A silicon nitride composite material and a preparation method thereof, and a seal ring and a preparation method thereof

Abstract

The present application belongs to the technical field of seal ring processing, and particularly relates to a silicon nitride composite material and a preparation method thereof, and a seal ring and a preparation method thereof. By adding boron nitride into silicon nitride, the overall hardness and wear resistance of the silicon nitride composite material can be significantly improved. By adding a binding agent into the silicon nitride, the binding effect can be enhanced, and the mechanical properties of the material can be improved. By adding a sintering aid, a liquid phase can be provided in the sintering process, so as to accelerate sintering and improve the sintering effect. By SPS plasma sintering or HPHT high-temperature and high-pressure sintering, compared with the traditional sintering process, the sintering rate is improved, and the compactness and mechanical properties of the silicon nitride composite material can be significantly improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sealing ring processing, and particularly relates to a silicon nitride composite material and a preparation method thereof, and a sealing ring and a preparation method thereof. BACKGROUND

[0002] The sealing ring is a ring-shaped sealing piece, each contact surface needs to be hardened and polished, and is tightly pressed against the inner hole wall of the static piece by the elasticity to play a sealing role. The sealing ring is placed in the ring groove of the sleeve, the sleeve rotates with the shaft, and the sealing ring is tightly pressed against the inner hole wall of the static piece by the elasticity of the gap to play a sealing role. With the rapid development of science and technology, the performance requirements of the sealing ring are higher and higher, however, the existing sealing ring has low wear resistance and hardness, and is easily worn in use, which affects the use of the equipment. SUMMARY

[0003] The application aims to provide a silicon nitride composite material and a preparation method thereof, and a sealing ring and a preparation method thereof. The silicon nitride composite material provided by the application can be used to prepare the sealing ring, and the obtained sealing ring has high wear resistance and high hardness.

[0004] In order to achieve the above-mentioned purpose, the application provides the following technical scheme:

[0005] The application provides a silicon nitride composite material, which is made of raw materials including the following mass fractions:

[0006] Silicon nitride 30-70 parts, boron nitride 15-55 parts, binder 2-8 parts, and sintering aid 3-7 parts;

[0007] The binder includes one or more of titanium carbide, silicon carbide, titanium carbonitride, cobalt, molybdenum and tungsten carbide;

[0008] The sintering aid includes one or more of aluminum oxide, zirconium oxide, yttrium oxide and magnesium oxide.

[0009] Preferably, the particle size of the silicon nitride, boron nitride, binder and sintering aid is not greater than 8 mu m.

[0010] Preferably, the particle size of the silicon nitride is 1-5 mu m, the particle size of the boron nitride is 1-8 mu m, the particle size of the binder is 1-5 mu m, and the particle size of the sintering aid is 2-5 mu m.

[0011] The application further provides a preparation method of the silicon nitride composite material described in the above scheme, including the following steps:

[0012] The silicon nitride, boron nitride, binder and sintering aid are mixed, and then vacuum heat treatment and sintering are sequentially performed to obtain the silicon nitride composite material;

[0013] The sintering is SPS plasma sintering or HPHT high temperature and high pressure sintering.

[0014] Preferably, the SPS plasma sintering is: heating to 1500-2000℃ at a heating rate of 100-150℃ / min, and holding for 4-10min.

[0015] Preferably, the HPHT high temperature and high pressure sintering is: pressure of 3-6GPa, temperature of 1300-1600℃, and holding time of 3-10min.

[0016] Preferably, the vacuum heat treatment is: temperature of 400-900℃, vacuum degree of 10 -1 ~10 -3 Pa, and holding time of 1-2h.

[0017] Preferably, the vacuum heat treatment is preceded by molding the mixed mixture; the molding pressure is 20-40mPa, and the holding time is 5-10s.

[0018] The application also provides a sealing ring with hardness above 24GPa, wear ratio above 5900, and surface precision above 0.2μm.

[0019] The raw material of the sealing ring is the silicon nitride composite material according to the above scheme or the silicon nitride composite material obtained by the preparation method according to the above scheme.

[0020] The application also provides a preparation method of the sealing ring according to the above scheme, comprising the following steps:

[0021] The silicon nitride composite material is sequentially subjected to turning, milling, drilling and grinding to obtain the sealing ring.

