Film hole forming method for double-wall turbine blade with thermal barrier coating

Abstract

The invention relates to the technical field of aero-engines, in particular to a film hole forming method for a double-wall turbine blade with a thermal barrier coating. The film hole forming method comprises the steps that the first distance between the outer layer wall and the inner layer wall of the turbine blade is obtained; according to the fact that the first interval is smaller than or equal to the preset interval between the outer layer wall and the inner layer wall of the turbine blade, the following steps are executed: the second depth of a first air film hole obtained by machining the outer layer wall through a laser beam is obtained; the first stroke of the electrode is obtained when the electrode is machined on the outer layer wall along the first air film hole till the electrode is perforated in the outer layer wall to obtain a second air film hole, and a second distance is formed between the electrode and the inner layer wall; and obtaining a target gas film hole according to the perforation of the electrode in the outer layer wall and the consistency of the sum of the second depth and the third depth of the second gas film hole and the first depth. The method solves the problems that an air film hole with a thermal barrier coating cannot be machined through electric sparks, and a back wall, interface layering, taper and the like are prone to being damaged through laser machining.

Description

Technical Field

[0001] The present invention relates to the technical field of aero-engine, and in particular, to a method for forming film holes of a double-wall turbine blade with a thermal barrier coating. Background Art

[0002] The manufacturing of turbine blades in modern gas turbine engines relies on the "three core technologies": advanced air-cooled structure, high-performance high-temperature materials, and thermal barrier coatings (TBCs). These technologies ensure the long-term life and high-strength reliable operation of the engine in complex environments. Due to the continuous increase in the turbine inlet temperature, the heat resistance of current superalloy materials has encountered challenges. Therefore, in the process of developing new high-temperature structural materials, a comprehensive thermal protection strategy that integrates film cooling and thermal barrier coatings is mainly adopted to improve its thermal protection performance.

[0003] Currently, for the machining of film holes on blades coated with thermal barrier coatings, the main method is to first drill the film holes and then coat the thermal barrier layer. However, this method requires pre-expanding the hole diameter to compensate for the hole diameter shrinkage phenomenon generated after coating deposition. Although this method can, to some extent, mitigate the adverse effects on the effectiveness of the air-cooled structure, considering that the statistical law of the shrinkage effect does not have universal applicability, it still poses challenges to the film structure and cooling efficiency. In severe cases, it may even lead to blockage of the cooling channels, making it difficult for the final hole specifications to meet the preset standards. Furthermore, some scholars have studied the machining of film holes coated with TBCs. After using a millisecond laser to drill holes and perform thermal cycling on TBC superalloy materials, it is easy for the ceramic coating to show chipping and delamination phenomena during the hole-making process. These damages will cause microcracks to be more likely to occur in the thermally grown oxide layer between the ceramic coating and the bond coat during the thermal cycling process, thereby reducing the service life of the thermal barrier coating. When laser machining the thermal barrier coating, the stress caused by the ejection of the melt is the key factor leading to the separation of the ceramic layer and the bond coat, while the delamination between the bond coat and the substrate is mainly caused by the thermal effect. When using the ultrafast laser machining technology for film holes of turbine blades, due to the narrow inner cavity gap of the double-wall blade, the laser hole-making is extremely likely to damage the opposite wall, and it is difficult to prevent damage. Therefore, how to implement effective protection measures is a key technical problem faced by laser machining of film holes on blades.

[0004] For ceramic materials containing conductive phases (such as TiB2, TiN, or TiC), electrical discharge machining (EDM) can be directly used for drilling. However, it should be noted that EDM is not suitable for machining thermal barrier coatings, while laser machining may cause problems such as coating delamination, especially delamination and material spalling at the interface between the ceramic layer and the bond coat, and between the bond coat and the metal substrate material.

[0005] Regarding the problems of the above-mentioned thermal barrier coatings being non-conductive, the back wall being easily damaged during laser processing, interface delamination, and obvious taper at the entrance and exit, etc., this paper proposes a combined laser and electrical discharge machining process to solve the problems that electrical discharge machining cannot machine the film cooling holes with thermal barrier coatings and laser processing is prone to damage the back wall, interface delamination, and taper, etc. The aim is to provide data support and theoretical basis for the subsequent composite machining technology of the film cooling holes coated with TBC on the blades, which has important scientific significance and application value. Summary of the Invention

[0006] To solve the problems that electrical discharge machining cannot machine the film cooling holes with thermal barrier coatings and laser processing is prone to damage the back wall, interface delamination, and taper, etc., the present invention provides a method for forming film cooling holes of a double-walled turbine blade with a thermal barrier coating, including the following steps:

[0007] Obtain the first distance between the outer wall and the inner wall of the turbine blade;

[0008] According to the first distance being less than or equal to the preset distance between the outer wall and the inner wall of the turbine blade, perform the following steps:

[0009] According to the first distance, the first thickness of the outer wall, the first depth of the preset film cooling hole, and the first laser energy of the laser beam, obtain the second depth of the first film cooling hole machined by the laser beam on the outer wall, and the second depth is less than the first depth;

[0010] According to the first distance, the first thickness, the first depth, and the second depth, obtain the first stroke of the electrode when machining along the first film cooling hole on the outer wall until the electrode perforates the outer wall to obtain the second film cooling hole, wherein there is a second distance between the electrode and the inner wall, and 0 < second distance ≤ first distance;

[0011] According to the electrode perforating the outer wall, and the sum of the second depth and the third depth of the second film cooling hole being consistent with the first depth, obtain the target film cooling hole.

[0012] Preferably, 0.6mm < second distance ≤ first distance.

[0013] According to an embodiment of the present invention, the outer wall includes a thermal barrier coating section and a metal matrix section, the thermal barrier coating section includes a ceramic layer and a bonding layer, the ceramic layer is a non-conductive layer, and the bonding layer and the metal matrix section are conductive layers;

[0014] Obtain a second depth at which the laser beam processes the first air film hole in the non-conductive layer according to the first spacing, the first thickness of the outer wall, the second thickness of the non-conductive layer, the first depth of the preset air film hole, and the first laser energy of the laser beam, where the second depth < the first depth, and the second thickness of the non-conductive layer ≤ the second depth of the first air film hole ≤ the sum of the second thickness of the non-conductive layer and the third thickness of the conductive layer.

