CN102560485A - Method for preparing hard protective film on magnesium alloy surface - Google Patents

Abstract

The invention provides a method for preparing a hard protective film on the surface of a magnesium alloy, which is characterized in that: first adopt arc ion plating, select a high-purity Cu target and use Ar gas as a working gas to deposit a metal Cu layer; then deposit the metal by electroplating Ni layer; finally by arc ion plating, select high-purity high-purity Cr target, use high-purity Ar gas and _N gas as working gas, deposit CrN monolayer film or Cr/CrN multilayer film on the upper surface of magnesium alloy, the present invention A method for preparing CrN single-layer film or Cr/CrN multi-layer film on the surface of magnesium alloy with good bonding force and no pollution to the environment is proposed to achieve the purpose of surface protection and modification of magnesium alloy components.

Description

Method for preparing hard protective film on magnesium alloy surface

technical field

The invention relates to surface treatment and surface modification technology of magnesium alloys, in particular to a method for depositing a CrN single layer or a Cr/CrN multilayer hard protective film on the surface of magnesium alloys to improve the corrosion resistance and corrosion resistance of magnesium alloy components. Abrasiveness, expanding the scope of use of magnesium alloy components.

Background technique

As a light engineering structural material, magnesium alloy has high specific strength, low elastic modulus, high thermal conductivity, electromagnetic shielding, good damping performance, high dimensional stability, good machinability and easy recycling, etc. Small and so on a series of excellent performance. It has a wide range of applications in transportation, communication products, aerospace, weaponry and other fields. These properties make magnesium alloys an attractive alternative to steel and aluminum, and one of the most promising engineering materials in the 21st century. However, the current application of magnesium alloy is still very low, and the annual production is only about 1% of that of aluminum alloy. The reason why the practical application of magnesium alloys is limited is that magnesium has some inherent performance defects, such as poor corrosion resistance, poor alloying strengthening effect, insufficient toughness, and poor wear resistance. In particular, the poor corrosion resistance and wear resistance have so far limited the application of magnesium alloys to statically loaded parts. Corrosion and wear are both surface phenomena of materials, so the most direct and effective way to improve the corrosion resistance and wear resistance of magnesium alloys is to carry out surface treatment and surface modification. Common surface treatment and surface modification methods of magnesium alloys mainly include electroplating, micro-arc oxidation (including anodic oxidation), thermal spraying, laser surface treatment, and vapor deposition technology. However, since magnesium is an extremely active element in chemical properties, the surface is easily corroded and oxidized during the electroplating process. Therefore, the pretreatment process of magnesium alloy surface electroplating is complicated and very difficult, and some plating solutions pollute the environment at the same time; magnesium alloy Surface micro-arc oxidation (including anodic oxidation) can form an oxide film on the surface of magnesium alloy, but the film is loose and porous, and the performance of the film layer is not ideal. Although there are some methods of sealing holes, the large-scale micro-arc oxidation treatment , requires a high-power power supply; the performance of the film produced by thermal spraying is not improved due to the porosity; laser surface treatment is not conducive to large-scale production due to the limited treatment area; vapor deposition technology can generate dense transition metal nitrides Or carbide film is an ideal surface modification treatment method for magnesium alloys.

