CN111041261A - Novel pressing and sintering method of particle reinforced molybdenum/tungsten-based composite material - Google Patents
Novel pressing and sintering method of particle reinforced molybdenum/tungsten-based composite material Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
- C22C1/05—Mixtures of metal powder with non-metallic powder
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/16—Both compacting and sintering in successive or repeated steps
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
- C22C27/04—Alloys based on tungsten or molybdenum
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
- C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
- B22F2998/10—Processes characterised by the sequence of their steps
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy
Abstract
The invention relates to a new pressing and sintering method of a particle reinforced molybdenum/tungsten-based composite material, belonging to the technical field of powder metallurgy. The novel pressing and sintering method adopts a twice pressing mode to obtain a pressing blank for the powder with the Fisher particle size not more than 2 mu m, and directly presses the powder with the Fisher particle size more than 2 mu m; and (3) firstly sintering the pressed blank by hydrogen, and then sintering in vacuum, wherein the hydrogen sintering adopts a mode of combining low-temperature sintering and high-temperature sintering. The pressing and sintering modes of the method can effectively deoxidize and improve the density. The mode of adopting twice suppression has effectively improved the suppression yield of fine powder, when carrying out the hydrogen sintering, adopts low temperature sintering in order fully to deoxidize, then carries out high temperature sintering again, when further improving the deoxidation degree, has effectively alleviated the obturator, and then guarantees when vacuum sintering, is favorable to the gas in the space to discharge, provides bigger sintering drive power for vacuum sintering for the sintering base has higher density.
Description
Technical Field
The invention relates to a new pressing and sintering method of a particle reinforced molybdenum/tungsten-based composite material, belonging to the technical field of powder metallurgy.
Background
Tungsten and its alloy, molybdenum and its alloy all have good high temperature strength and high temperature hardness, good thermal conductivity and electric conductivity, low coefficient of thermal expansion, excellent wearability and corrosion resistance, are used in fields such as space flight and aviation, energy electric power, microelectronics, biomedicine, machining, medical instrument, illumination, glass fibre, national defense construction extensively.
In particular, the existence of particle reinforced composite powder, i.e. particle reinforced molybdenum powder and particle reinforced tungsten powder, the particle reinforced phase makes molybdenum powder and tungsten powder have better performance, further widening the application field, wherein, the particle reinforced molybdenum powder is composed of molybdenum and oxide reinforced particles, the oxide particle dispersion reinforced molybdenum alloy can improve the performance of low temperature strength, plastic toughness, tensile strength, etc. of the molybdenum alloy, for example, Chinese patents CN107254594B, CN104328296A, CN104328301A, CN104294133A, etc. all disclose the preparation method of the particle reinforced molybdenum powder, the particle reinforced tungsten powder is composed of tungsten and oxide reinforced particles, the oxide particle dispersion reinforced tungsten alloy can improve the performance of tungsten alloy, such as high temperature performance, wear resistance, etc. for example, Chinese patents CN107008917B, CN105603235A, etc. disclose the preparation method of the particle reinforced tungsten powder, the particle reinforced phase in the particle reinforced molybdenum powder and the particle reinforced tungsten powder can be zirconium oxide, aluminum oxide, tungsten oxide, or tungsten, Oxides such as lanthanum oxide.
For the oxide-doped tungsten composite powder and the oxide-doped molybdenum composite powder, because the oxide has a strong function of preventing the growth of tungsten particles and molybdenum particles, generally, the particle sizes of the tungsten composite powder and the molybdenum composite powder after two-stage reduction are smaller, the Fisher particle size is mostly below 2 μm, even below 1 μm, and the tungsten composite powder and the molybdenum composite powder belong to superfine powder. The pressing of the particle-reinforced molybdenum superfine powder or the particle-reinforced tungsten superfine powder is a technological problem, and has the problems of large shrinkage, compaction failure, easy generation of cracks, fracture and even fragmentation and the like. In addition, the fine-particle reinforced molybdenum powder and the fine-particle reinforced tungsten powder have high oxygen content, and the traditional sintering method cannot effectively deoxidize and obtain a sintered blank with high density.
