BRAZE ALLOY COMPOSITIONS AND BRAZING METHODS FOR SUPERALLOYS

Abstract

A multi-component braze filler alloy comprising 60-70% by weight CM247 superalloy and BRB braze alloy is diffusion brazed to a CM247 alloy base substrate, such as a gas turbine blade or vane. The substrate/braze interface may be subsequently weld-repaired without de-melting and migrating the braze alloy from the interface. The weld zone and surrounding area are solidification crack resistant. After the alloy composition is brazed to the base substrate the component may be returned to service. Thereafter the component remains repairable by welding or re-brazing, if needed to correct future in-service defects.

Claims

1. A material for the braze repair of a nickel-base superalloy turbine component comprising a CM247/BRB mixture of CM247 base alloy in the range from approximately 60% to 70% by weight and the balance comprises BRB braze alloy.

2. A material as in claim 1, wherein the nickel-base superalloy turbine component comprises CM247.

3. A material as in claim 1, wherein the Ni-base superalloy component is a turbine vane or blade.

4. A material as in claim 1, wherein the CM247/BRB mixture comprises about 80% of CM247 base alloy by weight and the balance comprises the BRB braze alloy wherein the components brazed with the material are not subjected to temperatures exceeding about 2270 deg. F. during the brazing process.

5. A material as in claim 4, wherein the nickel-base superalloy turbine component comprises CM247.

6. A material as in claim 4, wherein the Ni-base superalloy component is a turbine vane or blade.

7. An article of manufacture comprising a Ni-base superalloy component wherein the Ni-base superalloy component has a portion thereof repaired by brazing with a brazing material, wherein the brazing material comprises a mixture of CM247 base alloy in the range from about 60% to about 70% by weight and the balance comprising a BRB braze alloy.

8. An article of manufacture as in claim 7, wherein the nickel-base superalloy turbine component comprises CM247.

9. An article of manufacture as in claim 7, wherein the Ni-base superalloy component is a turbine vane or blade.

10. An article of manufacture as in claim 7, wherein the Ni-base superalloy component has a portion thereof re-repaired by post braze welding and is suitable for continued service.

11. An article of manufacture as in claim 7, wherein the Ni-base superalloy component is post-braze heat treated and is suitable for continued service.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

[0016] FIG. 1: Tabular enumeration of some braze tests performed pursuant to some embodiments of the present invention;

[0017] FIG. 2: Typical vacuum cleaning furnace cycle pursuant to some embodiments of the present invention;

[0018] FIG. 3: Photomicrograph of typical cracks created for braze tests;

[0019] FIG. 4: Photomicrograph of typical cracks created for braze tests following the introduction of paste into the cracks by regulated compressed air behind a piston forcing the paste through an application needle, which was used to work the paste into the cracks as required. The paste comprises a liquid binder mixed with a braze alloy;

[0020] FIG. 5: Braze cycle used for some of the braze tests conducted herein, representing a typical braze cycle with multiple stop points in the ramp up to braze temperature, a short dwell at braze temperature and then a drop in temperature, and hold for alloy diffusion;

[0021] FIG. 6: Photomicrograph after completion of braze furnace cycle for the 50/50 alloy mix MarM509A/B;

[0022] FIG. 7: Photomicrograph after completion of braze furnace cycle for the 60/40 alloy mix MarM509A/B;

[0023] FIG. 8: Photomicrograph after completion of braze furnace cycle for the 70/30 alloy mix MarM509A/B;

[0024] FIG. 9: Photomicrograph at 50 after completion of braze furnace cycle for the 50/50 alloy mix MarM509A/B (etched);

[0025] FIG. 10: Photomicrograph at 50 after completion of braze furnace cycle for the 60/40 alloy mix MarM509A/B;

[0026] FIG. 11: Photomicrograph at 50 after completion of braze furnace cycle for the 70/30 alloy mix MarM509A/B (etched);

[0027] FIG. 12: Re-melt Evaluation. Photomicrograph following a solution heat treat cycle after completion of the braze furnace cycle to evaluate the affect on the braze of possible normal repair processes following brazing. Three mixtures of MarM/A/B are depicted (left to right), 70/30, 60/40, 50/50;

