Iron base sintered alloy having highly densified and hardened surface, and producing method thereof

1 . An iron base sintered alloy having highly densified and hardened surface, comprising:

a surface layer portion of the iron base sintered alloy having a thickness in a range of 1 μm to 2 mm from a surface of the iron base sintered alloy; and

an inner portion of the iron base sintered alloy located inside the iron base sintered alloy surface layer portion,

wherein the iron base sintered alloy surface layer portion contains potassium K.

2 . An iron base sintered alloy having highly densified and hardened surface, comprising:

an iron base sintered alloy surface layer portion; and

an iron base sintered alloy inner portion,

wherein the iron base sintered alloy surface layer portion contains sodium Na.

3 . An iron base sintered alloy having highly densified and hardened surface, comprising:

an iron base sintered alloy surface layer portion; and

an iron base sintered alloy inner portion, wherein the iron base sintered alloy surface layer portion contains K and Na.

4 . The iron base sintered alloy according to claim 1 ,

wherein the iron base sintered alloy surface layer portion contains K in an average concentration of 0.0001 to 1 mass %.

5 . The iron base sintered alloy according to claim 2 ,

wherein the iron base sintered alloy surface layer portion contains Na in an average concentration of 0.0001 to 1 mass %.

6 . The iron base sintered alloy according to claim 3 ,

wherein the iron base sintered alloy surface layer portion contains K and Na in an average concentration of 0.0001 to 1 mass % in total.

7 . The iron base sintered alloy according to claim 1 ,

wherein the iron base sintered alloy inner portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, and balance: Fe and unavoidable impurities; and the iron base sintered alloy surface layer portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, K: 0.0001 to 1 mass % in the average concentration, and balance: Fe and unavoidable impurities.

8 . The iron base sintered alloy according to claim 2 ,

wherein the iron base sintered alloy inner portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, and balance: Fe and unavoidable impurities; and the iron base sintered alloy surface layer portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, Na: 0.0001 to 1 mass % in the average concentration, and balance: Fe and unavoidable impurities.

9 . The iron base sintered alloy according to claim 3 ,

wherein the iron base sintered alloy inner portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, and balance: Fe and unavoidable impurities; and the iron base sintered alloy surface layer portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, K and Na: 0.0001 to 1 mass % in the average concentration in total, and balance: Fe and unavoidable impurities.

10 . The iron base sintered alloy according to claim 1 ,

wherein the iron base sintered alloy inner portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, and balance: Fe and unavoidable impurities; and the iron base sintered alloy surface layer portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, K: 0.0001 to 1 mass % in the average concentration, and balance: Fe and unavoidable impurities.

11 . The iron base sintered alloy according to claim 2 ,

wherein the iron base sintered alloy inner portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, and balance: Fe and unavoidable impurities; and the iron base sintered alloy surface layer portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, Na: 0.0001 to 1 mass % in the average concentration, and balance: Fe and unavoidable impurities.

12 . The iron base sintered alloy according to claim 3 ,

wherein the iron base sintered alloy inner portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, and balance: Fe and unavoidable impurities; and the iron base sintered alloy surface layer portion has a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, K and Na : 0.0001 to 1 mass % in the average concentration in total, and balance: Fe and unavoidable impurities.

13 . The iron base sintered alloy according to claim 1 ,

wherein the iron base sintered alloy surface layer portion has an open porosity of 5% or less.

14 . A mechanical part made of the iron base sintered alloy according to claim 1 .

15 . The mechanical part according to claim 14 ,

wherein the mechanical part is a sprocket, a gear, a rotor, an inner race or an outer race.

16 - 19 . (canceled)

20 . An iron base sintered alloy having highly densified and hardened surface, comprising:

a surface layer portion of the iron base sintered alloy having a thickness in a range of 1 μm to 2 mm from a surface of the iron base sintered alloy, said surface layer having an average concentration of phosphor P, higher than a concentration of P contained in an inner portion of the iron base sintered alloy located inside the iron base sintered alloy surface layer portion, and the iron base sintered alloy surface layer portion contains potassium K.

21 . An iron base sintered alloy having highly densified and hardened surface, comprising:

an iron base sintered alloy surface layer portion having an average concentration of P higher than a concentration of P contained in an iron base sintered alloy inner portion, and

the iron base sintered alloy surface layer portion containing sodium Na.

22 . An iron base sintered alloy having highly densified and hardened surface, comprising:

an iron base sintered alloy surface layer portion having an average concentration of P higher than a concentration of P contained in an iron base sintered alloy inner portion, and

the iron base sintered alloy surface layer portion containing K and Na.

23 . The iron base sintered alloy according to claim 20 ,

wherein the average concentration of P of the iron base sintered alloy surface layer portion is higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass %, and the iron base sintered alloy surface layer portion contains K in an average concentration of 0.0001 to 1 mass %.

24 . The iron base sintered alloy according to claim 21 ,

wherein the average concentration of P of the iron base sintered alloy surface layer portion is higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass %, and the iron base sintered alloy surface layer portion contains Na in an average concentration of 0.0001 to 1 mass %.

25 . The iron base sintered alloy according to claim 22 ,

wherein the average concentration of P of the iron base sintered alloy surface layer portion is higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass %, and the iron base sintered alloy surface layer portion contains K and Na in an average concentration of 0.0001 to 1 mass % in total.

26 . The iron base sintered alloy according to claim 20 ,

wherein the iron base sintered alloy inner portion is made up of an iron base alloy sintered body having a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, P: 0.05 mass % or less (including 0 mass %), and balance: Fe and unavoidable impurities, and the iron base sintered alloy surface layer portion has the average concentration of P higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass % and contains K in an average concentration of 0.0001 to 1 mass %.