Disclosure of Invention
The invention aims to provide a novel pressing and sintering method of a particle-reinforced molybdenum/tungsten-based composite material, which can effectively deoxidize and improve the density of a sintered blank.
The technical scheme of the invention is as follows:
a new pressing and sintering method of particle reinforced molybdenum/tungsten-based composite material comprises the following steps:
(1) pressing
(a) For the particle reinforced composite powder with the Fisher size of not more than 2 mu m, a part of the particle reinforced composite powder with the formula amount is pressed into blocks, crushed and sieved to form coarse powder with the particle size larger than that of the particle reinforced composite powder, the coarse powder and the rest of the particle reinforced composite powder are mixed and then pressed to obtain a pressed blank;
(b) directly pressing the particle-reinforced composite powder with the Fisher size of more than 2 mu m to obtain a pressed blank;
the particle reinforced composite powder is particle reinforced molybdenum powder or particle reinforced tungsten powder; the particle reinforced molybdenum powder consists of molybdenum and oxide reinforced particles; the particle reinforced tungsten powder consists of tungsten and oxide reinforced particles;
(2) twice sintering
Sequentially performing hydrogen sintering and vacuum sintering on the pressed blank obtained in the step (1);
when the particle reinforced composite powder is particle reinforced molybdenum powder, the hydrogen sintering comprises the following steps: sintering at 1350-1450 deg.c for over 2 hr, and sintering at 1600-1700 deg.c for over 1 hr; the temperature of the vacuum sintering is 1850-1950 ℃;
when the particle reinforced composite powder is particle reinforced tungsten powder, the hydrogen sintering is as follows: sintering at 1550-1650 ℃ for more than 2h, and sintering at 2000-2100 ℃ for less than 1 h; the temperature of the vacuum sintering is 2200-2350 ℃.
In the novel pressing and sintering method of the particle reinforced molybdenum/tungsten-based composite material, the powder with the Fisher particle size of not more than 2 mu m is pressed twice to obtain a pressed blank, the powder with the Fisher particle size of more than 2 mu m is pressed once to obtain the pressed blank, and the pressed blank is sintered twice, namely hydrogen sintering and vacuum sintering are combined, so that the purposes of effectively deoxidizing and improving the density are achieved. When hydrogen sintering is carried out, low-temperature sintering is carried out for more than 2 hours to fully deoxidize, then high-temperature sintering within 1 hour is carried out, the closed pores are relieved while further deoxidizing, and then gas in gaps is discharged when vacuum sintering is guaranteed, a larger sintering driving force is provided for vacuum sintering, and a sintering blank has higher density. The invention combines two sintering processes, which can achieve better effect.
The method comprises the steps of firstly carrying out primary sintering by using hydrogen protection to achieve the purpose of full deoxidation, wherein the sintering temperature is lower than the normal sintering temperature, gaps in a sintering blank are not completely closed, then carrying out secondary vacuum sintering, wherein the vacuum environment is favorable for discharging gas in the gaps, providing larger sintering power for sintering and being favorable for obtaining higher relative sintering density.
In the hydrogen sintering process, high-purity hydrogen with the purity of 99.999 percent is introduced in the whole process for protection, so that the enough low oxygen content of a sintered blank is ensured.