[0028] FIG. 13: Tabular enumeration of some braze tests performed pursuant to some embodiments of the present invention;

[0029] FIG. 14: Photomicrograph of cracks created in samples for braze test;

[0030] FIG. 15: Photomicrograph of cracks created in samples for braze test prior to HF cleaning;

[0031] FIG. 16: Photomicrograph of cracks created in samples for braze test following FIC cleaning and brazing;

[0032] FIG. 17: Alloy Application. Photomicrograph of typical cracks created for braze tests following the introduction of paste into the cracks by regulated compressed air behind a piston forcing the paste through an application needle, which was used to work the paste into the cracks as required. The paste comprises a liquid binder mixed with a braze alloy;

[0033] FIG. 18: Typical braze cycle as employed for some embodiments herein;

[0034] FIG. 19: Photomicrograph after completion of braze furnace cycle for the 60/40 alloy mix MarM509A/B;

[0035] FIG. 20: Photomicrograph after completion of braze furnace cycle for the 70/30 alloy mix MarM509A/B;

[0036] FIG. 21: Photomicrograph after completion of braze furnace cycle for the 80/20 alloy mix MarM509A/B;

[0037] FIG. 22: Photomicrograph after completion of braze furnace cycle for the 60/40 alloy mix CM247/BRB;

[0038] FIG. 23: Photomicrograph after completion of braze furnace cycle for the 70/30 alloy mix CM247/BRB;

[0039] FIG. 24: Photomicrograph after completion of braze furnace cycle for the 80/20 alloy mix CM247/BRB;

[0040] FIG. 25: Photomicrograph at 50 after completion of braze furnace cycle for the 60/40 alloy mix MarM509A/B;

[0041] FIG. 26: Photomicrograph at 50 after completion of braze furnace cycle for the 70/30 alloy mix MarM509A/B;

[0042] FIG. 27: Photomicrograph at 50 after completion of braze furnace cycle for the 80/20 alloy mix MarM509A/B;

[0043] FIG. 28: Photomicrograph at 50 after completion of braze furnace cycle for the 60/40 alloy mix CM247/BRB;

[0044] FIG. 29: Photomicrograph at 50 after completion of braze furnace cycle for the 70/30 alloy mix CM247/BRB;

[0045] FIG. 30: Photomicrograph at 50 after completion of braze furnace cycle for the 80/20 alloy mix CM247/BRB;

[0046] FIG. 31: Perspective and cross sectional photomicrograph following a solution heat treat cycle (2250 deg. F.) after completion of the braze furnace cycle to evaluate the affect on the braze of possible normal repair processes following brazing of CM247/BRB on a CM247 substrate with IN625 filler material;

[0047] FIG. 32: Photomicrograph following a solution heat treat cycle (2250 deg. F.) after completion of the braze furnace cycle to evaluate the affect on the braze of possible normal repair processes following brazing of MarM509/AB on a CM247 substrate with IN625 filler material. In the drawings and in the specification, MarM509 or 509 is an abbreviation of MarM509A or 509A respectively; and

[0048] FIG. 33: Results of mechanical testing for various braze materials and mixtures.

DETAILED DESCRIPTION

[0049] Improved high temperature repair braze compositions and methods are described, some embodiments of which achieve compositions, mechanical and structural properties nearer to that of the base metal. In some embodiments, the brazed region is subsequently weldable without incurring serious degradation of properties. After considering the following detailed description, those skilled in the art will clearly realize that the teachings of the present invention can be readily utilized in a multi-component braze filler alloy comprising various compositions of CM247 alloy, MarM509A, MarM509B and BRB braze alloy that are suitable for diffusion brazing to a nickel-based superalloy substrate such as CM247, such as typically used in a gas turbine blade or vane. The substrate/braze interface pursuant to some embodiments of the present invention is shown to be amenable to subsequent welding repair without incurring damaging demelting and/or migration of the braze alloy from the interface region. The weld zone and surrounding area are resistant to solidification cracking After the alloy composition is brazed to the base substrate the component may be returned to service. Thereafter, the component remains repairable by welding, if needed to correct future in-service defects, rather than scraping the component, with the weld-repaired component having reduced risk of solidification cracking as a consequence of the welding operation. This represents an important improvement over conventional brazing compositions and methods in which post braze welding typically degrades structural properties to such an extent that the component is no longer suitable for normal use.

