Thickness monitoring method for electron beam physical vapor deposition thermal barrier coating

Abstract

The invention discloses a thickness monitoring method for an electron beam physical vapor deposition thermal barrier coating, and relates to the technical field of thermal barrier coating preparation, and the thickness monitoring method comprises the following steps: arranging a monitoring device in a vacuum cavity, and selecting a target material of a proper material; the thermal barrier coating is prepared through the electron beam physical vapor deposition technology, and various parameters in the technological process are obtained; calculating the thickness of the thermal barrier coating through a computer by using a custom function formula; and after the calculated value is obtained, stopping the technological process, measuring the actual thickness of the sample, and comparing the actual thickness with the calculated value for analysis. Compared with the prior art, the method has the advantages that the thickness of the thermal barrier coating in the technological process can be calculated by acquiring the target material consumption mass and combining various parameters in the high-vacuum and high-temperature electron beam physical vapor deposition technological process, the stability of the technology and the coating quality is improved, meanwhile, the conditions of repeated reworking and defective products are avoided, and the production efficiency is improved. The process cost is reduced, and the method has a good practical application prospect.

Description

Technical Field

[0001] The invention relates to the technical field of thermal barrier coating preparation, in particular to a thickness monitoring method for electron beam physical vapor deposition thermal barrier coating. Background Art

[0002] Thermal barrier coating is a recognized technical means that can effectively reduce the surface temperature of materials, improve the thermal shock resistance of materials and extend the service life. It is widely used in important fields such as aerospace and new energy. Electron beam physical vapor deposition technology and thermal spraying technology are currently the only two processes that can mass-produce thermal barrier coatings with qualified performance. Compared with thermal spraying technology, the thermal barrier coating prepared by electron beam physical vapor deposition technology has a columnar crystal morphology, better strain tolerance and thermal shock resistance, making the coating less prone to cracking or peeling in repeated high-temperature-low-temperature service environments. Therefore, electron beam physical vapor deposition is also the only feasible technology for the preparation of thermal barrier coatings for core components of aircraft engines that are subjected to high temperature and high pressure.

[0003] Thermal barrier coatings prepared by electron beam physical vapor deposition technology are currently mainly used in high-speed moving parts such as turbine blades and guide vanes. The workpieces have extremely high aerodynamic and motion balance requirements. The slight weight changes caused by different thicknesses will directly determine whether the coating process is qualified. The thickness of the thermal barrier coating is a key indicator affecting the thermal insulation performance. Therefore, it is necessary to design the thickness of the thermal barrier coating according to the different requirements of thermal insulation effect, thermal shock resistance and motion balance in different application scenarios, and the actual thickness of the preparation is required to be consistent with the theoretical thickness. This requires the preparation process to have the ability to accurately control the coating deposition thickness.

[0004] Currently, the method commonly used to monitor coating film thickness in a vacuum environment is crystal oscillator thickness measurement. Its working principle is to monitor the film thickness through the piezoelectric effect and mass load effect of quartz crystal. The monitoring film thickness range is 0.1-2μm, and the working temperature does not exceed 150°C. In order to ensure a certain thermal protection effect, the thickness of the thermal barrier coating is generally 70-300μm. In order to enable the target gas to effectively form a columnar crystal coating on the surface of the workpiece, it is usually necessary to heat the workpiece. The heating temperature is generally 700-1200°C. This makes it impossible to use the existing vacuum film thickness monitoring method to monitor the thickness of the thermal barrier coating in the electron beam physical vapor deposition process.

[0005] The thickness of thermal barrier coatings is affected by many factors, such as target type, target consumption, workpiece curvature, electron beam power, deposition temperature, etc., and the high vacuum and high temperature process environment of electron beam physical vapor deposition makes it difficult to accurately control the thickness. Therefore, there is no technology that can accurately monitor the thickness of thermal barrier coatings during the process. The thickness of existing thermal barrier coatings is evaluated after the preparation process is completed, through destructive or non-destructive methods, or predicted through a single variable such as process time. The above methods have a time delay and only rely on a single variable such as process time. It is very easy for the thickness to fail to meet or exceed the standard, resulting in rework or scrap of the workpiece, and indirectly increasing the process cost.

