JP2008241014A - Slide member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a slide member further enhancing the mechanical characteristic of a CrN covering film. <P>SOLUTION: In the slide member, a covering film containing chromium nitride as a main component is formed on a slide surface by an ion plating method. The covering film makes ä200} plane of CrN as a main orientation, contains 0.05 to 20 mass% of boron, and is constituted such that a vacancy ratio is 0.5 to 20% to solve the above problem. Further, the covering film is preferably constituted such that a content of any one of oxygen and carbon or a content of both is 15 mass% or less, and is preferably used as a piston ring for an internal combustion engine. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sliding member, and more particularly to a sliding member used as a piston ring for an internal combustion engine in which a chromium nitride film that is strong against a force applied in parallel to the sliding surface is formed on the sliding surface.

In a sliding member such as a piston ring for an internal combustion engine, a CrN film containing Cr ₂ N is formed on the outer peripheral sliding surface by an ion plating method to improve wear resistance. Proposed. Further, forming a CrN film having a {111} plane as a main orientation by an ion plating method, and adding 0.05 to 20% by mass of B to the CrN film to improve the peel resistance is as follows. Patent Document 2 proposes this. There are two types of coatings made of Cr-B-N, one with CrN having {111} plane as the main orientation and one with {100} plane as the main orientation, with {111} plane as the main orientation. Compared with those having the {100} plane as the main orientation, the ones are superior in wear resistance and scuff resistance, but have a problem that the internal stress is high and the peel resistance is inferior. On the other hand, those having the {100} plane as the main orientation are inferior in wear resistance and scuff resistance compared to those having the {111} plane as the main orientation, but the porosity is easily controlled. Excellent peel resistance.
JP-A-8-296030 JP 2000-136875 A

  However, since the crystal structure of the ion plating film in which CrN described in Patent Document 2 has a {111} plane as a main orientation is a columnar crystal, surface irregularities (surface roughness) after the film is formed. Tends to be large, and is somewhat inferior in terms of resistance to opponent attacks. An ion plating film in which CrN has a {111} plane as a main orientation is strong against a force from the normal direction of the film surface, but against a force applied in parallel to the film surface which is a sliding surface. There is a drawback that it is weak. That it is weak to such force is considered that the peeling resistance evaluated by, for example, a scratch test is not sufficient, and the wear resistance is not sufficient.

  The present invention has been made to solve the above-mentioned problems, and the object thereof is a sliding member that further improves the mechanical properties of a film mainly composed of chromium nitride formed by an ion plating method. Is to provide.

  The sliding member of the present invention for solving the above-mentioned problem is a sliding member in which a film mainly composed of chromium nitride is formed on a sliding surface by an ion plating method, and the film is made of CrN { 200} plane is the main orientation, boron is contained in an amount of 0.05% by mass or more and 20% by mass or less, and the porosity is 0.5% or more and 20% or less.

  According to the present invention, as a result of the formation of the coating on the sliding surface with the {200} plane of CrN as the main orientation and containing a predetermined amount of boron, it is excellent in wear resistance and scuffing resistance. On the other hand, it was possible to form a film that was strong against the force applied in parallel and excellent in peel resistance on the sliding surface. The reason why this film is excellent in peel resistance is considered to be that the formation free energy of boron in chromium is higher than that of carbon, oxygen, and nitrogen. It dissolves in CrxN (chromium nitride). Therefore, compared with carbon, oxygen, and nitrogen, the effect on the base strengthening is increased, and it is considered that the peeling resistance of the film is improved. Furthermore, this film has a {200} plane of CrN as the main orientation, but a film having such an orientation can be obtained as a denser film than a film having the {111} plane of CrN as the main orientation. In particular, the film can be made strong against a force applied in parallel to the sliding surface and excellent in peel resistance. Furthermore, according to the present invention, excellent peel resistance, wear resistance and scuff resistance are exhibited within such a porosity range.

  In the sliding member of the present invention, it is preferable that the coating is configured such that the content of either one or both of oxygen and carbon is 15% by mass or less. According to the present invention, excellent peel resistance, abrasion resistance and scuff resistance are exhibited within such a content range.

