CN117303913A - High-performance silicon nitride sealing ring and preparation method thereof - Google Patents
High-performance silicon nitride sealing ring and preparation method thereof Download PDFInfo
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- CN117303913A CN117303913A CN202311358983.1A CN202311358983A CN117303913A CN 117303913 A CN117303913 A CN 117303913A CN 202311358983 A CN202311358983 A CN 202311358983A CN 117303913 A CN117303913 A CN 117303913A
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- pressure sintering
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- 229910052581 Si3N4 Inorganic materials 0.000 title claims abstract description 68
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 238000007789 sealing Methods 0.000 title claims abstract description 41
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 238000005245 sintering Methods 0.000 claims abstract description 82
- 239000000843 powder Substances 0.000 claims abstract description 66
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 34
- 239000002131 composite material Substances 0.000 claims abstract description 34
- 239000000395 magnesium oxide Substances 0.000 claims abstract description 26
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims abstract description 26
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims abstract description 26
- 239000011230 binding agent Substances 0.000 claims abstract description 23
- 229910000420 cerium oxide Inorganic materials 0.000 claims abstract description 20
- BMMGVYCKOGBVEV-UHFFFAOYSA-N oxo(oxoceriooxy)cerium Chemical compound [Ce]=O.O=[Ce]=O BMMGVYCKOGBVEV-UHFFFAOYSA-N 0.000 claims abstract description 20
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910000423 chromium oxide Inorganic materials 0.000 claims abstract description 19
- 238000002156 mixing Methods 0.000 claims abstract description 19
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 claims abstract description 19
- 239000002270 dispersing agent Substances 0.000 claims abstract description 17
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 17
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 17
- 238000000748 compression moulding Methods 0.000 claims abstract description 14
- 238000001694 spray drying Methods 0.000 claims abstract description 14
- 239000013078 crystal Substances 0.000 claims abstract description 12
- 238000000498 ball milling Methods 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 15
- 239000000463 material Substances 0.000 claims description 10
- 239000007789 gas Substances 0.000 claims description 9
- 239000002202 Polyethylene glycol Substances 0.000 claims description 7
- 229920001223 polyethylene glycol Polymers 0.000 claims description 7
- 229910019142 PO4 Inorganic materials 0.000 claims description 6
- 238000000465 moulding Methods 0.000 claims description 6
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 6
- 239000010452 phosphate Substances 0.000 claims description 6
- WGTYBPLFGIVFAS-UHFFFAOYSA-M tetramethylammonium hydroxide Chemical compound [OH-].C[N+](C)(C)C WGTYBPLFGIVFAS-UHFFFAOYSA-M 0.000 claims description 6
- PNGBYKXZVCIZRN-UHFFFAOYSA-M sodium;hexadecane-1-sulfonate Chemical compound [Na+].CCCCCCCCCCCCCCCCS([O-])(=O)=O PNGBYKXZVCIZRN-UHFFFAOYSA-M 0.000 claims description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims 2
- 229910021529 ammonia Inorganic materials 0.000 claims 1
- 238000005452 bending Methods 0.000 abstract description 7
- 239000003566 sealing material Substances 0.000 abstract description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 21
- 239000002245 particle Substances 0.000 description 13
- 238000000280 densification Methods 0.000 description 10
- 239000000203 mixture Substances 0.000 description 7
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 239000007791 liquid phase Substances 0.000 description 4
- 239000000919 ceramic Substances 0.000 description 3
- 229910000151 chromium(III) phosphate Inorganic materials 0.000 description 3
- IKZBVTPSNGOVRJ-UHFFFAOYSA-K chromium(iii) phosphate Chemical compound [Cr+3].[O-]P([O-])([O-])=O IKZBVTPSNGOVRJ-UHFFFAOYSA-K 0.000 description 3
- 239000002612 dispersion medium Substances 0.000 description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000009694 cold isostatic pressing Methods 0.000 description 2
- 238000000354 decomposition reaction Methods 0.000 description 2
- 238000009792 diffusion process Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- LJAOOBNHPFKCDR-UHFFFAOYSA-K chromium(3+) trichloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Cl-].[Cr+3] LJAOOBNHPFKCDR-UHFFFAOYSA-K 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 238000005324 grain boundary diffusion Methods 0.000 description 1