The method has good application prospect and popularization value, the reinforcing phase of the particle reinforced molybdenum-based composite material is not specially limited, the particle reinforced molybdenum-based composite material is only the conventional oxide reinforced molybdenum-based composite material in the field, and the type of the oxide is not specially limited and can be alumina, zirconia, lanthanum oxide and the like. The reinforcing phase of the particle-reinforced tungsten-based composite material is not particularly limited, and any kind of oxide may be used, including alumina, zirconia, and lanthana, as long as it is an oxide-reinforced tungsten-based composite material that is conventional in the art. Preferably, in the step (1), the reinforcing particles of the particle-reinforced molybdenum powder are alumina and/or zirconia; the reinforced particles of the particle reinforced tungsten powder are alumina and/or zirconia. For example, the particle-reinforced molybdenum powder may be Al2O3p/Mo、ZrO2pthe/Mo, the particle reinforced tungsten powder can be Al2O3p/W、ZrO2p/W。
The sources of the particle-reinforced molybdenum-based composite material and the particle-reinforced tungsten-based composite material are not limited, and the particle-reinforced molybdenum-based composite material and the particle-reinforced tungsten-based composite material can be prepared by a conventional method in the field, for example, a liquid-liquid or solid-liquid doping method can be used for preparing tungsten (molybdenum) -based composite powder, such as tungsten (molybdenum) -based composite powder prepared by the preparation methods of the particle-reinforced molybdenum-based composite material and the particle-reinforced tungsten-based composite material disclosed in chinese patents CN107254594B, CN104328296A, CN104328301A, CN104294133A, CN107008917B, CN105603235A, and the like.
The content of the particulate reinforcing phase in the particulate-reinforced molybdenum-based composite material and the particulate-reinforced tungsten-based composite material is not limited, and the mass fraction of the particulate reinforcing phase in the composite material is generally not more than 10%, and for example, the mass fraction of the particulate reinforcing phase may be 0.2%, 1%, 2%, 5%, or the like.
Preferably, in the step (2), the low-temperature sintering time is 2-3 h; the high-temperature sintering time is 0.5-1 h.
Preferably, in the step (2), the vacuum sintering time is 1-3 h.
Preferably, in the step (2), the vacuum degree of the vacuum sintering is 10-2Pa or less.
It can be understood that the particle-reinforced composite powder with the Fisher size of more than 2.0 μm is particle-reinforced molybdenum powder or particle-reinforced tungsten powder, and a conventional pressing method is adopted to press the particle-reinforced composite powder to obtain a pressed blank, wherein the pressing pressure is 180-300 MPa, and the pressing time is 10-20 min.
However, most of the particle-reinforced molybdenum or tungsten powders have a Fisher size of less than 2 μm, especially Al prepared by liquid-liquid or solid-liquid doping2O3p/Mo、ZrO2p/Mo、Al2O3p/W、ZrO2pThe granular reinforced molybdenum powder or granular reinforced tungsten powder of/W and the like has small apparent density and large shrinkage during pressing, is easy to cause problems and is cut into two parts or broken into a plurality of parts. This is because of Al2O3Or ZrO2Such as oxide having high hardness, non-deformability and nano-scale Al, which is different from tungsten (molybdenum) in physical properties2O3Or ZrO2The powder is adsorbed around tungsten (molybdenum) particles, and plays a role in isolating the tungsten (molybdenum) particles, so that the bonding force between the particles is small after pressing, and the strength of the blank is too low; on the other hand, due to Al2O3Or ZrO2The introduction of (2) has the function of preventing tungsten (molybdenum) grains from growing, so that the particle-reinforced molybdenum powder or the particle-reinforced tungsten powder is usually smaller (the Fisher size is not more than 2.0 mu m and even less than 1.0 mu m and is far lower than the Fisher size of pure tungsten (or molybdenum) powder), the surface area is increased, the filling is difficult, and the shrinkage during pressing is larger. And the fine powder with the Fisher size of less than 2 mu m has poor flowability during pressing, poor internal filling uniformity and large pressing shrinkage, so the fine powder is easy to break, the size is not controllable, the specific surface area of the fine powder is large, the bridging is serious, great difficulty is brought to pressing, the breakage, the edge drop and the like are easy to occur,The problems of corner drop, small size, serious deformation and the like are solved, and the pressing yield is low and is generally only 60-80%. Therefore, in the present invention, for the particle-reinforced composite powder having a fisher's particle size of not more than 2 μm, a part of the particle-reinforced composite powder in the formulation amount is briquetted and crushed to form a coarse powder having a particle size larger than that of the particle-reinforced composite powder, and the coarse powder and the remaining part of the particle-reinforced composite powder are mixed and then pressed to obtain a compact.
