CN115945465A - Method for removing zirconia thermal barrier coating - Google Patents
Method for removing zirconia thermal barrier coating Download PDFInfo
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- CN115945465A CN115945465A CN202310049130.3A CN202310049130A CN115945465A CN 115945465 A CN115945465 A CN 115945465A CN 202310049130 A CN202310049130 A CN 202310049130A CN 115945465 A CN115945465 A CN 115945465A
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- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
Abstract
The invention provides a method for removing a zirconia thermal barrier coating, which comprises the following steps: s1, YSZ coating surface pretreatment: ultrasonic cleaning to remove surface impurities; s2, laser beam adjustment: making the light beam vertically incident on the surface of the coating material; s3, setting parameters: the power is 40-100W, the laser scanning speed is 20-200mm/s, and the repetition frequency is 20-40kHz; the size of a light spot is controlled to be 10-60 mu m in the cleaning process, and the overlapping rate of the light spot is controlled to be 97.5-99.0%; setting ultrasonic power at 60-80W and repeating frequency at 40-100kHz, and scanning layer by layer for multiple times until the coating is removed. According to the invention, the ultrasonic vibration is utilized to inhibit the particles from splashing in the laser cleaning process, so that the negative influence of the heat influence on the removal effect in the laser cleaning process is weakened, the ultrasonic cleaning and the laser cleaning generate a synergistic effect, and the cleaning efficiency and the cleaning effect are improved.
Description
Technical Field
The invention relates to the technical field of thermal barrier coating materials, in particular to a method for cleaning a zirconia thermal barrier coating with yttria partially stabilized by ultrasonic wave and laser.
Background
The thermal barrier coating is a ceramic material used in the field of aeroengine blades, and mainly comprises yttria-partially stabilized zirconia (hereinafter abbreviated as YSZ), wherein Y 2 O 3 The mass percentage is 6-9%. Since 1970 the turbine blade thermal insulation material is first applied to the field of aero-engines, the turbine blade thermal insulation material still serves as a key material for improving the thermal insulation temperature of aero-engine turbine blades till now, has the advantages of low thermal conductivity, high thermal capacity, good thermal expansion matching with base material alloy materials and the like, still has good thermal stability under the continuous scouring of high-temperature gas jet, and occupies an important position in the field of aero-engines. At present, thermal barrier coatings are listed as key core materials in major propulsion plans in all aviation strong countries in the world, and the thermal barrier coatings have been listed as key materials of major concern in China.
Electron beam-physical vapor deposition is one of the surface treatment techniques for physically depositing a material source on the surface of a substrate under vacuum conditions, and is also a common method for preparing thermal barrier coatings.
The chemical cleaning is to remove target materials by using chemical reagents, and in the field of thermal barrier coatings, a chemical cleaning scheme of thermal barrier coatings which is disclosed and reported at present is an acid cleaning scheme by matching hydrofluoric acid and nitric acid.
The laser cleaning is a new technology for surface cleaning, and the principle is that the surface of an object is acted by a pulse beam, and the physical and chemical changes of melting, vaporization, evaporation, ionization, decomposition and the like of a material in a removed area are caused by using the material performance difference between the removed area and a reserved area, so that the removal effect of the surface material is realized. Laser cleaning is an environmentally friendly, non-contact, accurate and controllable method. In addition to successfully overcoming the shortcomings of mechanical and chemical cleaning, this technology has achieved tremendous success in certain areas. For example, in the protection of antiques, the removal of surface contaminants from plasters, murals, parchment and other cultural heritage has been successfully practiced. In the automobile industry, the laser cleaning can effectively replace chemical solvents containing dichloromethane, chlorofluorocarbon and the like which are harmful to human bodies and the environment. It has been reported that laser cleaning of boeing aircraft skins strengthens the skin surface and inhibits fatigue wear of rivets. If the thermal barrier material is cleaned by laser, the economic benefit can be improved, and the environmental pollution can be reduced. The laser cleaning technology has been successful in cultural relic protection, automobile manufacturing industry and marine microorganism removal of ships at present and brings considerable economic benefits.
Ultrasonic cleaning: the method is a cleaning technology mainly based on cavitation effect in cleaning liquid, and achieves the purpose of cleaning through dispersion, emulsification and stripping.
At present, in the production and preparation process of YSZ, pores existing inside the YSZ exceed a certain degree and can be converted into cracks and further spread on the surface and inside of the YSZ, the yield of production is seriously influenced, and economic waste and material waste are caused. Therefore, unqualified coatings need to be removed by a method so as to be prepared again, and the chemical cleaning method adopted at present has the problems of environmental pollution, incapability of accurately controlling the removal force, low removal efficiency and the like. These problems can result in irreparable loss and damage to the operator and substrate material during removal. Therefore, a new environment-friendly, efficient and accurate removal method is urgently needed to realize the re-preparation of YSZ.