- GVALZJMUIHGIMD-UHFFFAOYSA-H magnesium phosphate Chemical compound [Mg+2].[Mg+2].[Mg+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O GVALZJMUIHGIMD-UHFFFAOYSA-H 0.000 description 1
- 239000004137 magnesium phosphate Substances 0.000 description 1
- 229960002261 magnesium phosphate Drugs 0.000 description 1
- 229910000157 magnesium phosphate Inorganic materials 0.000 description 1
- 235000010994 magnesium phosphates Nutrition 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 238000012856 packing Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910000166 zirconium phosphate Inorganic materials 0.000 description 1
- LEHFSLREWWMLPU-UHFFFAOYSA-B zirconium(4+);tetraphosphate Chemical compound [Zr+4].[Zr+4].[Zr+4].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O LEHFSLREWWMLPU-UHFFFAOYSA-B 0.000 description 1
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- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
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- C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
- C04B35/584—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides based on silicon nitride
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Abstract
The invention provides a high-performance silicon nitride sealing ring and a preparation method thereof, and relates to the technical field of sealing materials. The invention carries out ball milling and mixing on powder (90-95% of silicon nitride, 0.5-1% of magnesium oxide, 0.5-1% of cerium oxide, 1-3% of chromium oxide and 3-8% of yttrium oxide) with binder, dispersant and water by mass percent, and then spray drying to obtain composite powder; the composite powder and beta-Si are mixed 3 N 4 Mixing seed crystals, and performing compression molding to obtain a blank; and (3) carrying out sectional air pressure sintering on the blank in nitrogen to obtain the high-performance silicon nitride sealing ring. ExamplesThe experimental results of the high-performance silicon nitride sealing ring prepared by the preparation method provided by the invention show that the relative density can reach 99.99%, the hardness can reach HV1600, the bending strength can reach 852MPa, and the fracture toughness can reach 7.36 MPa.m 1/2 。
Description
Technical Field
The invention relates to the technical field of sealing materials, in particular to a high-performance silicon nitride sealing ring and a preparation method thereof.
Background
The mechanical seal is a new type of device used in centrifugal pump or other rotary machines, and compared with the soft packing seal used in the past, it has the advantages of good sealing performance, long service life, less power consumption, etc. The sealing ring is the most important element constituting the mechanical seal, which determines the service performance and life of the mechanical seal to a large extent. In order to meet the requirements of low wear and long service life of mechanical seals, sealing ring materials are often required to have high hardness and high fracture toughness.
The silicon nitride ceramic has the advantages of high hardness, high strength, wear resistance and corrosion resistance, and is a novel sealing ring material. However, the reaction sintering silicon nitride is basically used in the mechanical sealing industry at present, and the physical and chemical properties and the mechanical properties of the reaction sintering silicon nitride are very different from those of normal-pressure sintering silicon nitride. Silicon nitride is a strongly covalent bond compound, and it is difficult to achieve sintering densification because it has a low diffusion coefficient, a low volume diffusion and grain boundary diffusion rate that cause densification, and a low sintering driving force, and it is decomposed at a high temperature of 1700 ℃ or higher.
In addition, the sealing ring belongs to structural members, and the forming technology of the sealing ring determines the uniformity of a blank body and the capability of preparing parts with complex shapes to a great extent, so that the final performance of a product is affected. The compression molding is the preferred molding process of ceramic products due to the characteristics of high molding efficiency, accurate size and low cost. However, compression molding tends to have a density gradient and a density unevenness. Because the mechanical seal has strict requirements on the uniformity of the structural components of the sealing ring material, the uniformity of the blank body directly influences the performance of the blank body during molding, and therefore, the silicon nitride ceramic blank body prepared by compression molding in the prior art is difficult to meet the use requirements of the sealing ring.
Therefore, providing a method for preparing a high-performance silicon nitride sealing ring is a technical problem to be solved in the field.
