CN101353735A - A method for preparing composite nanoparticle strengthened and toughened sintered molybdenum material - Google Patents

Abstract

The invention discloses a method for preparing a composite nano particle strengthened and toughened sintered molybdenum material. It is characterized in that the strengthening and toughening phase of the molybdenum material is La ₂ O ₃ /Mo ₅ Si ₃ composite nanoparticles, in which Mo ₅ Si ₃ is added in the form of nano-MoSi ₂ , and the in-situ reaction of MoSi ₂ and Mo at high temperature is used Mo ₅ Si ₃ is generated, and La ₂ O ₃ is added in the form of La ₂ O ₃ nanoparticles. The preparation method involved in the present invention is to organically combine the low-temperature toughening of rare earth oxides and the high-temperature strengthening of pentamolybdenum trisilicide to play a dual role of toughening and strengthening, and can effectively improve the high-temperature resistance and low-temperature toughness of molybdenum materials .

Description

A method for preparing composite nanoparticle strengthened and toughened sintered molybdenum material

technical field

The invention belongs to the technical field of metallurgy, and relates to a method for preparing a composite nanoparticle toughened sintered molybdenum material, in particular to a composite nanoparticle toughened sintered molybdenum material for preparing a copper alloy extrusion die with high thermal conductivity and low expansion The method of preparation of the material.

Background technique

As a powder metallurgy material used in the field of high temperature engineering, sintered molybdenum has the characteristics of high melting point, moderate density, good thermal conductivity, low thermal expansion coefficient, and excellent corrosion resistance. In addition to boats and backing plates for ceramics and rare earth magnets, they can also be used as crucibles, orifices and electrodes for glass melting, heat shields for high-temperature furnaces, plugs for perforated stainless steel pipes, nozzles for rocket launchers, and steel die-casting molds And copper alloy extrusion dies, etc. With the continuous development of modern industry and science and technology, the application field of sintered molybdenum is also expanding, and people's performance requirements have exceeded the performance requirements of existing or traditional uses in many aspects, such as extrusion temperature When the white copper tube is extruded at about 1200°C, the ordinary extruded die steel will soften and deform quickly at this temperature, and the ceramic material is embedded in the die steel as the mold core, and there are conditions of rapid cooling and rapid heating. The material is easy to crack and the sizing belt collapses. Sintered molybdenum is used as the tool and mold. It is required that the molybdenum not only has good high-temperature strength and low-temperature toughness, but also has high thermal conductivity, thermal stability and low thermal expansion coefficient to truly realize sintering. Structure and function integration of molybdenum materials. However, at present, sintered molybdenum generally has disadvantages such as poor high temperature resistance and brittleness, low quantity and low quality, incomplete varieties, low processing yield, shortage of many special-shaped special products, and high cost.

For high-performance molybdenum materials, carbide-strengthened molybdenum alloys (such as TZM, Mo-0.5Ti, MHC and ZHC), solid-solution-carbide-strengthened molybdenum alloys (such as M ₂₅ WH ₁ , M ₂₅ WH ₂ and M ₂₅ WZH ₃ ), rare earth oxide reinforced molybdenum alloy (doped with La ₂ O ₃ , Sm ₂ O ₃ , Nd ₂ O ₃ , Tb ₂ O _{3 ,} etc.), rare earth oxide-carbide comprehensive strengthening type Molybdenum alloys and high-temperature molybdenum (doped with Si, Al, K and other elements), and have successfully applied TZM, ZHC, MHC and other molybdenum alloys to the extrusion tool and die industry. Higher heat strength.

Publication patent 200610162008.3 provides a preparation method of strengthened molybdenum alloy, which involves using TiC as a strengthening phase for molybdenum alloys of copper and its alloys, ferrous metal die-casting molds, inserts and extrusion dies. Publication patent 200610165737.4 provides a The method for preparing molybdenum-lanthanum alloys involves rare earth modified molybdenum alloys. European patent EP080618A1 provides a method for preparing semi-finished and finished products of molybdenum alloys containing intermetallic compounds. The intermetallic compounds are preferably molybdenum silicide and molybdenum silicon boride , can also be molybdenum boride.

None of the above-mentioned patents relates to a preparation method for preparing a composite nanoparticle toughened sintered molybdenum material for a copper alloy extrusion die with high thermal conductivity and low expansion.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing composite nanoparticle toughened sintered molybdenum material. Compared with the previous sintered molybdenum material, the prepared material maintains high thermal conductivity and low expansion. , its high temperature resistance and low temperature toughness are effectively improved.

