JP3311767B2 - Sliding material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding material covered with a film having excellent sliding properties and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a base material having been subjected to a surface treatment capable of forming a film having excellent sliding characteristics has been used for a sliding portion of an engine part of an automobile, various mechanical parts, and the like. Conventional surface treatments include nitriding, chromium plating, and molybdenum spraying. However, in recent years, as the use conditions of sliding parts have been increased in speed and load, the sliding properties required of the parts have become increasingly severe, and conventional surface treatments may not be able to cope with them. Therefore, a film having more excellent wear resistance and seizure resistance has been desired.

[0003]

SUMMARY OF THE INVENTION TiN, TiC, Cr
PVD coatings such as N show excellent abrasion resistance and seizure resistance. Titanium nitride and chromium nitride are particularly noticeable as coatings that can be put to practical use, and are used in some mechanical parts and engine parts. I have.

[0004] However, at present, the use conditions of these parts have become more severe, and even with the use of these titanium nitride and chromium nitride films, there have been situations in which the sliding characteristics cannot be said to be sufficient. Therefore, there is a demand for a coating having more excellent wear resistance and seizure resistance. An object of the present invention is to further improve the characteristics of a sliding material coated with a chromium nitride-based hard film having excellent sliding characteristics, and to provide a method for producing the sliding material.

[0005]

The sliding material of the present invention, which achieves the above object, has a chromium: silicon:
Nitrogen = 1: 0.05-1.2: has a composition in the range of 0.1-1.2, and is characterized in that a base material is coated with a coating containing at least chromium nitride and silicon nitride. .
That is, the present invention is characterized in that a film composed of chromium nitride and silicon nitride as essential substances is formed on the surface of the base material.

[0006] Chromium and silicon, which are elements constituting the film, are both elements that easily form nitrides. Therefore, part or all of chromium and silicon can be nitrided, and two kinds of nitrides, chromium nitride and silicon nitride, can be combined in the coating. When the chromium content is 1, the composition of the elements of the composite coating is chromium: silicon: nitrogen = 1: 0.05 to atomic ratio.
1.2: 0.1 to l. It is limited to the range of 2. When the atomic ratio of silicon to chromium is less than 0.05, the effect of silicon nitride formation is not remarkable. When the atomic ratio of silicon to chromium exceeds 1.2, the hardness of the film increases, but the adhesion of the film decreases. And the tendency to peel off increases. When the atomic ratio of nitrogen to chromium is 0.1 or less, the generation of chromium nitride is reduced, so that the hardness is low and the wear resistance is low. The thickness of the film is desirably 1 to 50 μm.

[0007] In a film having the above composition, metal Cr or Si which does not become nitride may be present. Such metal Cr has slightly lower corrosion resistance than nitride, but changes in the thermal expansion coefficient and crystal structure of the film at the interface with the base material are smaller than when the film is made of a nitride single phase. This enhances adhesion. As described above, although metals Cr and Si have advantages and disadvantages, they are not as comprehensive as chromium nitride and silicon nitride. Therefore, it is preferable not to actively generate them. In addition, the upper limit of the generation amount is determined by the content of nitrogen, but it is preferable that the upper limit is not more than 95% in the film. Further, an alloy layer made of chromium and silicon is preferably provided as an underlayer between the base material and the film containing chromium nitride and silicon nitride, preferably in a thickness of 0.1 to 2 μm.
By providing a thickness of m, changes in the coefficient of thermal expansion and the crystal structure can be reduced, and the adhesiveness of the film can be increased due to its excellent flexibility. The atomic ratio between chromium and silicon in the underlayer is preferably 1: 0 to 1.2.

In the present invention, the sliding material can be produced by bringing a substrate into contact with a gas phase in which chromium, silicon and nitrogen are mixed by a PVD method. The substrate material to be coated is selected from iron-based materials, aluminum-based materials, and titanium-based materials depending on the application. The PVD method described in detail below is based on CVD (Chemical Vapor Deposition).
Although it is similar to low-temperature treatment than the method and the like, since heat input due to the evaporation phenomenon is inevitable, it is desirable to use a heat-resistant iron-based material as a base material if possible.

When a gaseous plasma is generated by mixing nitrogen with chromium and silicon vapor, chromium is ionized and reacts with nitrogen ions to form chromium nitride. Similarly, silicon is ionized and combined with nitrogen ions to generate silicon nitride. As a result, a chromium nitride + silicon nitride film is formed on the substrate surface. At that time, when the supply of nitrogen gas is small, unreacted chromium and silicon are left in addition to chromium nitride and silicon nitride.

