A method of laser processing a part with a thermal barrier coating and a part

Abstract

The application belongs to the field of material processing engineering, and discloses a laser processing method of a part with a thermal barrier coating and the part. Firstly, a defocused laser is used to preheat a target processing area and a peripheral area, and the temperature is controlled below the ablation threshold of the coating to reduce the temperature gradient. Then, a laser with a first preset energy density is used to scan along a contour trajectory to form an isolation groove as a stress release boundary and a crack barrier. Finally, a laser with a second preset energy density is used to process a closed area defined by the isolation groove until completion. The preheating uniformizes the temperature distribution of the coating and the substrate, and reduces the accumulation of instantaneous thermal stress caused by the difference in thermal conductivity. The isolation groove absorbs local stress and blocks the crack propagation path by pre-setting a physical boundary, preventing the spread of thermal damage. The internal processing is carried out in a controlled environment to avoid direct damage to the interface. The method significantly reduces the risk of coating micro-cracks, network cracks and peeling, and improves the processing precision, the service life of the part and the overall reliability.

Description

Technical Field

[0001] This invention belongs to the field of materials processing engineering technology, and particularly relates to a laser processing method and part for parts with thermal barrier coating. Background Technology

[0002] As high-end equipment such as aero-engines and gas turbines iterate towards higher efficiency and higher thrust-to-weight ratios, the operating temperatures of their hot-end components (such as turbine blades and combustion chambers) far exceed the temperature resistance limits of the high-temperature alloy substrate. Against this backdrop, thermal barrier coating systems have become an indispensable "thermal protective layer" for these critical components. This system typically consists of a metal bonding layer that provides anti-oxidation and adhesion, and a ceramic surface layer that provides thermal insulation. It effectively reduces the operating temperature of the substrate and significantly extends the service life of the component. In the manufacturing process of components with thermal barrier coatings, laser processing technology has become the mainstream process choice for achieving the machining of fine structures such as film pores.

[0003] In actual production, hot-end components with thermal barrier coatings often require precision laser processing (such as drilling and etching). However, ceramic coatings and metal substrates differ significantly in material properties: ceramic coatings have low thermal conductivity and high brittleness, while metal substrates have high thermal conductivity and good toughness. The instantaneous thermal shock generated during laser processing creates enormous thermal stress near the interface between the ceramic coating and the metal substrate. This thermal stress easily leads to defects such as microcracks and network cracks within the ceramic layer, and in severe cases, it can even cause the coating to warp and peel off from the metal substrate. Furthermore, improper laser energy control can directly damage the interface between the coating and the substrate. Once the interface oxidizes or is damaged, the adhesion between the coating and the substrate will decrease sharply.

[0004] Therefore, when laser processing is performed on parts with thermal barrier coatings, the laser energy can easily cause uncontrollable thermal damage such as cracks and peeling of the coating due to the huge difference in the thermophysical properties (such as thermal conductivity and coefficient of thermal expansion) between the coating and the substrate material. This damage can then spread to non-processed areas, affecting the lifespan and reliability of the parts. Summary of the Invention

[0005] This invention provides a laser processing method and part for parts with thermal barrier coatings. This laser processing method can effectively solve the problem that laser energy can easily cause uncontrollable thermal damage such as cracking and peeling of the coating, thus ensuring the lifespan and reliability of the parts.

[0006] To achieve the above objectives, the present invention employs the following technical content: A laser processing method for parts with thermal barrier coatings, comprising: A defocused laser is used to preheat the target processing area and the surrounding area of ​​the part to be processed, so as to reduce the temperature gradient between the target processing area and the surrounding area; wherein, the defocused laser energy is controlled below the ablation threshold of the thermal barrier coating material. After preheating, a laser with a first preset energy density is used to scan along the contour trajectory of the target processing area to obtain an isolation groove; the isolation groove is used as a preset stress relief boundary and crack propagation barrier. The closed area defined by the isolation groove is processed using a laser with a second preset energy density until the set requirements are met, so as to complete the laser processing of the part with thermal barrier coating.

[0007] Furthermore, the process of preheating the target processing area of ​​the part and the surrounding area of ​​the target processing area using defocused laser includes: Infrared thermal imagers were used to collect temperature data of the preheating area in real time. The output power or scanning speed of the defocused laser is dynamically adjusted based on the temperature data of the preheating area to keep the temperature of the preheating area uniform and controlled within a predetermined range.

