JP2009068051A - Thermal spraying method for forming sprayed coating having excellent adhesion - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal spraying method where the surface of a base material is subjected to roughening and cleaning combined with a specified treatment means before thermal spraying, thus the base material and the obtained sprayed coating have excellent adhesion even under severe conditions. <P>SOLUTION: Regarding the thermal spraying method where a sprayed coating having excellent adhesion is formed on the surface of a metal base material, the surface of a metal base material is subjected to blast treatment, next, the surface of the metal base material is subjected to reduced pressure arc cleaning in a state where external force is acted on the surface of the metal base material from the normal direction, and is subsequently subjected to thermal spraying treatment. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a thermal spraying method for forming a thermal spray coating on a metal substrate, and more particularly to a thermal spraying method with improved adhesion between the base material and the thermal spray coating.

As a method for improving the adhesion between the thermal spray coating and the substrate, blasting has been conventionally performed as a pretreatment for thermal spraying. The reason for this is the removal of rust on the substrate, foreign matter such as coatings, and contaminants, as well as making the surface of the substrate uneven, widening the contact area between the coating and the substrate, and the "anchor effect" by fitting into the coating. It is for having. Alumina, silicon carbide, etc. are used as abrasives for blasting, but since these abrasives are injected at a high speed with compressed air, dust and noise are generated in the process, which burdens the environment and workers. There is a big need for improvement.
In addition, this method is inexpensive and easy, but only a certain degree of adhesion can be obtained because the blast material or fragments thereof are stuck on the surface and remain at the substrate / film interface even after the film formation.
For example, when SUS304 stainless steel is deposited on mild steel by an atmospheric plasma spraying method, the adhesion strength of the practically used one is about 50 N / mm ² (or Mpa). Speaking of 50 N / mm ² is the tensile strength of plastic, and therefore there is a fixed idea among spraying related engineers that “the spray coating is easy to peel”.

Thus, a method of manufacturing a multilayer metal material has been proposed in which a blasting process is followed by a polishing process with a wire brush, followed by thermal spraying (see, for example, Patent Document 1).
Further, a pretreatment method is known in which a surface treatment is performed by spraying a thermal spray material and generating a vacuum arc discharge using a thermal spray material as a cathode (see, for example, Patent Document 2).
However, in the conventional film formation method by the thermal spraying after the pretreatment method, the adhesion strength of the thermal spray coating is not low enough, and it has not been possible to meet the demand for improving the performance of various devices.
On the other hand, in Patent Document 3, the surface of the metal substrate is subjected to blasting, then subjected to surface oxidation, and then subjected to vacuum arc cleaning, followed by thermal spraying to adhere the base and the resulting thermal spray coating. A thermal spraying method that improves strength is described.
However, in devices used under harsher conditions, further improvement in adhesion strength between the base material and the thermal spray coating is required.
Japanese Patent No. 3425496 Japanese Patent Laid-Open No. 5-98412 JP 2005-350748 A

  The present invention has adhesion that allows the base material and the thermal spray coating obtained to adhere to each other even under harsh conditions by roughening and cleaning the base material surface combined with specific treatment means before spraying. The object is to provide a thermal spraying method.

As a result of intensive studies in view of the above problems, the present inventors have found that a high adhesion strength of the coating can be realized by performing a specific reduced-pressure arc cleaning process after the blasting process as a pre-spraying process. Therefore, the present invention has been completed based on this finding.
That is, the present invention
(1) After blasting the surface of the metal substrate, and then subjecting the surface of the metal substrate to a reduced pressure arc cleaning process in a state where an external force is applied from the normal direction, the adhesion to the surface of the metal substrate to be sprayed is performed. Thermal spraying method to form an excellent thermal spray coating,
(2) The thermal spraying method according to (1), wherein the external force is gravity, and a reduced-pressure arc cleaning process is performed with the surface of the metal substrate facing downward.
(3) The thermal spraying method according to (1) or (2), wherein the thermal spray coating is made of one material selected from the group consisting of metals, alloys, ceramics, and cermets.
(4) The thermal spraying method according to any one of (1) to (3), wherein the thermal spray coating is made of stainless steel.
(5) The surface of the metal substrate is blasted, and then subjected to a reduced pressure arc cleaning treatment in a state where an external force is applied to the surface of the metal substrate from the normal direction, and then a metal is sprayed to form a metal film. A thermal spraying method in which an external force is applied from the normal direction to the surface of the metal base to perform a reduced-pressure arc cleaning process, and a thermal spray coating having excellent adhesion is formed on the surface of the metal base to be ceramic sprayed,
(6) The thermal spraying method according to any one of (1) to (5), wherein when the thermal spraying process is a reduced pressure thermal spraying process, the reduced pressure arc cleaning process is also performed during thermal spraying, and
(7) A multilayer metal material obtained by the thermal spraying method according to any one of (1) to (6),
Is to provide.
In the present invention, reduced-pressure arc cleaning (VAC) is arc cleaning performed in a pressure range of 10 to 5000 Pa, and is a concept including vacuum arc cleaning.