CM247

[0050] Alloy 247 is an exemplary material for the fabrication of gas turbine components, and thus, to be concrete in our descriptions, specific formulations and procedures for the repair of alloy 247 components are described herein. However, the compositions and procedures described herein are not inherently limited to alloy 247, but can be advantageously used for the repair of other superalloys as apparent to those having ordinary skills in the art of superalloy material science and superalloy component repair.

[0051] The following composition has been found to be among those advantageous as a braze filler alloy for use with alloy 247, and comprises approximately 60%-70% by weight CM247 alloy with the remainder being BRB braze alloy. All percents are weight percents and are intended to be approximate, in which slight deviations about the quoted values are not expected to cause dramatic changes in performance or properties. A more precise range of applicability can readily be determined by routine experimentation.

[0052] CM 247 has a typical composition as follows (from Huang and Koo, Mat. Transactions 45 562-568 (2004), the entire contents of which is incorporated herein by reference for all purposes.):

Ni(X.sub.Ni)C(X.sub.C)Cr(X.sub.Cr)Co(X.sub.Co)Al(X.sub.Al)B(X.sub.B)W(X.sub.w)-Mo(X.sub.Mo)Ta(X.sub.Ta)Ti(X.sub.Ti)Hf(X.sub.Hf)Zr(X.sub.Zr).

in which the weight percentages X.sub.z are approximately as follows for CM247 alloy in Eq. 1.

C: X.sub.C=0.07%

Cr: X.sub.Cr=8.1%

Co: X.sub.Co=9.2%

Al: X.sub.Al=5.6%

B: X.sub.B=0.015%

W: X.sub.W=9.5%

Mo: X.sub.Mo=0.5%

Ta: X.sub.Ta=3.2%

Ti: X.sub.Ti=0.7%

Hf: X.sub.Hf=1.4%

Zr: X.sub.Zr=0.015%

Ni: X.sub.Ni=(balance)Eq. 1.

[0053] Slight variations in these proportions are within normal commercial usage. For example, the commercial CM247 known as MAR-M-247 has the composition given in Eq. 2 as provided by the vendor.

C: X.sub.C=0.15%

Cr: X.sub.Cr=8.4%

Co: X.sub.Co=10.0%

Al: X.sub.Al=5.5%

B: X.sub.B=0.015%

W: X.sub.W=10.0%

Mo: X.sub.Mo=0.7%

Ta: X.sub.Ta=3.0%

Ti: X.sub.Ti=1.0%

Hf: X.sub.Hf=1.5%

Zr: X.sub.Zr=0.05%

Ni: X.sub.Ni=(balance)Eq. 2.

[0054] Thus, in view of this data, we use CM 247 herein to denote a superalloy having a composition in approximately the following ranges as given in Eq. 3.

CM 247

C: X.sub.C=0.07-0.15%

Cr: X.sub.Cr=8.1-8.4%

Co: X.sub.Co=9.2-10.0%

Al: X.sub.Al=5.5-5.6%

B: X.sub.B=0.015%

W: X.sub.W=9.5-10.0%

Mo: X.sub.Mo=0.5-0.7%

Ta: X.sub.Ta=3.0-3.2%

Ti: X.sub.Ti=0.7-1.0%

Hf: X.sub.Hf=1.4-1.5%

Zr: X.sub.Zr=0.015-0.05%

Ni: X.sub.Ni=(balance)Eq. 3.

[0055] The results reported herein employ AIMRO CM 247, substantially the same as CM247 described herein. For economy of language, we use CM247 herein to denote a material having a composition substantially within the ranges given by Eq. 3.

[0056] The experimental data obtained herein relates to directionally solidified CM 247 (CM247DS). However, it is not expected that the use of single crystal, polycrystalline or other forms of CM 247 will have a significant effect on the results.

