An injection molding process for large SiAlON ceramics

Abstract

The application relates to the technical field of ceramics, in particular to an injection molding process of large SiAlON ceramics, an injection molding process of large SiAlON ceramics, which comprises the following steps: A, ceramic powder preparation; B, feed preparation; C, injection molding; D, solvent debinding; E, thermal debinding and pre-sintering; and F, sintering. The large SiAlON ceramics produced by the injection molding process has high size precision, the size tolerance of the finished product after sintering can be controlled within 0.1%, the surface finish can reach 3-5 microns, the required machining allowance is extremely small, the cost required for the size precision machining in the later stage is greatly reduced, the production cycle is short, and the production efficiency is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramics, in particular to a kind of injection molding process of large SiAlON ceramic. BACKGROUND

[0002] Sialon ceramic is a kind of solid solution of Si3N4 and Al2O3 found by Japanese scholars and Jack and Wilson of England in the early 1970s when they studied Si3N4-Al2O3 system. They found that 60% to 70% of Al2O3 is dissolved into the crystal lattice of β-Si3N4, that is, Si atoms and N atoms in Si3N4 are partially replaced by Al or (Al+M) (where M is metal ions such as Mg2+, Ca2+, Li+ and La3+ and other rare earth ions) and O atoms, thus effectively promoting the sintering of silicon nitride and forming sialon ceramic. Sialon ceramic combines the excellent physical and mechanical properties of Si3N4 and Al2O3, with high hardness, wear resistance, strength and toughness, low thermal expansion coefficient, and comparable thermal shock resistance and oxidation resistance to SiC, so it has attracted widespread attention.

[0003] Large SiAlON ceramic structural parts such as engine turbine rotors have been reported, which are formed by traditional cold isostatic pressing, grouting and gel injection molding, but there are many drawbacks: 1. The size is difficult to unify, the required machining allowance is large, the utilization rate of waste materials is low, the size precision machining in the later stage occupies about 30% of the total cost, and the processing cost is high; 2. The forming cycle is long, and the production efficiency is low. SUMMARY

[0004] In order to overcome the shortcomings and deficiencies in the prior art, the purpose of the present application is to provide an injection molding process of large SiAlON ceramic, which has high size precision, the size tolerance of the finished product after sintering can be controlled within ±0.1%, the surface finish can reach 3-5 μm, the required machining allowance is extremely small, the cost required for size precision machining in the later stage is greatly reduced, the production cycle is short, and the production efficiency is greatly improved.

[0005] The purpose of the present application is achieved by the following technical scheme: an injection molding process of large SiAlON ceramic, comprising the following steps:

[0006] A, ceramic powder configuration: Si3N4, AlN, Y2O3, La2O3 and Al2O3 are put into a ball milling device for ball milling treatment with anhydrous ethanol as medium, and after ball milling, the SiAlON ceramic powder is obtained by drying and sieving;

[0007] B, feed preparation: the organic binder and SiAlON ceramic powder are added to the internal mixer, and fully melt and mix, after cooling, the small particle mixture is obtained by crushing treatment;

[0008] C, injection molding: the small particle mixture is added to the injection molding machine, and the regular blank is obtained;

[0009] D, solvent debinding: the regular blank is immersed in the dewaxing agent for solvent debinding treatment, and the first debinding blank is obtained after drying treatment;

[0010] E, hot debinding and pre-burning: the first debinding blank is placed in the heating furnace, and gradually heated and heat treated, and the pre-burning blank is obtained after furnace cooling;

[0011] F, sintering: the pre-burning blank is buried in the sintering aid, and sintering treatment is carried out in nitrogen atmosphere, and the regular SiAlON ceramic is obtained.

[0012] The ball milling time in step A is 8-10h.

[0013] The weight ratio of Si3N4, AlN, Y2O3, La2O3 and Al2O3 in step A is: Si3N4 85-88 parts, AlN 1-4 parts, Y2O3 0.8-2 parts, La2O3 5-8 parts and Al2O3 0.2-1 parts.