Arc ion plating technology has high ionization rate, fast coating rate, and can prepare a certain thickness of film layer, which is an ideal technology for preparing hard protective film. The deposition of transition metal nitride film on the surface of magnesium alloy by arc ion plating is different from that on the surface of steel and aluminum alloy. Due to the great chemical activity of magnesium alloy, it is easy to form a thicker loose oxide film on the surface. The previous ion bombardment cleaning is also difficult to completely remove this layer of oxide film, which makes the bonding force between the deposited film and the magnesium alloy substrate very poor, and the film layer is easy to fall off. In general, the bombardment of high-energy ions on the surface results in high-density defects in the surface region, such as vacancies, interstitial atoms, and dislocations. Metal atoms can diffuse to the inside through vacancies and dislocations, and N atoms can also diffuse to the inside through gaps and dislocations, so that a transition layer can be formed on the substrate surface. The existence of the transition layer forms a deep interface, which reduces the internal stress caused by lattice mismatch, thereby improving the bonding force. In this sense, the higher the temperature, the greater the ion bombardment energy, which is more conducive to obtaining high binding force. However, our experiments show that for arc ion plating to deposit transition metal nitride films on magnesium alloys, too high a bias voltage is not conducive to obtaining a strong bonding force. The reasons are mainly due to two aspects. First of all, the high temperature caused by the high bias aggravates the softening of the constituent phase β-Al ₁₂ Mg ₁₇ of the AZ series magnesium alloy, and the sheet sample will have serious bending deformation caused by uneven temperature. In addition, magnesium and N ₂ gas can also react chemically at high temperature to produce powdery Mg ₃ N ₂ , which causes serious etching and evaporation on the surface of magnesium alloy. Secondly, because the thermal expansion coefficients of Mg and transition metal nitrides are very different, too high deposition temperature will lead to a large tensile stress between the film layer and the substrate after cooling, thereby reducing the bonding force of the film. Therefore, the temperature should not be too high in consideration of reducing the thermal stress at the interface and the magnesium alloy substrate. In this way, it is not easy to control the deposition temperature of directly depositing the transition metal nitride film layer on the magnesium alloy. Because the film prepared by arc ion plating will have a certain number of large particles and growth defects (micropores, columnar grain boundaries, etc.), and the electrode potential of the magnesium alloy is very negative, and it is easy to corrode. When there is a corrosive medium, it is easy to form micropores. and galvanic corrosion processes at large particles. In this way, a simple transition metal nitride film cannot have a good protective effect, and an electroplated metal Ni layer can be used to prevent the contact corrosion between the medium and the surface of the magnesium alloy. The multilayer film is used to improve the toughness of the film layer and not easily form cracks; at the same time, the layer boundary of the multilayer film can also reduce the number of micropores penetrating through the nitride film and improve the corrosion resistance of the film layer.

At present, there is no technology to obtain a CrN series film layer with a combination of a metal nitride layer and a metal Ni layer on a magnesium alloy with good bonding force.

Contents of the invention

Purpose of the invention: The present invention provides a method for preparing a hard protective film on the surface of a magnesium alloy, the purpose of which is to solve the problem of unsatisfactory film effects on the magnesium alloy in the past.

Technical solution: the present invention is achieved through the following technical solutions:

A method for preparing a hard protective film on the surface of a magnesium alloy is characterized in that: first adopt arc ion plating, select a high-purity Cu target and use Ar gas as a working gas to deposit a metal Cu layer; then deposit a metal Ni layer by electroplating; Finally, by arc ion plating, select a high-purity high-purity Cr target, use high-purity Ar gas and _N2 gas as working gases, and deposit a CrN single-layer film or a Cr/CrN multilayer film on the upper surface of the magnesium alloy, specifically including the following steps:

(1) Before the magnesium alloy parts are placed in the deposition device, they are mechanically ground and polished, and then pretreated with organic solvent degreasing and chemical degreasing;

(2) Fix the pre-treated magnesium alloy sample on the substrate holder in the arc ion plating device, and vacuum the equipment room of the arc ion plating device;

(3) Using a high-purity Cu target, the Ar gas is passed into the vacuum chamber, the arc is ignited under low pressure, and the metal Cu layer is deposited on the magnesium alloy; then vacuum heat treatment is performed in situ;

(4) The pre-deposited Cu film on the magnesium alloy should be subjected to vacuum aging treatment; the treatment temperature is 200°C-400°C, and the aging time is 0.5-2.0 hours.

(5), take out the magnesium alloy sample of the deposited Cu layer after heat treatment from the vacuum chamber, carry out electroplating metal Ni layer, carry out surface cleaning subsequently, dry;

(6) Put the sample of the dried electroplated metal Ni layer on the substrate support in the arc ion plating vacuum chamber, and evacuate the equipment room; introduce Ar gas, select a high-purity Cr target, start the arc, and use 600V-800V pulse bias with a duty cycle of 20%-40% for routine cleaning;

(7) After electroplating the metal Ni layer on the magnesium alloy, the CrN hard film is deposited by arc ion plating; during deposition, the reaction gas _N2 gas is added to keep the total pressure of the gas in the vacuum chamber at 0.03-2.0Pa; When layering a protective film, the ambient gas Ar gas and N ₂ gas can also be added periodically and alternately to _keep the total pressure of the gas in the vacuum chamber at 0.03-2.0Pa. The thickness of Cr phase and CrN phase can prepare multi-layer films with different modulation periods;

(8) After the deposition is completed, turn off the pulse bias voltage and arc power supply, turn off the gas, and wait for the sample to cool down to room temperature in the vacuum chamber, then open the vacuum chamber and take it out.