BRB

[0057] BRB is a nickel-based diffusion braze alloy, such as commercially available through Sulzer Metco as Amdry BRB. The BRB material used herein has substantially the following composition:

Ni(X.sub.Ni)Cr(X.sub.Cr)Co(X.sub.Co)Al(X.sub.Al)B(X.sub.B) in which the weight percentages X.sub.Z are approximately in the following ranges:

BRB

Cr: X.sub.Cr=13.0-14.0%

Co: X.sub.Co=9.0-10.0%

Al: X.sub.Al=3.5-4.5%

B: X.sub.B=2.25-2.75%

Ni: X.sub.Ni=(balance)Eq. 4.

with a particle size distribution having a nominal range150+45 m (micrometers), mesh (ASTM)100+325 mesh. For economy of language, we use BRB herein to denote a material having a composition substantially within the ranges given by Eq. 4.

MarM509A/MarM509B

[0058] Brazing tests and improved brazing results are also described herein for cobalt based superalloys containing relatively large amounts of chromium and nickel commercially known under the trade names MarM509 (MarM509A, or briefly 509A), MarM509B (509B). The particular MarM509A/B materials used herein were obtained from Sulzer Metco under the trade names Amdry MM509 (509A) and Amdry MM509B (509B). The compositions provided by the vendor are as follows:

TABLE-US-00001 509A (Eq. 5A) 509B (Eq. 5B) C: X.sub.C = 0.6% C: X.sub.C = 0.6% Cr: X.sub.Cr = 24% Cr: X.sub.Cr = 23% Ni: X.sub.Ni = 10% Ni: X.sub.Ni = 10% W: X.sub.W = 7% W: X.sub.W = 7% Ta: X.sub.Ta = 3.5% Ta: X.sub.Ta = 3.5% Co: X.sub.Co = (balance) B: X.sub.B = 2.5% Co: X.sub.Co = (balance)

[0059] Studies were carried out using several of the present braze composition alloys pursuant to some embodiments of the present invention to repair cracks on an alloy 247 blade substrates and subsequently weld the brazed blades with the results described herein. It is apparent that these results demonstrate an improvement over prior art brazing compositions and methods, leading towards more effective, less expensive, service-ready repairs of superalloy components following brazing.

Results: CM247 DS Base Material Braze with CM247/BRB and MarM509A/MarM509B.

[0060] Improvements obtainable pursuant to some embodiments of the present invention, employing different mixtures of CM247/BRB and MarM509A/MarM509B under different processing conditions are presented. To be concrete in our discussion, we consider brazing a CM247 substrate material, more particularly, a component comprising service run row 1 turbine blades from the W501G engine made of CM247 DS castings. These examples are intended to be illustrative, not limiting, as one skilled in the art can readily adapt these compositions and methods to other substrate materials and/or components without undue experimentation. That is, these tests are typical examples of results obtainable and do not limit the scope of the present invention to specific compositions or process conditions disclosed. However, this particular example of turbine blades has considerable practical and commercial importance in itself

[0061] The tests described herein were conducted in separate rounds consisting of different braze base alloys of multiple mixtures with one braze alloy, different braze furnace cycles and different substrate preparation methods.

[0062] Several criteria were used to evaluate the results of these tests: [0063] 1. General visual appearance of the braze. [0064] 2. Metallographic evaluation of the interface, crack fill and porosity. [0065] 3. Remelt of the braze during a post braze solution heat treat cycle. [0066] 4. Post braze weldability. [0067] 5. Mechanical testing including surface hardness, UTS (ultimate tensile strength), yield and elongation.

Examples A: MarM509A/MarM509B (MarM509A/B) Mixtures

[0068] MarM509A/B denotes a mixture of 509A and 509B materials having the compositions substantially as given in Eqs. 5A and 5B respectively.

Example A.I: Surface Preparation

[0069] Two methods of surface preparation were combined for this test. A mechanical cleaning of the area was performed, using carbide blend tools to create a simulated crack approximately 0.050 (inches) in width by approximately 0.050 in depth. A typical example is shown in FIG. 3. Following the mechanical cleaning and the creation of the simulated cracks, the blade material was subjected to a vacuum cleaning furnace cycle according to the procedures given in FIG. 2.