Disclosure of Invention
The invention aims to provide a thermal barrier coating removing method combining infrared pulse laser and ultrasonic vibration, which aims to solve the problems that in the prior art, the environment is polluted, the removing force cannot be accurately controlled, the removing efficiency is low, meanwhile, uncontrollable damage is caused to a base material alloy material, the removing process can bring threat to the environment and personal safety and the like, and particularly solves the problems that the surface coating is left and the cleaning is incomplete due to splashed particles in the laser cleaning process.
In order to achieve the above object, the present invention provides a method for removing a zirconia thermal barrier coating, comprising the steps of:
s1, YSZ coating surface pretreatment: ultrasonic cleaning to remove surface impurities;
s2, laser beam adjustment: making the light beam vertically incident on the surface of the coating material;
s3, setting parameters: the power is 40-100W, the scanning speed is 20-200mm/s, and the repetition frequency is 20-40kHz; the size of a light spot is controlled to be 10-60 mu m in the cleaning process, and the overlapping rate of the light spot is controlled to be 97.5-99.0%; setting ultrasonic power of 60-80W and repetition frequency of 40-100kHz, and scanning layer by layer for multiple times until the coating is removed.
Preferably, the ultrasonic cleaning in step S1 is performed by soaking in absolute ethanol with a purity of 95-99.9%.
Preferably, the ultrasonic cleaning time is 10-15min, and the drying is carried out at 60-70 ℃ until the absolute ethyl alcohol on the surface of the coating is completely volatilized.
Preferably, the solution medium in the ultrasonic cleaning is water.
Preferably, the spot overlap ratio is obtained by the formula η = 1-v/(2 × f × d);
wherein, v: scanning speed, f: repetition frequency, η: spot overlap ratio, D: the spot size.
Preferably, the step S3 of scanning layer by layer for multiple times is to repeat the steps S1 to S3 until the Zr element on the surface is completely removed.
Preferably, the method for removing the zirconia thermal barrier coating comprises the following steps:
s1, keeping the distance between a focusing lens and the surface of a YSZ coating at 160-200mm, and vertically irradiating the laser beam above the surface of the YSZ coating to be cleaned, wherein the thickness of the coating is 100-220 mu m;
s2, setting parameters: the ultrasonic power is 80W, and the repetition frequency is 40kHz; the laser power is 40W, the pulse width is 5 mus, the pulse frequency is 40-100kHZ, and the spot overlapping rate is 97.5-99.0%; the laser scanning speed is 20-100mm/s, and the laser spot size is 10-60 mu m; and (4) scanning layer by layer for multiple times to remove the YSZ coating.
The invention provides equipment for removing a zirconium oxide thermal barrier coating, which comprises a laser, wherein a pulse light beam emitted by the laser sequentially passes through an optical vibrating mirror and an optical focusing lens to be emitted into an ultrasonic vibration generator.
Preferably, the laser is connected to a cooling device and a console.
The invention has the following beneficial effects:
the invention aims at a YSZ thermal barrier coating material (yttria-partially stabilized zirconia) in the field of aeroengines, and mainly aims at a Y component 2 O 3 And ZrO 2 Wherein Y is 2 O 3 6 to 9 percent of cleaning. The invention has the advantages that the laser cleaning is directly adopted to generate a large amount of residual particles on the surface to be removed, the residual particles are generated because the liquid in a partial molten pool is overheated in the laser ablation removing process and generates sputtering behavior under the action of plasma shock waves, and the residual particles can be enriched in the removed area, so that the negative influence is generated on the removing effect; the existing ultrasonic cleaning scheme does not have any effect on the removal of the thermal barrier coating.
Drawings
FIG. 1 is a flow chart of the present invention for cleaning a YSZ thermal barrier coating;
FIG. 2 is a schematic diagram of the operation of the present invention for cleaning YSZ thermal barrier coatings;
FIG. 3 is a graph of the original topography of the coating surface;
FIG. 4 is a topographical view of surface residual particles directly after laser removal of the coating;
FIG. 5 is a surface topography map after direct ultrasonic cleaning;
FIG. 6 is a surface topography map of the invention after ultrasonic vibration assisted laser cleaning;
FIG. 7 is a surface topography map of the invention after the ultrasonic vibration assisted laser has completely cleaned the coating;
FIG. 8 is a graph of the distribution of elements after the coating has been completely cleaned by the ultrasonic vibration assisted laser of the present invention;
wherein: 1. a laser; 2. an optical galvanometer; 3. an optical focusing lens; 4. a cooling device; 5. a console; 6. an ultrasonic vibration generator.
Detailed Description
The present invention is further illustrated by the following examples.