(5) In the step, the thickness of the Ni layer is 10-30 μm; the composition and process of the electroplating solution used for electroplating the metal Ni layer are as follows: nickel sulfate 200-350g/L, nickel chloride 20-40g/L, boric acid 20-40g/L , coumarin 1~2 g/L, Ni plating additive 1~2 g/L, the balance is deionized water, pre-plating solution PH4~6; electroplating temperature is 10℃-25℃, current density 1~10A/ dm ² , pre-plating at room temperature for 0.5h ~ 2.0h, take it out and rinse with running water to dry.

(3) The metal Cu layer in the step has a thickness of 0.1-1.0 μm.

(1) The mechanical grinding in the step is polished with 400#, 800#, 1200# and 1500# water-grinding sandpaper in sequence; the mechanical polishing is to use a cloth wheel of 18-25m/s, and use chromium oxide particle polishing paste; organic solvent degreasing And the chemical degreasing step is to put the ground and polished magnesium alloy into alcohol or acetone and ultrasonically clean it for 5-10 minutes, the temperature is room temperature, and the ultrasonic frequency is 22KHz; it is dried with cold wind.

(2) The vacuum degree of the step is less than 6.7×10 ^-3 Pa.

(3) In the step, the distance between the high-purity Cu target and the magnesium alloy sample is 100-400mm; in this step, the Ar gas is passed into the vacuum chamber, and the arc is ignited at a low pressure of 0.1-2.5Pa to deposit the Cu film; the arc current is 40 -80A, arc voltage 20-30V; apply pulse bias voltage 200-600V bombardment on the magnesium alloy sample, duty cycle 15-45%, frequency 51KHz;

(5) The composition and process of the electroplating solution for electroplating the metal Ni layer in the step: nickel sulfate 200-350g/L, nickel chloride 20-40g/L, boric acid 20-40g/L, coumarin 1-2 g/L, Ni plating additive 1~2 g/L, balance is deionized water, pre-plating solution PH4~6; electroplating temperature is room temperature, current density 1~10A/dm ² , pre-plating 0.5h~2.0h, take it out and use running water Rinse and dry.

(6) Vacuuming in the step, after the vacuum degree is less than 6.7×10 ^-3 Pa, in this step, Ar gas is passed into the vacuum chamber, and the arc is ignited at a low pressure of 0.1-2.5Pa, and the arc current is 40-80A , The arc voltage is 20-30V; a pulse bias voltage of 400-800V is applied to the magnesium alloy sample for bombardment, the duty cycle is 15-45%, and the frequency is 51KHz; the bombardment time is 1-5min.

(7) The ambient gas in the step is Ar or N ₂ gas. The two gases can be fed separately or alternately. The feeding time of each gas can be adjusted. When Ar and N ₂ gas are fed alternately, the Ar and N ₂ The time ratio of gas is 1:1~3; the pressure in the cavity is controlled at 0.1-2.5Pa; pulse bias voltage 0-400V is applied on the magnesium alloy sample, the duty cycle is 10-40%, and the frequency is 51KHz; the magnesium alloy substrate Temperature 25-200℃; arc current 40-80A, arc voltage 20-30V.

Advantages and effects: the present invention provides a method for preparing a hard protective film on the surface of a magnesium alloy, which first adopts arc ion plating, selects a high-purity Cu target and uses Ar gas as a working gas to deposit a metal Cu layer; then through electroplating, deposit Metal Ni layer; finally, through arc ion plating, select high-purity high-purity Cr target, use high-purity Ar gas and N ₂ gas as working gas, and deposit CrN single-layer film or Cr/CrN multi-layer film on the upper surface of magnesium alloy.

The specific method is as follows:

1. Pretreatment of magnesium alloy surface; mechanical grinding, polishing and ultrasonic cleaning with alcohol liquid, etc.