[0008] Furthermore, during the process of dynamically adjusting the output power or scanning speed of the defocused laser based on the temperature data of the preheating area, if it is determined that the temperature data of the preheating area exceeds the predetermined value range, the output power and / or scanning speed are reduced until the temperature of the preheating area remains uniform and controlled within the predetermined value range.

[0009] Further, the scanning along the contour trajectory of the target processing area using a laser with a first preset energy density includes: The laser is switched to a focusing mode to adjust the laser focus to a first preset energy density; wherein the first preset energy density is lower than an energy density threshold. An isolation groove is prepared by scanning along the contour trajectory of the target processing area using a laser with a first preset energy density; wherein the isolation groove is a continuous and closed groove.

[0010] Furthermore, the process of scanning along the contour trajectory of the target processing area using a laser with a first preset energy density includes: The depth of the isolation groove is acquired in real time using a confocal displacement sensor; The laser parameters are dynamically adjusted according to the depth of the isolation groove to ensure that the depth of the isolation groove is within a certain accuracy range; wherein the accuracy range is within ±10% of the thickness of the thermal barrier coating.

[0011] Furthermore, the laser parameters include the laser energy density, pulse width, number of scans, and focal length; by adjusting the laser energy density, pulse width, number of scans, and focal length, the depth of the isolation groove is made equal to the thickness of the thermal barrier coating.

[0012] Furthermore, the process of using a laser with a second preset energy density to process the enclosed area defined by the isolation groove includes: The laser is adjusted to a second preset energy density; wherein the second preset energy density is higher than an energy density threshold. A laser with a second preset energy density is used to process the closed area defined by the isolation groove; the closed area is formed by the isolation groove until the set requirements are met.

[0013] Furthermore, in the process of processing the closed area defined by the isolation groove using a laser with a second preset energy density, the setting requirements include one or any combination of processing depth, shape, and removal effect.

[0014] Furthermore, the trajectory of the isolation groove is determined by the shape of the processing area of ​​the part to be processed.

[0015] A part with a thermal barrier coating is processed using the aforementioned laser processing method for parts with thermal barrier coatings. Compared with the prior art, the present invention has the following advantages: This invention provides a laser processing method for parts with thermal barrier coatings. First, a defocused laser is used to preheat the target processing area and its surrounding area, controlling the temperature below the coating ablation threshold to reduce the temperature gradient. Then, a laser with a first preset energy density scans along the contour trajectory to form an isolation groove, serving as a stress release boundary and crack barrier. Finally, a laser with a second preset energy density processes the closed area defined by the isolation groove until completion. Preheating uniformly distributes the temperature between the coating and the substrate, reducing the accumulation of instantaneous thermal stress caused by differences in thermal conductivity. The isolation groove absorbs local stress and blocks crack propagation paths through pre-defined physical boundaries, preventing the spread of thermal damage. Internal processing is performed in a controlled environment, avoiding direct damage to the interface. This method effectively suppresses the generation of microcracks and network cracks in the coating, reduces the risk of peeling, maintains the bonding strength between the coating and the substrate interface, and effectively prevents damage to non-processed areas, thereby significantly improving processing accuracy, component lifespan, and overall reliability.

[0016] Preferably, in this invention, an infrared thermal imager is introduced during the preheating process to collect temperature data in real time, and the output power or scanning speed of the defocused laser is dynamically adjusted to maintain uniform temperature control within a predetermined range. Real-time temperature monitoring provides a feedback mechanism, which adaptively adjusts laser parameters to avoid localized overheating or underheating, ensuring a consistent temperature distribution in the preheating area. This enhances the stability and uniformity of the preheating process, further reduces coating defects caused by thermal shock, and improves overall processing control accuracy.

[0017] Preferably, in this invention, when the preheating temperature exceeds a predetermined range, the output power or scanning speed is actively reduced until the temperature returns to the control range. By rapidly responding to temperature deviations, the accumulation of temperature fluctuations is prevented, and a stable heating state is maintained to avoid damage to the coating due to instantaneous thermal gradients. This improves the reliability and response speed of temperature regulation, reduces interface oxidation or coating warping caused by uncontrolled heating, and enhances the safety of the processing.

[0018] Preferably, in this invention, the laser is switched to focused mode during the scanning of the contour trajectory, and a continuous, closed isolation groove is prepared with a first preset energy density lower than the energy density threshold. The focused laser provides high-precision energy output, and the low energy density avoids excessive ablation of the coating, ensuring that the isolation groove forms a complete and continuous physical boundary. This ensures the integrity of the isolation groove as a stress release and crack barrier, reduces the impact of laser processing on non-target areas, and improves processing quality.

