NICKEL ALLOY

Abstract

The present invention relates to nickel alloys suitable for use in high temperature environments. For example, the nickel alloys of the present invention can be used in temperatures above 800 C. The nickel alloys may be used in the automotive industry, e.g. in turbocharge turbine wheels.

Claims

1. A nickel alloy comprising or consisting of: from 0.01 to 0.3 wt % carbon, from 7.0 to 15.0 wt % chromium from 0 to 12.0 wt % cobalt, from 3.0 to 7.0 wt % molybdenum, from 0.1 to 9.5 wt % tungsten, from 1.0 to 3.0 wt % niobium, from 0 to 2.0 wt % tantalum, from 0.5 to 2.0 wt % titanium, from 3.5 to 7.0 wt % aluminium, from 0 to 3.0 wt % boron, from 0.01 to 0.1 wt % zirconium; and either from 0.1 to 1.0 wt % hafnium or from 0.1 to 1.0 wt % vanadium, with the balance of the composition being nickel and incidental impurities.

2. A nickel alloy of claim 1 wherein carbon is present in a range of from 0.05 to 0.2 wt %.

3. A nickel alloy of claim 1, wherein chromium is present in a range of from 7.5 to 13 wt %.

4. A nickel alloy of claim 1, wherein molybdenum is present in a range of from 3.5 to 5.5 wt %.

5. A nickel alloy of claim 1, wherein niobium is present in a range of from 1.8 to 2.5 wt %.

6. A nickel alloy of claim 1, wherein titanium is present in a range of from 0.6 to 1.2 wt %.

7. A nickel alloy of claim 1, wherein aluminium is present in a range of from 5.0 to 7.0 wt %.

8. A nickel alloy of claim 1, wherein boron is present in a range of from 0.005 to 0.02 wt %.

9. A nickel alloy of claim 1, wherein zirconium is present in a range of from 0.03 to 0.08 wt %.

10. A nickel alloy of claim 1, wherein hafnium is present in a range of from 0.2 to 0.7 wt %.

11. A nickel alloy of claim 1, wherein vanadium is present in a range of from 0.1 to 0.4 wt %.

12. A nickel alloy of claim 1, wherein cobalt is optionally present in a range of from 9 to 11 wt %.

13. A nickel alloy of claim 1, wherein tantalum is optionally present in a range of from 0.5 to 1 wt %.

14. A nickel alloy of claim 1, wherein tungsten is present in a range of 0.1 to 1.0 wt % or 5 to 9 wt %.

15. A nickel alloy of claim 1, wherein the iron is present in an amount of 0.5 or 1 wt %.

16. A nickel alloy of claim 1, the alloy comprising: 0.1 wt % carbon 12.5 wt % chromium, 4.0 wt % molybdenum, 0.5 wt % tungsten, 2.0 wt % niobium, 0.8 wt % titanium, 6.6 wt % aluminium, 0.01 wt % boron, 0.06 wt % zirconium; and 0.25 wt % vanadium, with the balance of the composition being nickel and incidental impurities.

17. A nickel alloy of claim 1, the alloy comprising: 0.16 wt % carbon 8.2 wt % chromium, 10 wt % cobalt 5.0 wt % molybdenum, 7.0 wt % tungsten, 2.2 wt % niobium, 0.8 wt % tantalum 1.0 wt % titanium, 5.5 wt % aluminium, 0.015 wt % boron, 0.05 wt % zirconium; and 0.5 wt % hafnium, with the balance of the composition being nickel and incidental impurities.

18. A nickel alloy of claim 1, wherein tungsten is present in a range 5 to 9 wt %.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 shows the results of simulations to predict the high temperature strength of Examples 1 and 2 and the Reference alloys 1 and 2.

[0048] FIGS. 2 to 4 shows the results simulations to predict the high temperature rupture life of Examples 1 and 2 and the Reference alloys 1 and 2 at 3 different temperatures.

[0049] FIG. 5 is a representation of a typical manufacturing process.

DETAILED DESCRIPTION

[0050] Alloys according to the present invention are produced in a VIM furnace under vacuum or protective Argon atmosphere. The first stage of preparing the alloy involves calculating the relative proportions by weight of the various elemental components and scrap or masteralloys (which are the source of the various elements required in the final alloy) in order to achieve the desired amounts of the various elements which are required in the final alloy. The solid masteralloys, scrap or elements are added to the furnace. Heating is applied in order to melt all of the components together and ensure a thorough mixing of the components in the furnace so that the elements are properly distributed within the matrix.

[0051] Masteralloys, scrap or elements used in the process are commercially available.

