High-performance metal alloy for additive manufacturing of machine components

Abstract

A high-performance metal alloy is disclosed being suitable for additive manufacturing of machine components, in particular machine components which are subjected to high gas temperature stress. Exemplary machine components are statoric components of gas turbines, such as nozzles.

Claims

1. A metal alloy having a nominal composition consisting of: TABLE-US-00010 O up to 0.1 wt % N up to 0.03 wt % S less than 0.004 wt % C up to 0.20 wt % Mn 0.6-1.4 wt % Si 0.76-2.0 wt % P less than 0.05 wt% Cr 25-35 wt % Ni 10.6-15.6 wt % W 2-10 wt % Fe 0.3-0.9 wt % Ta less than 0.04 wt % B less than 0.008 wt % Cu less than 0.02 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

2. The metal alloy of claim 1, wherein C is present in an amount up to 0.15 wt %.

3. The metal alloy of claim 2, wherein C is present in an amount up to 0.10 wt %.

4. The metal alloy of claim 3, wherein C is present in an amount of 0.001-0.07 wt %.

5. The metal alloy of claim 1, wherein B is present in an amount less than 0.004 wt %.

6. The metal alloy of claim 1, wherein N is present in an amount of 0.001-0.025 wt %.

7. The metal alloy of claim 1, wherein Mn is present in an amount of 0.6-1.0 wt %.

8. The metal alloy of claim 1, wherein Si is present in an amount of 0.8-1.5 wt %.

9. The metal alloy of claim 1, wherein Ni is present in an amount of 10.8-13.5 wt %.

10. The metal alloy of claim 1, wherein Fe is present in an amount of 0.4-0.8 wt %.

11. The metal alloy of claim 1, having a nominal composition consisting of: TABLE-US-00011 O up to 0.1 wt % N 0.001-0.025 wt % S less than 0.004 wt % C 0.001-0.07 wt % Mn 0.6-1.0 wt % Si 0.8-1.5 wt % P less than 0.05 wt % Cr 25-35 wt % Ni 10.8-13.5 wt % W 2-10 wt % Fe 0.4-0.9 wt % Ta less than 0.04 wt % B less than 0.004 wt % Cu less than 0.02 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

12. The metal alloy of claim 11, having a nominal composition consisting of: TABLE-US-00012 O 0.01-0.05 wt % N 0.005-0.025 wt % S less than 0.003 wt % C 0.005-0.07 wt % Mn 0.6-0.8 wt % Si 0.8-1.0 wt % P less than 0.04 wt % Cr 27-33 wt % Ni 11-12 wt % W 5-9 wt % Fe 0.4-0.7 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

13. The metal alloy of claim 12, having a nominal composition consisting of: TABLE-US-00013 O 0.036 wt % N 0.024 wt % S less than 0.003 wt % C 0.009 wt % Mn 0.71 wt % Si 0.91 wt % P less than 0.04 wt % Cr 29.76 wt % Ni 11.04 wt % W 6.98 wt % Fe 0.55 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

14. The metal alloy of claim 12, having a nominal composition consisting of: TABLE-US-00014 O 0.026 wt % N 0.007 wt % S less than 0.003 wt % C 0.039 wt % Mn 0.71 wt % Si 0.91 wt % P less than 0.04 wt % Cr 29.73 wt % Ni 11.05 wt % W 6.98 wt % Fe 0.54 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

15. The metal alloy of claim 1, obtainable by an additive manufacturing process selected from electron beam melting (EBM), selective laser melting (SLM), selective laser sintering (SLS), laser metal forming (LMF), direct metal laser sintering (DMLS), and direct metal laser melting (DMLM).

16. A gas turbine component, the component being a nozzle, made of the alloy of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The accompanying drawings, which are incorporated herein and constitute a part of the specification, illustrate exemplary embodiments of the present subject matter and, together with the detailed description, explain these embodiments. In the drawings:

(2) FIG. 1 shows a micrograph taken by Optical Microscope (magnification 50×) of the microstructure of a conventional alloy ‘FSX414’ of related art, as produced by Additive Manufacturing Process, where a high level of microstructural defects is visible; and

(3) FIG. 2 shows a micrograph taken by Optical Microscope (magnification 50×) of the microstructure of the new alloy, where no defects (either cracks or pores) are visible.

DETAILED DESCRIPTION

(4) The following description of exemplary embodiments refers to the accompanying drawings. The following description does not limit the invention. Instead, the scope of the invention is defined by the appended claims.