[0014] The weight ratio of the organic binder and SiAlON ceramic powder added in step B is 18-20:80-82.

[0015] The raw material ratio and the organic binder combination used in the application can greatly improve the density of large SiAlON ceramic products, and the density reaches 3.2-3.4g / cm 3 , the bending strength is 590-610MPa, and the hardness reaches 92-94HRA.

[0016] The organic binder is mixed by the following raw materials: PW organic binder 58-60 parts, PE organic binder 16-18 parts, PP organic binder 8-10 parts, EVA organic binder 5-8 parts and SA organic binder 3-5 parts.

[0017] The organic binder combination used in the application can effectively shorten the time required for solvent debinding, hot debinding and pre-burning, greatly shorten the total time required for the whole production process, effectively improve the production efficiency, and provide convenience for the industrialization of the application.

[0018] The working temperature of the internal mixer is 180-190℃, and the mixing time is 1.5-2h.

[0019] The working conditions of the injection molding machine in step C are: nozzle temperature 180-190℃, pressure 80-120bar, and speed 35-50%.

[0020] The dewaxing agent in step D is a mixture of triethanolamine with a concentration of 90% and aviation kerosene with a purity of 99% in a volume ratio of 8-6:2-3, the soaking temperature is 50-55℃, and the soaking time is 25-30h; after soaking, natural air drying is performed, and then the product is placed in an oven for baking at 75-85℃ for 3-4h.

[0021] The gradual temperature rising and holding treatment in step E is: temperature rising: rising to 100℃ within 400min, rising to 200℃ within 360min and holding the temperature for 60min, rising to 250℃ within 200min and holding the temperature for 120min, rising to 360℃ within 300min and holding the temperature for 30min, rising to 650℃ within 420min and holding the temperature for 30min, and rising to 1200℃ within 400min and holding the temperature for 120min.

[0022] The sintering aid in step F is a mixed powder agent composed of BN and Si3N4 in a weight ratio of 0.8-1.2:8-10.

[0023] The main crystal phase of Si3N4 in step A and the sintering aid is α-Si3N4>93%, D50<0.5μm, the specific surface area is about 17±0.5m 2 / g, and the loose bulk density is about 0.6±0.05g / ml.

[0024] In step F of the present application, the pre-sintered blank is buried in a mixed powder agent composed of BN and Si3N4 in a weight ratio of 0.8-1.2:8-10 for sintering, which can effectively improve the density and hardness of large SiAlON ceramics.

[0025] The sintering treatment in step F is: gradually increasing the sintering temperature to 1600℃ within 120min and holding the temperature for 60min, and then increasing the sintering temperature to 1800℃ within 90min and holding the temperature for 120min.

[0026] The present application has the advantages that: the present application is suitable for the production of large SiAlON ceramics, the large SiAlON ceramics produced by the injection molding process of the present application has high dimensional accuracy, the dimensional tolerance of the finished product after sintering can be controlled within ±0.1%, the surface finish can reach 3-5μm, the required machining allowance is extremely small, the cost required for the later dimensional accuracy machining is greatly reduced, the production cycle is short, and the production efficiency is greatly improved. DETAILED DESCRIPTION

[0027] For the convenience of the understanding of those skilled in the art, the application is further described below in conjunction with the examples, and the content mentioned in the examples is not a limitation to the application.

