CN111421144B

CN111421144B - Water corrosion resistant refractory metal molybdenum surface treatment method

Info

Publication number: CN111421144B
Application number: CN202010231696.4A
Authority: CN
Inventors: 丁向东; 万徳才让; 薛德祯; 马胜强; 孙院军; 杨贺杰; 曾毅
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2020-03-27
Filing date: 2020-03-27
Publication date: 2021-11-19
Anticipated expiration: 2040-03-27
Also published as: CN111421144A

Abstract

The invention discloses a method for treating a refractory metal molybdenum surface resistant to water corrosion, which comprises the steps of preparing molybdenum powder, press forming, sintering, hot working and heat treatment, preparing an experimental sample and ion irradiation, wherein the vacuum degree in a sample irradiation cavity is kept, Ar ions are adopted to irradiate the surface of the sample at a set temperature, and the dosage is selected to be 3-4 x10¹⁶ion/cm²The acceleration voltage is 350-400KeV, and the average atomic potential energy is 25-35eV, so as to obtain the molybdenum block after surface treatment. And evaluating the corrosion resistance of the sample before and after irradiation through electrochemical open-circuit potential, polarization curve, impedance and other tests. The refractory metal molybdenum treated by the method has good corrosion resistance, and the failure life of the molybdenum in an aqueous medium is greatly prolonged. By researching and analyzing the influence of neutron irradiation effect on corrosion, scientific data are provided for the application of molybdenum and the alloy thereof in the nuclear power field.

Description

Water corrosion resistant refractory metal molybdenum surface treatment method

Technical Field

The invention relates to a method for treating a water corrosion resistant alloy surface, in particular to a method for treating a water corrosion resistant refractory metal molybdenum surface.

Background

Molybdenum is one of rare metals with important strategic significance of a new generation, has the advantages of high melting point of 2625 ℃, excellent high-temperature strength, electric and thermal conductivity, high-temperature creep resistance, low thermal expansion coefficient and the like, and is good in corrosion resistance to liquid metal lead bismuth and the like, so that the molybdenum is widely applied to various fields of metallurgy, petroleum, chemical industry, machinery, aerospace, steel industry, nuclear energy technology and the like. With the continuous popularization of the application field of molybdenum and molybdenum alloy, the molybdenum and molybdenum alloy are widely applied to special environments such as high temperature, high pressure, strong corrosion and the like, and the service environments put higher requirements on the comprehensive performance of the molybdenum alloy. Taking a common pressurized water reactor as an example, in addition to a large amount of heat released by uranium dioxide fuel, neutrons released by U atoms in the fission process generate high radiation flux and heat at a reactor core, and the temperature of water in a pressure vessel is about 325 ℃ and the pressure is 15.5 MPa. Molybdenum, as one of the important cladding material candidates, is subjected to both high temperatures, high pressures, and synergistic effects of irradiation and corrosion within the reactor.

At present, a great deal of research finds that molybdenum has poor corrosion resistance in water environment and generates MoO at normal temperature₃But this oxide film does not protect the substrate well to mitigate the reaction rate. Some researches show that molybdenum is easily oxidized, corroded along crystals and other phenomena in high-temperature water after 400 ℃, and is corroded at high speed in a volatile mode. There are two general ways of protecting materials against corrosion, namely alloying and coating. Both of these approaches have their own drawbacks: alloying causes the problem of reduction of inherent mechanical and physical properties of the material, and the coating causes the bad phenomena of insufficient interface bonding strength and the like. How to avoid the defects caused by the two traditional protective measures and well improve the corrosion resistance of the material is a scientific problem to be urgently solved.

Disclosure of Invention

In order to solve the defects in the prior art, the invention aims to provide a method for treating the surface of refractory metal molybdenum resistant to water corrosion, wherein the surface of an experimental sample is irradiated by Ar ions, so that the electrochemical corrosion resistance is obviously improved. The technology does not introduce other elements into the molybdenum matrix to influence the inherent good mechanical properties of the matrix, avoids the problems of poor interface effect or bonding strength and the like caused by the traditional coating, and changes the electrochemical corrosion behavior by changing the organization behaviors of the crystal structure and the like of the surface nano layer.

