WO2015099148A1

WO2015099148A1 - Wear-resistant member and rolling support device provided with same, and shaft sealing device

Info

Publication number: WO2015099148A1
Application number: PCT/JP2014/084604
Authority: WO
Inventors: 和洋石川; 健司小松原; 諭史清田; 織田　武廣; 裕也中尾
Original assignee: 京セラ株式会社
Priority date: 2013-12-26
Filing date: 2014-12-26
Publication date: 2015-07-02
Also published as: JP6075811B2; JPWO2015099148A1

Abstract

　[Problem] To provide a highly durable wear-resistant member having suitable lubricant-retaining ability, a rolling support device provided with the wear-resistant member, and a shaft sealing device. [Solution] A wear-resistant member comprising a silicon nitride ceramic having silicon nitride columnar crystals, holes and first columnar crystals comprising silicon nitride being present on the surface of the silicon nitride ceramic, second columnar crystals comprising silicon nitride having a larger diameter than the first columnar crystals being intermingled inside the holes, and the number of holes having a maximum diameter of 3 µm to 9 µm per 1.2 mm² of area in the surface being 5 to 28. A rolling support device provided with the wear-resistant member, and a shaft sealing device.

Description

Abrasion resistant member, rolling support device including the same, and shaft seal device

The present invention relates to a wear-resistant member, a rolling support device including the same, and a shaft seal device.

Conventionally, good sliding characteristics have been achieved in ball screws, linear guides, rolling support devices such as rolling bearings used in wind power generators, construction machinery or steel rolling mills, and shaft sealing devices such as mechanical seal rings. A wear-resistant member made of a ceramic sintered body is used for the required portion.

Such a ceramic sintered body is usually manufactured by molding and firing ceramic powder, and then densifying using a hot isostatic pressing method (HIP method), and is a wear-resistant member. Various silicon nitride sintered bodies have been studied as ceramic sintered bodies.

For example, Patent Document 1 contains silicon nitride particles and a sintering aid component containing a rare earth element in the range of 1 to 6% by mass and Al in the range of 0.5 to 6% by mass, Further, at least one metal element selected from Ti, Zr, Hf, W, Mo, Ta, Nb and Cr is contained in a range of 0.01% by mass to 5% by mass as a single metal element or a compound of the metal element. In the silicon nitride sintered body, the needle-like crystal particles having a major axis L of 10 μm or less and a ratio of the major axis L to the minor axis S (L / S) of 5 or more are sintered with silicon nitride. Within the crystal structure of the body, the area ratio is in the range of 50% to 80%, the maximum diameter of voids present in the silicon nitride sintered body is 2 μm or less, and the number of voids is 30 × 30 μm A silicon nitride sintered body having 5 or less in the range has been proposed. .

JP 2013-234120 A

In the rolling elements or sliding bodies and the members that respectively hold the rolling elements and the sliding bodies, a lubricant is used in order to suppress direct contact, but the silicon nitride-based sintering proposed in Patent Document 1 is used. When the maximum diameter of pores is as small as 2 μm or less, such as the body, or when the number is small, the amount of lubricant that can be retained during sliding is small, wear-resistant members or wear-resistant The durability is lowered by the direct contact between the sex member and the member holding the sex member, or by adhesion.

On the other hand, if the pores of the sintered body are too large or the number thereof is too large, the amount of lubricant that can be retained increases, and although it does not easily come into direct contact or adhere, The amount of heat generated by the movement increases and the sliding characteristics deteriorate, and the durability decreases due to the low mechanical characteristics. In addition, in a low temperature environment of about −40 ° C., there is a problem that the sliding resistance at the time of starting increases rapidly.

Therefore, in recent years, there is a demand for an abrasion-resistant member that can hold a lubricant moderately and can be used for a long period of time.

The present invention has been devised to satisfy the above-described requirements, and provides a wear-resistant member having a high durability for a lubricant and having a high durability, a rolling support device including the same, and a shaft seal device. The purpose is to do.

The wear-resistant member of the present invention is made of a silicon nitride ceramic having a columnar crystal of silicon nitride, the first columnar crystal and pores made of silicon nitride are present on the surface, and the first column is formed inside the pores. The second columnar crystals made of silicon nitride having a diameter larger than that of the columnar crystals are interlaced with each other, and the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area of the surface is 5 or more. The number is 28 or less.

In addition, the rolling support device of the present invention includes a first member and a second member each having a raceway surface, and a plurality of rolling elements, and the first member and the second member are arranged to face each other, The rolling element is disposed between the raceway surfaces so as to be freely rotatable, and the rolling element is composed of the wear-resistant member having the above-described configuration.

The shaft seal device of the present invention includes a mechanical seal ring composed of a fixed member and a movable member, and at least one of the fixed member and the movable member is composed of an abrasion-resistant member having the above-described configuration. To do.

According to the wear-resistant member of the present invention, the lubricant can be appropriately retained and has high durability, so that it can be used for a long period of time.

Also, according to the rolling support device and the shaft seal device of the present invention, since it can be used for a long period of time, it has high reliability.

The rolling bearing which is an example of embodiment of the rolling support apparatus of this invention is shown, (a) is sectional drawing, (b) is a perspective view which shows the holder | retainer which comprises a rolling bearing. It is sectional drawing which shows an example of the shaft seal apparatus provided with the mechanical seal ring which consists of an abrasion-resistant member of this invention.

Hereinafter, an example of this embodiment will be described in detail.

The wear-resistant member of this embodiment is made of silicon nitride ceramics having a silicon nitride columnar crystal, and sometimes has a first columnar crystal (hereinafter simply referred to as a first columnar crystal) made of silicon nitride on the surface. ) And pores, and inside the pores, second columnar crystals made of silicon nitride having a diameter larger than that of the first columnar crystals (hereinafter sometimes simply referred to as second columnar crystals) are interlaced with each other. The number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area of the surface is 5 or more and 28 or less.