2. Fix the pre-treated magnesium alloy sample on the substrate holder in the arc ion plating device, and vacuum the equipment room;

3. Put Ar gas into the vacuum chamber, ignite the arc under low pressure, and deposit the metal Cu layer on the magnesium alloy; then perform vacuum heat treatment in situ.

4. Take out the magnesium alloy sample of deposited Cu layer after heat treatment from the vacuum chamber, and carry out electroplating metal Ni layer. Then wash the surface and let it dry.

5. Put the sample of the dried electroplated metal Ni layer on the substrate holder in the arc ion plating vacuum chamber, and evacuate the equipment room.

6. Introduce Ar gas, select a high-purity Cr target, start the arc, and use high pulse bias voltage for conventional cleaning treatment; then enter the growth gas, reduce the applied pulse bias voltage, adjust the sample temperature, and control the arc of the metal Cr target The arc current and arc voltage of the power supply are used to grow a CrN single-layer film or a Cr/CrN multi-layer film on a magnesium alloy sample.

5. After the deposition is over, turn off the pulse bias voltage and arc power supply, turn off the gas, wait for the sample to cool to room temperature in the vacuum chamber, open the vacuum chamber to take out the sample.

Compared with the prior art, the present invention has significant advantages: (1) deposit metal Cu layer by arc ion plating on the magnesium alloy, and improve the bonding strength of Cu layer and magnesium alloy through aging heat treatment; due to the Cu layer, The process of activating and pre-plating a Zn or Zn-Al alloy layer in the process of electroplating a metal Ni layer on the surface of a common magnesium alloy is omitted, so that electroplating a metal Ni layer becomes easy. (2) Arc ion plating technology is used to grow CrN single-layer film or Cr/CrN multilayer film on the Ni layer on the surface of magnesium alloy, which does not pollute the environment and meets environmental protection requirements; (3) The plating solution used for electroplating the metal Ni layer is cheap and Does not contain components that seriously pollute the environment (4) The nitride film layer grown on the metal Ni layer on the surface of the magnesium alloy has high bonding strength, the film thickness can reach 10-20μm, high hardness, and wear resistance. (5) The saprophytic resistance of the film layer is greatly improved due to the electroplated metal Ni layer; (6) The film layer of the present invention has a fast growth rate and a large growth area, and is suitable for large-scale industrial production.

Description of drawings:

Figure 1 is the elemental line scan diagram of the surface morphology and cross section of the Cr/CrN multilayer film when the time ratio of Ar gas and _N gas is 2min:2min. 1-2 is the cross-sectional morphology and element line scan diagram;

Figure 2 is the surface morphology and element line scan diagram of the cross section of the Cr/CrN multilayer film when the time ratio of Ar gas and _N gas is 2min:6min, where Figure 2-1 is the surface morphology, 2-2 is the cross-sectional morphology and element line scan.

The specific embodiment: the present invention will be further described below in conjunction with accompanying drawing:

As shown in Figure 1, the present invention provides a method for preparing a hard protective film on the surface of a magnesium alloy, first adopting arc ion plating, selecting a high-purity Cu target and using Ar gas as a working gas to deposit a metal Cu layer; then by electroplating, Deposit metal Ni layer; finally, through arc ion plating, select high-purity high-purity Cr target, use high-purity Ar gas and _N2 gas as working gas, deposit CrN single-layer film or Cr/CrN multi-layer film on the upper surface of magnesium alloy, Arc ion plating device is a common equipment for growing metal film and hard film. High-purity metal Cu and Cr, high-purity Ar gas and _N2 gas are also commonly used raw materials in industry.

The present invention specifically comprises the following steps:

(1) Before the magnesium alloy parts are placed in the deposition device, they are mechanically ground and polished, and then pretreated with organic solvent degreasing and chemical degreasing;

(2) Fix the pre-treated magnesium alloy sample on the substrate holder in the arc ion plating device, and vacuum the equipment room of the arc ion plating device;

(3) Using a high-purity Cu target, the Ar gas is passed into the vacuum chamber, the arc is ignited under low pressure, and the metal Cu layer is deposited on the magnesium alloy; then vacuum heat treatment is performed in situ;

(4) The pre-deposited Cu film on the magnesium alloy should be subjected to vacuum aging treatment; the treatment temperature is 200°C-400°C, and the aging time is 0.5-2.0 hours.