The method divides the particle reinforced composite powder with the Fisher size of below 2 mu m into two parts, one part is used for briquetting, and the other part is directly mixed with coarse powder obtained by briquetting and crushing. The coarse powder with large particle size is mixed with the fine powder with small particle size in a particle grading mode, the fine powder with small particle size can be filled between the coarse powder with large particle size, the apparent density is further improved, meanwhile, the coarse powder with large particle size is subjected to briquetting, the apparent density of the particle reinforced composite powder with the particle size of less than 2 microns is effectively improved by the method through a two-time pressing mode, so that the pressed blank is smooth in surface, clear in edge angle, controllable in size, large in density, high in strength and free of defects such as cracks, fractures, layering and the like.
In the method, briquetting is to obtain coarse powder with large particle size, particles with uneven size are artificially formed, so that loose packing density is improved through particle size distribution, and briquetting can also improve the loose packing density of the obtained coarse powder with large particle size, therefore, the pressure of the briquetting can be lower than that of conventional pressing, and preferably, in the step (a), the pressure of the briquetting is 80-100 MPa; the briquetting time is 5-10 min.
It is understood that the crushing after briquetting can be carried out by conventional crushing means in the art (e.g., ball milling, using ceramic pots and ceramic balls), and preferably, in step (a), the sieving is carried out by a 40-60 mesh sieve.
In order to further increase the density of the pressed blank after pressing, preferably, in the step (a) and the step (b), the pressure of the pressing is 180-300 MPa; the pressing time is 10-20 min.
In order to further increase the apparent density of the mixture of the coarse powder obtained after briquetting and the remaining fine powder, it is preferable that the mass fraction of the particle-reinforced composite powder used for briquetting in step (a) be 70% to 80% in the total amount of the particle-reinforced composite powder. The method is characterized in that 70-80% of the total amount of the particle-reinforced composite powder is briquetted, and after the particle-reinforced composite powder is crushed into coarse powder with large particle size, the coarse powder is mixed with the rest 20-30% of the particle-reinforced composite powder through particle grading, so that the loose packing density is improved, the surface of a pressed blank is smooth, the edges and corners are clear, the size is controllable, the density is high, the strength is high, and the defects of cracks, fracture, delamination and the like are avoided.
Preferably, in step (a), after mixing, the method further comprises: and annealing the mixed powder under the protection of hydrogen at the temperature of 850-950 ℃, and then pressing to obtain a pressed blank. Annealing under hydrogen protection helps to eliminate work hardening, restore the deformability of tungsten (molybdenum), and further reduce the oxygen content.
It can be understood that the annealing time can be 2-3 h. And cooling along with the furnace temperature after annealing.
Detailed Description
The present invention will be further described with reference to the following embodiments.
The specific embodiment of the novel pressing and sintering method of the particle reinforced molybdenum/tungsten-based composite material is as follows:
example 1
Al in this example2O3The sintering method of the particle reinforced molybdenum-based composite material comprises the following steps:
(1) raw materials
1.43kg of alumina reinforced molybdenum powder, wherein Al in the alumina reinforced molybdenum powder2O3The mass fraction of the aluminum oxide reinforced molybdenum powder is 2 percent, and the Fisher-size of the aluminum oxide reinforced molybdenum powder is 1.2 mu m.
(2) Briquetting and annealing
Taking 1.0kg of alumina reinforced molybdenum powder, filling the alumina reinforced molybdenum powder into a mold (compacting and filling), placing the mold in a cold isostatic press, maintaining the pressure for 5 minutes under the pressing pressure of 100MPa, forming, crushing, sieving by a 60-mesh sieve, uniformly mixing with the rest 0.43kg of alumina reinforced molybdenum powder, annealing under the protection of hydrogen, wherein the annealing temperature is 950 ℃, the annealing time is 1 hour, and cooling along with the furnace temperature for later use.