Here, the silicon nitride ceramic is a material containing 78% by mass or more of silicon nitride among all components constituting the ceramic, and the content is, for example, nitrogen (N) or silicon obtained by quantitative analysis. from the value of (Si), it may be obtained in terms of silicon nitride _(Si 3 _{N 4).} The surface on which the first columnar crystals and pores exist is a polished surface and a sliding surface. Note that the sliding surface is a sliding surface including not only the initial state but also a surface that newly appears after wearing after sliding.

The wear-resistant member of the present embodiment has the second columnar crystal because the second columnar crystal having a diameter larger than that of the first columnar crystal is present inside the pores so as to cross each other. Since the surface area inside the pores is larger than when the second columnar crystals are not interlaced, the amount of lubricant retained in the pores is increased. In addition, since the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area of the surface is 5 or more and 28 or less, an appropriate amount of lubricant is maintained without substantially impairing wear resistance. can do.

Further, when sliding between the wear-resistant members or between the wear-resistant member and the member holding the same, the lubricant existing between the sliding surfaces easily flows out of the sliding surfaces. However, the sliding surface, which is the surface, has 5 to 28 pores with a maximum diameter of 3 μm to 9 μm per 1.2 mm ² area, and the inside of the pores is thicker than the first columnar crystal. Since the second columnar crystals are interlaced with each other, the lubricant can be gradually supplied to the sliding surface without causing the lubricant to flow out instantaneously.

Therefore, the wear-resistant member of the present embodiment has a high durability because it becomes difficult for a shortage of lubricant to occur on the sliding surface and the sliding characteristics can be maintained over a long period of time.

Here, the state in which the diameter of the second columnar crystal is larger than that of the first columnar crystal can be confirmed by the following method. First, for example, 5 to 10 columnar crystals existing on the surface and pores are selected in an image with a magnification of 4000 to 10000 times taken using a scanning electron microscope (SEM), and the first existing on the surface. The width (W1) in the vertical direction (minor axis direction) at the midpoint in the longitudinal direction of one columnar crystal is measured. Further, the width (W2) at the midpoint in the longitudinal direction of the second columnar crystal existing in the pores is measured. A state where the average value of W2 is larger than the average value of W1 is that the diameter of the second columnar crystal is larger than that of the first columnar crystal. Here, the average value of W2 is preferably 1.5 times or more of the average value of W1.

In order to make the diameter of the second columnar crystal larger than that of the first columnar crystal, the effect of suppressing grain growth in the second columnar crystal existing inside the pores is adjusted by adjusting the nitrogen partial pressure during firing. A large amount of the metal element oxide may be volatilized to grow the second columnar crystal. At this time, the columnar crystals protruding on the surface of the silicon nitride ceramics are also grown, but the columnar crystals protruding on the surface of the siliconized ceramic are removed by polishing. There is no protrusion on the surface of the wear resistant member of this embodiment. Further, the first columnar crystal existing on the polished surface is constrained by the adjacent crystal, and the volatilization of the oxide of the metal element in the first columnar crystal is small, and the grains of the first columnar crystal Since the growth is suppressed, the mechanical strength of the wear resistant member is maintained.

In addition, the state in which the second columnar crystals are interlaced is an SEM image taken at a magnification of 4000 to 10,000 times, where the second columnar crystals are in contact with each other and their axes are at an arbitrary angle. The state of crossing. The second columnar crystals need only be crossed on the image. Actually, the second columnar crystals may be close to each other even if they are not in contact with each other.

In addition, the pores on the surface of the wear-resistant member of the present embodiment have a function of holding the lubricant. However, if the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area is less than 5, the pores are retained. The amount of lubricant that can be produced is not sufficient and the sliding properties cannot be maintained over a long period of time. On the other hand, when the number of pores with a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area exceeds 28, the mechanical properties are low, and there are problems such as chipping around the pores when sliding, resulting in durability. Lower. Further, in a low temperature environment of about −40 ° C., the sliding resistance at the start of sliding between the wear-resistant members or between the wear-resistant members and the members holding them may increase rapidly.

Further, the wear resistant member of this embodiment has a variation coefficient represented by √V / X of 0.05 or more, where √V is the standard deviation of the maximum pore diameter and X is the average value of the maximum pore diameter. It is preferable that it is 0.6 or less. When the coefficient of variation represented by √V / X is 0.05 or more and 0.6 or less, foreign substances contained in the lubricant, wear-resistant material generated during sliding, and the like can be accommodated in the pores. Since the lubricant can be retained, the sliding characteristics can be maintained over a long period of time. In addition, since abnormally large pores are less likely to be present on the surface, the occurrence of problems due to lack of pore outline portions is reduced, and high durability is achieved.

Here, the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area of the surface, the average value (X) of the maximum diameter of the pores, and the standard deviation (√V) of the maximum diameter of the pores are optically measured. Using a microscope, set the magnification to 100 times, select the area where the pore size and distribution are observed on average, and the area is 1.2 mm ² (for example, the horizontal length is 1.2 mm and the vertical length is A method called particle analysis of image analysis software “A image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd., hereinafter simply referred to as image analysis software) is applied to an image in a range of 1.0 mm). The setting conditions of this method are the brightness of the particles, the method of binarization, and the small figure removal area are dark, manual, and 0 μm, respectively, and a threshold value that is an index indicating the brightness of the image is set to each point ( Each pixel) is measured by setting it to 0.88 times the peak value of the histogram indicating the brightness of each pixel.

In the measurement method described here, pores having a maximum diameter of less than 3 μm are not included in the measurement because they do not contribute to retention of the lubricant and it is difficult to determine whether the pores are pores. In addition, “averagely observed” means that a region where crystals or pores having an abnormally large diameter exist only in one place is intentionally selected in a region observed at a magnification of 100 times. It's just an exclusion.

According to the measurement using the above-described image analysis software under such setting conditions, the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area of the surface, the average value (X) and standard deviation of the maximum diameter of the pores ( √V) can be obtained. The coefficient of variation (√V / X) can be obtained by dividing the standard deviation (√V) by the average value (X) of the maximum diameter of the pores. In the present embodiment, the maximum pore diameter on the surface is the maximum length of a certain pore obtained using the image analysis software.

