JP2001193644A - Sliding member for compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sliding member for compressor having excellent anti- abrasiveness, a low attacking property for the mating party, and excllent tight attaching performance. SOLUTION: As an underlayer, a Cr2N coating film is applied to the base material of a sliding surface, and as an overlayer, a coating film of a mixture of CrN and Cr2N is formed. It may be acceptable that the underlayer coating film consists of a mixture of Cr2N and Cr or of metal Cr. It may also be acceptable that the surface of base material is nitrided, and over the nitride layer, an underlayer and overlayer are formed. The coating films should preferably be evaporation films embodied by the ion plating process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sliding member for a compressor, and more particularly to an improvement in coating adhesion of a sliding member for a compressor such as a vane or a roller that slides in the compressor.

[0002]

2. Description of the Related Art Various compressors are used in refrigerators and air conditioners. The compressor includes a rotary compressor, a reciprocating compressor and the like, and each compressor incorporates many sliding members. FIG. 5 is a sectional view showing an example of a rotary compressor.

In the rotary compressor 1, a roller 5, which is rotatably mounted on a portion of an eccentric portion 4 formed on a part of a rotary shaft 2 and mounted in a cylinder 3, is provided with a tip end of a vane 6. The gas in the cylinder is compressed by rotating the inner surface of the cylinder 3 while making contact with the gas. At this time, the vane 6 reciprocates in the cylinder groove 8 formed in the cylinder 3 while constantly abutting on the outer periphery of the roller 5 with the spring 7 to maintain airtightness. Similarly, it is always in contact and keeps airtight. Further, as the roller rotates, the tip of the vane 6 slides on the outer peripheral surface of the roller 5, and when the vane reciprocates in the cylinder groove 8, the side surface of the vane slides on the inner surface of the groove. Members that slide in such a compressor are required to have excellent wear resistance.

In order to meet such a demand for improvement in wear resistance during sliding, a base material of a sliding member is subjected to nitriding. For example, the hardness of high-speed steel (SKH 51), which is widely used as a base material for shindo members, is about Hv750, but when it is subjected to nitriding, the hardness increases to about Hv1250. However, the wear resistance is considerably improved. However, there has been a problem that sufficient durability cannot be exhibited under severe conditions such as a compressor.

To solve such a problem, see, for example,
JP-63692 proposes a sliding member for a compressor such as a vane in which a coating layer is mainly formed on a base material by an ion plating method. As this coating layer, TiN is exemplified. By forming a coating by an ion plating method such as TiN, the wear resistance is remarkably improved. However, the hardness of titanium nitride (TiN) by the ion plating method is as high as about Hv2500, and there is a considerable difference in hardness as compared with the hardness of the base material (for example, about Hv750 for SKH51). When such a hard coating layer is formed on the base material, there is a problem that the impact resistance is reduced, the coating layer is easily peeled off, and the aggressiveness to the partner is increased.

[0006] JP-A-8-226395, one of the sliding members in the compression mechanism, the compound layer of CrN formed by a PVD method, or 40% or less of Cr ₂ N and the balance CrN
There has been proposed a hermetic rotary compressor made of an iron-based material having a mixed compound layer on the surface.

[0007]

SUMMARY OF THE INVENTION
In the technique described in Japanese Patent Application Laid-Open No. 8-226395, since a compound layer mainly composed of CrN is directly coated on a base material (iron-based material) by a PVD method, the hardness difference between the coating layer and the base material is large. However, there still remains a problem that adhesion is low and the coating layer is peeled off.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has a sliding member for a compressor which has little peeling of a coating layer, has low aggressiveness to a partner, and has excellent adhesion of the coating layer. The purpose is to propose.

[0009]

Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have intensively studied factors that affect the adhesion of a coating layer on a sliding member for a compressor. As a result, the change in hardness from the base material to the coating layer (coating) and the change in the coefficient of thermal expansion are gradual, thereby reducing the residual internal stress due to heat treatment and the like, and improving the adhesion of the coating layer (coating). It was found that it improved. The inventor of the present invention has proposed that the coating layer formed on the base material should be a multi-layer composed of two or three layers, and that the surface layer (upper layer) of the coating layer should have a low opponent aggressiveness, and should preferably be made of CrN by ion plating. after having a mixed layer of Cr ₂ N and the coating layer formed on the base material (lower layer), nitride layer having a thermal expansion coefficient close to the base material, or, preferably by ion plating, Cr _It has been found that it is better to use ₂ N, or a mixture of Cr ₂ N and metal Cr, or a layer made of metal Cr, or two to three layers of these layers.

