Activators, preformed pastes, preforms, and processes for thin-walled, through-wall defect repair

Abstract

The application discloses an activator for repairing a thin-wall penetrating defect, a prefabricated paste, a prefabricated piece and a process, relates to the field of repairing a high-temperature blade of a gas turbine, and the activator at least comprises the following elements with the mass percentage: Cr (7.1-9.8%), Co (15.2-19.8%), Al (2.5-4.3%), W (0.2-1.7), Ti (6.2-8.7%), Ta (5.6-7.8%), Mo (5.6-8.8%), Ru (2.7-4.2%), Hf (5.6-7.8%), Zr (0.07-0.15%), C (0.10-0.15%), and Sc (0.01-0.05%). The prefabricated paste is prepared by mixing the activator, a solidifying agent and a binder. The prefabricated piece is prepared by using the prefabricated paste. The process comprises the steps of defect polishing, prefabricated piece forming, prefabricated piece repairing, defect adding and post-processing. The application makes the structure of the repairing area close to the base material, can adapt to the high-temperature working environment of the blade, has high mechanical performance strength of the joint, effectively avoids the thin-wall cracking and deformation of the blade caused by high heat input, prevents the air passage from being blocked, and solves the problem of difficult repair of the thin-wall penetrating defect of the nickel-based high-temperature alloy blade.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas turbine high-temperature blade repair, and particularly to an activator for repairing thin-wall penetrating defects, a pre-prepared paste, a pre-prepared piece and a process. BACKGROUND

[0002] Nickel-based high-temperature alloy blades are core components for manufacturing heavy-duty gas turbines, and are known as the "aorta" of turbine components, responsible for extracting the energy after combustion of the gas, and the working temperature is extremely harsh. Especially the first stage turbine blade, which has to withstand the impact of high-temperature gas flow close to 1400℃, far exceeding the heat resistance limit of nickel-based high-temperature alloy (about 1100℃), so effective cooling measures must be taken to ensure the reliable work of the blade in high-temperature environment. The use of composite gas film cooling hollow structure is an effective cooling way to make the blade meet the high-temperature and high-pressure working conditions. When the blade is in service, the cooling air flows inside to take away the heat, and at the same time, a layer of gas film is formed by escaping through the gas film hole on the blade, which isolates the high temperature to reduce the surface temperature of the turbine blade during the working process.

[0003] During the long-term service of high-temperature blades, foreign object impact, airflow scouring, cold and hot fatigue, etc. are very easy to cause cracking, ablation and subtractive damage of the blade substrate, and these damages often cause penetrating damage to the thin wall if they occur in the thin wall part of the hollow blade. Due to the poor weldability of nickel-based high-temperature alloy, the process window of fusion welding repair is particularly narrow, and it is even more difficult to repair the blade thin wall with it, and high heat input is easy to cause thin wall deformation. Although the large gap brazing or powder metallurgy repair technology can effectively avoid the occurrence of welding cracks, but this kind of repair technology needs to introduce more low-melting-point filler metal during the repair process, and when it is used to repair the penetrating defects on the blade thin wall, the filler metal will flow into the air duct after liquefaction, causing air duct obstruction and damaging the structure of the hollow blade. SUMMARY

[0004] The present application aims to: in view of the above problems, provide an activator for repairing thin-wall penetrating defects, a pre-prepared paste, a pre-prepared piece and a process, so that the repaired area is close to the substrate, can adapt to the high-temperature working environment of the blade and has high mechanical strength of the joint, effectively avoids the cracking and deformation of the blade thin wall caused by high heat input, prevents air duct obstruction, and solves the problem of difficult repair of nickel-based high-temperature alloy blade thin-wall penetrating defects.

[0005] The technical scheme adopted by the present application is as follows: an activator for repairing thin-wall penetrating defects, the preparation of the activator includes at least the following elements with the mass percentage:

[0006] Cr (7.1% - 9.8%), Co (15.2% - 19.8%), Al (2.5% - 4.3%), W (0.2 - 1.7), Ti (6.2% - 8.7%), Ta (5.6% - 7.8%), Mo (5.6% - 8.8%), Ru (2.7% - 4.2%), Hf (5.6% - 7.8%), Zr (0.07% - 0.15%), C (0.10% - 0.15%), Sc (0.01% - 0.05%), the rest is Ni or / and inevitable impurity elements.