[0015] According to an embodiment of the present invention, the method for the laser beam to process the first air film hole in the non-conductive layer includes the following steps:

[0016] The laser beam moves around the first central axis of the preset air film hole along the first axis of the preset air film hole. The laser beam approaches the first outer diameter of the preset air film hole through circular movement from the first axis until the movement trajectory of the laser beam coincides with the first outer diameter. The laser beam processes the first air film hole in the non-conductive layer;

[0017] Alternatively, the laser beam moves around the first central axis of the preset air film hole along the first outer diameter of the preset air film hole. The laser beam approaches the first central axis through circular movement from the first outer diameter until the laser beam is located on the first axis of the preset air film hole. The laser beam processes the first air film hole in the non-conductive layer;

[0018] Alternatively, the laser beam moves around the first central axis of the preset air film hole along the first axis of the preset air film hole. The laser beam approaches the first outer diameter of the preset air film hole through circular movement from the first axis until the movement trajectory of the laser beam coincides with the second outer diameter of the preset air film hole. Then the laser beam moves around the first central axis of the preset air film hole along the first outer diameter of the preset air film hole. The laser beam approaches the first central axis through circular movement from the first outer diameter until the movement trajectory of the laser beam coincides with the second outer diameter. The laser beam processes the first air film hole in the non-conductive layer, where the second outer diameter < the first outer diameter.

[0019] According to an embodiment of the present invention, the outer wall includes a thermal barrier coating section and a metal matrix section. The thermal barrier coating section includes a ceramic layer and a bonding layer. The ceramic layer is a non-conductive layer, and the bonding layer and the metal matrix section are conductive layers;

[0020] The method for the laser beam to process the outer wall includes the following steps:

[0021] Obtain the first aperture of the preset air film hole;

[0022] The laser beam processes the first air film hole in the non-conductive layer. The second aperture of the first air film hole is within the first aperture range. The first air film hole has a fourth depth, and at least a part of the bottom of the first air film hole is located in the bonding layer;

[0023] The laser beam processes the third aperture and the fifth depth of the second air film hole in the conductive layer along the first air film hole. Among them, the third aperture < the second aperture, and the fifth depth < the third depth;

[0024] The electrode processes the fourth aperture and the sixth depth of the second air film hole in the conductive layer along the second air film hole processed by the laser beam. Among them, the fourth aperture > the third aperture, the sixth depth > the fifth depth, or the sixth depth < the fifth depth;

[0025] According to the perforation of the electrode in the conductive layer and the fourth aperture being within the first aperture range, and the sum of the fourth depth, the fifth depth, and the sixth depth being consistent with the first depth, the target air film hole is obtained.

[0026] According to an embodiment of the present invention, the electrode with a third outer diameter is obtained according to the first aperture of the preset air film hole. The electrode has a hollow cooling water channel;

[0027] The third aperture of the second air film hole is obtained according to the second diameter of the cooling water channel in the electrode;

[0028] Among them, the second diameter < the third outer diameter ≤ the third aperture < the first aperture.

[0029] According to an embodiment of the present invention, when the bottom of the first air film hole is close to the conductive layer, the first laser energy drops to the second laser energy.

[0030] According to an embodiment of the present invention, the electrode processes the outer wall along the second air film hole, including at least three electrode processing stages;

[0031] The three electrode processing stages include an electrode initial processing stage, an electrode intermediate processing stage, and an electrode perforation stage that are carried out in sequence;

[0032] When in the electrode initial processing stage, the electrode has a first discharge gap;

[0033] When in the electrode intermediate processing stage, the electrode has a second discharge gap;

[0034] When in the electrode perforation stage, the electrode has a third discharge gap;

[0035] Among them, the first discharge gap > the second discharge gap, the third discharge gap > the second discharge gap, and the first discharge gap ≥ the third discharge gap.

[0036] Preferably, the first discharge gap > the third discharge gap.

[0037] According to an embodiment of the present invention, the preset distance between the outer wall and the inner wall of the turbine blade is: 0 < preset distance ≤ 0.8 mm.

[0038] Preferably, 0.6 ≤ preset distance ≤ 0.8 mm.

[0039] According to an embodiment of the present invention, the first aperture of the preset film hole is 0.3 - 3.0 mm, and the difference between the target film aperture of the target film hole and the first aperture of the preset film hole is ±0.05 mm.

[0040] According to an embodiment of the present invention, the laser includes an ultrafast laser or a short - pulse laser or a long - pulse laser;

[0041] The ultrafast laser includes a picosecond laser or a femtosecond laser; the short - pulse laser includes a nanosecond laser; the long - pulse laser includes a millisecond laser.

[0042] According to an embodiment of the present invention, the laser processing parameters during picosecond laser processing include a single - pulse energy of 30 - 50 μJ, a scanning speed of 250 - 450 mm / s, and a repetition frequency of 84 - 500 kHz.

[0043] Preferably, the single - pulse energy is 40 μJ, the scanning speed is 300 mm / s, and the repetition frequency is 500 kHz.

[0044] According to an embodiment of the present invention, the electrode includes tubular brass, and the electrode processing parameters during brass processing include a peak current of 1 - 2.35 A and a pulse width of 5 - 12 μs.

[0045] Preferably, the peak current is 2.03 A, the pulse width is 5 μs, the pulse time is 25 μs, and the pulse peak voltage is 80 V.

[0046] The present invention has the following beneficial effects:

[0047] 1. The present invention processes the film cooling holes of a double-wall turbine blade with a thermal barrier coating through the combined processing of laser and electrode. First, the laser is used to process the non-conductive ceramic layer, and then the electrode is used to process the conductive layer, avoiding the problems of laser damaging the wall surface of the double-wall turbine blade after the laser penetrates the metal matrix when only using laser processing, as well as the phenomena of splitting of the hole wall and interface delamination easily caused by laser processing. By the method of the present invention, there is no need to additionally use a filling adhesive to fill the gap between the inner wall and the outer wall in order to avoid damaging the double-wall turbine blade when processing the film cooling holes.