[0028] Example 1

[0029] A large-scale SiAlON ceramic injection molding process, comprising the following steps:

[0030] A, ceramic powder configuration: Si3N4, AlN, Y2O3, La2O3 and Al2O3 are put into a ball milling device for ball milling treatment with anhydrous ethanol as the medium, and after ball milling is completed, drying and sieving are carried out to obtain SiAlON ceramic powder;

[0031] B, preparation of feedstock: organic binder and SiAlON ceramic powder are added to a banbury mixer, and fully melt and mix, and after cooling, crushing treatment is carried out to obtain small particle mixture;

[0032] C, injection molding: the small particle mixture is added to an injection molding machine for injection to obtain a regular blank;

[0033] D, solvent degreasing: the regular blank is soaked in a dewaxing agent for solvent degreasing treatment, and after drying treatment, a first degreasing blank is obtained;

[0034] E, thermal degreasing and pre-burning: the first degreasing blank is put into a heating furnace, and gradually heated and heat treated, and after furnace cooling, a pre-burning blank is obtained;

[0035] F, sintering: the pre-burning blank is buried in a sintering aid, and sintering treatment is carried out under a nitrogen atmosphere to obtain a regular-shaped SiAlON ceramic.

[0036] The ball milling time in step A is 8h.

[0037] The weight ratio of Si3N4, AlN, Y2O3, La2O3 and Al2O3 in step A is: Si3N4 85 parts, AlN 1 part, Y2O3 0.8 part, La2O3 5 parts and Al2O3 0.2 part.

[0038] The weight ratio of the organic binder and SiAlON ceramic powder added in step B is 18:80.

[0039] The organic binder is mixed by the following weight parts of raw materials: PW organic binder 58 parts, PE organic binder 16 parts, PP organic binder 8 parts, EVA organic binder 5 parts and SA organic binder 3 parts.

[0040] The working temperature of the banbury mixer is 180℃, and the mixing time is 1.5h.

[0041] The working conditions of the injection molding machine in step C are: nozzle temperature 180°C, pressure 80 bar, and speed 35%.

[0042] The dewaxing agent in step D is a mixture of triethanolamine with a concentration of 90% and aviation kerosene with a purity of 99% in a volume ratio of 8:2, the soaking temperature is 50°C, the soaking time is 25h; after soaking, it is naturally dried and then placed in an oven at 75°C for 3h, and the soaking time is the time when the degreasing rate of the once-degreased blank reaches 80%.

[0043] The gradual temperature rising and holding treatment in step E is: temperature rising: gradually rising to 100°C within 400min; gradually rising to 200°C within 360min and keeping the temperature for 60min; gradually rising to 250°C within 200min and keeping the temperature for 120min; gradually rising to 360°C within 300min and keeping the temperature for 30min; gradually rising to 650°C within 420min and keeping the temperature for 30min; gradually rising to 1200°C within 400min and keeping the temperature for 120min.

[0044] The sintering aid in step F is a mixed powder of BN and Si3N4 in a weight ratio of 0.8:8.

[0045] The main crystal phase of Si3N4 in step A and the sintering aid is α-Si3N4>93%, D50<0.5μm, specific surface area about 17±0.5m 2 / g, and loose bulk density about 0.6±0.05g / ml.

[0046] The sintering treatment in step F is: gradually rising the sintering temperature to 1600°C within 120min and keeping the temperature for 60min, and then rising the sintering temperature to 1800°C within 90min and keeping the temperature for 120min.

[0047] Example 2

[0048] An injection molding process of large SiAlON ceramic, comprising the following steps:

[0049] A, ceramic powder configuration: Si3N4, AlN, Y2O3, La2O3 and Al2O3 are put into a ball milling device for ball milling treatment with anhydrous ethanol as medium, and after ball milling, drying and sieving, SiAlON ceramic powder is obtained;

[0050] B, preparation of feedstock: organic binder and SiAlON ceramic powder are added to an internal mixer, and fully melt mixed and crushed after cooling to obtain small particle mixture;

[0051] C. Injection molding: small granular mixture is added into the injection molding machine to obtain regular blank;

[0052] D. Solvent debinding: regular blank is soaked in the dewaxing agent for solvent debinding treatment, and after drying treatment, primary debinding blank is obtained;

[0053] E. Thermal debinding and pre-burning: primary debinding blank is placed in a heating furnace, and gradually heated and heat-treated, and after furnace cooling, pre-burning blank is obtained;

[0054] F. Sintering: pre-burning blank is buried in sintering aid, and sintering treatment is carried out in a nitrogen atmosphere to obtain regular-shaped SiAlON ceramic.