[0007] A prefabricated paste for thin-wall penetrating defect repair, which is in the form of a paste and is prepared by mixing an activator, a curing agent and a binder for thin-wall penetrating defect repair in a desired proportion; wherein:

[0008] The curing agent is M-21 or Mar-M004 commercial alloy powder with a particle size in the range of 85-106 microns; the binder is NICROBRA S-BINDR type commercial; the mass of the activator is 40%-50%, the mass of the binder is 3%-5%, and the rest is the curing agent.

[0009] A prefabricated piece for thin-wall penetrating defect repair, which is prepared by using a mold to make the prefabricated paste for thin-wall penetrating defect repair into a prefabricated piece.

[0010] Specifically, the mold is a ceramic mold, the prefabricated paste is placed in the ceramic mold and evenly spread to a thickness of 5-9 mm; then the ceramic mold with the prefabricated paste is placed in a vacuum furnace with a vacuum degree better than 1x10 -3 Pa for sintering, the vacuum furnace provides a vacuum environment, the sintering temperature is 1140-1170°C, and the sintering time is 10-15 min; after sintering, the temperature in the vacuum furnace is reduced to 1000-1050°C for hot isostatic pressing, the pressure in the vacuum furnace during hot isostatic pressing is 10-20 MPa, the holding time for hot isostatic pressing is 30-60 min, and after hot isostatic pressing, the vacuum furnace is cooled to form a prefabricated piece, the thickness of the prefabricated piece is about 3-7 mm.

[0011] A process for repairing thin-wall penetrating defects on a hollow thin-wall blade of a substrate of a precipitation-strengthened nickel-based cast high-temperature alloy such as Mar-M247, MGA2400, GTD444, etc., comprising the following steps:

[0012] S1: defect polishing;

[0013] The through-wall defect area is mechanically polished to remove the oxide layer and polish the area around the through-wall defect into a bevel, the slope of the bevel should be less than 60°, the length and width of the polished bevel should be no more than 20mm*10mm, the thickness of the thin wall at the through-wall defect should be within 2mm-5mm, and after polishing, the bevel is placed in an alcohol or acetone solution for ultrasonic cleaning for 60 minutes, taken out and dried for standby use.

[0014] S2: preform forming; the preform for repairing the through-wall defect is prepared;

[0015] S3: preform shaping;

[0016] According to the specific size of the bevel formed after the defect polishing of step S1, the preform of step S2 is polished and shaped, the thickness of the preform after shaping is 0.5mm-1mm thicker than the thickness of the thin wall at the through-wall defect, the lower surface of the preform should be flush with the end surface of the small diameter end of the bevel, that is, the upper surface of the preform after shaping should be 0.5mm-1mm higher than the end surface of the large diameter end of the bevel; the preform matches the shape and size of the bevel at the remaining positions; the preform after polishing and shaping is placed in an alcohol or acetone solution for ultrasonic cleaning for 60 minutes, taken out and dried for standby use.

[0017] S4: defect addition;

[0018] The preform after shaping of step S3 is assembled to the bevel of step S1, and then is subjected to metallurgical insulation in a vacuum furnace with a vacuum degree better than 1*10 -3 Pa, the vacuum furnace provides a vacuum environment; the insulation temperature of the metallurgical insulation is 1190℃-1210℃, the insulation time is 45min-60min, and the preform is cooled in the furnace after the insulation is completed.

[0019] S5: post-processing;

[0020] After the metallurgical insulation and cooling of step S4 are completed, the blade is subjected to a performance recovery heat treatment, and the excess metal in the repair area is removed by shaping, that is, the shape and properties of the defect are remodeled.