[0022] The application provides a silicon nitride composite material. The application can significantly improve the overall hardness and wear resistance of the silicon nitride composite material by adding boron nitride to silicon nitride; the application can enhance the binding effect and improve the mechanical properties of the material by adding a binding agent to silicon nitride; and the application can provide a liquid phase in the sintering process by adding a sintering aid, thereby accelerating sintering and improving sintering effect.

[0023] The application also provides a preparation method of the silicon nitride composite material according to the above scheme. The application can significantly improve the compactness and mechanical properties of the silicon nitride composite material by SPS plasma sintering or HPHT high temperature and high pressure sintering, compared with traditional sintering process, while improving the sintering rate.

[0024] Further, the SPS plasma sintering is: heating to 1500-2000 DEG C at a heating rate of 100-150 DEG C / min, and holding for 4-10 min; the pressure of the HPHT high temperature and high pressure sintering is 3-6 GPa, the temperature is 1300-1600 DEG C, and the holding time is 3-10 min. The preparation method provided by the application has shorter time and higher preparation efficiency.

[0025] The application further provides a sealing ring with hardness above 24 GPa, wear ratio above 5900, and surface precision above 0.2 mu m; the raw material of the sealing ring is the silicon nitride composite material in the above scheme or the silicon nitride composite material obtained by the preparation method in the above scheme. The sealing ring provided by the application has high wear resistance and high hardness, and is not easy to wear, which is beneficial to the stable use of equipment.

[0026] The application further provides a preparation method of the sealing ring in the above scheme. The preparation method provided by the application has simple steps and is convenient to operate. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings in the following description only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0028] Figure 1 The structure schematic diagram of the sealing ring prepared for the embodiment 1 of the application. DETAILED DESCRIPTION

[0029] The application provides a silicon nitride composite material, which is made of raw materials including the following mass fractions:

[0030] Silicon nitride 30-70 parts, boron nitride 15-55 parts, binder 2-8 parts, and sintering aid 3-7 parts;

[0031] The binder includes one or more of titanium carbide, silicon carbide, titanium carbonitride, cobalt, molybdenum and tungsten carbide;

[0032] The sintering aid includes one or more of aluminum oxide, zirconium oxide, yttrium oxide and magnesium oxide.

[0033] In mass fractions, the raw materials of the silicon nitride composite material provided by the application include silicon nitride 30-70 parts, preferably 40-60 parts, and more preferably 50 parts; the particle size of the silicon nitride is preferably not more than 8 mu m, more preferably 1-5 mu m, and further preferably 3 mu m.

[0034] Based on the mass fraction of silicon nitride, the raw materials of the silicon nitride composite material provided by the present invention include 15 to 55 parts of boron nitride, preferably 25 to 45 parts, more preferably 35 parts; the particle size of the boron nitride is preferably not greater than 8 μm, more preferably 1 to 8 μm, and even more preferably 3 to 5 μm.

[0035] Based on the mass fraction of silicon nitride, the raw materials of the silicon nitride composite material provided by the present invention include 2 to 8 parts of binder, preferably 3 to 7 parts, more preferably 4 to 6 parts, and even more preferably 5 parts; the binder includes one or more of titanium carbide, silicon carbide, titanium carbonitride, cobalt, molybdenum and tungsten carbide, preferably one of silicon carbide and titanium carbide; the particle size of the binder is preferably not greater than 8 μm, more preferably 1 to 5 μm, and even more preferably 2 to 4 μm.

[0036] Based on the mass fraction of silicon nitride, the raw materials of the silicon nitride composite material provided by the present invention include 3 to 7 parts of sintering aid, preferably 4 to 6 parts, more preferably 5 parts; the sintering aid includes one or more of alumina, zirconium oxide, yttrium oxide and magnesium oxide, preferably alumina; the particle size of the sintering aid is preferably not greater than 8 μm, more preferably 2 to 5 μm, and even more preferably 3 to 4 μm.

[0037] The present invention also provides a method for preparing the silicon nitride composite material described above, comprising the following steps:

[0038] Silicon nitride, boron nitride, binder and sintering aid are mixed and then subjected to vacuum heat treatment and sintering in sequence to obtain silicon nitride composite material;

[0039] The sintering process is either SPS plasma sintering or HPHT high-temperature and high-pressure sintering.