The present invention has been completed based on the above findings. That is, the present invention relates to a sliding member for a compressor which performs a sliding motion in a compressor, wherein at least one sliding surface of the sliding member for the compressor has Cr ₂ N on a base material.
A film consisting of CrN
And a sliding member for a compressor excellent in coating adhesion and abrasion resistance, which comprises forming a film consisting of a mixture of Cr ₂ N, also in the present invention, the lower layer and Cr ₂ N It is preferable to use a film composed of a mixture with Cr or a film composed of metallic Cr. In the present invention, the surface of the base material is nitrided to form a nitrided layer, and a film made of Cr ₂ N, a film made of a mixture of Cr ₂ N and Cr, or a metal Cr is formed on the nitrided layer. Layer consisting of: CrN and Cr ₂ N
It is preferable to form an upper layer made of a film made of a mixture of the above. In the present invention, each of the coatings is preferably a vapor-deposited film formed by an ion plating method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A sliding member for a compressor according to the present invention has at least one sliding surface, on a base material of the member, a coating layer composed of at least two layers of an upper layer and a lower layer. . FIG. 1 is a cross-sectional view showing the vicinity of the surface of a compressor sliding member. FIG. 1A schematically shows a state in which a base material is coated with a coating 11 as an upper layer and a coating 10 as a lower layer.

The method of forming the coating layer in the present invention is not particularly limited, but may be any of PVD and CVD. PVD includes methods such as vacuum deposition, sputtering, and ion plating. Above all, a deposited film formed by an ion plating method is preferable because of its high adhesion strength.
In the present invention, the upper layer 11 contains 45 to 98% by mass of CrN and the balance of Cr ₂ N.
And a film composed of a mixture of Both CrN and Cr ₂ N have excellent abrasion resistance.However, when CrN and Cr ₂ N are used alone, their workability during polishing and grinding is poor, resulting in chipping and peeling. Many occur. Further, even during use, it is vulnerable to dynamic shock and thermal shock, and easily causes accidents such as peeling and breakage. For this reason, the coating as the upper layer was a mixture of CrN and Cr ₂ N. By mixing CrN and Cr ₂ N, chromium nitrides having different crystal systems are complicatedly entangled, dense and smooth, and have excellent impact resistance and toughness. Then, a dense and smooth film is formed, the aggressiveness of the partner is reduced, and the wear amount of the partner is reduced. The amount of CrN contained in the coating as the upper layer is 45% (% by mass) or more, preferably
55% or more and 98% or less, preferably 88% or less. CrN
When the content is less than 45%, the wear resistance is significantly reduced.
On the other hand, even when the content exceeds 98%, no remarkable improvement in wear resistance is observed, and instead, workability, impact resistance and toughness are reduced. The thickness of the film as the upper layer is 0.5 μm or more, preferably 4 μm or more and 10 μm or less. 0.5 μm coating thickness
If it is less than m, the desired wear resistance improving effect cannot be obtained because the film thickness is too thin. On the other hand, if it exceeds 10 μm, the film strength itself decreases, and the peeling resistance decreases.

Further, in the present invention, a coating having a lower hardness than the upper coating and having a thermal expansion coefficient closer to that of the base material than the upper coating is formed as the lower layer 10 on the base material. As such a coating, there is a coating made of Cr ₂ N. Incidentally, the hardness of the Cr ₂ N coating is about Hv1300 and the thermal expansion coefficient is 9.4 × 10 ⁻⁶ / deg. On the other hand, the hardness of the CrN + Cr ₂ N is approximately Hv 1800,
The hardness of the base material is about Hv750 of high speed steel (SKH51), and the thermal expansion coefficient is 11.7 × 10 ⁻⁶ / deg. By forming such a film as a lower layer on the base material, the internal stress of the film generated at the time of forming the film or at the time of heat treatment is reduced, and the adhesion of the film is improved.

[0014] In the present invention, instead of the Cr ₂ N, a mixture of Cr ₂ N and the metal Cr, or may be a metal Cr. By containing metal Cr in the film as the lower layer, the film hardness is reduced, the difference from the base material hardness is small, and the film adhesion is further improved. The thickness of the film as the lower layer is 0.2
μm or more, preferably 0.5 μm or more and 2 μm or less.
If the thickness of the coating is less than 0.2 μm, the adhesion and abrasion resistance of the coating decrease, and if it exceeds 2 μm, the abrasion resistance and the peeling resistance decrease.

In the present invention, a coating as a lower layer may be formed directly on the base material. However, as shown in FIG. 1B, the surface of the base material is nitrided to form a nitrided layer. A film as the lower layer 10 is formed on the nitride layer, and the lower layer 10 is further formed.
An upper layer 11 may be coated thereon. By forming the lower and upper coatings on the base material via the nitride layer, the change in hardness from the base material to the upper coating becomes smoother, the coating adhesion is improved, and the impact resistance is increased. In the present invention,
Instead of high-speed steel (SKH 51), stainless steel (SUS440C) and bearing steel (SUJ2) can be used as a base material.