  In the sliding member of the present invention, it is preferable that the sliding member is a piston ring for an internal combustion engine. According to the present invention, by forming a film by an ion plating method on the outer peripheral sliding surface of the piston ring, it can be preferably applied as a piston ring exhibiting excellent peeling resistance, wear resistance and scuff resistance.

  According to the sliding member of the present invention, the film whose main orientation is the {200} plane of CrN contains a predetermined amount of boron, so that it is empty compared to the conventional film whose main orientation is the {111} plane of CrN. It can be obtained as a dense film with a small porosity, and as a result, it can be a film exhibiting excellent peeling resistance, abrasion resistance and scuff resistance, and in particular, horizontal and parallel to the sliding surface. The film can be strong against the force applied to the film. In addition, the sliding member of the present invention can be applied as a piston ring that can be used for a high-power, high-temperature, high-load engine that is expected to be developed in the future.

  The piston ring of the present invention will be described below with reference to the drawings. The following embodiment is an example of the present invention, and the technical scope of the present invention is not limited to the following embodiment. In the present application, “film” refers to a film formed by an ion plating method unless otherwise specified.

(Sliding member)
In the sliding member of the present invention, a film mainly composed of chromium nitride is formed on the sliding surface by an ion plating method, and the film has a {200} plane of CrN as a main orientation, It contains 0.05% by mass or more and 20% by mass or less of boron. In this film, the content of either one or both of oxygen and carbon may be 15% by mass or less.

  The film is a compound film formed by an ion plating method. In the present invention, the film is a film mainly composed of chromium nitride. Here, as components other than the main component chromium nitride, chromium, boron, oxygen, carbon, inevitable impurities, and the like can be given. The main component, chromium nitride, is contained in the film at a mass ratio of approximately 80% or more.

  The coating is configured so that the porosity is 0.5% or more and 20% or less. A film having a porosity in this range has a lower porosity than a film having the {111} plane of CrN as the main orientation, and can be obtained as a dense film, so that it has excellent peeling resistance and wear resistance. In addition, it has scuff resistance, is particularly strong against the force applied in parallel to the sliding surface, and has excellent peeling resistance. If the porosity of the film is less than 0.5%, the film becomes too dense and brittle, and chipping and peeling are likely to occur. On the other hand, when the porosity of the film exceeds 20%, it becomes a film that is difficult to say dense, particularly weak against the force applied in parallel to the sliding surface, and cannot be said to have excellent peel resistance. Sometimes. When the porosity is in the range of 0.5% or more and 20% or less, 0.5% or more and 15% or less is preferable from the viewpoint of film strength, and 0.5% or more and 10% or less is preferable from the viewpoint of wear resistance. preferable. In addition, in this application, the porosity of a membrane | film | coat measures the porosity by image-analyzing the black-and-white which appears on a membrane | film | coat surface or a membrane | film | coat cross section.

The chromium nitride constituting the film contains Cr ₂ N, but is mainly made of CrN, and the CrN has a {200} plane as the main orientation. Here, the “main orientation” refers to the surface showing the largest relative value when compared with the relative value of the diffraction intensity with respect to ICDD as compared with ICDD (International Center for Diffraction Data) for CrN. . Therefore, a film having the {200} plane of CrN as the main orientation shows a relative value of diffraction intensity with respect to ICDD having the largest value on the {200} plane of CrN. In the present application, the crystal orientation can be analyzed by an X-ray diffraction method.

  In the present invention, a film whose main orientation is the {200} plane of CrN is provided on the sliding surface. Such a film can be obtained as a dense film having a lower porosity than a film whose main orientation is the {111} plane of CrN. As a result, the coating according to the present invention has an advantage that it is strong against a force applied in parallel to the sliding surface and has excellent peeling resistance.

