JP3009503B2 - Surface treatment member and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated member having an aluminum nitride layer having excellent adhesion on an aluminum alloy surface and a method for producing the same.

[0002]

2. Description of the Related Art Aluminum or an aluminum alloy (hereinafter referred to as aluminum, etc.) has a low Vickers hardness (Hv) of about 200 and is poor in wear resistance.
Conventionally, surface treatment techniques have been developed to improve these properties. However, aluminum and the like have a strong affinity with oxygen in the air and easily bond with oxygen to form an extremely stable and dense layer of thin alumina (Al ₂ O ₃ ). It is difficult to diffuse and infiltrate the surface hardening element or to form a hard film having good adhesion. Therefore, surface treatment methods such as anodic oxidation or chrome plating are limited. However, the hardness of this anodic oxide film varies depending on the processing conditions, but Hv varies from 200 to 1000, and does not always have sufficient wear resistance. In addition, there is a disadvantage that the film is easily peeled off even if Cr plating is performed.

[0003] Aluminum nitride itself is a material that is stable up to a very high temperature, has an Hv of about 1400, has excellent wear resistance, high thermal conductivity, and excellent electrical insulation.

[0004] Aluminum also has a strong affinity for nitrogen, and at temperatures above the melting temperature of aluminum, easily bonds with nitrogen to form aluminum nitride. A method has been reported in which a part of a member such as aluminum is heated to a temperature higher than the melting point of aluminum by utilizing this property, and aluminum nitride is formed on the surface of aluminum or the like by a method of reacting with nitrogen (melting method) ( JP-A-56-25963). However, in the melting method, there is deformation of the member itself with melting,
Since the surface layer on which the aluminum nitride layer is formed is a mixed layer of aluminum nitride and aluminum, Hv is also 200.
Below and low.

On the other hand, there is a method in which aluminum nitride is formed on the surface of aluminum or the like by reactive sputtering or vapor deposition. However, adhesion between the layer and the base material is poor due to mechanical or intermolecular bonding. In addition, there is a problem that mass processing is difficult and the processing cost is high.

As a method capable of forming an aluminum nitride layer which can be processed in a large amount, does not melt the material to be processed, and has excellent wear resistance, an ion-implanting method which has been conventionally used for nitriding iron-based metallic materials has been used. Attempts have been made to apply the nitriding method, but it has been difficult because of the alumina layer formed on the surface of the sample.

The inventors of the present invention have performed a pre-sputtering process using a mixed gas with a rare gas to which argon, a small amount of nitrogen or the like has been added before the nitriding treatment, so that the surface of aluminum or the like has high hardness and high resistance. The inventors of the present invention invented an ion nitriding method capable of forming an aluminum nitride layer having excellent wear properties (Japanese Patent Application Laid-Open No. Sho 60-211061 and Japanese Patent Application No. 63-15045). By this method, it has become possible to form an aluminum nitride layer on most aluminum practical alloy surfaces. However, if an attempt is made to increase the thickness of the aluminum nitride layer, the difference in thermal expansion between the aluminum alloy base material and the aluminum nitride layer (the thermal expansion coefficient of the former is about 26 × 10 ⁻⁶ / ° C., and that of the latter is 5 × 10 ⁻⁶ / ° C.) ), The layer was easily peeled off during the cooling process after the treatment, and it was difficult to obtain a thick aluminum nitride layer. In addition, if an attempt is made to increase the thickness of the nitrided layer without peeling, it has been necessary to perform the nitriding treatment at a lower temperature for a long time.

In order to more effectively improve the wear resistance of a member having a low hardness such as aluminum, it is important to make the surface hardened layer thicker. It is practically important to form a film on a surface of aluminum or the like with good adhesion. In particular, when used under a high load for a long time, it becomes even more important.

[0009]

The inventors of the present invention have conducted intensive research and conducted various systematic experiments in order to solve the above-mentioned problems of the prior art. As a result, the present inventors have achieved the present invention. is there. That is, an object of the present invention is to provide a surface-treated member which is excellent in adhesion to an aluminum alloy base material even when a thick aluminum nitride layer is formed and does not cause peeling of the layer, and a method of manufacturing the same.

[0010]

Means for Solving the Problems (Configuration of the First Invention) First
The surface-treated member of the invention (the invention according to claim 1) includes an aluminum alloy base material containing at least one element of group 4B, 5B, 7B, or 8 whose diffusion coefficient in aluminum is smaller than the self-diffusion coefficient of aluminum; An aluminum nitride layer formed on the surface thereof and fine particles of the intermetallic compound of the element dispersed and formed in a large number in the vicinity of a boundary between the base material and the aluminum nitride layer.