The PVD method is a technique for forming a film, and can be basically classified into three methods: vapor deposition, sputtering, and ion plating. In particular, in the present invention, the reactive ion plating method of depositing a chromium nitride + silicon nitride film on a substrate by reacting a vapor substance of chromium and silicon with nitrogen is most preferable.

As a method for obtaining a mixed vapor of chromium and silicon, chromium and silicon may be evaporated individually, or a chromium-silicon alloy may be evaporated. However, separate evaporation requires multiple evaporation sources such as an evaporation source and an electron beam, which makes the equipment complicated and bulky, and complicates the operation of the machine. Is desirable.

As for the evaporation method, a method of irradiating a high-energy beam such as an HCD gun or an electron beam to an alloy evaporation source to dissolve the alloy and obtain steam is performed by simultaneously dissolving chromium and silicon having different vapor pressures. High chromium evaporates first, and the composition ratio of chromium and silicon is not stable, and it is difficult to control the film composition. In contrast, the cathodic arc plasma ion plating method and the sputtering method can simultaneously evaporate the alloy using the alloy material as a cathode and a target, so that the composition of the evaporating material can be easily transferred to the film, and the composition can be stably adjusted. Can be maintained. Here, sputtering means that argon gas collides with a target and strikes and coats target particles, so that vaporized particles fly out of the cathode with high-density energy due to the cathodic arc. Energy is low and adhesion is low.

That is, in view of industrial production, the most preferred method for producing the material of the present invention is a cathodic arc plasma ion plating method using a chromium-silicon alloy having a desired composition as a cathode. According to this manufacturing method, a predetermined composition of chromium nitride-silicon nitride can be stably maintained with a small and simple apparatus, and a film having high adhesion can be easily formed.

In forming the film, the amount of nitrogen gas is gradually increased toward the film surface from the base material, or the metal ratio to the nitride in the composite film is high at the boundary with the base material, and gradually increases toward the film surface. By lowering the adhesion, the adhesion of the composite coating is further enhanced. That is, if ion plating is performed before introducing nitrogen gas, a base layer of chromium and silicon is formed on the base material. The underlayer has a good coefficient of thermal expansion and is not easily affected by thermal stress, so that it has good adhesion and high flexibility.

Instead of forming the underlayer, the amount of nitrogen gas introduced may be reduced to start ion plating, and thereafter the amount of nitrogen gas introduced may be gradually increased. When the ion plating is continued by introducing nitrogen gas gradually without forming the underlayer or when the thickness of the underlayer reaches a predetermined thickness, a part of the evaporated chromium and silicon are respectively changed to chromium nitride and nitride. Convert to silicon. The conversion rate is low when the nitrogen gas partial pressure is low, and the conversion rate increases as the nitrogen gas partial pressure gradually increases. As described above, when the hard film layer is formed with a continuous change in the amount of nitrogen from the underlayer having excellent adhesion and flexibility, it is effective in preventing peeling of the film.

[0016]

[Action] Although chromium nitride exhibits excellent seizure resistance and wear resistance even in a single phase, it further improves the sliding characteristics of the film by incorporating silicon nitride, which has excellent sliding characteristics, into the film. I do.

[0017]

The present invention will be described in detail with reference to the following examples. Example 1 In this example, a substrate made of SKD61 was used, and a chromium nitride + silicon nitride film was formed on the surface thereof by 5 μm PVD. The PVD treatment used a cathode arc plasma type ion plating apparatus. The substrate was washed with Freon to remove dirt adhering to the surface, sufficiently cleaned, and inserted into a vacuum chamber of an ion plating apparatus.

After the chamber is evacuated until the pressure in the chamber reaches 1.3 × 10 ⁻³ Pa, it is heated to 300 to 500 by a heater built in the ion plating apparatus.
C. to release the gas contained in the substrate.
Cooled to ° C. When the pressure in the chamber becomes 4 × 10 ⁻³ Pa or less, an arc discharge is generated on the surface of the alloy target made of chromium-silicon as a cathode to cause chromium ions and silicon ions to fly out. At this time, a bias voltage of -700 to -900 V is applied to the substrate, and metal ions ejected from the cathode are made to collide with the substrate surface with high energy, that is, oxide removal and activation treatment of the substrate surface are performed by so-called bombard cleaning. Was.

