CN107974603B - A kind of resistance to high temperature oxidation two-phase composite tungsten material and preparation method thereof - Google Patents

Abstract

The invention discloses a high-temperature oxidation-resistant dual-phase tungsten composite material and a preparation method thereof, wherein the alloy dual-phase components doped by the high-temperature oxidation-resistant dual-phase tungsten composite material are WSi ₂ and W _0.67 Cr _0.33 , wherein each component is according to The atomic percent composition is: WSi ₂ 0.5-1.5%, W _0.67 Cr _0.33 98.5-99.5%. WSi ₂ alloy powder and W _0.67 Cr _0.33 (W‑12wt.%Cr) alloy powder prepared by self-propagation were mixed in proportion, and alloy samples were prepared by spark plasma sintering. Under the synergistic effect of the two phases, not only the high-temperature oxidation resistance of the tungsten-based alloy is significantly improved, but also the mechanical properties of the tungsten-based composite material at high temperatures are significantly improved.

Description

A high-temperature oxidation-resistant dual-phase tungsten composite material and its preparation method

technical field

The invention relates to a metal composite material and a preparation method thereof, in particular to a high-temperature oxidation-resistant dual-phase tungsten composite material and a preparation method thereof.

Background technique

Controlled thermonuclear fusion energy is an ideal energy source for the future of human society, and is considered to be one of the main ways to effectively solve the future energy needs of human beings. Tungsten has the characteristics of high melting point, high thermal conductivity, minimal adsorption of deuterium and tritium, low radioactivity, no reaction with H, and strong anti-sputtering ability. From the current research, tungsten is considered to be the most promising PFMs ( Plasma Facing Materials). However, in the event of a fusion reactor coolant failure accident, air will enter the vacuum reactor, and PFMs will withstand an instantaneous temperature of 1200 °C. In practical applications, the synergistic effect of oxygen and water vapor in humid air makes tungsten materials oxidize rapidly. In order to develop self-passivating smart tungsten alloys, researchers at home and abroad have improved the oxidation resistance of tungsten by doping Cr elements. W-Cr binary alloy forms dense oxide layer Cr ₂ O ₃ , but the Cr ₂ O ₃ oxide layer is difficult to maintain stability and long-term passivation after long-term exposure to high temperature oxidizing environment. Therefore, activating elements are added to the W-Cr binary alloy system to improve the oxidation resistance of the alloy.

At present, studies have reported that the most active elements doped with W-Cr alloys are mainly Ti, Y, and Si elements. The common method at home and abroad is to add W, Cr, and the third element in the form of simple substances. Sintering was carried out after H2 (80 hours). However, the traditional mechanical alloying process has many disadvantages, such as serious energy consumption; low output is not enough to meet the actual production application requirements; incomplete mechanical alloying; the introduction of impurities and so on. However, the use of WSi ₂ doped W-Cr alloy has not been reported. WSi ₂ doped W-Cr dual-phase alloy can significantly improve the oxidation resistance and high-temperature mechanical properties of W alloy.

SUMMARY OF THE INVENTION

The present invention aims to provide a high-temperature oxidation-resistant dual-phase tungsten composite material and its preparation method. The technical problem to be solved is to improve the high-temperature oxidation resistance of W-Cr binary alloy materials through the screening of doping elements and the optimization of the preparation process. Performance and anti-water mist high temperature oxidation performance.

In the high-temperature oxidation-resistant dual-phase tungsten composite material of the present invention, the doped alloy dual-phase components are WSi ₂ and W _0.67 Cr _0.33 , wherein each component is constituted by atomic percentage: WSi ₂ 0.5-1.5%, W _0.67 Cr _0.33 98.5-99.5%.

The preparation method of the high-temperature oxidation-resistant dual-phase tungsten composite material of the present invention comprises the following steps:

Step 1: Mix the Powder

WSi ₂ alloy powder and W _0.67 Cr _0.33 alloy powder (converted into mass ratio chemical formula W-12wt.%Cr) were stirred in a powder mixer at 400 rpm for 2 hours and mixed evenly to obtain a dual-phase composite powder; the original powder The particle sizes were: WSi ₂ average particle size 4.0 microns, W _0.67 Cr _0.33 average particle size 5.2 microns.