(5), take out the magnesium alloy sample of the deposited Cu layer after heat treatment from the vacuum chamber, carry out electroplating metal Ni layer, carry out surface cleaning subsequently, dry;

(6) Put the sample of the dried electroplated metal Ni layer on the substrate support in the arc ion plating vacuum chamber, and evacuate the equipment room; introduce Ar gas, select a high-purity Cr target, start the arc, and use 600V-800V pulse bias with a duty cycle of 20%-40% for routine cleaning;

(7) After electroplating the metal Ni layer on the magnesium alloy, the CrN hard film is deposited by arc ion plating; during deposition, the reaction gas _N2 gas is added to keep the total pressure of the gas in the vacuum chamber at 0.03-2.0Pa; When layering a protective film, the ambient gas Ar gas and N ₂ gas can also be added periodically and alternately to _keep the total pressure of the gas in the vacuum chamber at 0.03-2.0Pa. The thickness of Cr phase and CrN phase can prepare multi-layer films with different modulation periods;

(8) After the deposition is completed, turn off the pulse bias voltage and arc power supply, turn off the gas, and wait for the sample to cool down to room temperature in the vacuum chamber, then open the vacuum chamber and take it out.

Specifically, in the "(5)" step, the thickness of the Ni layer is 10-30 μm; the composition and process of the electroplating solution used for electroplating the metal Ni layer are as follows: nickel sulfate 200-350g/L, nickel chloride 20-40g/L, boric acid 20～40g/L, coumarin 1～2 g/L, Ni plating additive 1～2 g/L, the balance is deionized water, pre-plating solution PH4～6; electroplating temperature 10℃-25℃, current density 1～10A/dm ² , pre-plating at room temperature for 0.5h～2.0h, take it out and rinse with running water to dry.

(3) The metal Cu layer in the step has a thickness of 0.1-1.0 μm.

(1) The mechanical grinding in the step is polished with 400#, 800#, 1200# and 1500# water-grinding sandpaper in sequence; the mechanical polishing is to use a cloth wheel of 18-25m/s, and use chromium oxide particle polishing paste; organic solvent degreasing And the chemical degreasing step is to put the ground and polished magnesium alloy into alcohol or acetone and ultrasonically clean it for 5-10 minutes, the temperature is room temperature, and the ultrasonic frequency is 22KHz; it is dried with cold wind.

(2) The vacuum degree of the step is less than 6.7×10 ^-3 Pa.

(3) In the step, the distance between the high-purity Cu target and the magnesium alloy sample is 100-400mm; in this step, the Ar gas is passed into the vacuum chamber, and the arc is ignited at a low pressure of 0.1-2.5Pa to deposit the Cu film; the arc current is 40 -80A, arc voltage 20-30V; apply pulse bias voltage 200-600V bombardment on the magnesium alloy sample, duty cycle 15-45%, frequency 51KHz;

(5) The composition and process of the electroplating solution for electroplating the metal Ni layer in the step: nickel sulfate 200-350g/L, nickel chloride 20-40g/L, boric acid 20-40g/L, coumarin 1-2 g/L, Ni plating additive 1~2 g/L, balance is deionized water, pre-plating solution PH4~6; electroplating temperature is room temperature, current density 1~10A/dm ² , pre-plating 0.5h~2.0h, take it out and use running water Rinse and dry.

(6) Vacuuming in the step, after the vacuum degree is less than 6.7×10 ^-3 Pa, in this step, Ar gas is passed into the vacuum chamber, and the arc is ignited at a low pressure of 0.1-2.5Pa, and the arc current is 40-80A , The arc voltage is 20-30V; a pulse bias voltage of 400-800V is applied to the magnesium alloy sample for bombardment, the duty cycle is 15-45%, and the frequency is 51KHz; the bombardment time is 1-5min.

(7) In the step, the ambient gas is introduced into the vacuum chamber, the pressure in the chamber is controlled, the applied pulse bias voltage is reduced, and a transition metal hard film is deposited on the magnesium alloy. The ambient gas in this step is Ar or N ₂ gas, The two gases can be fed separately or alternately, and the feeding time of each gas can be adjusted. When Ar and N ₂ gas are fed alternately, the time ratio of Ar and N ₂ gas is 1:1~3; the pressure in the chamber is controlled At 0.1-2.5Pa; apply pulse bias voltage 0-400V, duty cycle 10-40%, frequency 51KHz on the magnesium alloy sample; magnesium alloy substrate temperature 25-200℃; arc current 40-80A, arc voltage 20- 30V.