(3) Pressing
And (3) completely filling 1.43kg of the powder annealed in the step (2) into a die, placing the die into a cold isostatic press, and keeping the pressure for 10 minutes under the pressing pressure of 300MPa to press the powder into blocks to obtain pressed blanks.
(4) Hydrogen sintering and vacuum sintering
Taking the pressed blank obtained in the step (3), and sintering for two times, wherein the first sintering is sintering under the protection of hydrogen, heating to 1350 ℃, preserving heat for 3 hours, heating to 1600 ℃, preserving heat for 1 hour, and cooling along with a furnace; the second sintering is carried out under vacuum (vacuum degree is not higher than 10)-2Pa), heating to 1850 ℃, preserving heat for 3 hours, and cooling along with the furnace to obtain the product.
The relative density of the sample after the above two pressing and two sintering was 97.8%, while that of the comparative sample after only one sintering (1850 ℃ C.. times.3 h, hydrogen gas) was 95.9%.
Example 2
ZrO in this example2The sintering method of the particle reinforced molybdenum-based composite material comprises the following steps:
(1) raw materials
1.375kg of zirconia-reinforced molybdenum powder, wherein ZrO in the zirconia-reinforced molybdenum powder2The mass fraction of (a) is 1.0%, and the Fisher-size of the zirconia-reinforced molybdenum powder is 1.6 μm.
(2) Briquetting and annealing
1.1kg of zirconia reinforced molybdenum powder is taken and put into a mould (compacted and filled), then the mould is placed in a cold isostatic press, the pressure is maintained for 10 minutes under the pressing pressure of 80MPa for forming, the mould is crushed, the crushed material is sieved by a 40-mesh sieve, the crushed material is uniformly mixed with the rest 0.275kg of zirconia reinforced molybdenum powder, then the annealing treatment is carried out under the protection of hydrogen, the annealing temperature is 900 ℃, the annealing time is 2 hours, and the mixture is cooled along with the furnace temperature for standby.
(3) Pressing
And (3) completely filling 1.375kg of the powder annealed in the step (2) into a mould, placing the mould into a cold isostatic press, and keeping the pressure for 20 minutes under 230MPa of pressing pressure to press the powder into blocks to obtain pressed blanks.
(4) Hydrogen sintering and vacuum sintering
Taking the pressed blank obtained in the step (3), sintering for two times, wherein the first sintering is sintering under the protection of hydrogen, heating to 1450 ℃, preserving heat for 2 hours, heating to 1700 ℃, preserving heat for 0.5 hour, and cooling along with the furnace; the second sintering is carried out under vacuum (vacuum degree is not higher than 10)-2Pa), heating to 1950 ℃, preserving the heat for 1 hour, and cooling along with the furnace to obtain the product.
The relative density of the sample after the above-mentioned two pressing and two sintering was 98.1%, while that of the comparative sample after only one sintering (1950. degreeC.. times.1 h, hydrogen gas) was 96.5%.
Example 3
Al in this example2O3The sintering method of the particle reinforced tungsten-based composite material comprises the following steps:
(1) raw materials
2.57kg of aluminum oxide reinforced tungsten powder, wherein Al in the aluminum oxide reinforced tungsten powder2O3The mass fraction of the aluminum oxide reinforced tungsten powder is 0.2 percent, and the Fisher size of the aluminum oxide reinforced tungsten powder is 1.8 mu m.
(2) Briquetting and annealing
2.0kg of alumina reinforced tungsten powder is taken and put into a mould (compacted and filled), then the mould is placed in a cold isostatic press, the mould is formed under the pressure of 90MPa and the pressure is maintained for 8 minutes, the crushed tungsten powder is crushed and sieved by a 40-mesh sieve, the crushed tungsten powder and the rest 0.57kg of alumina reinforced tungsten powder are uniformly mixed, then annealing treatment is carried out under the protection of hydrogen, the annealing temperature is 880 ℃, the annealing time is 2.5 hours, and the tungsten powder is cooled for standby along with the furnace temperature.