In the wear-resistant member of this embodiment, it is preferable that the first columnar crystal on the surface has an average aspect ratio of 1.2 or more and 3.5 or less. When the average value of the aspect ratio of the first columnar crystals is 1.2 or more and 3.5 or less, the first columnar crystals are interlaced to increase fracture toughness and to form a dense structure with high hardness. Therefore, the durability of the wear resistant member is improved. The average aspect ratio is more preferably 1.8 or more and 3.5 or less.

Here, the average value of the aspect ratio of the first columnar crystal on the surface may be obtained in accordance with JIS R 1670-2006. Specifically, using an image with a magnification of 2000 times taken with an SEM, an area in which the size and distribution of columnar crystals are observed on the surface on average (the area is 2730.5 μm ² (the lateral length is 63.5 μm The vertical length is 43 μm)), and at least 100 of the first columnar crystals are measured. Then, the major axis and minor axis of the target first columnar crystal are measured, the aspect ratio (major axis / minor axis) is obtained, and the average value may be calculated.

Further, out of 100% of the area in the observation region on the surface of the wear-resistant member of the present embodiment, the total area of the first columnar crystals whose major axis is less than 3 μm is 50% or more, and the major axis is 5 μm or more. The total area of the first columnar crystals is preferably 10% or more. The remaining area corresponds to the first columnar crystal, grain boundary phase, and pores having a major axis of 3 μm or more and less than 5 μm. When the above-mentioned range is satisfied, the length of the cracks generated at the initial stage during sliding depends on the crystal grain size, but the total area of the first columnar crystals whose major axis is less than 3 μm 50% or more, the resulting cracks tend to be fine cracks, and even if these cracks progress, the growth of cracks stops due to the presence of large columnar crystals with a major axis of 5 μm or more. The wear resistant member has excellent durability.

The percentage of the total area of the first columnar crystals whose major axis is less than 3 μm and the percentage of the total area of the first columnar crystals whose major axis is 5 μm or more out of 100% of the area of the surface observation area is SEM. 4 areas where the distribution of crystals is observed on average from the area of 24574.5μm ² (the length in the horizontal direction is 190.5μm and the length in the vertical direction is 129μm) Select. The area per range is set to be, for example, 2730.5 μm ² (63.5 μm in the horizontal direction and 43 μm in the vertical direction). Then, the major axis and minor axis of the first columnar crystal in each range are measured, the area is calculated assuming that both crystals are elliptical, and the major area is less than 3 μm with the total area (4 × 2730.5 μm ² ) as the denominator. The total area of the first columnar crystals and the total area of the first columnar crystals whose major axis is 5 μm or more may be expressed as a percentage.

Further, the wear-resistant member of the present embodiment has a silicide formed of at least one of iron and tungsten (hereinafter sometimes simply referred to as silicide) on the surface, and an equivalent circle diameter of 0.05 μm or more. The number of silicides having a size of 5 μm or less is preferably 2.0 × 10 ⁴ pieces / mm ² or more and 2.0 × 10 ⁵ pieces / mm ² or less.

When the number of silicides having an equivalent circle diameter of 0.05 μm or more and 5 μm or less is 2.0 × 10 ⁴ pieces / mm ² or more and 2.0 × 10 ⁵ pieces / mm ² or less, the first columnar crystal is exposed to a high temperature. Even if a microcrack occurs in the inside, the presence of the silicide in the above-described range can suppress or deflect the microcrack, and thus has high fracture toughness at high temperatures. Further, in the sintering process, the presence of the silicide in the above-mentioned range is unlikely to hinder the growth of the first columnar crystals in the sintering process, and the first columnar crystals exist in an interlaced manner. Therefore, it has excellent mechanical properties.

Here, the presence of silicide consisting of iron and tungsten on the surface may be measured and identified using an X-ray diffractometer (XRD). It can also be confirmed by detecting iron and silicon or tungsten and silicon in a measurement using an energy dispersive X-ray analyzer (Energy Dispersive X-ray Spectroscopy: EDS). Further, the dispersal can be confirmed by SEM observation because these silicides are different in color tone from the crystal of silicon nitride, but in mapping using an electron beam microanalyzer (EPMA) This can also be confirmed by the fact that the location of silicon and the location of silicon overlap, or the location of tungsten and the location of silicon overlap.

Further, the number of silicides having an equivalent circle diameter of 0.05 μm or more and 5 μm or less can utilize a color tone difference from a silicon nitride crystal. For example, a portion where the presence of silicide is observed on the surface on average is selected using a SEM at a magnification of 2000 times, and an image in a range where the area becomes 2730.5 μm ² may be analyzed by image analysis software. At this time, the measurement conditions are as follows: the brightness of the particles is bright, the binarization method is manual, the small figure removal area is 0 μm, and the threshold value, which is an index indicating the brightness of the image, is set to 200 Good.

Further, it is preferable that the average value of the circularity in the above-described silicide is 0.6 or more and 0.9 or less. When the average circularity of the silicide is 0.6 or more and 0.9 or less, even if it is exposed to high temperature and thermal stress is generated in the silicide, the residual stress is easy to disperse. In addition, microcracks originating from the periphery of the silicide are less likely to occur, so that excellent mechanical properties can be maintained even at high temperatures.

In addition, the average value of the circularity of the silicide may be obtained by analyzing with image analysis software in the same manner as when measuring the number of silicides.

Further, the silicon nitride ceramic constituting the wear resistant member of the present embodiment may contain a metal element oxide. Here, the metal element oxide is at least one of aluminum oxide, calcium oxide, magnesium oxide, and rare earth element (RE) oxide. The metal element oxide is contained in the grain boundary phase and the columnar crystal. Will exist.

When the above-described metal element oxide is contained, the sintering of the silicon nitride ceramics that become the wear resistant member is promoted, so that the mechanical characteristics can be enhanced.

