JPH0813118A - Adhesion structure of thermally sprayed coating film and improvement of adhesion of thermally sprayed coating film - Google Patents

Abstract

PURPOSE:To enhance the metallurgical joining property of a thermally sprayed coating film to a base material composed of aluminum alloy and to improve the adhesion of the sprayed coating film. CONSTITUTION:A base material such as piston, consisting of aluminum alloy (Al-Si), and a thermally spraying material, containing an alloying element (Cu) having a melting point lower than that of the aluminum alloy constituting the base material and capable of forming a melt layer, are used. This thermally spraying material is subjected to thermally spraying treatment, by which the sprayed coating film is laminated on the base material. Subsequently, heating is done for 2hr to 530 deg.C as a temp. corresponding to the solution heat treatment temp. of T6 and T7 treatment, by which a melt layer is formed in an interfacial region. Then, by applying cooling, an interfacial melted and solidified layer is formed in the interface between the sprayed coating film and the base material and metallurgical joining property is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sprayed film adhesion structure and a sprayed film adhesion improving method. INDUSTRIAL APPLICABILITY The present invention can be applied to, for example, a piston ring groove of an internal combustion engine and a bore sliding surface of a cylinder.

[0002]

2. Description of the Related Art Conventionally, a thermal spray coating is laminated on a base material. Generally, the mechanical bond is the main contact between the sprayed film and the base material, and the base material is roughened by shot blasting before the spraying process to increase the surface area or create a new surface, thereby forming a sprayed film. Has increased the adhesion.

As another method for improving the adhesion of the sprayed coating, a method of preheating a base material in a state before the spraying treatment has been proposed. In addition, Japanese Patent Publication No. 54-42855 discloses that a base material having a surface exposed by shot blasting,
The surface of the base material is sprayed with powder made of white cast iron.
A technique of stacking a cured layer having improved adhesion is disclosed.

[0004]

The degree of roughening of the exposed surface by shot blasting is greatly influenced by the cleanliness, the size, shape and material of the blast particles. Therefore, the adhesion of the sprayed coating tends to vary considerably, the reliability is not always sufficient, and the current situation is to manage the process. Therefore, peeling of the sprayed film is likely to occur, and defects often occur. Therefore, the lamination of the sprayed film on the exposed surface shot blasted,
Although it is applied to relatively less important parts, the fact is that it has not been applied to highly important parts.

Even in the case of preheating the base material before the thermal spraying treatment described above, it is premised on the improvement of the adhesiveness by the shot blasting treatment, and the adhesiveness of the thermal spray coating cannot be greatly improved. Further, the technology according to the above-mentioned publication is also based on the premise that the adhesion strength is improved by the shot blasting treatment, and the adhesion strength of the sprayed film cannot be significantly improved, and the base material is not an aluminum alloy type but an iron material. It is intended for systems.

The present invention has been made in view of the above-mentioned circumstances, and enhances the metallurgical bondability of a sprayed film by forming an interfacial melt solidification layer at the interface between a base material made of an aluminum alloy and the sprayed film, An object of the present invention is to provide a sprayed film adhesion structure in which the adhesion of the sprayed film is improved and a sprayed film adhesion improving method.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive efforts to develop a mode of laminating a sprayed coating on a base material made of an aluminum alloy, and as a result, have found that a molten liquid having a melting point lower than that of the aluminum alloy constituting the base material. A thermal spray material containing an alloying element capable of forming a layer is used, and after the thermal spray material is sprayed on a base material to form a sprayed film, a temperature range in which a molten liquid layer can be formed (slightly above the eutectic temperature If heated to a temperature range) and then cooled, a thin interfacial solidification layer (presumed to be a eutectic structure or a structure containing a eutectic) is formed at the interface between the sprayed film and the base material, and metallurgical The inventors have found that the bond strength of the sprayed film to the base material is significantly improved by the bonding, and confirmed by a test to complete the present invention.

For example, in the phase diagram of a binary system of aluminum and another element (X) shown in FIG. 1, if a temperature Ta slightly higher than the eutectic temperature Te is heated, a molten liquid layer is locally formed. However, as the alloy concentration increases, the alloy solidifies immediately and, eventually, the melt layer is formed only in the interface region. Therefore, if this is cooled, a thin-walled interface melt solidification layer (presumed to be a eutectic structure or a structure containing a eutectic) is locally formed at the interface between the sprayed film and the base material, and the metallurgical It is considered that the bondability is improved.