  Boron is contained in the film in an amount of 0.05% by mass or more and 20% by mass or less. When the boron content is less than 0.05% by mass, the peel resistance of the film is not improved, and when the boron content exceeds 20% by mass, the peel resistance of the film may be considerably reduced. The reason for limiting the boron content within the above range is that the free energy of formation of boron in chromium is high, boron is difficult to form boride, and is dissolved in chromium or CrxN (chromium nitride). Compared to carbon, oxygen, nitrogen, etc., the effect on base strengthening is increased, and as a result, it is considered that the peel resistance of the film is improved. Accordingly, boron is present in a solid solution state in Cr or CrxN (chromium nitride). In the present application, the component composition of boron, oxygen, carbon and the like contained in the film can be quantified using a backscattering measuring device, and the surface form is a metal microscope or X-ray microanalyzer (EPMA). Can be observed.

  The coating is preferably configured such that the content of either one or both of oxygen and carbon is 15% by mass or less. By setting the content of either one or both of oxygen and carbon within this range, it is possible to obtain a film exhibiting excellent peeling resistance, abrasion resistance and scuff resistance. When the content of either one or both of oxygen and carbon exceeds 15% by mass, the peel resistance of the film is lowered.

  The thickness of the film is not particularly limited, and is usually 1 μm or more and 70 μm or less. The thickness varies depending on the use of the sliding member of the present invention, but is preferably 3 μm or more and 50 μm or less, for example, when applied as a piston ring for an internal combustion engine.

  The sliding member of the present invention described above is preferably used as a piston ring. By forming the coating according to the present invention on the outer peripheral sliding surface of the piston ring, it can be preferably applied as a piston ring having excellent peeling resistance, wear resistance and scuff resistance.

  The structure of the piston ring when applied as a piston ring for an internal combustion engine is not particularly limited. For example, various forms can be adopted for the material of the piston ring base material, the nitride layer formed as the base, the kind of the base film, etc., and the coating according to the present invention is formed at least on the outer peripheral sliding surface thereof. It only has to be. Moreover, it is applicable to any of a top ring, a second ring, and an oil ring.

(Sliding member manufacturing method)
A typical manufacturing example of the sliding member of the present invention uses a chromium boron alloy as a target for the ion plating method, and a chromium nitride film containing boron on the outer peripheral sliding surface of the sliding member in a nitrogen atmosphere. In addition, as another forming method, a chromium target is used as a target, and it can also be manufactured in a diborane (B ₂ H ₆ ) gas and nitrogen gas atmosphere. The sliding member of the present invention is not necessarily limited to this manufacturing method as long as it has the above-described constituent elements, and may be manufactured by another manufacturing method.

  The boron content of a film formed by ion plating is usually controlled by easily adjusting the boron content in the film by ion plating using a target with a varied boron content. can do. Specifically, it can be performed by adjusting the boron content in the chromium boron alloy. Further, the film forming conditions can be changed to further adjust.

  The crystal orientation of the film can be controlled by changing the film formation conditions. In the examples described later, the arc current is controlled to produce the {200} plane orientation of CrN and the {111} plane orientation of CrN. It is divided.

  The gas atmosphere in ion plating can include a mixed gas atmosphere of nitrogen and oxygen, a mixed gas atmosphere of nitrogen and hydrocarbons, or a mixed gas atmosphere of nitrogen, oxygen and hydrocarbons. By performing ion plating, the film formed by the ion plating method can contain one or both of oxygen and carbon. The content of oxygen and carbon can be adjusted by adjusting each gas pressure introduced into the chamber.

  Below, the sliding member of an Example, a comparative example, and a prior art example is demonstrated by various tests.

  Ten types of coatings are formed on the same piston ring base material using the arc ion plating apparatus as samples according to the example, and eight types of coatings are formed as samples according to the comparative example. As a result, six types of films were formed. For the piston ring base material, 17Cr stainless steel (C: 0.9 mass%, Si: 0.4 mass%, Mn: 0.30 mass%, Cr: 17.5 mass%, Mo: 1.10 mass%) V: 0.10% by mass, P: 0.02% by mass, S: 0.02% by mass, balance: iron and inevitable impurities). At this time, a bias voltage of −25 V was applied to each sample, and the film formation time was adjusted so as to have a thickness of 20 μm.

