JPH04201075A - Thermal spray coating manufacturing method - Google Patents

Abstract

PURPOSE:To better the mechanical biting of a base material and film, to improve an adhesive force and to present the film from peeling off by imparting unevenness in spots on the base material surface at blasting time. CONSTITUTION:The base material(for instance graphite) 5 surface is covered by a porous member 7, the base material 1 surface is then ground by a fine particle G having passed thru the hole 10 of the porous member 7 with the fine particle (Al2O3 powder) G being blown, and a large uneven face 11 is formed. Thereafter, films 8, 9 are formed with the powder in a molten or semi- molten state being thermally sprayed on the surface.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of forming a thermal spray coating on a base material,
In particular, the present invention relates to a blasting method for increasing the surface roughness of a base material in order to increase the adhesion between the sprayed coating and the base material, a method for producing a sprayed coating, and an adhesive laminated member.

[Conventional technology]

Plasma spraying is a surface treatment method that forms a film by spraying molten or semi-molten powder onto the surface of a base material using a heat source, and is used for turbine blades, automobile engine parts, and the like.

When forming a film on the surface of the base material using plasma irradiation method,
Usually, the surface is roughened in advance to improve the mechanical bond between the film and the base material and to increase adhesion.

As a method for surface roughening, the surface of the base material is (1) blasted with powder (Japanese Patent Laid-Open No. 62-18226
1), (2) a method of forming grooves by machining (Japanese Patent Application Laid-Open No. 60-230975), and (3) a method of forming corrosion grooves with a corrosive liquid (Japanese Patent Application Laid-Open No. 60-5015).
No. 7) has been conventionally implemented.

[Problem to be solved by the invention]

Improving the adhesion between the thermal spray coating and the base material is essential to improving the reliability of the coating. However, in the conventional blasting method, it is not possible to increase the surface roughness by increasing the unevenness of the surface in order to uniformly scrape off the surface of the base material, and it is not possible to improve the adhesion between the film and the base material. To deal with this, methods have been considered to increase the roughness by creating grooves by machining or by etching with corrosive liquid. However, these methods are difficult to apply to materials that are difficult to process and hygroscopic, such as graphite.

The purpose of the present invention is to solve the above-mentioned problems by creating irregularities on the surface of a base material that can enhance the anchoring effect of the sprayed coating on the base material by just blasting, thereby forming a sprayed coating with high adhesion. The object of the present invention is to provide a blasting method, a method for producing a thermal spray coating, and a close-contact laminated member.

[Means to solve the problem]

In order to achieve the above object, the present invention includes the steps of: covering the surface of the base material with a porous member; and spraying fine particles and scraping the surface of the base material with the fine particles that have passed through the holes of the porous member. This is a blasting method characterized by the following.

The present invention also includes a step of covering the surface of the base material with a perforated member;
The method includes the steps of: spraying fine particles and scraping the surface of the base material with the fine particles passing through the holes of the perforated member; and spraying molten or semi-molten powder onto the surface to form a film. This is a characteristic method for producing thermal spray coatings.

The present invention also provides a step of spraying fine particles onto the substrate surface to form a slightly uneven surface, a step of covering the slightly uneven surface with a perforated member, and a step of spraying the fine particles to pass through the holes of the perforated member. A method for producing a thermal spray coating, comprising the steps of: forming a large uneven surface by scraping the small uneven surface with fine particles; and forming a coating by spraying molten or semi-molten powder onto the surface. It is. Here, the particle size of the fine particles is preferably the same as or smaller than the pore size of the porous member. Further, the perforated member is preferably a perforated flat plate or a wire mesh.

Here, it is preferable to repeat the process before forming the thermal spray coating multiple times.

The present invention also provides a close-contact laminated member comprising a base and a thermal sprayed coating that is in close contact with the surface of the base material, in which each member is recessed and zero provided on the contact surface between the base and the thermal sprayed coating. It is characterized by being provided with a large uneven surface and a small uneven surface formed on the large uneven surface.