The invention is realized by the following technical scheme.

The invention provides a water corrosion resistant refractory metal molybdenum surface treatment method, which comprises the following steps:

1) preparation of molybdenum powder

Roasting molybdenite to obtain molybdenum trioxide mixed with impurities, and dissolving, separating and purifying the molybdenum trioxide mixture by adopting an ammonia water solution to obtain an ammonium molybdate solution; decomposing the ammonium molybdate solution at a certain temperature to obtain molybdenum trioxide, and reducing the molybdenum trioxide in an ammonia atmosphere to obtain pure molybdenum powder;

2) press forming and sintering

Carrying out single-shaft cold pressing forming on the pure molybdenum powder to obtain a pressed plate, and carrying out pressureless sintering on a pressed plate blank at a sintering temperature in a hydrogen atmosphere;

3) hot working and heat treatment

Carrying out hot rolling on a molybdenum plate, preserving heat in a hydrogen atmosphere, then carrying out multi-pass double-roller rolling in the air to obtain a plate, and then carrying out annealing treatment;

4) preparation of the test samples

Cutting a molybdenum plate sample, finely grinding and polishing by using polishing paste, slightly etching the polished surface by using an aqueous solution containing potassium ferricyanide and sodium hydroxide, and cleaning residual corrosive by using water;

5) ion irradiation

Maintaining the vacuum degree in the sample irradiation cavity, irradiating the sample surface with Ar ion at set temperature, and selecting dosage of 3-4 x10¹⁶ion/cm²I.e. dose rate of 9 x10¹⁶ion/cm²And the acceleration voltage is 350-400KeV, and the average atomic potential energy is 25-35eV, so that the molybdenum block after surface treatment is obtained.

With respect to the above technical solutions, the present invention has a further preferable solution:

optionally, in step 3), impurities in the molybdenum plate are: la is less than or equal to 0.0009, Mg is less than or equal to 0.0002, Fe is less than or equal to 0.0023, Cr is less than or equal to 0.0008, and Al is less than or equal to 0.0006.

Optionally, in the step 1), the ammonium molybdate solution is decomposed at a temperature of 450 ℃ to 500 ℃.

Optionally, in the step 2), pressureless sintering is carried out for 6h at the sintering temperature of 1960 DEG C

Optionally, in the step 3), hot rolling is performed at 1350 ℃, heat preservation is performed in a hydrogen atmosphere for 10min, the stress relief annealing temperature is 850-1100 ℃, and the heat preservation time is 40-60 min.

Optionally, in the step 4), the Mo slice is finely ground by using 240#, 400#, 800#, 1200# and 2000# water sandpaper, respectively, and polished by using polishing paste with a particle diameter of 0.5-1.5 μm.

Optionally, in the step 5), the angle between the ion incidence direction and the sample surface is 97 °.

Optionally, in the step 5), the filament voltage 8V and the filament current 110A in the ion source are maintained.

Optionally, in the step 5), the vacuum degree in the sample irradiation cavity is kept to be 1-3 x10^-7torr, temperature 25-100 ℃.

The water corrosion resistant refractory metal molybdenum surface treatment method has the following beneficial effects:

1. the molybdenum plate after surface treatment by the ion irradiation technology avoids the defects brought by the traditional alloying, namely the defects that the original mechanical and physical properties of the material are not influenced, and the water corrosion resistance of the molybdenum plate is also well improved;

2. by the surface modification technology of ion irradiation, the phenomena of poor interface effect and binding force, easy falling and the like caused by the coating are avoided;

3. the influence of Ar ion irradiation on the water corrosion resistance of molybdenum is well evaluated while neutron irradiation is simulated through Ar ions;

4. the density of the oxide film generated in the aqueous medium is increased by the ion irradiation surface treatment technology, so that the oxide film has a certain positive effect on the protection of a matrix and the alleviation of corrosion.

