JP2015086116A - Silicon nitride sintered body and abrasion resistant member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon nitride sintered body having high abrasion resistance and an abrasion resistant member containing the silicon nitride sintered body.SOLUTION: There is provided a silicon nitride sintered body containing a hard crystal of at least one of titanium nitride or titanium carbonitride, having the content of titanium in terms of titanium nitride of 5 mass% to 10 mass% and containing at least one of aluminum and calcium in the hard crystal. By containing at least one of aluminum and calcium, hardness of the hard crystal becomes high and abrasion resistance is improved.

Description

  The present invention relates to a silicon nitride sintered body and an abrasion resistant member.

  Silicon nitride-based sintered bodies are used for various applications as structural ceramics because of their excellent mechanical properties, and studies are underway on their composition and composition in order to further improve their properties.

For example, in Patent Document 1, silicon nitride as a parent phase is composed of 66 to 99% by volume of β-Si ₃ N ₄ and the remaining α-Si ₃ N _4, and these silicon nitrides have a minor axis diameter of 500 nm or less. A silicon nitride-based sintered body composed of columnar crystals having an aspect ratio of 5 to 25 and equiaxed crystals having an average grain size of 300 nm or less and containing a titanium compound in the parent phase crystal grains and the grain boundary phase has been proposed. Yes.

JP-A-6-100370

  The silicon nitride-based sintered body proposed in Patent Document 1 is excellent in mechanical strength and fracture toughness, but has high wear resistance required in applications involving high-speed or long-time sliding. It did not have sex.

  The present invention has been devised to satisfy the above-described requirements, and provides a silicon nitride-based sintered body having high wear resistance and a wear-resistant member comprising the silicon nitride-based sintered body. .

  The silicon nitride-based sintered body of the present invention contains hard crystals of at least one of titanium nitride and titanium carbonitride, and the content of titanium in terms of titanium nitride is 5 mass% or more and 10 mass% or less. Includes at least one of aluminum and calcium.

  The wear resistant member of the present invention is characterized by comprising the silicon nitride sintered body having the above-described configuration.

  According to the silicon nitride-based sintered body of the present invention, it contains at least one of hard crystals of titanium nitride and titanium carbonitride, and the content of titanium converted to titanium nitride is 5 mass% or more and 10 mass% or less. Since the hard crystal contains at least one of aluminum and calcium, the hardness of the hard crystal is increased, and thus the wear resistance is excellent.

  Further, according to the wear-resistant member of the present invention, the wear-resistant member can be used over a long period of time because it is made of a silicon nitride-based sintered body having excellent wear resistance. It is possible to reduce the risk of causing problems on the installed equipment.

An example of the silicon nitride-based sintered body of the present embodiment is shown, (a) is a photograph of a cross section, and (b) is an analysis example of a hard crystal by energy dispersive X-ray analysis.

  The silicon nitride-based sintered body of the present embodiment includes at least one of hard crystals of titanium nitride and titanium carbonitride, and the content of titanium converted to titanium nitride is 5% by mass or more and 10% by mass or less. The hard crystal contains at least one of aluminum and calcium.

  By satisfying the above-described configuration, a silicon nitride sintered body having excellent wear resistance can be obtained. Thus, it is possible to have excellent wear resistance because the hardness of the hard crystal is increased by containing at least one of aluminum and calcium, and the content of titanium converted to titanium nitride is 5% by mass or more. This is because when the content is 10% by mass or less, hard crystals having increased hardness exist in the silicon nitride sintered body without hindering densification.

  And at least one of the hard crystals of titanium nitride and titanium carbonitride in the silicon nitride-based sintered body of this embodiment can be confirmed by measuring and identifying using an X-ray diffractometer (XRD). it can.

  The content of titanium converted to titanium nitride is determined from the content of titanium (Ti) obtained by a fluorescent X-ray analyzer (XRF) or an ICP (Inductively Coupled Plasma) emission analyzer (ICP). What is necessary is just to convert into TiN).

  Further, as to whether or not the hard crystal contains at least one of aluminum and calcium, the cross section of the silicon nitride sintered body is observed with a scanning electron microscope (SEM), and the attached energy dispersive X-ray analyzer When the hard crystal is irradiated with X-rays with (EDS), at least one of aluminum (Al) and calcium (Ca) may be detected. The cross section of the silicon nitride based sintered body is a mirror surface obtained by polishing.