[Effect]

The adhesion between the base material and the thermal sprayed coating is mainly achieved by the mechanical biting effect (anchoring effect), and it is known that roughening the surface of the base material is effective in improving the adhesion. It is being In the present invention, this surface roughening was performed by the method shown below.

After covering the base material with a perforated member such as a flat plate with multiple holes or a wire mesh, recesses are formed on the surface by blasting from the outside and scraping off only the portions located in the holes or the portions located in the mesh. This is a method of forming. In addition, after blasting the entire surface of the base material in advance, the surface of the base material is covered with a flat plate or wire mesh having multiple holes, and then blasting is performed again from the outside to the areas located in the holes or in the mesh. A recess is formed on the surface by scraping off the chisel. moreover,
This is a method in which the above blasting method is performed multiple times to form recesses on the surface of the base material.

Next, by spraying molten or semi-molten powder onto the base material having the recesses formed by the method described above to form a thermal spray coating, a large anchoring effect is obtained, and the base material and the coating are bonded together. Improves adhesion.

〔Example〕

The present invention will be explained in detail below.

FIG. 2 shows a method of forming a thermal spray coating according to the present invention when graphite is used as the base material. FIG. 3 shows the moving path of the tip of the blast gun used to roughen the surface by blasting the base material.

First, the blasting method will be explained.

Base material is graphite 5 (diameter: 20m, thickness 25mm)
), and the pressure from the tip of the blast gun 6 is 2 kg/a+?
AQ20. with compressed air. Powder (#60') is sprayed onto the surface of the base material to blast the entire surface of the base material to form a rough surface, that is, a slightly uneven surface 4. At this time, the distance between the tip of the blast gun 6 and the base material 5 was approximately 70 m1, and the blast gun moving speed was 2000 m/akin. Further, as shown in FIG. 3, the pitch P, which is the width of the path along which the tip of the blast gun moves in parallel, was approximately 7 m in this embodiment, and the number of passes was one.

The number of passes was determined as one pass when the tip of the blast gun moved from B to E in the movement path of the blast gun shown in FIG.

Next, the surface of the graphite material 5 is covered with a perforated flat plate 7 made of fluororesin (trade name: Teflon) as shown in FIG. In this case, the hole diameter (D,) is
A plurality of 2 m holes 10 are provided. After that, use AQ20 with a blast gun under the same conditions as above. By spraying powder and scraping off the surface of the base material located below the plurality of holes 10 provided in the perforated flat plate 7, the recesses 3 shown in FIG. 2 are formed.
, and a large uneven surface 11 was formed as a whole.

In this case, the depth H of the recess 3 can be changed by changing the number of passes of blasting. This time, the number of passes is 2.
, 4 and 6 test pieces were prepared. Furthermore, a perforated flat plate with a smaller hole diameter D2 of φ11IW11 was produced,
A test piece was also prepared in which the surface of the base material was covered and then subjected to blasting treatment. Table 1 shows the number of passes and blasting depth of these test pieces produced according to the present invention.

Table 1 As mentioned above, the feature of the present invention is that the entire surface of the base material is roughened by blasting in advance, and then it is covered with a perforated flat plate having a plurality of pores and then blasted again. This makes it possible to further form concave portions on the rough surface of the base material located in the pores, thereby increasing the roughness. The results in Table 1 show this. That is, when blasting was performed by covering the base material with a perforated flat plate with a hole diameter of 2 m, blasting depths of 45.6'O and 80 μm were obtained when the number of passes was 2.4 and 6, respectively. Further, when blasting was performed by covering the base material with a perforated flat plate with a hole diameter of 1 m+, a blasting depth of 50 μm was obtained when the number of passes was two.