As shown in fig. 2, which is an operation schematic diagram of the ultrasonic vibration assisted laser cleaning technology of the present invention, the solid laser adopted by the present invention comprises a laser 1, an optical galvanometer 2, an optical focusing lens 3, a cooling device 4, a console 5 and an ultrasonic vibration generator 6. The optical galvanometer controls a laser cleaning moving track, the optical focusing lens controls a cleaning surface to be consistent with a light beam focusing surface in a laser cleaning process, the cooling device prevents the cleaning effect from being damaged by overheating of equipment in the laser cleaning process, the console is responsible for setting laser cleaning process parameters, and the ultrasonic vibration generator is responsible for generating ultrasonic vibration waves in an aqueous medium environment.
As shown in the attached figure 1, the method is a flow chart of the cleaning steps adopted by the invention, and comprises the following specific steps:
s1, YSZ coating surface pretreatment: absolute ethyl alcohol with the purity of 95-99.9% is used as a soaking solution, impurities such as dust and the like on the surface of a material to be cleaned are removed by using ultrasonic cleaning equipment, the ultrasonic cleaning time is 10min, and then the material is dried in a drying box at the temperature of 60-70 ℃ for 2-3h, so that the residual absolute ethyl alcohol on the surface of the YSZ coating to be cleaned is fully volatilized and cannot generate spontaneous combustion;
s2, beam adjustment: placing a YSZ coating to be cleaned in an ultrasonic cleaning pool in a laser cleaning operation platform, adjusting a laser beam, and ensuring that the beam is vertically incident on the surface of a YSZ coating material in the cleaning process, wherein a solution medium in the pool is water;
setting parameters: setting laser parameters, wherein the power P is 40W-100W, the laser scanning speed v is 20mm/s-200mm/s, the repetition frequency f is 20kHz-40kHz, the spot overlapping rate eta is obtained by a formula eta = 1-v/(2 x f x D), the spot size D is controlled within the range of 10μm-60μm in the cleaning process, and the spot overlapping rate is controlled within the range of 97.5% -99.0%. Setting ultrasonic power of 60W-80W and repetition frequency of 40kHz-100kHz. The solution medium is water, and no other cleaning reagent is added.
And removing the YSZ coating layer by layer in a multi-scanning mode to obtain a removed base material, namely completing the removal of the YSZ coating layer.
Example 1
1. And (3) keeping the distance between the focusing lens and the surface of the YSZ coating at 160-200mm, and vertically irradiating the laser beam above the surface of the YSZ coating to be cleaned, wherein the thickness of the coating is 100-220 mu m.
2. Setting parameters: the laser power is 40W, the pulse width is 5 mus, the pulse frequency is 40kHZ, and the spot overlapping rate is controlled to be 97.5-99.0%; the laser scanning speed is 20mm/s-100mm/s, and the laser spot size is 10-60 mu m; the ultrasonic power is 80W, the repetition frequency is 40kHz, and finally, laser cleaning process parameters are set based on the parameter ranges, and the YSZ coating is removed in a layer-by-layer multi-time scanning mode. Wherein, the step 1 and the step 2 in the example 1 are repeated by layer for multiple times of scanning, the cleaning operation is finished when no Zr element exists on the surface, and as shown in figures 7 to 8, the ultrasonic vibration assisted laser completely cleans the coating at the position A, B.
As shown in fig. 6, the surface topography is obtained by combining laser and ultrasonic vibration, and it can be seen from the surface topography that the surface particles are significantly reduced and the cracks are also significantly reduced, and the range of the process parameters set by the method can effectively ensure the stability of the removal effect.
Comparative example 1
Cleaning with laser only
The setting parameters are specifically as follows: laser parameters were set, where the power P was 40W, the scanning speed v was equal to 100mm/s, the repetition frequency f was 40kHz, the spot lap ratio η was obtained by the formula η = 1-v/(2 f x D), the spot size D was controlled in the range of 10 μm to 60 μm during cleaning, and the lap ratio was controlled in the range of 97.5% to 99.0%.
As shown in FIG. 4, which is a graph of the topography of the residual particles on the surface of the coating after cleaning the coating with only laser, the experimental laser power was 40W, the repetition frequency was 40kHz, and the scanning speed was 100mm/s. Experimental results show that a large amount of splash particles are left on the surface, the incomplete cleaning can have negative influence on the execution of subsequent processes, but the surface obviously has ablation removal phenomenon, so the requirement of removing the YSZ coating on the blade of the aircraft engine is not met.
Comparative example 2
Cleaning by ultrasound only
The set parameters are specifically: ultrasonic power 80W, repetition frequency 40kHz. The solution medium is water, and no other cleaning reagent is added. FIG. 5 shows a surface topography of the coating after ultrasonic cleaning alone, with an ultrasonic power of 80W and a repetition frequency of 40kHz. Comparing the original topography of the coating surface as shown in FIG. 3, the results show that the surface coating is unchanged from the original coating when cleaned with ultrasound alone.