[0021] In summary, due to the adoption of the above technical solutions, the present application has the following advantages:

[0022] 1. Compared with the conventional repair material, the activator disclosed in the present application does not add high-concentration B, Si and Zr as melting point depressants, but adjusts the mass ratio of the strengthening elements in the high-temperature alloy to achieve high-entropy of the alloy, so as to suppress the melting point of the activator to the range allowed by the process; therefore, the repair area obtained by using the preform of the present application does not contain low-melting-point B, Si and Zr compounds and / or eutectic phases, the structure of the repair area is close to that of the base material, can withstand the high-temperature working environment of the blade, and the mechanical strength of the joint is high;

[0023] 2、The process disclosed by the application has the beneficial effects of avoiding blade thin-wall cracking and deformation caused by high heat input compared with the existing melting welding technology; and has the beneficial effects of avoiding a large amount of liquid phase flowing into the blade air channel during the metallurgical process, causing air channel obstruction compared with the existing large-gap brazing or powder metallurgy repair technology; and effectively solves the problem of difficult repair of the thin-wall penetrating defects of the nickel-based high-temperature alloy blade. BRIEF DESCRIPTION OF DRAWINGS

[0024] The application will be described by way of example and with reference to the accompanying drawings in which:

[0025] Figure 1 Microstructure of the DFX-M preform provided by the application;

[0026] Figure 2 Schematic diagram of the thin-wall penetrating defects of the N1 guide vane provided by the application;

[0027] Figure 3 Schematic diagram of step S1 in the process provided by the application;

[0028] Figure 4 Schematic diagram of step S2 or S3 in the process provided by the application;

[0029] Figure 5 Schematic diagram of step S4 in the process provided by the application;

[0030] Figure 6 Schematic diagram of step S5 in the process provided by the application;

[0031] Figure 7 Microstructure of the repair area obtained by repairing the thin-wall penetrating defects of the N1 guide vane provided by the application.

[0032] Markings in the figure: 1-thin wall; 2-air channel; 3-base body; 4-penetrating defects; 5-bevel; 6-preform. DETAILED DESCRIPTION

[0033] All the features disclosed in this specification, or all the steps of any method or process disclosed in this specification, may be combined in any combination, except where features or steps are mutually exclusive.

[0034] Any feature disclosed in this specification, unless stated otherwise, can be replaced by any equivalent or similar feature, or any feature with the same purpose. That is, unless stated otherwise, each feature is one example only of a number of equivalent or similar features.

[0035] Example 1

[0036] An activator for repairing thin-wall penetrating defects, the preparation of the activator at least includes the following elements with mass percentage: An activator for repairing thin-wall penetrating defects, the preparation of the activator at least includes the following elements with mass percentage:

[0037] Cr (7.1% - 9.8%), Co (15.2% - 19.8%), Al (2.5% - 4.3%), W (0.2 - 1.7), Ti (6.2% - 8.7%), Ta (5.6% - 7.8%), Mo (5.6% - 8.8%), Ru (2.7% - 4.2%), Hf (5.6% - 7.8%), Zr (0.07% - 0.15%), C (0.10% - 0.15%), Sc (0.01% - 0.05%), the rest is Ni or / and inevitable impurity elements.

[0038] In the present embodiment, the activator is in powder form, with a particle size of 30 μm - 53 μm, and can be prepared by an atomization method; the melting temperature range is 1130 °C - 1160 °C.

[0039] It should be noted that the atomization method is a conventional method in the art, and will not be described in more detail herein.

[0040] In order to further clearly set forth and illustrate the technical solutions of the present application, the following non-limiting embodiments of the activator are provided, and the element content data below are all mass percentage data.

[0041] Table 1: Embodiments of the activator

[0042]

[0043]

[0044] According to the above embodiments of the activator, it can be known that the activator of the present embodiment, compared with conventional repair materials, does not add high concentrations of B, Si and Zr as melting point depressants, but adjusts the mass proportions of high-temperature alloy strengthening elements to achieve high-entropy of the alloy, so as to depress the melting point of the activator to the range allowed by the process. Therefore, when the activator of the present application is applied to repair defects, the repair area obtained does not contain low-melting-point B, Si and Zr compounds and / or eutectic phases, the repair area structure is close to that of the base material, can withstand the high-temperature working environment of the blade, and the mechanical performance strength of the joint is high.