Disclosure of Invention
The invention aims to provide a high-performance silicon nitride sealing ring and a preparation method thereof. The high-performance silicon nitride sealing ring prepared by the preparation method provided by the invention has the advantages of high density, good sealing performance, uniform components and density and excellent mechanical properties.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of a high-performance silicon nitride sealing ring, which comprises the following steps:
(1) Providing the following powder materials in percentage by mass: 90-95% of silicon nitride, 0.5-1% of magnesium oxide, 0.5-1% of cerium oxide, 1-3% of chromium oxide and 3-8% of yttrium oxide;
(2) Ball-milling and mixing the powder in the step (1), a binder, a dispersing agent and water, and then spray-drying to obtain composite powder;
(3) Mixing the composite powder obtained in the step (2) with beta-Si 3 N 4 Mixing seed crystals, and performing compression molding to obtain a blank;
(4) And (3) performing sectional air pressure sintering on the blank obtained in the step (3) in nitrogen to obtain the high-performance silicon nitride sealing ring.
Preferably, the binder in the step (2) includes one or more of polyethylene glycol, polyvinyl alcohol and phosphate inorganic binder.
Preferably, the dispersant in the step (2) includes one or more of ammonia water, tetramethylammonium hydroxide and sodium hexadecyl sulfonate.
Preferably, the mass ratio of the powder material to the binder, the dispersing agent and the water in the step (2) is 100 (0.5-3.5) (0.01-2) (50-100).
Preferably, in the step (3), beta-Si 3 N 4 The adding amount of the seed crystal is 2-10% of the volume of the composite powder.
Preferably, the pressure of the compression molding in the step (3) is 100-180 MPa.
Preferably, the step (4) of the staged gas pressure sintering includes sequentially performing low gas pressure sintering and high gas pressure sintering.
Preferably, the nitrogen pressure of the low-pressure sintering is 0.1-2 MPa, the temperature of the low-pressure sintering is 1400-1600 ℃, and the time of the low-pressure sintering is 0.5-1 h.
Preferably, the nitrogen pressure of the high-pressure sintering is 3-8 MPa, the temperature of the high-pressure sintering is 1750-1850 ℃, and the time of the high-pressure sintering is 1-3 h.
The invention also provides a high-performance silicon nitride sealing ring prepared by the preparation method.
The invention provides a preparation method of a high-performance silicon nitride sealing ring, which comprises the following steps: mixing powder (90-95% of silicon nitride, 0.5-1% of magnesium oxide, 0.5-1% of cerium oxide, 1-3% of chromium oxide and 3-8% of yttrium oxide) with a binder, a dispersing agent and water in percentage by mass in a ball milling manner, and then spray-drying to obtain composite powder; the composite powder and beta-Si are mixed 3 N 4 Mixing seed crystals, and performing compression molding to obtain a blank; and (3) carrying out sectional air pressure sintering on the blank in nitrogen to obtain the high-performance silicon nitride sealing ring. According to the invention, magnesium oxide, cerium oxide, chromium oxide and yttrium oxide are used as composite sintering aids, so that the sintering temperature of densification of silicon nitride is effectively reduced, and the mechanical property of the ceramic material is improved while the density of the ceramic material is improved by adjusting the proportion of each sintering aid in powder; the water is used as a dispersion medium to be spray-dried to form composite powder with uniform composition, and the composite powder has the advantages of good fluidity, stable loose density and good forming property, can form a blank with uniform composition without cold isostatic pressing, and improves the mechanical property of ceramic materials; and then sintering the blank body by adopting a sectional air pressure sintering mode until the air holes are completely closed, and then performing secondary sintering to further remove the closed air holes so as to promote the densification of the ceramic material. Experimental results of the embodiment show that the relative density of the high-performance silicon nitride sealing ring prepared by the preparation method provided by the invention can reach 99.99%, the hardness can reach HV1600, the bending strength can reach 852MPa, and the fracture toughness can reach 7.36 MPa.m 1/2 。
Detailed Description
The invention provides a preparation method of a high-performance silicon nitride sealing ring, which comprises the following steps:
(1) Providing the following powder materials in percentage by mass: 90-95% of silicon nitride, 0.5-1% of magnesium oxide, 0.5-1% of cerium oxide, 1-3% of chromium oxide and 3-8% of yttrium oxide;
(2) Ball-milling and mixing the powder in the step (1), a binder, a dispersing agent and water, and then spray-drying to obtain composite powder;
(3) Mixing the composite powder obtained in the step (2) with beta-Si 3 N 4 Mixing seed crystals, and performing compression molding to obtain a blank;
(4) And (3) performing sectional air pressure sintering on the blank obtained in the step (3) in nitrogen to obtain the high-performance silicon nitride sealing ring.