In the embodiment of the present invention, AZ31B magnesium alloy is selected. The following are preferred embodiments of the present invention.

Example 1

AZ31B magnesium alloy is selected to be processed into samples with a side length of 20×15mm and a thickness of 3mm, and the target material is high-purity Cu or Cr target.

The specific operation steps are:

(1) Pretreatment of magnesium alloy: Degrease and decontaminate the processed magnesium alloy sample with common detergent, then polish the sample with 400-1500# sandpaper in turn, and finally polish it mechanically. Put the polished magnesium alloy sample into alcohol or acetone liquid for ultrasonic cleaning for 5 minutes, dry it with cold air, and set it aside.

(2) Fix the pretreated magnesium alloy sample on the substrate holder in the vacuum chamber of the equipment, and the distance between the sample and the Cu target is 100 mm. Then close the vacuum chamber, and evacuate to a background vacuum of 6.7×10 ^-3 Pa by means of a mechanical pump and a diffusion pump. After the chamber pressure reaches the background vacuum, Ar gas is introduced. When the vacuum is stable at 0.3Pa, the target power is turned on, the arc current is 70A, the arc voltage is 20V, the pulse bias is 400V, the duty cycle is 40%, and the frequency 51KHz, deposit Cu film on the magnesium alloy sample, time 10min.

(3) After the deposition of the Cu film, the sample was heated in situ at 500°C and kept for 1.0 hour.

(4) Take out the Cu-deposited and aged sample from the vacuum chamber, wash it in distilled water for a while, and put it in the electroplating solution for electroplating. Plating solution composition and process: nickel sulfate 300g/L, nickel chloride 20g/L, boric acid 40g/L, coumarin 2 g/L, Ni plating additive 1 g/L, the balance is deionized water, pre-plating solution The pH value is 6; the electroplating temperature is room temperature, the current density is 5A/dm ² , pre-plating at room temperature for 1 hour, and rinsed with running water to dry after taking it out.

(5) The Ni-plated and dried sample is placed on the substrate holder in the arc ion plating chamber, the high-purity Cr target is 200mm away from the sample, and the vacuum is pumped to 6.7×10 ^-3 Pa.

(6) Introduce Ar gas, when the vacuum is stable at 0.6Pa, turn on the target power supply, the arc current is 70A, the arc voltage is 20V, the pulse bias voltage is 600V, the duty cycle is 40%, the frequency is 51KHz, and the bombardment is carried out for 2 minutes .

(3) After the sample is bombarded, Ar gas and N ₂ gas are periodically introduced, the time ratio is 2min:6min, the gas pressure is kept at 0.6Pa, the pulse bias voltage is 200V, the duty cycle is 20%, the frequency is kept at 51KHz, and the Cr /CrN multilayer film growth. The growth time is 60min.

(4) After the deposition, turn off the pulse bias voltage and arc power supply, turn off the gas, wait for the sample to cool to room temperature in the vacuum chamber, open the vacuum chamber to take out the sample.

Figure 2 shows the Cr/CrN multilayer film grown on the surface of the magnesium alloy under this condition.

Example 2

AZ31B magnesium alloy is selected to be processed into samples with a side length of 20×15mm and a thickness of 3mm, and the target material is high-purity Cu or Cr target.

The specific operation steps are:

(1) Pretreatment of magnesium alloys: Degreasing and decontaminating the processed magnesium alloy samples with ordinary detergent, then grinding the samples with 400-1500# sandpaper in turn, and finally mechanically polishing. The polished magnesium alloy Alloy samples were ultrasonically cleaned in alcohol or acetone liquid for 5 minutes, dried with cold air, and set aside.

(2) Fix the pretreated magnesium alloy sample on the substrate holder in the vacuum chamber of the equipment, and the distance between the sample and the Cu target is 150mm. Then close the vacuum chamber, and evacuate to a background vacuum of 6.7×10 ^-3 Pa by means of a mechanical pump and a diffusion pump. After the chamber pressure reaches the background vacuum, Ar gas is introduced. When the vacuum is stable at 0.5Pa, the target power is turned on, the arc current is 60A, the arc voltage is 20V, the pulse bias is 500V, the duty cycle is 40%, and the frequency 51KHz, deposit Cu film on the magnesium alloy sample, time 10min.

