Braze materials and method for joining of ceramic matrix composites

Abstract

A method of coupling two ceramic matrix composite components comprises procuring a first ceramic matrix composite component, procuring a second ceramic matrix composite component, and applying a melt alloy between the first and second ceramic matrix components. The melt alloy comprises a homogeneous mixture of two or more materials in powder form, where the two or more materials include a braze alloy comprising silicon and a high melting point material or alloy. The first and second ceramic matrix composite components and the melt alloy are heat treated to a temperature, and the temperature is maintained for a length of time, followed by cooling, thereby coupling the first and second ceramic matrix composite components.

Claims

1. A melt alloy for use as a braze material for joining ceramic matrix composites, the melt alloy comprising: a homogeneous mixture of two or more materials in powder form, one of the two or more materials being a braze alloy comprising silicon and another of the two or more materials being a high melting point material or alloy, wherein the homogeneous mixture of the two or more materials in powder form is selected from the group consisting of (in wt. %): Ti-9Si (5%)+71SiCr (95%), 75SiTi (97%)+C (3%), 75SiTi (97%)+B (3%), 75SiTi (50%)+71SiCr (50%), 75SiTi (50%)+Ti-43Cr (50%), 75SiTi (50%)+12.5SiCo (50%), and Ti-25Cr-23Si (97%)+C (3%).

2. The melt alloy of claim 1, wherein the braze alloy comprising silicon further comprises titanium.

3. The melt alloy of claim 1, wherein the braze alloy comprising silicon further comprises chromium.

4. The melt alloy of claim 1, wherein the braze alloy includes up to about 75 wt. % Si.

5. The melt alloy of claim 4, wherein the braze alloy is selected from the group consisting of (in wt. %): Ti-9Si, Ti-25Cr-23Si, 71SiCr, and 75SiTi.

6. The melt alloy of claim 1, wherein the high melting point material is selected from the group consisting of C, B and TiH.

7. The melt alloy of claim 1, wherein the high melting point material is an alloy including at least one of silicon, titanium, chromium and cobalt.

8. The melt alloy of claim 1, wherein the mixture includes from 50 wt. % to 97 wt. % of the braze alloy, and from 3 wt. % to 50 wt. % of the high melting point material.

9. A method of coupling two ceramic matrix composite components, the method comprising the operations of: procuring a first ceramic matrix composite component; procuring a second ceramic matrix composite component; applying a melt alloy between the first and second ceramic matrix components, the melt alloy comprising a homogeneous mixture of two or more materials in powder form, where the two or more materials in powder form include a braze alloy comprising silicon and a high melting point material or alloy, the braze alloy including up to about 75 wt. % Si and being selected from the group consisting of (in wt. %): Ti-9Si, Ti-25Cr-23Si, 71SiCr, and 75SiTi; heat treating the first ceramic matrix composite component, the second ceramic matrix composite component, and the melt alloy to a temperature; maintaining the temperature for a length of time; and cooling the first ceramic matrix composite component, the second ceramic matrix composite component, and the melt alloy, thereby coupling the first and second ceramic matrix composite components.

10. The method of claim 9, wherein the braze alloy further comprises titanium.

11. The method of claim 9, wherein the braze alloy further comprises chromium.

12. The method of claim 9, wherein the high melting point material is selected from the group consisting of C, B and TiH.

13. The method of claim 9, wherein the high melting point material is an alloy including at least one of silicon, titanium, chromium and cobalt.

14. The method of claim 9, wherein the mixture includes from 50 wt. % to 97 wt. % of the braze alloy, and from 3 wt. % to 50 wt. % of the high melting point material.

15. The method of claim 9, wherein the homogeneous mixture of the two or more materials in powder form is selected from the group consisting of (in wt. %): Ti-9Si (5%)+71SiCr (95%), 75SiTi (97%)+C (3%), 75SiTi (97%)+B (3%), 75SiTi (50%)+71SiCr (50%), 75SiTi (50%)+Ti-43Cr (50%), 75SiTi (50%)+12.5SiCo (50%), and Ti-25Cr-23Si (97%)+C (3%).

