Iron-based sintered powder metal for wear resistant applications
A powder metal material comprises pre-alloyed iron-based powder including carbon present in an amount of 0.25 to 1.50% by weight of the pre-alloyed iron-based powder. Graphite is admixed in an amount of 0.25 to 1.50% by weight of the powder metal material. The admixed graphite includes particles finer than 200 mesh in an amount greater than 90.0% by weight of the admixed graphite. Molybdenum disulfide is admixed in an amount of 0.1 to 4.0% by weight of the powder metal material, copper is admixed in an amount of 1.0 to 5.0% by weight of the powder metal material, and the material is free of phosphorous. The powder metal material is then compacted and sintered at a temperature of 1030 to 1150° C. At least 50% of the admixed graphite of the starting powder metal material remains as free graphite after sintering.
1. A method of forming a powder metal material comprising the steps of:
obtaining a powder metal mixture of pre-alloyed iron-based powder, admixed graphite powder, admixed molybdenum disulfide, and admixed copper, wherein at least about 90.0% by weight of the admixed graphite powder consists of particles having a U.S. standard sieve designation finer than 200 mesh, and the admixed graphite is present in an amount of about 0.25 to about 1.50% by weight of the powder metal mixture; and
pre-alloying the iron-based powder with carbon in an amount of at least 0.25% by weight of the pre-alloyed iron-based powder to retain at least about 50% of the admixed graphite as free graphite after sintering the powder metal mixture, wherein the pre-alloyed iron-based powder includes a pearlitic structure, and the powder metal mixture is free of phosphorous.
2. A method as set forth in claim 1 , wherein the powder metal mixture includes the admixed molybdenum disulfide in an amount of about 0.1 to about 4.0% by weight of the powder metal mixture.
3. A method as set forth in claim 1 , wherein the powder metal mixture includes the admixed copper in an amount of about 1.0 to about 5.0% by weight of the powder metal mixture.
4. A method as set forth in claim 1 , wherein the powder metal mixture includes the admixed molybdenum disulfide in an amount of about 0.1 to about 4.0% by weight of the powder metal mixture; and
the powder metal mixture includes the admixed copper in an amount of about 1.0 to about 5.0% by weight of the powder metal mixture.
5. A method as set forth in claim 1 , wherein the carbon is present in an amount of 0.25 to 1.50% by weight of the pre-alloyed iron-based powder, the admixed molybdenum disulfide is present in an amount of about 0.1 to about 4.0% by weight of the powder metal mixture, and the admixed copper is present in an amount of about 1.0 to about 5.0% by weight of the powder metal mixture.
6. A method of forming a sintered powder metal material comprising the steps of:
obtaining a powder metal mixture of pre-alloyed iron-based powder including carbon in an amount of at least 0.25% by weight of the pre-alloyed iron-based powder, admixed graphite powder, admixed molybdenum disulfide, and admixed copper, wherein at least about 90.0% by weight of the admixed graphite powder consists of particles having a U.S. standard sieve designation finer than 200 mesh, and the admixed graphite is present in an amount of about 0.25 to about 1.50% by weight of the powder metal mixture; and
retaining at least about 50% of the admixed graphite as free graphite after sintering the powder metal mixture, and wherein the pre-alloyed iron-based powder includes a pearlitic structure, and the powder metal mixture is free of phosphorous.
7. A method as set forth in claim 6 including pressing the powder metal mixture to a density of about 6.40 to about 7.10 g/cm 3 .
8. A method as set forth in claim 6 wherein said retaining includes compacting and sintering the powder metal mixture.
9. A method as set forth in claim 8 wherein said sintering occurs at a temperature of about 1030 to about 1150° C.
10. A method as set forth in claim 8 wherein said sintering occurs in an atmosphere of hydrogen and nitrogen.
11. A method as set forth in claim 8 wherein said sintering occurs in an atmosphere of dissociated ammonia.
12. A method as set forth in claim 6 , wherein the powder metal mixture includes the admixed molybdenum disulfide in an amount of about 0.1 to about 4.0% by weight of the powder metal mixture and the admixed copper in an amount of about 1.0 to about 5.0% by weight of the powder metal mixture.