Steel alloy and a component comprising such a steel alloy
A carburisable steel alloy suitable for bearing components comprising, in percent by weight: C 0.05-0.5 wt. % Cr 2.5-5.0 wt. %, Mo 4-6 wt. %, W 2-4.5 wt. %, V 1-3 wt. %, Ni 2-4 wt. %, Co 2-8 wt. %, optionally one or more of the following elements: Nb 0-2 wt. % N 0-0.5 wt. % Si 0-0.7 wt. %, Mn 0-0.7 wt. %, Al 0-0.1 5 wt. %, wherein the combined amount of Nb+V is within the range 1-3.5 wt. %, the combined amount of C+N is within the range 0.05-0.5 wt. %, the balance being Fe and unavoidable impurities.
1. A method of making carburisable steel alloy comprising, in percent by weight:
C 0.05-0.5 wt. %,
Cr 2.5-5.0 wt. %,
Mo 4-6 wt. %,
W 2-4.5 wt. %,
V 1-3 wt. %,
Ni 2-4 wt. %,
Co 2-8 wt. %,
optionally one or more of the following elements:
Nb 0-2 wt. %,
N 0-0.5 wt. %,
Si 0-0.7 wt. %,
Mn 0-0.7 wt. %,
Al 0-0.15 wt. %,
wherein the combined amount of Nb+V is within the range 1-3.5 wt. %, the combined amount of C+N is within the range 0.05-0.5 wt. %, and the balance being Fe and unavoidable impurities, comprising
producing the steel alloy by vacuum induced melting and vacuum arc remelting (VIM-VAR), or
forming the steel alloy as a powder metallurgy steel alloy by gas atomisation, and additionally comprising
hardening and tempering the steel alloy to have a microstructure comprising tempered martensite and precipitated carbides, which microstructure is free or essentially free from ferrite.
2. A method for making a mechanical component comprising a steel alloy comprising, in percent by weight:
C 0.05-0.5 wt. %,
Cr 2.5-5.0 wt. %,
Mo 4-6 wt. %,
W 2-4.5 wt. %,
V 1-3 wt. %,
Ni 2-4 wt. %,
Co 2-8 wt. %,
optionally one or more of the following elements:
Nb 0-2 wt. %,
N 0-0.5 wt. %,
Si 0-0.7 wt. %,
Mn 0-0.7 wt. %,
Al 0-0.15 wt. %,
wherein the combined amount of Nb+V is within the range 1-3.5 wt. %, the combined amount of C+N is within the range 0.05-0.5 wt. %, and the balance being Fe and unavoidable impurities, comprising
producing the steel alloy by vacuum induced melting and vacuum arc remelting (VIM-VAR), or
forming the steel alloy as a powder metallurgy steel alloy by gas atomisation, and additionally comprising
carburising and/or nitriding the mechanical component to have a surface layer with an increased hardness.
3. The method according to claim 2 , comprising
forming the mechanical component from hot isostatically-pressed powder metallurgy steel alloy.
4. A method of making carburisable steel alloy comprising, in percent by weight:
C 0.05-0.5 wt. %,
Cr 2.5-5.0 wt. %,
Mo 4-6 wt. %,
W 2-4.5 wt. %,
V 1-3 wt. %,
Ni 2-4 wt. %,
Co 2-8 wt. %,
Si 0.05-0.7 wt. %,
Mn 0.05-0.7 wt. %,
optionally one or more of the following elements:
Nb 0-2 wt. %,
N 0-0.5 wt. %,
Al 0-0.15 wt. %,
wherein the combined amount of Nb+V is within the range 1-3.5 wt. %,
the combined amount of C+N is within the range 0.05-0.5 wt. %, and the balance being Fe and unavoidable impurities, comprising
producing the steel alloy by vacuum induced melting and vacuum arc remelting (VIM-VAR), or
forming the steel alloy as a powder metallurgy steel alloy by gas atomisation.
5. The method according to claim 4 , wherein the steel alloy comprises less than 1 wt. % unavoidable impurities.
6. The method according to claim 5 , wherein the steel alloy comprises less than 0.5 wt. % unavoidable impurities.
7. The method according to claim 4 , wherein the combined amount of C+N is within the range 0.05-0.3 wt. %.
8. The method according to claim 4 , wherein the steel alloy comprises 0.1-0.3 wt. % C.
9. The method according to claim 4 , wherein the steel alloy comprises 3-4.5 wt. % Cr.
10. The method according to claim 9 , wherein the steel alloy comprises 3-4 wt. % Cr.
11. The method according to claim 4 , wherein the steel alloy comprises 3-7 wt. % Co.
12. The method according to claim 11 , wherein the steel alloy comprises 4-6 wt. % Co.
13. The method according to claim 4 , wherein the steel alloy comprises 1.5-2.5 wt. % V.
14. The method according to claim 4 , wherein the expression 11 wt. %≤W eq ≤15 wt. % is satisfied, wherein W eq =W+2*Mo.
15. A method for making a mechanical component comprising a steel alloy according to claim 4 , comprising carburising and/or nitriding the mechanical component to have a surface layer with an increased hardness.
16. The method according to claim 15 , wherein the mechanical component is a bearing component.
17. The method according to claim 15 , comprising carburising the mechanical component to have an increased carbon content in its surface layer.
18. The method according to claim 17 , wherein the carbon content in the surface layer is at least 1.0 wt. %.
19. The method according to claim 18 , wherein the carbon content in the surface layer is at least 1.1 wt. %.