[0006] Based on this, a thickness monitoring method for an electron beam physical vapor deposition thermal barrier coating is now provided, which can eliminate the drawbacks of the prior art solutions. Summary of the invention

[0007] The purpose of the present invention is to provide a thickness monitoring method for electron beam physical vapor deposition thermal barrier coatings, so as to solve the problem that the thickness of the thermal barrier coating cannot be monitored in the electron beam physical vapor deposition process environment in the background technology, and thus the coating thickness cannot be accurately controlled, and the workpiece thickness is prone to exceed or fail to meet the standard, resulting in multiple rework and increased process costs.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating comprises the following steps:

[0010] S1. Arrange the monitoring device inside the vacuum chamber and select the target material required for the deposition process;

[0011] S2. Prepare thermal barrier coating by electron beam physical vapor deposition process and obtain various parameters in the process;

[0012] S3. Setting a linear regression model by computer and calculating the thickness of the thermal barrier coating using a custom function formula and the above parameters;

[0013] S4. After obtaining the calculated value, stop the process, measure the actual thickness of the sample, and compare and analyze it with the calculated value;

[0014] The use of the thickness monitoring method of an electron beam physical vapor deposition thermal barrier coating using the above steps S1 to S4 also specifically involves a thickness monitoring device of an electron beam physical vapor deposition thermal barrier coating, including a vacuum chamber and a computer, wherein a crucible for placing a target material required for a deposition process is arranged inside the vacuum chamber, the crucible is a copper water-cooled crucible, a weighing sensor is arranged at the lower end of the crucible, and the weighing sensor is connected to the computer via a data cable, a heating device is arranged at the top of the vacuum chamber, a workpiece rotating device is installed below the heating device, a workpiece clamping device for clamping the workpiece is connected to one side of the workpiece rotating device, a vacuum device is arranged at the bottom of the vacuum chamber, and an electron beam emitting device is arranged above the vacuum device.

[0015] Furthermore, the target material is a ceramic target material of yttria-stabilized zirconia or a thermal barrier coating target material of other component systems.

[0016] Furthermore, the electron beam emitting device is configured as a direct-emission electron gun or a deflection-type electron gun with a deflection angle of 0-270°, and the power range of the electron gun is 5-60KW.

[0017] Furthermore, the target material needs to be preheated before the process preparation operation in step S2, and the preheating treatment uses a low-power electron beam.

[0018] Furthermore, the computer in step S3 calculates the thickness of the thermal barrier coating by a custom function formula, which specifically includes the following steps:

[0019] S31, a user-defined function f(x), wherein the variable x adopts the comprehensive calculated value of the electron beam process parameters, namely, power*time;

[0020] S32. Use the INTERCEPT function to establish a linear regression model. The model formula is y=INTERCEPT+B1*x+B2*x^ 2 +B3*x^ 3 , B1, B2, and B3 are all fitting coefficients;

[0021] S33, by comparing the physical and chemical properties of the actual target material with the standard target material, the physical and chemical properties include but are not limited to chemical composition, target material density, size, porosity, and determining the target material coefficient a according to the above values;

[0022] S34, determining a power coefficient b according to a power value in the electron beam process parameter;

[0023] S35, calculating function f(x)=y*a*b;

[0024] S36, determining a deposition coefficient c according to the workpiece type and the deposition temperature value;

[0025] S37, obtaining the target material consumption mass z through a weighing sensor, and transmitting the above data to a computer through a data line;

[0026] S38. Calculate h=[z / f(x)]*c to obtain the calculated thickness of the coating.

[0027] Furthermore, the time in step S31 is obtained by a timer, and the unit of the time is minute.

[0028] Furthermore, the fitting coefficient in step S32 is set to B1≥B2≥B3.

[0029] Furthermore, the value range of the target material coefficient a in step S33 is 0.80≤a≤1.2.

[0030] Furthermore, the value range of the power coefficient b in step S34 is 0.7≤b≤1.2.