According to the intrinsic advantages of ion irradiation, namely, the irradiation layer is only hundreds of nanometers and the uniformity is good and the like, on the basis of not changing the inherent performance of the Mo material, the Mo material with the water corrosion resistance improved after the surface treatment is obtained by irradiating the 300nm layer on the Mo surface through Ar ions. The invention well makes up the problems caused by the traditional alloying, namely adding elements to influence the inherent mechanical and physical properties of the substrate, limiting the utilization of the material in certain specific environments, and avoiding the problems of interface effect caused by two materials brought by the coating, such as the falling phenomenon caused by different thermal expansion coefficients or poor binding force, innovatively provides the technical means of ion irradiation, irradiates a layer of Ar ions on the surface of Mo, changes the original crystal structure, such as non-crystallization, and improves the water corrosion resistance of the material. In addition, neutron irradiation can be simulated through Ar irradiation, the influence of the neutron irradiation effect on corrosion is well researched and analyzed, and scientific data is provided for the application of molybdenum and molybdenum alloy in the field of nuclear power.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention:

FIG. 1 shows the concentration and damage distribution of Ar ions in Mo;

FIG. 2 is a microhardness variation test chart of Mo before and after Ar ion irradiation;

FIG. 3 is the open circuit potential of Mo in 3.5% NaCl solution before and after Ar ion irradiation;

FIG. 4 is a plot of Mo in 3.5% NaCl solution before and after irradiation with Ar ions;

FIG. 5 is an impedance spectrum of Mo in 3.5% NaCl solution before and after Ar ion irradiation;

FIGS. 6a and 6b are the interface morphology graphs obtained after the electrochemical corrosion of the unirradiated Mo;

FIG. 7 is an interface morphology diagram obtained after electrochemical corrosion of Mo irradiated by Ar ions.

Detailed Description

The present invention will now be described in detail with reference to the drawings and specific embodiments, wherein the exemplary embodiments and descriptions of the present invention are provided to explain the present invention without limiting the invention thereto.

The invention relates to a water corrosion resistant refractory metal molybdenum surface treatment method, which comprises the following steps:

(1) preparation of molybdenum powder

First, molybdenite (MoS) is roasted₂) Obtaining molybdenum trioxide mixed with impurities, and dissolving, separating and purifying the mixture containing molybdenum trioxide by adopting an ammonia water solution to finally obtain an ammonium molybdate solution. Decomposing the ammonium molybdate solution at 450-500 ℃, and volatilizing ammonia and water in the reaction process to obtain molybdenum trioxide. Finally, molybdenum trioxide is reduced twice in ammonia atmosphere to obtain pure molybdenum powder; the detailed reaction equation is as follows:

MoS₂+O₂→MoO₃+SO₂ (1)

MoO₃+NH₄OH→(NH₄)₆Mo₇O₂₄ (2)

(NH₄)₆Mo₇O₂₄→MoO₃+H₂O (3)

MoO₂+2H₂＝Mo+2H₂O (4)

(2) press forming and sintering

And carrying out single-shaft cold pressing forming on the molybdenum powder to obtain a pressed plate. And carrying out pressureless sintering on the pressed blank in a hydrogen atmosphere. Wherein the sintering temperature is 1960 ℃, and the heat preservation time is 6 h.

(3) Hot working and heat treatment

And (3) carrying out hot rolling on the molybdenum plate, wherein the rolling temperature is 1350 ℃, keeping the temperature for 10min in a hydrogen atmosphere, carrying out double-roller rolling in the air, and carrying out rolling to obtain the final plate with the thickness of 3 mm. The annealing temperature is 850-1100 ℃ and the heat preservation time is 40-60 min.

(4) Hot working and heat treatment

The molybdenum plate was cut into square samples of 10x10x3mm by a wire cutting machine, the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200 and No. 2000 sandpaper, respectively, to obtain a flat surface, and polished with a polishing paste having a particle diameter of 0.5 to 1.5. mu.m. In order to eliminate the surface stress and deformation layer introduced in the polishing process and compare the grain boundary before and after irradiation, the polished surface is slightly etched by using an aqueous solution containing 8-12% of potassium ferricyanide and sodium hydroxide, and finally, the polished surface is cleaned by water to remove the residual corrosive agent on the surface.