That is, the sprayed film adhesion structure according to claim 1 is
It is composed of a base material made of an aluminum alloy having a surface to be exposed and a sprayed film laminated on the surface of the base material, and an interfacial melted and solidified layer that is melted and solidified is formed in the interface region between the sprayed film and the base material. It is characterized by that. The sprayed film adhesion improving method according to claim 2 is a method capable of easily manufacturing the sprayed film adhesion structure according to claim 1, and is lower than the base material made of an aluminum alloy and the aluminum alloy constituting the base material. Using a thermal spray material containing an alloying element capable of forming a molten liquid layer having a melting point, a thermal spray material is sprayed on the exposed surface of the base material to form a thermal spray film, and a molten liquid layer after the thermal spray treatment. By heating at least the sprayed film in a temperature range capable of generating, to form a local melt layer in the interface region between the sprayed film and the base material, and then by cooling it, the interface region between the sprayed film and the base material Is characterized in that an interfacial melt-solidified layer that is melt-solidified is formed, and a metallurgical joining step for enhancing metallurgical bondability in the interface region is sequentially performed.

[0010]

[Function] The base material made of an aluminum alloy and the sprayed film laminated on the exposed surface of the base material are metallurgically bonded through the interfacial melting and solidifying layer. Therefore, the sprayed film can obtain high adhesion strength.
In the first aspect, the interfacial melt solidification layer is considered to have a eutectic structure or a structure containing a eutectic. The composition of the eutectic generally depends on the composition of the sprayed powder, the aluminum alloy constituting the base material, and the like. In the case of a binary system, it is a binary eutectic, in the case of a ternary system, it is a ternary eutectic, and in the case of a multi-component system, it is a multi-element eutectic. The average thickness of the interface melting and solidifying layer is about 5 to 500 μm,
In particular, it can be 10 to 200 μm. In consideration of ensuring the bonding strength of the sprayed film, the interfacial melted and solidified layer is preferably present on substantially the entire interface between the substrate and the sprayed film, but may be partially present on the interface region.

The interface melt-solidified layer is formed by solidifying the melt liquid layer generated in the interface region between the base material and the sprayed film, so that the cooling rate for solidifying the interface melt-solidified layer can be made relatively high,
Therefore, the structure in the interfacial melting and solidifying layer is likely to be refined.
In a form in which the sprayed film 2 is further laminated on the exposed surface 1a of the base material 1 as schematically illustrated in FIG. 2, or on the exposed surface 1a of the base material 1 as illustrated schematically in FIG. The sprayed layer 3a may be laminated, and the second sprayed layer 3b may be laminated thereon.

During the thermal spraying treatment, a granular thermal spraying material whose surface is partially melted or a granular thermal spraying material which is entirely in the form of droplets collides with the exposed surface of the base material. Therefore, the internal structure of the sprayed film has a form in which slightly flat particles 4 are laminated, as schematically shown in FIG. In addition, between particles 4 is particle 4
Generally, it is easy to form micropores depending on the type. In the second aspect, a thermal spray material containing an alloy element capable of forming a melt layer having a melting point lower than that of the aluminum alloy forming the base material is used. When the thermal spray material is in the form of powder, the particle size can be about 1 to 100 μm, especially about 5 to 70 μm. Examples of such elements include copper, silicon, silver, tin and zinc. In this case, a powder obtained by alloying the alloy element can be used as a thermal spray material, or a mixed powder of the alloy element powder and an aluminum powder which is a thermal spray material can be used.

According to a second aspect of the present invention, the sprayed material is sprayed on the exposed surface of the base material to form a sprayed film. Prior to the thermal spraying treatment, it is preferable that the exposed surface of the base material is roughened by blasting as in the conventional case. This is because, in addition to metallurgical bonding by the interfacial melting and solidifying layer, mechanical bonding can be expected as in the conventional case, and further increase in adhesion of the sprayed coating can be expected. In the second aspect, after the thermal spraying treatment, at least the thermal sprayed film is heated to a temperature region where the above-mentioned molten liquid layer can be formed, so that the molten liquid layer is formed in the interface region between the thermal sprayed film and the base material. The heating temperature is several tens of degrees Celsius (e.g.
It is preferable to set the temperature above 30 ° C.). Therefore, when a eutectic is intended, the temperature is, for example, 2 to 5 rather than the eutectic temperature.
It is preferable to set the temperature above 10 ° C to 30 ° C even above 0 ° C.

The porosity of the sprayed film before carrying out the metallurgical bonding step can be appropriately selected according to the shape and type of the base material, but it is generally 2% by volume or less (in particular, 1% by volume or less, especially 0.8 volume% or less, 0.6 volume% or less) is preferable. It is considered that the smaller porosity is advantageous for avoiding the outflow of the molten liquid layer at the interface, and thus is advantageous for the formation of the interfacial melt solidification layer.