(Structure of the Second Invention) In the method of manufacturing a surface-treated member according to the second invention (the second invention), the diffusion coefficient in aluminum is smaller than that of aluminum by 4B, 5B, 7B. Performing a nitriding treatment on an aluminum alloy base material containing at least one group 8 element to form an aluminum nitride layer on the surface of the base material, by nitriding near a boundary between the base material and the aluminum nitride layer; A large number of fine particles of an intermetallic compound of an element are dispersed and formed.

[0012]

The surface-treated member according to the first aspect of the present invention has fine particles of an intermetallic compound of an alloy element added to the aluminum alloy near the boundary between the aluminum alloy base material and the aluminum nitride layer. It is characterized in that it is dispersed in a large number, and the intermetallic compound remarkably improves the adhesion of the aluminum nitride layer. The reason is not clear at present, but the vicinity of the boundary between the aluminum nitride layer and the base material, in which a large number of finely precipitated intermetallic compounds are dispersed, becomes intricate, and the anchor (interpolation effect)
It is estimated that the adhesion of the aluminum nitride layer is enhanced.

(Function of the Second Invention) In the method for manufacturing a surface-treated member according to the second invention, fine particles of an intermetallic compound of an alloy element added to an aluminum alloy base material are nitrided to form the base material and aluminum nitride. It is characterized in that it is dispersed and deposited near the boundary with the layer.

Elements belonging to Groups 4B, 5B, 7B and 8 whose diffusion coefficient in aluminum is smaller than the self-diffusion coefficient of aluminum have a relatively small solid solubility limit in the α phase of 2% by weight or less. Therefore, when the element which was dissolved in the α phase before the nitriding treatment was consumed in the base material immediately below the aluminum nitride layer during the nitridation process along with the formation of the aluminum nitride layer, the element was converted into the aluminum nitride. Since the amount of solid solution is extremely small, the composition of these elements relatively increases in the vicinity, but since the diffusion rate of these elements in aluminum is slower than the self-diffusion rate of aluminum, the amount of diffusion into the base material is small. Is concentrated near the boundary between the aluminum nitride layer and the base material. Furthermore, since the solid solubility limit of the element in the α phase is as small as 2% by weight or less, the concentration easily proceeds until the solid solubility limit is exceeded, and the element is finely precipitated as an intermetallic compound near the boundary. In addition, it is considered that the intermetallic compound precipitated in the process of nitriding has a certain degree of metallic bonding with the aluminum alloy and aluminum nitride as the base material during the process of deposition and growth, which also improves the adhesion. Presumed to be a factor.

[0015]

【The invention's effect】

(Effect of the First Invention) In the surface treatment member of the first invention, since a large number of fine particles of an intermetallic compound are dispersedly formed near the boundary between the aluminum alloy base material and the aluminum nitride layer, the aluminum alloy base of the aluminum nitride layer is formed. The adhesion to the material is extremely excellent, and the aluminum nitride layer is not peeled off even when the thickness is 5 μm or more.

The aluminum nitride layer has a Vicker hardness of 1
Although it has excellent wear resistance since it is as high as 000 to 1600, when it has a thick layer, the wear resistance particularly under a high load is improved.

(Effect of the Second Invention) In the method for producing a surface-treated member according to the second invention, fine particles of an intermetallic compound are formed by nitriding treatment, so that the dispersion state of the fine particles can be easily controlled and the aluminum nitride layer can be easily formed. Adhesion can be further improved.

[0018]

【Example】

(Specific Example of First Invention) A specific example that further embodies the first invention will be described.

The aluminum alloy used in the surface treatment member according to this embodiment is an element belonging to Group 4B, 5B, 7B or 8 as an alloy element. The aluminum alloy has a diffusion coefficient smaller than the self-diffusion coefficient of aluminum and an α phase. Elements such as titanium, vanadium, manganese, nickel, iron and the like having a solid solubility limit of 2% by weight or less are used. These elements are the main constituent elements of the intermetallic compound. The amount of the alloying element added is set to 0.1.
The content is preferably 0.01 to 5% by weight, and if it is 0.01% or less, the amount of the intermetallic compound becomes small, so that the effect of improving the adhesion becomes insufficient. It is not preferable because the toughness of the alloy base material is impaired and the castability is impaired during the production of the alloy. If the aluminum alloy contains one or more of the above-mentioned elements, the adhesion of the aluminum nitride layer is improved. Therefore, in addition to these alloy elements, a small amount of an element such as magnesium, zinc, copper, or silicon may be added.

