KR102278830B1 - Method of repairing gas turbine blade tip using high frequency welding - Google Patents

Abstract

The present invention relates to a method for repairing a gas turbine blade by using high-frequency welding, and more specifically, to a method for repairing a gas turbine blade by using high-frequency welding, which comprises: a first step of removing a top coating on the gas turbine blade; a second step of removing a bond-coated layer of the gas turbine blade; a third step of blasting the surface of the gas turbine blade; a fourth step of identifying whether the bond-coated layer is removed or not; a fifth step or removing the bond-coated layer which is not removed again; a sixth step of performing heat treatment before welding; a seventh step of performing a non-destructive test on the gas turbine blade in order to detect a defective portion: an eighth step of machining and cutting a tip of the turbine blade, where there is the defective portion; a nineth step of performing high-frequency welding on the machined and cut defective portion; a tenth step of performing heat treatment after welding; an eleventh step of grinding a welded surface: a twelfth step of performing washing with fluorine ions; a thirteenth step of scanning the machined and cut surface in a 3D mode and making an input; a fourteenth step of performing laser cladding: and a fifteenth step of fitting a measurement to a shape of a tip of the original gas turbine blade. As the above-mentioned, according to the method for repairing a gas turbine blade by using high-frequency welding, bonding strength between an existing body and a repaired portion is so high, that the repaired one keeps safe for a long time of use. In an economic sense, the long-term use after repaired prevents frequent repairing of the blade and saves replacement costs.

Description

Method of repairing gas turbine blade tip using high frequency welding

The present invention relates to a gas turbine blade repair method using high-frequency welding, and more particularly, it is shown in FIG. 2 by removing foreign substances from the surface of the blade where the defective part is generated, and then processing and cutting to make the defective surface of the blade smooth. As shown above, the deep groove on the surface where the defective part of the blade is formed is filled with high-frequency welding using the same material as the welding material of the blade. After filling the groove with high-frequency welding, the blade disappeared by processing and cutting with laser cladding. It relates to a gas turbine blade repair method using high-frequency welding, characterized in that it is formed as much as the size of the tip.

A gas turbine is a prime mover that compresses air, sends it to a combustor, and adds fuel to it to produce high-temperature and high-pressure combustion gas through isostatic combustion, and drives the turbine to generate output.

At this time, a blade is conventionally used as a component of a device that converts the energy of the fluid into mechanical power energy.

The blade used in the above-described gas turbine must have the property to withstand high temperature and high pressure, so it must be made of a super heat-resistant alloy such as a nickel-based, cobalt-based or nickel-cobalt-based alloy. It is more economical to repair and reuse the damaged part than to replace the entire blade with a new one in order to reduce the cost when repairing the blade due to damage.

As a prior art related to the repair of such a gas turbine blade, the intermediate member 5 is located between the welding base materials 4 in the vacuum chamber 1 in Korean Patent Registration No. 10-0504381, and the pressure for applying the bonding pressure There is a rod (2) and a support (7), and an induction coil (3, Induction Coil) by a red pepper wave induction heater (10, High Frequency Induction Generator) is installed as a device for heating the welding material, and the welding process is performed. A repair method that performs the bonding step, homogenization heat treatment step, and heat treatment step by a bonding device configured so that a thermocouple (9, Thermocouple, thermometer) is fixed to the welding material and the XY Recorder (8) for process recording is connected In the above, in the bonding step, as the bonding temperature in the temperature range of 1423K or 1473K, it is maintained for within 120 minutes, then slowly cooled to 1273K and then air cooled, and the bonding pressure is kept constant at 20 kPa, and in the homogenization heat treatment step, the solution heat treatment temperature After maintaining at 1393K, furnace cooling, and the heat treatment step is heating to 1473K and immediately cooling at a cooling rate of 10K/min to join, followed by step 1 of 16 hours at 1113K temperature, and 10 hours at 1033K temperature A directional and single crystal gas turbine blade repair method by a transition liquid phase diffusion method, characterized in that two steps to make it happen, and a three-step aging heat treatment step in three steps to be made at 922K temperature for 24 hours have been registered and published. have.

