CN114086112B

CN114086112B - Method for uniformly preheating complex-surface workpiece for PS-PVD (plasma physical vapor deposition)

Info

Publication number: CN114086112B
Application number: CN202210076235.3A
Authority: CN
Inventors: 郭洪波; 郭谦; 何雯婷; 彭徽; 魏亮亮
Original assignee: Beihang University
Current assignee: Beihang University
Priority date: 2022-01-24
Filing date: 2022-01-24
Publication date: 2022-03-25
Anticipated expiration: 2042-01-24
Also published as: CN114086112A

Abstract

The invention discloses a uniform preheating method of a complex-surface workpiece for PS-PVD (plasma physical vapor deposition), which aims to solve the technical problems that the complex-surface workpiece is difficult to uniformly preheat by adopting high-energy beam jet flow and is difficult to operate and high in cost in engineering practice by adopting an external heating body for heating. The surface in-situ uniform heating of workpieces with complex shapes and different sizes can be realized before spraying, the uniformity of the coating on the surface of the workpiece is improved, and the production cost is greatly reduced.

Description

Method for uniformly preheating complex-surface workpiece for PS-PVD (plasma physical vapor deposition)

Technical Field

The invention belongs to the technical field of plasma physical vapor deposition preparation of thermal barrier coatings, and particularly relates to a uniform preheating method of a complex-profile workpiece for PS-PVD.

Background

Thermal barrier coatings (TBCs for short) are a high-temperature thermal protection technology which adopts a high-temperature-resistant, low-thermal-conductivity and corrosion-resistant ceramic material to be compounded with an alloy in a coating mode so as to reduce the surface temperature of the alloy in a high-temperature environment. The TBCs are used on the engine blades, so that the working temperature of the engine can be obviously improved, the working efficiency and the thrust of the engine are improved, and the working temperature of alloy of the turbine blades can be reduced by 30-150 ℃, so that the service life and the reliability of the engine are greatly improved.

The development of TBCs is driven by the development of manufacturing techniques, PS being the most widely used method for preparing TBCs, and coatings prepared generally having a layered structure with an effective interlayer bonding area of less than 40%. Because of their structural characteristics, TBCs made of PS generally have good thermal insulation properties, but poor thermal shock resistance. Muehlberger et al invented low pressure plasma spraying on the basis of atmospheric plasma spraying technology, and compared with the conventional atmospheric plasma spraying, the plasma jet was elongated at a lower vacuum, the jet velocity was greatly increased, and the spray powder obtained from the plasma jet at a higher velocity, so that the prepared coating had better density and binding force. On the basis of the above, the working pressure is further reduced (about 200 Pa), the spraying power is increased (80-100 kW), the plasma jet is further expanded and thickened, the temperature of the plasma is further increased (about 15550K can be reached), and the injected material can be evaporated into a gas phase. The characteristics of the coating formed by vapor deposition are closer to those of the coating prepared by electron beam physical vapor deposition, so that the rapid deposition of large-area compact metal or ceramic films, namely the plasma physical vapor deposition technology, can be realized. The vapor deposition forms a columnar or quasi-columnar structure coating, so that the thermal stress can be greatly reduced in the cold and hot cycle service process, and the service life of the coating is prolonged.

The temperature of the substrate is of great significance to the growth of the vapor deposition coating. The PS-PVD deposition vapor phase coating comprises three processes of evaporation, deposition and diffusion. The evaporation process is a process of heating and evaporating ceramic powder into gas phase atoms, the deposition process is a process of recombining free gaseous atoms or ions into a solid material to be deposited on a substrate, and the diffusion process is a process of diffusing and recombining material atoms against an energy barrier due to the requirement of reducing the internal energy of the material after the material is deposited on the substrate. At low substrate temperatures (less than 500 c), the deposition efficiency of the coating is low and gas phase atoms condense directly into particles that accumulate on the substrate surface, resulting in a low bond strength between the coating and the substrate. When the temperature of the substrate is 700-900 ℃, the deposition and the surface diffusion compete with each other, and the growth of the coating is mainly influenced by the shadow effect and grows into coarse conical crystals; when the temperature of the substrate is higher (more than 1200 ℃), the surface diffusion plays a main role at this time to form columnar crystals with preferred orientation, a certain gap exists between the columns, and the pores between the columns can penetrate to the surface of the coating along the surface of the substrate.