Example A.II: Alloy Application

[0070] Three different mixtures of a single base and a single braze alloy were tested. In all of these cases, the braze alloy was MarM509B (509B) and the base was MarM509A (509A). The base was mixed with braze alloy with weight ratios 509A/509B of 50/50, 60/40, 70/30 and then combined with liquid binder in the amount of about 10%-15% by volume to form a paste. The paste was then worked into a plastic cartridge with regulated compressed air behind a piston to force the paste through an application needle that was used to work the paste into the cracks as required. Stop off can be applied as required to the base material around the braze to assure that the alloy does not run outside the intended repair zone. A typical result of this alloy-application, crack-filling step is shown in FIG. 4.

Example A-III: Braze Cycle

[0071] The braze cycle employed in this Example A represents a typical braze cycle with multiple stop points in the ramp up to braze temperature, a dwell at braze temperature followed by a drop in temperature and a holding period for alloy diffusion. A typical cycle is given in FIG. 5. It is important to note that 2200 deg. F. is the highest temperature applied during all braze cycles employed in these Examples-A for MarM509A/B.

Example A-IV: Results

[0072] Results from seven tests are reported herein, identified as Example A-04 to Example A-10 in FIG. 1.

A-IV(i) Post Braze Visual Evaluation

[0073] A visual inspection was performed after the braze furnace cycle was completed. The results for MarM509A/B (Examples A-04, A-05, A-06 of FIG. 1) are shown as follows:

[0074] FIG. 6 is a photomicrograph of results obtained with the 50/50 alloy mixture. This 50/50 alloy mixture appears hot (that is, close to or exceeding its melting point) and perhaps has a slight undercut around the braze edges, although this cannot be definitively determined from this micrograph.

[0075] FIG. 7 is a photomicrograph of results obtained with the 60/40 alloy mixture. This 60/40 alloy mixture appears to have a reasonably smooth appearance and apparently shows continuous flow at the edges.

[0076] FIG. 8 is a photomicrograph of results obtained with the 70/30 alloy mixture. This 70/30 alloy mixture apparently shows a sluggish flow resulting in a significant transition at the braze edges.

A-IV(ii) Metallographic Evaluation

[0077] Metallographic evaluation was performed at 50 for flow, interface quality, porosity and other defects. The results for MarM509A/B (Examples A-04, A-05, A-06 of FIG. 1) are shown as follows:

[0078] FIG. 9 is the metallographic result for the 50/50 braze mixture. This photomicrograph apparently indicates good flow into the base material, providing a smooth transition from the braze repair area. The interface appears to be substantially acceptable but with a hint of being hot. Porosity was below 1% of the measured area of the repair.

[0079] FIG. 10 is the metallographic result for the 60/40 braze mixture. This photomicrograph apparently indicates good flow into the base material, providing a smooth transition from the braze repair area. The interface appears to be excellent and porosity was below 1% of the measured area of the repair

[0080] FIG. 11 is the metallographic result for the 70/30 braze mixture. This photomicrograph apparently indicates sluggish flow into the base material with a sharp contrast from the blaze alloy. The interface appears to be substantially acceptable but the porosity was rather high with severe voiding arising from a lack of adequate alloy flow.

A-IV(iii) Remelt Evaluation

[0081] The three different mixtures considered in this Example-A, MarM509A/B (Examples-04, -05, -06 of FIG. 1) were subjected to a typical solution heat treat cycle after the braze was completed in order to determine if the braze alloy would likely be affected if the component so brazed were later subjected to a normal repair process. The remelt percentage was calculated by comparing the alloy height following solution heat treatment to the alloy height following the braze process but before the solution heat treatment. For 50/50 (MarM509A/B) more than 100% remelt was observed. The alloy returned to its liquid state and ran off the workpiece resulting in a depression below the level of the original surface. For 60/40 (MarM509A/B), approximately 50% alloy height loss was observed. For 70/30 (MarM509A/B), approximately 30% alloy height loss was observed. A photomicrograph of these results is provided in FIG. 12.