The heating may be carried out by charging the entire base material into a heating furnace to heat the entire base material, or by using induction heating or the like to locally heat the sprayed film. Thereafter, the sprayed film is cooled to solidify the melt liquid layer and form an interfacial melt solidification layer. In this case, the volume of the melt layer itself is significantly smaller than the base material volume, and
Since the base material is made of an aluminum alloy with high thermal conductivity, the heat of the melt layer is quickly transferred to the base material side, and the solidification cooling rate can be increased. Therefore, the structure of the interfacial melt solidification layer can be refined. obtain.

[0016]

【Example】

(Example 1) In the thermal spraying process, iron-based powder (atomized powder, -280 mesh, iron-1.0 wt% carbon) and copper-
Aluminum powder (atomized powder, -200 mesh, copper-
9 wt% aluminum), and both are mixed to form a mixed powder, which is used as a thermal spray material. Here, the whole mixed powder is 10
When the content was 0 wt%, the copper-aluminum powder had a blending ratio of 30 wt%.

As the base material, an aluminum alloy of JIS-AC8A which is an aluminum-silicon-magnesium system is used.
The exposed surface of the base material is roughened by blasting (Rz50-
It is about 150 μm). Then, the above-mentioned thermal spray material was sprayed onto the exposed surface of the substrate by a thermal spraying device. As a result, a sprayed film (average thickness of 400 to 600 μm) was laminated on the exposed surface. The porosity of this sprayed film is generally 0.5 to
It is 1% by volume. The thermal spraying conditions are HVOF thermal spraying method and O ₂ =
40 liters / min, propylene = 39 liters / m
in, air = 56 liter / min, powder supply amount = 90
Gram / min.

Next, a metallurgical joining process is carried out. That is, the base material on which the sprayed coating was laminated was placed in a soaking type heating furnace, heated and held at 530 ° C. for 2 hours in the air atmosphere, and heat-treated thereby. The temperature of this heat treatment corresponds to the T6 treatment or T7 treatment of the aluminum alloy constituting the base material. Therefore, the aluminum alloy constituting the base material is subjected to solution treatment as T6 treatment or T7 treatment. It will be.

During the heat treatment, the sprayed film was placed on the top and the substrate was placed on the bottom. Therefore, even if the porosity of the sprayed film is relatively high, it is considered to be advantageous for avoiding the outflow of the melt layer generated at the interface. After the heat treatment, it was air-cooled to a room temperature region. Then, it was heated and held at 170 ° C. for 10 hours in an air atmosphere to perform an aging treatment, and then air-cooled.

In this embodiment, the thermal spray material is copper-based as described above.
It contains aluminum powder, and the base material is an aluminum-silicon system. Considering the aluminum-copper-silicon ternary phase diagram, the eutectic temperature of the aluminum-copper-silicon ternary eutectic is determined to be 524 ° C. Therefore, as described above, when the substrate provided with the sprayed film is heated and held at 530 ° C. for 2 hours and then cooled, a melt having a eutectic composition or a composition close to the eutectic is generated at the interface, and solidification causes eutectic structure. It is also presumed that a structure containing eutectic was generated at the interface.

In this example, heat treatment (530 ° C. ×
The interface region between the sprayed film and the substrate after 2 hours) was observed with an optical microscope (magnification: 200 times), and this is shown in FIG. Further, as a comparative example, the interface region between the sprayed film and the base material was observed with an optical microscope (magnification: 200 times) before heat treatment, and this is shown in FIG. In FIGS. 5 and 6, the right side portion shows the base material, and the left side portion shows the thermal spray coating in which the powdery thermal spray material is laminated.

Further, in the embodiment, a scanning electron microscope (S
It was observed by EM). The photograph is shown in FIG. 7 (magnification: 400 times)
8 and FIG. 8 (magnification: 1000 times). 7 and 8, the lower substantially semicircular or substantially quarter circular black portion indicates the exposed surface of the aluminum alloy base material, and the upper portion indicates the thermal spray coating. Further, in FIGS. 7 and 8, it can be seen that an interfacial melt solidification layer having a structure different from those of the sprayed film and the base material is formed in the interface region between the base material and the sprayed film. This is presumed to be an aluminum-copper-silicon eutectic structure or a structure containing a eutectic for the reasons described above. The average thickness of this interfacial melting and solidification layer was about 20 to 100 μm.