[0019] Preferably, in this invention, a confocal displacement sensor is used to collect the depth of the isolation groove in real time during the scanning process, and the laser parameters are dynamically adjusted to keep the depth within a predetermined accuracy range. Real-time depth monitoring combined with parameter feedback adjustment ensures the consistency of the isolation groove depth and avoids depth deviations affecting its function as a barrier. Effectively, this improves the geometric accuracy and reliability of the isolation groove, effectively prevents cracks from spreading to non-processed areas, and reduces the incidence of processing defects.

[0020] Preferably, in this invention, the depth of the isolation groove is precisely matched to the thickness of the thermal barrier coating by adjusting parameters such as laser energy density, pulse width, number of scans, and focal length. Multi-parameter coordinated control provides flexibility, enabling precise depth optimization to enhance stress absorption capacity. This strengthens the barrier effect of the isolation groove, maximizes thermal stress release, and ensures the protection of the coating interface during processing.

[0021] Preferably, in this invention, a second preset energy density laser higher than the energy density threshold is used when processing the enclosed area. The high energy density accelerates material removal efficiency, while the isolation groove acts as a pre-set barrier to isolate thermal effects and prevent energy diffusion from damaging the surrounding area. This improves internal processing efficiency, avoids incomplete processing or interface damage due to insufficient energy, and maintains the integrity of the processed area.

[0022] Preferably, in this invention, the set requirements include processing depth, shape, and removal effect, or a combination thereof. By parametrically targeting the processing, the laser energy is precisely matched to specific needs, achieving controllable removal. This enhances the applicability and flexibility of the method, adapting to diverse processing tasks and improving the quality and practicality of the finished product.

[0023] Preferably, in this invention, the trajectory of the isolation groove is customized according to the shape of the processing area. This customized trajectory ensures the isolation groove closely conforms to the processing contour, providing a targeted stress release boundary. This optimizes the crack prevention effect, maximizes protection of non-processed areas, and ensures the overall structural stability of the part.

[0024] This invention also provides a part with a thermal barrier coating, manufactured using the aforementioned laser processing method. The preheating process significantly reduces the instantaneous thermal shock and interfacial thermal stress accumulation caused by the difference in thermophysical properties between the ceramic coating and the metal substrate. The formed isolation groove acts as a physical barrier, effectively absorbing localized stress concentration and blocking the propagation path of thermal cracks to unprocessed areas, while simultaneously protecting the coating-substrate interface from direct laser damage. The integrity of the thermal barrier coating and the interfacial bonding strength of the part manufactured using the aforementioned laser processing method are significantly improved, effectively avoiding processing-induced microcracks, network cracks, coating peeling, and interfacial oxidation failure, thereby greatly improving the service reliability and service life of the part in high-temperature and harsh environments. Attached Figure Description

[0025] Figure 1 A schematic diagram of thermally induced damage to the coating provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of laser processing of thermal barrier coatings provided in an embodiment of the present invention. Detailed Implementation

[0026] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0030] The technical terms used in this invention are explained as follows: Defocused laser refers to a laser technology in which the laser beam is not focused on the target surface during propagation, but rather acts on the material or object in a scattered or divergent state.

[0031] As stated in the background, Figure 1 As shown, due to the significant difference in thermophysical properties between the coating and the substrate material, laser energy can easily cause uncontrollable thermal damage such as cracking and peeling of the coating, which can then spread to unprocessed areas, affecting component lifespan and reliability. Currently, the industry generally adopts the method of optimizing single laser parameters (such as power, speed, and pulse frequency) to find a "balance point" that can simultaneously meet processing efficiency and coating protection requirements for laser processing of high-temperature alloys with thermal barrier coatings. Researchers in this field have developed an innovative laser composite processing technology that uses a two-step millisecond-femtosecond laser method to prepare high-quality micropores on thermal barrier coated nickel-based alloys. The study found that the millisecond laser stage effectively controlled melt flow and hole taper through an optimized decreasing power pulse sequence, while the femtosecond laser finishing stage significantly improved the surface quality of the hole walls. Process parameter optimization analysis shows that processing efficiency can be further improved by increasing power and speed. This method successfully achieved a processing effect with sharp hole edges and smooth hole walls, providing an efficient solution for micropore processing of thermal barrier coatings; however, optimizing laser parameters has limitations, as it cannot fundamentally solve the physical problem of thermo-mechanical damage diffusion. The parameter optimization window is usually very narrow, and even for coated parts of different batches and in different states, a lot of tedious process tests need to be carried out again.