At present, two preheating modes are generally adopted in the process of preparing a coating by plasma physical vapor deposition, one mode is to directly preheat by adopting plasma jet, however, the preheating mode is difficult to realize uniformity, particularly for a complex-profile workpiece, because the wall thickness difference of each part of the complex workpiece is very large, the temperature difference of different parts of the same workpiece can reach 50-100 ℃ in the heating process, the thin-wall part of a part is very easy to overheat in the preheating process to cause the damage of the workpiece, and the temperature of the clamping end of the workpiece can not meet the spraying requirement. The other method is to adopt an external heating body such as a heating furnace for preheating, is limited by the size of a furnace body, has high preheating cost for large-scale workpieces with complex profiles, and is difficult to operate in engineering practice when the heating body heats the workpieces in a high vacuum environment.

Therefore, in order to solve the above problems, it is desirable to develop a method for uniformly preheating a low-cost complex-profile workpiece suitable for plasma physical vapor deposition (PS-PVD).

Disclosure of Invention

Based on the defects of the prior art, the invention provides a uniform preheating method for a PS-PVD workpiece with a low cost and a complex profile. According to the invention, a preheating mechanism is arranged on a sliding table of the original PS-PVD equipment, as shown in figure 1, the preheating mechanism is arranged on the sliding table, the distance between the preheating mechanism and a spray gun is controlled to be 100-2000mm, a preheating rotor arc is formed between the spray gun and an anode of the preheating mechanism, and a workpiece is subjected to radiation heating through the rotor arc and an anode plate.

The complete technical scheme of the invention comprises the following steps:

a PS-PVD complex surface workpiece uniform preheating method is characterized in that a preheating device for PS-PVD is adopted for preheating, and the device comprises a plasma spray gun 1, a vacuum tank 2, a slide rail 3, a preheating mechanism 5 and a workpiece 6;

the plasma spray gun 1, the preheating mechanism 5, the sliding rail 3 and the workpiece 6 are all arranged in a vacuum tank, and the preheating mechanism 5 is arranged on the sliding rail 3;

the preheating mechanism 5 comprises a first anode plate 7 positioned on the top of the workpiece 6, and a second anode plate 9 and a third anode plate 14 positioned on two sides of the workpiece 6;

the preheating mechanism 5 comprises a base 11, the workpiece 6 is arranged on a ceramic insulating table 12 on the base 11, the ceramic insulating table 12 can drive the workpiece 6 to rotate,

a first ceramic insulating block 10 is arranged between the second anode plate 9 and the base 11, and a second ceramic insulating block 13 is arranged between the third anode plate 14 and the base 11;

a first ceramic insulating support 8 is arranged between the first anode plate 7 and the second anode plate 9, and a second ceramic insulating support 15 is arranged between the first anode plate 7 and the third anode plate 14;

during preheating, an arc is initiated between the plasma torch and the first anode plate 7, the second anode plate 9 and the third anode plate 14, and the workpiece is preheated by the rotor arc 4 and the anode plates.

The material of the first anode plate 7, the second anode plate 9 and the third anode plate 14 is one of high-temperature alloy, stainless steel and graphite.

The thickness of the first anode plate 7, the second anode plate 9 and the third anode plate 14 is 5-10mm, the first anode plate 7 is arranged on the upper part of a workpiece, and the included angle between the installation angle and the horizontal plane is 30-45 degrees; the installation positions of the second anode plate 9 and the third anode plate 14 are symmetrically distributed along the central axis of the tool, the included angle between the installation positions and the central axis is 45-60 degrees, the heights of the second anode plate 9 and the third anode plate 14 are consistent, and the heights are set according to the size of a workpiece.