In FIGS. 7 and 8, the interfacial melt solidification layer also enters the minute gaps between the black portions constituting the aluminum alloy base material to fill the minute gaps.
It is presumed that the interfacial melting solidified layer was generated by once melting and then solidifying. Further, in FIG. 6 as well, since the interfacial melting solidification layer has surely entered the concave portion on the exposed surface of the base material, it is presumed that the interfacial melting solidification layer was produced by once melting and solidifying.

A test for examining the adhesion of the thermal sprayed film after the above heat treatment was conducted, and the test result is shown in FIG. The number of test pieces was 10. As shown in FIG. 9, in the example, the adhesion of the sprayed film was about 8 kg / cm ² . In the comparative example before the heat treatment, the adhesion of the sprayed film was as small as about 5 kg / cm ² . As described above, in the example, the adhesion of the sprayed film was significantly improved as compared with the comparative example. Moreover, the variation α1 in the adhesive force of the sprayed film was also greatly reduced (about one third) as compared with the variation α2 in the comparative example. From this, it can be seen that the formation of the interfacial melting and solidification layer is very advantageous for improving the adhesive force of the sprayed film and reducing the variation in the adhesive force.

In the test for examining this adhesion, a rectangular test piece W (L1 = 8 m) made of an aluminum alloy shown in FIG.
m, L2 = 5 to 8 mm, L3 = 1 mm), and the sprayed film W10 was laminated on the test piece W. FIG. 11 shows a test apparatus. The test apparatus includes a base 10, a holding unit 11, a load 12, and a bolt 13. Then, with the bolt 13 fastened and the test piece W held by the holding portion 11, the load 12 is moved in the direction of the arrow Y1 to press the load 12 against the sprayed film W10, thereby applying a shearing force to the sprayed film W10. I went.

Example 2 In this example, JIS-AC, which is an aluminum-silicon-magnesium alloy as a base material, is used.
4C alloy is used. Also, copper-nickel-silicon powder (atomized powder, -150 mesh,
Copper-10 wt% nickel-3% wt silicon) is used. Then, copper-nickel-silicon powder is sprayed on the exposed surface of the shot-blasted base material, and a first sprayed film (thickness 100 μm) is laminated. The thermal spraying condition of the first thermal spray coating is O ₂
= 42 liters / min, propylene = 40 liters /
min, air = 60 liters / min, powder supply amount = 8
It is 0 g / min.

Next, iron-based powder (atomized powder, -280 mesh, iron-1.0 wt% carbon) as a thermal spray material.
Is sprayed onto the first sprayed film, and the second sprayed layer (average thickness 50
0 μm) was laminated. The spraying condition of the second sprayed film is O ₂ = 4
0 liter / min, propylene = 38 liter / mi
n, air = 50 liter / min, powder supply amount = 90 liter / min. The base material on which the first sprayed film and the second sprayed film are formed is charged into a soaking type heating furnace, and 530
Heated at ℃ × 2hr. After that, as a result of examining the cross section of the interface between the sprayed coating and the base material, it was confirmed that an interface melt-solidified layer of 20 to 100 μm was formed at the interface. It is considered that this interface melt-solidified layer has an aluminum-copper-silicon eutectic structure or a structure containing a eutectic as in the case of Example 1.

Further, also in this example, the same test as in Example 1 was conducted to measure the adhesion, and it was confirmed that the adhesion of the sprayed film was improved and the variation in the adhesion was reduced. (Example 3) In this example, an AC8P alloy is used as the base material. Then, tin powder (atomized powder, -350 mesh, purity 9
9%) is sprayed on the exposed surface of the base material, and a first sprayed film (average thickness 50 μm) is laminated. The thermal spraying condition of the first thermal sprayed film is O ₂ =
38 liters / min, propylene = 36 liters / m
in, air = 50 liters / min, powder supply amount = 80
Gram / min. Next, the iron-based powder used in Example 2 is sprayed and a second sprayed film (average thickness 500 μm) is laminated. The base material on which the first sprayed film and the second sprayed film are formed is charged into the above-mentioned soaking type heating furnace, and the temperature is 240 ° C. × 2 hr.
Heated. As a result of investigating the cross section of the interface between the sprayed coating and the base material, it was confirmed that an interface melt-solidified layer (aluminum-tin alloy layer) having an average thickness of 10 to 50 μm was formed at the interface. Further, in this example, as in the case of Example 1, it was confirmed that the adhesive force of the sprayed film was improved and the variation in the adhesive force was decreased.