27 . The iron base sintered alloy according to claim 21 ,

wherein the iron base sintered alloy inner portion is made up of an iron base alloy sintered body having a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, P: 0.05 mass % or less (including 0 mass %), and balance: Fe and unavoidable impurities, and the iron base sintered alloy surface layer portion has the average concentration of P higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass % and contains Na in an average concentration of 0.0001 to 1 mass %.

28 . The iron base sintered alloy according to claim 22 ,

wherein the iron base sintered alloy inner portion is made up of an iron base alloy sintered body having a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, P: 0.05 mass % or less (including 0 mass %), and balance: Fe and unavoidable impurities, and the iron base sintered alloy surface layer portion has the average concentration of P higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass % and contains K and Na in an average concentration of 0.0001 to 1 mass % in total.

29 . The iron base sintered alloy according to claim 20 ,

wherein the iron base sintered alloy inner portion is made up of an iron base alloy sintered body having a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, P: 0.05 mass % or less (including 0 mass %), and balance: Fe and unavoidable impurities, and the iron base sintered alloy surface layer portion has the average concentration of P higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass % and contains K in an average concentration of 0.0001 to 1 mass %.

30 . The iron base sintered alloy according to claim 21 ,

wherein the iron base sintered alloy inner portion is made up of an iron base alloy sintered body having a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, P: 0.05 mass % or less (including 0 mass %), and balance: Fe and unavoidable impurities, and the iron base sintered alloy surface layer portion has the average concentration of P higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to 1 mass % and contains Na in an average concentration of 0.0001 to 1 mass %.

31 . The iron base sintered alloy according to claim 22 ,

wherein the iron base sintered alloy inner portion is made up of an iron base alloy sintered body having a composition of C: 0.1 to 0.9 mass %, one or at least two of Mo, Ni, Cr and Cu: 0.1 to 10 mass % in total, one or at least two of Mn, Si, V, Nb, W, Al, Ti, Ca and S: 0.1 to 3 mass % in total, P: 0.05 mass % or less (including 0 mass %), and balance: Fe and unavoidable impurities, and the iron base sintered alloy surface layer portion has the average concentration of P higher than the concentration of P contained in the iron base sintered alloy inner portion by 0.01 to I mass % and contains K and Na in an average concentration of 0.0001 to 1 mass % in total.

32 . The iron base sintered alloy according to claim 20 ,

wherein the iron base sintered alloy surface layer portion has open porosity of 5% or less.

33 . A mechanical part made of the iron base sintered alloy according to claim 20 .

34 . The mechanical part according to claim 33 ,

wherein the mechanical part is a sprocket, a gear, a rotor, an inner race, or an outer race.

35 - 38 . (canceled)

39 . A producing method of the iron base sintered alloy according to claim 1 , comprising:

forming a coat of a potassium sulfate salt consisting of one or at least two of potassium sulfate, potassium sulfite, potassium thiosulfate, potassium dodecyl sulfate, potassium dodecylbenzene sulfate, food blue No. 1 and potassium ascorbate sulfate ester, acting as a lubricant, on an inner surface of a cavity of a pressing die;

filling raw powder of the iron base sintered alloy into the cavity of the pressing die and then pressing the filled raw powder; and

sintering the formed powder compact.

40 . A producing method of the iron base sintered alloy according to claim 2 , comprising:

forming a coat of a sodium sulfate salt consisting of one or at least two of sodium sulfate, sodium sulfite, sodium thiosulfate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, food blue No. 5 and sodium ascorbate sulfate ester, acting as a lubricant, on an inner surface of a cavity of a pressing die;

filling raw powder of the iron base sintered alloy into the cavity of the pressing die and then pressing the filled raw powder; and

sintering the formed powder compact.

41 . A producing method of the iron base sintered alloy according to claim 3 , comprising:

forming a mixed coat of a potassium sulfate salt and a sodium sulfate salt, acting as a lubricant, on an inner surface of a cavity of a pressing die;

filling raw powder of the iron base sintered alloy into the cavity of the pressing die and then pressing the filled raw powder; and

sintering the formed powder compact.

42 . A producing method of the iron base sintered alloy according to claim 20 , comprising:

forming a coat of the potassium phosphate metallic salt consisting of one or at least two of dipotassium hydrogen phosphate, tripotassium phosphate, polypotassium phosphate, potassium riboflavin phosphate, acting as a lubricant, on an inner surface of a cavity of a pressing die;

filling raw powder of the iron base sintered alloy into the cavity of the pressing die and then pressing the filled raw powder; and

sintering the formed powder compact.

43 . A producing method of the iron base sintered alloy according to claim 21 , comprising:

forming a coat of the sodium phosphate metallic salt consisting of one or at least two of disodium hydrogen phosphate, trisodium phosphate, polysodium phosphate, sodium riboflavin phosphate, acting as a lubricant, on an inner surface of a cavity of a pressing die;

filling raw powder of the iron base sintered alloy into the cavity of the pressing die and then pressing the filled raw powder; and

sintering the formed powder compact.

44 . A producing method of the iron base sintered alloy according to claim 22 , comprising:

forming a coat of the mixed metallic salt of the potassium phosphate metallic salt and the sodium phosphate metallic salt, acting as a lubricant, on an inner surface of a cavity of a pressing die;

filling raw powder of the iron base sintered alloy into the cavity of the pressing die and then pressing the filled raw powder; and sintering the formed powder compact.