As another prior art, as a method for repairing the wear surface of low alloy iron steam turbine parts in Korean Patent Publication No. 1997-0010880, (a) 1.0 to 1.35% by weight of Cr, 1.00 to 1.30% by weight of Mo, and providing a steam turbine component containing 0.21% to 0.29% V by weight and having a worn surface; (b) depositing a first weld metal layer on the worn surface to generate a heat-affected zone in the turbine component; (c) a second weld using heat at a higher temperature than was used in depositing the first weld metal layer on the first weld metal layer so as to temper at least a portion of the heat affected zone in the turbine component. There is disclosed a method for repairing abrasion surfaces of a turbine part, characterized in that it consists of a second welding metal layer deposition step of depositing a metal layer.

As described above, the repair process of the conventional gas turbine blade is complicated, and it takes a lot of time to repair due to cracks or losses in a very small part, and even if the repair is done, the connection between the existing body and the repaired part is difficult. Because it is weak, it has disadvantages such as that it cannot be used for a long time for safety reasons as an emergency measure for short-term use.

The present invention has been devised to solve the above-described problems, and an object of the present invention is to provide a method for repairing a gas turbine blade that is safe even for long-term use after repair because the bonding strength between the existing body and the repaired part is very high.

A gas turbine blade repair method using high-frequency welding according to the present invention includes a first step of removing the top coating of the gas turbine blade; Step 2 of removing the bond coating layer of the gas turbine blade; Step 3 of blasting the surface of the gas turbine blade; Step 4 of inspecting whether the bond coating layer is removed; Step 5 of removing the non-removed bond coating layer again; 6 steps of heat treatment before welding; Step 7: Non-destructive inspection of gas turbine blades to detect defects: Step 8: Machining and cutting the tip of the gas turbine blades with defects; Step 9 of high-frequency welding of the processed and cut defective parts; 10 steps of heat treatment after welding; Step 11 of grinding the weld surface: Step 12 of cleaning with fluoride ions; 13 step of 3D scanning and inputting the cut surface; It is characterized by a 14-step laser cladding: 15-step process of adjusting the dimensions to the same shape as the original gas turbine blade tip shape.

As described above, the gas turbine blade repair method using high-frequency welding of the present invention has a very high bonding strength between the existing body and the repaired part, so it is safe to use for a long time after repair. There are remarkable effects such as reducing repair and replacement costs.

1 is a process diagram of a gas turbine blade repair method using high-frequency welding according to the present invention.
2 is a schematic diagram of a gas turbine blade.
Figure 3 is a schematic diagram showing the correlation between the crack and welding of the gas turbine blade according to the gas turbine blade repair method using the present invention high-frequency welding.

A gas turbine blade repair method using high-frequency welding according to the present invention includes a first step of removing the top coating of the gas turbine blade; Step 2 of removing the bond coating layer of the gas turbine blade; Step 3 of blasting the surface of the gas turbine blade; Step 4 of inspecting whether the bond coating layer is removed; Step 5 of removing the non-removed bond coating layer again; 6 steps of heat treatment before welding; Step 7: Non-destructive inspection of gas turbine blades to detect defects: Step 8: Machining and cutting the tip of the gas turbine blades with defects; Step 9 of high-frequency welding of the processed and cut defective parts; 10 steps of heat treatment after welding; Step 11 of grinding the weld surface: Step 12 of cleaning with fluoride ions; 13 step of 3D scanning and inputting the cut surface; It is characterized by the 14-step laser cladding: 15-step process of adjusting the dimensions to the same shape as the original gas turbine blade tip shape.

And the high frequency welding in the 9-step process uses the same solvent as the base material Inconel 738, and the laser cladding in the 14-step process uses Inconel 625 powder.

In addition, the grit blasting in the first step process ^{is carried out under the conditions of a pressure of 3 to 5 kg/cm 2} , alumina particle size of 30 to 50 mesh, and the grit blasting in the third step is a pressure of 3 to 5 kg/cm ² , alumina It is characterized by working under the condition of particle size 120~200mesh.

Hereinafter, the gas turbine blade repair method using the high frequency welding of the present invention will be described in detail with reference to the accompanying drawings.

1 is a process diagram of a gas turbine blade repair method using high frequency welding according to the present invention, FIG. 2 is a schematic diagram of a gas turbine blade, and FIG. 3 is a crack and welding of a gas turbine blade according to the gas turbine blade repair method using high frequency welding according to the present invention It is a schematic diagram showing the correlation.