[0055] The ball milling time in step A is 9h.

[0056] The weight ratio of Si3N4, AlN, Y2O3, La2O3 and Al2O3 in step A is: Si3N4 87 parts, AlN 3 parts, Y2O3 1.5 parts, La2O3 7 parts and Al2O3 0.6 parts.

[0057] The weight ratio of organic binder and SiAlON ceramic powder added in step B is 19:81.

[0058] The organic binder is mixed by the following weight parts of raw materials: PW organic binder 59 parts, PE organic binder 17 parts, PP organic binder 9 parts, EVA organic binder 7 parts and SA organic binder 4 parts.

[0059] The working temperature of the internal mixer is 185℃, and the mixing time is 1.8h.

[0060] The working conditions of the injection molding machine in step C are: nozzle temperature 185℃, pressure 100bar, and speed 42%.

[0061] The dewaxing agent in step D is a mixture of triethanolamine with a concentration of 90% and aviation kerosene with a purity of 99% at a volume ratio of 7:2.5, the soaking temperature is 53℃, and the soaking time is 28h; after soaking, it is naturally dried, and then placed in an oven at 80℃ for 3.5h, the soaking time is the time when the debinding rate of the primary debinding blank reaches 80%.

[0062] The step E of gradually increasing temperature and holding temperature is: increasing temperature: increasing to 100℃ within 400min; increasing to 200℃ within 360min and holding the temperature for 60min; increasing to 250℃ within 200min and holding the temperature for 120min; increasing to 360℃ within 300min and holding the temperature for 30min; increasing to 650℃ within 420min and holding the temperature for 30min; increasing to 1200℃ within 400min and holding the temperature for 120min.

[0063] The sintering aid in the step F is a mixed powder of BN and Si3N4 with a weight ratio of 1:9.

[0064] The main crystal phase of Si3N4 in the step A and the sintering aid is α-Si3N4>93%, D50<0.5μm, specific surface area about 17±0.5m2 / g, and loose bulk density about 0.6±0.05g / ml. 2

[0065] The sintering treatment in the step F is: increasing the sintering temperature to 1600℃ within 120min and holding for 60min, then increasing the sintering temperature to 1800℃ within 90min and holding for 120min.

[0066] Example 3

[0067] A large-scale SiAlON ceramic injection molding process, comprising the following steps:

[0068] A, ceramic powder configuration: Si3N4, AlN, Y2O3, La2O3 and Al2O3 are put into a ball milling device for ball milling treatment with anhydrous ethanol as medium, and after ball milling, drying and sieving, SiAlON ceramic powder is obtained;

[0069] B, preparation of feedstock: organic binder and SiAlON ceramic powder are added to an internal mixer, and fully melt mixed and crushed after cooling to obtain small particle mixture;

[0070] C, injection molding: the small particle mixture is added to an injection molding machine for injection to obtain regular blank;

[0071] D, solvent debinding: the regular blank is immersed in a dewaxing agent for solvent debinding treatment, and after drying treatment, a first debinding blank is obtained;

[0072] E, thermal debinding and pre-sintering: the first debinding blank is put into a heating furnace and gradually increases temperature and holds temperature, and after furnace cooling, a pre-sintered blank is obtained;

[0073] ​F, sintering: embedding the pre-sintered blank into a sintering aid, and performing a sintering treatment under a nitrogen atmosphere to obtain a regular-shaped SiAlON ceramic.

[0074] The ball milling time in step A is 8-10h.

[0075] The weight ratio of Si3N4, AlN, Y2O3, La2O3 and Al2O3 in step A is: Si3N4 88 parts, AlN 4 parts, Y2O3 2 parts, La2O3 8 parts and Al2O3 1 part.