Next, using a separately prepared plasma spraying device, high melting point metal powder was first sprayed onto the rough surfaces of the four types of graphite base materials shown in Table 1 prepared by the method described above.
After forming the high melting point metal layer 8 having a thickness of 0 μm, high melting point oxide ceramic powder was sprayed on the upper surface of the high melting point metal layer to form a high melting point oxide ceramic layer 9 having a thickness of about 100 μm.

Here, for comparison, no perforated plate was used, the entire area of the base material was subjected to a pressure of 2 kg/d, a distance between the blast gun and the base material of approximately 70 m, and a moving speed of the blast gun of approximately 2000 m.
Prepare graphite that has been blasted (conventional method) under the conditions of m/11in, 1 pass, and a pitch of approximately 7mm+.
After forming a high melting point metal layer of about 100 μm by plasma spraying, a test piece with a high melting point oxide ceramic layer of about 100 μm formed on the surface was prepared, and was subjected to the adhesion test described below together with the four types of test pieces mentioned above. I tried it on.

Next, in order to clarify the effects of the present invention, the adhesion between the base material and the thermally sprayed coating was investigated, and the results will be described.

Here, as a method for measuring the adhesion between the sprayed coating and the base material, the adhesion test method described in JISH8666 was followed. The test conditions in this case were that the test piece temperature was room temperature and the loading rate was 1000 kg f/win.

FIG. 5 shows the relationship between the blasting depth H formed on the surface of the base material and the adhesion force. This time, since the depth when blasting was performed using the conventional method was used as a reference, the blasting depth H using the conventional method was set to 0 μm.

The adhesion of the film tends to increase as the blasting depth increases, and at a blasting depth of 80 μm, the adhesion is improved by about 40% compared to the conventional method.

Further, an improvement in adhesion was observed regardless of whether the diameter of the holes provided in the perforated flat plate used to cover the base material was 2 m or inn, and there was no significant difference due to the difference in hole diameter.

In general, forming irregularities on the surface of the base material improves the adhesion of the sprayed coating due to the mechanical entrapment effect (anchoring effect).
It is said that it depends. In other words, by entering the molten or semi-molten particles into the recesses formed on the surface of the base material, the mechanical bite effect between the sprayed coating and the base material increases, and as a result, the adhesion between the sprayed coating and the base material increases. improves.

As shown in this example, when recesses are formed by blasting using a perforated flat plate, the deeper the blasting depth, the better the adhesion. This shows that the embedding effect has become larger.

Next, the results of a heat resistance test conducted on a film formed according to the present invention will be described. When a material with a thermally sprayed coating formed on a base material is heated and cooled, thermal stress is generated between the base material and the coating due to the difference in coefficient of thermal expansion between the two, resulting in peeling or cracking of the coating. occurs. In this test, we investigated the influence of recesses formed on the surface of the base material on these phenomena.

As a heat resistance test method, a test piece was first set in an electric furnace and kept at high temperature and in a vacuum for a certain period of time, then cooled to room temperature, and the test piece was taken out. Next, the extracted test piece was subjected to external appearance observation and cross-section wt observation using an optical microscope (magnification: 100 to 400 times). The test conditions at this time include temperatures of 1600 K and 2000 K, holding time of 1 hour, and degree of vacuum of 2 to 3 x 10''-'torr.

As a result of investigating the test piece taken out after the test, it was found that the test piece prepared according to the present invention showed that the test piece prepared according to the present invention had an external mist temperature of 1600 K and 2000 K by visual inspection.
The film was healthy with no peeling or cracking observed.

On the other hand, in the case of test pieces prepared by the conventional method, the temperature was 16
The sample No. 00 had a sound appearance, but the sample No. 2000 had large racks on the film and some peeling of the film.

In addition, in the cross-sectional wA observation of the film, fine racks (10 μm or less) were generated in the test pieces prepared according to the present invention at both 1600K and 2000K.
There was no peeling of the film.

On the other hand, when using the conventional method, large racks occurred in both 1600 and 2000 cases. The reason why the cracks become so fine is that in the present invention, the unevenness of the base material makes the interface between the base material and the coating difficult to slip, and the stress is dispersed, preventing peeling or large ranks. Seem.