A method for preparing composite nanoparticles toughened sintered molybdenum material, characterized in that: comprising the following steps:

1) Preparation of molybdenum powder

_MoO2 powder with a purity of 99.8-99.9% is reduced under a protective atmosphere at 950-1100°C to obtain molybdenum powder;

2) Preparation of _MoSi2 powder

The molybdenum powder and silicon powder prepared in step 1) are fully mixed according to the atomic ratio Mo:Si=1:(2～2.1), and ball milled to prepare MoSi ₂ powder;

3) Preparation of La ₂ O ₃ /MoSi ₂ composite nanopowder

Fully mix MoSi ₂ and La ₂ O ₃ powders with a mass ratio of 1-1:1.5, and ball mill to prepare La ₂ O ₃ /MoSi ₂ composite particles with a particle size of 60-80nm;

4) Preparation of La ₂ O ₃ /Mo ₅ Si ₃ Composite Nanoparticles Strengthened and Toughened Sintered Molybdenum Materials

Add the La ₂ O ₃ /MoSi ₂ composite nano-powder to the Mo powder and mix thoroughly, the La ₂ O ₃ /MoSi ₂ composite nano-particle is 0.2% to 2.0% of the mass of Mo; press the resulting mixed powder to obtain a Φ15-55mm The bar material is sintered at a temperature of 1800-1900° C. to prepare a La ₂ O ₃ /Mo ₅ Si ₃ composite nanoparticle strengthened and toughened sintered molybdenum material.

The protective gas in the step 1) is hydrogen, and the flow rate is 25-35 dm ³ ·min ^-1 .

The silicon powder in the step 2) has a purity of 99.8-99.9% and a particle size of 0-48 μm.

The ball grinding process in the step 2) is: put the mixed powder into the ball mill tank, the ball mill medium is stainless steel balls, the specifications of the stainless steel balls are Φ20mm and Φ10mm, and the ratio is 1: (2～2.5), the stainless steel balls and the powder The weight ratio of the ball mill is (20-30): 1; before the ball milling, the ball mill tank is evacuated first, and then argon gas is introduced to ensure that the ball mill process is always carried out under the protection of argon gas, and the ball mill tank is sealed with an O-ring; It is carried out in a type ball mill, the speed is 250-400r/min, and the ball milling time is 20-30 hours.

The ball grinding process in the step 3) is: put the mixed powder in the ball mill tank, the ball mill medium is stainless steel balls, the specifications of the stainless steel balls are Φ20mm and Φ10mm, and the ratio is 1: (2～2.5), the stainless steel balls and the powder The weight ratio is (20-30): 1, the ball milling is carried out in a planetary ball mill, the ball milling time is 25-35 hours, and the rotating speed is 350-400r/min.

The pressing process in the step 4) is as follows: the mixed powder is evenly loaded into a rubber mold, and pressed on a cold isostatic press, the pressing pressure is 180-300 MPa, the boosting time is 22-24 minutes, and the holding time is 7 ～9min, the depressurization time is 2～4min, and the bar material of Φ15～55mm is obtained.

In the step 4), the whole sintering period is protected by hydrogen to prevent the blank from being oxidized.

The beneficial effects that the present invention has have:

The La ₂ O ₃ /Mo ₅ Si ₃ composite nanoparticle strengthened and toughened sintered molybdenum material involved in the present invention is an organic combination of low-temperature toughening of rare earth oxides and high-temperature strengthening of pentamolybdenum trisilicide to play a toughening and reinforcing role. The dual function of molybdenum can effectively improve the high temperature resistance and low temperature toughness of molybdenum materials. Compared with the previous sintered molybdenum material, the material prepared by the present invention can effectively improve its high temperature resistance and low temperature toughness while maintaining high thermal conductivity and low expansion. The comprehensive performance data of the material can be seen in Examples 2-6 . It overcomes the shortcomings of existing sintered molybdenum materials, such as poor high temperature resistance and brittleness, small quantity and low quality, low processing yield, shortage of many special-shaped special products, and high cost.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Embodiment 1: The preparation method of composite nanoparticle toughened sintered molybdenum material mainly includes:

1) Preparation of molybdenum powder

The MoO ₂ powder with a purity of 99.9% is reduced under the protection of hydrogen at 950-1100°C, the reduction time is 90-120min, and the hydrogen flow rate is 30dm ³ ·min ^-1 .