(3) After the deposition of the Cu film, the sample was heated in situ at 450°C and kept for 1.0 hour.

(4) Take out the Cu-deposited and aged sample from the vacuum chamber, wash it in distilled water for a while, and put it in the electroplating solution for electroplating. Plating solution composition and process: nickel sulfate 350g/L, nickel chloride 25g/L, boric acid 33g/L, coumarin 1 g/L, Ni plating additive 2 g/L, the balance is deionized water, pre-plating solution The pH value is 6; the electroplating temperature is room temperature, the current density is 8A/dm ² , pre-plating at room temperature for 1 hour, and rinsed with running water to dry after taking it out.

(5) The Ni-plated and dried sample is placed on the substrate holder in the arc ion plating chamber, the high-purity Cr target is 200mm away from the sample, and the vacuum is pumped to 6.7×10 ^-3 Pa.

(6) Introduce Ar gas, when the vacuum is stable at 0.6Pa, turn on the target power supply, the arc current is 60A, the arc voltage is 20V, the pulse bias voltage is 600V, the duty cycle is 40%, the frequency is 51KHz, and the bombardment is carried out for 2 minutes .

(3) After the sample is bombarded, Ar gas and N ₂ gas are periodically introduced, the time ratio is 2min:4min, the gas pressure is kept at 0.6Pa, the pulse bias voltage is 150V, the duty cycle is 20%, the frequency is kept at 51KHz, and the Cr /CrN multilayer film growth. The growth time is 60min.

(4) After the deposition, turn off the pulse bias voltage and arc power supply, turn off the gas, wait for the sample to cool to room temperature in the vacuum chamber, open the vacuum chamber to take out the sample.

Example 3

AZ31B magnesium alloy is selected to be processed into samples with a side length of 20×15mm and a thickness of 3mm, and the target material is high-purity Cu or Cr target.

The specific operation steps are:

(1) Pretreatment of magnesium alloy: Degrease and decontaminate the processed magnesium alloy sample with common detergent, then polish the sample with 400-1500# sandpaper in turn, and finally polish it mechanically. Put the polished magnesium alloy sample into alcohol or acetone liquid for ultrasonic cleaning for 5 minutes, dry it with cold air, and set it aside.

(2) Fix the pretreated magnesium alloy sample on the substrate holder in the vacuum chamber of the equipment, and the distance between the sample and the Cu target is 220 mm. Then close the vacuum chamber, and evacuate to a background vacuum of 6.7×10 ^-3 Pa by means of a mechanical pump and a diffusion pump. After the chamber pressure reaches the background vacuum, Ar gas is introduced. When the vacuum is stable at 0.6Pa, the target power is turned on, the arc current is 60A, the arc voltage is 20V, the pulse bias is 400V, the duty cycle is 40%, and the frequency 51KHz, deposit Cu film on the magnesium alloy sample, time 10min.

(3) After the deposition of the Cu film, the sample was heated in situ at 550°C and kept for 0.5 hours.

(4) Take out the Cu-deposited and aged sample from the vacuum chamber, wash it in distilled water for a while, and put it in the electroplating solution for electroplating. Plating solution composition and process: nickel sulfate 290g/L, nickel chloride 36g/L, boric acid 30g/L, coumarin 2 g/L, Ni plating additive 2 g/L, the balance is deionized water, pre-plating solution The pH value is 6; the electroplating temperature is room temperature, the current density is 3A/dm ² , pre-plating at room temperature for 1 hour, and rinsed with running water to dry after taking it out.

(5) The Ni-plated and dried sample is placed on the substrate holder in the arc ion plating chamber, the high-purity Cr target is 220 mm away from the sample, and the vacuum is pumped to 6.7×10 ^-3 Pa.

(6) Introduce Ar gas, when the vacuum is stable at 0.6Pa, turn on the target power supply, the arc current is 70A, the arc voltage is 20V, the pulse bias voltage is 550V, the duty cycle is 40%, the frequency is 51KHz, and the bombardment time is 2min .(3) After the sample is bombarded, feed N ₂ gas, keep the gas pressure at 0.6Pa, reduce the pulse bias voltage to 150V, duty cycle 20%, frequency at 51KHz, and grow CrN monolayer film. The growth time is 50min.