(5) Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

(6) First embodiments of the subject matter disclosed herein correspond to a high-performance metal alloy having a nominal composition consisting of:

(7) TABLE-US-00002 O up to 0.1 wt % N up to 0.03 wt % S less than 0.004 wt % C up to 0.20 wt % Mn 0.6-1.4 wt % Si 0.76-2.0 wt % P less than 0.05 wt % Cr 25-35 wt % Ni 10.6-15.6 wt % W 2-10 wt % Fe 0.3-0.9 wt % Ta less than 0.04 wt % B less than 0.008 wt % Cu less than 0.02 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(8) It should be appreciated that the alloy above encompasses reduced amounts of Carbon and Boron, so as to show remarkably and substantially reduced microstructural defects once processed by Additive Manufacturing technologies, with respect to the current best in class Co-based alloys (i.e. FSX414), while showing high-temperature oxidation and corrosion resistance and high resistance to thermal fatigue, as it will be demonstrated in the following working examples.

(9) With the term “up to”, it is meant that the element is present and in a wt % up to the upper limit value included.

(10) With the term “less than”, it is meant that the wt % ranges from the upper limit value included down to 0 (zero) included, so that the element can be absent.

(11) In some embodiments of the high-performance metal alloy, C is present in an amount up to 0.15 wt %; preferably in an amount up to 0.10 wt %; more preferably in an amount of 0.001-0.07 wt %. Reduced amounts of Carbon allow to achieve an advantageous balance between mechanical properties and microstructure goodness in Additive Manufacturing alloy; moreover reduced amounts of Carbon give enhanced mechanical properties in Investment Casting Alloy.

(12) In other embodiments of the high-performance metal alloy, B is present in an amount less than 0.004 wt %. Reduced amounts of Boron allow to improve Additive Manufacturing manufacturability.

(13) In other embodiments of the high-performance metal alloy, N is present in an amount of 0.001-0.025 wt %. The presence of Nitrogen allows to strengthen the alloy.

(14) In other embodiments of the high-performance metal alloy, Mn is present in an amount of 0.6-1.0 wt %. These amounts of Manganese improve mechanical properties as from the solid solution during the preparation process.

(15) In other embodiments of the high-performance metal alloy, Si is present in an amount of 0.8-1.5 wt %. These amounts of Silicon improve mechanical properties as from the solid solution during the preparation process.

(16) In other embodiments of the high-performance metal alloy, Ni is present in an amount of 10.8-13.5 wt %. These amounts of Nickel improve mechanical properties as from the solid solution during the preparation process.

(17) In other embodiments of the high-performance metal alloy, Fe is present in an amount of 0.4-0.8 wt %.

(18) In preferred embodiments, the high-performance metal alloy has a nominal composition consisting of:

(19) TABLE-US-00003 O up to 0.1 wt % N 0.001-0.025 wt % S less than 0.004 wt % C 0.001-0.07 wt % Mn 0.6-1.0 wt % Si 0.8-1.5 wt % P less than 0.05 wt % Cr 25-35 wt % Ni 10.8-13.5 wt % W 2-10 wt % Fe 0.4-0.9 wt % Ta less than 0.04 wt % B less than 0.004 wt % Cu less than 0.02 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(20) In particularly preferred embodiments of the high-performance metal alloy,

(21) TABLE-US-00004 O 0.01-0.05 wt % N 0.005-0.025 wt % S less than 0.003 wt % C 0.005-0.07 wt % Mn 0.6-0.8 wt % Si 0.8-1.0 wt % P less than 0.04 wt % Cr 27-33 wt % Ni 11-12 wt % W 5-9 wt % Fe 0.4-0.7 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(22) A particularly preferred embodiment corresponds to a high-performance metal alloy having a nominal composition consisting of:

(23) TABLE-US-00005 O 0.036 wt % N 0.024 wt % S less than 0.003 wt % C 0.009 wt % Mn 0.71 wt % Si 0.91 wt % P less than 0.04 wt % Cr 29.76 wt % Ni 11.04 wt % W 6.98 wt % Fe 0.55 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(24) Another particularly preferred embodiment corresponds to a high-performance metal alloy having a nominal composition consisting of:

(25) TABLE-US-00006 O 0.026 wt % N 0.007 wt % S less than 0.003 wt % C 0.039 wt % Mn 0.71 wt % Si 0.91 wt % P less than 0.04 wt % Cr 29.73 wt % Ni 11.05 wt % W 6.98 wt % Fe 0.54 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(26) With reference to FIG. 1, the observed microstructural defects of the current best in class Co-based alloys (i.e. FSX414) is characterized by linear appearance.