[0040] In this invention, the mixing of silicon nitride, boron nitride, binder and sintering aid is preferably carried out by: adding the binder and sintering aid sequentially into a ball mill jar for ball milling while stirring, and then adding boron nitride and silicon nitride into the ball mill jar while stirring.

[0041] In this invention, the ball-to-material ratio of the ball mill is preferably 5-10:1, more preferably 6-9:1, and even more preferably 7-8:1; the ball milling speed is preferably 100-300 r / min, more preferably 150-250 r / min, and even more preferably 200 r / min; and the ball milling time is preferably 1-3 h, more preferably 1.5-2.5 h, and even more preferably 2 h.

[0042] In this invention, the mixture obtained by vacuum heat treatment is preferably shaped; the shaping is preferably compression molding; the shaping pressure is preferably 20-40mPa, more preferably 25-35mPa, and even more preferably 30mPa, and the holding time is preferably 5-10s, more preferably 6-9s, and even more preferably 7-8s; after shaping, the obtained product is preferably demolded to obtain a blank.

[0043] In this invention, the temperature of the vacuum heat treatment is preferably 400–900°C, more preferably 500–800°C, and even more preferably 600–700°C, and the vacuum degree is preferably 10. -1 ~10 -3 Pa, more preferably 10 Pa -2 ~10 -3 Pa, more preferably 10 Pa -2 Pa, the heat treatment time is preferably 1 to 2 hours, more preferably 1.3 to 1.8 hours, and even more preferably 1.5 hours; the apparatus for vacuum heat treatment is preferably a vacuum furnace.

[0044] In this invention, the sintering is SPS plasma sintering or HPHT high-temperature and high-pressure sintering; the SPS plasma sintering is preferably: sintering the block blank in a vacuum or argon or nitrogen atmosphere and holding it at a certain temperature; the SPS plasma sintering is more preferably: heating at a heating rate of 100-150℃ / min (referred to as the first heating) to 1500-2000℃ and holding at that temperature for 4-10min.

[0045] In this invention, the heating rate of the first heating is preferably 100-150℃ / min, more preferably 110-140℃ / min, and even more preferably 120-130℃ / min; the final temperature is preferably 1500-2000℃, more preferably 1600-1900℃, and even more preferably 1700-1800℃; and the holding time is preferably 4-10 min, more preferably 5-9 min, and even more preferably 6-8 min.

[0046] In this invention, the HPHT high-temperature and high-pressure sintering is preferably performed by assembling the block blanks into blocks and then sintering them in a high-temperature and high-pressure cavity; the pressure of the HPHT high-temperature and high-pressure sintering is preferably 3-6 GPa, more preferably 4-5 GPa, and even more preferably 4.5 GPa; the temperature is preferably 1300-1600℃ or 1400-1500℃; and the holding time is preferably 3-10 min, more preferably 5-7 min.

[0047] The present invention also provides a sealing ring with a hardness of 24 GPa or higher, a wear ratio of 5900 or higher, and a surface finish of 0.2 μm or higher.

[0048] The raw material for the sealing ring is the silicon nitride composite material described in the above scheme or the silicon nitride composite material obtained by the preparation method described in the above scheme.

[0049] In this invention, the size of the sealing ring is preferably determined according to different applications; in a specific embodiment of this invention, the thickness of the sealing ring is preferably 1.5-3mm, more preferably 1.8mm, the outer diameter is preferably 8-35mm, more preferably 10mm, the large inner diameter is preferably 6-30mm, more preferably 8mm, the small inner diameter is preferably 5-28mm, more preferably 6.5mm, and the depth of the large inner circle is preferably 1.15mm.

[0050] The present invention also provides a method for preparing the sealing ring described above, comprising the following steps:

[0051] The silicon nitride composite material was sequentially turned, milled, drilled, and ground to obtain a sealing ring.

[0052] In this invention, the turning, milling, drilling and grinding apparatus is preferably a machine tool.