The first ceramic insulating support 8 and the second ceramic insulating support 15 are triangular hollow ceramic insulating supports.

The device also comprises an infrared temperature measuring mechanism, and when the device is preheated, the heating power, the distance and the rotation mode of the ceramic insulating table are adjusted according to a real-time temperature measuring result obtained by the infrared temperature measuring mechanism.

When preheating, the distance between the plasma spray gun 1 and the preheating mechanism 5 is adjusted by utilizing the slide rail 3 according to the size and the shape of the workpiece.

The first ceramic insulating support 8, the second ceramic insulating support 15, the first ceramic insulating block 10, the second ceramic insulating block 13 and the ceramic insulating table 12 are made of non-conductive oxide ceramics.

The preheating mechanism 5 further comprises a ceramic insulation wire column 16, and three independent cables are respectively connected with the first anode plate 7, the second anode plate 9 and the third anode plate 14 through the ceramic insulation wire column 16.

The heating power of the plasma spray gun 1 is 3kW-48 kW.

The specific preheating step comprises:

(1) setting workpiece preheating program parameters, wherein the parameters comprise rotor-rotor arc current, spray gun working gas flow, preheating distance and workpiece rotation mode;

(2) fixing the workpiece on a ceramic insulating table in a vacuum tank;

(3) closing the vacuum tank, and vacuumizing to ensure that the pressure of the vacuum tank is lower than 0.08 mbar;

(4) filling argon as a protective gas into the vacuum tank to ensure that the pressure of the vacuum tank reaches 130 mbar;

(5) checking the preheating program parameters, opening a working gas valve, striking an arc between the plasma spray gun and the first anode plate, the second anode plate and the third anode plate, gradually adjusting the gas flow to the specified gas flow after the electric arc is stabilized, gradually adjusting the current between transferred ion arcs to be 600A and the voltage to be 30-80V;

(6) in the preheating process, an infrared temperature measuring device is adopted to measure the temperature of different positions of the workpiece outside an observation window, and the temperature is adjusted according to the heating power, the distance and the rotation mode of the ceramic insulating table;

(7) when the coating is preheated to the spraying temperature, an ion arc is initiated, and the coating preparation is started.

Compared with the prior art, the invention has the following advantages:

1. the preheating method is simple, external equipment is not needed, in-situ uniform heating of the surface of the workpiece can be realized before spraying through multi-rotor arc multi-angle radiation heating, the uniformity of the coating on the surface of the workpiece is improved, and the production cost is greatly reduced.

2. The anode plate used by the invention can be customized according to the size of the workpiece, the heatable workpiece is not limited by the size, and the uniform preheating of the large-size complex workpiece can be realized.

3. The multi-rotor moving-arc can continuously heat the workpiece in the plasma physical vapor deposition process, and is favorable for maintaining the temperature of the workpiece in the spraying process.

4. The multi-rotor moving-ion arc is beneficial to stabilizing jet flow, increasing jet flow temperature and gas phase content in the jet flow in the plasma physical vapor deposition process, and is beneficial to vapor coating deposition.

Drawings

FIG. 1 is a schematic view showing the overall installation of a preheating apparatus for PS-PVD according to the present invention.

FIG. 2 is a front view of the preheating mechanism of the present invention.

FIG. 3 is a schematic side view of the preheating mechanism according to the present invention.

In the figure: 1-a plasma spray gun, 2-a vacuum tank, 3-a slide rail, 4-a rotor arc, 5-a preheating mechanism, 6-a workpiece, 7-a first anode plate, 8-a first ceramic insulating support, 9-a second anode plate, 10-a first ceramic insulating block, 11-a base, 12-a ceramic insulating table, 13-a second ceramic insulating block, 14-a third anode plate, 15-a second ceramic insulating support and 16-a ceramic insulating wire column.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only illustrative and are not intended to limit the present application.

As shown in figure 1, the integral device of the invention comprises a plasma spray gun 1, a vacuum tank 2, a slide rail 3, a preheating mechanism 5 and a workpiece 6.