[0031] Furthermore, the numerical range of the deposition coefficient c in step S36 is 0.7≤c≤1.8.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The invention discloses a method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating. Compared with the prior art, the invention can utilize a self-designed weighing device to obtain the target material consumption mass in a high vacuum and high temperature electron beam physical vapor deposition process, and combine the electron beam process parameters, the target material physicochemical coefficient, and the workpiece deposition coefficient. The thickness of the thermal barrier coating in the process is calculated through a user-defined function, which is convenient for grasping the coating thickness change in the process and achieving the effect of accurately adjusting the coating thickness, greatly improving the stability of the process and the coating quality, while avoiding the occurrence of multiple rework and defective products, greatly reducing the process cost and the unqualified rate of the thermal barrier coating prepared by the electron beam physical vapor deposition process, effectively improving the process stability and the coating quality, and having good practical application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the thickness monitoring device of the present invention;

[0035] Figure 2 It is a schematic diagram for comparing the calculated thickness according to an embodiment of the present invention with the actual thickness of a workpiece.

[0036] Notes on figure numbers: 1. vacuum chamber; 2. heating device; 3. workpiece clamping device; 4. workpiece rotating device; 5. workpiece; 6. target material; 7. crucible; 8. weighing sensor; 9. data line; 10. electron beam emitting device; 11. computer; 12. vacuum device. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0038] In this embodiment, if Figure 1-Figure 2 As shown, a method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating comprises the following steps:

[0039] S1, arranging a monitoring device inside the vacuum chamber 1, and selecting a target material 6 required for a deposition process;

[0040] S2. Prepare thermal barrier coating by electron beam physical vapor deposition process and obtain various parameters in the process;

[0041] S3, setting a linear regression model through the computer 11, and calculating the thickness of the thermal barrier coating using a custom function formula and the above parameters;

[0042] S4. After obtaining the calculated value, stop the process, measure the actual thickness of the sample, and compare and analyze it with the calculated value;

[0043] Specifically, before performing the coating deposition operation on the workpiece 5, the electron beam emitting device 10 is first cleaned to ensure that the electron beam emitting device 10 is not prone to frequent high-voltage discharge or interruption problems, thereby increasing stability. The target material 6 in the above step S1 is a ceramic target material of yttria-stabilized zirconia or a thermal barrier coating target material of other component systems. Before placing the target material 6 into the crucible 7, the target material 6 is inspected to ensure the stability of its performance. The monitoring device (not shown in the figure) is a common component in this field and is a prior art. Through the above step S4, it is possible to observe and judge whether the thickness monitoring method has reference and accuracy based on the comparison results, effectively improving the credibility of the thickness monitoring method and facilitating subsequent analysis operations;

[0044] The use of the method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating using the above steps S1 to S4 also specifically involves a thickness monitoring device for an electron beam physical vapor deposition thermal barrier coating. The principle is to use a high-energy-density electron beam to heat the material to be evaporated, i.e., the target material 6, in a crucible 7 under a high vacuum environment to make it reach a molten gasified state, and then evaporate to the surface of the workpiece 5 to condense into a coating. The thickness of the coating is monitored by a vacuum chamber 1 and a computer 11. The interior of the vacuum chamber 1 is provided with a crucible 7 for placing the target material 6 required for the deposition process. The crucible 7 is a copper water-cooled crucible. The copper water-cooled crucible is mainly used in the electron gun industry and is usually composed of a side wall and a bottom wall. The interior has a dual-path or multi-path circulating water path structure, which can effectively dissipate heat and enhance the overall strength and stability of the crucible 7. A weighing sensor 8 is provided at the lower end of the crucible 7. The weighing sensor 8 is used to obtain the initial mass of the target material 6 and the mass z of the target material consumed during the process. 8 is connected to a computer 11 through a data cable 9. The data cable 9 is a metal-armored high-temperature resistant data cable. A layer of metal protection is added to the outside of the product to prevent the inside from being damaged during transportation and installation, so as to protect the internal cables. The data cable 9 is sealed by a CF flange metal to isolate the vacuum chamber 1 from the outside world, thereby playing a sealing role. A heating device 2 is provided on the top of the vacuum chamber 1. The heating temperature is 700-1200°C, so that the target material 6 can reach a molten gasification state, and then evaporate to the surface of the workpiece 5 to condense into a coating. A workpiece rotating device 4 is installed below the heating device 2 to facilitate the rotation of the workpiece 5. A workpiece clamping device 3 for clamping the workpiece 5 is connected to one side of the workpiece rotating device 4 to facilitate the fixing of the workpiece 5. A vacuum device 12 is provided at the bottom of the vacuum chamber 1 to generate, measure and control a vacuum environment. An electron beam emitting device 10 is provided above the vacuum device 12. The electron beam emitting device 10 includes an evaporation electron gun and a preheating electron gun. The target material 6 is preheated by the preheating electron gun.