[0048] 2. By the method of the present invention, holes are drilled in a metal matrix with a ceramic coating on its surface. According to the surface morphology of the ceramic layer, the longitudinal section schematic diagram of the hole wall, and the results of the remelting layer thickness of the hole wall of the metal matrix obtained by the method of the present invention, it shows the feasibility of the combined processing of picosecond laser and electric discharge machining of metal matrix ceramic coating materials, solves the problems that the electrode cannot process the film cooling holes with a thermal barrier coating and laser processing is prone to cause interface delamination and taper, etc., provides data support and theoretical basis for the subsequent combined processing technology of the film cooling holes of the double-wall turbine blade, and has important scientific significance and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 The flowchart of a method for forming film cooling holes of a double-wall turbine blade with a thermal barrier coating according to the present invention is shown;

[0050] Figure 2 The partial structural schematic diagram of a double-wall turbine blade with a thermal barrier coating is shown;

[0051] Figure 3 The metallographic microscope images of the surface morphology of the ceramic layer after laser beam and electrode processing in Examples 1-4 are shown, where (a), (b), (c), and (d) are the changes in the surface morphology of the hole before and after electric discharge machining under different single-pulse energies, scanning speeds, repetition frequencies, and processing times in sequence;

[0052] Figure 4 The metallographic microscope image of the blade obtained in Example 5 is shown, where (a) is the surface morphology of the hole, (b) is the longitudinal section of the hole wall, (c) is the remelting layer thickness of the left hole wall of the matrix, and (d) is the remelting layer thickness of the right hole wall of the matrix;

[0053] Figure 5 The metallographic microscope image of the blade obtained in Example 6 is shown, where (a) is the surface morphology of the hole, (b) is the longitudinal section of the hole wall, (c) is the remelting layer thickness of the left hole wall of the matrix, and (d) is the remelting layer thickness of the right hole wall of the matrix. DETAILED DESCRIPTION OF THE INVENTION

[0054] The present disclosure will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are described only to enable those of ordinary skill in the art to better understand and thus implement the present disclosure, rather than to imply any limitation on the scope of the present disclosure.

[0055] As used herein, the term "comprising" and its variants are to be construed as open-ended terms meaning "including but not limited to". The term "based on" is to be construed as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be construed as "at least one embodiment". The term "another embodiment" is to be construed as "at least one other embodiment". The terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not used to limit that the indicated device, element or component must have a specific orientation, or be constructed and operated in a specific orientation. And, in addition to being able to represent the orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the present application can be understood according to specific circumstances. In addition, the terms "mounted", "arranged", "provided with", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral structure; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, or there may be an internal connection between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances. In addition, the terms "first", "second", etc. are mainly used to distinguish different devices, elements or components (the specific types and structures may be the same or different), and are not used to indicate or imply the relative importance and quantity of the indicated device, element or component. Unless otherwise specified, the meaning of "a plurality" is two or more.

[0056] This embodiment discloses a method for forming air film holes on a double-wall turbine blade with a thermal barrier coating, as Figure 2 shown, which may include:

[0057] Obtaining a first distance between the outer wall and the inner wall of the turbine blade;

[0058] Performing the following steps according to the first distance being less than or equal to a preset distance between the outer wall and the inner wall of the turbine blade:

[0059] Obtain a second depth of the first film hole machined by the laser beam on the outer wall according to the first spacing, the first thickness of the outer wall, the first depth of the preset film hole, and the first laser energy of the laser beam, where the second depth is less than the first depth;

[0060] Obtain a first stroke of the electrode when the electrode is machined along the first film hole on the outer wall until the electrode perforates the outer wall to obtain a second film hole according to the first spacing, the first thickness, the first depth, and the second depth, where a second spacing exists between the electrode and the inner wall, and 0 < second spacing ≤ first spacing;

[0061] Obtain a target film hole according to the electrode perforating the outer wall and the sum of the second depth and the third depth of the second film hole being consistent with the first depth.

[0062] In this embodiment, the turbine blade is a turbine blade with a double wall, as Figure 2 shown. The inner wall is closer to the middle of the turbine blade, and the outer wall is farther from the middle of the turbine blade. Measure the first spacing between the outer wall and the inner wall. When the first spacing is less than or equal to the preset spacing, measure the first thickness of the outer wall, obtain the first depth of the preset film hole, obtain the first laser energy of the laser beam, and judge the first depth of the first film hole machined by the laser beam on the outer wall according to the first spacing, the first thickness of the outer wall, the first depth of the preset film hole, and the first laser energy of the laser beam, that is, judge the depth of ablating the outer wall with the laser beam, ensure that the film hole can be machined faster with the laser beam, and at the same time avoid the problem of delamination on the film hole wall caused by long-term use of the laser beam when machining the film hole on the outer wall, and the problem that the laser beam energy is likely to damage the comparison wall after the laser beam perforates. The comparison wall is one wall surface of the inner wall surface corresponding to the outer wall.

[0063] According to the second depth at which the first film cooling hole has been machined on the outer wall by the laser beam, the stroke required for the electrode to machine the second film cooling hole after the electrode extends into the first film cooling hole can be determined. In order to avoid the situation that after the electrode perforates the hole, every time a part is ablated by the electric discharge, the electrode adaptively continues to extend, ensuring that the electrode effectively ablates the part to be machined. As a result, the electrode remains in a moving state while performing electric discharge machining to drill the hole. When the electrode is about to perforate the hole, since the electrode is machined during the moving process, the inertia generated by the movement of the electrode may cause the electrode to continue to move after perforating the hole, resulting in the electrode contacting the inner wall and damaging the inner wall of the turbine blade. Therefore, according to the first distance, the first thickness, the first depth, and the second depth, the first stroke generated by the electrode from the bottom of the first film cooling hole to after perforating the hole is determined, so that one end of the electrode is located in the gap between the outer wall and the inner wall, and there is a second distance between the electrode and the inner wall, that is, the electrode does not contact the inner wall, ensuring that there is a gap between the electrode and the inner wall. By obtaining the first stroke of the electrode, it is convenient to determine the maximum movable stroke of the electrode when the electrode drills the outer wall, thereby avoiding the situation that the moving stroke of the electrode is too large, resulting in the electrode contacting the inner wall and damaging the inner wall.

[0064] And according to the sum of the perforation of the electrode on the outer wall, the second depth, and the third depth of the second film cooling hole being consistent with the first depth, the target film cooling hole is obtained, ensuring that the machined film cooling hole is the target film cooling hole, that is, it is necessary to ensure that the direction of the laser beam or the electrode machining on the outer wall is consistent with the extending direction of the target film cooling hole. Here, perforation means that the electrode drills the outer side wall until the electrode extends into the gap between the outer wall and the inner wall, that is, the state where the electrode extends into the gap between the outer wall and the inner wall or the state where the second film cooling hole is in communication with the gap between the outer wall and the inner wall is the perforation of the electrode. By the method of first using the laser beam for machining and then using electric discharge machining in cooperation in this embodiment, problems such as the electric discharge machining being unable to machine the film cooling hole with a thermal barrier coating and the laser machining being prone to damaging the walls, interface delamination, and taper of the double-wall turbine blade can be solved. It is also not necessary to use additional filling glue to fill the gap between the inner wall and the outer wall in order to avoid the film cooling hole being prone to damaging the double-wall turbine blade.

[0065] Preferably, 0.6 mm < the second distance ≤ the first distance.