[0019] Then while depositing on the substrate surface of metal ions to reduce the bias voltage, a nitrogen gas was introduced into the chamber and ionized nitrogen by passing through the plasma, 1.2 × 10 ^-1 to 1 A bias voltage of -10 to -100 V was applied at a pressure of about 0.6 Pa to form an ion plating film on the substrate surface. After forming a predetermined film thickness, the substrate was cooled in a vacuum chamber to 200 ° C. or lower, and then the substrate was taken out of the chamber.

A film having a thickness of 5 μm was formed by the above method. Further, by the same method, the composition, the atomic ratio of each element, and the hardness of the films formed under various atmospheric pressures while changing the nitrogen flow rate using the chromium-silicon alloy evaporation source having the changed composition ratio were examined. The composition and atomic ratio were determined by XPS
(X-ray photoelectron spectroscopy). Each spectrum of chromium 2P3, silicon 2P, and nitrogen 1S electrons was used for analysis. Table 1 shows the measurement results of the atomic ratios of the constituent elements of the film. The numbers in the table indicate the atomic ratio of silicon to nitrogen when chromium is 1.

[0021]

[Table 1]

As a result of comparing the energy values of the respective spectra and analyzing the composition, in the film, a part of chromium and silicon was combined with nitrogen to form chromium nitride and silicon nitride, respectively, and the amount of reactive nitrogen gas was small. Below, it was confirmed that some of the chromium and silicon were unreacted and existed in their respective metallic states. Cr: Si = 80 at%: 20
Table 2 shows the composition ratios of Cr and Si in the films formed under various atmospheres by changing the nitrogen flow rate using an evaporation source of at%. For Cr and Si in the coating, the ratio of metal and nitride not reacting with nitrogen was shown.

[0023]

[Table 2] Even when the Cr: Si ratio of the evaporation source was changed from the above value, the ratio of each metal and nitride was almost the same as in Table 2. Table 3 shows the measured values of the microhardness of the coating of the present invention. The measurement was carried out using a micro Vickers hardness tester with a load of 10 g and a holding time of 15 seconds.

[0024]

[Table 3] From the above results, the coating of the present invention has a microhardness of 1100 or more, and from this value, it can be seen that the wear resistance against frictional wear is good.

Example 2 In this example, the seizure resistance of the material of the present invention was evaluated. SK
Using a test piece made of D61 material and having three pin-shaped projections 10 (see FIGS. 1 and 2) of 5 mm long × 5 mm wide × 5 mm high arranged at equal intervals on a concentric circle, a test piece was formed on a square end face of 5 mm square. A test piece having a coating of the present invention formed with a thickness of 5 microns was prepared,
A seizure resistance test was performed with an ultra-high pressure wear tester. The coating of the test piece was formed by the method described in Example 1,
The atomic ratio was chromium: nickel: nitrogen = 1: 0.22: 0.82. Further, the compound ratio of Cr and Si is set to X
As a result of examination by PS, metal Cr: CrN = 75: 25,
Metal Si: Si nitride = 45: 55.

As a comparative example, a similar test was performed using a test piece having a 100-micron-thick chromium plating film and a 5-micron-thick chromium nitride film formed by an ion plating method on a 5 mm square end face of the test piece. Was.

The apparatus and test conditions of the ultra-high pressure wear tester used in this test are as follows. The test equipment is shown in FIGS. 1 and 2.
FIG. 2 is a cross-sectional view taken along the line AA of FIG. 2 and schematically shows a main part. The disk 2 (removably mounted on the stator holder 1) has a diameter of 80 mm and a thickness of 10 mm and has been polished. Lubricating oil is injected into the center of the counterpart material) from the back through the oil inlet 3. A pressing force P is applied to the stator holder 1 with a predetermined pressure toward the right in the figure by a hydraulic device (not shown). A rotor 4 is opposed to the disk 2, and is rotated at a predetermined speed by a driving device (not shown). A test piece 5 is slidably attached to the disk 2 on the rotor 4 with a pin-shaped projection 10 having a square surface of 5 mm square having a surface treatment layer formed thereon as a sliding surface.

In such an apparatus, a predetermined pressing force P is applied to the stator holder 1 so that the disk 2 and the pin-shaped projections 10 of the test piece 5 come into contact with each other with a predetermined surface pressure.
The rotor 4 is rotated while oil is supplied from the oil inlet 3 to the sliding surface at a predetermined oil supply speed. The pressure acting on the stator holder 1 is gradually increased at regular intervals, and the torque T generated on the stator holder 1 by the friction between the test piece 5 and the counterpart disk 2 due to the rotation of the rotor 4 is changed to the stainless steel fiber 6.
, And the change is read by a dynamic strain meter 8 and recorded on a recorder 9. Assuming that the seizure occurred when the torque T sharply increased, the quality of the seizure resistance is judged based on the contact surface pressure at this time.