16. A method of coupling two ceramic matrix composite components, the method comprising the operations of: procuring a first ceramic matrix composite component; procuring a second ceramic matrix composite component; applying a melt alloy between the first and second ceramic matrix components, the melt alloy comprising a homogeneous mixture of two or more materials in powder form, where the two or more materials in powder form include a braze alloy comprising silicon and a high melting point material or alloy; heat treating the first ceramic matrix composite component, the second ceramic matrix composite component, and the melt alloy to a temperature; maintaining the temperature for a length of time; and cooling the first ceramic matrix composite component, the second ceramic matrix composite component, and the melt alloy, thereby coupling the first and second ceramic matrix composite components, wherein the homogeneous mixture of the two or more materials in powder form is selected from the group consisting of (in wt. %): Ti-9Si (5%)+71SiCr (95%), 75SiTi (97%)+C (3%), 75SiTi (97%)+B (3%), 75SiTi (50%)+71SiCr (50%), 75SiTi (50%)+Ti-43Cr (50%), 75SiTi (50%)+12.5SiCo (50%), and Ti-25Cr-23Si (97%)+C (3%).

17. A method of coupling two ceramic matrix composite components, the method comprising the operations of: procuring a first ceramic matrix composite component; procuring a second ceramic matrix composite component; applying a melt alloy between the first and second ceramic matrix components, the melt alloy comprising a homogeneous mixture of two or more materials in powder form, where the two or more materials in powder form include a braze alloy comprising silicon and a high melting point material selected from the group consisting of C, B and TiH; heat treating the first ceramic matrix composite component, the second ceramic matrix composite component, and the melt alloy to a temperature; maintaining the temperature for a length of time; and cooling the first ceramic matrix composite component, the second ceramic matrix composite component, and the melt alloy, thereby coupling the first and second ceramic matrix composite components.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a gas turbine engine vane assembly made of ceramic matrix composite material, the vane assembly joined by a melt alloy;

(2) FIG. 2 is another perspective view of the gas turbine engine vane assembly of FIG. 1;

(3) FIG. 3 is an exploded assembly view of the vane assembly of FIG. 1 showing that the vane assembly includes an airfoil made of a ceramic matrix composite material, a first platform made of ceramic matrix composite material, and a second platform made of ceramic matrix composite material;

(4) FIG. 4 is a perspective view of a first test assembly used to test the melt alloy, the first test assembly including a first component made of ceramic matrix composite material joined to a second component made of ceramic matrix composite material by the melt alloy and a strip of ceramic matrix composite material reinforcing both sides of the joint;

(5) FIG. 5 is a side elevation view of the first test assembly of FIG. 4;

(6) FIG. 6 is a plan view of a second test assembly used to test the melt alloy, the second test assembly including a first component made of ceramic matrix composite material joined to a second component made of ceramic matrix composite material by the melt alloy and a strip of ceramic matrix composite material reinforcing both sides of the joint;

(7) FIG. 7 is an enlarged front view of a third test assembly used to test the melt alloy by cycling, for one hundred cycles, between room temperature and 2000 F. and holding the temperature at 2000 F. for one hour, the third test assembly including a first component made of ceramic matrix composite material joined to a second components made of ceramic matrix composite material by the melt alloy, and showing the microstructure of the pre-tested melt alloy joint; and

(8) FIG. 8 is an enlarged front view of the third test assembly used to test the melt alloy by cycling, for one hundred cycles, between room temperature and 2000 F. and holding the temperature at 2000 F. for one hour, and showing the microstructure of the post-tested melt alloy joint.

DETAILED DESCRIPTION OF THE DRAWINGS

(9) For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.

(10) A melt alloy 24 and a method of using the melt alloy 24 for brazing high temperature substrates including, for example, SiC fiber reinforced ceramic matrix composites is disclosed. In some embodiments, melt alloy 24 joins a ceramic matrix composite component to another ceramic matrix composite component. In some embodiments, melt alloy 24 joins a ceramic matrix composite component to a metal. In some embodiments, the melt alloy 24 includes at least one filler alloy, as shown, for example, in Table 1 below.

(11) The melt alloy 24 includes a base element and at least one secondary element that is different than the base element. The base element is selected from a group consisting of silicon, titanium, chromium, cobalt, niobium, hafnium, tantalum and germanium. The at least one secondary element is selected from a group consisting of chromium, aluminum, titanium, niobium, boron, silicon, and germanium. In some embodiments, melt alloy 24 includes a tertiary element. In some embodiments, the tertiary element is selected from a group consisting of carbon, boron, tantalum, niobium, and hafnium.

