JP3212636B2 - Sliding material - 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 characteristics.

[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, chrome plating,
Molybdenum spraying and the like. However, in recent years, as the use conditions of sliding parts have 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. There is a demand for a film having abrasion resistance and seizure resistance.

In response to such a request, PVD (Phys.
It has been proposed to coat a sliding surface of a sliding member with a film such as a metal nitride or a metal carbide by an ical vapor deposition method.

[0004] PVD films such as TiC and CrN show excellent abrasion resistance and seizure resistance. Titanium nitride, chromium nitride, and the like are particularly attracting attention as films that can be put to practical use.

[0005] However, although these ceramic films have high hardness and are superior to conventional surface treatments such as chromium plating in abrasion resistance and seizure resistance, titanium nitride has low adhesion to a substrate and has a thickness of 3 μm or more. It is not easy to coat a thick film. Chromium nitride is inferior to titanium nitride in abrasion resistance and corrosion resistance.
For this reason, titanium nitride has a problem that, although it is excellent in wear resistance and corrosion resistance, these properties cannot be sufficiently exhibited when formed into a film.

[0006] In order to improve the adhesion of the ceramic film, it is necessary to undercoat with a dissimilar metal film having strong adhesion to both the substrate and the film, or to undercoat a pure metal film of a metal element forming the ceramic film. Attempted. Furthermore, Japanese Patent Publication No. 53-19325
It is also known to change the composition of the carbide or nitride of Ti or Zr, that is, the content of N or C, in the thickness direction of the coating as in the above.

Further, in Japanese Patent Application Laid-Open No. 62-188856, the present applicant has proposed a film in which the ratio between chromium nitride and metallic chromium is changed. However, these measures for improving the adhesion complicate the manufacturing process of the composite hard material coated with the hard coating.

Accordingly, an object of the present invention is to provide a composite hard material coated with a chromium-nickel-nitrogen based coating having excellent adhesion.

[0009]

Therefore, the sliding material of the present invention which achieves the above object has a composition element ratio of chromium: nickel: nitrogen = 1: 0.05-1: 0.1-1 in atomic ratio.
Wherein the base material is coated with a film having chromium nitride and metallic nickel. That is, the present invention is characterized in that a film made of chromium nitride and nickel is formed on the surface of a substrate.

[0010] Of the chromium, nickel and nitrogen constituting the film, nickel is an element which hardly forms nitride, while chromium is an element which easily forms nitride. Therefore, one of the chromium and nickel metal elements can be nitrided, and the other can be compounded in a metal state in the coating. When the amount of chromium is 1, the composition of the constituent elements of the composite coating is chromium: nickel: nitrogen = 1: 0.05 to 1: 0.1 to 1 in atomic ratio.
Is limited to the range. When the atomic ratio of nickel to chromium is 0.05 or less, the effect of nickel on adhesion and corrosion resistance is not remarkable, and when the nickel atomic ratio exceeds 1, the hardness decreases and the abrasion resistance of the coating decreases. 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 1
It is preferably 30 μm.

In the present invention, the above-mentioned sliding material can be manufactured by bringing a substrate into contact with a gas phase in which chromium, nickel and nitrogen are mixed by a PVD method. The material of the base material to be coated is iron-based material, aluminum-based material,
And titanium-based materials depending on the application. The PVD method described in detail below is based on CVD (Chemical Vapor Depos).
ition) method is similar to low-temperature treatment, but heat input due to the evaporation phenomenon is unavoidable, so it is desirable to use a heat-resistant iron-based material as a base material if possible.

The PVD method used in the present invention is a technique for forming a film, and can be basically classified into three methods: vapor deposition, sputtering, and ion plating. As a method of obtaining a mixed vapor of chromium and nickel, chromium and nickel may be separately evaporated, or a chromium-nickel alloy may be evaporated.

In particular, in the present invention, the reactive ion plating method of depositing a chromium nitride + nickel film on a substrate by reacting an evaporating substance of chromium and nickel with nitrogen is most preferable. When plasma is generated in a gas phase in which chromium and nickel vapors are mixed with nitrogen, the chromium ionizes and combines with nitrogen ions to form chromium nitride. As a result, a chromium nitride + nickel film is formed on the substrate surface.