(5) Ion irradiation

Ar ions are adopted to irradiate the surface of a sample, and the vacuum degree in an irradiation cavity of the sample is 1-3 x10^-7torr, keeping the temperature at 25-100 deg.C, selecting the dose at 3-4 x10¹⁶ion/cm²The acceleration voltage is 350-400KeV, the average atomic potential energy is 25-35eV, Ar ion irradiation is carried out on the surface of the prepared sample, the filament voltage of 8V and the filament current of 110A in the ion source are kept in the process, and the sample is taken out after the irradiation is finished to prepare the molybdenum sample after the surface treatment.

Specific examples are given below to further illustrate the present invention.

Example 1

Roasting molybdenite (MoS)₂) Molybdenum trioxide mixed with impurities is obtained, and the ammonium molybdate solution is obtained by dissolving, separating and purifying the mixture of the ammonia water solution and the molybdenum trioxide. Decomposing the ammonium molybdate solution at 500 ℃ to obtain molybdenum trioxide, and reducing twice in an ammonia atmosphere to obtain pure molybdenum powder. And carrying out single-shaft cold pressing on the pure molybdenum powder to obtain a pressed plate. And pressureless sintering the pressed blank in a hydrogen atmosphere at the sintering temperature of 1960 ℃, and keeping the temperature for 6 hours. Rolling a molybdenum plate at 1350 ℃, keeping the temperature for 10min in a hydrogen atmosphere, performing double-roller rolling in air, and performing double-roller rolling to obtain a final plate with the thickness of 3mm, wherein the specific impurity concentration of the prepared molybdenum plate is shown in table 1. And carrying out heat treatment at the annealing temperature of 1100 ℃ for 40 min. The molybdenum plate was cut into 10 × 3mm square samples by a wire cutting machine, the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200, No. 2000 sandpaper, and polished with a polishing paste having a particle diameter of 0.5 μm. Watch after polishingSlightly etching the surface by using an aqueous solution containing 10 percent of potassium ferricyanide and sodium hydroxide, and cleaning the surface residues by using water; irradiating the sample surface with Ar ions at a dose of 3 x10¹⁶ion/cm²The accelerating voltage is 350KeV, the average atomic potential energy is 30eV, the filament voltage in the ion source is 8V, the filament current is 110A, and the vacuum degree in the sample irradiation cavity is 3 x10^-7torr, temperature 60 ℃ to obtain a molybdenum sample.

Example 2

Roasting molybdenite (MoS)₂) Molybdenum trioxide mixed with impurities is obtained, and the ammonium molybdate solution is obtained by dissolving, separating and purifying the mixture of the ammonia water solution and the molybdenum trioxide. Decomposing the ammonium molybdate solution at 450 ℃ to obtain molybdenum trioxide, and reducing twice in an ammonia atmosphere to obtain pure molybdenum powder. And carrying out single-shaft cold pressing on the pure molybdenum powder to obtain a pressed plate. And pressureless sintering the pressed blank in a hydrogen atmosphere at the sintering temperature of 1960 ℃, and keeping the temperature for 6 hours. Rolling a molybdenum plate at 1350 ℃, keeping the temperature for 10min in a hydrogen atmosphere, performing double-roller rolling in air, and performing double-roller rolling to obtain a final plate with the thickness of 3mm, wherein the specific impurity concentration of the prepared molybdenum plate is shown in table 1. Heat treatment is carried out at the annealing temperature of 1000 ℃ for 50 min. The molybdenum plate was cut into 10 × 3mm square samples by a wire cutting machine, the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200, No. 2000 sandpaper, and polished with a polishing paste having a particle diameter of 0.8 μm. Slightly etching the polished surface by using an aqueous solution containing 9 percent of potassium ferricyanide and sodium hydroxide, and cleaning the surface residue by using water; irradiating the sample surface with Ar ions at a dose of 4 x10¹⁶ion/cm²The accelerating voltage is 360KeV, the average atomic potential energy is 35eV, the voltage of a filament in the ion source is 8V, the current of the filament is 110A, and the vacuum degree in the sample irradiation cavity is 2 x10^-7torr, temperature 90 ℃ to obtain a molybdenum sample.