A-IV(iv): Post Braze Weld Evaluation

[0082] No weld evaluation was performed on these braze samples due to the failure of the remelt tests.

A-IV(v): Mechanical Testing

[0083] No mechanical testing was performed on these samples due to the failure of the remelt tests.

Example B: CM247/BRB Mixtures

[0084] CM247/BRB denotes a mixture of CM247 and BRB materials having the compositions substantially as given in Eqs. 3 and 4 respectively.

[0085] Additional braze tests were performed combining braze and diffusion cycles performed to the same times and temperature as used for the base material heat treat cycle. The tests consisted of one braze cycle, one surface preparation method, with two base alloys mixed using three different levels of two different braze alloys.

Example B-I: Surface Preparation

[0086] The braze surfaces were prepared using a mechanical cleaning method with carbide blend tools to create a simulated crack approximately 0.050 in width by approximately 0.050 in depth. No vacuum cleaning furnace cycle was performed after the mechanical cleaning operation. One blade was cleaned using a fluoride ion cleaning (FIC) furnace with HF gas to prepare the surface for braze. FIGS. 14, 15, 16 show typical blades at various stages in the surface preparation process.

Example B-II: Alloy Application

[0087] Three different mixtures of two base and braze alloys were prepared and tested: (MarM-509A base/MarM-509B braze) and (CM247/BRB).

[0088] The MarM-509A (509A) base was mixed with MarM-509B (509B) braze alloy in the ratios (by weight) 60/40, 70/30, 80/20 (509A/509B). These mixtures were then combined with liquid binder in an amount of 10%-15% by volume to form a paste.

[0089] The CM247 base was mixed with BRB braze alloy in the ratios CM247/BRB (by weight) 60/40, 70/30, 80/20. These mixtures were then combined with liquid binder in an amount of 10%-15% by volume to form a paste. Thus, six pastes were prepared and tested.

[0090] Each paste was worked into a plastic cartridge with regulated compressed air behind a piston to force the paste through an application needle that was used to work the paste into the cracks as required. Stop off can be applied as required to the base material around the braze to assure that the alloy does not run outside the intended repair zone. FIG. 17 shows typical blades following the step of alloy application.

Example B-III: Braze Cycle

[0091] The braze cycle used was chosen to have the same times and temperatures as a standard solution heat treat cycle, as given in FIG. 18.

Example B-IV: Results

[0092] Results from 20 tests are reported herein, identified as Example B-14 to Example B-39 in FIG. 13.

B-IV(i): Post Braze Visual Evaluation

[0093] A visual inspection was performed following the combined braze and diffusion furnace cycle of FIG. 18. The results for MarM509A/B (Examples B-29, B-30, B-31) are shown as follows:

[0094] FIG. 19 is a photomicrograph of results obtained with the 60/40 alloy mixture. This mixture appears hot with excessive run of the alloy from the braze area.

[0095] FIG. 20 is a photomicrograph of results obtained with the 70/30 alloy mixture. This mixture has an excellent smooth appearance with good continuous flow at the edges.

[0096] FIG. 21 is a photomicrograph of results obtained with the 80/20 alloy mixture. This mixture has a slight sluggish appearance but appears to be acceptable with some contrast at the braze edges.

[0097] The results of the visual inspection for CM247/BRB (Examples B-14, B-15, B-16) are shown as follows:

[0098] FIG. 22 is a photomicrograph of results obtained with the 60/40 alloy mixture. This mixture appears very hot with excessive run of the alloy from the braze area.

[0099] FIG. 23 is a photomicrograph of results obtained with the 70/30 alloy mixture. This mixture has a good smooth appearance at the edges with some alloy flow from the repair area.

[0100] FIG. 24 is a photomicrograph of results obtained with the 80/20 alloy mixture. This mixture has a smooth appearance at the braze edges with a slight sluggish appearance, but probably an acceptable appearance.