The plasma spray gun 1, the preheating mechanism 5, the sliding rail 3 and the workpiece 6 are all arranged in the vacuum tank. The plasma spray gun 1 is positioned on one side of the vacuum tank, the preheating mechanism 5 is arranged on the slide rail 3, and the workpiece 6 is positioned on the preheating mechanism 5.

The preheating mechanism 5 of the present invention has a specific structure as shown in fig. 2, three anode plates are arranged around the workpiece, the anode plates can be made of high temperature alloy, stainless steel, graphite, etc., and include a first anode plate 7 positioned on the top of the workpiece 6, and a second anode plate 9 and a third anode plate 14 positioned on both sides of the workpiece 6. Three anode plates are used for generating a rotor arc 4 between the plasma torch and preheating the workpiece by using the rotor arc 4.

Compared with the prior art, the method has the advantages that the plasma jet is adopted to directly preheat or an external preheating furnace is adopted to preheat. The preheating method of the invention adopts multi-rotor arc heating, thus realizing in-situ uniform heating of the surface of the workpiece before spraying. Meanwhile, in the design of transferring ion arc, a plurality of anode plates are adopted to carry out multi-angle radiation heating, and the specific structure is as follows: the thickness of the anode plate is 5-10mm, wherein the installation positions of the second anode plate 9 and the third anode plate 14 are symmetrically distributed along the central axis of the tool, and the included angle between the installation positions and the central axis is 45-60 degrees. The heights of the second anode plate 9 and the third anode plate 14 are consistent, the heights are set according to the sizes of the workpieces, preferably 10% -15% higher than the maximum height of the workpieces, and the lengths of the second anode plate 9 and the third anode plate 14 are more than 15% -20% of the maximum width of the workpieces so as to ensure that transferred ion arcs generating enough radiation range can preheat the workpieces 6. A strip-shaped first ceramic insulating block 10 is arranged between the second anode plate 9 and the base 11, and a strip-shaped second ceramic insulating block 13 is arranged between the third anode plate 14 and the base 11.

A first ceramic insulating support 8 is arranged between the first anode plate 7 and the second anode plate 9, a second ceramic insulating support 15 is arranged between the first anode plate 7 and the third anode plate 14, the first ceramic insulating support 8 and the second ceramic insulating support 15 are triangular hollow insulating supports, the triangular shape of the hollow insulating supports ensures that the included angle between the first anode plate 7 and the horizontal plane is 30-45 degrees, and the hollow structural design mode of the insulating supports ensures that most rotor arcs can smoothly pass through the supports to reach the surface of a workpiece, so that the heating efficiency is improved. The above design substantially ensures that the three rotating rotor arcs cover the entire surface of the workpiece 6, and the coverage of the rotating rotor arcs are substantially complementary and overlap less, avoiding under-or over-heating of a portion of the workpiece to ensure uniformity of heating.

Meanwhile, in the experimental process, the problem of uneven heating can be effectively avoided to a certain extent by adopting the design, but the heating power distribution of each rotor arc at each position in space has certain unevenness. Therefore, in order to further optimize the heating mode, the invention provides that the workpiece 6 is arranged on the ceramic insulating table 12 on the base 11, the ceramic insulating table can drive the workpiece 6 to rotate freely (the rotating speed is 0-30 rpm), and the design has two using modes, namely, the ceramic insulating table can be matched with an infrared temperature measuring mechanism for use, and can be used for certain workpieces (such as blades) with complex shapes and large wall thickness difference at each position, if the temperature of certain parts with large wall thickness is found to be low in the preheating process, the ceramic insulating table can be used for rotating for a certain angle, so that the parts with large wall thickness of the workpiece are exposed to the regions with high heating power, and the heating efficiency of the parts is improved. Secondly, for some workpieces with regular shapes, in order to ensure the heating power of each part to be uniform, a mode that the workpiece rotates all the time can be adopted, so that each part of the workpiece can be heated uniformly.