According to the present invention, since the blast material does not remain at the interface and the unevenness of the interface is deep and thin, it is possible to form a sprayed coating with extremely strong adhesion strength between the substrate and the sprayed coating. And the adhesion strength could be greatly exceeded compared with the film | membrane obtained by the conventional method.
The metal material with a thermal spray coating obtained by the present invention is frequently used for aircraft ethidine, gas turbine engines for power generation, engines for automobiles, etc., and can cope with more severe conditions, and has a high adhesion strength. Improvement can directly contribute to high performance of equipment, long life, resource saving, and energy saving.
In addition, the method of the present invention can reduce the environmental load and the blasting time that is heavy on the operator.

A preferred embodiment of a thermal spraying method for forming a thermal spray coating having excellent adhesion according to the present invention will be described in detail.
The sprayed coating material of the present invention may be any material that has been used so far, such as metal, alloy, ceramic, cermet, etc., for example, steel-based material, molybdenum, titanium, etc., and stainless steel, molybdenum, etc. are particularly preferred. .
In the present invention, as the metal base material on which the thermal spray coating is formed, steel materials, stainless steel, aluminum, alloys and the like can be used, and steel materials and stainless steel are preferable.

Blasting is indispensable as a pretreatment for thermal spraying, but the blasting surface is contaminated because oxides such as alumina are used as a blasting material. This is one cause of the decrease in adhesion. Furthermore, even if the blast treatment is performed for a long time, the substrate is only worn and the surface roughness is not increased.
The blasting process has many conditions such as the particle size of the blasting material, the air pressure, and the blasting distance, but any blasting process that can be used in the present invention is not particularly limited. For example, it is preferable to use # 20 to 100 alumina as a blast material and perform air pressure of 0.5 MPa to 0.7 MPa.
Further, since the reduced pressure arc cleaning process is performed as will be described later, the blasting process does not need to be performed for a longer time than in the past.

As a result of the blast treatment, irregularities are formed on the surface of the metal substrate, and most of the oxide film present on the substrate has been removed, but impurities such as the blasting material or its fragments remain, so that the thermal spray coating has high adhesion. A vacuum arc cleaning process is performed.
An oxide film may be formed on the surface of the metal substrate during the reduced-pressure arc cleaning process.

  Next, a reduced pressure arc cleaning process is performed on the blasted metal substrate. The reduced-pressure arc cleaning process has various conditions such as chamber pressure, voltage, current, and cleaning time. In the present invention, these conditions can be set as appropriate. For example, the chamber pressure is 100 Pa, the current is 20 to 90 A, and the cleaning time is preferably 1 to 10 seconds.

  FIG. 1 shows a schematic configuration of an example of a preferred reduced-pressure arc cleaning processing apparatus. The main structure is a vacuum vessel 1, a water-cooled copper electrode (anode) 2 provided in the vessel, a support 4 covered with an insulator 5 and an object to be processed which is supported by the support and becomes a cathode. It comprises a metal substrate 3, a DC power source 6, an RF (high frequency) igniter 7, a timer switch 8, a viewing window 9, a gas inlet 11 provided with a valve 10, a gas outlet 13 provided with a filter 12, and a pressure gauge 14.

