LOW COBALT HARD FACING ALLOY

Abstract

A stainless steel alloy comprising essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 10.5 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities. The impurities may consist of 0 to 0.2 percent by weight cobalt, 0 to 0.5 percent by weight manganese, 0 to 0.3 percent by weight molybdenum, 0 to 0.03 percent by weight phosphor, 0 to 0.03 percent by weight sulphur, 0 to 0.1 percent by weight nitrogen.

Claims

1. An alloy consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 10.5 percent by weight of a carbide former selected from the group consisting of molybdenum, tantalum, tungsten, zirconium and vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities

2. An alloy comprising essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 10.5 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

3. An alloy according to claim 2, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

4. An alloy according to claim 2, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.5 to 10.5 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

5. An alloy according to claim 1, wherein the impurities consist of 0 to 0.2 percent by weight cobalt, 0 to 0.3 percent by weight molybdenum, 0 to 0.03 percent by weight phosphor, 0 to 0.03 percent by weight sulphur, 0.1 to 0.5 percent by weight nitrogen and the balance iron plus impurities.

6. An alloy according to claim 1, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight tantalum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

7. An alloy according to claim 1, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight tantalum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

8. An alloy according to claim 1, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight tungsten, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

9. An alloy according to claim 8, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight tungsten, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

10. An alloy according to claim 1, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight Zirconium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

11. An alloy according to claim 10, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight Zirconium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

12. An alloy according to claim 1, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

13. An alloy according to claim 12, consisting essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

14. An alloy according to claim 6, wherein the impurities consist of 0 to 0.2 percent by weight cobalt, 0 to 0.5 percent by weight manganese, 0 to 0.3 percent by weight molybdenum, 0 to 0.03 percent by weight phosphor, 0 to 0.03 percent by weight sulphur, 0 to 0.1 percent by weight nitrogen.

15. An alloy according to claim 8, wherein the impurities consist of 0 to 0.2 percent by weight cobalt, 0 to 0.5 percent by weight manganese, 0 to 0.3 percent by weight molybdenum, 0 to 0.03 percent by weight phosphor, 0 to 0.03 percent by weight sulphur, 0 to 0.1 percent by weight nitrogen.

16. An alloy according to claim 10, wherein the impurities consist of 0 to 0.2 percent by weight cobalt, 0 to 0.5 percent by weight manganese, 0 to 0.3 percent by weight molybdenum, 0 to 0.03 percent by weight phosphor, 0 to 0.03 percent by weight sulphur, 0 to 0.1 percent by weight nitrogen.

17. An alloy according to claim 12, wherein the impurities consist of 0 to 0.2 percent by weight cobalt, 0 to 0.5 percent by weight manganese, 0 to 0.3 percent by weight molybdenum, 0 to 0.03 percent by weight phosphor, 0 to 0.03 percent by weight sulphur, 0 to 0.1 percent by weight nitrogen.

18. An article comprising an alloy as claimed in claim 1.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The improved alloys described here have been developed having, in weight percent, 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 10.5 percent by weight of a carbide former selected from the group consisting of molybdenum, tantalum, tungsten, zirconium and vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0042] The impurities may be up to 0.2 wt % cobalt, up to 0.5 wt % manganese, up to 0.03 wt % phosphor, up to 0.03 wt % sulphur and up to 0.1 wt % nitrogen. In the alloys which use titanium, tantalum, tungsten, zirconium or vanadium as the carbide former the alloy may contain an impurity of up to 0.3 wt % molybdenum

[0043] These compositions are similar to those proposed in U.S. Pat. No. 5,660,939 but there is a reduction in the niobium content and substitution with one or more carbide formers selected from the group consisting molybdenum, titanium, tantalum, tungsten, zirconium and vanadium.

[0044] Molybdenum is a carbide former which may be provided within the alloy in a quantity which further improves the properties of the alloy as it is provided in such a quantity that residual molybdenum following the formation of the carbides remains within the matrix and provides an improved pitting resistance.

