steps of (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said powder metal to a density of at least about 80% of theoretical density; (c) sintering said powder metal; and (d) infiltrating said powder metal with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis.

Claim 15

A copper infiltrated ferrous powder metal part as claimed in claim 1 prepared by the steps of (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said powder metal to a density of at least about 80% of theoretical density; (c) sintering said powder metal under vacuum sintering conditions or a hydrogen atmosphere using conditions effective for sintering; and (d) infiltrating said powder metal also under vacuum sintering conditions or a hydrogen atmosphere using conditions effective for infiltrating, with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis.

Claim 16

The copper infiltrated ferrous powder metal part of claim 1 prepared by presintering said metal part followed by copper infiltration.

Claim 17

A copper infiltrated ferrous powder metal part infiltrated with copper or a copper alloy characterized as having after infiltration an overall density of at least 7.50 g/cm 3 and a diffusion depth of copper into the steel matrix of less than about 4 micrometers as determined by chemical etching or less than about 8 micrometers as determined by electron dispersive X-ray analysis, wherein said ferrous metal is a low alloy or tool steel.

Claim 18

A copper infiltrated ferrous powder metal part infiltrated with copper or a copper alloy characterized as having after infiltration an overall density of at least 7.50 g/cm 3 and a diffusion depth of copper into the steel matrix of less than about 4 micrometers as determined by chemical etching or less than about 8 micrometers as determined by electron dispersive X-ray analysis, wherein said ferrous metal is a low alloy or tool steel.

Claim 19

The metal part of claim 15 wherein said ferrous metal has a boron content in the range of about 0.1-0.2%.

Claim 20

A process for infiltrating ferrous powder metal parts with a copper or copper alloy infiltrant to yield an impact strength as measured by the unnotched Charpy test, of greater than 50 ft. lbs., and an ultimate tensile strength of greater than 60 ksi, comprising the steps of: (a) pressing a ferrous powder metal to a density of at least about 80% of theoretical density; (b) sintering said powder metal; and (c) infiltrating said powder metal with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis, wherein said ferrous metal is a low alloy or tool steel.

Claim 21

A process for infiltrating ferrous powder metal parts with a copper or copper alloy infiltrant to yield an impact strength as measured by the unnotched Charpy test, of greater than 50 ft. lbs., and an ultimate tensile strength of greater than 60 ksi, comprising the steps of: (a) pressing a ferrous powder metal to a density of at least about 80% of theoretical density; (b) sintering said powder metal; and (c) infiltrating said powder metal with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis, wherein said ferrous metal is a low alloy or tool steel.

Claim 22

The process of claim 17 wherein said ferrous metal has a boron content in the range of about 0.1-0.2%.

Claim 23

A copper infiltrated ferrous powder metal part as claimed in claim 15 prepared by the steps of: (a) filling a die with ferous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said powder metal to a density of at least about 80% of theoretical density; (c) sintering said powder metal; and (d) infiltrating said powder metal with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis.

Claim 24

A copper infiltrated ferrous powder metal part as claimed in claim 15 prepared by the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said powder mtal to a density of at least about 80% of theoretical density; (c) sintering said power metal under vacuum sintering conditions or a hydrogen atmosphere using conditions effective for sintering; and (d) infiltrating said powder metal also under vacuum sintering conditions or a hydrogen atmosphere using conditions effective for infiltrating, with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis.

Claim 25

The process of claim 7 wherein the sintering and infiltrating are carried out simultaneously.

Claim 26

The metal parts of claims 12 or 13 wherein the sintering and infiltrating are carried out simultaneoulsy.

Claim 27

A process for infiltrating ferrous powder metal parts witha copper or copper alloy infiltrant to yield an impact strength, as measured by the unnotched Charpy test, of greater than 50 foot pounds, and an ultimate tensile strength of greater than 46 ksi in the as-infiltrated condition, comprising the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said ferrous powder metal to a density of at least about 80% of theoretical density; (c) sintering said ferrous powder metal under an atmosphere of an inert gas or a reducing gas using conditions effective for sintering; (d) infiltrating said ferrous powder metal with a copper or copper alloy infiltrant under an atmosphere of an inert gas with or without a reducing gas and assuring that th edepth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis; (e) the filling, pressing, sintering and infiltrating conditions being effective to provide a powder metal part having a residual uninfiltrated porosity and a maximum pore size of residual uninfiltrated porosity, as taken from a worst field of view in a functionally critical area of said metal part, of less than about 7 volume percent and 125 micrometers, respectively; said ferrous powder metal following infiltration having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 28

A process for infiltrating ferrous powder metal parts witha copper or copper alloy infiltrant to yield an impact strength, as measured by the unnotched Charpy test, of greater than 50 foot pounds, and an ultimate tensile strength of greater than 46 ksi in the as-infiltrated condition, comprising the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said ferrous powder metal to a density of at least about 80% of theoretical density; (c) sintering said ferrous powder metal under an atmosphere of an inert gas or a reducing gas using conditions effective for sintering; (d) infiltrating said ferrous powder metal with a copper or copper alloy infiltrant under an atmosphere of an inert gas with or without a reducing gas and assuring that th edepth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis; (e) the filling, pressing, sintering and infiltrating conditions being effective to provide a powder metal part having a residual uninfiltrated porosity and a maximum pore size of residual uninfiltrated porosity, as taken from a worst field of view in a functionally critical area of said metal part, of less than about 7 volume percent and 125 micrometers, respectively; said ferrous powder metal following infiltration having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 29

A process as defined in claim 23 wherein the inert gas contains hydrogen.