  FIG. 1 shows an example of a silicon nitride-based sintered body of the present embodiment, where (a) is a photograph of a cross section, and (b) is an analysis example of hard crystals by energy dispersive X-ray analysis. FIG. 1A is a photograph taken with an SEM. The hard crystal 1 is confirmed to be white, and the silicon nitride crystal 2 is confirmed to be black around the hard crystal 1. FIG. 1B shows a case where X-rays are applied to the hard crystal 1 in an image taken with an SEM. When Al and Ca are detected, and when such a result is obtained, the hard crystal 1 is obtained. It contains at least one of aluminum and calcium.

  It is also possible to confirm whether or not the hard crystal contains at least one of aluminum and calcium by using a transmission electron microscope (TEM).

The silicon nitride-based sintered body of the present embodiment is a value obtained by converting silicon into silicon nitride, and may contain 80% by mass or more of all components constituting the silicon nitride-based sintered body, particularly 90% by mass. The above content is preferable because the mechanical properties tend to increase. As a measuring method, if content of silicon (Si) obtained by a fluorescent X-ray analyzer (XRF) or an ICP (Inductively Coupled Plasma) emission analyzer (ICP) is converted into silicon nitride (Si ₃ N ₄ ) Good.

The silicon nitride sintered body of the present embodiment has 2.1 × 10 ³ or more and 4.2 × 10 ³ or less hard crystals having an equivalent circle diameter of 0.2 μm or more and 1.0 μm or less per 1 mm ^{2 on} the surface. It is preferable that Here, the surface is a surface that forms the outside of the silicon nitride sintered body, but a mirror surface obtained by polishing the surface of the silicon nitride sintered body when measuring the number of hard crystals. Is also included.

Hard crystal having an equivalent circle diameter of 0.2 μm or more and 1.0 μm or less per 2.1 mm ^{2 on the} surface is 2.1.
When there are x10 ³ or more and 4.2 x 10 ³ or less, the wear resistance can be further improved.

And in order to obtain | require the number per 1 mm < ² > of the hard crystal whose circle equivalent diameter in a surface is 0.2 micrometer or more and 1.0 micrometer or less, first, the surface of a silicon nitride sintered body is grind | polished to make a mirror surface. Specifically, diamond abrasive grains having an average particle diameter of 0.05 to 0.15 μm may be supplied to a tin lapping machine to polish the surface of the silicon nitride based sintered body. Then, after the mirror surface obtained by polishing was washed, the surface was observed with a magnification of 1000 using an optical microscope, and the area photographed with a CCD camera was 1.2 × 10 ⁵ μm ^2.
Capture an image in the range of 150 μm in the horizontal direction and 80 μm in the vertical direction, and perform particle analysis using the image analysis software “A Image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Corp.). Can be obtained. As the setting conditions for the particle analysis, for example, the brightness is set to light, the binarization method is manually set, the small figure removal area is set to 0 μm, and a threshold value that is an index indicating the brightness of the image is set in the image. It is set to 0.88 times or less of the peak value of the histogram indicating the brightness of each point (each pixel). A scanning electron microscope may be used instead of the optical microscope.

  In addition, the silicon nitride sintered body of the present embodiment includes a silicide composed of at least one of molybdenum, chromium, iron, nickel, manganese, vanadium, niobium, tantalum, cobalt, and tungsten. The content is preferably 0.08% by mass or more and 0.16% by mass or less.

  When the above-described configuration is satisfied, the color tone of the silicon nitride sintered body can be darkened, and the mechanical properties at high temperatures are improved because the metal silicide is thermodynamically stable. be able to.

Examples of the silicide with the metal include, for example, a composition formula of MoSi ₂ , Mo ₃ Si ₂ , Mo ₅ Si ₃ , CrSi, Cr ₂ Si, Cr ₃ Si, CrSi ₃ , Cr ₅ Si ₃ , CrSi ₂ , FeSi ₃ , FeSi ₂ , FeSi, Fe ₂ Si, Fe ₂ Si ₃ , Fe ₃ Si, Fe ₃ Si ₂ , Fe ₃ Si ₄ , Fe ₃ Si ₇ , Fe ₅ Si ₂ , Fe ₅ Si ₃ , NiSi ₃ , NiSi _{2, NiSi, Ni 2 Si,} Ni 2 Si 3, Ni 3 Si, Ni 3 Si 2, Ni 3 Si 4, Ni 3 Si 7, Ni 5 Si 2, Ni 5 Si 3, MnSi, Mn 2 Si, MnSi 2 _{, VSi, VSi 2, VSi 3} , V 2 Si, V 3 Si 5, NbSi, NbSi 2, Nb 2 Si, Nb 5 Si 3, TaSi 2, T _{Si 3, Ta 2 Si 3,} Ta 5 Si, CoSi, are those represented by the _{CoSi 2, CoSi 2, Co 5} Si 3, WSi 2, W 3 Si 2 and _W 5 Si _3, as measured by XRD It can be confirmed by identifying.