The intermetallic compound formed near the boundary between the aluminum nitride layer and the member is Ti (Ti).
Al ₃ , zirconium (Zr), hafnium (Hf),
Thorium (Th), vanadium (V), niobium (N
b), tantalum (Ta), manganese (Mn), nickel (Ni), and iron (Fe) for ZrAl ₃ and HfA, respectively.
l ₃ , ThAl ₃ , VAl ₆ , NbAl ₃ , TaAl ₃
And when two or more of the above elements are contained,
When other elements are added to the alloy, these elements may form a solid solution in the intermetallic compound and may be a ternary or more intermetallic compound. The shape of the intermetallic compound may have a circular cross section or may have irregularities, and is not particularly limited. Its size is preferably 0.1 to 20 μm in average diameter, and if it is out of this range, the anchor effect will be small. The distance between the grains is desirably about the above-mentioned average diameter. If the distance is smaller than 0.1 μm, the diffusion of aluminum is inhibited, and the nitriding reaction is suppressed.
If it is larger than μm, the anchor effect becomes small, which is not preferable. Among the alloying elements, Ti and V are particularly excellent in improving adhesion since the amount of the intermetallic compound which precipitates particularly strongly tends to be large.

The aluminum nitride layer formed on the surface of the aluminum alloy base material is wurtzite type aluminum nitride (AlN).
６０60 at% and the nitrogen content is 40４０50 at%. Instead of aluminum, magnesium or zirconium,
Oxygen or carbon may be partially substituted for nitrogen. The thickness of the layer depends on the application and is not particularly limited.
However, when abrasion resistance is required under a load, the thickness is desirably 5 μm or more. In order to prevent the peeling, the selection of alloy elements in the aluminum alloy and the connection between the aluminum nitride layer and the base material are performed as in this example. This requires the presence of finely dispersed intermetallic compounds near the boundaries.

(Specific Example of Second Invention) A specific example which further embodies the second invention will be described.

The nitriding method used in the method for manufacturing a surface-treated member of this embodiment is not particularly limited, but ion nitriding is preferred. The ion nitriding treatment is performed by the following operation using, for example, the apparatus shown in FIG. An aluminum alloy member, which is a sample, is provided on a base or the like provided in a vacuum vessel. After the inside of the vessel is depressurized by a vacuum pump, the temperature of the sample is raised by glow discharge or the like. After the temperature is raised, pre-sputtering is performed on the sample surface as a pretreatment for the ion nitriding treatment. The pre-sputtering is to roughen the surface of the aluminum nitride layer forming portion so as to have a surface property in which the layer is easily formed.
Glow discharge or ion beam sputtering is performed in a rare gas such as argon or helium containing up to 2000 ppm. In pre-sputtering, the pressure in the vacuum vessel is 10 ^{−3 to 5} Torr, and the processing temperature is 550.
It is desirable that the temperature be lower than or equal to ° C. In addition, the ion nitriding treatment is performed by introducing a nitrogen gas or a nitrogen-containing gas into a vacuum vessel for a predetermined time by glow discharge. At that time, the pressure in the vacuum vessel is 10 ^{-1 to} 20 Torr, and the treatment temperature is 300 to 60.
It is desirable to carry out in the range of 0 ° C.

(Example 1) The sample used in this example was pure A
l, Ti, V, Mn, Fe, Ni as alloying elements in Table 1
2 prepared by melting and casting to add the composition shown in
It is an original alloy (diameter 19 mmφ, length 10 mm). Similarly, Cr, Mg, Zn, Si, C
A binary alloy prepared by alloying u was prepared and used as a sample for comparison. As a comparative sample, pure Al and practical alloy J
IS 6061 was also used.

[0025]

[Table 1]

In this embodiment, an ion nitriding apparatus whose schematic diagram is shown in FIG. 1 was used. This apparatus has a stainless steel sealed container 1 and a base 2 provided at the center of the sealed container 1 as main components. This closed container 1 is a lid 1
a and a reactor main body 1b, and a lid 11a has a window 11
The preheating heater 12 is provided on the inner peripheral side of the reaction furnace main body 1b, and a stainless steel anode plate 13 is provided inside the heater. Further, a gas inlet pipe 14 and a gas outlet pipe 15 are provided at the bottom of
A cooling water pipe 16 for sending cooling water and a mercury manometer pressure gauge 17 are attached to the inside.