Further, the preheating mechanism 5 is mounted on the slide rail 3, the distance between the preheating mechanism 5 and the plasma spray gun 1 can be adjusted according to the specific situation of the workpiece in the preheating process, and if the workpiece with larger size needs larger heating power, the preheating mechanism 5 can move on the slide rail 3, so that the distance between the plasma spray gun 1 and the workpiece is increased to increase the voltage, and the heating power is improved. And is matched with the rotatable ceramic insulating table 12 to realize the adjustment of multiple degrees of freedom, and is suitable for preheating workpieces with various sizes and complex shapes.

In a preferred embodiment, the horizontal distance from the rotating outer circumference of the workpiece to the second anode plate and the third anode plate is 5-10 cm, and the vertical distance from the highest point of the workpiece to the first anode plate is kept at 5-10 cm. The first anode plate is arranged on the upper part of the workpiece, and the included angle between the installation angle and the horizontal plane is 30-45 degrees.

In a preferred embodiment, the insulating support, the insulating block and the insulating table are all non-conductive oxide ceramics, such as alumina and the like. Three separate cables are connected to the three anode plates by ceramic insulated posts 16 to provide power to the anode plates, as shown in figure 3.

In a preferred embodiment, the heating power of the plasma torch 1 is 3kW to 48 kW.

The practical operation steps of preheating the workpiece by using the device comprise:

1. setting a workpiece preheating program (including transferred ion arc current, flow of working gas of a spray gun, preheating distance and a workpiece rotating mode);

2. fixing the workpiece on a ceramic insulating table in a vacuum tank;

3. closing the vacuum tank, and vacuumizing to ensure that the pressure of the vacuum tank is lower than 0.08 mbar;

4. opening a tank filling gas Ar gas switch, and filling protective gas into the vacuum tank until the pressure reaches 130 mbar;

5. checking the preheating parameters, opening a working gas valve, striking an arc between the plasma spray gun and the anode plate, gradually adjusting the gas flow to the specified gas flow (Ar 20-40 SLPM) after the arc is stabilized, gradually adjusting the current between transferred ion arcs to be (100-600A), and the voltage to be 30-80V;

6. in the preheating process, an infrared temperature measuring device is adopted to measure the temperature of different positions of the workpiece outside an observation window, and whether the ceramic insulating table needs to be adjusted to rotate or not is judged according to the temperature measurement result;

7. when the coating is preheated to the spraying temperature, an ion arc is initiated, and the coating preparation is started.

Example 1:

a duplex blade of an aeroengine of a certain model is prepared into a thermal barrier coating by PS-PVD and preheated by a multi-rotor arc. The method comprises the following specific steps:

the method comprises the following steps: setting a workpiece preheating program (transfer ion arc current 200A, spray gun working gas flow 30 SLAM, preheating distance 1200 mm, workpiece rotation speed 20 rpm);

step two: fixing the workpiece on a ceramic insulating table in a vacuum tank;

step three: closing the vacuum chamber, and vacuumizing to ensure that the pressure in the vacuum chamber is lower than 0.08 mbar;

step four: opening a tank filling gas Ar gas switch, and filling protective gas into the tank until the pressure reaches 130 mbar;

step five: checking the preheating parameters, opening a working gas valve, striking an arc between a spray gun and an anode plate, gradually adjusting the gas flow to the specified gas flow (Ar: 30 SLPM) after the arc is stabilized, gradually adjusting the current between transferred ion arcs to be 200A and the voltage to be 35V;

step six: when the coating is preheated to the spraying temperature, an ion arc is initiated, and the coating preparation is started.

After preheating for 10min, an infrared temperature measuring device is adopted to measure the temperature of the upper edge plate of the blade outside the observation window to be 880 ℃, the temperature of the lower edge plate of the blade to be 865 ℃, the temperature of the middle position of the blade body to be 870 ℃, the temperature difference to be less than 20 ℃, and the temperature of the preheated blade is uniform, thereby meeting the spraying requirement.

The above applications are only some embodiments of the present application. It will be apparent to those skilled in the art that various changes and modifications can be made without departing from the inventive concept herein, and it is intended to cover all such modifications and variations as fall within the scope of the invention.