(12) In some embodiments, at least one lower melting point alloy or other material is included in melt alloy 24. In some embodiments, at least one higher melting point alloy or other material is included in melt alloy 24, for example, carbon, boron or TiH, as shown in Table 2. In some embodiments, melt alloy 24 is a homogeneous mixture of the two or more alloys combined in powder form.

(13) In one example, a melt alloy includes silicon-titanium (SiTi) and silicon-cobalt (SiCo) braze alloys and mixtures thereof. The exemplary melt alloy has good wetting and bonding of a SiC ceramic matrix composite material component to another SiC ceramic matrix composite material component with no excessive reactions between the melt alloy and the SiC ceramic matrix composite material components.

(14) As another example, the silicon filler material that is consisting of a mixture of braze-alloys and high-melting materials, produces in-situ stable microstructure and phases, such as SiC, in the brazed joints at high-temperatures. CTE between the silicon braze filler composition and ceramic matrix composite component minimizes the joint thermal mismatch, which results in lower thermal residual stresses in the ceramic matrix composite braze joints, as another example.

(15) As another example, the silicon filler material provides high-temperature joint mechanical properties. Tensile properties of double lap braze joints exceeded the ceramic matrix composite base material properties at room temperature, 2000 F., and 2100 F. The silicon filler material joints have high-temperature stability and cyclic oxidation resistance. As another example, the ceramic matrix composite melt alloy minimizes relative movements and leakages at the joint interfaces of ceramic matrix composite turbine vane assemblies as shown in FIG. 1.

(16) TABLE-US-00001 TABLE 1 Ceramic Matrix Composite Melt Alloy Compositions (by weight percent) Alloy # Alloy Name Melting ( F.) Al Cr Co Ti Ta CMC-Bra-1 75SiTi 2426 0.01 max 0.01 max 0.01 max 24.3-25.3 0.01 max CMC-Bra-2 91TiSi 2426 0.01 max 0.01 max 0.01 max 90.5-91.5 0.01 max CMC-Bra-3 71SiCr 2381 0.01 max 28.5-29.5 0.01 max 0.01 max 0.01 max CMC-Bra-4 Ti25Cr23Si 2381-2570 0.01 max 24.5-25.1 0.01 max 51.8-52.8 0.01 max CMC-Bra-5 57TiCr 2570 0.01 max 42.5-43.5 0.01 max 56.5-57.5 0.01 max CMC-Bra-6 12.5SiCo 2894 0.01 max 0.01 max 87.0-88.0 0.01 max 0.01 max CMC-Bra-7 98NbB 2894 0.01 max 0.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-8 89HfCr 2732 0.01 max 10.7-11.3 0.01 max 0.01 max 0.01 max CMC-Bra-9 64NbCr 3002 0.01 max 35.5-36.5 0.01 max 0.01 max 0.01 max CMC-Bra-10 74NbAl 2894 25.8-26.3 0.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-11 74TaAl 2901 25.8-26.3 0.01 max 0.01 max 0.01 max 73.5-74.5 CMC-Bra-12 53GeNb 2894 0.01 max 0.01 max 0.01 max 0.01 max 0.01 max Alloy # Nb Hf C B Si Ge CMC-Bra-1 0.01 max 0.01 max 3.01 max 0.01 max 74.7-75.7 0.01 max CMC-Bra-2 0.01 max 0.01 max 3.01 max 0.01 max 8.5-9.5 0.01 max CMC-Bra-3 0.01 max 0.01 max 3.01 max 0.01 max 70.5-71.5 0.01 max CMC-Bra-4 0.01 max 0.01 max 3.01 max 0.01 max 22.4-23.4 0.01 max CMC-Bra-5 0.01 max 0.01 max 3.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-6 0.01 max 0.01 max 3.01 max 0.01 max 12.0-13.0 0.01 max CMC-Bra-7 97.7-98.3 0.01 max 3.01 max 1.90-2.25 0.01 max 0.01 max CMC-Bra-8 0.01 max 88.5-89.5 3.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-9 63.5-64.5 0.01 max 3.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-10 73.5-74.5 0.01 max 3.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-11 0.01 max 0.01 max 3.01 max 0.01 max 0.01 max 0.01 max CMC-Bra-12 46.5-47.5 0.01 max 3.01 max 0.01 max 0.01 max 52.5-53.5