In step 1, fill the mixing tank with one-third of the volume of powder, set the speed of the mixer to 400r/min, and set the time to 2h.

Step 2: Sintering

Put the two-phase composite powder obtained in step 1 into a graphite mold, then put the mold into a spark plasma sintering furnace, evacuate the sintering furnace at room temperature, raise the temperature to 1450°C for 1 minute after 8.5 minutes, and keep the furnace cavity during the sintering process The vacuum degree is 2-8Pa, the pressure is controlled not to exceed 50MPa during sintering, and after the heat preservation is completed, it is lowered to room temperature, and the (WSi ₂ ) _x (W _0.67 Cr _0.33 ) _y dual-phase tungsten alloy composite material is obtained. Cr and Si elements exist in the tungsten-based alloy in the form of compounds. On the one hand, it prevents the oxidation of Cr and Si elements during the preparation process; .

During the sintering process, the heating rate was 100°C/min, and the cooling rate was 100°C/min.

The beneficial effects of the present invention are reflected in:

WSi ₂ is a metal compound with a tetragonal crystal structure, and W _0.67 Cr _0.33 is an infinite substitution solid solution with a body-centered cubic structure. Compared with the traditional mechanical alloying method, the direct mixing of WSi ₂ and W _0.67 Cr _0.33 alloy powder has the following advantages: First, by adding alloy powder, it replaces the traditional mechanical alloying process, saves energy and greatly increases the output Secondly, it is beneficial to weaken the activity of Cr and Si elements to prevent the material preparation process from being oxidized, so that the activated elements Cr and Si exist in the form of solid solution and compound in the sintered sample; finally, the subsurface WSi ₂ and W in the oxidation process The W-Si-O and W-Cr-O oxides formed by oxidation of _0.67 Cr _0.33 significantly reduce the thermal stress and growth stress between the oxide layer Cr ₂ O ₃ and the W substrate, and improve the bonding ability of the oxide layer and the substrate. Therefore, the high-temperature oxidation resistance of the tungsten-based composite material can be improved. Compared with W-Cr-Si ternary alloy, which is more researched at present, the direct doping of WSi ₂ effectively stabilizes the Cr ₂ O ₃ oxide layer and reduces the generation of tungsten-rich phase. The WO ₃ formed in the tungsten-rich phase during the oxidation process has serious damage to the oxidation resistance of the material. Moreover, when an accident occurs in a nuclear fusion reactor, there will be an extreme situation of 1200°C high temperature, water mist, and oxygen coexisting. At this time, Cr ₂ O ₃ will volatilize into CrO ₃ , and the protective layer will break and fail. The glass phase SiO ₂ with self-healing function can still exist stably in the environment of 1200 ° C, and can reduce the diffusion of OH ^- ions in the water mist in the protective layer. And under the synergistic effect of WSi ₂ and W _0.67 Cr _0.33 , the high temperature oxidation resistance of tungsten-based materials is significantly improved. After 15 hours of oxidation, the weight gain rate is only 1/8-1/10 of pure tungsten materials.

Description of drawings

Figure 1 is the micromorphological image of (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 alloy in sintered state. Figure 1a is the surface morphology, and Figure 1b is the fracture morphology.

Figure 2 is the cross-sectional image _of the oxide layer of W _0.67 Cr _0.33 and (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 alloy after oxidation for 10 minutes _{. 2} ) Cross-sectional morphology of oxide layer of _0.01 (W _0.67 Cr _0.33 ) _0.99 alloy.

Figure 3 is the oxidation kinetics curve for 15 hours of oxidation.

Figure 4 is the image of alloy morphology after oxidation for 15 hours. Figure 4a is pure tungsten, Figure 4b is W _0.67 Cr _0.33 , and Figure 4c is (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 .

Detailed ways

The technical solutions of the present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

Example 1:

In this example, the high-temperature oxidation-resistant (WSi ₂ ) _0.005 (W _0.67 Cr _0.33 ) _0.995 dual-phase tungsten alloy composite material, the doped alloy dual-phase components are WSi ₂ and W _0.67 Cr _0.33 , where each component is atomically The percentage composition is: WSi ₂ 0.5%, W _0.67 Cr _0.33 99.5%.