Claims

1. A uniform preheating method of a complex-surface workpiece for PS-PVD is characterized in that a preheating device for PS-PVD is adopted for preheating, and the device comprises a plasma spray gun (1), a vacuum tank (2), a slide rail (3), a preheating mechanism (5) and a workpiece (6);

the plasma spray gun (1), the preheating mechanism (5), the sliding rail (3) and the workpiece (6) are all arranged in a vacuum tank, and the preheating mechanism (5) is arranged on the sliding rail (3);

the preheating mechanism (5) comprises a first anode plate (7) positioned at the top of the workpiece (6), and a second anode plate (9) and a third anode plate (14) positioned at two sides of the workpiece (6);

the preheating mechanism (5) comprises a base (11), the workpiece (6) is arranged on a ceramic insulating table (12) on the base (11), the ceramic insulating table (12) can drive the workpiece (6) to rotate,

a first ceramic insulating block (10) is arranged between the second anode plate (9) and the base (11), and a second ceramic insulating block (13) is arranged between the third anode plate (14) and the base (11);

a first ceramic insulating support (8) is arranged between the first anode plate (7) and the second anode plate (9), and a second ceramic insulating support (15) is arranged between the first anode plate (7) and the third anode plate (14);

during preheating, arc striking is carried out between the plasma spray gun and the first anode plate (7), the second anode plate (9) and the third anode plate (14), and the workpiece is preheated by the rotor arc and the anode plates.

2. The method for uniformly preheating the complex-profile workpiece for PS-PVD according to claim 1, wherein the material of the first anode plate (7), the second anode plate (9) and the third anode plate (14) is one of high-temperature alloy, stainless steel and graphite.

3. The method for uniformly preheating the complex-profile workpiece for PS-PVD according to claim 1, wherein the thickness of the first anode plate (7), the second anode plate (9) and the third anode plate (14) is 5-10mm, the first anode plate (7) is arranged on the upper part of the workpiece, and the included angle between the installation angle and the horizontal plane is 30-45 degrees; the installation positions of the second anode plate (9) and the third anode plate (14) are symmetrically distributed along the central axis of the tool, the included angle between the installation positions and the central axis is 45-60 degrees, the heights of the second anode plate (9) and the third anode plate (14) are consistent, and the heights are set according to the size of a workpiece.

4. The method for uniformly preheating a complex-profile workpiece for PS-PVD according to claim 1, wherein the first ceramic insulating support (8) and the second ceramic insulating support (15) are triangular hollow ceramic insulating supports.

5. The method as claimed in claim 1, wherein the apparatus further comprises an infrared temperature measurement mechanism, and the heating power, distance and rotation mode of the ceramic insulation table are adjusted according to real-time temperature measurement results obtained by the infrared temperature measurement mechanism during preheating.

6. The method for uniformly preheating the complex-profile workpiece for PS-PVD according to claim 1, wherein the distance from the plasma torch (1) to the preheating mechanism (5) is adjusted by the slide rail (3) according to the size and shape of the workpiece during preheating.

7. The method for uniformly preheating the complex-profile workpiece for PS-PVD according to claim 1, wherein the first ceramic insulating support (8), the second ceramic insulating support (15), the first ceramic insulating block (10), the second ceramic insulating block (13) and the ceramic insulating table (12) are made of non-conductive oxide ceramics.

8. A method for uniformly preheating a complex-profile workpiece for PS-PVD according to claim 1, wherein the preheating mechanism (5) further comprises ceramic insulating posts (16), and three independent cables are respectively connected to the first anode plate (7), the second anode plate (9) and the third anode plate (14) through the ceramic insulating posts (16).

9. A method for uniformly preheating a complex-profile workpiece for PS-PVD according to claim 1, wherein the plasma torch (1) has a heating power of 3kW to 48 kW.

10. The method for uniformly preheating the complex-profile workpiece for PS-PVD according to claim 1, wherein the specific preheating step comprises:

(2) fixing the workpiece on a ceramic insulating table in a vacuum tank;