Here, in order to obtain silicon nitride ceramics having high thermal conductivity, an oxide of a rare earth element is included, and the rare earth element is at least one of erbium (Er), ytterbium (Yb), and lutetium (Lu). Is preferred. Moreover, since the rare earth element oxide has a small volume expansion due to temperature change (small thermal expansion coefficient), the inclusion of the rare earth element oxide can improve the thermal shock resistance of the wear resistant member made of silicon nitride ceramics. .

Next, as an example of the configuration of the wear-resistant member of this embodiment, in which silicon nitride ceramics having columnar crystals of silicon nitride contain a metal element oxide. The silicon nitride content is 78% by mass or more, and among the total 100% by mass of calcium oxide, aluminum oxide and rare earth element oxide, the content of calcium oxide is 0.3% by mass or more and 1.5% by mass or less. The content is 14.2% by mass or more and 48.8% by mass or less, and the balance is a rare earth element oxide.

Thus, by adjusting the content of silicon nitride and the composition and composition ratio of the oxide of the metal element that serves as a sintering aid, the bulk density of the silicon nitride ceramic is increased and the wear resistance is high. It can be a sex member.

And the structure of each content in the total of 100 mass% of the oxide of aluminum oxide, calcium oxide, and rare earth elements (RE) can be calculated | required as follows. First, the contents of Al, Ca, and RE are determined using an X-ray fluorescence analyzer (XRF) or an inductively coupled plasma (ICP) emission spectrometer (ICP), and aluminum oxide (Al ₂ O ₃ ) and oxidation are respectively obtained. Conversion to calcium (CaO) and rare earth element oxide (RE ₂ O ₃ ). Next, the values converted into oxides may be summed, the summed value may be used as the denominator, and the numerator may be expressed in percentage as the value converted into each oxide. In addition, the value converted into an oxide is the content of 100% by mass of all components constituting the silicon nitride ceramic.

The content of silicon nitride _(Si 3 _{N 4)} is or obtained by conversion from the Si content obtained by XRF or ICP on _Si 3 _{N 4,} Si ₃ from the N content was determined by nitrogen analysis apparatus it may be obtained in terms of N _4. Further, the content of components other than Si and N contained in the silicon nitride ceramics is obtained by XRF or ICP, and the values converted into oxides are totaled, and the value obtained by subtracting the total value from 100% by mass is nitrided. It is good also as content of silicon.

When silicon nitride ceramics contains silicon oxide formed by oxidation of part of silicon nitride, all oxygen contained in the silicon nitride ceramics using an oxygen analyzer (LE-CO, model TC-136) Measure the amount, determine the content of components other than Si and N determined by XRF or ICP, subtract the total amount of oxygen required for conversion of oxides of these components from the total amount of oxygen, The content of silicon oxide may be obtained by converting the content of O) to silicon oxide (SiO ₂ ). When silicon oxide is contained in the silicon nitride ceramic, the content of silicon nitride (Si ₃ N ₄ ) is determined from the content of Si (total silicon amount) obtained by XRF or ICP. What is necessary is just to convert using the value which deducted content of the silicon required for conversion.

FIG. 1 shows a rolling bearing which is an example of an embodiment of a rolling support device of the present embodiment, (a) is a sectional view, and (b) is a perspective view showing a cage of the rolling bearing shown in (a). FIG.

The rolling bearing 10 in the example shown in FIG. 1A includes a first member (outer ring) 11 and a second member (inner ring) 12 having

raceway surfaces

11a and 12a arranged to face each other, And a plurality of rolling elements 13 which are arranged between the raceway surfaces 11a and 12a so as to be freely rollable. When the rolling elements 13 roll, the first member (outer ring) 11 and the second member (inner ring) 12 One is configured to move relative to the other. The size of the rolling element 13 is, for example, a sphere having a diameter of 40 mm or more and 60 mm or less.

A counter bore 12b is formed on one side of the rolling element 13 on the raceway surface of the second member (inner ring) 12 so as to be inclined from the raceway surface 12a of the second member (inner ring) 12. The counter bore 12b is for facilitating the attachment of the rolling element 13 between the first member (outer ring) 11 and the second member (inner ring) 12. Further, the cage 14 shown in FIG. 1 (b) has an annular shape and holds the rolling elements 13 by pockets 14a arranged at equal intervals in the circumferential direction.

In the rolling support device (rolling bearing) 10 of the embodiment shown in FIG. 1, the rolling element 13 is made of the wear resistant member of the embodiment. As described above, the rolling elements 13 constituting the rolling support device 10 of the present embodiment are made of the wear-resistant member of the present embodiment, so that good sliding characteristics can be maintained even if used for a long time. Can be used continuously for a long time. Moreover, since the replacement frequency of the members is small, the operation efficiency can be improved. Needless to say, the first member (outer ring) 11 and the second member (inner ring) 12 are preferably made of the wear-resistant member of this embodiment.

FIG. 2 is a cross-sectional view showing an example of a shaft seal device including a mechanical seal ring made of an abrasion-resistant member according to this embodiment.

The shaft seal device 20 includes a mechanical seal ring 21 including a fixed member 21a that is an annular body and a movable member 21b that is an annular body having a convex portion, and at least one of the fixed member 21a and the movable member 21b is a main member. It consists of the abrasion-resistant member of embodiment.

Here, the mechanical seal ring 21 is attached between a rotating shaft 22 that transmits a driving force by a driving mechanism (not shown) and a casing 23 that rotatably supports the rotating shaft 22, and is movable with the fixed member 21a. Sliding surfaces 21 as and 21 bs with the member 21 b are installed so as to form a vertical surface with respect to the rotation shaft 22.

The fixing member 21a is supported by a buffer rubber 27 attached to the inside of the casing 23 that is an outer frame of the shaft seal device 20. In addition, a collar 26 fixed by a set screw 28, a coil spring 25, and a packing 24 are installed on the rotary shaft 22 in this order toward the mechanical seal ring 21, and the movable member 21b is supported by the packing 24 in a buffered manner. ing.