The invention provides powder in the following mass percentages: 90 to 95 percent of silicon nitride, 0.5 to 1 percent of magnesium oxide, 0.5 to 1 percent of cerium oxide, 1 to 3 percent of chromium oxide and 3 to 8 percent of yttrium oxide. The invention takes magnesium oxide, cerium oxide, chromium oxide and yttrium oxide as composite sintering aids, effectively reduces the sintering temperature of densification of silicon nitride, and improves the mechanical property of the ceramic material while improving the density of the ceramic material by adjusting the proportion of each sintering aid in powder.
In the present invention, the powder comprises, in mass%, 90 to 95%, preferably 92 to 93% of silicon nitride. In the present invention, the average particle diameter of the silicon nitride is preferably 0.5 to 0.8 μm; alpha-Si in the silicon nitride 3 N 4 The volume content of (2) is preferably 95% or more. According to the invention, the sintering activity of the silicon nitride powder is improved by selecting the silicon nitride with proper particle size, so that the densification of the ceramic material is further promoted, and the material performance is improved; by controlling the phase content of the silicon nitride raw material, enough alpha phase is dissolved into liquid phase in the sintering process to grow beta-Si in a column shape 3 N 4 Further improving the fracture toughness of the silicon nitride ceramic material.
In the present invention, the powder comprises 0.5 to 1% by mass of magnesium oxide, preferably 0.6 to 0.8% by mass. In the invention, magnesium oxide is used as a sintering aid, and in the sintering process, the magnesium oxide reacts with silicon dioxide on the surface of silicon nitride to form a low-melting-point liquid phase, and then reacts with the silicon nitride to form a eutectic, so that the densification sintering temperature of the silicon nitride is reduced.
In the present invention, the average particle diameter of the magnesium oxide is preferably 0.5 to 2. Mu.m. The invention can be fully mixed with silicon nitride powder by controlling the particle size of magnesium oxide, promote sintering and further improve the compactness and the tissue uniformity of ceramic materials.
In the present invention, the powder comprises, in mass%, 0.5 to 1%, preferably 0.6 to 0.8% of cerium oxide. According to the invention, cerium oxide and magnesium oxide are added to be matched to serve as a composite sintering aid, and the mixture ratio of the cerium oxide and the magnesium oxide is adjusted, so that the cerium oxide and the magnesium oxide can react with silicon dioxide on the surface of silicon nitride to form a low-melting-point silicate liquid phase during sintering, and sintering densification is promoted, so that the obtained ceramic material has excellent mechanical properties.
In the present invention, the average particle diameter of the cerium oxide is preferably 0.5 to 2. Mu.m. The invention can be fully mixed with silicon nitride powder by controlling the particle size of cerium oxide, promote sintering and further improve the compactness and the tissue uniformity of ceramic materials.
In the present invention, the powder comprises 1 to 3% by mass of chromium oxide, preferably 1.5 to 2.5% by mass. According to the invention, the chromium oxide and the magnesium oxide are added to be matched, and the proportion of the chromium oxide and the magnesium oxide is adjusted, so that the shrinkage rate of the ceramic material in the sintering process is reduced, and the tissue uniformity of the material is improved.
In the present invention, the average particle diameter of the chromium oxide is preferably 0.5 to 2. Mu.m. The invention can be fully mixed with silicon nitride powder by controlling the particle size of the chromium oxide, thereby further improving the tissue uniformity of the ceramic material.