In particular, when the metal silicide is a tungsten silicide, the W ₅ Si ₃ (411) with respect to the peak intensity I (WSi ₂ ) in the (101) plane and the (103) plane of WSi ₂ determined by XRD. The ratio I (W ₅ Si ₃ ) / I (WSi ₂ ) of the peak intensity I (W ₅ Si ₃ ) in the plane and the (321) plane is preferably 0.1 or more, and this ratio is 0.1 or more When it exists, heat resistance can be improved. Further, the tungsten silicide is preferably W ₅ Si ₃ (JCPDS # 81-1916).

The metal silicide is preferably interspersed as particles having an average particle size of 0.1 μm or more and 0.25 μm or less, and preferably an average particle size of 0.1 μm or more and 0.2 μm or less. Here, the average particle diameter of the metal silicide was determined by using a reflection electron image after setting the magnification so that the mirror-finished cross section was 20 or more using SEM. This is a value obtained by adopting the equivalent circle diameter in the grain size measuring method specified in 2006.

  The wear resistant member of the present embodiment is composed of the above-described silicon nitride sintered body of the present embodiment having excellent wear resistance, so that the wear amount is small, so that it can be used over a long period of time. In addition, it is possible to reduce the risk of causing problems in the mounting equipment due to wear powder or the like. Here, the wear resistant member is a member used for applications involving high speed or long-time sliding, for example.

  Next, an example of a method for manufacturing the silicon nitride sintered body of this embodiment will be described.

  Silicon nitride powder having a β conversion ratio of 20% or less, powders of aluminum oxide, magnesium aluminate and calcium carbonate as sintering aids, powders of titanium oxide, titanium nitride and titanium carbonitride as titanium sources At least one of them is selected. Then, various powders are weighed to make primary materials.

Here, the addition amount of each powder of aluminum oxide, magnesium aluminate, and calcium carbonate is, for example, 2% by mass to 6% by mass of aluminum oxide powder in the total of 100% by mass of the primary raw material, magnesium aluminate. The powder is 0.5 mass% to 2.5 mass%, and the calcium carbonate powder is 3.5 mass% to 7.5 mass%. In addition, when titanium nitride is used, the amount of powder serving as a titanium source is 5% by mass or more and 10% by mass or less of 100% by mass of the primary raw material, and the remainder is silicon nitride powder.

  Here, in order to obtain a silicon nitride sintered body containing at least one of aluminum and calcium in the hard crystal, the average particle diameter of each powder serving as a silicon nitride, aluminum oxide, calcium carbonate and titanium source is 0.5 The thickness may be set to μm to 1.5 μm, 1.6 μm to 2.2 μm, 1.2 μm to 2.0 μm, or 0.14 μm to 0.22 μm. If the titanium source powder is less than 0.14 μm, the size of the hard crystal is small, and the hard crystal cannot contain at least one of aluminum and calcium, and the effect of improving wear resistance cannot be obtained.

In addition, it contains a silicide composed of at least one of molybdenum, chromium, iron, nickel, manganese, vanadium, niobium, tantalum, cobalt and tungsten, and the content in terms of metal is 0.08% by mass or more and 0.16% by mass or less. In order to obtain a certain silicon nitride sintered body, an oxide powder of at least one of these metals is used, and 0.08 to 0.16 parts by mass in terms of metal is added to 100 parts by mass of the primary raw material. That's fine. The added metal oxide powder reacts with silicon during firing to release oxygen, thereby producing a thermodynamically stable silicide.

  Next, each powder weighed in a predetermined amount is mixed and pulverized together with a solvent by, for example, a barrel mill, a rotary mill, a vibration mill, a bead mill, a sand mill, an agitator mill, etc. to obtain a slurry. As the grinding media used in this grinding, those composed of a silicon nitride sintered body, a zirconium oxide sintered body, an aluminum oxide sintered body, etc. can be used. In order to reduce the size, it is preferable to use a grinding media made of a silicon nitride sintered body having the same material composition or approximate composition as the silicon nitride sintered body to be produced.

The pulverization is preferably performed until the particle size (D ₅₀ ) at which the cumulative volume becomes 50% becomes 0.8 μm or less from the viewpoint of improving the sinterability and making the crystal structure columnar.