The fluid 30 is moved outside the shaft seal device 20 by the sealing action by the O-ring 29 provided between the packing 24 and the rotary shaft 22 and the sealing action of the sliding surfaces 21as and 21bs of the mechanical seal ring 21. Prevents leakage. A part of the fluid 30 enters between the sliding surfaces 21as and 21bs of the mechanical seal ring 21 and acts as a lubricating liquid.

In the shaft seal device 20 of the present embodiment, when the movable member 21b starts to slide, dynamic pressure is generated between the sliding surfaces 21as and 21bs, and the generated hydraulic pressure causes the lubricating liquid to flow into the sliding surface. It tends to flow out of 1as and 21bs, but at least one of the sliding surfaces 21as and 21bs as the surface has 5 to 28 pores with a maximum diameter of 3 to 9 μm per 1.2 mm ² area. Since the second columnar crystals having a diameter larger than that of the first columnar crystals are mixed with each other in the pores, the lubricating liquid does not instantaneously flow out by the dynamic pressure, and the sliding surfaces 21as and 21bs Can be gradually supplied.

Further, since the shaft seal device 20 of the present embodiment includes the mechanical seal ring 21 made of the wear-resistant member of the present embodiment, it maintains good sliding characteristics even if it is used for a long period of time. Can be used continuously for a long time. Moreover, since the replacement frequency of the members is small, the operation efficiency can be improved.

Next, an example of a method for manufacturing the wear resistant member of the present embodiment will be described.

First, silicon nitride powder and powders of calcium oxide, aluminum oxide and rare earth element oxide as a sintering aid are wet mixed using a barrel mill, rotary mill, vibration mill, bead mill or attritor, etc. Grind into a slurry.

In addition, the total of powders of calcium oxide, aluminum oxide and rare earth element oxides, which are sintering aids, is calculated when the sum of the silicon nitride powder and the sum of these sintering aid powders is 100% by mass. Further, it may be weighed so as to be 3 mass% or more and 18.2 mass% or less. The composition of each sintering aid includes, for example, a calcium oxide content of 0.3% by mass or more and 1.5% by mass or less, out of a total of 100% by mass of calcium oxide, aluminum oxide and rare earth element oxide, and aluminum oxide. The content of is 14.2 mass% or more and 48.8 mass% or less, and the balance is oxides of rare earth elements.

The silicon nitride powder used has a particle size (D ₉₀ ) of 3 μm or less with a cumulative volume of 90% when the sum of the cumulative volume of the particle size distribution curve is 100%, or in the pulverization described above. It is preferable to grind to 3 μm or less from the viewpoint of improving the sinterability and making the crystal structure columnar.

And after grinding | pulverization, organic binders, such as paraffin wax, polyvinyl alcohol (PVA), and polyethylene glycol (PEG), are mixed with a slurry at 1 mass% or more and 10 mass% or less with respect to the total 100 mass% of the added powder. Is preferred for formability.

Next, the slurry is passed through a sieve having a particle size number of 200 described in ASTM E 11-61 or a finer mesh than this mesh, and then granules are obtained by using a spray dryer.

Here, the maximum diameter of the pores existing on the surface of the wear-resistant member can be controlled by the average particle diameter of the granules. To make the maximum diameter of the pores 3 μm or more and 9 μm or less, the average particle diameter of the granules May be 30 μm or more and 80 μm or less. Moreover, what is necessary is just to change suitably the average particle diameter of a granule by adjusting the rotational speed of the rotary atomizer (atomizer) with which the spray dryer was equipped.

Next, the obtained granule is filled in a mold and molded by a uniaxial pressing method, and then a predetermined shape having a relative density of 45% or more and 60% or less by a cold isostatic pressing (CIP) method, for example, A spherical, flat or annular shaped body is used. From the viewpoint of improving the density of the molded body and the collapseability of the granules, the molding pressure in the uniaxial pressing method is preferably 10 to 30 MPa, and the molding pressure in the CIP method is preferably 50 to 100 MPa. The obtained molded body is degreased in a nitrogen atmosphere or a vacuum atmosphere. The degreasing temperature varies depending on the kind of the added organic binder, but it is preferably 900 ° C. or lower, and particularly preferably 500 ° C. or higher and 800 ° C. or lower.

Next, the shaped body is placed in a firing furnace in which a graphite resistance heating element used for firing a general silicon nitride shaped body is placed and fired. Regarding the temperature, the temperature is raised from room temperature to 300 to 1000 ° C. in a vacuum atmosphere, and then nitrogen gas is introduced to maintain the nitrogen partial pressure at 10 to 100 kPa. At this time, since the open porosity of the compact is about 40 to 55%, the compact is sufficiently filled with nitrogen gas. Then, the temperature is continuously increased and the temperature is maintained at 1750 ° C. for 1 to 2 hours in order to obtain a fine crystal structure. Thereafter, the temperature is further raised, and the firing temperature is set to 1800 ° C. or higher and 1860 ° C. or lower, and the holding time is 3 to 5 hours. Alternatively, the baking may be performed at a baking temperature of 1730 ° C. or higher and 1750 ° C. or lower and a holding time of 12 to 16 hours.

Here, when the firing temperature is set to 1800 ° C. or higher and 1860 ° C. or lower and the holding time is set to 3 to 5 hours, the oxide of the metal element in the second columnar crystal, which has the effect of suppressing grain growth, is volatilized. The second columnar crystal, which is less constrained from the adjacent crystal than the first columnar crystal, grows more grains, and the second columnar crystals having a diameter larger than the first columnar crystal cross each other inside the pores. There will be more than one. The same result as described above can be obtained even when the firing temperature is set to 1730 ° C. or higher and 1750 ° C. or lower and the holding time is set to 12 to 16 hours.