As the method for forming the nitride layer, any of the well-known methods such as ion nitriding and gas nitriding is suitable. Usually, the surface hardness of the nitrided layer is Hv1200 or more. In addition,
In the present invention, the thickness of the nitride layer is 1 μm
As described above, the thickness of the diffusion layer is preferably 30 μm or more. In the present invention, the coating layer does not need to cover the entire surface of the sliding member. The coating may be limited to only the sliding surface. For example, in the case of the compressor vane shown in FIG. 3, a coating layer composed of an upper layer 11 and a lower layer 10 is formed on the tip and side surfaces, which are sliding surfaces, and no coating layer is formed on the base. . In the vane shown in FIG. 4, the upper layer 11 is formed only at the tip end where the wear resistance is most required, and the lower layer 10 alone is formed on the side surface. In the case of the vane shown in FIG. 2, this is an example in which a coating layer is formed only on the tip portion exposed to particularly severe sliding conditions.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a base material of a sliding member (vane) for a compressor,
Donut-shaped test piece (outer diameter 40 mmφ, inner diameter 16 mmφ, thickness 10 mm) using high-speed steel (SKH 51) equivalent to a vane
Were prepared, and various coating layers shown in Table 1 were formed on the surface of the test piece, and subjected to a scuffing resistance test. The test was carried out using an Amsler test machine under the following conditions. In addition, as a partner piece (plate shape: 18 mm × 15 mm × thickness 5 mm),
Roller material (monicro cast iron) was used. Finally, scuffing was caused, and the load when scuffing occurred was measured as a critical surface pressure. The results are shown in Table 1.

The scuffing resistance is expressed as a scuffing surface pressure index with the critical surface pressure of the conventional example being 100. In the case of anti-scuffing surface pressure index less than 100,
Scuffing resistance is inferior to the conventional example. Test conditions • Rotational speed: 5 m / sec • Lubricating oil: SAE30 + white kerosene (1: 1) • Oil temperature: 50 ° C • Oil volume: 0.2 l / min • Load: 25 kgf / cm ² (2.45 MPa) for 20 minutes After, 30kgf /
cm ² and ^{(2.94MPa), 5kgf / cm 2} (0.49 to hereafter every 2 minutes
MPa) The coating layer was formed on the surface of the test piece by a reactive ion plating method, using the various coatings shown in Table 1 as a lower layer and an upper layer. Note that N gas was used as a reaction gas. In the case of using metal chromium alone, vacuum was applied without introducing N gas. Adopt Cr as the evaporation source and heat it to Cr
Is evaporated in the reaction gas, it is ionized in the gas phase state, the biased preform (specimen) surface negatively, a reaction product CrN, Cr ₂ N, Cr, and ion plating, coating A layer was formed. The proportion of each chromium nitride in the coating was adjusted by changing the partial pressure of N gas, which is a reaction gas in the atmosphere.

Some of the test pieces were subjected to an ion-pure nitriding treatment on the surface of the base material to form a nitrided layer, and then the above-mentioned coating layer was formed. The ion pure nitriding treatment was performed at a temperature of 520 ° C. in a mixed gas atmosphere of nitrogen gas and hydrogen gas. The above test pieces were further subjected to an adhesion test. The adhesion test uses a scratch tester to determine the critical load at which film peeling occurs.
It is shown as a peeling load index as 0, and is shown in Table 1. When the peeling load index is less than 100, it indicates that the adhesion of the coating film is lower than in the conventional example.

[0020]

[Table 1]

From Table 1, it can be seen that the example of the present invention is a sliding member in which the hardness gradient of the coating is gentle, the aggressiveness of the coating is low, and the adhesion of the coating is remarkably improved as compared with the conventional example. Understand. In Comparative Examples outside the range of the present invention, the adhesion of the coating film was deteriorated.

[0022]

According to the present invention, a compressor having excellent abrasion resistance equal to or higher than conventional ones, low aggressiveness of a mating member, and further excellent in workability in manufacturing and durability in operation. The sliding member for use can be manufactured inexpensively and with a high yield, and the industrially remarkable effect is achieved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of a coating layer structure near the surface of a sliding member for a compressor of the present invention.

FIG. 2 is a longitudinal sectional view of a compressor vane according to one embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a compressor vane according to one embodiment of the present invention.

FIG. 4 is a longitudinal sectional view of a compressor vane according to one embodiment of the present invention.

FIG. 5 is a sectional view showing an example of a rotary compressor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor 2 Rotating shaft 3 Cylinder 4 Eccentric part 5 Roller 6 Vane 7 Spring 8 Cylinder groove 10 Lower layer 11 Upper layer

Claims (4)

[Claims] 1. A sliding member for a compressor which performs a sliding motion in a compressor, wherein a coating made of Cr ₂ N is formed on a base material on at least one sliding surface of the sliding member for the compressor. It formed as a lower layer, CrN and Cr ₂ N and the film adhesion and excellent wear resistance sliding member for a compressor, which comprises forming a film comprising a mixture as the upper layer. The method according to claim 2, wherein said lower layer, in place of the coating film made of Cr ₂ N, the sliding member for a compressor according to claim 1, characterized in that a coating consisting of a mixture of Cr ₂ N and Cr. 3. The sliding member for a compressor according to claim 1, wherein the lower layer is a coating made of metal Cr. 4. The method according to claim 1, wherein the surface of the base material is nitrided to form a nitrided layer, and a lower layer and an upper layer made of the film are formed on the nitrided layer. Sliding members for compressors.