[0045] Example 2

[0046] A pre-prepared paste for repairing thin-walled penetrating defects, in order to further clearly set forth and illustrate the technical solutions of the present application, the following non-limiting embodiments of the activator are provided.

[0047] In a first embodiment, a DFX-M pre-prepared paste is prepared.

[0048] Materials selected:

[0049] Activator: the activator with the brand of DFB-A in Example 1; Curing agent: Mar-M004 commercial alloy powder; Binder: NICROBRAZ S-BINDR type commercial;

[0050] Wherein: Mar-M004 commercial alloy powder, particle size between 85 μm and 106 μm, composition:

[0051] C (0.05 wt%), Cr (12.0 wt%), Mo (4.5 wt%), Nb (2.0 wt%), Al (5.9 wt%), Ti (0.6 wt%), Hf (1.3 wt%), Zr (0.05 wt%), B (0.015 wt%).

[0052] Material usage: the weight of the activator powder accounts for 40%, the mass of the binder accounts for 3.5%, and the rest is the curing agent.

[0053] The paste made by mixing the above-mentioned activator, curing agent and binder in the above-mentioned usage is used as the preform paste to make the corresponding DFX-Y preform.

[0054] The second embodiment is to prepare the DFX-Y preform paste.

[0055] Material selection:

[0056] Activator: the activator with the brand of DFB-A in Example 1; Curing agent: Mar-M004 commercial alloy powder; Binder: NICROBRAZ S-BINDR type commercial;

[0057] Wherein: Mar-M004 commercial alloy powder, particle size between 85 μm and 106 μm, composition:

[0058] C (0.05 wt%), Cr (12.0 wt%), Mo (4.5 wt%), Nb (2.0 wt%), Al (5.9 wt%), Ti (0.6 wt%), Hf (1.3 wt%), Zr (0.05 wt%), B (0.015 wt%).

[0059] Material usage: the weight of the activator powder accounts for 40%, the mass of the binder accounts for 3.5%, and the rest is the curing agent.

[0060] The paste made by mixing the above-mentioned activator, curing agent and binder in the above-mentioned usage is used as the preform paste to make the corresponding DFX-Y preform.

[0061] Example 3

[0062] A thin-wall through-wall defect repair preform, in order to further clearly illustrate and describe the technical solutions of the present application, the following non-limiting embodiments of the activator are provided.

[0063] The first embodiment is to prepare a DFX-M preform.

[0064] The DFX-M preform paste in Example 2 is placed in a ceramic mold and evenly spread, with a thickness of about 5 mm; then sintering is performed in a vacuum furnace with a vacuum degree better than 1×10 -3 Pa, the sintering temperature is 1150℃, and the sintering time is 10 min; after sintering is completed, the temperature in the vacuum furnace is lowered to 1050℃ for hot isostatic pressing treatment, the pressure in the vacuum furnace is 15 MPa, and the holding time is 30 min, and then the furnace is cooled to obtain a preform 6 with a thickness of about 3 mm. The microstructure of the DFX-M preform is shown in Figure 1 .

[0065] The second embodiment is to prepare a DFX-Y preform.

[0066] The DFX-Y preform paste in Example 2 is placed in a ceramic mold and evenly spread, with a thickness of about 5 mm; then sintering is performed in a vacuum furnace with a vacuum degree better than 1×10 -3 Pa, the sintering temperature is 1170℃, and the sintering time is 10 min; after sintering is completed, the temperature in the vacuum furnace is lowered to 1000℃ for hot isostatic pressing treatment, the pressure in the vacuum furnace is 20 MPa, and the holding time is 30 min, and then the furnace is cooled to obtain a preform 6 with a thickness of about 3 mm.

[0067] Example 4

[0068] A thin-wall through-wall defect repair process, in order to further clearly illustrate and describe the technical solutions of the present application, taking the first stage turbine guide vane N1 of a 50MW heavy-duty gas turbine as an example, as follows.