Although graphite was used as the base material in the above embodiments, the present invention is also applicable to metals, ceramics, etc. Furthermore, the present invention is not limited to plasma spraying;
It is also applicable to other thermal spraying methods such as flame spraying and arc spraying. Furthermore, the thermal spraying material is not limited to high melting point materials, but can also be applied to other metals, ceramics, etc.

Furthermore, for the perforated plate that covers the surface of the base material during blasting, variations in hole diameter, hole shape, hole arrangement, perforated plate thickness, etc. can be considered, and other materials such as wire mesh can also be applied. It is.

Furthermore, as a blasting method, the particle size of the blasting material,
Possible variations include the material of the blasting material, the pressure of compressed air, the distance between the blast gun and the base material, the moving speed of the blast gun, the moving route of the blast gun, the number of passes, etc.

〔Effect of the invention〕

According to the present invention, the surface of the base material can be unevenly formed in spots during the blasting process, which improves mechanical engagement between the base material and the film, which is effective in improving adhesion and preventing peeling of the film.

Therefore, the present invention is effective as a method for forming a thermal spray coating on members that require high adhesion between the base material and the coating, and members where large thermal stress is generated between the base material and the coating due to heating and cooling.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of a thermal sprayed coating formed by the method of the present invention, and FIG. 2 is a diagram showing the method of forming a thermal sprayed coating according to the present invention.
Figure 3 is a diagram of the movement path of the tip of the blast gun, Figure 4 is a plan view of the perforated flat plate used in the blasting process of the present invention, and Figure 5 is the relationship between the blasting depth and adhesion force formed on the surface of the base material. It is a diagram. 1. Base material, 2... Thermal spray coating layer, 3... Concavity, 4... Irregularities on the surface of the base material, 5... Graphite base material, 6... Blast gun, 7... Teflon flat plate , 8... High melting point metal layer, 9... High melting point oxide ceramic layer, T... Blast gun moving direction, G... Flow of powder to 〇203, H... Depth of recess, R.・Movement path of the tip of the blast gun, B: Blast start position, E: Blast end position, P: Pitch. D: Outer diameter of Tochiflon extraction, D2: Outer diameter of hole.

Claims (7)

[Claims] 1. A blasting method comprising the steps of: covering the surface of a base material with a perforated member; and spraying fine particles and scraping the surface of the base material with the fine particles that have passed through the holes of the perforated member. 2. a step of covering the surface of the base material with a perforated member; a step of spraying fine particles and scraping the surface of the base material with the fine particles passing through the holes of the perforated member; and spraying a molten or semi-molten powder onto the surface. A method for producing a thermal spray coating, the method comprising: forming a coating by 3. A step of spraying fine particles onto the substrate surface to form a small uneven surface, a step of covering the small uneven surface with a perforated member, and a step of spraying the fine particles and forming the small uneven surface by the fine particles passing through the holes of the perforated member. 1. A method for producing a thermal spray coating, comprising the steps of: forming a large uneven surface by scraping the surface; and spraying a molten or semi-molten powder onto the surface to form a coating. 4. 4. The method for producing a thermal spray coating according to claim 2, wherein the particle size of the fine particles is the same as or smaller than the pore size of the porous member. 5. 5. The method for producing a thermal spray coating according to claim 2, wherein the perforated member is a perforated flat plate and is also a wire mesh. 6. The method for producing a thermal spray coating according to any one of claims 2 to 5, characterized in that the step before forming the thermal spray coating is repeated multiple times. 7. A base, a thermally sprayed coating adhered to the surface of this base material,
In the close-contact laminated member, the contact surface between the base and the thermal sprayed coating is provided with a large uneven surface formed by recesses and protrusions of each member, and a small uneven surface formed on the large uneven surface. A close-contact laminated member characterized by: