JPH06346077A - Sliding part - Google Patents

Abstract

PURPOSE:To prepare a hard coating film composed mainly of Cr, having excellent sliding characteristics such as abrasion resistance and seizure resistance and exhibiting excellent initial conformability. CONSTITUTION:The sliding part is produced by coating a substrate with a coating film composed of Cr, an M group (M is Ti, V, Zr, Nb, Mo, Hf, Ta, W and/or Al), N and O and having a compositional ratio of the metallic elements M/(Cr+M) of 1-55 atom % and that of gaseous elements O/(N+O) of 5-80 atom %.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member having a hard coating on the sliding portion and used for machine parts such as automobile parts and compressor parts. More specifically, chromium is the main metal component. The present invention relates to a sliding member coated with a film composed of one or more metal elements and nitrogen and oxygen.

[0002]

2. Description of the Related Art Sliding parts such as mechanical parts are subject to sliding characteristics such as wear resistance and seizure resistance under increasingly severe conditions due to higher rotation speed and higher output of internal combustion engines and compressors of automobiles. It is expected to improve. Similarly, in cutting tools, it is expected that the sliding characteristics will be improved by increasing the cutting speed. Conventionally, as a measure for improving sliding characteristics, surface treatment such as improvement of wear resistance by hard chrome plating and improvement of seizure resistance by nitriding or molybdenum spraying can be mentioned.

However, these methods do not provide sufficient sliding properties as a sliding material, and have recently been relatively chemically chemically prepared by physical vapor deposition (PVD) or chemical vapor deposition (CVD). Methods for producing stable Cr-N-based and Ti-N-based hard coatings have been investigated. However, Cr-
Since the N-based coating has a relatively low coating hardness, the coating is apt to wear, and although attempts have been made to improve this point, sufficient sliding characteristics have not yet been obtained.

Therefore, it is desired to develop a film having higher film hardness and excellent sliding characteristics, and a Ti-N-based film has attracted attention. However, the Ti-N-based coating has a drawback that the hardness of the coating is too high when it is used as a sliding member such as a machine part, and it causes abrasion of the mating material. "Familiarity" also has the disadvantage. Here, "initial familiarity" means that the surface of the sliding member, which has roughness caused by machining or film formation itself, comes into sliding contact with the mating material within a short time after the start of sliding, and the surface is minute and smooth. As a result of abrasion, the contact surface pressure is reduced by increasing the contact area, making it difficult for lubricant oil film breakage to occur, thereby preventing wear and seizure. A sliding member coated with a film having a too high film hardness such as a Ti-N-based film has a problem that it is likely to cause abrasion or seizure at the initial sliding stage due to poor initial fitting.

[0005]

In view of the above points, the present invention provides a sliding material coated with a film containing Cr as a main metal component, which has excellent sliding characteristics such as wear resistance and seizure resistance. The object of the present invention is to solve the above problems by coating a hard film having good initial familiarity. further,
In order to solve the above problems, the present applicant has filed Japanese Patent Application No. 5-1
No. 20062, a metal element consisting of chromium, an M group (M; one or more metal elements selected from titanium, vanadium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten and aluminum) and nitrogen, The composition ratio of M / (Cr +
Although a sliding member coated with a film of M) = 1 to 55% was proposed, the present invention aims to further improve the above-mentioned wear resistance and reduce the wear of the mating member.

[0006]

[Means for Solving the Problems] That is, the sliding member according to the present invention comprises chromium, group M (M; titanium, vanadium, zirconium, niobium, molybdenum, hafnium,
One or more metal elements selected from tantalum, tungsten and aluminum), nitrogen and oxygen, and the composition ratio of the metal elements is M / (Cr + M) in atomic% ratio.
= 1 to 55%, and the composition ratio of the gas elements is O / (N + O) = 5 to 80% in atomic% ratio. This film is CrN or C
By adding an element of group M and oxygen to r2 N, the hardness of the coating itself is higher than that of CrN or Cr2 N coating, and the wear resistance, seizure resistance and initial familiarity of CrN are improved.
Alternatively, it is better than the Cr2 NG coating.
The effects of the elements of group M and oxygen are as follows: (a) Both increase the hardness of the CrN or Cr2N film, but the former has a higher rate of increase in hardness, and (b) the former is CrN or Cr2. Although the coefficient of friction of the N film is slightly increased, the latter greatly reduces it, and (c) both suppress the reduction of CrN or Cr2 N film due to corrosion in oil, but the former is less effective. Is large.
Since the elements of group M and oxygen are different due to the influence on the physical properties, they are divided into different groups, and Ti, V, Z
Since r, Nb, Mo, Hf, Ta, W, and Al are all common in the above points, they are included in one group.

If the metal element composition ratio of M / (Cr + M) is less than 1%, the effect of improving wear resistance is small, whereas if it exceeds 55%, seizure resistance and initial familiarity cannot be improved. The metal element composition ratio was in the range of 1 to 55%. If the composition ratio O / (N + O) of the gas element is less than 5%, the wear of the mating material increases, whereas if it exceeds 80%, the wear of the coating itself increases and the sliding characteristics cannot be improved.

As the base material, various materials such as Fe-based material, Al-based material and Ti-based material can be used. The thickness of the Cr-M-N-O-based coating is not particularly limited, but is preferably in the range of 1 to 50 μm. Similarly, the film roughness Ra is 1 μm
The following is preferable.

Further, the mating material is not particularly limited, and cast iron or steel material, these materials plated with Cr, materials having a thermal spray coating, etc. can be used. Further, the coating film of the present invention is formed by PVD or CVD, preferably PVD, on a sufficiently cleaned substrate.

[0010]

[Function] The CrN-based coating has low wear resistance, while the TiN-based coating has poor initial conformability, and thus both are prone to seizure. However, Cr containing Cr and other metal elements M, N and O coexist. By using a -M-N-O type coating, it became difficult for seizure to occur. In addition, since the wear resistance is improved, the wear after the fitting is realized is reduced and the wear of the mating material is also reduced. Hereinafter, the present invention will be described in detail with reference to examples in which V is selected as the metal element (M).

[0011]

EXAMPLE The film-forming substrate used in this example is high chromium steel (JIS standard SUJ-2). The substrate was ultrasonically cleaned in a Freon solution in advance, and the mirror-finished substrate surface was subjected to cathodic arc plasma ion plating according to the procedure described below to perform Cr-N hard coating (comparative example), Cr-VN. System hard coating (comparative example) and Cr-V
A -NO hard coating (Example) was formed.

The ultrasonically cleaned substrate was mounted in a vacuum container (chamber) of an ion plating apparatus, and then vacuumed until the chamber pressure reached 1.3 × 10 −3 Pa (pascal). From the time when this degree of vacuum is achieved, the substrate is heated to 300 to 600 ° C. by the heater built in the chamber to release the gas components adhering to or adsorbing on the substrate surface, and then 200 ° C.
Cooled down.

When the pressure in the chamber becomes 4 × 10 -3 Pa or less, arc discharge is generated on the surface of the Cr-V alloy target having various compositions used as the cathode, and most of Cr and V are ionized. It was ejected from the target surface.

At this time, the jig on which the base body is mounted is -700 to
A bias voltage of -1000 V was applied, the ionized Cr and V jumping from the target were attracted to the surfaces of the substrate and the jig, and these ions were made to collide with the surface to be processed at high speed. The activation treatment of the substrate surface was performed by so-called sputter cleaning in which oxides and the like on the surface to be treated were scraped by the collision of the ionized metal.

After that, a small amount of nitrogen gas was introduced into the chamber where the arc discharge occurred, and a part of ionized Cr and V were combined with the nitrogen gas and deposited as a nitride film on the surface of the substrate. Thereafter, the flow rate of nitrogen gas is further increased to introduce oxygen gas at a flow rate that provides a predetermined gas element gas element composition ratio to a pressure of about 0.7 to 4.0 Pa, and a bias voltage of 0 to -100 V is applied to the substrate. Apply 1-50 Cr-VNO hard coating on the substrate surface by applying
It was formed to a thickness of μm. In addition, Cr-VN of the comparative example
In the case of forming a system film, the film was similarly formed without introducing oxygen gas. After forming the specified film thickness, the chamber temperature is 150 ℃
After cooling to the following, the film-coated substrate was taken out of the chamber. The hardness of the film is Hv = 1000-2
It was in the range of 500.

A sliding test was carried out using the film obtained by the above method. Example 2 A scuff test was carried out by a pin-on-disc type friction tester using gray cast iron (FC25) as a counterpart material. The scuff test conditions were as follows. Lubrication method: Motor oil # 30, oil temperature 80 ° C, oil amount 4
cc / sec Friction speed: 8 m / sec Contact load: Initially increased from 2 MPa to seizure every 1 MPa. Friction time: Hold for 180 seconds under each load Table 1 shows the results of the scuff test.

[0017]

[Table 1] No V (Cr + V) -1 O (N + O) -1 Scuff value 1 Cr-V -N -O 15 20 2.1 shot 2 Cr-V -N -O 50 20 2.3 Clear 3 Cr-V -N-O50 70 2.4 Ratio 1 Cr-V -N 50 0 2.0 Comparison 2 Cr-N 0 0 1.0 The scuff value is the value when the comparison target Cr-N is 1.0.

No. 1 according to the present invention. 1, 2 and 3 Cr
The -V-N-O-based film has a V atom% (hereinafter simply referred to as "V atom%") of 1 with respect to the metal element in the film.
5, 50 and 50%, and the oxygen atom% (hereinafter simply referred to as "oxygen atom%") with respect to the sum of nitrogen atoms and oxygen atoms in the film is 20, 20 and 70%, respectively. The ratio (ratio) of metal atoms and gas atoms is approximately (2 to
1): It is desirable to set it to 1: but it is not limited to this.

The effect of V atomic% and oxygen atomic% in the coating on the characteristics of the coating was investigated. C that does not include V as a comparative example
A scuff value (baking surface pressure) of 1.0 was obtained by performing a scuff test on the r-N type coating under the same conditions. The scuff value of the Cr-V-N-O-based coatings of 1, 2 and 3 was improved by about two times or more. Furthermore, No. 2 and N
o. Comparing the Cr-V-N-O-based coatings of No. 3 with No. 3 having a large oxygen atom%. 3 showed a high scuff value.

Example 3 A pin-drum abrasion tester was used to perform an abrasion test using gray cast iron (FC25) for the drum. The wear test conditions were as follows. Lubrication method: Motor oil # 30, oil temperature 80 ° C, oil amount 8
cc / sec Drum rotation speed: 5 m / sec Contact load: 1.5 MPa Test time: 30 ksec Table 2 shows the wear test results.

[0021]

[Table 2] Pin drum No V (Cr + V) -1 O (N + O) -1 Abrasion amount Abrasion amount 1 Cr-V-N-O 15 20 0.5 0.7 Shot 2 Cr-V-N-O 50 20 0.4 0.6 Bright 3 Cr-V -N -O 50 70 0.4 0.6 Ratio 1 Cr-V -N 50 0 0.6 0.8 Comparison 2 Cr-N 0 0 1.0 1.0 The scuff value is 1.0 for Cr-N which is the comparison target. It is the value at the time of doing.

As a comparison object, V and C containing no oxygen
A wear test was performed on the r-N-based coating and the Cr-VN coating containing no oxygen under the same conditions as the Cr-VN-O coating. Here, the amount of wear of the pin coated with the film was obtained from the width of the worn contact surface in the drum rotation direction, and the amount of wear of the drum was obtained from the wear depth of the drum. Table 2 shows the respective characteristics when the amount of pin wear and the amount of drum wear in the case of the Cr-N type coating are 1.0.

The Cr-VN-0 type coating according to the present invention comprises
The amount of wear of the drum is slightly reduced as compared with the comparative example, while the amount of wear of the pin is significantly reduced as compared with the comparative example. In particular, No. 2, No. In the Cr-V-N-O-based coating of No. 3, the wear amount is suppressed to about 1/2 of the Cr-N-based coating and 2/3 of the Cr-VN-based coating.

From the results of the above scuffing test and abrasion test, it is possible to compare the Cr-N type coating and the Cr-VN coating with Cr.
It has been found that the -V-N-O type coating has excellent seizure resistance, good initial familiarity, and can suppress wear of the mating material of the sliding portion.

[0025]

As described above, the conventional Cr-N system or Cr-V system is formed by coating the sliding surface with a film composed of Cr, which is the main metal component, other metal elements, nitrogen and oxygen.
It is possible to obtain a sliding member that does not wear the mating material more than the case where the -N film is coated, has good initial conformability, and has excellent sliding characteristics such as wear resistance and seizure resistance.

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Claims (1)

[Claims] 1. Chromium, group M (M; titanium, vanadium, zirconium, niobium, molybdenum, hafnium,
One or more metal elements selected from tantalum, tungsten and aluminum), nitrogen and oxygen, and the composition ratio of the metal elements is M / (Cr + M) in atomic% ratio.
= 1 to 55%, and the composition ratio of the gas element is atomic% ratio O / (N + O) = 5 to 80%.