[0069] The N1 guide vane is a hollow vane, which has a base body 3 and a thin wall 1, and there is an air passage 2 between the thin wall 1 and the base body 3, and a defect penetrates the thin wall 1 to form a through-wall defect 4; the base material of the thin wall 1 is Mar-M247 precipitation strengthened nickel-based cast high-temperature alloy, and the nominal chemical composition is:

[0070] Ni-8wt%Cr-10wt%Co-10wt%W-5.5wt%Al-1wt%Ti-3wt%Ta-1.5wt%Hf-0.6wt%Mo-0.15wt%C-0.015wt%B-0.03wt%Zr.

[0071] As shown in Figures 2-7 , the repair process is completed by the following steps, see steps S1-S5 in detail.

[0072] S1: Defect grinding;

[0073] The through-wall defect 4 on the thin wall 1 of the N1 guide vane is mechanically ground to remove the oxide layer, and the thin wall 1 around the through-wall defect 4 is ground to a bevel 5 with a slope of 45°, the large-diameter end of the bevel 5 is located on the outer surface of the N1 guide vane, and the small-diameter end of the bevel 5 is located on the inner wall of the cavity of the N1 guide vane; the length x width of the ground bevel 5 is 10 mm x 2 mm, and the thickness of the thin wall 1 at the bevel 5 is 2.2 mm; after grinding, the bevel 5 is placed in alcohol for ultrasonic cleaning for 60 minutes, taken out and dried for standby.

[0074] S2: Preform forming; using the description in Example 3, a DFX-M preform is made.

[0075] S3: Preform shaping;

[0076] According to the geometric dimensions of the bevel 5 in step S1, the DFX-M preform 6 in Example 3 is ground, and the thickness of the shaped preform 6 is 2.7 mm, the lower surface of the preform 6 is flush with the inner wall of the cavity at the defect of the vane, then the ground and shaped preform 6 is placed in an alcohol solution for ultrasonic cleaning for 60 minutes, taken out and dried for standby.

[0077] S4: Defect addition;

[0078] The shaped preform 6 in step S2 is assembled to the bevel 5 in step S1, the large-diameter end of the bevel 5 is 0.5 mm higher than the outer surface of the N1 guide vane; then metallurgical insulation is carried out in a vacuum furnace with a vacuum degree better than 1 x 10-3Pa, the insulation temperature is 1210℃, the insulation time is 50 minutes, and the furnace is cooled after the insulation is completed.

[0079] S5: Post-processing;

[0080] After metallurgical insulation and cooling, the vane is subjected to performance recovery heat treatment, and the excess metal in the repair area is removed by shaping, so that the shape and properties of the through-wall defect 4 on the thin wall 1 of the N1 guide vane are remodeled.

[0081] Test:

[0082] After the repair is completed, the joint in the repair area is made into a tensile piece, and the room temperature tensile strength is measured to be 795 MPa, reaching 80.3% of the base material strength; the high temperature tensile strength at 900℃ reaches 473 MPa, reaching 70.1% of the base material strength.

[0083] To sum up, the process disclosed in the embodiment avoids the cracking and deformation of the thin wall 1 caused by high heat input, compared with the existing melting welding technology; compared with the existing large-gap brazing or powder metallurgy repair technology, the preformed repair part 6 and the constraint of the groove 5 avoid the flow of a large amount of liquid phase into the air passage 2 during the metallurgical process, causing the air passage 2 to be blocked; that is, the problem of difficult repair of the through-wall defect 4 of the nickel-based high-temperature alloy blade thin wall 1 is effectively solved.

[0084] The present application is not limited to the foregoing specific embodiments. The present application extends to any novel one, or any novel combination, of the characteristics disclosed in this specification, as well as to any novel method or process steps disclosed, or any novel combination thereof.

Claims

1. An activator for repairing thin-walled through-hole defects, applied to hollow thin-walled blades whose substrate is a precipitation-strengthened nickel-based cast high-temperature alloy, characterized in that: The preparation of the activator includes at least the following elements in mass percentage: Cr: 7.1%-9.8%, Co: 15.2%-19.8%, Al: 2.5%-4.3%, W: 0.2%-1.7%, Ti: 6.2%-8.7%, Ta: 5.6%-7.8%, Mo: 5.6%-8.8%, Ru: 2.7%-4.2%, Hf: 5.6%-7.8%, Zr: 0.07%-0.15%, C: 0.10%-0.15%, Sc: 0.01%-0.05%, and the rest are Ni and unavoidable impurity elements.