Example 3

Roasting molybdenite (MoS)₂) Molybdenum trioxide mixed with impurities is obtained, and the ammonium molybdate solution is obtained by dissolving, separating and purifying the mixture of the ammonia water solution and the molybdenum trioxide. Decomposing the ammonium molybdate solution at 460 ℃ to obtain molybdenum trioxide, and reducing twice in an ammonia atmosphere to obtain pure molybdenum powder. Single-shaft cold pressing pure molybdenum powderThe pressed plate is obtained. And pressureless sintering the pressed blank in a hydrogen atmosphere at the sintering temperature of 1960 ℃, and keeping the temperature for 6 hours. Rolling a molybdenum plate at 1350 ℃, keeping the temperature for 10min in a hydrogen atmosphere, performing double-roller rolling in air, and performing double-roller rolling to obtain a final plate with the thickness of 3mm, wherein the specific impurity concentration of the prepared molybdenum plate is shown in table 1. And carrying out heat treatment at the annealing temperature of 850 ℃ for 60 min. The molybdenum plate was cut into 10x10x3mm square samples by a wire cutter, and the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200, No. 2000 sandpaper and polished with a polishing paste having a particle diameter of 1.0. mu.m. Slightly etching the polished surface by using an aqueous solution containing 8 percent of potassium ferricyanide and sodium hydroxide, and cleaning the surface residue by using water; irradiating the sample surface with Ar ions at a dose of 3 x10¹⁶ion/cm²The accelerating voltage is 400KeV, the average atomic potential energy is 25eV, the filament voltage in the ion source is 8V, the filament current is 110A, and the vacuum degree in the sample irradiation cavity is 3 x10^-7torr, temperature 60 ℃ to obtain a molybdenum sample.

Example 4

Roasting molybdenite (MoS)₂) Molybdenum trioxide mixed with impurities is obtained, and the ammonium molybdate solution is obtained by dissolving, separating and purifying the mixture of the ammonia water solution and the molybdenum trioxide. Decomposing the ammonium molybdate solution at 470 ℃ to obtain molybdenum trioxide, and reducing twice in an ammonia atmosphere to obtain pure molybdenum powder. And carrying out single-shaft cold pressing on the pure molybdenum powder to obtain a pressed plate. And pressureless sintering the pressed blank in a hydrogen atmosphere at the sintering temperature of 1960 ℃, and keeping the temperature for 6 hours. Rolling a molybdenum plate at 1350 ℃, keeping the temperature for 10min in a hydrogen atmosphere, performing double-roller rolling in air, and performing double-roller rolling to obtain a final plate with the thickness of 3mm, wherein the specific impurity concentration of the prepared molybdenum plate is shown in table 1. And carrying out heat treatment at the annealing temperature of 900 ℃ for 55 min. The molybdenum plate was cut into 10 × 3mm square samples by a wire cutting machine, the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200, No. 2000 sandpaper, and polished with a polishing paste having a particle diameter of 1.5 μm. Slightly etching the polished surface by using an aqueous solution containing 9 percent of potassium ferricyanide and sodium hydroxide, and cleaning the surface residue by using water; irradiating the sample surface with Ar ions at a dose of 3 x10¹⁶ion/cm²The acceleration voltage was set to 370KeV,the average atomic potential energy is 32eV, the filament voltage in the ion source is 8V, the filament current is 110A, and the vacuum degree in the sample irradiation cavity is 3 x10^-7torr, temperature 100 ℃ to obtain a molybdenum sample.