In the present invention, the powder comprises, in mass%, 3 to 8%, preferably 4 to 7%, more preferably 5 to 6% of yttrium oxide. The invention forms the composite sintering aid by adding yttrium oxide and magnesium oxide, reduces the sintering temperature by adjusting the mixture ratio of the yttrium oxide and the magnesium oxide, and improves the strength of the ceramic material.
In the present invention, the yttrium oxide preferably has an average particle diameter of 0.5 to 2. Mu.m. The invention can be fully mixed with silicon nitride powder by controlling the particle size of yttrium oxide, promote sintering and further improve the compactness and the tissue uniformity of ceramic materials.
After the powder is obtained, the powder, the binder, the dispersing agent and the water are subjected to ball milling and mixing, and then spray drying is carried out, so that the composite powder is obtained.
In the present invention, the binder preferably includes one or more of polyethylene glycol, polyvinyl alcohol, and a phosphate inorganic binder, more preferably polyethylene glycol and a phosphate inorganic binder; the mass ratio of the polyethylene glycol to the phosphate inorganic binder is preferably (3-5): 1, more preferably 4:1. In the present invention, the phosphate inorganic binder is preferably one or more of magnesium phosphate, zirconium phosphate, chromium phosphate and aluminum phosphate. The invention selects the binder of the above type, has higher stability, can improve the bonding performance between powder materials, and further improves the sintering density.
In the present invention, the dispersant preferably includes one or more of ammonia water, tetramethylammonium hydroxide, and sodium hexadecyl sulfonate. In the invention, the dispersing agent can promote the uniform dispersion of the powder in water, is favorable for obtaining spherical composite powder with uniform components and proper particle size during spray drying, and further improves the fluidity, bulk density and molding property of the composite powder.
In the present invention, the mass ratio of the powder to the binder, the dispersant and the water is preferably 100 (0.5 to 3.5): 0.01 to 2): 50 to 100, more preferably 100 (1 to 3): 0.05 to 1): 60 to 90, most preferably 100 (1.5 to 2.5): 0.1 to 0.5): 70 to 80. The invention adopts water as a dispersion medium, and can improve the dispersibility of the powder in water by controlling the mass ratio of the powder to the binder, the dispersing agent and the water, and the prepared slurry has low viscosity, is favorable for obtaining spherical composite powder with uniform components and proper particle size during spray drying, and further improves the fluidity, loose density and molding property of the composite powder.
The parameters of the ball milling mixing are not particularly limited, and the components can be fully and uniformly mixed to obtain the homogeneous slurry.
In the present invention, the spray drying is preferably performed in a nitrogen atmosphere. In the present invention, the inlet temperature of the spray drying is preferably 200 to 250℃and the outlet temperature of the spray drying is preferably 70 to 150 ℃.
After spray drying is completed, the invention preferably screens the spray dried product to obtain composite powder. In the present invention, the sieving is preferably a 100-200 mesh sieve.
After the composite powder is obtained, the invention combines the composite powder with beta-Si 3 N 4 And mixing the seed crystals, and performing compression molding to obtain a blank.
In the present invention, the beta-Si 3 N 4 The amount of seed crystal added is preferably 2 to 10% by volume of the composite powder, more preferably 4 to 8% by volume, and most preferably 5 to 6% by volume. The invention is beneficial to promoting the beta-Si in the liquid phase by adding the seed crystal 3 N 4 The sintering temperature can be further reduced by controlling the addition amount, and the mechanical property of the ceramic material is improved.
In the present invention, the pressure of the compression molding is preferably 100 to 180MPa, more preferably 120 to 160MPa. The composite powder prepared by the method has the advantages of uniform dispersion of components, good fluidity and formability, and uniform green body can be obtained by adopting common compression molding.
After the blank is obtained, the blank is subjected to sectional air pressure sintering in nitrogen, and the high-performance silicon nitride sealing ring is obtained.
In the present invention, the staged gas pressure sintering preferably includes low gas pressure sintering and high gas pressure sintering which are sequentially performed. The invention adopts two-step air pressure sintering, can inhibit the decomposition of silicon nitride and improve the sintering density.