2. A prefabricated paste for repairing thin-walled penetrating defects, characterized in that: The prefabricated paste is in paste form and is prepared by mixing the activator for repairing thin-wall penetrating defects according to claim 1, a curing agent and a binder in a required proportion.

3. The prefabricated paste according to claim 2, characterized in that The curing agent is commercial M-21 or Mar-M004 alloy powder with a particle size ranging from 85 μm to 106 μm; the binder is commercial NICROBRAZ S-BINDR type; wherein: The mass of the activator accounts for 40%-50%, the mass of the binder accounts for 3%-5%, and the balance is the curing agent; M-21 commercial alloy powder, particle size between 85μm and 106μm, nominal chemical composition: C: 0.13wt%, B: 0.02wt%, Cr: 5.7wt%, Mo: 2.0wt%, Al: 6.0wt%, W: 11.0wt%, Nb: 1.5wt%, Zr: 0.12wt%, and the rest are Ni and unavoidable impurity elements; Mar-M004 commercial alloy powder, particle size between 85μm and 106μm, composition: C: 0.05wt%, Cr: 12.0wt%, Mo: 4.5wt%, Nb: 2.0wt%, Al: 5.9wt%, Ti: 0.6wt%, Hf: 1.3wt%, Zr: 0.05wt%, B: 0.015wt%.

4. A prefabricated part for repairing thin-walled penetrating defects, characterized in that: The prefabricated paste for repairing thin-walled penetrating defects according to claim 2 or 3 is made into a prefabricated part (6) using a mold.

5. The preform according to claim 4, characterized in that The mold containing the prefabricated paste is placed in a vacuum environment for sintering at a sintering temperature of 1140°C-1170°C and a sintering time of 10 min-15 min. After sintering, the ambient temperature is lowered to 1000°C-1050°C for hot isostatic pressing. The ambient pressure for hot isostatic pressing is 10 MPa-20 MPa, and the holding time for hot isostatic pressing is 30 min-60 min. After hot isostatic pressing, the mold is cooled in the furnace to form a prefabricated part (6).

6. The preform according to claim 5, characterized in that The vacuum environment is provided by a vacuum furnace, and the vacuum degree of the vacuum environment is better than 1×10 -3 Pa.

7. A process for repairing thin-wall penetrating defects, characterized in that: The following steps are involved: S1: defect polishing; Grind the penetrating defect (4) area to form a groove (5) in the penetrating defect (4), clean it, blow it dry and set it aside; S2: Preform molding; manufacturing the preform for repairing the thin-walled through-hole defect according to claim 6; S3: Prefabricated parts modification; According to the specific size of the groove (5) formed after grinding the through-hole defect (4) in step S1, the prefabricated part (6) is ground and shaped to match the shape and size of the groove (5), and the upper surface of the prefabricated part (6) is 0.5mm-1mm higher than the surface of the groove (5), and then cleaned and dried for later use; S4: defect additive; Assemble the prefabricated part (6) after the modification in step S3 to the groove (5) in step S1, then perform metallurgical insulation in a vacuum environment, and cool it with the furnace after the insulation is completed; S5: post-processing; After the cooling in step S4 is completed, a performance recovery heat treatment is performed to repair the shape and remove excess metal in the repair area to complete the shape reshaping.

8. The process according to claim 7, characterized in that In step S1, the slope of the groove (5) is less than 60°.

9. The process according to any one of claims 7-8, characterized in that This process is used to repair thin-wall penetration defects on hollow thin-walled blades whose substrate is precipitation-strengthened nickel-based cast high-temperature alloy.

10. The process according to claim 9, characterized in that The vacuum degree of the vacuum environment is better than 1×10 -3 Pa; the metallurgical holding temperature is 1190℃-1210℃, and the holding time is 45min-60min.

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