[0053] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0054] Example 1

[0055] (1) Raw material preparation: 62 parts by weight of silicon nitride, 30 parts by weight of boron nitride, 3 parts by weight of silicon carbide, and 5 parts by weight of alumina sintering aid, to be used;

[0056] (2) Mixing and ball milling: First, add 3 parts by mass of silicon carbide and 5 parts by mass of alumina sintering aid into the ball mill jar in sequence while stirring. Then add 30 parts by mass of boron nitride and 62 parts by mass of silicon nitride into the ball mill jar while stirring until the mixture is uniform.

[0057] (3) Molding: The mixture is added to a pressing and molding equipment for pressing and molding, and a blank is obtained after demolding;

[0058] (4) Vacuum heat treatment: The blank is placed in a vacuum furnace for vacuum heat treatment at a vacuum degree of 10. -2 Heat-treated at PA for 1 hour, the resulting block-shaped blank is then removed for use.

[0059] (5) SPS plasma sintering: The block blank is heated to 1700℃ at a rate of 120℃ / min and held for 6min under vacuum atmosphere to obtain a silicon nitride composite material with high wear resistance and high hardness.

[0060] (6) The silicon nitride composite material is turned, milled, drilled and ground in sequence to obtain a sealing ring.

[0061] In this embodiment, the sealing ring has a hardness of 24 GPa, a wear ratio of 5900, a surface finish of 0.2 μm, and a structure as follows: Figure 1 As shown.

[0062] according to Figure 1 As can be seen, the sealing ring in this embodiment has a thickness of 1.8 mm, an outer diameter of 10 mm, a large inner diameter of 8 mm, a small inner diameter of 6.5 mm, a large inner depth of 1.15 mm, and a surface finish of 0.2 μm.

[0063] Example 2

[0064] (1) Raw material preparation: 45 parts by weight of silicon nitride, 45 parts by weight of boron nitride, 4 parts by weight of titanium carbide, and 6 parts by weight of alumina sintering aid, to be used;

[0065] (2) Ball milling: Add 4 parts by mass of titanium carbide and 6 parts by mass of alumina sintering aid to the ball milling jar in sequence and stir while adding. Then add 45 parts by mass of boron nitride and 45 parts by mass of silicon nitride to the ball milling jar and stir while adding until the mixture is uniform to obtain the mixture.

[0066] (3) Molding: The mixture is added to a pressing and molding equipment for pressing and molding, and a blank is obtained after demolding;

[0067] (4) Vacuum heat treatment: The blank is placed in a vacuum furnace for vacuum heat treatment at a vacuum degree of 10. -2 Heat-treated at PA for 1 hour to obtain a block-shaped billet, which is then removed and set aside for use.

[0068] (5) HPHT high temperature and high pressure sintering: The block blank is sintered by HPHT high temperature and high pressure, the pressure of HPHT high temperature and high pressure sintering is 4GPa, the temperature is 1600℃, and the holding time is 5min, to obtain a silicon nitride composite material with high wear resistance and high hardness.

[0069] (6) The silicon nitride composite material is turned, milled, drilled and ground in sequence to obtain a sealing ring.

[0070] In this embodiment, the hardness of the sealing ring is 26 GPa and the wear ratio is 7200.

[0071] Comparative Example 1

[0072] (1) Raw material preparation: 92 parts by weight of silicon nitride, 3 parts by weight of silicon carbide, and 5 parts by weight of alumina sintering aid, to be used;

[0073] (2) Ball milling: First, add 3 parts by mass of silicon carbide and 5 parts by mass of alumina sintering aid to the ball milling jar in sequence for ball milling while stirring. Then, add 92 parts by mass of silicon nitride to the ball milling jar while stirring until the mixture is uniform and a mixture is obtained.

[0074] (3) Molding: The mixture is added to a pressing and molding equipment for pressing and molding, and a blank is obtained after demolding;

[0075] (4) Vacuum heat treatment: The blank is placed in a vacuum furnace for vacuum heat treatment at a vacuum degree of 10. -2 Heat-treated at PA for 1 hour to obtain a block-shaped billet, which is then removed and set aside for use.

[0076] (5) SPS plasma sintering: The block blank is heated to 1700℃ at a rate of 120℃ / min and held for 6min under vacuum atmosphere to obtain a silicon nitride composite material with high wear resistance and high hardness.

[0077] (6) The silicon nitride composite material is turned, milled, drilled and ground in sequence to obtain a sealing ring.

[0078] In this embodiment, the hardness of the sealing ring is 14.5 GPa and the wear ratio is 3800.