  1, for example, after setting the metal substrate 3 on the support 4 and injecting argon gas from the gas inlet 11 in the direction of the arrow, the gas is supplied from the gas outlet 13 by a vacuum pump or the like in the direction of the arrow. The discharge is repeatedly performed several times, the inside of the container 1 is depressurized to about 100 Pa, and an arc is ignited using an RF (high frequency) igniter 7, whereby a reduced pressure arc cleaning process can be performed.

In the present invention, the reduced-pressure arc cleaning is performed in a state where an external force is applied from the normal direction to the surface of the metal substrate.
In the embodiment shown in FIG. 1, the surface of the metal substrate 3 is set downward, and therefore, the surface of the metal substrate 3 is in a state where gravity acts on the surface from the normal direction.
In the present invention, the external force acting on the surface of the metal substrate from the normal direction is not limited to the above-described gravity, and examples thereof include centrifugal force. Further, the magnitude of the external force acting (loaded) on the surface of the metal substrate is preferably 10 m / s ² (1G) or more, and more preferably 30 to 300 m / s ² (3G to 30G).

The spraying process may be any spraying method that is generally used. As an example of the atmospheric pressure plasma spraying method, a current of 600 to 850 A, a voltage of 35 V, an argon pressure of 0.35 MPa (50 psi), and a helium pressure of 0.35 to 0.69 MPa (50 to 100 psi) are appropriate.
Thus, a sprayed coating having excellent adhesion is formed.

  In the present invention, a plurality of thermal spray coatings can also be formed. In this case, after forming the first layer coating, the reduced pressure arc cleaning treatment is performed again while applying a force in the normal direction from the surface of the metal substrate to remove the surface oxide, followed by the formation of the outer layer thermal spray coating. To do. Thus, the adhesion strength between the respective layers can be strengthened by performing the reduced-pressure arc cleaning treatment during the film formation. This method is also preferable when a ceramic film is formed on the outer layer.

In the present invention, it is important to perform the blasting process and the reduced pressure arc cleaning (VAC) process in this order as a pre-process of the thermal spraying process.
After the blast treatment, the VAC treatment has a larger and finer surface cross section than the blast treatment or the VAC treatment alone. It is considered that when the VAC process is performed after the blasting process, the electric field concentrates on the convex part formed by the blasting process and a cathode spot is generated, melting and evaporation occur due to the high current density, and the unevenness is further increased.

It can be considered as follows from the micrograph of the surface of the metal substrate that has been subjected to VAC treatment after blast treatment.
(1) Oxides, residual blasting material by blasting, etc. are almost completely removed, and a clean surface can be obtained.
(2) Since the surface melts thinly and a new surface is exposed, the surface is activated.
(3) Since a part of the thinly melted base material is lifted upward by the strong arc at the time of oxide removal, the interval between the crests of the roughness is smaller than the blast alone. At this moment, since the arc moves to another part at the moment of lifting, the molten part solidifies while falling. For this reason, a mushroom-shaped mountain is formed in the uneven part. Because the thermal spray coating enters under the mushroom-shaped umbrella, a strong anchor effect is exhibited.
By such a mechanism, it is considered that the base material-coating interface is clean, the base material and the coating are bonded together with diffusion, and a thermal spray coating having a remarkably high adhesion strength is formed.

  Furthermore, when the above VAC treatment is performed with a downward VAC with the surface of the metal substrate to be treated facing downward, and with an upward VAC with the surface of the metal substrate to be treated facing upward, the formed protrusions The object can be formed as a thick mushroom-like protrusion with the vertically downward VAC. This is considered to be the effect of gravity, and the surface shape can be further roughened by an external force acting in the normal direction. This further roughening of the surface enables a stronger adhesion between the thermal spray coating and the substrate.

As described above, improvement of the adhesion of the film is the most basic requirement for the film, and it is possible to improve the performance of all devices using the film. Among these, specific examples that can be achieved only by improving adhesion and removing oxides will be described in detail.
(1) Lighter and more compact automobile engines As is well known, improving the fuel efficiency of automobiles is an important issue for automobile manufacturers, and reducing the vehicle weight is a major requirement for improving fuel efficiency. By lightening the heaviest engine among car parts, various parts and members that fix the engine can be reduced in weight, and a ripple effect can be expected.
For this reason, each company has developed that a cylinder block is made of a lightweight aluminum alloy and a hard metal film is formed on the cylinder block by a thermal spraying method. This method also has the advantage that the dimensions between the cylinders can be reduced, and it is a measure that can be said to be two birds with one stone for a car that lays the engine horizontally and drives the front wheels.
However, the biggest problem that hinders practical use is the low adhesion of the film, so that each automobile manufacturer has a film that forms a cylinder even after traveling 100,000 km (km) and 200,000 km (km). The current situation is that there is no confidence that it will not peel off.
If the thermal spraying method of the present invention is used, it can be expected that the adhesion strength of the coating will be increased and it can be an effective method for the production of lightweight and compact cylinders.