For reference, Fig. 3 (a) is a state in which the tip of the blade is broken, Fig. 3 (b) is a state in which the tip of the blade is processed and cut, and Fig. 3 (c) is a groove formed deeper than the processed cut surface. is filled by high-frequency welding, and (d) of FIG. 3 shows a state in which the blade tip is formed by laser cladding.

1 to 3, the present invention relates to a gas turbine blade repair method using high-frequency welding.

More specifically, as a one-step process, the top coating of the gas turbine blade together with rust or foreign substances on the surface of the gas turbine blade is removed by grit blasting.

At this time, the grit blasting is performed ^{to remove the ceramic top coating layer with a pressure of 3 to 5 kg/cm 2} , and an alumina particle size of 30 to 50 mesh.

Grit blasting refers to the removal of scale by spraying sharply angled iron pieces onto the metal surface to remove scale or to make the machined surface beautiful.

The second step process is to remove the uppermost coating of the gas turbine blade by the grit blasting of the first step, and then remove the bond coating layer of the gas turbine blade made of MCrAlY by chemical stripping.

The hydrochloric acid concentration is 30~35% and the temperature is 60~70℃.

The three-step process is again blasting the surface of the gas turbine blades.

At this time, the grit blasting is performed with a pressure of 3 to 5 kg/cm ² , and alumina particle size of 120 to 200 mesh.

The smaller the mesh number, the larger the grain of alumina, which is the grit. In the first stage process, the alumina particles are larger than the alumina particles in the third stage process, so the blasting in the third stage process is more sophisticated removal of foreign substances, etc. this will be done

Blast with grit as in step 1 process.

Step 4 is a process of inspecting whether the bond coating layer has been removed, and the gas turbine blade is maintained at a temperature of 600 to 650 ° C in an electric furnace for 2 hours to inspect whether the bond coating layer has been removed.

The five-step process is a process of removing the bond coating layer that has not been removed again, so that the bond coating layer that has not been removed is removed by grinding.

Step 6 is a heat treatment process before welding.

In other words, the 6-step process is a solution heat treatment before welding, which is a heat treatment process before non-destructive inspection to open hidden microcracks.

The heat treatment conditions are vacuum degree 1.0 xe ^-4~-6 , temperature 1100~1180℃, hold for 2~3 hours, and then cool with gas.

The seven-step process is a process of non-destructive testing of gas turbine blades to detect defects.

In general, it is called fluorescence penetrant inspection.

The 8-step process is a process of machining and cutting the tip of the gas turbine blade with the defect.

Only the defective parts identified in the non-destructive inspection are processed and cut.

The 9-step process is a process of high-frequency welding of the processed and cut defective parts.

At this time, the welding material in the high-frequency welding is to be welded with the same material as the blade.

That is, in general, in high-frequency welding, Inconel 738, the same material as the blade, is used for welding.

As a preferred implementation, the blade is placed inside the coil that forms a high frequency installed in the chamber, and the current is applied while purging the argon gas, heating and maintaining the blade temperature so that the blade temperature is 950 ~ 1050 ℃ using Inconel 738 wire. Welding should be completed within 20-30 minutes.

As described above, in the high-frequency welding process of the present invention, since welding is performed in an argon atmosphere at a high temperature using a welding material of the same material as the base material, the bonding between the base material and the welding material is excellent.

The 10-step process is a heat treatment process after high-frequency welding.

After raising the temperature in the welded state, keep it at 1090~1140℃ for 20~30 minutes, and then cool it with argon gas from 950~1050℃ to room temperature.

Step 11 is a process of grinding the processed part of the heat-treated blade.

The 12-step process is a process of cleaning the blade with fluoride ions.

It is a process to improve brazing or welding performance by removing oxides in cracks and depleting trace elements such as Al, Ti, Cr on the welding surface.

More specifically, by using HF gas at a pressure of 100 to 600 Torr and a temperature of 900 to 1150° C., oxides in cracks of high-temperature parts, especially A ₂ O ₃ , TiO ₂ , Cr ₂ O _{3 ,} etc. are removed, and the reaction formula Is as follows.

6HF + Al ₂ O ₃ → 2AlF ₃ + 3H ₂ O

4HF + TiO ₂ → TiF ₄ + 2H ₂ O

6HF + Cr ₂ O ₃ → 2CrF ₃ +3H ₂ O

In addition, HF gas is used on the welding surface to deplete trace elements such as Al, Ti, and Cr as shown in the following reaction formula.

6HF + 2Al → 2AlF ₃ + 3H ₂

8HF + 2Ti → 2TiF ₄ + 4H ₂

6HF + 2Cr → 2CrF ₃ +3H ₂

The 13-step process is a process of 3D scanning and inputting the machined/cut surface.

In other words, it is a process that supports a computer program so that the laser cladding can be performed by scanning the cut welding surface with a laser to set the welding path, calculate the shape and volume to be laminated, and then automatically input into the program and follow the set welding path. .

The 14-step process is a process of laser cladding the welding path set in the 13-step process.

The condition of laser cladding is a process of melting and laminating powder on the welding surface. Powder Inconel 625, powder size 30~150um, powder injection speed 3~10g/min, input power 500~1000 W, gun speed 500~1000mm/min. let it proceed

The reason for using the same IN 738 as the base material for high-frequency welding with a solvent and IN 625 for laser cladding is that IN 625 contains less than 0.4 wt% of Al and Ti, respectively, so that welding cracks do not occur. IN 738 contains more Al and Ti at about 3.5 wt% in alloy components than IN 625, so it is easily exposed to high-temperature cracks that occur during welding. This is because high-frequency welding is advantageous.

The 15-step process is a process of dimensioning the original gas turbine blade tip shape.

Briefly summarizing the gas turbine blade repair method using high-frequency welding of the present invention according to the above-described process, after removing foreign substances on the surface of the blade where the defective part is generated, processing and cutting to make the defective surface of the blade smooth. As shown in Fig., the deep groove on the surface where the defective part is formed is filled with high-frequency welding using a welding material of the same material as the blade, and after filling the groove with high-frequency welding, it is processed and cut with laser cladding. It is to form as much as the size of the tip of the missing blade.

As described above, the gas turbine blade repair method using high-frequency welding of the present invention has a very high bonding strength between the existing body and the repaired part, so it is safe to use for a long time after repair. There are remarkable effects such as reducing repair and replacement costs.

Claims (6)

Step 1 of removing the top coating of the gas turbine blade; Step 2 of removing the bond coating layer of the gas turbine blade; Step 3 of blasting the surface of the gas turbine blade; Step 4 of inspecting whether the bond coating layer is removed; Step 5 of removing the non-removed bond coating layer again; 6 steps of heat treatment before welding; Step 7: Non-destructive inspection of gas turbine blades to detect defects: Step 8: Machining and cutting the tip of the gas turbine blades with defects; Step 9 of high-frequency welding of the processed and cut defective parts; 10 steps of heat treatment after welding; Step 11 of grinding the weld surface: Step 12 of cleaning with fluoride ions; 13 steps of 3D scanning and input of the machining/cut surface; 14 steps of laser cladding: 15 steps of adjusting the dimensions to the same shape as the original gas turbine blade tip shape:
In the 9-step process, high-frequency welding uses the same solvent as the base material Inconel 738, and the laser cladding in the 14-step process uses Inconel 625 powder,
In the high-frequency welding in the 9-step process, the blade is placed inside a coil that forms a high-frequency wave installed in the chamber, and a current is applied while purging argon gas to heat and maintain the blade temperature to 950 ~ 1050 ° C. A gas turbine blade repair method using high-frequency welding, characterized by completing welding within 20 to 30 minutes using Inconel 738 wire.
delete delete According to claim 1,
The conditions of laser cladding in the 14-step process are a process of melting and laminating powder on the welding surface. Powder Inconel 625, powder size 30~150um, powder injection speed 3~10g/min, input power 500~1000 W, gun speed A gas turbine blade repair method using high-frequency welding, characterized by processing at 500-1000mm/min.
According to claim 1,
The grit blasting in the first step process is carried out under the conditions of a pressure of 3 to 5 kg/cm ² , alumina particle size of 30 to 50 mesh, and the grit blasting in the third step is a pressure of 3 to 5 kg/cm ² , alumina particle size A gas turbine blade repair method using high-frequency welding, which is characterized by working under conditions of 120-200 mesh.
According to claim 1,
In the 10-step process, the heat treatment process after high frequency welding is a gas using high frequency welding, characterized in that after heating in a welded state, the temperature is maintained at 1090 to 1140 ° C. for 20 to 30 minutes, and then cooled with argon gas from 950 to 1050 ° C. to room temperature. How to repair turbine blades.

Images