In particular, when the thermal spray coating is made of copper, the copper-aluminum alloy is kept near the solution treatment temperature (generally 510 to 525 ° C.) during the T6 and T7 treatments of the aluminum alloy constituting the base material. Since the melting point (eutectic temperature) of the system corresponds, the heating in the solution treatment and the heating in the heat treatment for improving the adhesion of the sprayed film can be combined. When the sprayed coating is made of aluminum, the heating temperature in the metallurgical joining process exceeds 500 ° C, so not only the metallurgical joining effect due to the interfacial melting and solidification layer but also the effect of relaxing residual stress generated in the sprayed coating. Can be expected. Therefore, when machining the sprayed film, when using the sprayed film, the effect of further enhancing the peeling resistance of the sprayed film can be expected.

(Application Example) FIGS. 12 and 13 show an application example applied to the ring groove 110 of the piston 100 of the internal combustion engine. FIG. 12 schematically shows the manufacturing process, and FIG. 13 shows the piston 100 in a state where the sprayed coating 200 laminated on the ring groove 110 is machined. In this example, as shown in FIG.
An aluminum alloy (AC8A) piston 100 having a ring groove 110 is used. The ring groove 110 has a shape that expands toward the outer periphery, and the expansion surfaces 110 a, 1
10b is provided. Then, the powder spray material 140 is sprayed on the entire circumference of the ring groove 110 of the piston 100 by the spray gun 150. Then, after undergoing the above-mentioned heat treatment, the sprayed coating 200 is set to a predetermined shape and size by machining. Even when the sprayed film 200 is laminated in the ring groove 110 of the piston 100 in this way, the life of the sprayed film 200 can be extended, which is advantageous for securing the output of the internal combustion engine. Although this application example is applied to the piston 100, it may be applied to the sliding surface of the cylinder bore of the internal combustion engine.

[0031]

According to the first aspect of the present invention, the interfacial melting solidification layer formed in the interface region between the base material made of an aluminum alloy and the thermal spray coating can enhance the metallurgical bondability of the thermal spray coating to the base material. The adhesion of the sprayed film can be improved. Therefore, peeling of the sprayed film can be reduced or avoided.

According to the second aspect, a thermal spray material containing an alloying element capable of forming a molten liquid layer having a melting point lower than that of the aluminum alloy forming the substrate can be used to form the molten liquid layer after the thermal spraying treatment. After heating to a temperature range and forming a local melt layer in the interface area, the interface melt-solidified layer is formed by cooling and solidifying this, so that the metallurgical bondability at the interface between the sprayed film and the base material is improved. As a result, the adhesion of the sprayed film is improved.

[Brief description of drawings]

FIG. 1 is a binary system phase diagram of aluminum exhibiting a eutectic reaction and other elements.

FIG. 2 is a configuration diagram schematically showing a form in which a sprayed film is laminated on a base material.

FIG. 3 is a configuration diagram schematically showing another embodiment in which a thermal spray coating is laminated on a base material.

FIG. 4 is a configuration diagram schematically showing an internal structure of a sprayed film.

FIG. 5 is an optical microscope photograph according to a comparative example.

FIG. 6 is an optical micrograph according to an example.

FIG. 7 is an electron micrograph according to an example.

FIG. 8 is an electron micrograph according to an example.

FIG. 9 is a graph showing the adhesion of the sprayed film.

FIG. 10 is a schematic perspective view of a test piece used in a test for examining adhesion.

FIG. 11 is a configuration diagram of a test device used in a test for examining adhesion.

FIG. 12 is a configuration diagram showing a thermal spraying process.

FIG. 13 is a side view of a piston having a sprayed coating formed on a ring groove.

[Explanation of symbols]

In the figure, 100 is a piston, 110 is a ring groove, 2, 3
Reference numerals a, 3b and 200 denote sprayed films.

Claims (2)

[Claims] 1. A base material made of an aluminum alloy having an exposed surface and a sprayed film laminated on the exposed surface of the base material, and melt-solidified in an interface region between the sprayed film and the base material. A sprayed film adhesion structure characterized in that an interfacial melt solidification layer is formed. 2. A base material made of an aluminum alloy and a thermal spray material containing an alloying element capable of forming a molten liquid layer having a melting point lower than that of the aluminum alloy constituting the base material are used. A thermal spraying step of laminating a thermal spray coating on the exposed surface of the material, and heating the thermal spray coating at least in a temperature range where the molten liquid layer can be formed after the thermal spray treatment, thereby forming the thermal spray coating and the base material. By forming a local melt layer in the interface region and then cooling, a melt-solidified interface melt-solidified layer is formed in the interface region between the sprayed film and the substrate, and metallurgical bonding in the interface region. A method for improving adhesion of a sprayed coating, which comprises sequentially performing a metallurgical bonding step for improving the property.