[0045] In addition molybdenum carbide and tungsten carbide form at lower temperatures than niobium carbide and have a tendency to form molybdenum, or tungsten containing chromium carbides where the chromium content is in the range 19 to 22 by weight. Where niobium has been used as the carbide former it has been found that because it is a strong carbide former niobium carbides can form whilst atomising (or early on in casting if by that route) and grow which can then lead to nozzle blockages etc and hence low powder yield. Because molybdenum and tungsten have less affinity to form carbides than chromium the reaction with carbon provides molybdenum-containing chromium (Cr, Mo)C carbides rather than molybdenum carbides or tungsten-containing chromium (Cr, W)C carbides. In this way manufacturability of the alloy is maintained.

[0046] Exemplary alloy 1 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0047] Exemplary alloy 2 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.0 to 9.0 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0048] Exemplary alloy 3 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0049] Exemplary alloy 4 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 percent by weight carbon, 4.0 to 6.0 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0050] Exemplary alloy 5 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight tantalum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0051] Exemplary alloy 6 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.0 to 9.0 percent by weight tantalum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0052] Exemplary alloy 7 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight tantalum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0053] Exemplary alloy 8 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 percent by weight carbon, 4.0 to 6.0 percent by weight tantalum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0054] Exemplary alloy 9 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight tungsten, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0055] Exemplary alloy 10 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.0 to 9.0 percent by weight tungsten, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0056] Exemplary alloy 11 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight tungsten, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0057] Exemplary alloy 12 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 percent by weight carbon, 4.0 to 6.0 percent by weight tungsten, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0058] Exemplary alloy 13 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight Zirconium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0059] Exemplary alloy 14 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.0 to 9.0 percent by weight Zirconium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0060] Exemplary alloy 15 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight Zirconium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0061] Exemplary alloy 16 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 percent by weight carbon, 4.0 to 6.0 percent by weight Zirconium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0062] Exemplary alloy 17 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 to 2.0 percent by weight carbon, 4.0 to 9.0 percent by weight vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0063] Exemplary alloy 18 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 6.0 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.0 to 9.0 percent by weight vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0064] Exemplary alloy 19 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 9.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0065] Exemplary alloy 20 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 percent by weight carbon, 4.0 to 6.0 percent by weight vanadium, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0066] Exemplary alloy 21 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.25 percent by weight carbon, 4.0 to 6.0 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0067] Exemplary alloy 22 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 0.8 to 1.2 percent by weight carbon, 4.0 to 6.0 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0068] Exemplary alloy 23 consists essentially of 19 to 22 percent by weight chromium, 8.5 to 10.5 percent by weight nickel, 5.25 to 5.75 percent by weight silicon, 1.7 to 2.0 percent by weight carbon, 8.5 to 10.5 percent by weight molybdenum, 0.3 to 0.5 percent by weight titanium, 0.1 to 0.5 by weight percent nitrogen and the balance iron plus impurities.

[0069] In each of the above exemplary alloys impurities, which may be deliberately added, may be present. The impurities may be up to 0.2 wt % cobalt, up to 0.5 wt % manganese, up to 0.03 wt % phosphor, up to 0.03 wt % sulphur and up to 0.1 wt % nitrogen, up to 200ppm wt % oxygen. In the alloys which use titanium, tantalum, tungsten, zirconium or vanadium as the carbide former the alloy may contain an impurity of 0 to 0.3 wt % molybdenum

[0070] The new alloys have an acceptable galling resistance as carbides will still be formed, and the matrix continues to have a duplex autenitic/ferritic microstructure which undergoes secondary hardening due to the formation of an iron silicon intermetallic phase.

[0071] Further hardening is achievable by hot isostatic pressing (HIPPING) of the stainless steel alloy when in powder form where secondary hardening occurs within the ferritic phase of the duplex microstructure.

[0072] Although carbides continue to be formed the alloy has a resultant lover overall carbide caused, in part, by the weight percentage content of molybdenum and carbon giving an alloy with an acceptable hardness but greater ductility and toughness. This improvement in ductility opens up the range of range of applications where consideration to shock events has to be considered as well as the overall wear resistance requirement.