[0066] According to an embodiment of the present invention, the outer wall includes a thermal barrier coating section and a metal matrix section. The thermal barrier coating section includes a ceramic layer and a bonding layer. The ceramic layer is a non-conductive layer, and the bonding layer and the metal matrix section are conductive layers;

[0067] Obtain a second depth at which the laser beam processes a first film hole in the non-conductive layer according to the first spacing, the first thickness of the outer wall, the second thickness of the non-conductive layer, the first depth of the preset film hole, and the first laser energy of the laser beam, where the second depth < the first depth, and the second thickness of the non-conductive layer ≤ the second depth of the first film hole ≤ the sum of the second thickness of the non-conductive layer and the third thickness of the conductive layer.

[0068] In this embodiment, the outer wall is composed of a thermal barrier coating section and a metal matrix layer section. The thermal barrier coating section is composed of a ceramic layer and a bonding layer. The bonding layer is made of metal. The ceramic layer is bonded to the metal matrix layer section through the metal bonding layer. Since the ceramic layer is non-conductive and the bonding layer and the metal matrix layer section are conductive, this embodiment proposes to use laser to process the non-conductive part and electrode to process the conductive part. For the sake of concise description of the processing position and easy understanding, the bonding layer and the metal matrix are referred to as the conductive layer in some descriptions in this article, and the ceramic layer is referred to as the non-conductive layer. By processing the non-conductive layer with a laser beam, the problem that the electrode cannot process the ceramic layer is solved. Further, by setting the depth of laser processing of the non-conductive layer, that is, setting the second depth at which the laser beam processes the first film hole, the second thickness of the non-conductive layer ≤ the second depth of the first film hole ≤ the sum of the second thickness of the non-conductive layer and the third thickness of the conductive layer, it is ensured that the film hole located in the non-conductive layer is processed by the laser beam, so when using the electrode for processing, it is ensured that the electrode only processes the conductive layer. Since the laser is likely to cause delamination of the thermal barrier coating, that is, delamination between the ceramic layer and the bonding layer, delamination between the bonding layer and the metal matrix layer, and problems such as taper, only the first film hole is processed by laser in the ceramic layer to reduce the adverse effects brought by laser processing for hole making.

[0069] In some embodiments, the first film hole is processed by ablating the non-conductive layer at a high temperature of the laser until the position where the laser beam spot is located shows the conductive layer, and the aperture of the first film hole is within the aperture range of the preset film hole. At this time, the operation of the laser beam processing can be stopped. Insert the electrode into the first film hole. When the electrode and the above-mentioned conductive layer are within the preset discharge gap range, pass current into the electrode. The electrode discharges to generate an electric spark with the conductive layer, and the conductive layer is ablated by the electric spark to realize electric discharge machining for hole making.

[0070] In some embodiments, 0.05 mm ≤ the preset discharge gap ≤ 0.03 mm.

[0071] In some embodiments, the thickness of the metal matrix layer section is 1 - 2 mm, the thickness of the bonding layer is 0.015 - 0.06 mm, and the thickness of the ceramic layer is 0.03 - 0.15 mm.

[0072] According to an embodiment of the present invention, the method for the laser beam to process a first film hole in the non-conductive layer includes the following steps:

[0073] The laser beam revolves around the first central axis of the preset air film hole along the first axis of the preset air film hole. The laser beam moves annularly from the first axis towards the first outer diameter of the preset air film hole until the movement trajectory of the laser beam coincides with the first outer diameter. The laser beam processes the first air film hole on the non-conductive layer.

[0074] Alternatively, the laser beam revolves around the first central axis of the preset air film hole along the first outer diameter of the preset air film hole. The laser beam moves annularly from the first outer diameter towards the first central axis until the laser beam is located at the first axis of the preset air film hole. The laser beam processes the first air film hole on the non-conductive layer.

[0075] Alternatively, the laser beam revolves around the first central axis of the preset air film hole along the first axis of the preset air film hole. The laser beam moves annularly from the first axis towards the first outer diameter of the preset air film hole until the movement trajectory of the laser beam coincides with the second outer diameter of the preset air film hole. Then, the laser beam revolves around the first central axis of the preset air film hole along the first outer diameter of the preset air film hole. The laser beam moves annularly from the first outer diameter towards the first central axis until the movement trajectory of the laser beam coincides with the second outer diameter. The laser beam processes the first air film hole on the non-conductive layer, where the second outer diameter < the first outer diameter.

[0076] In this embodiment, three processing methods are provided for processing by the laser beam on the non-conductive layer. The first processing method is that the laser beam processes the first air film hole on the non-conductive layer by means of circumferential cutting from the hole axis to the hole outer diameter.

[0077] The second processing method is that the laser beam processes the first air film hole by means of circumferential cutting from the hole outer diameter to the hole axis. Since, during the process of the laser beam processing the air film hole, a phenomenon occurs where the temperature generated by the laser beam accumulates in the already processed hole, the accumulated heat affects the hole wall, such as causing interface delamination. To reduce this influence, by processing from the hole outer diameter to the hole axis, the heat accumulates towards the hole axis direction, reducing the heat at the hole outer diameter, that is, reducing the heat accumulation on the hole wall. At the same time, processing the hole outer diameter first allows the heat flow to have a larger flow space, thereby reducing the problem of the temperature affecting the interface delamination of the hole wall.

[0078] The third processing method is a combination of the first processing method and the second processing method. Specifically, first, a first air film hole with a partial first hole diameter and a partial second depth is machined from the hole axis to the second outer diameter of the hole, and then all the first air film holes are machined from the first outer diameter to the second outer diameter of the hole. By machining the first air film hole with a partial first hole diameter and a partial second depth first, the machining area for subsequently machining all the first air film holes from the first outer diameter to the second outer diameter is reduced, the heat continuously generated by the laser beam on the hole wall is reduced, and thus the problem of the temperature affecting the interface delamination of the hole wall is reduced.

[0079] According to an embodiment of the present invention, the outer wall includes a thermal barrier coating section and a metal matrix section. The thermal barrier coating section includes a ceramic layer and a bonding layer. The ceramic layer is a non-conductive layer, and the bonding layer and the metal matrix section are conductive layers;

[0080] The method for machining the laser beam on the outer wall includes the following steps:

[0081] Obtain the first hole diameter of the preset air film hole;

[0082] The laser beam is machined on the non-conductive layer to obtain the first air film hole. The second hole diameter of the first air film hole is within the range of the first hole diameter. The first air film hole has a fourth depth, and at least a part of the bottom of the first air film hole is located in the bonding layer;

[0083] The laser beam processes the third hole diameter and the fifth depth of the second air film hole along the first air film hole on the conductive layer, where the third hole diameter < the second hole diameter and the fifth depth < the third depth;

[0084] The electrode processes the fourth hole diameter and the sixth depth of the second air film hole along the second air film hole with the third hole diameter and the fifth depth on the conductive layer, where the fourth hole diameter > the third hole diameter, the sixth depth > the fifth depth, or the sixth depth < the fifth depth;

[0085] According to the perforation of the electrode on the conductive layer, the fourth hole diameter is within the range of the first hole diameter, and the sum of the fourth depth, the fifth depth, and the sixth depth is consistent with the first depth, the target air film hole is obtained.