2) Preparation of _MoSi2 powder

The molybdenum powder prepared in step 1) and the silicon powder with a purity of 99.9% and a particle size of less than 48 μm are fully mixed according to the atomic ratio Mo:Si=1:2, and then the mixed powder is put into a stainless steel tank for ball milling. The medium is stainless steel balls, the specifications of stainless steel balls are Φ20mm and Φ10mm, the ratio is 1:2, and the weight ratio of stainless steel balls to powder is 20:1. Before ball milling, vacuumize the ball mill tank first, and then pass in a certain pressure of argon gas to ensure that the ball mill process is always carried out under the protection of argon gas. The ball mill tank is sealed with an O-ring. Ball milling was carried out in a planetary ball mill at a speed of 390 r/min, and MoSi ₂ powder was prepared after ball milling for 24 hours.

3) Preparation of La ₂ O ₃ /MoSi ₂ composite nanopowder

Fully mix the MoSi ₂ and La ₂ O ₃ (analytical pure) powders with a mass ratio of 1:1, then put the mixed powder into the planetary ball mill for 30 hours according to the conditions of step 2), and the stainless steel ball and the powder The weight ratio is 20:1, the rotation speed is 390r/min, and La ₂ O ₃ /MoSi ₂ composite particles with a particle size of 60-80nm are prepared.

4) Preparation of La ₂ O ₃ /Mo ₅ Si ₃ Composite Nanoparticles Strengthened and Toughened Sintered Molybdenum Materials

The La ₂ O ₃ /MoSi ₂ composite nano-powder prepared in step 3) is added to the Mo powder, and the La ₂ O ₃ /MoSi ₂ composite nano-particle is 0.2%-2.0% of the mass of Mo. The mixed powders were thoroughly mixed for 10 hours under normal pressure with a cone mixer. The mixed powder is evenly put into the rubber mold, and pressed on a cold isostatic press with a pressing pressure of 200MPa, a pressurization time of 22-24min, a holding time of 7-9min, and a depressurization time of 2-4min. Obtain a Φ17mm bar. The pressed bar is sintered in an intermediate frequency furnace, the sintering temperature is 1840 ° C, and the temperature is kept for 5 to 8 hours to prepare the La ₂ O ₃ /Mo ₅ Si ₃ composite nanoparticle toughened sintered molybdenum material. During the whole sintering period, pass Protected with hydrogen to prevent the blank from being oxidized.

Example 2

According to the step 1 described in "Example 2", molybdenum powder is prepared, and the ball-to-material ratio in step 2) is determined as 20: 1, and the rotating speed is determined as 390r/min, and _MoSi2 powder is prepared, according to step 3) To prepare _La2O3 / _MoSi2 composite nanoparticles, set _{the La2O3} / _MoSi2 composite nanoparticles in step 4) to be 0.5% of the mass of Mo, _and keep it warm for ₇ hours to prepare _La2O3 /MoSi2 The comprehensive performance data of ₅ Si ₃ composite nanoparticles strengthened and toughened sintered molybdenum materials are shown in Table 1.

Table 1 present embodiment material performance data

Example 3

According to the step 1 described in "Example 2", molybdenum powder is prepared, and the ball-to-material ratio in step 2) is determined as 20: 1, and the rotating speed is determined as 390r/min, and _MoSi2 powder is prepared, according to step 3) To prepare _La2O3 / _MoSi2 composite nanoparticles, set the _La2O3 / _MoSi2 composite nanoparticles in step 4) _{to 0.5} % of the mass of Mo, and keep it warm for ₅ hours to prepare _La2O3 /MoSi2 The comprehensive performance data of ₅ Si ₃ composite nanoparticles strengthened and toughened sintered molybdenum materials are shown in Table 2.

Table 2 present embodiment material performance data

Example 4

According to the step 1 described in "Example 2", molybdenum powder is prepared, and the ball-to-material ratio in step 2) is determined as 20: 1, and the rotating speed is determined as 390r/min, and _MoSi2 powder is prepared, according to step 3) To prepare _La2O3 / _MoSi2 composite nanoparticles, set _{the La2O3} / _MoSi2 composite nanoparticles in step 4) to be 1.0% of the mass of Mo, _and keep it warm for ₇ hours to prepare _La2O3 /MoSi2 The comprehensive performance data of the sintered molybdenum materials strengthened and toughened by ₅ Si ₃ composite nanoparticles are shown in Table 3.

Table 3 present embodiment material performance data

Example 5

According to the step 1 described in "Example 2", molybdenum powder is prepared, and the ball-to-material ratio in step 2) is determined as 30: 1, and the rotating speed is determined as 390r/min, and _MoSi2 powder is prepared, according to step 3) La ₂ O ₃ /MoSi ₂ composite nanoparticles were prepared, and the La ₂ O ₃ /MoSi ₂ composite nanoparticles in step 4) were 0.5% of the mass of Mo, and kept for 7 hours to prepare La ₂ O ₃ /Mo ₅ The comprehensive performance data of Si ₃ composite nanoparticle strengthened and toughened sintered molybdenum materials are shown in Table 4.