Here, in order to allow pores having a maximum diameter of 3 μm or more and 9 μm or less to exist in the range of 5 or more and 28 or less, the nitrogen pressure when held at the firing temperature may be controlled to 100 kPa or more and 100 kPa or less.

Further, in order to obtain a wear resistant member having a coefficient of variation represented by √V / X of 0.05 or more and 0.6 or less, a pressure of 150 MPa or more and 250 MPa or less by a hot isostatic pressing method (HIP method) after firing. Should be added.

Further, in order to obtain a wear-resistant member having an average aspect ratio of the first columnar crystal on the surface of 1.2 or more and 3.5 or less, the firing temperature may be 1810 ° C. or more and 1850 ° C. or less.

Further, out of 100% of the area in the surface observation region, the total area of the first columnar crystals whose major axis is less than 3 μm is 50% or more, and the total area of the first columnar crystals whose major axis is 5 μm or more is In order to obtain a wear-resistant member of 10% or more, a silicon nitride powder having a particle size (D ₅₀ ) with a cumulative volume of 50% of 1 μm or more and 2 μm or less is wet-mixed for 5 to 10 hours using a bead mill, particle size (D ₅₀₎ is, for example, may be a slurry ground to be 0.5μm or more 2μm or less.

In addition, a silicide composed of at least one of iron and tungsten exists on the surface, and the number of silicides having an equivalent circle diameter of 0.05 μm or more and 5 μm or less is 2.0 × 10 ⁴ pieces / mm ² or more and 2.0 × 10 ⁵ pieces. In order to obtain a wear resistant member having a thickness of / mm ² or less, at least one of ferric oxide powder and tungsten carbide powder is added to the silicon nitride powder and the sintering aid powder in the following amounts. That's fine. Specifically, 1 part by mass of ferric oxide powder having a specific surface area of 0.5 m ² / g or more and 50 m ² / g or less per 100 parts by mass of the silicon nitride powder and the sintering aid powder. The powder of tungsten carbide having a specific surface area of 0.5 m ² / g or more and 50 m ² / g or less may be added in an amount of 0.6 parts by mass or more and 0.9 parts by mass or less.

In addition, both iron silicide and tungsten silicide are interspersed, and the number of silicides having an equivalent circle diameter of 0.05 μm or more and 5 μm or less is 2.0 × 10 ⁴ pieces / mm ² or more and 2.0 × 10 ⁵ pieces / mm. ^In order to obtain a wear-resistant member having ² or less, 0.5 m ² / g to 50 m ² / g of ferric oxide and tungsten carbide powders of 0.5 to 1 part by mass and 0.25 parts by mass, respectively. What is necessary is just to add more than 0.6 parts by mass.

The ferric oxide powder added in this way reacts with silicon nitride in the firing step to release oxygen and produce iron silicide. Similarly, tungsten carbide powder reacts with silicon nitride in the firing step to desorb carbon and produce tungsten silicide.

Further, in order to obtain a wear resistant member having an average circularity of the silicide of 0.6 or more and 0.9 or less, the specific surface area of the ferric oxide powder and tungsten carbide powder to be added is 0.52 m ² / g or more. It may be 0.65 m ² / g or less.

Then, after subjecting the obtained sintered body to grinding as necessary, for example, with a lapping machine made of tin, the arithmetic average in JIS B 0601: 2013 (ISO 4287: 1997, Amd. 1: 1997) Polishing is performed so that the height (Ra) is 0.98 μm or less.

The above-described manufacturing method can provide a highly durable wear-resistant member having an appropriate lubricant holding performance, and can be suitably used for a rolling support device, a shaft seal device, and the like.

Hereinafter, examples of the present invention will be described in detail, but the present invention is not limited to these examples.

First, a silicon nitride powder having an average particle size of 2.6 μm and calcium oxide, aluminum oxide, and yttrium oxide powders were mixed to obtain a mixed powder. Then, this mixed powder was put into a vibration mill together with water as a solvent, and pulverized and mixed for 72 hours to prepare a slurry.

Next, after adding 5% by mass of polyvinyl alcohol (PVA) to the pulverized and mixed powder and removing foreign matters through the slurry through a mesh sieve having a particle size number of 200 described in ASTM E 11-61, Granules having an average particle size of 55 μm were obtained by using a dryer. And after filling this granule in a shaping | molding die and shape | molding by the uniaxial pressurization method, the spherical molded object with a relative density of 52.5% was obtained using CIP method. Here, the molding pressure in the uniaxial pressing method was 20 MPa, and the molding pressure in the CIP method was 75 MPa. Next, after degreasing in a nitrogen atmosphere at 600 ° C., it is placed in a firing furnace in which a graphite resistance heating element is installed, and fired at the nitrogen partial pressure, firing temperature and holding time shown in Table 1, A ligature was obtained. Then, the obtained sintered body was polished to obtain rolling elements (sample Nos. 1 to 9) having a diameter of 47.63 mm.

By ICP where, Si, Ca, Al, the content of Y was measured and converted to _{_{Si Si 3 N 4, Ca CaO}} , and Al and _Al 2 _O 3, Y to _Y 2 _{O 3,} Si ₃ N ₄ is 78 mass%, CaO is between 0.05 wt%, _Al 2 _{O 3} is 8.88 _wt%, Y 2 _{O 3} was 12.2 wt%.

Further, when columnar crystals existing on the surface and columnar crystals existing in the pores were measured using EDS, Si and N were confirmed, and it was found that the columnar crystals were made of silicon nitride.

In addition, the number of pores having a maximum diameter of 3 μm or more and 9 μm or less on the surface is determined by an image with a magnification of 100 using an optical microscope (area 1.2 mm ² (horizontal length 1.2 mm, vertical length 1.0 mm). )) Was obtained by applying a technique called particle analysis of image analysis software. The setting conditions in the particle analysis are as follows: the brightness of the particle is dark, the binarization method is manual, the small figure removal area is 0 μm, and the threshold value, which is an index indicating the brightness of the image, is set for each point in the image. It was measured by setting it to 0.88 times the peak value of the histogram indicating brightness.