(2) Higher efficiency of aircraft and power generation gas turbine engines In order to increase the output and efficiency of gas turbine engines, the turbine inlet temperature is getting higher and exposed to high-temperature and high-speed combustion gases. Thermal insulation coating (TBC) is essential for turbine blades. The TBC currently used is composed of two layers of CoNiCrAlY used as a bond coat and ZrO ₂ —Y ₂ O ₃ (PSZ) that plays a role of heat insulation. However, in a gas turbine for power generation, which is particularly difficult to operate, the life of the heat insulating film is said to be about half a year, and extending the life of the heat insulating film is the key to high efficiency.
There are many research results regarding TBC, and it has been clarified that the cause of film peeling is an oxide generated on the surface of CoNiCrAlY as a bond coat. As is well known, in oxidation and corrosion phenomena, oxides and corrosion products become a kind of catalyst, and oxidation and corrosion further progress.
Therefore, if the present invention is applied in forming the TBC film,
1. The adhesion strength between the base material and CoNiCrAlY can be significantly increased.
2. The oxide can be almost completely removed from the surface of CoNiCrAlY formed by thermal spraying.
3. The adhesion between CoNiCrAlY and PSZ can be significantly increased.
For these reasons, it is considered possible to greatly extend the peel-resistant life of TBC. Therefore, if this technology is adopted for aircraft engines, the maintenance interval can be extended,
The economic effect is immeasurable.

(3) Development of low-pressure plasma spraying that does not contain oxides in the film Even when a metal film is formed by a low-pressure plasma spraying device, a small amount of oxide is found when the cross-section of the film is observed with a scanning electron microscope (SEM), for example. Being present is a common experience. This small amount of oxide sometimes causes mechanical properties to deteriorate and corrosion resistance to deteriorate. However, in the thermal spraying method currently in practical use, a film is formed without any oxide in the film. I can't. Therefore, if a technology capable of completely removing oxides from the sprayed coating is developed, it can be said that it is epoch-making.
In the present invention, if the reduced-pressure arc cleaning process is continuously performed during the thermal spraying using the reduced-pressure plasma spraying method, the arc by the reduced-pressure arc cleaning process selectively acts on the oxide. It is considered possible to form

Example 1
First, the steel base material (SS400) was used as a sample, and the end surface was manually blasted using # 20 alumina particles. The blast air pressure is 0.7 MPa, the nozzle diameter is 8 mm, and the distance between the substrate and the nozzle is about 100 mm.

  The sample was placed on the support 4 in the vacuum vessel shown in FIG. 1, the metal substrate sample was used as a cathode, the inside of the vacuum vessel 1 was exhausted to 100 Pa or less, and an Ar gas atmosphere was formed. After evacuating the container, a DC voltage was applied between the sample and the electrode to cause a DC arc discharge. The reduced-pressure arc cleaning process was performed by setting the distance between the electrodes to 20 mm, the current to 20 A, and the arc time to an arbitrary time of less than 10 seconds.

A sprayed coating was formed on the end face of the cylindrical sample by plasma spraying on the sample subjected to the reduced-pressure arc cleaning treatment. SUS316 stainless steel was used as the thermal spray material, and the thickness of the thermal spray coating was targeted at 200 μm.
The spraying conditions were as follows: arc current: 800 A, spraying distance: 100 mm, spraying angle: 90 °, main gas: Ar (0.35 MPa), auxiliary gas: He (0.69 MPa), discharge rate: 30 g / min.