In the present invention, the nitrogen pressure of the low-pressure sintering is preferably 0.1 to 2MPa, more preferably 0.2 to 1MPa, and most preferably 0.3 to 0.5MPa; the temperature of the low-pressure sintering is preferably 1400-1600 ℃, more preferably 1450-1550 ℃ and most preferably 1500 ℃; the time for the low-pressure sintering is preferably 0.5 to 1 hour, more preferably 1 hour. The invention firstly carries out sintering under lower air pressure and temperature, can avoid the decomposition of silicon nitride under the condition of adding a small amount of sintering auxiliary agent, and simultaneously forms isolated closed air holes by netlike continuous holes in the sintering process.
In the present invention, the nitrogen pressure of the high-pressure sintering is preferably 3 to 8MPa, more preferably 4 to 7MPa, and most preferably 5 to 6MPa; the high-pressure sintering temperature is 1750-1850 ℃, preferably 1780-1840 ℃ and most preferably 1800 ℃; the time for the high-pressure sintering is preferably 1 to 3 hours, more preferably 1.5 to 2 hours, and most preferably 2 hours. The invention carries out secondary sintering under higher pressure and temperature, can further eliminate closed pores and improve the density of ceramic materials.
According to the invention, magnesium oxide, cerium oxide, chromium oxide and yttrium oxide are used as composite sintering aids, so that the sintering temperature of densification of silicon nitride is effectively reduced, and the mechanical property of the ceramic material is improved while the density of the ceramic material is improved by adjusting the proportion of each sintering aid in powder; the water is used as a dispersion medium to be spray-dried to form composite powder with uniform composition, and the composite powder has the advantages of good fluidity, stable loose density and good forming property, can form a blank with uniform composition without cold isostatic pressing, and improves the mechanical property of ceramic materials; and then sintering the blank body by adopting a sectional air pressure sintering mode until the air holes are completely closed, and then performing secondary sintering to further remove the closed air holes so as to promote the densification of the ceramic material.
The invention also provides a high-performance silicon nitride sealing ring prepared by the preparation method. The high-performance silicon nitride sealing ring provided by the invention has the advantages of high density, good sealing performance, uniform components and excellent mechanical properties.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
(1) The mass percentages are as followsIs a powder of (1): 95% of silicon nitride, 0.5% of magnesium oxide, 0.5% of cerium oxide, 1% of chromium oxide and 3% of yttrium oxide; wherein the average grain size of the silicon nitride is 0.5 mu m, and the alpha-Si in the silicon nitride 3 N 4 The volume content of (2) is more than 95%; the average particle size of the magnesium oxide, cerium oxide, chromium oxide and yttrium oxide is 1 μm;
(2) Ball-milling and mixing the powder in the step (1), a binder, a dispersing agent and water, spray-drying, and sieving with a 100-mesh sieve to obtain composite powder; wherein the binder is polyethylene glycol and chromium phosphate, and the mass ratio of the polyethylene glycol to the chromium phosphate is 4:1; the dispersing agent is sodium hexadecyl sulfonate; the mass ratio of the powder to the binder, the dispersing agent and the water is 100:0.5:0.01:100; the inlet temperature of spray drying is 200 ℃ and the outlet temperature is 70 ℃;
(3) Mixing the composite powder obtained in the step (2) with beta-Si 3 N 4 Mixing seed crystals, and performing compression molding to obtain a blank; beta-Si 3 N 4 The adding amount of the seed crystal is 10% of the volume of the composite powder; the pressure of compression molding is 180MPa;
(4) Sequentially performing low-pressure sintering and high-pressure sintering on the blank obtained in the step (3) in nitrogen to obtain a high-performance silicon nitride sealing ring; the nitrogen pressure of the low-pressure sintering is 0.1MPa, the temperature is 1400 ℃ and the time is 0.5h; the nitrogen pressure of high-pressure sintering is 8MPa, the temperature is 1850 ℃ and the time is 3h.
The high-performance silicon nitride sealing ring prepared in the embodiment has the relative density of 99.99%, the hardness of HV1600, the bending strength of 852MPa and the fracture toughness of 7.2 MPa.m 1/2 。
Example 2
The powder in example 1 was replaced with: 90% of silicon nitride, 0.5% of magnesium oxide, 0.5% of cerium oxide, 1% of chromium oxide and 8% of yttrium oxide.
