Precipitation-hardening stainless steel powder and sintered compact thereof
There is provided a precipitation hardening stainless steel powder including, in percentage by mass: Si: ≤1.0%; Mn: ≤1.8%; Ni: 3.0 to 8.5%; Cr: 12.0 to 20.0%; Mo: 0.1 to 2.5%; Cu: 1.0 to 5.0% and/or Ti+Al: 1.0 to 5.0%; Nb+Ta≥5C or Nb≥5C; N≤350 ppm; and the balance being Fe and incidental impurities. A sintered compact fabricated from the steel powder has a martensite content of 90% or more. The precipitation hardening stainless steel powder provides a sintered compact that exhibits high strength after aging.
1. A precipitation hardening stainless steel powder comprising, in percentage by mass:
C: ≤0.05%;
Si: ≤1.0%;
Mn: ≤1.8%;
Ni: 3.0 to 8.5%;
Cr: 12.0 to 20.0%;
Mo: 0.1 to 2.5%;
Cu: 1.0 to 5.0% and/or Ti+Al: 1.0 to 5.0%;
Nb+Ta≥5C or Nb≥5C;
N≤350 ppm; and
the balance being Fe and incidental impurities, wherein a sintered compact fabricated from the steel powder has a martensite content of 90% or more.
2. The precipitation hardening stainless steel powder according to claim 1 , containing Mn of 1.5% or less.
3. The precipitation hardening stainless steel powder according to claim 1 , having a Ni-bal value of −4 or more, wherein the Ni-bal is calculated by expression (1):
Ni-bal=Ni+27C+23N+0.2Mn+0.3Cu−1.2(Cr+Mo)−0.5Si−0.3Nb+10 (1).
4. The precipitation hardening stainless steel powder according to claim 3 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content.
5. The precipitation hardening stainless steel powder according to claim 3 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content without Cu.
6. The precipitation hardening stainless steel powder according to claim 1 , wherein the sintered compact fabricated from the steel powder has a grain size number of 7 or more.
7. The precipitation hardening stainless steel powder according to claim 6 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content.
8. The precipitation hardening stainless steel powder according to claim 6 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content without Cu.
9. The precipitation hardening stainless steel powder according to claim 2 , having a Ni-bal value of −4 or more, wherein the Ni-bal is calculated by expression (1):
Ni-bal=Ni+27C+23N+0.2Mn+0.3Cu−1.2(Cr+Mo)−0.5Si−0.3Nb+10 (1).
10. The precipitation hardening stainless steel powder according to claim 9 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content.
11. The precipitation hardening stainless steel powder according to claim 9 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content without Cu.
12. The precipitation hardening stainless steel powder according to claim 2 , wherein the sintered compact fabricated from the steel powder has a grain size number of 7 or more.
13. The precipitation hardening stainless steel powder according to claim 12 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content.
14. The precipitation hardening stainless steel powder according to claim 12 , containing one or two of Ti and Al of 1.0 to 5.0% in a total content without Cu.
15. A sintered compact fabricated from the precipitation hardening stainless steel powder according to claim 1 , having a martensite content of 90% or more and a grain size number of 7 or more.