(27) Conversely, with reference with FIG. 2, the alloy herein disclosed shows a homogeneous surface without microstructural defects or discontinuities.

(28) The alloy herein disclosed can be obtained by processes of additive manufacturing, such as electron beam melting (EBM), selective laser melting (SLM), selective laser sintering (SLS), laser metal forming (LMF), direct metal laser sintering (DMLS), and direct metal laser melting (DMLM).

(29) In general, the process of production of the alloy can be carried out until a desired thickness and shape of the alloy is achieved.

(30) However, in preferred processes, the alloy is obtained by Direct Metal Laser Melting (DMLM), without the need of Hot Isostatic Press (HIP) process. The resulting alloy solution is then properly solutioned and aged.

(31) It should be understood that all aspects identified as preferred and advantageous for the alloy are to be deemed as similarly preferred and advantageous also for the respective processes of production.

(32) Second embodiments of the subject matter disclosed herein correspond to a gas turbine component, such as a statoric component, for example a nozzle, made of the above alloy. Nozzles, and particularly first stage nozzles, are subjected to the hottest gas temperatures in the turbine, but to lower mechanical stresses than buckets. The nozzles made of the above alloy have excellent high-temperature oxidation and corrosion resistance, high resistance to thermal fatigue, relatively good weldability for ease of manufacture and repair, and good castability.

(33) It should be also understood that all the combinations of preferred aspects of the alloy, and process of production, as well as their uses in gas turbine applications, as above reported, are to be deemed as hereby disclosed.

(34) While the disclosed embodiments of the subject matter described herein have been fully described above with particularity and detail in connection with several exemplary embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without materially departing from the novel teachings, the principles and concepts set forth herein, and advantages of the subject matter recited in the appended claims. Hence, the proper scope of the disclosed innovations should be determined only by the broadest interpretation of the appended claims so as to encompass all such modifications, changes, and omissions. In addition, the order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments.

EXAMPLES

Example 1

(35) An alloy has been prepared having the following nominal composition:

(36) TABLE-US-00007 O 0.036 wt % N 0.024 wt % S less than 0.003 wt % C 0.009 wt % Mn 0.71 wt % Si 0.91 wt % P less than 0.04 wt % Cr 29.76 wt % Ni 11.04 wt % W 6.98 wt % Fe 0.55 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(37) The alloy was obtained by DMLM, wherein the power source had an energy power of about 250 W. The resulting powder layer thickness was of about 0.05 mm.

(38) The power source scan spacing was preferably arranged in order to provide substantial overlapping of adjacent scan lines. An overlapping scan by the power source enabled stress reduction to be provided by the subsequent adjacent scan, and may effectively provide a continuously heat treated material.

(39) The resulting alloy solution was then solutioned and aged.

Example 2

(40) An alloy has been prepared having the following nominal composition:

(41) TABLE-US-00008 O 0.026 wt % N 0.007 wt % S less than 0.003 wt % C 0.039 wt % Mn 0.71 wt % Si 0.91 wt % P less than 0.04 wt % Cr 29.73 wt % Ni 11.05 wt % W 6.98 wt % Fe 0.54 wt % Ta less than 0.001 wt % B less than 0.003 wt % Cu less than 0.001 wt % Zr less than 0.003 wt % Co balance, based on the alloy weight.

(42) The alloy was obtained by DMLM at the same conditions as in Example 1.

Comparative Example 3

(43) A conventional FSX414 alloy has been prepared having the following nominal composition:

(44) TABLE-US-00009 S 0.02 wt % C 0.29 wt % Mn 0.44 wt % Si 0.9 wt % P 0.01 wt % Cr 28.9 wt % Ni 10.6 wt % W 7.0 wt % Fe 0.05 wt % B 0.012 wt % Co balance, based on the alloy weight.

(45) The alloy was obtained by DMLM at the same conditions as in Example 1.

Example 4

(46) The samples obtained in Example 1 and in Example 3 (i.e. conventional FSX414) by the same additive manufacturing process and parameters were examined along the building direction. They were conventionally metallographic prepared for Optical Microscope observation (magnification 50×). With reference to FIG. 1, the observed microstructural defects of the current best in class Co-based alloys (i.e. FSX414 of Example 3) is characterized by linear appearance.

(47) Conversely, with reference with FIG. 2, the alloy of Example 1 shows a homogeneous surface without microstructural defects or discontinuities.