[0086] In this embodiment, the sixth depth is the depth obtained by further processing on the basis of the fifth depth. The sum of the fifth depth and the sixth depth is equal to the third depth of the second gas film hole. By ensuring that at least a part of the bottom of the first gas film hole is located in the bonding layer, it is ensured that the laser beam completely processes all the gas film holes in the non-conductive layer part, ensuring that the electrode only processes the gas film holes in the conductive layer and avoiding ineffective processing. The fourth depth and the second depth in this embodiment can be understood as the same depth, that is, the fourth depth and the second depth are the same. For the convenience of distinguishing the processing in different situations, the fourth depth is used here. By means of the laser beam processing the third aperture and the fifth depth of the second gas film hole in the conductive layer along the first gas film hole, the laser beam first processes out part of the second gas film holes with the third aperture and the fifth depth, and then the electrode is used to continue processing the second gas film holes with the fourth aperture and the sixth depth. This processing method not only improves the processing efficiency on the premise of ensuring that the laser beam reduces the interface delamination of the hole wall, but also enables the part of the second gas film holes processed by the laser beam in the conductive layer to form a cooling water tank that can accommodate part of the cooling water generated during the processing of the electrode. The cooling water tank can be used to temporarily accommodate the cooling water, so that part of the heat generated by the cooling water cooling the electrode can be released in the cooling water tank, reducing the temperature of the cooling water, and thus reducing the damage to the surface of the thermal barrier coating caused by the heat of the cooling water discharged from the gas film hole inlet.

[0087] Preferably, the sixth depth < the fifth depth, so that the laser can process more deeply the gas film holes in the conductive layer.

[0088] In some embodiments, 0 mm < the sixth depth ≤ 0.5 mm, so as to ensure that more parts of the gas film holes can be processed by the laser beam in the conductive layer, further improving the working efficiency.

[0089] According to an embodiment of the present invention, the electrode with the third outer diameter is obtained according to the first aperture of the preset gas film hole, and the electrode has a hollow cooling water channel;

[0090] The third aperture of the second gas film hole is obtained according to the second diameter of the cooling water channel in the electrode;

[0091] Wherein, the second diameter < the third outer diameter ≤ the third aperture < the first aperture.

[0092] In this embodiment, by means of obtaining the third aperture of the second gas film hole according to the second diameter of the cooling water channel in the electrode, it is ensured that part of the heat of the ablated metal material can still be released in the cooling water tank, and the pollution of the surface of the ceramic layer by the ablated matrix material can also be avoided.

[0093] Preferably, the ratio of the third outer diameter to the first aperture diameter is 1 to 1.2:1.5. By setting the ratio of the diameter of the electrode to the preset air film aperture diameter, the smooth machining of the electrode towards the conductive layer is ensured.

[0094] According to an embodiment of the present invention, when the bottom of the first air film hole approaches the conductive layer, the first laser energy drops to the second laser energy.

[0095] In this embodiment, when the bottom of the first air film hole machined by the laser in the non-conductive layer approaches the conductive layer, the laser energy of the laser beam is reduced, further reducing the damage caused by the laser beam machining to the double-wall turbine blade during machining and drilling.

[0096] In some embodiments, when the aperture of the laser beam machining reaches the range close to the preset air film aperture, the laser energy of the laser beam is reduced, thereby further reducing the damage caused by the laser beam machining to the double-wall turbine blade during machining and drilling.

[0097] According to an embodiment of the present invention, the electrode machining along the second air film hole on the outer wall includes at least three electrode machining stages;

[0098] The three electrode machining stages include an electrode initial machining stage, an electrode intermediate machining stage, and an electrode perforation stage that are carried out in sequence;

[0099] When in the electrode initial machining stage, the electrode has a first discharge gap;

[0100] When in the electrode intermediate machining stage, the electrode has a second discharge gap;

[0101] When in the electrode perforation stage, the electrode has a third discharge gap;

[0102] Wherein, the first discharge gap > the second discharge gap, the third discharge gap > the second discharge gap, and the first discharge gap ≥ the third discharge gap.

[0103] In this embodiment, the primary electrode processing stage is the stage when the electrode starts to process on the conductive layer. The intermediate electrode processing stage is the stage when the electrode processes the conductive layer without perforation. The electrode perforation stage is the stage when the electrode penetrates the air film hole. During the initial processing of the second air film hole, the surfaces of the electrode and the workpiece are usually relatively rough. A larger gap can ensure that even if there are some protrusions or unevenness on the surface, the electrode and the workpiece will not come into direct contact, avoiding damage to the electrode or short-circuit phenomenon. However, the larger discharge gap makes the energy distribution not concentrated, and the flow of the working fluid is weak in the initial stage, resulting in a lower cooling efficiency. As a result, the melted material fails to be washed away in time and accumulates on the workpiece surface, forming a relatively thick remelting layer, which reduces the quality of the air film hole and the diameter of the air film hole fails to meet the requirements. Therefore, when processing the conductive layer, the discharge gap of the electrode at the start of processing is larger than that in the intermediate processing stage, so that the conductivity of the middle part of the conductive layer is stronger than that near the non-conductive layer. By means of the three electrode processing stages, the integrity of the air film hole is ensured.

[0104] Preferably, the first discharge gap > the third discharge gap.

[0105] In some embodiments, the primary electrode processing stage is the stage when the electrode processes on the adhesive layer. The intermediate electrode processing stage is the stage when the electrode processes the metal matrix layer without perforation. The electrode perforation stage is the stage when the electrode penetrates the air film hole. The discharge gap of the adhesive layer is larger than that of the metal matrix layer, so that the conductivity of the metal matrix layer is stronger than that of the adhesive layer.