[0052] Once melting and mixing has been achieved gaseous and low boiling point impurities are removed by exposure to the vacuum and non-metallics are removed by floatation, leaving a clean bath of liquid alloy in the furnace. A sample of the molten alloy is then removed from the furnace, allowed to cool and analysed by spectroscopic or other accepted analytical methods in order to determine its elemental composition. An adjustment to the composition may or may not be required at this stage to accommodate for any elemental mass loss during melting. The composition is adjusted by the addition of further elements as necessary, and optionally re-analysed to ensure that the desired composition has been achieved.

[0053] After the desired composition has been achieved, the temperature is further raised above the melting temperature to a tapping temperature in order to ensure easy pouring of the melt into moulds of the desired size and shape.

[0054] FIG. 5 is a representation of a typical manufacturing process.

EXAMPLES

[0055] Two example alloys have been manufactured. The composition of the alloys are disclosed below.

[0056] Example 1 is a nickel alloy having the composition shown below:

0.16 wt % carbon
8.2 wt % chromium,
10 wt % cobalt
5.0 wt % molybdenum,
7.0 wt % tungsten,
2.2 wt % niobium,
0.8 wt % tantalum
1.0 wt % titanium,
5.5 wt % aluminium,
0.015 wt % boron,
0.05 wt % zirconium,
0.5 wt % hafnium,
with the balance of the composition being nickel and incidental impurities.

[0057] Example 2 is a nickel alloy having the composition shown below:

0.1 wt % carbon
12.5 wt % chromium,
4.0 wt % molybdenum,
0.5 wt % tungsten,
2.0 wt % niobium,
0.8 wt % titanium,
6.6 wt % aluminium,
0.01 wt % boron,
0.06 wt % zirconium,
0.25 wt % vanadium,
with the balance of the composition being nickel and incidental impurities.

[0058] Test pieces of Examples 1 and 2 were melted in a small R&D VIM furnace and were cast into test carrots, using the investment casting process. The test carrots are being machined into tensile and stress rupture test pieces. Test pieces have been produced for Examples 1 and 2. Test carrots of two known alloys have been formed, Reference Example 1 (commercially available alloy Mar-M247) and Reference Example 2 (commercially available alloy IN7130). The performance of the test carrots of Examples 1 and 2 and the test carrots of Reference Example 1 (Mar-M247) and Reference Example 2 (IN7130) will be compared in a range of mechanical tests. The mechanical tests are set out below. It is anticipated that the performance of Examples 1 and 2 will be improved over the known alloys. This is due to the beneficial properties of Examples 1 and 2 demonstrated in predictive software.

[0059] Mechanical Testing

[0060] High temperature tensile testingsamples from each alloy will be tested at room temperature, 850 C., 950 C. and 1050 C. This is an industry standard test.

[0061] High temperature stress rupture testingsamples from each alloy will be tested at 850 C., 950 C. and 1050 C. This is also an industry standard test.

[0062] High temperature oxidation and corrosion testingsamples of each of the alloys will be exposed to exhaust gases from and diesel exhaust engines at elevated temperatures (850 C., 950 C. and 1050 C.) for extended periods. This test is designed to closely replicate the operating environment of turbocharger turbine wheels, although the samples will be not be subjected to any stress during the testing. This test will enable the high temperature oxidation and corrosion resistance to be determined for each alloy.

[0063] Metallographysamples of each alloy will be exposed to high temperatures (850 C., 950 C. and 1050 C.) for extended periods. Samples will be withdrawn at periodic intervals to be prepared for metallographic evaluation. This test will enable the high temperature microstructural evolution of each alloy to be determined.

Example 3

[0064] The high temperature properties of alloys of Examples 1 and 2 were modelled using the commercial computer programme JMatPro. Properties of the alloys along with Mar-M247 and IN713C were generated in JMatPro.

Example 3aHigh Temperature Tensile Properties

[0065] FIG. 1 shows the results of the simulations using JMatPro to predict the high temperature strength of Examples 1 and 2 and the Reference alloys 1 and 2. Example 1 showed a higher high temperature strength than that of Reference Example 1. It was unexpected that the performance of Example 1 would be better than that of Reference Example 1.

[0066] The simulations also showed that Example 2 exceeded the higher temperature mechanical properties of Reference Example 2. In addition Example 2 was shown to exceed the properties of Reference Example 1 at high temperature, an alloy which is four times the cost of example 1.

Example 3bHigh Temperature Rupture Life

[0067] Data generated using JMatPro indicates that the rupture life of Example 1 is greater than that of Reference Example 1 and that of Example 2 is greater than that of Reference Example 2 at elevated temperatures, as shown in FIGS. 2-4.

[0068] Throughout the description and claims of this specification, the words comprise and contain and variations of them mean including but not limited to, and they are not intended to (and do not) exclude other moieties, additives, components, integers or steps. Throughout the description and claims of this specification, the singular encompasses the plural unless the context otherwise requires. In particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise.

[0069] Features, integers, characteristics, compounds, chemical moieties or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0070] The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.