(3) Pressing
And (3) completely filling 2.57kg of the powder annealed in the step (2) into a die, placing the die into a cold isostatic press, and keeping the pressure for 20 minutes under the pressing pressure of 200MPa to press the powder into blocks to obtain pressed blanks.
(4) Hydrogen sintering and vacuum sintering
Taking the pressed blank obtained in the step (3), sintering for two times, wherein the first sintering is sintering under the protection of hydrogen, heating to 1550 ℃, preserving heat for 3 hours, heating to 2000 ℃, preserving heat for 0.5 hour, and cooling along with a furnace; the second sintering is carried out under vacuum (vacuum degree is not higher than 10)-2Pa), heating to 2200 ℃, preserving heat for 3 hours, and cooling along with the furnace to obtain the product.
The relative density of the sample after the above two pressing and two sintering was 97.1%, while that of the comparative sample after only one sintering (2200 ℃ C.. times.3 h, hydrogen gas) was 95.8%.
Example 4
ZrO in this example2The sintering method of the particle reinforced tungsten-based composite material comprises the following steps:
(1) raw materials
2.5kg of zirconium oxide reinforced tungsten powder, wherein ZrO in the zirconium oxide reinforced tungsten powder2The mass fraction of the powder is 0.5 percent, and the Fisher size of the zirconia reinforced tungsten powder is 1.5 mu m.
(2) Briquetting and annealing
2.0kg of zirconium oxide reinforced tungsten powder is taken and put into a mould (compacted and filled), then the mould is placed in a cold isostatic press, the pressure is maintained for 8 minutes under the pressing pressure of 90MPa for forming, the tungsten powder is crushed and sieved by a 40-mesh sieve, the crushed tungsten powder and the rest 0.5kg of zirconium oxide reinforced tungsten powder are uniformly mixed, then annealing treatment is carried out under the protection of hydrogen, the annealing temperature is 850 ℃, the annealing time is 2 hours, and the tungsten powder is cooled for standby along with the furnace temperature.
(3) Pressing
And (3) completely filling 2.5kg of the powder annealed in the step (2) into a die, placing the die into a cold isostatic press, and keeping the pressure for 15 minutes under the pressing pressure of 180MPa to press the powder into blocks to obtain pressed blanks.
(4) Hydrogen sintering and vacuum sintering
Taking the pressed blank obtained in the step (3), and sintering for two times, wherein the first sintering is sintering under the protection of hydrogen, heating to 1650 ℃, preserving heat for 2 hours, heating to 2100 ℃, preserving heat for 1 hour, and cooling along with the furnace; the second sintering is carried out under vacuum (vacuum degree is not higher than 10)-2Pa), heating to 2350 deg.C, maintaining for 1 hr, and furnace cooling.
The relative density of the sample after the above two pressing and two sintering was 97.2%, while that of the comparative sample after only one sintering (2350 ℃ C.. times.1 h, hydrogen gas) was 96.1%.
For the particle reinforced molybdenum powder or particle reinforced tungsten powder with the Fisher particle size of more than 2.0 mu m, the powder is pressed for 10-20 min under the pressure of 180-300 MPa. The procedure of hydrogen sintering and vacuum sintering was the same as in example 1.
If only pressing is carried out on the particle reinforced molybdenum powder or the particle reinforced tungsten powder with the Fisher particle size of less than 2.0 mu m, the particle reinforced molybdenum powder or the particle reinforced tungsten powder with the particle size of less than 2.0 mu m is directly pressed for 10-20 min under the pressure of 180-300 MPa, the finished product rate of pressing is only 60% -80%, and the problems of breakage, edge drop, corner drop, small size, serious deformation and the like are easy to occur. And the twice pressing of the embodiment 1-4 is adopted, so that the pressing yield can reach more than 98%. The problems of easy fracture, edge drop, corner drop, small size, serious deformation and the like are caused by large specific surface area of fine powder with the Fisher size of less than 2.0 mu m, serious bridging and great difficulty in pressing.