[0106] In some embodiments, when only processing a metal matrix of the same material, that is, when using an electrode to process the metal matrix layer, the relationship of the discharge gaps of the electrode is: the initial stage > the perforation stage > the intermediate stage. To avoid direct contact caused by unevenness on the surfaces of the electrode and the workpiece, resulting in damage to the electrode or short-circuit phenomenon, the discharge gap in the initial stage is larger; the current density increases in the perforation stage, the discharge energy is concentrated, and the workpiece is effectively penetrated. The discharge process in the intermediate stage is stable and efficient, the energy is concentrated, the material removal is uniform and continuous, so the discharge gap is the smallest.

[0107] In some embodiments, 0.05 mm ≤ the first discharge gap, the second discharge gap, and the third discharge gap ≤ 0.3 mm.

[0108] According to an embodiment of the present invention, the preset distance between the outer wall and the inner wall of the turbine blade is: 0 mm < the preset distance ≤ 0.8 mm.

[0109] In this embodiment, a preset distance range between the outer wall and the inner wall of the turbine blade is provided.

[0110] Preferably, 0.6 mm ≤ the preset distance ≤ 0.8 mm.

[0111] According to an embodiment of the present invention, the first aperture diameter of the preset air film hole is 0.3 - 3.0 mm, and the difference between the target film aperture diameter of the target air film hole and the first aperture diameter of the preset air film hole is ±0.05 mm.

[0112] In this embodiment, by setting the preset film aperture diameter and the preset remelting layer thickness, it is convenient to carry out the processing work of the air film hole while ensuring the quality of the target air film hole.

[0113] According to an embodiment of the present invention, the laser includes an ultrafast laser or a short-pulse laser or a long-pulse laser;

[0114] The ultrafast laser includes a picosecond laser or a femtosecond laser; the short-pulse laser includes a nanosecond laser; the long-pulse laser includes a millisecond laser.

[0115] In this embodiment, some selectable laser examples are provided.

[0116] In some embodiments, the electrode is a tubular copper electrode wire with a diameter of φ1.4 mm, and the preset air film aperture diameter is φ1.5 mm.

[0117] In some embodiments, when using the picosecond laser, the processing method of the picosecond laser is circumferential cutting and punching, the scanning path of the picosecond laser does not exceed 1.5 mm, and the interval between the concentric circles processed by the picosecond laser does not exceed 0.01 mm.

[0118] According to an embodiment of the present invention, the laser processing parameters during the picosecond laser processing include a single-pulse energy of 30 - 50 μJ, a scanning speed of 250 - 450 mm / s, and a repetition frequency of 84 - 500 kHz.

[0119] In this embodiment, by setting reasonable laser processing parameters, the processing quality of the air film hole is ensured.

[0120] Preferably, the single-pulse energy is 40 μJ, the scanning speed is 300 mm / s, and the repetition frequency is 500 kHz.

[0121] In some embodiments, the number of laser processing times is obtained according to the thickness of the ceramic layer. When the thickness of the ceramic layer is 0.03 - 0.15 mm, the number of processing times is 16 - 20 times. The number of processing times mainly affects the depth of the hole and has a small impact on the entrance aperture diameter. Therefore, the number of processing times usually depends on the thickness of the ceramic layer, and the preferred number of processing times is 16 times.

[0122] According to an embodiment of the present invention, the electrode includes tubular brass, and the electrode processing parameters during the brass processing include a peak current of 1 - 2.35 A and a pulse width of 5 - 12 μs.

[0123] In this embodiment, by setting reasonable electrode processing parameters, the processing quality of the air film holes is further ensured.

[0124] Preferably, the peak current is 2.03 - 2.35 A, the pulse width is 5 - 6 μs, the pulse time is 25 μs, and the pulse peak voltage is 80 V, so that the thickness of the remelting layer generated by the electrode during the processing of the inner wall is ≤ 0.03 mm.

[0125] More preferably, the peak current is 2.03 A and the pulse width is 5 μs.

[0126] Examples 1 - 4

[0127] 1.1 Equipment

[0128] A picosecond fiber laser, with an output wavelength of 1064 nm, a Gaussian beam with a pulse width of 10 - 15 ps, a repetition frequency range of 1 Hz - 1000 kHz, an average output power of 35 W, and a maximum single - pulse energy of 135 μJ.

[0129] An electric discharge machining equipment, with a voltage of 380 V, an XY stroke of 500×400 mm, a tool electrode made of tubular brass, and the workpiece being the anode and the electrode being the cathode during processing.

[0130] A nickel - based superalloy EB - PVD with a thermal barrier coating is used to simulate a gas turbine blade. The test piece is a circular sample with a diameter of about 30 mm. The metal matrix layer uses a nickel - based single - crystal superalloy IC10 with a thickness of about 1 - 2 mm. 8YSZ is used as the ceramic layer with a thickness of about 0.03 - 0.15 mm, and a metal alloy NiCrAlYSi is used as the metal bonding layer with a thickness of about 0.015 - 0.06 mm, and deposition is carried out using the electron beam physical vapor deposition method (EB - PVD).

[0131] 1.2 Forming φ1.5 - mm air film holes on a double - wall turbine blade

[0132] The picosecond laser is used to etch the non - conductive ceramic layer at normal temperature and pressure. The processing method is circumferential cutting and drilling, and the scanning path is set as concentric circles with a maximum diameter of 1.5 mm and an interval of 0.01 mm to obtain the first air film hole. The error range between the diameter of the first air film hole in the example and φ1.5 mm is ±0.05 mm, that is, the diameter range of the first air film hole obtained by processing is φ1.45 - 1.55 mm.

[0133] The electrode extends into the first air film hole to process the conductive layer to obtain the second air film hole. The processing method of filling cold water during the electric discharge machining process of the electrode and the processing principle of the electric discharge machining are prior arts, so they will not be elaborated here.

[0134] The picosecond laser processing parameters of Examples 1 - 4 are shown in Table 1 below, and each example is divided into three groups for processing:

[0135] Table 1 Picosecond laser processing parameters of Examples 1 - 4

[0136]

[0137] The electrical discharge machining parameters of Examples 1 - 4 are shown in Table 2 below:

[0138] Table 2 Electrical discharge machining parameters of Examples 1 - 4

[0139]

[0140] The air film holes of Examples 1 - 4 before and after electrical discharge machining are as Figure 3 shown. The initial state is the surface morphology of the ceramic layer after picosecond laser beam machining (i.e., the state before electrical discharge machining), and the final state is the surface morphology of the ceramic layer after perforation by electrical discharge machining. Figure (a) shows Figure 3 the change in the surface morphology of the hole before and after electrical discharge machining at different single pulse energies. Figure (b) shows the change in the surface morphology of the hole before and after electrical discharge machining at different scanning speeds. Figure (c) shows the change in the surface morphology of the hole before and after electrical discharge machining at different repetition frequencies. Figure (d) shows the change in the surface morphology of the hole before and after electrical discharge machining at different machining times. There is no heat affected zone and ablation phenomenon on the surface of the ceramic layer after picosecond laser beam machining. After electrical discharge machining, the surface integrity of the ceramic layers of Example 1c, Example 2c, and Example 3c, with pore diameters of 1.486 mm, 1.499 mm, and 1.488 mm respectively, meets the error range (±0.05 mm). For the remaining Examples 1 (a, b), Example 2 (a, b), and Example 3 (a, b), the electrical discharge machining has a certain degree of impact on the surface integrity of the ceramic layer. Therefore, it is crucial to reduce the damage to the surface of the ceramic layer during electrical discharge machining. Excessive or too small electrical discharge energy will both lead to an increase in the thickness of the remelting layer and a decrease in machining accuracy. Moreover, if the erosion products are not discharged in time and adhere to the surface, it will affect the surface morphology of the hole and the integrity of the hole opening.