[0076] The weight ratio of the organic binder and SiAlON ceramic powder added in step B is 20:82.

[0077] The organic binder is mixed by the following weight parts of raw materials: PW organic binder 60 parts, PE organic binder 18 parts, PP organic binder 10 parts, EVA organic binder 8 parts and SA organic binder 5 parts.

[0078] The working temperature of the internal mixer is 190℃, and the mixing time is 2h.

[0079] The working conditions of the injection molding machine in step C are: nozzle temperature 190℃, pressure 120bar, and speed 50%.

[0080] The dewaxing agent in step D is a mixture of triethanolamine with a concentration of 90% and aviation kerosene with a purity of 99% in a volume ratio of 6:3, the soaking temperature is 55℃, and the soaking time is 30h; after soaking, it is naturally dried and then placed in an oven at 85℃ for 4h, and the soaking time is the time when the degreasing rate of the once-degreased blank reaches 80%.

[0081] The gradual heating and holding treatment in step E is: heating: gradually heating to 100℃ within 400min; gradually heating to 200℃ within 360min and keeping the temperature for 60min; gradually heating to 250℃ within 200min and keeping the temperature for 120min; gradually heating to 360℃ within 300min and keeping the temperature for 30min; gradually heating to 650℃ within 420min and keeping the temperature for 30min; gradually heating to 1200℃ within 400min and keeping the temperature for 120min.

[0082] The sintering aid in step F is a mixed powder of BN and Si3N4 in a weight ratio of 1.2:10.

[0083] The main crystal phase of Si3N4 in step A and the sintering aid is α-Si3N4>93%, D50<0.5μm, and the specific surface area is about 17±0.5m 2 / g, a loose bulk density of about 0.6±0.05 g / ml.

[0084] The sintering process in step F is: gradually increasing the sintering temperature to 1600℃ within 120 min and keeping for 60 min, then increasing the sintering temperature to 1800℃ within 90 min and keeping for 120 min.

[0085] Comparative Example 1

[0086] The difference between this example and Example 1 is that in the sintering process in step F, the pre-sintered blank is not buried in the sintering aid but is directly sintered in a nitrogen atmosphere, i.e., no sintering aid is used.

[0087] Comparative Example 2

[0088] The difference between this comparative example and Example 2 is that the organic binder used in step B of this comparative example is different from that of Example 2. The organic binder used in this comparative example is the binder described in paragraph 0027 of the patent application with the application number 201710861534.7, which includes the following components in mass percentage: PEG 40%-50%, PEO 20%-25%, HDPE 10%-15%, PMMA 13%-20%, and oleic acid 3%-5%.

[0089] The soaking time when the debinding rate of the once-debinding blank reaches 80% in step D is 37 h.

[0090] Comparative Example 3

[0091] The difference between this comparative example and Example 3 is that in step A of this comparative example: the composition of the SiAlON ceramic powder is different from that of Example 3. The SiAlON ceramic powder formula used in this comparative example is the SiAlON ceramic powder formula described in claim 2 of the patent application with the application number 202010454507.X, i.e., the SiAlON ceramic powder contains a combination of micro-nano silicon nitride powder, aluminum nitride powder, aluminum oxide powder, and sintering aid, and the mass percentage of the silicon nitride powder, aluminum nitride powder, and aluminum oxide powder is as follows: silicon nitride 67.14-72.37 wt.%, aluminum nitride 6.48-6.98 wt.%, and aluminum oxide 16.38-17.65 wt.%, and the mass percentage of each sintering aid in the sintering aid combination is as follows: yttrium oxide 1-9 wt.%, ytterbium oxide 0-0.5 wt.%, magnesium oxide 0-0.5-1 wt.%, silicon nitride magnesium 0-0.5 wt.%, and samarium oxide 0-1 wt.%.

[0092] Using the technical solutions described in Examples 1-3 and Comparative Examples 1-3, large-sized SiAlON ceramics of the same size were produced, ten batches of samples were produced for each technical solution, five samples were taken from each batch, and the following detection parameters were detected, and the average value of the detection results of each group of technical solutions was recorded in the following table.