[0032] To address the aforementioned issues, this embodiment provides a laser processing method for parts with thermal barrier coatings. This innovative method can actively guide, constrain, and isolate the thermo-mechanical damage caused by laser processing, strictly limiting it to a predetermined processing area, thereby fundamentally ensuring the integrity of the coating in non-processed areas.

[0033] This embodiment provides a laser processing method for parts with thermal barrier coatings, including: A defocused laser is used to preheat the target processing area and the surrounding area of ​​the part to be processed, so as to reduce the temperature gradient between the target processing area and the surrounding area; wherein, the defocused laser energy is controlled below the ablation threshold of the thermal barrier coating material. After preheating, a laser with a first preset energy density is used to scan along the contour trajectory of the target processing area to obtain an isolation groove; the isolation groove is used as a preset stress relief boundary and crack propagation barrier. The closed area defined by the isolation groove is processed using a laser with a second preset energy density until the set requirements are met, so as to complete the laser processing of the part with thermal barrier coating.

[0034] It is evident that this laser processing method, through precise energy and depth control, strictly confines the thermo-mechanical damage during processing to a predetermined area, fundamentally solving the problem of uncontrollable damage in the laser processing of heterogeneous materials, and significantly improving the processing quality of micro-holes in coated parts and the reliability of components.

[0035] The laser processing method will be further described below with reference to the accompanying drawings and embodiments: like Figure 2 As shown, this embodiment provides a laser processing method for parts with thermal barrier coatings, and the specific steps are as follows: Step 1: Defocus Preheating. A defocused laser beam scans and heats the target processing area and its surrounding area. An integrated infrared thermal imager is used to monitor the temperature field distribution of the preheated area in real time. Based on the feedback temperature data, the laser output power or scanning speed is dynamically adjusted to ensure that the temperature of the entire preheated area is uniform and strictly controlled within a predetermined value. The energy density of the laser beam is set to a level sufficient to heat the material but below its ablation threshold. This causes the thermal barrier coating and substrate material in the area to be processed to undergo uniform and gentle expansion beforehand, reducing the temperature gradient between this area and the surrounding materials, thereby pre-releasing some thermal stress and providing a "stress buffer" for subsequent processing. The core control of this step lies in heat input management, achieving uniform preheating without melting through the coordination of defocusing amount, laser power, scanning speed, and scanning path.

[0036] Step Two: Preparing the Isolation Groove. After preheating, a low-energy-density focused laser beam is used to precisely scan along the pre-defined contour trajectory of the target processing area, creating a continuous, closed shallow groove. A confocal displacement sensor is used to monitor the groove bottom depth in real time. For non-circular hole shapes (such as the diffused shape commonly used in film pores), the path of the isolation groove can be offset to ensure the accuracy of the final processing contour. When the detected depth is close to the coating thickness, the depth of the shallow groove is precisely controlled to be approximately equal to the thickness of the thermal barrier coating, where ±10% process fluctuation is allowed, preferably the depth of the isolation groove is consistent with the thickness of the thermal barrier coating. This means that the groove will completely penetrate the entire thermal barrier coating, but with little or no damage to the underlying metal substrate. This isolation groove acts as a pre-set physical and thermal barrier. It artificially creates a controllable and regular defect boundary before the main processing begins. This boundary will serve as a stress concentration point and crack termination zone, effectively blocking the propagation of thermal stress waves and microcracks generated during subsequent high-energy processing to non-processed areas. The core of this step lies in depth accuracy. By precisely controlling the laser energy density, pulse width, number of scans, and focal length, the groove depth is ensured to terminate precisely at the coating / substrate interface.

[0037] Step 3: Main Processing. Within the area defined and enclosed by the isolation groove, the material is processed using appropriate laser parameters to achieve the desired processing depth, shape, or removal effect (e.g., creating cooling holes, grooves, etc.). Because the processing area is surrounded by the isolation groove, the thermal stress and cracks generated in this step will be effectively confined within the isolation zone.

[0038] For example, steps one, two, and three are all completed continuously by the same laser processing equipment, and the laser parameters are automatically switched by the CNC program. The laser parameters include, but are not limited to, energy density, pulse frequency, defocusing amount, and scanning speed, thereby ensuring the continuity and accuracy of the processing.

[0039] Furthermore, the trajectory of the isolation groove can be set according to the shape of the final required processing area. For a round hole, the trajectory is circular; for a square groove, the trajectory is rectangular; for a complex shape, the trajectory is its outline shape.