[0141] The thickness of the remelting layer on the pore wall of the air film holes obtained by processing Examples 1 - 4 is shown in Table 3.

[0142] Table 3 Thickness of the remelting layer on the pore wall of the air film holes obtained by processing Examples 1 - 4

[0143]

[0144] The thickness of the remelting layer is one of the important technical indicators to measure the machining quality of the air film hole. If it does not meet the machining requirements, it is extremely easy to break and directly shorten the fatigue life of the material. As can be seen from Table 3, the maximum thickness of the remelting layer is 0.06 mm, and the minimum thickness is 0 mm.

[0145] Examples 5 - 6

[0146] Examples 5 - 6 are different from Example 1c in that the electrical discharge machining parameters are different. The electrical discharge machining parameters of Examples 5 - 6 are shown in Table 4.

[0147] Table 4 Electrical Discharge Machining Parameters of Examples 5 - 6

[0148]

[0149] In Example 5, a gas turbine blade is formed with film holes as Figure 4 shown. Observed under a metallurgical microscope, Fig. (a) shows the surface morphology of the entrance hole of the film hole after electrical discharge machining. The average entrance diameter of the erosion hole in the ceramic layer measured by the metallurgical microscope is 1.483 mm. It can be seen from the figure that the erosion hole is less affected by electrical discharge machining and the hole shape is complete. Fig. (b) is a schematic diagram of the bonding layer on the hole wall under the electrical discharge conditions of Example 5. There are no obvious microcracks generated on the side wall of the ceramic layer machined by the picosecond laser beam, and there is no obvious attachment of erosion products on the inner wall of the hole. Moreover, no obvious interface delamination is found between the ceramic layer and the bonding layer, the bonding layer has good compactness, and there are no phenomena such as coating peeling and melting erosion. There are almost no microcracks and no obvious delamination between the ceramic layer and the bonding layer and between the bonding layer and the metal matrix layer. Figs. (c) and (d) show the remelting layer thickness at the initial stage of the metal matrix layer during electrical discharge machining. The average remelting layer thickness on the left side is 0.026 mm, and on the right side is 0.03 mm, indicating that the remelting layer thickness of the film hole obtained by the method of this example is small and the machining quality of the film hole is good.

[0150] In Example 6, a gas turbine blade is formed with film holes as Figure 5 shown. Observed under a metallurgical microscope, Fig. (a) shows the surface morphology of the entrance hole of the film hole after electrical discharge machining. The average entrance diameter of the erosion hole in the ceramic layer measured by the metallurgical microscope is 1.534 mm. After electrical discharge machining, there are ablation traces on the surface of the ceramic layer, which may be the accumulation area of the mixed product after the oxidation of the ceramic layer and the metal matrix. The peak current (2.35 A) and pulse width (6 μs) in Example 6 are both larger than those in Example 5 (peak current 2.03 A, pulse width 5 μs), and the larger discharge energy causes ablation. Fig. (b) is a schematic diagram of the bonding layer on the hole wall under this test condition. There are almost no microcracks generated on the surface of the ceramic layer, and no obvious delamination is found between the thermal barrier coating and the metal matrix. Figs. (c) and (d) show the remelting layer thickness at the entrance of the metal matrix during electrical discharge machining. The average remelting layer thickness on the left side is 0.02 mm, and on the right side is 0.011 mm. The remelting layer is thin. Except for the slight defect of ablation traces on the surface of the ceramic layer in Example 6, it still has good machining effects in terms of interface delamination and remelting layer.

[0151] By comparing the surface morphologies of the thermal barrier coatings processed by Examples 1-4, Example 5 and Example 6, it can be seen that inappropriate electrical discharge machining parameters result in excessive discharge energy, serious ablation damage, and the failure to timely eject the erosion products, which ultimately adhere to the hole surface and affect the hole surface morphology.

[0152] For the hole-making of a metal matrix with a ceramic coating on the surface, the present invention provides a composite machining of picosecond laser and electrical discharge machining. First, the ceramic layer is machined by a picosecond laser beam, and after its metal bonding layer is exposed, the conductive layer is machined by electrical discharge machining. The feasibility of the composite machining of a metal matrix ceramic coating material by picosecond laser and electrical discharge machining is demonstrated through the surface morphology of the ceramic layer, the longitudinal sectional view of the hole wall, and the thickness of the remelting layer on the hole wall of the metal matrix. This solves the problems that electrical discharge machining cannot machine the film holes with thermal barrier coatings, and laser machining is prone to damage the back wall, interface delamination, and taper. It provides data support and a theoretical basis for the subsequent composite machining process of the film holes of double-layer wall turbine blades, and has important scientific significance and application value.

[0153] Those of ordinary skill in the art can understand that the above embodiments are specific cases for implementing the present disclosure, and in actual applications, various changes can be made in form and details without departing from the scope of the present disclosure.

Claims

1. A method for forming film cooling holes on a double-walled turbine blade with a thermal barrier coating, characterized in that, It includes the following steps: Obtain a first spacing between the outer wall and the inner wall of the turbine blade; Perform the following steps according to the first spacing being less than or equal to a preset spacing between the outer wall and the inner wall of the turbine blade: According to the first spacing, a first thickness of the outer wall, a first depth of a preset film cooling hole, and a first laser energy of a laser beam, obtain a second depth of the laser beam for machining the first film cooling hole on the outer wall, where the second depth is less than the first depth; According to the first spacing, the first thickness, the first depth, and the second depth, obtain a first stroke of the electrode when machining along the first film cooling hole on the outer wall until the electrode perforates the outer wall to obtain a second film cooling hole, where there is a second spacing between the electrode and the inner wall, and 0 < second spacing ≤ first spacing; Obtain a target film cooling hole according to the electrode perforating the outer wall and the sum of the second depth and a third depth of the second film cooling hole being consistent with the first depth.