In this example, the preparation method of the high-temperature oxidation-resistant (WSi ₂ ) _0.005 (W _0.67 Cr _0.33 ) _0.995 dual-phase tungsten alloy composite material is as follows:

1. Powder making: Mix the WSi ₂ and W _0.67 Cr _0.33 alloy powder in a 400 rpm mixer for 2 hours to obtain a two-phase composite powder; the particle size of the original powder is: the average particle size of WSi ₂ The average particle size of W _0.67 Cr _0.33 is 5.2 microns.

2. Sintering: Put the two-phase composite powder into the graphite mold, then put the mold into the discharge plasma sintering furnace, vacuum the sintering furnace at room temperature, raise the temperature to 1450°C for 1 minute after 8.5 minutes, and keep the furnace during the sintering process The vacuum degree of the cavity is 2Pa, and the pressure is controlled not to exceed 50MPa during sintering. After the heat preservation is completed, it is lowered to room temperature, and the (WSi ₂ ) _0.005 (W _0.67 Cr _0.33 ) _0.995 dual-phase tungsten alloy composite material is obtained.

During the sintering process, the heating rate was 100°C/min, and the cooling rate was 100°C/min.

The second phase of the sintered composite material is evenly distributed, the oxide layer is relatively dense during the oxidation process, and has high high temperature oxidation resistance. After 15 hours of oxidation, the weight gain rate is only 1/10 of the pure tungsten material.

Example 2:

In this example, the high-temperature oxidation-resistant (WSi ₂ ) _0.015 (W _0.67 Cr _0.33 ) _0.985 dual-phase tungsten alloy composite material, the doped alloy dual-phase components are WSi ₂ and W _0.67 Cr _0.33 , where each component is atomically The percentage composition is: WSi ₂ 1.5%, W _0.67 Cr _0.33 98.5%.

In this example, the preparation method of the high-temperature oxidation-resistant (WSi ₂ ) _0.015 (W _0.67 Cr _0.33 ) _0.985 dual-phase tungsten alloy composite material is as follows:

1. Powder making: Mix WSi ₂ and a certain proportion of W _0.67 Cr _0.33 alloy powder in a powder mixer at 400 rpm for 2 hours to obtain a two-phase composite powder; the particle size of the original powder is: the average particle size of WSi ₂ is 4.0 microns, W _0.67 Cr _0.33 average particle size 5.2 microns.

2. Sintering: Put the two-phase composite powder into the graphite mold, then put the mold into the discharge plasma sintering furnace, evacuate the sintering furnace at room temperature, raise the temperature to 1450°C for 1 minute after 8.5 minutes, and keep the furnace cavity during the sintering process The vacuum degree is 5Pa, and the pressure is controlled not to exceed 50MPa during sintering. After the heat preservation is completed, it is lowered to room temperature, and the (WSi ₂ ) _0.015 (W _0.67 Cr _0.33 ) _0.985 dual-phase tungsten alloy composite material is obtained.

During the sintering process, the heating rate was 100°C/min, and the cooling rate was 100°C/min.

The second phase of the sintered composite material is evenly distributed, the oxide layer is relatively dense during the oxidation process, and has high high temperature oxidation resistance. After 15 hours of oxidation, the weight gain rate is only 1/8 of the pure tungsten material.

Example 3:

In this example, the high-temperature oxidation-resistant (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 dual-phase tungsten alloy composite material, the doped alloy dual-phase components are WSi ₂ and W _0.67 Cr _0.33 , where each component is atomically The percentage composition is: WSi ₂ 1%, W _0.67 Cr _0.33 99%.

In this example, the preparation method of the high-temperature oxidation-resistant (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 dual-phase tungsten alloy composite material is as follows:

1. Powder making: Mix WSi ₂ and a certain proportion of W _0.67 Cr _0.33 alloy powder in a powder mixer at 400 rpm for 2 hours to obtain a two-phase composite powder; the particle size of the original powder is: the average particle size of WSi ₂ is 4.0 microns, W _0.67 Cr _0.33 average particle size 5.2 microns.