Table 4 present embodiment material performance data

Example 6

Prepare molybdenum powder according to step 1) described in "Summary of the Invention", set the ball-to-material ratio in step 2) as 20:1, and the rotating speed as 270r/min, prepare _MoSi2 powder, and prepare according to step 3) La ₂ O ₃ /MoSi ₂ composite nanoparticles were obtained, and the La ₂ O ₃ /MoSi ₂ composite nanoparticles in step 4) were set at 0.5% of the mass of Mo, and kept for 7 hours to prepare La ₂ O ₃ /Mo ₅ The comprehensive performance data of Si ₃ composite nanoparticles strengthened and toughened sintered molybdenum materials are shown in Table 5.

Table 5 present embodiment material performance data

Claims (7)

1. A method for preparing composite nanoparticles toughened sintered molybdenum material, characterized in that: comprising the following steps: 1) Preparation of molybdenum powder _MoO2 powder with a purity of 99.8-99.9% is reduced under a protective atmosphere at 950-1100°C to obtain molybdenum powder; 2) Preparation of _MoSi2 powder The molybdenum powder and silicon powder prepared in step 1) are fully mixed according to the atomic ratio Mo:Si=1:(2～2.1), and ball milled to prepare MoSi ₂ powder; 3) Preparation of La ₂ O ₃ /MoSi ₂ composite nanopowder Fully mix MoSi ₂ and La ₂ O ₃ powders with a mass ratio of 1-1:1.5, and ball mill to prepare La ₂ O ₃ /MoSi ₂ composite particles with a particle size of 60-80nm; 4) Preparation of La ₂ O ₃ /Mo ₅ Si ₃ Composite Nanoparticles Strengthened and Toughened Sintered Molybdenum Materials Add the La ₂ O ₃ /MoSi ₂ composite nano-powder to the Mo powder and mix thoroughly, the La ₂ O ₃ /MoSi ₂ composite nano-particle is 0.2% to 2.0% of the mass of Mo; press the resulting mixed powder to obtain a Φ15-55mm The bar material is sintered at a temperature of 1800-1900° C. to prepare a La ₂ O ₃ /Mo ₅ Si ₃ composite nanoparticle strengthened and toughened sintered molybdenum material. 2. The method for preparing composite nanoparticle strengthened and toughened sintered molybdenum material according to claim 1, characterized in that: the protective gas in the step 1) is hydrogen, and the flow rate is 25-35 dm ³ ·min ^-1 . 3. The method for preparing composite nanoparticle strengthened and toughened sintered molybdenum material according to claim 1, characterized in that the silicon powder in step 2) has a purity of 99.8-99.9% and a particle size of 0-48 μm. 4. the method for preparing composite nanoparticle strengthening and toughening sintered molybdenum material as claimed in claim 1, is characterized in that: the ball milling process in described step 2) is: mixed powder is put into ball mill pot, and ball mill medium is Stainless steel balls, the specifications of stainless steel balls are Φ20mm and Φ10mm, the ratio is 1:(2~2.5), the weight ratio of stainless steel balls to powder is (20~30):1; Argon gas is used to ensure that the ball milling process is always carried out under the protection of argon gas, and the ball milling tank is sealed with an O-ring; the ball milling is carried out in a planetary ball mill with a speed of 250-400r/min and a ball milling time of 20-30 hours. 5. the method for preparing composite nanoparticle strengthening and toughening sintered molybdenum material as claimed in claim 1, is characterized in that: the ball milling process in described step 3) is: mixed powder is put into ball mill tank, and ball mill medium is Stainless steel balls, stainless steel ball specifications are Φ20mm and Φ10mm, the ratio is 1: (2~2.5), the weight ratio of stainless steel balls to powder is (20~30):1, the ball milling is carried out in a planetary ball mill, and the ball milling time is 25~ 35 hours, the speed is 350~400r/min. 6. the method for preparing composite nanoparticle strengthening and toughening sintered molybdenum material as claimed in claim 1, is characterized in that: the pressing process in described step 4) is: the mixing powder is evenly packed in the rubber mold, in cold etc. Pressing on a static press, the pressing pressure is 180-300MPa, the pressurization time is 22-24min, the pressure-holding time is 7-9min, and the depressurization time is 2-4min, to obtain a bar of Φ15-55mm. 7. The method for preparing composite nanoparticle toughened sintered molybdenum material as claimed in any one of claims 1 to 6, characterized in that: in the step 4), the whole sintering period is protected by hydrogen to prevent the blank from being oxidation.