2. The forming method of the film cooling holes of a double-wall turbine blade with a thermal barrier coating according to claim 1, characterized in that, The outer wall includes a thermal barrier coating section and a metal matrix section. The thermal barrier coating section includes a ceramic layer and a bonding layer. The ceramic layer is a non-conductive layer, and the bonding layer and the metal matrix section are conductive layers; According to the first spacing, a first thickness of the outer wall, a second thickness of the non-conductive layer, a first depth of the preset film cooling hole, and a first laser energy of the laser beam, obtain a second depth of the laser beam for machining the first film cooling hole on the non-conductive layer, where the second depth < first depth, and the second thickness of the non-conductive layer ≤ the second depth of the first film cooling hole ≤ the sum of the second thickness of the non-conductive layer and a third thickness of the conductive layer.

3. A method for forming a film cooling hole of a double-walled turbine blade with a thermal barrier coating according to claim 2, characterized in that The method for the laser beam to machine the first film cooling hole on the non-conductive layer includes the following steps: The laser beam moves around the first central axis of the preset film cooling hole along the first axis of the preset film cooling hole. The laser beam approaches the first outer diameter of the preset film cooling hole through circular movement from the first axis until the movement trajectory of the laser beam coincides with the first outer diameter, and the laser beam machines the first film cooling hole on the non-conductive layer; Or, the laser beam moves around the first central axis of the preset film cooling hole along the first outer diameter of the preset film cooling hole. The laser beam approaches the first axis of the preset film cooling hole through circular movement from the first outer diameter until the laser beam is located at the first axis of the preset film cooling hole, and the laser beam machines the first film cooling hole on the non-conductive layer; Alternatively, the laser beam rotates around the first central axis of the preset film hole along the first axis of the preset film hole. The laser beam moves annularly from the first axis towards the first outer diameter of the preset film hole until the movement trajectory of the laser beam coincides with the second outer diameter of the preset film hole. Then, the laser beam rotates around the first central axis of the preset film hole along the first outer diameter of the preset film hole. The laser beam moves annularly from the first outer diameter towards the first central axis until the movement trajectory of the laser beam coincides with the second outer diameter. The laser beam processes the first film hole in the non-conductive layer, where the second outer diameter < the first outer diameter.

4. A method for forming a film cooling hole of a double-wall turbine blade with a thermal barrier coating according to claim 1, characterized in that The outer wall includes a thermal barrier coating section and a metal matrix section. The thermal barrier coating section includes a ceramic layer and a bonding layer. The ceramic layer is a non-conductive layer, and the bonding layer and the metal matrix section are conductive layers. The method for processing the laser beam on the outer wall includes the following steps: Obtain the first aperture diameter of the preset film hole. The laser beam processes the first film hole in the non-conductive layer. The second aperture diameter of the first film hole is within the range of the first aperture diameter. The first film hole has a fourth depth, and at least part of the bottom of the first film hole is located in the bonding layer. The laser beam processes the third aperture diameter and the fifth depth of the second film hole in the conductive layer along the first film hole, where the third aperture diameter < the second aperture diameter and the fifth depth < the third depth. The electrode processes the fourth aperture diameter and the sixth depth of the second film hole in the conductive layer along the second film hole processed by the laser beam, where the fourth aperture diameter > the third aperture diameter, the sixth depth > the fifth depth, or the sixth depth < the fifth depth. Based on the electrode perforating the conductive layer and the fourth aperture diameter being within the range of the first aperture diameter, and the sum of the fourth depth, the fifth depth, and the sixth depth being consistent with the first depth, the target film hole is obtained.

5. A method for forming a film cooling hole of a double-wall turbine blade with a thermal barrier coating according to claim 4, characterized in that Obtain the electrode with a third outer diameter according to the first aperture diameter of the preset film hole. The electrode has a hollow cooling water channel. Obtain the third aperture diameter of the second film hole according to the second diameter of the cooling water channel in the electrode. Wherein, the second diameter < the third outer diameter ≤ the third aperture diameter < the first aperture diameter.

6. A method for forming a film cooling hole of a double-wall turbine blade with a thermal barrier coating according to claim 4, characterized in that When the bottom of the first film hole approaches the conductive layer, the first laser energy drops to the second laser energy.

7. A method for forming a film cooling hole of a double-wall turbine blade with a thermal barrier coating according to claim 1, characterized in that, The electrode processing the second film hole on the outer wall includes at least three electrode processing stages. The three electrode processing stages include an initial electrode processing stage, an intermediate electrode processing stage, and an electrode perforating stage that are carried out in sequence. When in the initial electrode processing stage, the electrode has a first discharge gap. When in the intermediate electrode processing stage, the electrode has a second discharge gap. When in the electrode perforating stage, the electrode has a third discharge gap. Wherein, the first discharge gap > the second discharge gap, the third discharge gap > the second discharge gap, and the first discharge gap ≥ the third discharge gap.

8. A method for forming a film cooling hole of a double-walled turbine blade with a thermal barrier coating according to claim 1, characterized in that, The preset distance between the outer wall and the inner wall of the turbine blade is: 0 ≤ preset distance ≤ 0.8 mm.

9. A method for forming film cooling holes of a double-wall turbine blade with a thermal barrier coating according to claim 1, characterized in that, The first aperture diameter of the preset film holes is 0.3 - 3.0 mm, and the difference between the target film aperture diameter of the target film holes and the first aperture diameter of the preset film holes is ±0.05 mm.

10. A method for forming a film cooling hole of a double-walled turbine blade with a thermal barrier coating according to claim 1, characterized in that, The laser includes an ultrafast laser, a short-pulse laser, or a long-pulse laser; The ultrafast laser includes a picosecond laser or a femtosecond laser; the short-pulse laser includes a nanosecond laser; the long-pulse laser includes a millisecond laser.

11. A method for forming a film cooling hole of a double-wall turbine blade with a thermal barrier coating according to claim 10, characterized in that, The laser processing parameters during picosecond laser processing include a single-pulse energy of 30 - 50 μJ, a scanning speed of 250 - 450 mm / s, and a repetition frequency of 84 - 500 kHz.

12. A method for forming a film cooling hole of a double-wall turbine blade with a thermal barrier coating according to claim 1, characterized in that, The electrode includes tubular brass, and the electrode processing parameters during brass processing include a peak current of 1 - 2.35 A and a pulse width of 5 - 12 μs.

Images