[0014]

When a substrate is coated with a nitride single phase such as titanium nitride, a sudden change occurs from the metal phase to the ceramic phase at the interface between the base material and the coating, and the chemical composition, crystal structure, and coefficient of linear expansion therebetween. , The adhesion of the film is poor, and the ceramic film tends to peel off. On the other hand, the film according to the present invention forms a so-called cermet having a composite phase in which ceramic and metal are mixed. The change in the crystal structure and the coefficient of linear expansion is small, and the adhesion to the substrate is strong. Further, a composite hard material having high adhesiveness can be manufactured by a simple process without undercoating.

Further, since the metal phase is nickel having high corrosion resistance, the corrosion resistance of the chromium nitride film is also improved.
Since ceramic coatings made of PVD are generally under compressive stress immediately after production, cracks are generated in the coating when a tensile force is applied during the use of sliding parts, and it is often seen that corrosion becomes a starting point. Because the material of the present invention is a cermet film,
The coating is tough and hard to crack, and the corrosion caused by the crack is suppressed.

Hereinafter, the present invention will be described in detail with reference to examples. (Embodiment 1) In this embodiment, a substrate made of SKD61 material is used, and a chromium nitride + nickel film is formed on the surface thereof by 5 μm.
m was formed. For the PVD treatment, a cathode arc plasma type ion plating apparatus was used. 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 evacuating the chamber until the pressure in the chamber reaches 1.3 × 10 ⁻³ Pa, the heater is built in the ion plating apparatus to 300 to 500.
C. to release the gas contained in the substrate.
Cooled to ° C. When the pressure in the chamber became 4 × 10 ⁻³ Pa or less, a chromium-nickel target was used as a cathode, an arc discharge was generated on the surface thereof, and chromium ions and nickel ions were ejected. At this time, a bias voltage of -700 to -900 V is applied to the substrate, and metal ions ejected from the cathode collide with the outer peripheral surface of the substrate with high energy. Oxidation removal and activation treatment of the substrate surface were performed by so-called pombard cleaning. Thereafter, while lowering the bias voltage and depositing metal ions on the surface of the substrate, nitrogen gas was introduced into the chamber, and nitrogen was ionized by passing through the plasma.
The bias voltage is set to a pressure of about 0 ^{-1 to} 1.6 Pa,
An ion plating film was formed on the substrate surface by applying 10 to -100 V. After the formation of the predetermined film thickness, the substrate was cooled down to 200 ° C. or lower in the vacuum chamber, 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, in the same manner, 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 a chromium-nickel alloy evaporation source having a changed composition ratio were examined.

The composition and the atomic ratio were analyzed by XPS (X-ray photoelectron spectroscopy). Each spectrum of chromium 2P3, nickel 2P3, and nitrogen 1S electrons was used for analysis. As a result of comparing the energy values of each spectrum and analyzing the composition, it was confirmed that in the film, nitrogen and chromium combined to form chromium nitride, and nickel was in a metallic state.

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 nickel to nitrogen when chromium is 1.

[0021]

[Table 1]

The measured values of microhardness of the coating of the present invention are shown in Table 2. The measurement was performed using a micro Vickers hardness tester, and the load was 1
The test was carried out at 0 g for a holding time of 15 seconds.

[0023]

[Table 2]

The above results present invention coating, wear resistance microhardness is H _M V1200 or is found to be satisfactory. But the hardness the nickel ratio exceeds 1 to chromium is reduced further, H _M V8 is a hardness of the chromium plating film
It is equivalent to 00 to 1000, and superiority of wear resistance cannot be expected. Therefore, the maximum atomic ratio of nickel to chromium is defined as 1.

(Example 2) The seizure resistance of the material of the present invention was evaluated. Using a test piece 5 made of SKD61 material and having three pin-shaped protrusions 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 square end face of 5 mm square is formed. A test piece having a coating according to the present invention having a thickness of 5 μm was prepared, and a seizure resistance test was performed using an ultrahigh pressure wear tester. The coating of the test piece was formed by the method described in Example 1, and chromium: nickel: nitrogen = 1: 0.2
The atomic ratio was 1: 0.26.