The high-performance silicon nitride sealing ring prepared in the embodiment has the relative density of 99.99%, the hardness of HV1586, the bending strength of 844MPa and the fracture toughness of 7.36 MPa.m 1/2 。
Example 3
The powder in example 1 was replaced with: 92% of silicon nitride, 0.5% of magnesium oxide, 0.5% of cerium oxide, 1% of chromium oxide and 6% of yttrium oxide, and the rest of the parameters are the same as those of example 1.
The high-performance silicon nitride sealing ring prepared in the embodiment has the relative density of 99.99%, the hardness of HV1590, the bending strength of 848MPa and the fracture toughness of 7.28 MPa.m 1/2 。
Example 4
The powder in example 1 was replaced with: 92% of silicon nitride, 1% of magnesium oxide, 1% of cerium oxide, 2% of chromium oxide and 4% of yttrium oxide.
The high-performance silicon nitride sealing ring prepared in the embodiment has the relative density of 99.99%, the hardness of HV1594, the bending strength of 848MPa and the fracture toughness of 7.24 MPa.m 1/2 。
Example 5
The sintering parameters in example 1 were replaced with: the nitrogen pressure of the low-pressure sintering is 2MPa, the temperature is 1600 ℃ and the time is 1h; the nitrogen pressure of high-pressure sintering is 6MPa, the temperature is 1800 ℃ and the time is 2h.
The high-performance silicon nitride sealing ring prepared in the embodiment has the relative density of 99.99%, the hardness of HV1598, the bending strength of 852MPa and the fracture toughness of 7.32 MPa.m 1/2 。
From the above examples, the high-performance silicon nitride sealing ring prepared by the preparation method provided by the invention has the advantages of high density, good sealing performance, uniform composition and density and excellent mechanical properties.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. A preparation method of a high-performance silicon nitride sealing ring comprises the following steps:
(1) Providing the following powder materials in percentage by mass: 90-95% of silicon nitride, 0.5-1% of magnesium oxide, 0.5-1% of cerium oxide, 1-3% of chromium oxide and 3-8% of yttrium oxide;
(2) Ball-milling and mixing the powder in the step (1), a binder, a dispersing agent and water, and then spray-drying to obtain composite powder;
(3) Mixing the composite powder obtained in the step (2) with beta-Si 3 N 4 Mixing seed crystals, and performing compression molding to obtain a blank;
(4) And (3) performing sectional air pressure sintering on the blank obtained in the step (3) in nitrogen to obtain the high-performance silicon nitride sealing ring.
2. The method of claim 1, wherein the binder in step (2) comprises one or more of polyethylene glycol, polyvinyl alcohol, and phosphate inorganic binder.
3. The method of claim 1, wherein the dispersant in step (2) comprises one or more of ammonia, tetramethylammonium hydroxide, and sodium hexadecylsulfonate.
4. The preparation method according to claim 1, wherein the mass ratio of the powder to the binder, the dispersant and the water in the step (2) is 100 (0.5-3.5): 0.01-2): 50-100.
5. The method according to claim 1, wherein in the step (3), β -Si is contained 3 N 4 The adding amount of the seed crystal is 2-10% of the volume of the composite powder.
6. The method according to claim 1, wherein the pressure of the molding in the step (3) is 100 to 180MPa.
7. The method according to claim 1, wherein the step (4) of stepwise gas pressure sintering includes sequentially performing low gas pressure sintering and high gas pressure sintering.
8. The method according to claim 7, wherein the nitrogen pressure of the low-pressure sintering is 0.1 to 2MPa, the temperature of the low-pressure sintering is 1400 to 1600 ℃, and the time of the low-pressure sintering is 0.5 to 1h.
9. The method according to claim 7, wherein the nitrogen pressure of the high-pressure sintering is 3 to 8MPa, the temperature of the high-pressure sintering is 1750 to 1850 ℃, and the time of the high-pressure sintering is 1 to 3 hours.
10. A high performance silicon nitride seal ring made by the method of any one of claims 1 to 9.
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