The research verifies that the application of the laser cleaning technology to the YSZ thermal barrier coating has the technical advantages and characteristics of precision, controllability, high efficiency and environmental protection, and can avoid a plurality of problems brought by a chemical reagent cleaning method. Before the laser cleaning technology is applied to the thermal barrier coating, taking a chemical cleaning method as an example, nitric acid and hydrofluoric acid are used as main cleaning reagents, and the coating cleaning is completed through six procedures of wax sealing, acid cleaning, neutralization and the like. The purpose of wax sealing is to protect partial area from being corroded by acid liquor, and the wax sealing process needs to be carried out in advance, so that the requirement on the process execution standard is high. Meanwhile, the substrate is not damaged while the corrosion of the coating is difficult to prevent in the chemical cleaning process, and hydrogen embrittlement can be generated in serious cases. The cleaning effect of acid cleaning cannot be achieved by visual inspection, a chemical corrosion product needs to be removed by using a brush or gauze in a cleaning link, and potential hidden dangers are brought to the health of operators due to the treatment of waste liquid after chemical cleaning and an acid mist environment caused by the treatment. The problems existing in the YSZ thermal barrier coating cleaning can not be solved by the existing laser cleaning decontamination method and ultrasonic cleaning, the coating on the surface of the base material can be completely removed by the method of combining the laser cleaning decontamination method and the ultrasonic cleaning, and a reliable technical scheme is provided for solving the problems existing in the cleaning method.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered as the technical solutions and the inventive concepts of the present invention within the technical scope of the present invention.
Claims (9)
1. A method of removing a zirconia thermal barrier coating comprising the steps of:
s1, YSZ coating surface pretreatment: ultrasonic cleaning to remove surface impurities;
s2, laser beam adjustment: making the light beam vertically incident on the surface of the coating material;
s3, setting parameters: the power is 40-100W, the laser scanning speed is 20-200mm/s, and the repetition frequency is 20-40kHz; the size of a light spot is controlled to be 10-60 mu m in the cleaning process, and the overlapping rate of the light spot is controlled to be 97.5-99.0%; setting ultrasonic power at 60-80W and repeating frequency at 40-100kHz, and scanning layer by layer for multiple times until the coating is removed.
2. The method for removing the zirconia thermal barrier coating according to claim 1, wherein the step S1 is soaked with absolute ethanol with purity of 95-99.9% before the ultrasonic cleaning.
3. The method for removing the zirconia thermal barrier coating according to claim 1, wherein the ultrasonic cleaning time is 10-15min, and the drying is carried out at 60-70 ℃ until the absolute ethanol on the surface of the coating is completely volatilized.
4. The method for removing the zirconia thermal barrier coating of claim 1 wherein the solution medium during ultrasonic cleaning is water.
5. The method of removing a zirconia thermal barrier coating of claim 1 wherein the spot overlap ratio is obtained by the formula η = 1-v/(2 x f d);
wherein, v: scanning speed, f: repetition frequency, η: spot overlap ratio, D: the spot size.
6. The method for removing the zirconia thermal barrier coating according to claim 1, wherein the scanning step S3 is repeated until the Zr element on the surface is completely removed by repeating the steps S1-S3.
7. Method for removing a zirconia thermal barrier coating according to any one of claims 1 to 6 comprising the following steps:
s1, keeping the distance between a focusing lens and the surface of the YSZ coating at 160-200mm, and vertically irradiating the laser beam above the surface of the YSZ coating to be cleaned, wherein the thickness of the coating is 100-220 mu m;
s2, setting parameters: the ultrasonic power is 80W, and the repetition frequency is 40kHz; the laser power is 40W, the pulse width is 5 mus, the pulse frequency is 40-100kHZ, and the spot overlapping rate is 97.5-99.0%; the laser scanning speed is 20-100mm/s, and the laser spot size is 10-60 mu m; and (4) scanning layer by layer for multiple times to remove the YSZ coating.
8. The equipment for removing the thermal barrier coating of the zirconium oxide is characterized by comprising a laser (1), wherein a pulse light beam emitted by the laser (1) sequentially passes through an optical vibrating mirror (2) and an optical focusing lens (3) and is emitted into an ultrasonic vibration generator (6).
9. The apparatus for removing a zirconia thermal barrier coating according to claim 8 characterized in that the laser (1) is connected to a cooling apparatus (4) and a console (5).
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116571489A (en) * | 2023-05-25 | 2023-08-11 | 北京金轮坤天特种机械有限公司 | High-pressure water jet cleaning method for environmental sediment on surface of thermal barrier coating |
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2023
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116571489A (en) * | 2023-05-25 | 2023-08-11 | 北京金轮坤天特种机械有限公司 | High-pressure water jet cleaning method for environmental sediment on surface of thermal barrier coating |
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