The gas introduction pipe 14 is connected to a high-purity nitrogen gas cylinder and a high-purity hydrogen gas cylinder (both not shown) via a control valve. The gas pump 15 is connected to the vacuum pump 3.

A DC power supply circuit 4 is formed between the anode 13 and the base 2 serving as a cathode. The DC power supply circuit 4 is current-controlled by an input from a two-color thermometer 41 for measuring the sample temperature, and functions to keep the sample temperature within a certain range.

In the ion nitriding in this apparatus, first, the sample 5 was placed on the base 2 and the sealed container was closed. Then, the pressure of the residual gas was reduced by the vacuum pump 3 until the residual gas pressure became 10 ^-3 Torr. Further, with the preliminary heater 12 while evacuating,
The furnace wall was heated for 30 minutes. Immediately after the heating, argon gas was introduced to ⁴ Torr, the gas was replaced with hydrogen gas, and the pressure was further reduced to 10 ⁻³ Torr. In this manner, the replacement with the argon gas was repeated two or three times to remove the residual oxygen gas in the furnace as much as possible.

Next, hydrogen gas was flowed into the furnace at a reduced pressure of 10 ⁻³ Torr, and the furnace pressure was adjusted to 1.3 Torr while simultaneously evacuating. And both poles 1
A DC voltage of several hundred volts was applied between 3 and 2, discharge was started, and the temperature was increased by ion bombardment. The sample surface is 5
When the temperature reached 00 ° C, the argon gas was stopped.
Argon gas to which 100 ppm of nitrogen gas was added was introduced. The pressure of the argon-nitrogen mixed gas (hereinafter, referred to as a mixed gas) was adjusted to 0.7 Torr, and the discharge was further continued for 1 hour while maintaining the pressure at 0.7 Torr. Thereafter, the introduction of the mixed gas was stopped, and then nitrogen gas was introduced. Gas pressure of nitrogen gas in furnace is 1.4T
The flow rate of the nitrogen gas was adjusted so as to be orr, the temperature of the sample was set to 500 ° C., and the sample was left standing while maintaining the temperature to perform ion nitriding for a predetermined time.

After the ion nitriding treatment, the discharge was stopped, and the sample was cooled under reduced pressure and taken out of the furnace. By repeating this series of operations, the ion nitriding time was variously changed to 2 to 20 hours, that is, a plurality of samples having different nitrided layer thicknesses were obtained. A black layer was formed on the surface of the obtained sample, and as a result of substance identification by X-ray diffraction, it was confirmed that each of these layers was wurtzite-type aluminum nitride (AlN). Among these samples, those treated for a long time to obtain a thick aluminum nitride layer showed peeling. Table 2 shows the maximum thickness (critical layer thickness) of the aluminum nitride layer obtained without occurrence of peeling in appearance.

Ti, V, Mn, Fe, N as alloying elements
Example samples 1 to 7 using i showed a large critical layer thickness. In particular, for Ti and V, an aluminum nitride layer three times or more thicker than pure Al is obtained. Al-Ti and Al-
The cross section of the aluminum nitride layer formed of the V
The results of line analysis performed by PMA are shown in FIGS. 2 and 3, respectively. In both alloys, Ti and V were concentrated in the vicinity B of the boundary between the aluminum nitride layer A and the base material C in the process of ion nitriding, and the maximum concentrations were 0.7 and 0.6% by weight, respectively.
Both exceeded the solid solubility limits of both alloys, 0.55 and 0.2% by weight. In addition, it was observed that a large number of fine particles of an intermetallic compound were dispersed and formed near the boundary between the aluminum nitride layer of each alloy and the base material. Fe-Mn
In the case of the binary alloy, the concentration of Mn was also observed near the boundary, but the adhesion of the layer was slightly inferior since the precipitation amount of the intermetallic compound near the boundary was smaller than in the case of Ti and V.

[0033]

[Table 2]

Further, since the intermetallic compound precipitated and formed in the nitriding treatment contributes to the adhesion, when Fe or Ni is used as an alloying element, the solid solution amount in the α phase is 0.01% by weight. % Or less, the intermetallic compound is considerably present before the ion nitriding treatment, and the amount of the intermetallic compound formed by the ion nitriding treatment is not so large.
No remarkable effect of improving adhesion like Ti and V has been obtained.