Comparative Example 1
After blasting the metal substrate in the same manner as in Example 1, as shown in FIG. 2, the cathode and anode are replaced from the configuration shown in FIG. As in Example 1, a reduced pressure arc cleaning process and then a thermal spraying process were performed to form a sprayed coating on the surface of the metal base material, except that the reduced pressure arc cleaning was performed with the surface facing upward.
In addition, the meaning of the code | symbol in FIG. 2 is the same meaning as the code | symbol in FIG.

Test example 1
The cross section including the surface of the sample before the vacuum arc cleaning (VAC) treatment in Example 1 and Comparative Example 1 and after the VAC treatment for a certain time was observed with an optical microscope. The observed micrograph is shown in FIG.
In FIG. 3, the left side a to f show the sample cross section after the upward VAC treatment of Comparative Example 1, and the right side g to l show the sample cross section after the downward VAC treatment of Example 1. Further, a and g indicate the cross section of the sample in which the VAC processing time is 0, that is, only the blast processing is performed. In addition, b and h are processing times of 1 second, c and i are processing times of 3 seconds, d and j are processing times of 5 seconds, e and k are processing times of 7 seconds, and f and l are processing times of 9 seconds. . In addition, all the magnifications of FIGS. 3A to 1L are the same, and the dividing line shown below a and g indicates a length of 50 μm.
As shown in FIG. 3, mushroom-like protrusions are found everywhere in Comparative Example 1 (FIGS. 3A to 3F) subjected to upward VAC treatment and Example 1 (FIGS. 3G to l) subjected to downward VAC treatment. However, when the formed protrusions were compared, Example 1 which performed the downward VAC treatment became longer and longer. Thus, since the influence by gravity can be seen, it can be expected that the surface shape is further roughened by an external force.

Test example 2
The sample after VAC treatment before and a predetermined time VAC process in Example 1 and Comparative Example 1, by using a laser microscope, the arithmetic mean height of surface roughness R _a and the average profile elements the length R _sm It was measured.
Here, the arithmetic average height R _a is extracted from the roughness curve by the reference length l in the direction of the average line, and the average line m of this extracted portion is taken as the x-axis (y = 0), from which the measurement curve The absolute values of the deviations up to are totaled and averaged. That is, as shown in the explanatory diagram of FIG. 4, the area surrounded by the x-axis and the roughness curve is added to the reference length on the roughness curve f (x), and averaged regardless of the shape of the roughness. Value. The derivation formula is shown below

(In the formula, l represents the reference length (m).)
Further, the average length R _sm of the contour curve element is extracted from the roughness curve as shown in the explanatory diagram of FIG. 5 only in the direction of the average line L, and one peak and The sum of the lengths of the average lines corresponding to one adjacent valley (interval between irregularities) is obtained, and the arithmetic average value of the intervals between the numerous irregularities is expressed. Here, the average value of the roughness curve is m (x axis). There are mountains and valleys of various heights on the target surface even though they are called mountains and valleys, but the highest one is the maximum height Rz, and 10% of Rz. The above peaks and valleys were counted, and those below were not used for the calculation of R _sm . The derivation formula is shown below.

(In the formula, Smi is the unevenness interval (m), and n is the number of unevenness intervals within the reference length)
The results are shown in FIGS. 6-8, ■ shows Example 1, and ◆ shows Comparative Example 1. FIG. In addition, the value in the case of only blast processing is indicated by a dotted line.

FIG. 6 is a graph showing a change in arithmetic average height R _a (μm) with respect to VAC processing time (arc time (s)). In the same processing time, _Ra is larger in both upward and downward directions than in the case of blasting alone, and the value of _Ra in Example 1 in which downward VAC is performed is about twice as large as that in Comparative Example 1 in which upward VAC is performed. It is shown to be big.
FIG. 7 is a graph showing changes in the average length R _sm (μm) of the contour curve elements with respect to the VAC processing time (arc time (s)). At the same processing time, R _sm is smaller than the case of only blasting in both upward and downward directions, and there is no great difference in the horizontal unevenness interval R _sm between Example 1 and Comparative Example 1.
FIG. 8 is a graph showing changes in the ratio R _a / R _{sm with} respect to the VAC processing time (arc time (s)). At the same processing time, the ratio of R _a / R _sm is larger both in the upward and downward directions than in the case of blasting alone. In Example 1 in which downward VAC was performed, R _a / R _{sm was} higher than that in Comparative Example 1 in which upward VAC was performed. The value is shown to be large.
In this way, the downward VAC treatment can greatly roughen the surface of the metal substrate as compared with the upward VAC treatment or blasting alone.