  The orientation of CrN in the film was adjusted so that the arc current was 200 A for the examples and comparative examples, and the {200} plane was the main orientation, and for the conventional example, the arc current was 150 A, and {111 } The surface was adjusted so as to have the main orientation. The component composition in the film was controlled by the composition of the target chromium boron alloy for the boron content, and the oxygen and carbon contents were adjusted by the ratio of nitrogen, oxygen, and methane in the atmospheric gas.

  Table 1 shows the orientation plane, composition, porosity, and characteristics of each sample. Moreover, the test method of each characteristic is shown below.

(Abrasion test)
For the wear test, an Amsler type wear tester 20 shown in FIG. 1 is used, a measurement sample 21 (7 mm × 8 mm × 5 mm) is used as a fixed piece, and the mating material 22 (rotating piece) has a donut shape (outer diameter 40 mm, inner diameter). 16 mm, thickness 10 mm), the measurement sample 21 on which the film was formed and the mating member 22 were brought into contact with each other and a load P was applied. Each sample was used as the measurement sample 21. The friction coefficient test conditions using each measurement sample 21 were: counterpart material 22: boron cast iron (C: 3.35 mass%, Si: 2.08 mass%, Mn: 0.82 mass%, P: 0.36 mass) %, S: 0.07 mass%, B: 0.08 mass%, balance: iron and inevitable impurities), lubricating oil 23: Krysef H8 (equivalent to No. 1 spindle oil), oil temperature: 80 ° C., peripheral speed: The test was performed under the conditions of 1 m / sec (478 rpm), load: 1471.5 N (150 Kg), and test time: 7 hours. The counterpart material 22 is ground into a predetermined shape, and then the surface grinding is sequentially performed by changing the fineness of the grinding wheel, so that it finally becomes 2 μm Rz (10-point average roughness, conforming to JIS B0601 (1994)). Adjusted.

  The wear resistance index shown in Table 1 shows the result of the wear amount of each measurement sample as an index. The wear amount of the measurement sample of Conventional Example 2 is set to 100, and the wear amount of each sample with respect to it is set as a relative ratio. Compared. Therefore, the smaller the abrasion resistance index of each measurement sample is, the smaller the wear amount is, and the better the abrasion resistance is. Each of the measurement samples of Examples 1 to 10 and Comparative Examples 1 to 8 having the {200} plane of CrN as the main orientation has a small wear resistance index, and Conventional Examples 1 to 6 having the {111} plane of CrN as the main orientation. It was superior in wear resistance than the measurement sample.

(Peel test: vertical direction)
The peel test is a peel test for a force applied perpendicularly to the outer peripheral sliding surface of the piston ring on which a film is formed by an ion plating method, and was performed using an impact test apparatus 31 shown in FIG. As shown by an arrow in FIG. 2, an indenter 34 urged by a spring 33 is caused to collide with a coating film surface 32 of a sample placed on the gold 35. An impact energy of 43.1 mJ (4.4 kgfmm) was applied per collision, and the number of times until peeling occurred on the coating surface 32 was measured. The presence or absence of peeling was determined by observing the film surface 32 with a magnification of 15 times.

  The peel resistance index in the vertical direction shown in Table 1 indicates the result of the peel test of each measurement sample as an index, and the number of times until the film surface of the measurement sample of Conventional Example 2 peels is 100, The number of peeling of each sample was compared as a relative ratio. Therefore, the peeling resistance index of each measurement sample is larger than 100, indicating that the peeling is more difficult and the peeling resistance is excellent. This peel resistance mainly indicates the peel resistance from the vertical direction of the film. From the results shown in Table 1, the samples of Examples 1 to 10 containing a predetermined amount of boron, oxygen, or carbon It turns out that it is excellent in the peeling resistance of the perpendicular direction rather than the sample of Comparative Examples 1-8 which does not contain fixed amount boron, oxygen, or carbon.