A binary alloy containing Cr, Mg, Zn, Si, and Cu (Comparative Samples 1 to 5) and a practical alloy JIS 6
No. 061 (Comparative Sample 7) has a critical layer thickness of aluminum nitride of 4 to 5 μm, which is almost the same as pure Al, and shows almost no effect of improving adhesion. These alloy elements have a higher diffusion rate in Al than the self-diffusion rate of Al, or have a higher solid solubility limit in the α phase, and the binary alloy or the like obtained by alloying these elements is an aluminum nitride layer. This is because almost no intermetallic compound is formed near the boundary between the metal and the base material.
FIG. 4 shows the result of linear analysis of the cross section of the aluminum nitride layer formed of the Al—Cu binary alloy by EPMA.
It can be seen that Cu concentration hardly occurred.

FIGS. 5 to 7 show a scanning electron beam at a portion where the aluminum nitride layer formed when Al-V, pure Al, or Al-Cu is peeled off, that is, near the boundary between the layer and the base material. 1 shows a metal structure by a microscope (SEM). Pure Al for Al-V, which has excellent adhesion,
It can be seen that fine irregularities are formed by an intermetallic compound whose surface is presumed to exhibit an anchor effect as compared with Al-Cu.

Example 2 The sample used in this example was pure A
1 was prepared in the same manner as in Example 1 except that Ti, V, and Mg were added as alloying elements to l so that the composition shown in Table 3 was obtained.
Original, ternary alloy. These samples were subjected to the same ion nitriding treatment as in Example 1, and the critical layer thickness of the aluminum nitride layer in each sample was determined. The results are shown in Table 4. The critical layer thickness of the ternary Al-Mg-Ti, Al-Mg-V alloy is larger than that of the binary Al-Ti, Al-V alloy. This is presumed to be because Mg has a function of increasing the nitridation rate, and thus the enrichment of Ti and V near the boundary between the aluminum nitride layer and the base material was further promoted during the nitridation process.

[0038]

[Table 3]

[0039]

[Table 4]

[Brief description of the drawings]

FIG. 1 is a schematic view of an ion nitriding apparatus according to the present invention.

FIG. 2 is a diagram showing a result of line analysis by EPMA of a cross section of an aluminum nitride layer formed on an Al—Ti binary alloy in Example 1.

FIG. 3 is a diagram showing a line analysis result by EPMA of a cross section of the aluminum nitride layer formed on the Al-V binary alloy in Example 1.

FIG. 4 is a diagram showing a result of line analysis by EPMA of a cross section of the aluminum nitride layer formed on the Al—Cu binary alloy in Example 1.

FIG. 5 is a diagram showing a metallographic structure of the Al—V binary alloy ion-nitrided in Example 1 near the boundary between the aluminum nitride layer and the base material by a scanning electron microscope.

FIG. 6 is a diagram showing a metal structure of a pure Al ionized in Example 1 in the vicinity of a boundary between an aluminum nitride layer and a base material by a scanning electron microscope.

FIG. 7 is a diagram showing the metal structure of the Al—Cu binary alloy ion-nitrided in Example 1 near the boundary between the aluminum nitride layer and the base material, which is observed by a scanning electron microscope.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Closed container 2 Base 3 Vacuum pump 4 Power supply circuit 5 Sample A Aluminum nitride layer B Near boundary C Base material

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C23C 8/36

Claims (2)

(57) [Claims] 1. A method according to claim 1, wherein the diffusion coefficient in aluminum is smaller than the self-diffusion coefficient of aluminum.
B, an aluminum alloy base material containing at least one group 8 element, an aluminum nitride layer formed on the surface thereof, and an intermetallic compound of the element dispersed and formed in the vicinity of a boundary between the base material and the aluminum nitride layer. A surface treatment member comprising fine particles. 2. 4B, 5B, 7 wherein the diffusion coefficient in aluminum is smaller than the self-diffusion coefficient of aluminum.
B, an aluminum alloy base material containing at least one group 8 element is subjected to nitriding treatment, and when an aluminum nitride layer is formed on the surface of the base material, nitriding treatment is performed near the boundary between the base material and the aluminum nitride layer by nitriding treatment. A method for producing a surface-treated member, wherein a large number of fine particles of the intermetallic compound of the element are dispersed and formed.