阅读说明：本技术 一种涡轮叶片热障涂层飞秒激光精准化去除方法 (Femtosecond laser precision removing method for thermal barrier coating of turbine blade ) 是由 周留成 蔡振兵 俞延庆 杨家仙 李玉琴 王学德 于 2019-09-19 设计创作，主要内容包括：本发明涉及激光加工技术领域,且公开了一种涡轮叶片热障涂层飞秒激光精准化去除方法,主要包括以下步骤：步骤一,加工工件前,将待加工工件安装于工作台上并设定激光器的相应参数,主要包括激光的波长、脉冲宽度、重复频率、激光器工作功率；步骤二,利用CAD软件进行加工路径的设定,利用激光打标控制软件设定具体加工条件,包括扫描速度,扫描次数,扫描线间距；步骤三,加工开始时,超短脉冲激光束从激光源发射。该涡轮叶片热障涂层飞秒激光精准化去除方法,通过设定激光器的性能参数以及通过控制系统调节光束调整传输协调以及监测系统,实现对复杂曲面上的热障涂层高效、高精度去除。(The invention relates to the technical field of laser processing, and discloses a femtosecond laser precision removal method for a thermal barrier coating of a turbine blade, which mainly comprises the following steps: before a workpiece is machined, mounting the workpiece to be machined on a workbench and setting corresponding parameters of a laser, wherein the parameters mainly comprise the wavelength, the pulse width, the repetition frequency and the working power of the laser; setting a processing path by using CAD software, and setting specific processing conditions including scanning speed, scanning times and scanning line spacing by using laser marking control software; and step three, emitting the ultra-short pulse laser beam from the laser source when the processing is started. According to the femtosecond laser precision removing method for the thermal barrier coating of the turbine blade, the thermal barrier coating on a complex curved surface is removed efficiently and precisely by setting performance parameters of a laser and adjusting a light beam adjustment transmission coordination and monitoring system through a control system.)

1. A femtosecond laser precision removing method for a thermal barrier coating of a turbine blade is characterized by mainly comprising the following steps:

before a workpiece is machined, mounting the workpiece to be machined on a workbench and setting corresponding parameters of a laser, wherein the parameters mainly comprise the wavelength, the pulse width, the repetition frequency and the working power of the laser;

setting a processing path by using CAD software, and setting specific processing conditions including scanning speed, scanning times and scanning line spacing by using laser marking control software;

when the processing is started, ultra-short pulse laser beams are emitted from a laser source, are expanded and straightened through a light beam transmission adjusting system, are reflected through a scanning vibrating mirror, and are subjected to parallel focusing through a focusing mirror and then are irradiated onto the surface of a workpiece to be processed;

in the processing process, the control system coordinates the light beam transmission system and the workbench to enable the pulse laser beam to remove the thermal barrier coating on the surface according to an appointed path, wherein the workpiece moves along with the workbench, and the scanning galvanometer swings in a reciprocating manner to enable the point-like circular light spots to be scanned into quasi-linear circular light spots;

observing the cleaning effect through a real-time monitoring system and feeding back the cleaning effect to a control system in the machining process, and adjusting corresponding parameters in real time by the control system to realize optimized cleaning;

and step six, finishing the cleaning process and taking out the machined workpiece.

2. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the ultrashort pulseThe pulse width (single pulse duration) of the laser beam can reach femtosecond level (10) ^-15Second power) or even lower.

3. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the light beam transmission system can adjust parameters such as spot diameter, defocusing amount and the like in the laser processing process.

4. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the control system can coordinate the workbench and the light beam transmission system to remove the thermal barrier coating on the complex curved surface.

5. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the ultrashort pulse laser beam has extremely high peak energy density and extremely short pulse width, and ultrashort pulse laser photons are absorbed by electrons in the material by utilizing the interaction of laser and plasma in the processing process, so that the material is removed, and a nonmetal ceramic layer and a strong adhesive force bonding layer which has physicochemical reaction with a base material can be removed.

6. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the pulse width of the ultrashort pulse laser beam is extremely short, the pulse width of the ultrashort pulse laser beam is shorter than the characteristic time (such as electronic relaxation time, electronic-phonon relaxation time and the like) of most physical and chemical processes, and the ultrashort pulse laser beam can realize 'cold processing' in a true sense by introducing extremely small amount of heat in the processing process.

7. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the ultrashort pulse laser beam is different from the long pulse laser beam, ablation gasification and impact vibration of the substrate cannot be caused, so that a melting zone and microcracks cannot be formed in the processing process, the controllability is high, and the surface of the substrate is not damaged or is slightly damaged.

8. The femtosecond laser precision removal method for the thermal barrier coating of the turbine blade as claimed in claim 1, wherein: the gas nozzle can be arranged in the process of removing the thermal barrier coating on the surface by the ultrashort pulse laser beam, and the gas nozzle can release gas so as to avoid secondary pollution on the surface of the substrate in the process of removing the thermal barrier coating and improve the removal efficiency.

Technical Field

The invention relates to the technical field of laser processing, in particular to a femtosecond laser precision removing method for a thermal barrier coating of a turbine blade.

Background

Against the background of the rapid development of aeronautical technology, aeroengines are moving towards high flow rates, high thrust-weight ratios, which depend to a large extent on the inlet temperature of the engine turbine. The thrust-weight ratio of the next generation aero-engine is more than 12, and the service temperature of hot end parts such as turbine blades and the like of the next generation aero-engine is required to reach 2000K. With the improvement of the requirement on the service temperature of the hot end component of the engine, the design requirement of the aircraft engine cannot be met only by the high-temperature resistance of the high-temperature alloy. In the last four decades, in order to meet the requirements of turbine blades and other thermal end parts on extreme service environments such as high-temperature impact, high-temperature strong corrosion and the like, the field of aeroengines always adopts a method for preparing a thermal barrier coating on the surface of a high-temperature alloy.

Generally, a thermal barrier coating structure used in practical engineering is a two-layer structure. The surface layer is a ceramic layer and mainly plays a role in heat insulation; the inner layer is an adhesive layer and mainly plays a role in enhancing the binding force and resisting oxidation. But can cause partial failure and destruction of the thermal barrier coating in the actual operating environment and during the coating process. Because the shape design of the hot end part of the engine is complex and the cost is high, the re-processing manufacturing cost is high, and the thermal barrier coating has good insulation property and strong adhesive force, the existing removing method has certain limitation. Therefore, a femtosecond laser precision removing method for the thermal barrier coating of the turbine blade is provided.

Disclosure of Invention

The invention provides a femtosecond laser precision removing method for a thermal barrier coating of a turbine blade, which solves the problems in the background technology.

The invention provides the following technical scheme: a femtosecond laser precision removing method for a thermal barrier coating of a turbine blade mainly comprises the following steps:

before a workpiece is machined, mounting the workpiece to be machined on a workbench and setting corresponding parameters of a laser, wherein the parameters mainly comprise the wavelength, the pulse width, the repetition frequency and the working power of the laser;

setting a processing path by using CAD software, and setting specific processing conditions including scanning speed, scanning times and scanning line spacing by using laser marking control software;

when the processing is started, ultra-short pulse laser beams are emitted from a laser source, are expanded and straightened through a light beam transmission adjusting system, are reflected through a scanning vibrating mirror, and are subjected to parallel focusing through a focusing mirror and then are irradiated onto the surface of a workpiece to be processed;

in the processing process, the control system coordinates the light beam transmission system and the workbench to enable the pulse laser beam to remove the thermal barrier coating on the surface according to an appointed path, wherein the workpiece moves along with the workbench, and the scanning galvanometer swings in a reciprocating manner to enable the point-like circular light spots to be scanned into quasi-linear circular light spots;

observing the cleaning effect through a real-time monitoring system and feeding back the cleaning effect to a control system in the machining process, and adjusting corresponding parameters in real time by the control system to realize optimized cleaning;

and step six, finishing the cleaning process and taking out the machined workpiece.

Preferably, the pulse width (single pulse duration) of the ultrashort pulse laser beam can reach femtosecond level (10) ^-15Second power) or even lower.

Preferably, the beam transmission system can adjust parameters such as spot diameter, defocusing amount and the like in the laser processing process.

Preferably, the control system can coordinate the workbench and the light beam transmission system to remove the thermal barrier coating on the complex curved surface.

Preferably, the ultrashort pulse laser beam has extremely high peak energy density and extremely short pulse width, and the ultrashort pulse laser photons are absorbed by electrons in the material by utilizing the interaction of laser and plasma in the processing process, so that the material is removed, and the nonmetal ceramic layer and the strong adhesive force bonding layer which has physicochemical reaction with the base material can be removed.

Preferably, the pulse width of the ultrashort pulse laser beam is extremely short, the pulse width is shorter than the characteristic time of most physicochemical processes (such as electron relaxation time, electron-phonon relaxation time and the like), and the processing process introduces extremely small amount of heat, so that the real 'cold processing' can be realized.

Preferably, the ultrashort pulse laser beam is different from the long pulse laser beam, ablation gasification and impact vibration of the substrate cannot be caused, so that a melting zone and microcracks cannot be formed in the processing process, the controllability is extremely high, and the surface of the substrate is not damaged or is slightly damaged.

Preferably, a gas nozzle can be arranged in the process of removing the thermal barrier coating on the surface by the ultrashort pulse laser beam, and the gas nozzle can release gas so as to avoid secondary pollution on the surface of the substrate in the process of removing the thermal barrier coating and improve the removal efficiency.

The invention has the following beneficial effects:

1. according to the femtosecond laser precision removing method for the thermal barrier coating of the turbine blade, the thermal barrier coating on a complex curved surface is removed efficiently and precisely by setting performance parameters of a laser and adjusting a light beam adjustment transmission coordination and monitoring system through a control system.

2. According to the femtosecond laser precision removing method for the thermal barrier coating of the turbine blade, the ultrashort pulse laser beam is directly acted on the surface of the thermal barrier coating to be removed, and the surface non-metal ceramic layer and the bonding layer with strong adhesive force in the turbine blade can be removed due to the fact that the ultrashort pulse laser beam is short in pulse width and high in peak energy density.

3. According to the femtosecond laser precision removing method for the thermal barrier coating of the turbine blade, the thermal barrier coating on the surface of the material is removed in a 'cold processing' mode by introducing a very small amount of heat in the processing process, a melting zone, a microcrack and the like are not formed in the processing process, the damage to the surface of a base material is very small, the removing effect is good, and the femtosecond laser precision removing method has a good application prospect in the aspect of removing the thermal barrier coating on the surface.

Drawings

FIG. 1 is a schematic diagram of the method for removing thermal barrier coating on surface by ultrashort pulse laser of the present invention;

FIG. 2 is a schematic view of an exemplary thermal barrier coating;

FIG. 3 is a graph of the law of influence of different parameters;

FIG. 4 is SEM pictures of (a) raw (b)5W (c)10W (d)15W (e)20W after processing with different femtosecond laser powers;

FIG. 5 is the elemental content and surface roughness of the turbine surface after processing at different femtosecond laser powers;

FIG. 6 is SEM pictures of processed samples of different femtosecond laser repetition frequencies (a) unprocessed (b)100KHz (c)250KHz (d)500KHz (e)1000 KHz;

FIG. 7 is the elemental content and surface roughness of the turbine surface after different femtosecond laser repetition frequency processing;

FIG. 8 is a SEM photograph of (a) raw (b)1 time (c)10 times (d)50 times after processing at different scanning times;

FIG. 9 is a graph of the elemental content and surface roughness of the turbine surface after machining for different scan times.

In the figure: 1. a laser; 2. a galvanometer X; 3. a galvanometer Y; 4. a focusing mirror; 5. an air nozzle; 6. a substrate; 7. coating; 8. a ceramic layer; 9. an adhesive layer; 10. a substrate.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1-9, a femtosecond laser precision removing method for thermal barrier coating of turbine blade mainly includes the following steps:

before a workpiece is machined, mounting the workpiece to be machined on a workbench and setting corresponding parameters of a laser, wherein the parameters mainly comprise the wavelength, the pulse width, the repetition frequency and the working power of the laser; the laser in this embodiment is a phoros series laser from the lithuan Light Conversion company, and the basic parameters of the laser are as follows: the wavelength is 1064nm, the repetition frequency is 1-1000 kHz, the pulse width is 290fs, and the maximum average power is 20W;

setting a processing path by using CAD software, and setting specific processing conditions including scanning speed, scanning times and scanning line spacing by using laser marking control software;

when the processing is started, ultra-short pulse laser beams are emitted from a laser source, are expanded and straightened through a light beam transmission adjusting system, are reflected through a scanning vibrating mirror, and are subjected to parallel focusing through a focusing mirror and then are irradiated onto the surface of a workpiece to be processed;

in the processing process, the control system coordinates the light beam transmission system and the workbench to enable the pulse laser beam to remove the thermal barrier coating on the surface according to an appointed path, wherein the workpiece moves along with the workbench, and the scanning galvanometer swings in a reciprocating manner to enable the point-like circular light spots to be scanned into quasi-linear circular light spots;

observing the cleaning effect through a real-time monitoring system and feeding back the cleaning effect to a control system in the machining process, and adjusting corresponding parameters in real time by the control system to realize optimized cleaning;

sixthly, finishing the cleaning process, and taking out the processed workpiece, wherein in the embodiment, a femtosecond laser beam is adopted to remove the bonding layer on the surface of the high-temperature alloy, the base material is DZ125 directionally solidified column crystal high-temperature alloy, and the mass fraction of Al is 4.8-5.4%; the material of the bonding layer is NiCrAlYSi, the thickness is 25-35 mu m, and the mass fraction of Al is 6-10%.

Further, the pulse width (single pulse duration) of the ultrashort pulse laser beam can reach the femtosecond level (10-15 seconds) or even lower.

Furthermore, the light beam transmission system can adjust parameters such as spot diameter and defocusing amount in the laser processing process, and optimal removal of the thermal barrier coating on the surface of the material is realized through setting of the parameters.

Furthermore, the control system can coordinate the workbench and the light beam transmission system to remove the thermal barrier coating on the complex curved surface.

Furthermore, the ultrashort pulse laser beam has extremely high peak energy density and extremely short pulse width, and ultrashort pulse laser photons are absorbed by electrons in the material by utilizing the interaction of laser and plasma in the processing process, so that the material is removed, and the nonmetal ceramic layer and the strong adhesive force bonding layer which has physicochemical reaction with the base material can be removed.

Further, the pulse width of the ultrashort pulse laser beam is extremely short, the pulse width is shorter than the characteristic time of most physical and chemical processes (such as electron relaxation time, electron-phonon relaxation time and the like), and the processing process introduces extremely small amount of heat, so that the real 'cold processing' can be realized.

Furthermore, the ultrashort pulse laser beam is different from the long pulse laser beam, ablation gasification and impact vibration of the substrate cannot be caused, so that a melting zone and microcracks cannot be formed in the processing process, the controllability is high, and the surface of the substrate is not damaged or is slightly damaged.

Further, a gas nozzle can be arranged in the process of removing the thermal barrier coating on the surface by the ultrashort pulse laser beam, and the gas nozzle can release gas so as to avoid secondary pollution on the surface of the substrate in the process of removing the thermal barrier coating and improve the removal efficiency.