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

The apparatus and test conditions of the ultra-high pressure wear tester used in this test are as follows. The test apparatus is schematically illustrated in FIG. 1 and FIG. 2 which is a cross-sectional view taken along the line AA in FIG. 1, and has a diameter of 80 mm × a thickness of 10 mm detachably attached to the stator holder 1. Lubricating oil is injected through the oil inlet 3 from the back side at the center of the disk 2 (counterpart material) that has been polished. 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 5 mm square end face 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: FC25 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 product of the present invention has a contact surface pressure of 327 k.
g / cm ² , but the chrome plating of the comparative product had an anti-seizure surface pressure of 253 kg / cm ² or more, and it had excellent seizure resistance even with respect to the titanium nitride film of 283 kg / cm ² . confirmed.

(Example 3) The material of the present invention was subjected to a corrosion wear test using a Kaken abrasion tester. Substrate material is SKD-
61 materials, 5mm long × 5mm wide × 20m long
m, using a test piece with one end in the longitudinal direction having a curved surface of R6 mm, the curved surface 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: nickel: nitrogen = 1: 0.08: 0.6
It was 7. As a comparative example, a thickness of 100
The same test was performed using a test piece on which a 10-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 drum rotates at a predetermined speed. The lubrication was performed by dropping a fixed amount of a sulfuric acid aqueous solution adjusted to PH = 2 to the contact portion to obtain an acid atmosphere.

The test conditions are as follows. Sliding partner material: FC25 material Friction speed: 0.25 m / sec Friction time: 6 hours Contact load: 4 kg Atmosphere: 1.5 cc / min of sulfuric acid aqueous solution adjusted to PH = 2.0 was dropped on the sliding part.

[0034]

[Table 3]

Compared with the chrome-plated product, which is a comparative product, the product of the present invention has a significantly reduced abrasion amount of about 1/50, and is also reduced by about 30% with respect to the abrasion amount of a sample ion-plated with chromium nitride. are doing. According to Table 3, the film of the present invention is:
It is clear that the corrosion and wear properties are significantly improved as compared with the conventional product.

Example 4 The adhesion of the film of the present invention was measured. The adhesion was measured by a method called a twist test. This method fixes one of the abutments of a ring-shaped test piece with a coating on the outer periphery, twists the other one, measures the torsion angle until peeling of the coating occurs, and checks the adhesion of the coating. It is a method to evaluate.

The test piece had an outer diameter of 86 mm and an inner diameter of 82 m.
It has a ring shape with a thickness of 3 mm and a thickness of 3 mm. The material used was SKD61.

According to the method described in Example 1, a composite film of chromium nitride + nickel composed of chromium: nickel: nitrogen = 1: 0.2: 0.7 at an atomic ratio of 10 μm was formed on the outer peripheral surface of the test piece.
m. As a comparative example, the same test was performed using a test piece in which a single phase of titanium nitride was coated on the outer periphery of a test piece having the same material and dimensions by 5 μm by ion plating.
The results of the adhesion test are shown in Table 4 in terms of the angle ratio with the twist angle of the comparative product as 1.

[0039]

[Table 4]

In general, the greater the thickness of the coating, the lower the adhesion. However, the coating of the present invention has a large torsion angle until peeling occurs even though the coating is thicker than titanium nitride. I have.

[0041]

As is clear from the above invention,
The present invention, by coating a composite film of chromium nitride and nickel on the substrate surface, has superior seizure resistance, abrasion resistance, and adhesion of the film as compared with conventionally used coatings. A composite hard material suitable for moving parts, cutting tools, and the like can be provided, and such a composite hard material is manufactured by a simple process.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a part of an ultra-high pressure abrasion tester.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

[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 projection of test piece (5 mm square)

Claims (1)

(57) [Claims] 1. A PVD which has a composition ratio of chromium: nickel: nitrogen = 1: 0.05-1: 0.1-1 in atomic ratio, and in which chromium nitride and metallic nickel are present. A sliding material comprising a film coated on a substrate.