[0093] Product size tolerance (%), surface finish (μm), density (g / cm 3 ), bending strength (MPa), hardness (HRA).

[0094]

[0095] The above examples are the preferred implementation of the present application, in addition to this, the present application can also be implemented in other ways, without departing from the concept of the present application, any obvious replacement within the protection scope of the present application.

Claims

1. An injection molding process for large SiAlON ceramics, characterized in that: It comprises the following steps: A. Ceramic powder configuration: Si3N4, AlN, Y2O3, La2O3 and Al2O3 are put into a ball milling device for ball milling treatment with anhydrous ethanol as medium. After ball milling, drying and sieving, SiAlON ceramic powder is obtained; B. Feed preparation: organic binder and SiAlON ceramic powder are added into a banbury mixer for fully melting and mixing. After cooling, small particle mixture is obtained through crushing treatment; C. Injection molding: small particle mixture is added into an injection molding machine for injection to obtain regular blank; D. Solvent debinding: regular blank is soaked in a dewaxing agent for solvent debinding treatment. After drying treatment, primary debinding blank is obtained; E. Thermal debinding and pre-sintering: primary debinding blank is put into a heating furnace for gradually increasing temperature and holding treatment. After furnace cooling, pre-sintering blank is obtained; F. Sintering: pre-sintering blank is buried in a sintering aid for sintering treatment in a nitrogen atmosphere to obtain regular-shaped SiAlON ceramic; In step A, the weight ratio of Si3N4, AlN, Y2O3, La2O3 and Al2O3 is: Si3N4 85-88 parts, AlN 1-4 parts, Y2O3 0.8-2 parts, La2O3 5-8 parts and Al2O3 0.2-1 part; The organic binder is mixed by the following raw materials in weight: PW organic binder 58-60 parts, PE organic binder 16-18 parts, PP organic binder 8-10 parts, EVA organic binder 5-8 parts and SA organic binder 3-5 parts; In step D, the dewaxing agent is a mixture of triethanolamine with a concentration of 90% and aviation kerosene with a purity of 99% in a volume ratio of 8-6:2-3. The soaking temperature is 50-55℃, and the soaking time is 25-30h.

2. A process for injection moulding of bulk SiAlON ceramics according to claim 1, characterized in that: In step B, the weight ratio of organic binder and SiAlON ceramic powder added is 18-20:80-82.

3. A process for injection moulding of bulk SiAlON ceramics according to claim 1, characterized in that: The working temperature of the banbury mixer is 180-190℃, and the mixing time is 1.5-2h.

4. A process for injection molding of large SiAlON ceramics according to claim 1, characterized in that: In step C, the working conditions of the injection molding machine are: nozzle temperature 180-190℃, pressure 80-120bar and speed 35-50%.

5. A process for injection moulding of bulk SiAlON ceramics according to claim 1, characterized in that: In step E, the gradually increasing temperature and holding treatment is: Increasing temperature: increasing to 100℃ within 400min; increasing to 200℃ within 360min and keeping the temperature for 60min; increasing to 250℃ within 200min and keeping the temperature for 120min; increasing to 360℃ within 300min and keeping the temperature for 30min; increasing to 650℃ within 420min and keeping the temperature for 30min; increasing to 1200℃ within 400min and keeping the temperature for 120min.

6. A process for injection molding of large SiAlON ceramics according to claim 1, characterized in that: In step F, the sintering aid is a mixed powder of BN and Si3N4 in a weight ratio of 0.8-1.2:8-10.

7. A process for injection molding of large SiAlON ceramics according to claim 1, characterized in that: In step F, the sintering treatment is: increasing the sintering temperature to 1600℃ within 120min and keeping the temperature for 60min, then increasing the sintering temperature to 1800℃ within 90min and keeping the temperature for 120min.

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