(17) TABLE-US-00002 TABLE 2 Ceramic Matrix Composite Melt Alloy Mixtures (by weight percent) Braze Mixture # Braze mixture (wt %) Comments BrazMix-1 Co-377 (95%) + Ti9Si CMC cracks, braze (5%) melt but not wet- out. BrazMix-2 Co-377 (96%) + TiH (4%) Braze melt, joint cracks, interface reacted BrazMix-3 Co-472 (96%) + TiH (4%) Melt, good flow, bonded, large voids, joint cracks, interface reactions BrazMix-4 Co-472 (95%) + 12.5SiCo Braze melt, not (5%) good flow, bonded, no cracks BrazMix-5 71SiCr (100%) Braze melt, good flow, no cracks BrazMix-6 71SiCr (95%) + Ti9Si Braze melt, good (5%) flow, no cracks, cyclic oxidation test at 2000 F./RT, SEM BrazMix-7 75SiTi (100%) Good flow, no cracks, cyclic test at 2000 F./RT no fracture in braze at 100 cycles BrazMix-8 75SiTi (97%) + C (3%) Good bond, cyclic test at 2000 F./RT no fracture in braze at 100 cycles, tensile tests BrazMix-9 75SiTi (97%) + B (3%) Not good flow, unbonded BrazMix-10 75SiTi (50%) + 71SiCr Good flow, bonded (50%) BrazMix-11 75SiTi (50%) + Ti43Cr Good flow, bonded (50%) BrazMix-12 75SiTi (50%) + 12.5SiCo Good flow, bonded (50%) BrazMix-13 Ti25Cr23Si (100%) Good flow, bonded BrazMix-14 Ti25Cr23Si (97%) + C Good flow, bonded, (3%) cyclic test at 2000 F./RT after 100 clycles of cyclic oxidation test

(18) In some embodiments, the melt alloy 24 comprises one or more high temperature melting alloys. In some embodiments, the melt alloy 24 is a braze alloy that has a melting point of about 1300 C. to 1650 C. In some embodiments, the melt alloy 24 is a crystalline solid. In some embodiments, the melt alloy 24 has a nominal composition comprising, in weight percent, up to about 75 percent silicon, up to about 25 percent aluminum, or up to about 91 percent titanium.

(19) In some embodiments, the melt alloy 24 includes a braze alloy mixture for brazing ceramic matrix composite substrates. In some embodiments, the melt alloy 24 is a eutectic mixture. In some embodiments, the melt alloy 24 includes a base metal. In some embodiments, the melt alloy 24 includes a base intermetallic element.

(20) In some embodiments, the melt alloy 24 includes at least one secondary metal different from the base metal and/or element. In some embodiments, the melt alloy 24 includes at least one secondary element different from the base metal and/or element.

(21) In some embodiments, the melt alloy 24 has a baseline braze alloy composition of silicon and titanium. In some embodiments, the melt alloy 24 has a baseline braze alloy composition of about 75 percent silicon by weight, 25 percent titanium by weight. In some embodiments, the melt alloy 24 has an eutectic melting temperature of 1330 C. In some embodiments, the melt alloy 24 has a baseline braze alloy composition of silicon, titanium, and at least one of aluminum, boron, and chromium. The aluminum, boron, and/or chromium improve joint re-melt temperatures and mechanical properties. In some embodiments, the melt alloy 24 has a composition including silicon, titanium, and an element selected from the group consisting of carbon, boron, tantalum, niobium, and hafnium.

(22) As an example of the melt alloy 24 in use, a vane assembly 10 of a gas turbine engine is shown in FIG. 1. The vane assembly 10 includes an airfoil 14, a first platform 12, and a second platform 16. In the illustrative embodiment, the airfoil 14, the first platform 12, and the second platform 16 are made of a ceramic matrix composite material.

(23) The airfoil 14 includes a first end 30 and a second end 32 spaced apart from and opposite the first end 30. The first platform 12 includes a first airfoil slot 18A sized to receive the first end 30 of the airfoil 14. The second platform 16 includes a second airfoil slot 18B sized to receive the second end 32 of the airfoil 14.