2. Sintering: Put the two-phase composite powder into the graphite mold, then put the mold into the discharge plasma sintering furnace, vacuum the sintering furnace at room temperature, raise the temperature to 1450°C for 1 minute after 8.5 minutes, and keep the furnace during the sintering process The vacuum degree of the cavity is 8Pa, and the pressure is controlled not to exceed 50MPa during sintering. After the heat preservation is completed, it is lowered to room temperature, and the (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 dual-phase tungsten alloy composite material is obtained.

During the sintering process, the heating rate was 100°C/min, and the cooling rate was 100°C/min.

The morphology of the composite material after sintering is shown in Figure 1. The second phase is evenly distributed. From the microscopic appearance, the material has less voids and is relatively dense. Commercial tungsten, W _0.67 Cr _0.33 (self-propagating) alloy, (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 duplex tungsten alloy was subjected to cyclic oxidation experiments at 1000°C for 15 hours. Oxidizing atmosphere: 20vol.% O ₂ , 80vol.% N ₂ . In order to analyze the oxidation mechanism, after 10 minutes of oxidation, observe the oxide layer interface of the sample as shown in Figure 2, the oxide layer thickness of W _0.67 Cr _0.33 (self-propagating) alloy is about 2.6 μm, and (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) The thickness of the oxide layer of _0.99 duplex tungsten alloy is about 1.8 μm, and the oxide layer is relatively dense. The oxidation kinetics curve after oxidizing for 15 hours is shown in Figure 3, (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 dual-phase tungsten alloy has excellent high-temperature oxidation resistance, and its weight gain after oxidation for 15 hours is lower than that of W _0.67 Cr _0.33 alloy. Much lower than commercially pure tungsten. Figure 4 is an image of the alloy morphology after oxidation for 15 hours. Pure tungsten is completely oxidized to yellow tungsten (WO ₃ ), and the scale of (WSi ₂ ) _0.01 (W _0.67 Cr _0.33 ) _0.99 duplex tungsten alloy is more dense than that of W _0.67 Cr _0.33 alloy. For dense. The second phase of the sintered composite material is evenly distributed, the oxide layer is relatively dense during the oxidation process, and has high high temperature oxidation resistance. After 15 hours of oxidation, the weight gain rate is only 1/9 of the pure tungsten material.

Claims (7)

1. a kind of resistance to high temperature oxidation two-phase composite tungsten material, it is characterised in that: its alloy double phase component adulterated is WSi₂With W_0.67Cr_0.33, wherein each component is constituted by atomic percent are as follows: WSi₂0.5-1.5%, W_0.67Cr_0.3398.5-99.5%.

2. a kind of preparation method of resistance to high temperature oxidation two-phase composite tungsten material described in claim 1, it is characterised in that including such as Lower step:

Step 1: mixed powder

By WSi₂Alloyed powder and W_0.67Cr_0.33Alloyed powder is added in mixing tank and is uniformly mixed, and obtains two-phase composite powder；

Step 2: sintering

The two-phase composite powder that step 1 is obtained is packed into graphite jig, then mold is put into discharge plasma sintering furnace, room temperature Under to sintering stove evacuation, be warming up to 1450 DEG C keep the temperature 1 minute, in sintering process keep furnace chamber vacuum degree, carry out vacuum-sintering, Room temperature is down to after heat preservation to get (WSi is arrived₂)_x(W_0.67Cr_0.33)_yTwo-phase tungsten composites.

3. preparation method according to claim 2, it is characterised in that:

In step 1, Particle Sizes are as follows: WSi₂Particle mean size is 4.0 microns, W_0.67Cr_0.33Particle mean size is 5.2 micron.

4. preparation method according to claim 2, it is characterised in that:

In step 1, the powder of one third volume, mixing tank revolving speed 400r/min, mixing time 2h are loaded in mixing tank.

5. preparation method according to claim 2, it is characterised in that:

Pressure, which is controlled, in step 2, in sintering process is no more than 50MPa.

6. preparation method according to claim 2, it is characterised in that:

In step 2, in sintering process, heating rate is 100 DEG C/min, and rate of temperature fall is 100 DEG C/min.

7. preparation method according to claim 2, it is characterised in that:

It is 2-8Pa that furnace chamber vacuum degree is kept in step 2, in sintering process.