Test example 3
Next, the adhesion strength of the coatings of the samples on which the thermal spray coatings having different arc treatment times in Example 1 and Comparative Example 1 were measured in accordance with the thermal spray coating test method of JIS H8666.
In this test, the A test piece was formed by forming a film in Example 1 and Comparative Example 2. The A test piece is a cylinder having a diameter of 25 mm and a length of 40 mm, and an M16 screw is cut on the opposite end face to fix it to the jig of the tensile tester.
Only the blasting was applied to the B test piece of the same size, and the A test piece and the B test piece were bonded to the test rod (mating material) with a strong adhesive. In this measurement, an epoxy resin adhesive (trade name: Araldite AT-1, manufactured by Ciba Geigy Co., Ltd.) was used, and the adhesive was heated at 150 ° C. for 40 minutes. The strength of this adhesive is about 85 N / mm ² . Thereafter, a chucking bar was screwed to the other end of both the A and B test pieces, attached to a tensile tester, and a tensile test was performed to measure the adhesion strength of the film.

FIG. 9 shows a change in the adhesion force (MPa = N / mm ² ) between the film and the metal substrate with respect to the VAC treatment time (arc time (s)). In FIG. 9, ■ represents Example 1, and ◆ represents Comparative Example 1. In addition, the value in the case of only blast processing is indicated by a dotted line.
As shown in FIG. 9, the adhesive strength of Example 1 treated with downward VAC was higher by about 20 MPa at the maximum than Comparative Example 1 treated with upward VAC.

Example 2
In the apparatus shown in FIG. 1, the cathode and anode members are changed to the rotating VAC member shown in the schematic configuration diagram of FIG. 10, the internal pressure of the container is set to 200 Pa, centrifugal force is applied to the surface of the metal substrate, and the reduced pressure arc A thermal spray coating was formed on the surface of the metal substrate in the same manner as in Example 1 except that the cleaning treatment was performed.
In FIG. 10, a metal substrate (cathode) 21 and a copper electrode (anode) 22 are rotated by a motor 23 around a magnetic shield shaft 24 as a rotation axis. 25 is an insulator, and 26 is a conductor. The conductor 26 and the cathode 21 are formed to be energized. The drive part is formed of the members indicated by these reference numerals 21 to 26. On the other hand, a minus electrode 28 and a plus electrode 29 are fixed to the electrode support (insulating) material 27, the minus electrode 28 is in contact with the rotating conductor 26, and the plus electrode 29 is in contact with the rotating anode 22. The interelectrode distance 30 was 20 mm. VAC was performed at rotation speeds of 200 rpm and 600 rpm, with arc times of 3 seconds (200 rpm) and 5 seconds (200 rpm and 600 rpm).
The adhesion of the obtained film was measured in the same manner as in Test Example 3. The results are shown in Table 1. For comparison, Table 1 shows the adhesion strength of Reference Example in which blasting alone was performed as a pretreatment, Example 1 in which blasting and inverted VAC were performed, and Comparative Example 1 in which blasting and upward VAC were performed. Shown together.

Comparative Example 2
Blast treatment is not performed on the surface of the metal base material, and fine pyramid-shaped protrusions are regularly formed by knurling. Example 1 (inverted VAC), Example 2 (rotary VAC) and Comparative example 1 (upward VAC) The spray coating was formed on the surface of the metal substrate by performing the VAC treatment and the thermal spray treatment in the same manner as in FIG. The adhesion of this sprayed coating was measured in the same manner as in Test Example 3. The results are shown in Table 1.