Example 5

Roasting molybdenite (MoS)₂) Molybdenum trioxide mixed with impurities is obtained, and the ammonium molybdate solution is obtained by dissolving, separating and purifying the mixture of the ammonia water solution and the molybdenum trioxide. Decomposing the ammonium molybdate solution at 480 ℃ to obtain molybdenum trioxide, and reducing twice in an ammonia atmosphere to obtain pure molybdenum powder. And carrying out single-shaft cold pressing on the pure molybdenum powder to obtain a pressed plate. And pressureless sintering the pressed blank in a hydrogen atmosphere at the sintering temperature of 1960 ℃, and keeping the temperature for 6 hours. Rolling a molybdenum plate at 1350 ℃, keeping the temperature for 10min in a hydrogen atmosphere, performing double-roller rolling in air, and performing double-roller rolling to obtain a final plate with the thickness of 3mm, wherein the specific impurity concentration of the prepared molybdenum plate is shown in table 1. Heat treatment is carried out for 40min at the annealing temperature of 950 ℃. The molybdenum plate was cut into 10 × 3mm square samples by a wire cutting machine, the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200, No. 2000 sandpaper, and polished with a polishing paste having a particle diameter of 1.2 μm. Slightly etching the polished surface by using an aqueous solution containing 12 percent of potassium ferricyanide and sodium hydroxide, and cleaning the surface residue by using water; irradiating the sample surface with Ar ions at a dose of 4 x10¹⁶ion/cm²The accelerating voltage is 350KeV, the average atomic potential energy is 30eV, the filament voltage in the ion source is 8V, the filament current is 110A, and the vacuum degree in the sample irradiation cavity is 3 x10^-7torr, temperature 25 ℃ to obtain a molybdenum sample.

Example 6

Roasting molybdenite (MoS)₂) Molybdenum trioxide mixed with impurities is obtained, and the ammonium molybdate solution is obtained by dissolving, separating and purifying the mixture of the ammonia water solution and the molybdenum trioxide. Decomposing the ammonium molybdate solution at 490 ℃ to obtain molybdenum trioxide, and reducing twice in an ammonia atmosphere to obtain pure molybdenum powder. And carrying out single-shaft cold pressing on the pure molybdenum powder to obtain a pressed plate. And pressureless sintering the pressed blank in a hydrogen atmosphere at the sintering temperature of 1960 ℃, and keeping the temperature for 6 hours. Rolling molybdenum plate at 1350 deg.C, maintaining the temperature in hydrogen atmosphere for 10min, rolling in air by two rollersThe final plate thickness obtained by rolling was 3mm, and the specific impurity concentrations in the obtained molybdenum plate were as shown in table 1. And carrying out heat treatment at the annealing temperature of 1100 ℃ for 45 min. The molybdenum plate was cut into 10 × 3mm square samples by a wire cutting machine, the Mo chips were finely ground with No. 240, No. 400, No. 800, No. 1200, No. 2000 sandpaper, and polished with a polishing paste having a particle diameter of 0.7 μm. Slightly etching the polished surface by using a 10% potassium ferricyanide and sodium hydroxide aqueous solution, and cleaning the surface residue by using water; irradiating the sample surface with Ar ions at a dose of 3 x10¹⁶ion/cm²The accelerating voltage is 400KeV, the average atomic potential energy is 28eV, the filament voltage in the ion source is 8V, the filament current is 110A, and the vacuum degree in the sample irradiation cavity is 3 x10^-7torr, temperature 40 ℃ to obtain a molybdenum sample.

Fig. 1 is a distribution diagram of Ar ion concentration and damage degree after irradiation in an experimental sample obtained by monte carlo simulation and calculation, and it can be found that the irradiation depth of Ar + in molybdenum does not exceed 320 μm, and the maximum irradiation ion concentration is less than 4.5 at.%. Whereas the damage caused by Ar + irradiation was-180 dpa.

The impurity concentrations of the molybdenum plates obtained in the examples of the present invention are shown in Table 1 below.