[0079] Comparative Example 2

[0080] (1) Raw material preparation: 90 parts by weight of silicon nitride, 4 parts by weight of silicon carbide, and 6 parts by weight of alumina sintering aid, to be used;

[0081] (2) Ball milling: First, add 4 parts by mass of silicon carbide and 6 parts by mass of alumina sintering aid to the ball milling jar in sequence for ball milling while stirring. Then, add 90 parts by mass of silicon nitride to the ball milling jar while stirring until the mixture is uniform and a mixture is obtained.

[0082] (3) Molding: The mixture is added to a pressing and molding equipment for pressing and molding, and a blank is obtained after demolding;

[0083] (4) Vacuum heat treatment: The blank is placed in a vacuum furnace for vacuum heat treatment at a vacuum degree of 10. -2 Heat treatment at Pa for 1 hour yields a block-shaped billet, which is then removed for use.

[0084] (5) HPHT high temperature and high pressure sintering: The block blank is sintered by HPHT high temperature and high pressure, the pressure of HPHT high temperature and high pressure sintering is 4GPa, the temperature is 1600℃, and the holding time is 5min, to obtain a silicon nitride composite material with high wear resistance and high hardness.

[0085] (6) The silicon nitride composite material is turned, milled, drilled and ground in sequence to obtain a sealing ring.

[0086] In this embodiment, the hardness of the sealing ring is 16.8 GPa and the wear ratio is 4100.

[0087] As can be seen from the above embodiments, the sealing ring provided by the present invention has a hardness of over 24 GPa, a wear ratio of over 5900, and a surface finish of over 0.2 μm. The sealing ring provided by the present invention has high wear resistance and high hardness, is not easily worn, and is beneficial to the stable use of equipment.

[0088] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A silicon nitride composite material, made from the following raw materials in parts by weight: 62 parts silicon nitride, 30 parts boron nitride, 3 parts silicon carbide, and 5 parts aluminum oxide; or, 45 parts silicon nitride, 45 parts boron nitride, 4 parts titanium carbide, and 5 parts aluminum oxide; The silicon nitride has a particle size of 1-5 μm; the boron nitride has a particle size of 1-8 μm; the silicon carbide or titanium carbide has a particle size of 1-5 μm; and the alumina has a particle size of 2-5 μm. The preparation method of the silicon nitride composite material includes the following steps: The raw materials were mixed and then subjected to vacuum heat treatment and sintering in sequence to obtain silicon nitride composite material. The sintering is SPS plasma sintering or HPHT high-temperature and high-pressure sintering; the vacuum heat treatment is: vacuum degree 10 -2 The heat treatment was carried out at 1 Pa for 1 hour; the SPS plasma sintering was carried out by heating to 1700 ℃ at a heating rate of 120 ℃ / min and holding for 6 min; the HPHT high temperature and high pressure sintering was carried out at a pressure of 4 GPa, a temperature of 1600 ℃ and a holding time of 5 min.

2. The method for preparing the silicon nitride composite material according to claim 1, characterized in that, Includes the following steps: The raw materials were mixed and then subjected to vacuum heat treatment and sintering in sequence to obtain silicon nitride composite material. The vacuum heat treatment is performed with a vacuum degree of 10. -2 The heat treatment was carried out at 1 Pa for 1 hour; the SPS plasma sintering was carried out by heating to 1700 ℃ at a heating rate of 120 ℃ / min and holding for 6 min; the HPHT high temperature and high pressure sintering was carried out at a pressure of 4 GPa, a temperature of 1600 ℃ and a holding time of 5 min.

3. The preparation method according to claim 2, characterized in that, The mixture obtained before vacuum heat treatment is shaped; the shaped pressure is 20~40 mPa, and the holding time is 5~10 s.

4. A sealing ring, characterized in that, Hardness above 24 GPa, wear ratio above 5900, and surface finish above 0.2 μm; The raw material for the sealing ring is the silicon nitride composite material according to claim 1 or the silicon nitride composite material obtained by the preparation method according to claim 2 or 3.

5. The method for preparing the sealing ring according to claim 4, characterized in that, Includes the following steps: The silicon nitride composite material was sequentially turned, milled, drilled, and ground to obtain a sealing ring.

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