The above description is only a preferred embodiment of the present invention, and not intended to limit the present invention, and the scope of the present invention is defined by the appended claims, and all changes that come within the meaning and range of equivalency of the specification are therefore intended to be embraced therein.
Claims (10)
1. A novel pressing and sintering method of a particle reinforced molybdenum/tungsten-based composite material is characterized by comprising the following steps:
(1) pressing
(a) For the particle reinforced composite powder with the Fisher size of not more than 2 mu m, a part of the particle reinforced composite powder with the formula amount is pressed into blocks, crushed and sieved to form coarse powder with the particle size larger than that of the particle reinforced composite powder, the coarse powder and the rest of the particle reinforced composite powder are mixed and then pressed to obtain a pressed blank;
(b) directly pressing the particle-reinforced composite powder with the Fisher size of more than 2 mu m to obtain a pressed blank;
the particle reinforced composite powder is particle reinforced molybdenum powder or particle reinforced tungsten powder; the particle reinforced molybdenum powder consists of molybdenum and oxide reinforced particles; the particle reinforced tungsten powder consists of tungsten and oxide reinforced particles;
(2) twice sintering
Sequentially performing hydrogen sintering and vacuum sintering on the pressed blank obtained in the step (1);
when the particle reinforced composite powder is particle reinforced molybdenum powder, the hydrogen sintering comprises the following steps: sintering at 1350-1450 deg.c for over 2 hr, and sintering at 1600-1700 deg.c for over 1 hr; the temperature of the vacuum sintering is 1850-1950 ℃;
when the particle reinforced composite powder is particle reinforced tungsten powder, the hydrogen sintering is as follows: sintering at 1550-1650 ℃ for more than 2h, and sintering at 2000-2100 ℃ for less than 1 h; the temperature of the vacuum sintering is 2200-2350 ℃.
2. The new pressing and sintering method as claimed in claim 1, wherein in the step (a), the pressure of the pressed block is 80-100 MPa; the briquetting time is 5-10 min.
3. The new pressing and sintering method according to claim 1, wherein in the step (a) and the step (b), the pressing pressure is 180-300 MPa; the pressing time is 10-20 min.
4. The novel pressing and sintering method as claimed in claim 1, wherein in the step (a), the mass fraction of the particle-reinforced composite powder used for the briquetting is 70-80% of the total mass of the particle-reinforced composite powder.
5. The new pressing and sintering method as claimed in claim 1, wherein in the step (a), the sieving is 40-60 mesh sieving.
6. The new pressing and sintering method of claim 1, wherein step (a) further comprises, after mixing: and annealing the mixed powder under the protection of hydrogen at the temperature of 850-950 ℃, and then pressing to obtain a pressed blank.
7. The new pressing and sintering method according to any one of claims 1 to 6, wherein in the step (1), the reinforcing particles of the particle-reinforced molybdenum powder are alumina and/or zirconia; the reinforced particles of the particle reinforced tungsten powder are alumina and/or zirconia.
8. The new pressing and sintering method as claimed in any one of claims 1 to 6, wherein in the step (2), the time of the low-temperature sintering is 2 to 3 hours; the high-temperature sintering time is 0.5-1 h.
9. The new pressing and sintering method as claimed in any one of claims 1 to 6, wherein in the step (2), the vacuum sintering time is 1 to 3 hours.
10. The new pressing and sintering method as claimed in any one of claims 1 to 6, wherein in the step (2), the vacuum degree of the vacuum sintering is 10-2Pa or less.
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| CN113909480A (en) * | 2020-07-08 | 2022-01-11 | 核工业西南物理研究院 | Preparation method of in-situ nano zirconium oxide particle dispersion reinforced tungsten alloy |
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