In addition, in an image with a magnification of 6000, which was taken using an SEM, the width at the midpoint in the longitudinal direction of the first columnar crystal existing on the surface is W1, and the longitudinal direction of the second columnar crystal existing inside the pores The width at the midpoint was W2, and the number of samples was five. The average value of the widths W1 of the first columnar crystals each having five samples was M (W1), and the average value of the widths W2 of the second columnar crystals was M (W2).

In addition, the inside of the pores at a magnification of 6000 times taken with SEM was observed to confirm the presence or absence of the second columnar crystals.

Between the raceway surface of the first member (outer ring) and the raceway surface of the second member (inner ring) made of high carbon chrome bearing steel (the symbol of the type described in JIS G 4805-2008 is SUJ2). A rolling bearing provided with a sample (rolling element) was prepared and subjected to a fatigue test.

Here, the conditions of the fatigue test were as follows.
Maximum contact surface pressure: 3.2 GPa
Bearing rotation speed: 3000rpm
Lubricant: Kinematic viscosity (40 ° C) of poly-α-olefin grease lubricant: 600 mm ² / s
Temperature: Room temperature The vibration of the rolling bearing during rotation was monitored by a vibration detector, and the fatigue test was stopped when the rolling element was damaged and the vibration of the rolling bearing exceeded a predetermined value. Sample No. The relative value was calculated with reference to 1 as the life of the rolling element from the start of operation to the end of operation. The results are shown in Table 1.

As shown in Table 1, Sample No. Samples Nos. 4 to 8 are sample Nos. The life is longer than 1 to 3, 9 and is made of a silicon nitride ceramic having a silicon nitride columnar crystal, the first columnar crystal and pores exist on the surface, and the first columnar shape is inside the pores. Second columnar crystals having a diameter larger than that of the crystals are interlaced with each other, and the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm ² area of the surface is 5 or more and 28 or less. It was found that the wear resistance was excellent.

Sample No. shown in Example 1 No. 6 is fired by the same method as above, and then the temperature is 1580 ° C., the time is 1 hour, and the HIP treatment is performed at the pressure shown in Table 2, and the obtained sintered body is polished, whereby the diameter is 47.63 mm. Rolling elements (Sample Nos. 10 to 16) were obtained.

Then, the coefficient of variation represented by √V / X was determined by calculating the average value and standard deviation of the maximum pore diameter by the same method as the method for calculating the number of pores described in Example 1. Calculated from the deviation.

In addition, the same fatigue test as in Example 1 was performed, and Sample No. The relative value was calculated with the life of 10 as the reference value 1. The results are shown in Table 2.

As shown in Table 2, sample no. Samples 11 to 15 are sample Nos. It has been found that when the lifetime is longer than 10 and 16, and the coefficient of variation represented by √V / X is 0.05 or more and 0.6 or less, the wear resistance is further improved.

Sample No. shown in Example 1 Degreasing is carried out by the same method as in No. 6, and then calcined at the calcining temperature shown in Table 3, and the obtained sintered body is polished to obtain a rolling element having a diameter of 47.63 mm (sample Nos. 17 to 23). Obtained.

The average value of the aspect ratio of the first columnar crystal on the surface was determined according to JIS R1670-2006 using an image with a magnification of 2000 times taken with an SEM.

Further, Vickers hardness was determined in accordance with JIS R 1610-2003. Furthermore, JIS
Fracture toughness was determined according to the indenter press method defined in R 1607-2010 (ISO 15732-2003 (MOD)). The results are shown in Table 3.

As shown in Table 3, sample No. Samples 18 to 22 are sample Nos. Fracture toughness higher than 17 The hardness is higher than 23, and the average value of the aspect ratio of the first columnar crystal on the surface is 1.2 or more and 3.5 or less, and it turns out to be a wear-resistant member with excellent fracture toughness and hardness. It was.

Sample No. shown in Example 1 A mixed powder similar to that of No. 6 was prepared, put into a bead mill with water as a solvent, and pulverized and mixed for the time shown in Table 4 to prepare a slurry. Then, except that it was a molded body from which a spherical body having a diameter of 10 mm was obtained after polishing, degreasing was performed in the same manner as shown in Example 1, nitrogen partial pressure was 600 kPa, firing temperature was 1740 ° C., holding time Was fired for 14 hours, and the obtained sintered body was polished to obtain rolling elements (sample Nos. 24-27) having a diameter of 10 mm.

Then, the percentage of the total area of the first columnar crystals whose major axis is less than 3 μm and the percentage of the total area of the first columnar crystals whose major axis is 5 μm or more out of 100% of the area of the observation area on the surface of each sample. It was determined as follows. First, from the region having an area of 24574.5 μm ² observed at a magnification of 1000 times using an SEM, four regions in which the crystal distribution was observed on average (area 2730.5 μm ² per range) were selected. Then, the major axis and minor axis of the first columnar crystal in each range are measured, the area is calculated assuming that both crystals are elliptical, and the major area is less than 3 μm with the total area (4 × 2730.5 μm ² ) as the denominator. The total area of the first columnar crystals and the total area of the first columnar crystals whose major axis is 5 μm or more are expressed as percentages as molecules.

Next, in accordance with JIS R 1691-2011, a wear test was performed using sample Nos. 24-27. In the wear test, the disc-shaped test piece that is in sliding contact with the sample is made of SUJ2, the applied load is 10 N, the sliding speed of the disc-shaped test piece is 0.37 m / s, the sliding circle diameter is 14 mm, and the sliding distance. Was 2000 m, and ion-exchanged water was used as the lubricating fluid.

And the specific wear amount of each sample is calculated, and the sample No. The relative value was calculated as the reference value 1 for the specific wear amount of 27. The smaller this relative value, the smaller the specific wear amount. The results are shown in Table 4.

As shown in Table 4, sample no. 24 to 26 are sample Nos. As a result, the total area of the first columnar crystals whose major axis is less than 3 μm is 50% or more, and the major axis is 5 μm or more. It was found that the wear resistance is improved when the total area of a certain first columnar crystal is 10% or more.