As shown in Table 1, the pretreatment was 32 N / mm ² in the reference example in which only the blast treatment was performed, but in Comparative Example 1 in which the “upward VAC” treatment was performed, the adhesion strength doubled to 65 N / mm ² . . Furthermore, in Example 1 where the “inverted VAC” treatment was performed with the test piece (cathode) at the top and the anode at the bottom, an extremely high adhesion strength of 80 to 95 N / mm ² could be achieved. In this case, the test piece is loaded with 1 G of gravity. In the adhesion strength measurement based on JIS H 8666, a tensile test is performed by bonding a test piece with a film and a test rod (mating material) with a thermosetting strong adhesive. In the case of blasting + inverted VAC, there was an example where the adhesive was broken in the same test, so the actual adhesion strength is considered to be higher.
Further, in Example 2, a high value of 54 to 65 MPa (1.7 to 2.0 times relative to the reference example of blasting alone) was obtained as the adhesion strength. In the rotating VAC in Example 2, as described above, the rotation was performed at 200 rpm and 600 rpm under a pressure of 200 Pa. The centrifugal forces acting on the test surface at this time are 3G and 28G, respectively. The adhesion strength under such high G was almost the same as blast + normal (upward) VAC.
Further, in the knurled processing of Comparative Example 2 + various VACs, the adhesion strength was 22 to 32 MPa. The reason why the adhesion strength did not become high is that the pyramid-shaped convex portion formed by knurling processing had a vertical angle of 90 degrees, so the heat capacity of the pyramid increased, and the surface of the conventional VAC treatment did not melt, Therefore, it is considered that the shape of the tip of the convex portion was not a mushroom shape.

It is a schematic block diagram of an example of the pressure reduction arc cleaning apparatus which implements this invention. 2 is a schematic configuration diagram of a reduced-pressure arc cleaning device used in Comparative Example 1. FIG. 2 is an optical micrograph of a cross section including the surface of an arc-treated sample in Example 1 and Comparative Example 1. FIG. The arithmetic mean it is an explanatory view of height R _a. It is explanatory drawing of the average length _Rsm of a contour curve element. It is a graph which shows the change of arithmetic mean height Ra with respect to the VAC processing time of Example 1 and Comparative Example 1. It is a graph which shows the change of the average length R _sm of the contour curve element with respect to the VAC processing time of Example 1 and Comparative Example 1. It is a graph which shows the change of _Ra / _Rsm ratio with respect to the VAC processing time of Example 1 and Comparative Example 1. It is a graph which shows the change of the film | membrane adhesive force with respect to the VAC processing time of Example 1 and Comparative Example 1. It is a schematic block diagram of the rotation VAC apparatus used in Example 2.

Explanation of symbols

1 Vacuum container 2 Copper electrode (anode)
3 Metal substrate (cathode)
4 Supporting Tool 5 Insulator 6 DC Power Supply 7 RF Igniter (High Frequency Igniter)
8 Timer switch 9 Peep window 10 Valve 11 Gas inlet 12 Filter 13 Gas outlet 14 Pressure gauge 21 Metal substrate (cathode)
22 Copper electrode (anode)
23 Motor 24 Magnetic shield shaft 25 Insulator 26 Conductor 27 Electrode support (insulation) material 28 Negative electrode 29 Positive electrode 30 Distance between electrodes

Claims (7)

  After blasting the surface of the metal substrate and then performing a reduced-pressure arc cleaning process with an external force acting on the surface of the metal substrate from the normal direction, the metal substrate surface to be thermally sprayed has excellent adhesion. A thermal spraying method for forming a thermal spray coating.   The thermal spraying method according to claim 1, wherein the external force is gravity, and the reduced-pressure arc cleaning process is performed with the metal substrate surface facing downward.   The thermal spraying method according to claim 1 or 2, wherein the thermal spray coating is made of one material selected from the group consisting of metals, alloys, ceramics, and cermets.   The thermal spraying method according to any one of claims 1 to 3, wherein the thermal spray coating is stainless steel.   After blasting the surface of the metal substrate, and then performing a reduced-pressure arc cleaning process with an external force applied to the surface of the metal substrate from the normal direction, the metal is sprayed to form a metal film, and then the metal A thermal spraying method in which a reduced pressure arc cleaning process is performed with an external force applied to the surface of a base material from the normal direction to form a thermal spray coating having excellent adhesion on the surface of the metal base material to be ceramic sprayed.   The thermal spraying method according to any one of claims 1 to 5, wherein the thermal spraying process is a low-pressure thermal spraying process, and the vacuum arc cleaning process is also performed during thermal spraying.   The multilayer metal material obtained by the thermal spraying method of any one of the said Claims 1-6.