[0045] Among them Figure 1 As shown, the electron beam emitting device 10 is set as a direct electron gun, and the electron gun power range of the direct electron gun is 5 to 60KW. The electron beam emitting device 10 can also be set as a deflection type electron gun, and the deflection angle of the deflection type electron gun is 0 to 270°, and its electron gun power range is also set to 5 to 60KW, thereby increasing the stability of the coating quality.

[0046] Among them Figure 1 As shown, the target material 6 needs to be preheated before the process preparation operation in step S2. The preheating treatment uses a low-power electron beam to remove impurities or moisture on the surface of the target material 6, and can improve the temperature uniformity of the target material 6, reduce the thermal stress caused by the temperature gradient, and thus reduce the risk of cracking.

[0047] Among them Figure 1 and Figure 2As shown, the computer 11 in step S3 calculates the thickness of the thermal barrier coating by a custom function formula, which specifically includes the following steps:

[0048] S31, a user-defined function f(x), wherein the variable x adopts the comprehensive calculated value of the electron beam process parameters, namely, power*time, and the time is obtained through a timer, and the unit of time is minutes;

[0049] S32. Use the INTERCEPT function to establish a linear regression model. The model formula is y=INTERCEPT+B1*x+B2*x^ 2 +B3*x^ 3 , B1, B2, and B3 are all fitting coefficients, and the fitting coefficients are set to B1≥B2≥B3;

[0050] S33, by comparing the physical and chemical properties of the actual target material 6 with the standard target material, the physical and chemical properties include but are not limited to chemical composition, target material density, size, porosity, and determining the target material coefficient a according to the above values, and the value range of the target material coefficient a is 0.80≤a≤1.2;

[0051] Specifically, this embodiment selects 8wt% yttria-stabilized zirconia targets as thermal barrier coating targets, the number of which is set to 10, and the target size is Target density is 3.9g / cm^ 3 , the target porosity is 5-8%, and the above data are compared with the physical and chemical properties of the standard target to determine the target coefficient a = 0.90, which is within the numerical range;

[0052] S34, determining a power coefficient b according to a power value in the electron beam process parameter, wherein the power coefficient b has a value range of 0.7≤b≤1.2;

[0053] Specifically, in this embodiment, the electron beam power is selected as 40KW, and the power coefficient b is determined to be 1.0, and the power coefficient b is within the numerical range;

[0054] S35, calculating function f(x)=y*a*b;

[0055] S36, determining a deposition coefficient c according to the type of workpiece and the deposition temperature value, wherein the deposition coefficient c has a value range of 0.7≤c≤1.8;

[0056] Specifically, in this embodiment, a flat plate sample with a size of 25x40x3mm and a material of GH3030 is selected, and the substrate temperature is 700-750°C, and the deposition coefficient is determined to be c=0.97, and the deposition coefficient c is within the numerical range;

[0057] S37, obtaining the target material consumption mass z through the weighing sensor 8, and transmitting the above data to the computer 11 through the data line 9;

[0058] S38, calculate h=[z / f(x)]*c, and obtain the calculated thickness of the coating;

[0059] Specifically, the calculated thickness of the coating is obtained according to the above steps. After the calculated value is obtained, the process is stopped, the sample is taken out, and the coating thickness is measured using a cutting machine, a metallographic mounting machine and a microscope to obtain the actual thickness of the workpiece 5. The thickness comparison results are shown in Table 1. It can be seen from the data that the absolute value of the thickness error between the calculated coating thickness and the actual thickness of the workpiece 5 is between 0.07 and 2.00 μm, and its numerical range is small, which effectively improves the credibility of the thickness monitoring method, facilitates the grasp of the coating thickness change in the process, achieves the effect of accurately adjusting the coating thickness, effectively improves the process stability and coating quality, and has a good practical application prospect.