Sample No. shown in Example 1 6 and a ferric oxide powder and a tungsten carbide powder having a specific surface area shown in Table 5 were prepared, and the ferric oxide powder and the tungsten carbide powder with respect to 100 parts by mass of the mixed powder were prepared. The addition amount was the addition amount shown in Table 5. The sample No. 1 of Example 1 was prepared from the slurry preparation step except that a molded body having a size capable of forming a test piece for measuring fracture toughness and mechanical strength was obtained. 6 was prepared by the same method as in Sample No. 6. 28-42 were obtained.

And, for each sample, the silicide names measured and identified by XRD are shown in Table 5. The number of silicides having an equivalent circle diameter of 0.05 μm or more and 5 μm or less is obtained by analyzing the SEM image at a magnification of 2000 times using image analysis software by utilizing the color difference with the crystal of silicon nitride. Asked. The setting conditions were measured by setting the brightness of the particles to light, the binarization method to be manual, the small figure removal area to 0 μm, and the threshold value, which is an index indicating the brightness of the image, to 200.

Next, test pieces for measuring the fracture toughness value and mechanical strength were cut out from each sample, and the fracture toughness value at 500 ° C. was measured according to JIS R 1617-2010. Also, JIS
In accordance with R 1601-2008 (ISO 14704-2000 (MOD)), the four-point bending strength F ₀ at room temperature was measured. The results are shown in Table 5.

As shown in Table 5, sample no. Samples Nos. 29-31, 34-36 and 39-41 are sample Nos. The fracture toughness value at a higher temperature is higher than that of Samples Nos. 28, 33 and 38. Number of silicides whose four-point bending strength is higher than 32, 37 and 42, and there are silicides of at least one of iron and tungsten on the surface, and the equivalent circle diameter is 0.05 μm or more and 5 μm or less Is 2.0 × 10 ⁴ pieces / mm ² or more and 2.0 × 10 ⁵ pieces / mm ² or less, it was found that excellent mechanical properties are obtained.

Sample No. shown in Example 1 6 and a ferric oxide powder and a tungsten carbide powder having a specific surface area shown in Table 6 were prepared, and the ferric oxide powder and the tungsten carbide powder with respect to 100 parts by mass of the mixed powder were prepared. The addition amount was the addition amount shown in Table 6. And from the slurry preparation process, sample No. 1 in Example 1 was obtained except that a molded body having a size capable of forming a test piece for measuring mechanical strength was used. 6 was prepared by the same method as in Sample No. 6. 43-60 were obtained.

Then, by the same method as in Example 5, the presence of the silicide was confirmed, and the circularity of the silicide was measured.

Next, a test piece for measuring the mechanical strength was cut out from each sample, and a four-point bending strength F ₀ at room temperature in accordance with JIS R 1601-2008 (ISO 14704-2000 (MOD)) and JIS R 1604- The 4-point bending strength F _{1 at} 1000 ° C. according to 2008 (ISO 17565-2003 (MOD)) was measured. Then, to calculate the reduction rate of the 4-point bending strength _{F 1} for four-point bending strength _{_{_{F 0 ΔF (= (F 0}}} -F 1) / F 0 × 100) (%). The results are shown in Table 6.

As shown in Table 6, sample No. 44-47, 50-53 and 56-59 are sample Nos. Results with smaller reduction rate ΔF than 43, 48, 49, 54, 55 and 60 were obtained, and the average circularity of silicide on the surface was 0.6 or more and 0.9 or less, which was excellent even at high temperatures. It was found that the mechanical properties can be maintained.

10: Rolling support device (rolling bearing)
11: First member (outer ring)
12: Second member (inner ring)
13: Rolling element 14: Cage 20: Shaft seal device 21: Mechanical seal ring 22: Rotating shaft 23: Casing 24: Packing 25: Coil spring 26: Collar 27: Buffer rubber 28: Set screw 29: O-ring 30: Fluid

Claims

Silicon nitride ceramics having silicon nitride columnar crystals, first columnar crystals made of silicon nitride and pores exist on the surface, and silicon nitride having a diameter larger than that of the first columnar crystals inside the pores And the number of pores having a maximum diameter of 3 μm or more and 9 μm or less per 1.2 mm 2 area of the surface is 5 or more and 28 or less. Wear-resistant member.
When the standard deviation of the maximum diameter of the pore is √V and the average value of the maximum diameter of the pore is X, the variation coefficient represented by √V / X is 0.05 or more and 0.6 or less. The wear-resistant member according to claim 1.
The wear-resistant member according to claim 1 or 2, wherein the first columnar crystal on the surface has an average aspect ratio of 1.2 to 3.5.
The total area of the first columnar crystals whose major axis is less than 3 μm out of 100% of the area in the observation region of the surface is 50% or more, and the total area of the first columnar crystals whose major axis is 5 μm or more The wear-resistant member according to any one of claims 1 to 3, wherein the wear-resistant member is 10% or more.
A silicide composed of at least one of iron and tungsten is present on the surface, and the number of silicides having an equivalent circle diameter of 0.05 μm or more and 5 μm or less is 2.0 × 10 4 / mm 2 or more. The wear-resistant member according to claim 1, wherein the wear-resistant member is 0 × 10 5 pieces / mm 2 or less.
The wear resistant member according to claim 5, wherein the silicide has an average circularity of 0.6 or more and 0.9 or less.
A first member and a second member each having a raceway surface;
A plurality of rolling elements,
The first member and the second member are arranged to face each other,
The rolling element is disposed between the raceway surfaces so as to freely roll,
A rolling support device, wherein the rolling element comprises the wear resistant member according to any one of claims 1 to 6.
Provided with a mechanical seal ring consisting of a fixed member and a movable member,
A shaft seal device, wherein at least one of the fixed member and the movable member is composed of the wear-resistant member according to any one of claims 1 to 6.