B-IV(ii): Metallographic Evaluation

[0101] Metallographic evaluation was performed at 50 for flow, interface quality, porosity and other defects. The results for MarM509A/B (Examples B-29, B-30, B-31) are shown as follows:

[0102] FIG. 25 is a photomicrograph of results obtained with the 60/40 braze mixture. The photomicrograph apparently shows good flow into the base material providing a smooth transition from the braze alloy. The interface appears to be acceptable but with a hint of being hot. Porosity was similar to the casting material and below about 1% of the measured volume of the repair area.

[0103] FIG. 26 is a photomicrograph of results obtained with the 70/30 braze mixture. The photomicrograph shows excellent flow into the base material, providing a smooth transition from the edges. The interface is excellent. The porosity is similar to the casting material and below about 1% of the measured volume of the repaired area. The right edge of the braze was apparently missed and not filled during the application of the alloy.

[0104] FIG. 27 is a photomicrograph of results obtained with the 80/20 braze alloy mixture. The photomicrograph shows sluggish flow into the base material with a sharp contrast from the regions at the edges. The actual interface is apparently acceptable but the porosity was beyond typically acceptable limits with severe voiding from lack of flow.

[0105] The results for CM247/BRB (Examples B-14, B-15, B-16) are shown as follows:

[0106] FIG. 28 is a photomicrograph of results obtained with the 60/40 braze mixture. The photomicrograph apparently shows good flow into the base material providing a smooth transition from the braze repair area. The interface appears to be acceptable but with a hint of being hot. Porosity was similar to the casting material and below about 1% of the measured volume of the repair area.

[0107] FIG. 29 is a photomicrograph of results obtained with the 70/30 braze mixture. The photomicrograph shows excellent flow into the base material, providing a smooth transition from the braze repair area. The interface is excellent. The porosity is similar to the casting material and below about 1% of the measured volume of the repair area.

[0108] FIG. 30 is a photomicrograph of results obtained with the 80/20 braze alloy mixture. The photomicrograph shows sluggish flow into the base material with a sharp contrast at the edges. The actual interface is apparently acceptable but the porosity was beyond typically acceptable limits with severe voiding from lack of flow.

Example B-IV(iii): Remelt Evaluation

[0109] Three different mixtures of MarM509/A/B were subjected to a solution heat treat cycle (2270 deg. F.) after the initial braze was completed to determine if the braze would be affected during a future normal repair process. The remit percentage was calculated by comparing the bead height following the solution heat treat cycle with the post braze alloy bead height.

[0110] 60/40 Remelt Evaluation: 100% of the alloy height loss was observed (Total Remelt).

[0111] 70/30 Remelt Evaluation: An alloy height loss of approximately 10% of was observed.

[0112] 80/20 Remelt Evaluation: No alloy height loss was observed.

[0113] It is important to note that this remelt evaluation shows marked improvement over the remelt discussed in Example A-IV(iii) for the 70/30 and 80/20 compositions. We attribute this to the use of generally higher braze temperature and times for these

[0114] Examples-B in comparison to the braze temperature and times used in Example-A. From FIG. 18 we see that Example-B components were held at 2270 deg. F. (12 deg. F.) for 240-255 min. while in Example-A, the components were held at 2200 deg. F. (10 deg. F.) for 40 min. and at 2050 deg. F. (10 deg. F.) for 270 min. (FIG. 5). Thus, we conclude that the different time-temperature protocol has an important effect on the properties of braze joints for 509A/509B braze compositions and that ratios of 509A/509B less than about 70/30 are contraindicated.

[0115] Three different mixtures of CM247/BRB were subjected to a solution heat treat cycle (2270 deg. F.) after the initial braze was completed to determine if the braze would be affected during a future normal repair process. The remit percentage was calculated by comparing the bead height following the solution heat treat cycle with the post braze alloy bead height.

[0116] 60/40 Remelt Evaluation: 100% of the alloy height loss was observed (Total Remelt).

[0117] 70/30 Remelt Evaluation: An alloy height loss of approximately 10% of was observed.

[0118] 80/20 Remelt Evaluation: No alloy height loss was observed.

[0119] In summary, 60/40 shows good flowability, deposition and mechanical properties, but lacks good remelt characteristics when compared to 70/30 or 80/20. It appears advantageous to use the 70/30 mixture if the braze composition is to be applied and if it is to be subjected to any re-heating above about 2270 deg.