Claim 30

A process as defined in claim 23 wherein the reducing gas is dissociated ammonia.

Claim 31

A process as defined in claim 23 wherein the reducing gas is "synthetic" nitrogen.

Claim 32

A process as defined in claim 23 wherein the inert gas is selected frm argon, helium and nitrogen.

Claim 33

A process as defined in claim 25 wherein the sintering step is carried out under vacuum.

Claim 34

A process as defined in claim 25 wherein the infiltrating step is carried out under vacuum.

Claim 35

A copper infiltrated ferrous powder metal part prepared by the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distributionin said die; (b) pressing said powder metal to a density of at least about 80% of theoretical density; (c) sintering said powder metal under an inert or reducing gas atmosphere using conditions effective for sintering; and (d) infiltrating said powder metal also under an inert or reducing gas atmosphere using conditions effective for infiltrating, with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis.

Claim 36

A copper infiltrated ferrous powder metal part prepared by the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distributionin said die; (b) pressing said powder metal to a density of at least about 80% of theoretical density; (c) sintering said powder metal under an inert or reducing gas atmosphere using conditions effective for sintering; and (d) infiltrating said powder metal also under an inert or reducing gas atmosphere using conditions effective for infiltrating, with a copper or copper alloy infiltrant assuring that the depth of copper diffusion into the steel matrix as measured by chemical etching is less than about 4 micrometers, or less than about 8 micrometers when determined by electron dispersive X-ray analysis.

Claim 37

The metal parts of claim 30 wherein the sintering and infiltrating are carried out simultaneously.

Claim 38

The metal parts of claim 30 wherein the reducing gas atmosphere is dissociated ammonia.

Claim 39

The metal parts of claim 30 wherein the reducing gas atmosphere is "synthetic" nitrogen.

Claim 40

The metal parts of claim 30 wherein the inert gas is selected from argon, helium, and nitrogen.

Claim 41

The metal parts of claim 30 wherein the sintering step is carried out under vacuum.

Claim 42

The metal parts of claim 30 wherein the infiltrating step is carried out under vacuum.

Claim 43

A process for infiltrating ferrous powder metal parts with a copper or copper alloy infiltrant to yield an impact strength, as measured by the unnotched Charpy test, of greater than 50 foot pounds, and an ultimate tensile strength of greater than 46 ksi, in the as-infiltrated condition, comprising the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said ferrous powder metal to a density of at least about 80% of theoretical density; (c) sintering sid ferrous powder metal under an inert gas atmosphere at ambient pressure using sintering conditions; (d) infiltrating said ferrous powder metal with a copper or copper alloy infiltrant under an inert gas atmosphere at ambient pressure using infiltrating conditions; (e) the filling, pressing, sintering and infiltrating conditions being effective to provide a powder metal part having a residual uninfiltrated porosity and a maximum pore size of residual uninfiltrated porosity, as taken from a worst field of view in a functionally critical area of said metal part, of less than about 7 volume percent and 125 micrometers, respectively; said ferrous powder metal following infiltration having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 44

A process for infiltrating ferrous powder metal parts with a copper or copper alloy infiltrant to yield an impact strength, as measured by the unnotched Charpy test, of greater than 50 foot pounds, and an ultimate tensile strength of greater than 46 ksi, in the as-infiltrated condition, comprising the steps of: (a) filling a die with ferrous powder metal to achieve uniform powder metal distribution in said die; (b) pressing said ferrous powder metal to a density of at least about 80% of theoretical density; (c) sintering sid ferrous powder metal under an inert gas atmosphere at ambient pressure using sintering conditions; (d) infiltrating said ferrous powder metal with a copper or copper alloy infiltrant under an inert gas atmosphere at ambient pressure using infiltrating conditions; (e) the filling, pressing, sintering and infiltrating conditions being effective to provide a powder metal part having a residual uninfiltrated porosity and a maximum pore size of residual uninfiltrated porosity, as taken from a worst field of view in a functionally critical area of said metal part, of less than about 7 volume percent and 125 micrometers, respectively; said ferrous powder metal following infiltration having a combined carbon content in the range of about 0.15% to about 1.25%.

Claim 45

The process of claim 37 wherein the sintering and infiltrating are carried out simultaneously.