(24) To produce the vane assembly 10, the first end 30 of the airfoil 14 is received in the first airfoil slot 18A and the second end 32 of the airfoil 14 is received in the second airfoil slot 18B. The melt alloy 24 is applied to the first end 30, the first airfoil slot 18A, and the first platform 12 proximate the first end 30. The melt alloy 24 is applied to the second end 32, the second airfoil slot 18B, and the second platform 16 proximate the second end 32. In some embodiments, the melt alloy 24 may be applied before the first end 30 and/or the second end 32 is received in the first and second airfoil slots 18A, 18B respectively. The vane assembly 10 is heat treated and then cooled. After cooling, the airfoil 14 is coupled to the first and second platforms 12, 16.

(25) As an example of a method of using the melt alloy 24, the melt alloy 24 is applied to a first component, for example, the airfoil 14, and a second component, for example, the first platform 12. In some embodiments, both components are made of a ceramic matrix composite material. In some embodiments, one of the components is made from a metal material. The melt alloy 24 coated components are heat treated to a temperature sufficient to induce at least a portion of the braze composition to melt. In some embodiments, the temperature is 2475 F. The components and the melt alloy 24 are maintained at the temperature for a length of time. Thereafter, components and the melt alloy 24 are cooled. In some embodiments, the temperature is selected to be at least about 2400 F. yet lower than a melting point temperature of any of the ceramic matrix composite components.

(26) In some embodiments, the components are subjected to a diffusion heat treatment. The components are heat treated at a temperature suitable for diffusion. In some embodiments, the temperature is about 2000 F. to 2400 F.

(27) An example of an assembly used to test a ceramic matrix composite brazed joint is shown in FIGS. 4-6. The test assembly 20, shown in FIG. 4, includes a first component 22, a second component 26, melt alloy 24, a first reinforcement strip 23, and a second reinforcement strip 25. The first component 22 includes a top surface 40 and a bottom surface 42 spaced apart and opposite top surface 40. The second component 26 includes a top surface 44 and a bottom surface 46 spaced apart from and opposite the top surface 44.

(28) As shown in FIGS. 5 and 6, the first component 22 and the second component 26 lie in the same plane and are spaced apart from each other. The melt alloy 24 is applied between the first and second components 22, 26 along a width of the first and the second components 22, 26. The melt alloy 24 is additionally applied to top surfaces 40, 44 and bottom surfaces 42, 46 of the first and second components 22, 26 respectively. The first reinforcement strip 23 is positioned on the melt alloy 24 that is applied to the top surfaces 40, 44. The second reinforcement strip 25 is positioned on the melt alloy 24 that is applied to the bottom surfaces 42, 46. As such, the test assembly 20 has a double-lap joint. In some embodiments, the test assembly 20 has a single-lap joint. The test assembly 20 is heat treated and cooled to braze the melt alloy 24 to the first component 22, the second component 26, the first reinforcement strip 23, and the second reinforcing strip 25.

(29) The tensile strength of the test assembly 20 was then tested. To test the tensile strength, the first and second components 22, 26 were pulled in the opposite direction perpendicular to the reinforcement strips 23, 25. The tests were performed at least at room temperature, 2000 F., and 2100 F. For each test, the test assembly failed in either the first or second components 22, 26 at break point 27, but not in the melt alloy 24. All the ceramic matrix composite tensile specimens, like test assembly 20, failed in the ceramic matrix composite base materials outside of the braze joints. The tensile properties of the double-lap braze joints exceeded the ceramic matrix composite base material properties at room temperature, 2000 F., and 2100 F.

(30) The resistance of the joints of the test assembly 20 was tested for thermal shock and oxidation using cyclic oxidation tests between room temperature and 2000 F. The joints of the test assembly 20 survived after 100 cycles, wherein the temperature was held at 2000 F. for 1 hour per cycle.

(31) FIG. 7 shows as-brazed CMC joints. Brazed CMC joints after 100 cycles (hours) of 2000 F./RT Thermal Shock/Cyclic Oxidation tests are shown in FIG. 8. The microstructure of the brazed joints of the test assembly 20 was evaluated using a Scanning Electron Microscope (SEM) before testing and after the cycle oxidation tested conditions described above. The pre-test microstructure of the test assembly 20 is shown in FIG. 7. The post-test microstructure of the test assembly 20 is shown in FIG. 8. The tests revealed that the pre-test and post-test microstructure and strength were similar.

(32) While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.