Example B-IV(iv): Post Braze Weld Evaluation

[0120] An evaluation was done on CM247/BRB (Example B-24) to observe the effect of a post braze weld repair using IN625 filler material. The test was completed after a post weld solution cycle. However, no age heat treat was performed. No cracks were observed at the interface or surrounding areas, and the welder performing the work reported that this weld seemed to be similar to that of a weld of the base alloy. See FIG. 31.

[0121] An evaluation was done on MarM509/A/B (Example B-39) to observe the effect of a post braze weld repair using IN625 filler material. The test was completed after a post weld solution cycle. However, no age heat treat was performed. No cracks were observed at the interface or surrounding areas, and the welder performing the work reported that this weld seemed to be similar to that of a weld of the base alloy. See FIG. 32. Therefore, the 70/30 mixture is considered to be advantageous on the basis of the following tests and/or observations: [0122] Flowability (ability to fill the gaps and cracks) [0123] Remelt [0124] Reweld [0125] Hardness [0126] Tensile Tests [0127] Mechanical Tests

Example B-IV(vi) Mechanical Testing

[0128] Mechanical testing was done to compare the hardness, tensile strength, yield and elongation of the two alloys of various mixtures against the base material and the base material with IN625 weld repairs. The tests were carried out by Metcut Research, Inc. of Cincinnati, Ohio according to the procedures given in FIG. 33. Six samples of each type were tested and the average of those six are reported in FIG. 33 including the Base Material (Specimen 45) and the base material with IN625 weld repairs (Specimen 46).

CONCLUSIONS

Surface Preparation

[0129] Mechanical cleaning provided an excellent braze surface and interface between braze and the base alloy. The mechanical-vacuum cleaning process used in Example A provided an equal interface, however no better than the mechanical cleaning process alone. No apparent benefits resulted from using the extra furnace cycle. Examples B were performed after mechanical preparation of the surface using a carbide burr to remove the top layer of material. The mechanical test samples were also prepared using this same method which further indicates the acceptability of the process. The FIC cleaning process did provide a better visual wetting of the alloy and apparently a very slightly improved interface observed during the lab examination. However, all mechanical tests performed showed a consistent loss of tensile strength of about 4%-5%.

Braze Alloy Selection and Application.

[0130] The CM247 base alloy mixed with BRB braze material consistently provided the best test results observed herein. The CM247 and MarM509A base alloy powders provided substantially equal results with regard to visual flow and interface quality. However, when mixed with equal amounts of braze alloy the CM247 typically was slightly more free flowing. The CM247 alloy typically provided 13%-15% better tensile strength values than the MarM509 alloy of the same mixture with higher and more consistent strain rate through 2.0% yield values. Both CM247 and MarM509 braze provided substantially equal visual results when welded with IN625 filler material. However, it is generally better practice to strive to have the chemical composition of the repair area as close to the original base material as possible (that is, a higher base alloy content in the mixtures).

[0131] The 70/30 mixture of the CM247 base powder with the BRB braze alloy provided better results with regard to porosity, crack fill, post braze solution cycle remelt and tensile strength. It is also observed that the braze elongation with the CM247 base alloy was typically superior to the MarM509 alloy. However the elongation numbers typically decreased from the 60/40 mixture up to the 70/30 mixture.

[0132] The remit evaluation with the 70/30 mixture seemed to be acceptable with regard to future repair cycles with only a slight hint (10% height loss) of the alloy turning liquid during subsequent solution cycles.

Braze Cycle

[0133] All braze cycles performed with the lower braze cycle temperature (2200 deg. F.) experienced complete remelt test failures even when higher base material alloy was added to the mixture. The higher braze cycle temperature used in the second (B) tests provided improved results in the remit evaluations.

[0134] The advantage to the higher temperature braze cycle, which in effect is equal to the standard solution heat treat cycle of the base material, is that the opportunity to braze before or after weld repairs is always present without the addition of heat treat cycles which add cost to the repair process and may have some unknown effect to the base material properties.

[0135] Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting, The use of including, comprising, or having and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.