[0040] For example, this embodiment also provides a part with a thermal barrier coating, which is processed by the above-described laser processing method; based on the above-described laser processing method for parts with thermal barrier coatings, the thermal impact of the thermal barrier coating material can be effectively suppressed during the laser processing of the part, thus ensuring the lifespan and reliability of the part.

[0041] In summary, the laser processing method and the part with thermal barrier coating provided by this invention have the following advantages compared with existing buoys: First, the three-step processing method proposed in this invention is a gradual process of energy input from mild to intense, and from surface to point, avoiding instantaneous and violent energy impact. The isolation groove physically creates an "energy depression." When the stress wave generated by subsequent high-energy processing propagates to this boundary, it will be reflected, dissipated, or have its propagation path changed (the crack tip is blunted or deflected at the groove), thus making it impossible to cross.

[0042] Secondly, the preheating stage reduces the yield strength of the material, causing a certain degree of plastic deformation and releasing some internal stress in advance, which is equivalent to "preheating stress". A controllable and regular "pre-set defect" is artificially introduced, which becomes a stress concentration point and release zone. The high stress generated during subsequent processing will preferentially be released into this pre-set, regular low-strength area, rather than randomly and uncontrollably expanding outward to form cracks.

[0043] Third, precise control of the processing depth is achieved on the order of coating thickness. The coating and the substrate are heterogeneous materials with vastly different mechanical properties, making them a natural weak point. The isolation groove terminates precisely at this interface, completely severing the continuity of the coating while avoiding unnecessary damage to the substrate. The isolation groove severs the lateral continuity of the coating, thereby effectively suppressing lateral expansion stress. The introduction of the isolation groove becomes crucial in preventing coating peeling.

[0044] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A laser processing method for parts with thermal barrier coatings, characterized in that, include: A defocused laser is used to preheat the target processing area and the surrounding area of ​​the part to be processed, so as to reduce the temperature gradient between the target processing area and the surrounding area; wherein, the defocused laser energy is controlled below the ablation threshold of the thermal barrier coating material. After preheating, the laser is switched to focusing mode, and a laser with a first preset energy density is used to scan along the contour trajectory of the target processing area to obtain an isolation groove; wherein, the first preset energy density is lower than the energy density threshold; the isolation groove is a continuous, closed groove; the isolation groove is used as a preset stress release boundary and crack propagation barrier; the scanning process includes: using a confocal displacement sensor to collect the depth of the isolation groove in real time; dynamically adjusting the laser parameters according to the depth of the isolation groove so that the depth of the isolation groove is equal to the thickness of the thermal barrier coating; The closed area defined by the isolation groove is processed using a laser with a second preset energy density until the set requirements are met, so as to complete the laser processing of the part with thermal barrier coating; wherein, the second preset energy density is higher than the energy density threshold.

2. The laser processing method for a part with a thermal barrier coating according to claim 1, characterized in that, The process of preheating the target processing area and the surrounding area of ​​the part using defocused laser includes: Infrared thermal imagers were used to collect temperature data of the preheating area in real time. The output power or scanning speed of the defocused laser is dynamically adjusted based on the temperature data of the preheating area to keep the temperature of the preheating area uniform and controlled within a predetermined range.

3. The laser processing method for a part with a thermal barrier coating according to claim 2, characterized in that, During the process of dynamically adjusting the output power or scanning speed of the defocused laser based on the temperature data of the preheating area, if it is determined that the temperature data of the preheating area exceeds the predetermined value range, the output power and / or scanning speed are reduced until the temperature of the preheating area remains uniform and controlled within the predetermined value range.

4. The laser processing method for a part with a thermal barrier coating according to claim 1, characterized in that, The laser parameters include the laser energy density, pulse width, number of scans, and focal length; by adjusting the laser energy density, pulse width, number of scans, and focal length, the depth of the isolation groove is made equal to the thickness of the thermal barrier coating.

5. The laser processing method for a part with a thermal barrier coating according to claim 1, characterized in that, The process of using a laser with a second preset energy density to process the enclosed area defined by the isolation groove includes: Adjust the laser to the second preset energy density; A laser with a second preset energy density is used to process the closed area defined by the isolation groove; the closed area is formed by the isolation groove until the set requirements are met.

6. The laser processing method for a part with a thermal barrier coating according to claim 1, characterized in that, In the process of processing the closed area defined by the isolation groove using a laser with a second preset energy density, the setting requirements include one or any combination of processing depth, shape, and removal effect.

7. The laser processing method for a part with a thermal barrier coating according to claim 1, characterized in that, The trajectory of the isolation groove is determined by the shape of the processing area of ​​the part to be processed.

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