TABLE 1 impurity concentration in Mo

2) Evaluation of mechanical Properties and Corrosion Properties

In order to detect the influence of irradiation on the mechanical properties of the Mo matrix, microhardness is performed on samples before and after irradiation, and FIG. 2 shows the results of Vickers hardness measurement before and after Mo irradiation. It was found that the irradiation did not cause a significant difference. Fig. 3 is an open circuit potential diagram measured in a 3.5% sodium chloride aqueous solution before and after Mo irradiation, and it can be found that irradiation significantly increases the open circuit potential, which results in Mo having improved its corrosion resistance. FIG. 4 is a polarization plot, Table 2 by fitting the data.

TABLE 2 polarization curve fitting data

From experimental data it was found that the current density I0 after irradiation was more than four times smaller than that without irradiation, and also that the corrosion rate of Mo was reduced by more than 4 times by irradiation compared to that without irradiation. Fig. 5 is a graph of the measured impedance radius before and after irradiation, and it can be clearly found that the impedance radius of Mo after irradiation in a 3.5% sodium chloride aqueous solution is much larger than that without irradiation. 6a-6b are graphs of the morphology of the unirradiated Mo interface measured by electrochemical corrosion, and it can be seen that the surface has a very thick MoO3 oxide film with a thickness of about 3 μm, and that the oxide film is not very dense and has defects such as voids in some places. And fig. 7 is a morphology graph of an irradiated Mo interface measured by electrochemical corrosion, and it can be clearly found that the corrosion of the irradiated Mo is very slight, the electrochemical corrosion rate is greatly reduced compared with that of the irradiated Mo, and the thickness of an oxide film generated by corrosion is about 1.5 μm, which is more than half of that of the non-irradiated Mo. In conclusion, the Ar + irradiation Mo obviously improves the water corrosion resistance.

The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.

Claims

1. A refractory metal molybdenum surface treatment method resisting water corrosion is characterized by comprising the following steps:

1) preparation of molybdenum powder

2) press forming and sintering

3) hot working and heat treatment

in the step 3), impurities in the molybdenum plate are as follows: la is less than or equal to 0.0009, Mg is less than or equal to 0.0002, Fe is less than or equal to 0.0023, Cr is less than or equal to 0.0008, and Al is less than or equal to 0.0006;

4) preparation of the test samples

Cutting a molybdenum plate sample, finely grinding and polishing by using polishing paste, slightly etching the polished surface by using an aqueous solution containing 8-12% of potassium ferricyanide and sodium hydroxide, and cleaning residual corrosive by using water;

5) ion irradiation

Maintaining the vacuum degree in the sample irradiation cavity, irradiating the sample surface with Ar ion at set temperature, and selecting dosage of 3-4 x10¹⁶ion/cm²The acceleration voltage is 350-400KeV, and the average atomic potential energy is 25-35eV, so as to obtain the molybdenum block after surface treatment.

2. The method as claimed in claim 1, wherein in step 1), the ammonium molybdate solution is decomposed at a temperature of 450-500 ℃.

3. The method for treating the surface of the refractory metal molybdenum with resistance to water corrosion according to claim 1, wherein in the step 2), the pressureless sintering is carried out at the sintering temperature of 1960 ℃ for 6 hours.

4. The method as claimed in claim 1, wherein in the step 3), the heat rolling is performed at 1350 ℃, the temperature is maintained in a hydrogen atmosphere for 10min, the stress relief annealing temperature is 850-.

5. The method for treating the surface of the refractory metal molybdenum with resistance to water corrosion according to claim 1, wherein in the step 4), Mo slices are sequentially and finely ground by using No. 240, No. 400, No. 800, No. 1200 and No. 2000 water sandpaper respectively, and are polished by using polishing paste with the particle diameter of 0.5-1.5 μm.

6. The method as claimed in claim 1, wherein in step 5), the angle between the ion incidence direction and the sample surface is 97 °.

7. The method as claimed in claim 1, wherein in step 5), the filament voltage in the ion source is maintained at 8V and the filament current is maintained at 110A.

8. The method for treating the surface of the refractory metal molybdenum with resistance to water corrosion according to claim 1, wherein in the step 5), the vacuum degree in a sample irradiation cavity is kept at 1-3 x10^-7torr, temperature 25-100 ℃.