[0060] Table 1

[0061] frequency Example Calculation Thickness Actual thickness of workpiece Absolute value of thickness error 1 43.58408 44.1 0.51592 2 97.17603 97.1 0.07603 3 104.58738 104.3 0.28738 4 106.01161 105.4 0.61161 5 106.66396 105.9 0.76396 6 112.6374 114.6 1.9626 7 115.39856 116.3 0.90144 8 117.03772 116.6 0.43772 9 117.03772 117.5 0.46228 10 121.11548 120.9 0.21548

[0062] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating, characterized in that: The following steps are involved: S1, arranging a monitoring device inside a vacuum chamber (1), and selecting a target material (6) required for a deposition process; S2. Prepare thermal barrier coating by electron beam physical vapor deposition process and obtain various parameters in the process; S3, setting a linear regression model through a computer (11), and calculating the thickness of the thermal barrier coating using a custom function formula and the above parameters; S4. After obtaining the calculated value, stop the process, measure the actual thickness of the sample, and compare and analyze it with the calculated value; The use of a method for monitoring the thickness of a thermal barrier coating by electron beam physical vapor deposition using the above steps S1 to S4 also specifically involves a device for monitoring the thickness of a thermal barrier coating by electron beam physical vapor deposition, comprising a vacuum chamber (1) and a computer (11); a crucible (7) for placing a target material (6) required for a deposition process is arranged inside the vacuum chamber (1); the crucible (7) is a copper water-cooled crucible; a weighing sensor (8) is arranged at the lower end of the crucible (7); the weighing sensor (8) is connected to the computer (11) via a data line (9); a heating device (2) is arranged at the top of the vacuum chamber (1); a workpiece rotating device (4) is installed below the heating device (2); a workpiece clamping device (3) for clamping a workpiece (5) is connected to one side of the workpiece rotating device (4); a vacuum device (12) is arranged at the bottom of the vacuum chamber (1); an electron beam emitting device (10) is arranged above the vacuum device (12).

2. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 1, characterized in that: The target material (6) is a ceramic target material of yttria-stabilized zirconia or a thermal barrier coating target material of other component systems.

3. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 1, characterized in that: The electron beam emitting device (10) is configured as a direct-emission electron gun or a deflection-type electron gun with a deflection angle of 0-270°, and the power range of the electron gun is 5-60 kW.

4. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 1, characterized in that: Before the process preparation operation in step S2, the target material (6) needs to be preheated, and the preheating treatment uses a low-power electron beam.

5. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 1, characterized in that: The computer (11) in step S3 calculates the thickness of the thermal barrier coating by a self-defined function formula, which specifically includes the following steps: S31, a user-defined function f(x), wherein the variable x adopts the comprehensive calculated value of the electron beam process parameters, namely, power*time; S32. Use the INTERCEPT function to establish a linear regression model. The model formula is y=INTERCEPT+B1*x+B2*x^ 2 +B3*x^ 3 , B1, B2, and B3 are all fitting coefficients; S33, by comparing the physical and chemical properties of the actual target material (6) with those of the standard target material, the physical and chemical properties including but not limited to chemical composition, target material density, size, and porosity, and determining the target material coefficient a according to the above values; S34, determining a power coefficient b according to a power value in the electron beam process parameter; S35, calculating function f(x)=y*a*b; S36, determining a deposition coefficient c according to the workpiece type and the deposition temperature value; S37, obtaining the target material consumption mass z through the weighing sensor (8), and transmitting the above data to the computer (11) through the data line (9); S38. Calculate h=[z / f(x)]*c to obtain the calculated thickness of the coating.

6. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 5, characterized in that: The time in step S31 is obtained by a timer, and the unit of the time is minute.

7. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 5, characterized in that: The fitting coefficient in step S32 is set to B1≥B2≥B3.

8. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 5, characterized in that: The value range of the target material coefficient a in the step S33 is 0.80≤a≤1.

2.

9. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 5, characterized in that: The value range of the power coefficient b in step S34 is 0.7≤b≤1.

2.

10. The method for monitoring the thickness of an electron beam physical vapor deposition thermal barrier coating according to claim 5, characterized in that: The numerical range of the deposition coefficient c in step S36 is 0.7≤c≤1.8.

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