In addition, moldability is obtained by weighing an organic binder such as paraffin wax, PVA (polyvinyl alcohol), PEG (polyethylene glycol), etc., in an amount of 1 to 10 parts by mass with respect to 100 parts by mass of the primary raw material, and mixing it with the slurry. Can be improved. Furthermore, you may add a thickening stabilizer, a dispersing agent, a pH adjuster, an antifoamer, etc.

In addition, in order to obtain a silicon nitride sintered body having 2.1 × 10 ³ or more and 4.2 × 10 ³ or less hard crystals having an equivalent circle diameter of 0.2 μm or more and 1.0 μm or less per 1 mm ^{2 on} the surface, For example, when the powder serving as the titanium source is titanium nitride and the addition amount is 7.5% by mass of 100% by mass of the primary material, the dispersant is 0.2 parts by mass or more and 0.6% by mass with respect to 100 parts by mass of the primary material. What is necessary is just to add a part or less.

And the slurry to which the organic binder etc. were added is spray-dried using a spray-drying apparatus, and the granulated granule is obtained. Next, the obtained granule is subjected to dry pressure molding or CIP molding (Cold Isostatic Pressing) to obtain a molded body. What is necessary is just to set the molding pressure at this time from a viewpoint of the improvement of the density of a molded object, and the collapsibility of a granule.

  Moreover, you may use shaping | molding methods, such as casting molding, injection molding, and tape shaping | molding. Moreover, after shaping | molding with each shaping | molding method, it is good also as a desired shape by cutting, laminating | stacking, or joining a molded object.

Next, the obtained molded body is placed in a carbon mortar whose surface is covered with silicon carbide or silicon nitride crystal particles, and degreased in nitrogen or vacuum. The degreasing temperature varies depending on the kind of the added organic binder, but is preferably 900 ° C. or less. In particular, it is preferably 450 ° C. or higher and 800 ° C. or lower. The removal of lipid components such as an organic binder from the molded body is called degreasing, and the degreased body is called a degreased body.

  The degreased body is held in a vacuum atmosphere at 700 ° C. to 900 ° C. for 0.5 to 1.5 hours and in a standard pressure nitrogen atmosphere at 1400 ° C. to 1600 ° C. for 2 to 4 hours. By maintaining the temperature below 1800 ° C. for 3 to 14 hours, it is possible to obtain the silicon nitride based sintered body of the present embodiment containing hard crystals containing at least one of aluminum and calcium. By this firing, even if titanium oxide is used as a titanium source, it is nitrided into titanium nitride, and a silicon nitride-based sintered body containing hard crystals of titanium nitride is obtained.

  Examples of the present invention will be specifically described below, but the present invention is not limited to these examples.

  First, silicon nitride powder having a β conversion rate of 10% or less, aluminum oxide, magnesium aluminate and calcium carbonate powders as sintering aids, and titanium source powder shown in Table 1 were prepared. Each was weighed and used as a primary material.

  Here, the addition amount of the magnesium aluminate powder is 1.5% by mass in 100% by mass of the primary raw material, and the addition amounts of the aluminum oxide, calcium carbonate and titanium source powders are as shown in Table 1, and the balance Was a silicon nitride powder. In addition, the addition amount of the powder of a titanium source is an addition amount when converted into titanium nitride.

  The average particle sizes of silicon nitride, aluminum oxide, magnesium aluminate, and calcium carbonate powders are 1.1 μm, 1.8 μm, 16.1 μm, 1.6 μm, and 1.1 μm, respectively. As shown in FIG.

Next, the primary raw material, the organic binder, and the solvent weighed in a predetermined amount were mixed and pulverized by a barrel mill until the particle size (D ₅₀ ) with a cumulative volume of 50% became 0.8 μm or less to obtain a slurry. As the grinding media used in this grinding, a grinding media made of a silicon nitride sintered body was used. Here, the addition amount of the organic binder was 5.5 parts by mass with respect to 100 parts by mass of the primary raw material. And the obtained slurry was spray-dried using the spray-drying apparatus, and the granulated granule was obtained.

Next, the obtained granules were subjected to dry pressure molding to obtain disk-shaped and prismatic shaped bodies. Next, the molded body was placed in a silicon carbide mortar and degreased by holding at 500 ° C. in a nitrogen atmosphere for 5 hours to obtain a degreased body. The obtained degreased body was held in a vacuum atmosphere at 800 ° C. for 1 hour, in a nitrogen atmosphere of standard pressure at 1500 ° C. for 3 hours, further heated up and held at 1750 ° C. for 3 hours, Disk-shaped and prismatic sintered bodies were obtained.