The test conditions are as follows. Friction speed: 8 m / s Counterpart material: Aluminum alloy (A390) Contact surface pressure: After leveling at 20 kg / cm ² , increase pressure by 10 kg / cm ² until seizure occurs. Hold at each contact pressure for 3 minutes. Lubricating oil: Motor oil # 30, oil temperature 80 ° C, supply amount 250cc / min

As a result of the test, the material of the present invention showed a contact surface pressure of 373.
baking in kg / cm ² occurs, but it is comparative materials seizure surface of the chromium plating pressure 253 kg / cm ² or more, that the seizure resistance is superior with respect to 283kg / cm ² of titanium nitride film confirmed.

Example 3 A wear test of the material of the present invention was carried out using a Kaken abrasion tester. Substrate material is SKD-61 and the shape is 5 × 5mm
× Using a test piece having a length of 20 mm and one end in the longitudinal direction having a curved surface of R6 mm, a curved surface portion of the end was coated with the coating of the present invention to a thickness of 10 μm by the method described in Example 1. The element ratio of the coating is chromium: silicon: nitrogen = 1: 0.22:
It was 0.82.

As a comparative example, a thickness of 100
A similar test was performed using a test piece on which a 6-μm-thick chromium nitride film was formed by a chromium plating of μm and an ion plating method.

In the test, the tip R of the surface-treated test piece was
The curved surfaces are brought into line contact with the outer peripheral portion of the counterpart material whose portion is processed into a drum shape, a predetermined load is applied, and the member rotates at a predetermined speed. Lubrication was performed by supplying a constant amount of motor oil to the contact portion. The test conditions are as follows. Sliding partner material: FC25 material Friction speed: 8 m / sec Friction distance: 150 km Contact load: 4 kg Lubrication conditions: lubricating oil Motor oil # 30, oil temperature 80
Table 4 shows the measurement results of the film wear amount and the counterpart material wear amount. The results were expressed as relative values with the test result of the chromium plating film as 100.

[0034]

[Table 4]

From Table 4, it is clear that the coating of the present invention has significantly improved abrasion resistance as compared with the conventional coating of chromium plating, and that the coating of the present invention is at least as good as compared with chromium nitride. That is, as compared with the chromium plating film as a comparative material, the material of the present invention has a significantly reduced film abrasion amount of about 1/100, and is reduced by about 20% from the abrasion amount of the sample in which chromium nitride is ion-plated. . The wear of the mating material is also significantly reduced with respect to the chromium plating film, and is substantially the same as that of the chromium nitride product.

[0036]

As is apparent from the above description,
The present invention provides a composite hard material having excellent seizure resistance and abrasion resistance by coating a composite film of chromium nitride and silicon nitride on a substrate surface, as compared with a chromium nitride film, and A method capable of stably producing such a composite hard material by a simple process can be provided.

The material of the present invention is suitable for engine parts such as piston rings and cam followers, as well as sliding parts such as air compressor parts such as shoe disks and cutting tools.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a part of an ultra-high pressure wear tester crushed.

FIG. 2 is a sectional view taken along the line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stator holder 2 Disk (counterpart material) 3 Lubrication port 4 Rotor 5 Test piece 6 Stainless steel fiber 7 Load cell 8 Dynamic strain gauge 9 Recorder 10 Pin-shaped protrusion of test piece (5 mm square)

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 F16J 1/02

Claims (4)

(57) [Claims] 1. A composition element having an atomic ratio of chromium: silicon: nitrogen = 1: 0.05 to 1.2: 0.1 to 1.2, and at least chromium nitride and nitride A sliding material comprising a base material coated with a film containing silicon. 2. The method according to claim 1, wherein the coating is made of chromium nitride, silicon nitride, metallic chromium, and metallic silicon, and the ratio of chromium nitride to silicon nitride increases from the surface of the base material toward the surface of the coating. The sliding material according to 1. 3. The sliding material according to claim 1, wherein an underlayer made of chromium and silicon is interposed between the coating and the base material. 4. The chromium: silicon =
1: Using an alloy consisting of 0.05 to 1.2 as an evaporation source, plasma of chromium and silicon atoms is ejected from the cathode surface by a cathode arc plasma type ion plating method,
A method for producing a sliding material, comprising coating a film on a substrate to which a bias voltage has been applied while introducing nitrogen gas into the plasma.