(Peel test: horizontal direction)
This peel test is a peel test for a force applied in parallel (horizontal) to the sliding surface on which the film is formed by the ion plating method, and was performed using a scratch test apparatus 41 shown in FIG. The scratch test apparatus 41 shown in FIG. 3 presses the indenter 42 on the measurement sample 44 (20 mm × 10 mm × thickness 5 mm) placed on the table 43, and moves the sample 44 in that state. (Acoustic Emission) A device for detecting by the detector 45. In this application, it measured on the conditions of load load speed: 100N / min, table speed: 10mm / min, AE sensitivity: 1.2, indenter tip: R0.2mm. In the evaluation, the number of cracks generated by a scratch test was calculated, and the number of cracks generated per predetermined area was compared to evaluate the index. 4A and 4B are micrographs of the sample surface after the scratch test. FIG. 4A shows the measurement result of the sample of Example 2, and FIG. 4B shows the measurement result of the sample of Conventional Example 2. FIG. 5 is a cross-sectional photograph of the sample shown in FIG.

  The peel resistance index in the horizontal direction shown in Table 1 indicates the result of the scratch test of each measurement sample as an index. The number of occurrences of cracks in the measurement sample of Conventional Example 2 is assumed to be 100, and the cracks of each sample with respect thereto The number of occurrences was compared as a relative ratio. Therefore, as the peel resistance index of each measurement sample is smaller than 100, cracks are less likely to occur, indicating that the peel resistance (also referred to as crack resistance) is superior. This peel resistance mainly indicates the peel resistance from the horizontal direction of the film. From the results shown in Table 1, the samples of Examples 1 to 10 and Comparative Examples 1 to 8 having a predetermined range of porosity. It is understood that the horizontal direction peeling resistance is superior to the samples of Conventional Examples 1 to 6 having no porosity in a predetermined range. In addition, the degree of porosity can be observed from the photographs shown in FIGS.

(Other evaluation)
The orientation of CrN was measured by an X-ray diffractometer (manufactured by Rigaku Corporation, model number: RINT2500), evaluated by comparison with ICDD (International Center for Diffraction Data) for CrN, and compared by the relative value of diffraction intensity with respect to ICDD. Sometimes, it was displayed on the surface showing the largest relative value. The results are shown in Table 1. In addition, the composition of components such as B, O, and C in the film was quantified using a backscattering measurement device (manufactured by Nissin High Voltage Co., Ltd.) Further, the porosity of the film is obtained by image analysis of black and white appearing on the cross section of the film, and the porosity is measured, and the holes at that time are observed in a form appearing as a black portion as shown in FIG. . The film thickness was calculated from the cross-sectional observation.

  From the above results, the measurement samples of Examples 1 to 10 according to the present invention have a smaller porosity and can be obtained as a dense film as compared with the conventional film whose main orientation is the {111} plane of CrN. As a result, it was possible to obtain a film exhibiting excellent peeling resistance, abrasion resistance and scuff resistance, and in particular, a result that was strong against a force applied horizontally and parallel to the sliding surface was obtained. .

It is a block diagram of the configuration of an Amsler type wear tester used for measurement. It is a block diagram of the configuration of an impact test apparatus used for measurement. It is a block diagram of the configuration of a scratch test apparatus used for measurement. It is an electron micrograph of the sample surface after a scratch test. It is a cross-sectional photograph of the measurement sample shown in FIG.

Explanation of symbols

20 Amsler type wear tester 21 Measurement sample 22 Counterpart material 23 Lubricating oil 31 Impact test device 32 Coating surface 33 Spring 34 Indenter 35 Die 41 Scratch test device 42 Indenter 43 Table 44 Measurement sample 45 AE detector

Claims (3)

A sliding member in which a film mainly composed of chromium nitride is formed on a sliding surface by an ion plating method,
The coating has a {200} plane of CrN as a main orientation, contains 0.05% by mass to 20% by mass of boron, and has a porosity of 0.5% to 20%. A sliding member characterized.   The sliding member according to claim 1, wherein the film has a content of either one or both of oxygen and carbon of 15% by mass or less.   The sliding member according to claim 1 or 2, wherein the sliding member is a piston ring for an internal combustion engine.

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