  Here, the disk-shaped sintered body is for evaluating wear resistance, and the dimensions are a diameter of 38 mm and a thickness of 3 mm. Further, in evaluating the wear resistance, one main surface is polished with diamond abrasive grains until the arithmetic average roughness Ra becomes 0.05 μm or less, and this is used as a test piece, in accordance with JIS R 1691-2011. A wear test was carried out.

In the wear test, the spherical test piece that was in sliding contact with the disk-shaped test piece was a SUS440C ball having a diameter of 10 mm, and ion-exchanged water was used as the lubricating fluid. The load was 10 N, the sliding speed of the disk-shaped test piece was 0.37 m / s, the sliding circle diameter was 14 mm, and the sliding distance was 2000 m.

  The prismatic sintered body is for evaluating mechanical strength, and the dimensions are 3 mm, 4 mm and 50 mm in thickness, width and length, respectively. Four-point bending strength was measured according to JIS R 1601-2008.

  In addition, each sample was measured using XRD and identified hard crystal names are shown in Table 1. In addition, Table 1 shows the values measured using ICP and converted to titanium nitride from the obtained titanium content.

  Furthermore, each sample was cut and mirror-finished by polishing, and the cross section was observed with an SEM, and X-rays were irradiated to the hard crystal with the attached EDS to confirm whether aluminum and calcium were detected. The results are shown in Table 1.

As shown in Table 1, Sample No. 2,4,6-9,11,13,15,17-20,22,23 have a specific wear amount as small as 0.37 (mm ³ / (N · m) or less), and titanium nitride and titanium carbonitride The hard crystal contains at least one hard crystal and the content of titanium converted to titanium nitride is 5% by mass or more and 10% by mass or less, and the hard crystal contains at least one of aluminum and calcium. It was found that the sintered body was excellent in silicon nitride, and had a four-point bending strength of 390 MPa or more.

Sample No. 1 of Example 1 Sample No. 8 was prepared by adding the addition amount of dispersant shown in Table 2 to the slurry used to prepare No. 8. 24-28, Sample No. 1 of Example 1. Sample No. 9 was prepared by adding the addition amount of dispersant shown in Table 2 to the slurry used to prepare No. 9. 29-33 were produced. In addition, the addition amount of a dispersing agent is with respect to 100 mass parts of primary raw materials, and the preparation methods other than having added the dispersing agent are the same as in Example 1. Then, a wear test was performed in the same manner as in Example 1.

Further, diamond abrasive grains having an average particle size of 0.05 to 0.15 μm were supplied to a tin lapping machine to polish the surface of the sample to obtain a mirror surface. After the mirror surface obtained by polishing was washed, the surface was observed with a magnification of 1000 using an optical microscope, and the area photographed with a CCD camera was 1.2 × 10 ⁵ μm ² (
By capturing images in the range of 150 μm in the horizontal direction and 80 μm in the vertical direction), and performing particle analysis using the image analysis software “A Image-kun” (registered trademark, manufactured by Asahi Kasei Engineering Corp.) The number of hard crystals having an equivalent circle diameter of 0.2 μm or more and 1.0 μm or less per 1 mm ² was determined. As the setting conditions for the particle analysis, for example, the brightness is set to light, the binarization method is manually set, the small figure removal area is set to 0 μm, and a threshold value that is an index indicating the brightness of the image is set in the image. It was set to 0.88 times or less of the peak value of the histogram indicating the brightness of each point (each pixel).

As shown in Table 2, there are 2.1, × 10 ³ or more and 4.2 × 10 ³ or less hard crystals with an equivalent circle diameter of 0.2 μm or more and 1.0 μm or less per 1 mm ^{2 on} the surface. It was found that the silicon nitride sintered body has wear resistance.

1: Hard crystal 2: Silicon nitride crystal

Claims (3)

  The hard crystal contains at least one of hard crystals of titanium nitride and titanium carbonitride, and the content of titanium in terms of titanium nitride is 5% by mass or more and 10% by mass or less, and the hard crystal contains at least one of aluminum and calcium. A silicon nitride-based sintered body characterized by the above. The hard crystal having an equivalent circle diameter of 0.2 μm or more and 1.0 μm or less is present in an area of 2.1 × 10 ³ or more and 4.2 × 10 ³ or less per 1 mm ^{2 on the} surface. Item 4. The silicon nitride based sintered body according to Item 1.   A wear-resistant member comprising the silicon nitride sintered body according to claim 1.