(4) After the deposition, turn off the pulse bias voltage and arc power supply, turn off the gas, wait for the sample to cool to room temperature in the vacuum chamber, open the vacuum chamber to take out the sample.

the

Example 4

AZ31B magnesium alloy is selected to be processed into samples with a side length of 20×15mm and a thickness of 3mm, and the target material is high-purity Cu or Cr target.

The specific operation steps are:

(1) Pretreatment of magnesium alloy: Degrease and decontaminate the processed magnesium alloy sample with common detergent, then polish the sample with 400-1500# sandpaper in turn, and finally polish it mechanically. Put the polished magnesium alloy sample into alcohol or acetone liquid for ultrasonic cleaning for 5 minutes, dry it with cold air, and set it aside.

(2) Fix the pretreated magnesium alloy sample on the substrate holder in the vacuum chamber of the equipment, and the distance between the sample and the Cu target is 200mm. Then close the vacuum chamber, and evacuate to a background vacuum of 5.2×10 ^-3 Pa by means of a mechanical pump and a diffusion pump. After the chamber pressure reaches the background vacuum, Ar gas is introduced. When the vacuum is stable at 0.3Pa, the target power is turned on, the arc current is 80A, the arc voltage is 20V, the pulse bias is 300V, the duty cycle is 40%, and the frequency 51KHz, deposit Cu film on the magnesium alloy sample, time 10min.

(3) After the deposition of the Cu film, the sample was heated in situ at 450°C and kept for 1.5 hours.

(4) Take out the Cu-deposited and aged sample from the vacuum chamber, wash it in distilled water for a while, and put it in the electroplating solution for electroplating. Plating solution composition and process: electroplating solution composition and process: nickel sulfate 250g/L, nickel chloride 35g/L, boric acid 20g/L, coumarin 2 g/L, Ni plating additive 1 g/L, the balance is to Ionized water, the pH value of the pre-plating solution is 5; the electroplating temperature is room temperature, the current density is 5A/dm ² , and the pre-plating is at room temperature for 1 hour. After taking it out, rinse it with running water and dry it.

(5) The Ni-plated and dried sample is placed on the substrate holder in the arc ion plating chamber, the high-purity Cr target is 200mm away from the sample, and the vacuum is pumped to 6.7×10 ^-3 Pa.

(6) Introduce Ar gas, when the vacuum is stable at 0.6Pa, turn on the target power supply, the arc current is 65A, the arc voltage is 20V, the pulse bias voltage is 600V, the duty cycle is 40%, the frequency is 51KHz, and the bombardment is carried out for 2 minutes .

(7) After the sample is bombarded, feed N ₂ gas, keep the gas pressure at 0.6Pa, reduce the pulse bias voltage to 200V, the duty cycle is 20%, and the frequency is kept at 51KHz to grow the CrN monolayer film. The growth time is 50min.

(4) After the deposition, turn off the pulse bias voltage and arc power supply, turn off the gas, wait for the sample to cool to room temperature in the vacuum chamber, open the vacuum chamber to take out the sample.

Example 5

AZ31B magnesium alloy is selected to be processed into samples with a side length of 20×15mm and a thickness of 3mm, and the target material is high-purity Cu or Cr target.

The specific operation steps are:

(1) Pretreatment of magnesium alloy: Degrease and decontaminate the processed magnesium alloy sample with common detergent, then polish the sample with 400-1500# sandpaper in turn, and finally polish it mechanically. Put the polished magnesium alloy sample into alcohol or acetone liquid for ultrasonic cleaning for 5 minutes, dry it with cold air, and set it aside.

(2) Fix the pretreated magnesium alloy sample on the substrate holder in the vacuum chamber of the equipment, and the distance between the sample and the Cu target is 100 mm. Then close the vacuum chamber, and evacuate to a background vacuum of 6.7×10 ^-3 Pa by means of a mechanical pump and a diffusion pump. After the chamber pressure reaches the background vacuum, Ar gas is introduced. When the vacuum is stable at 0.3Pa, the target power is turned on, the arc current is 70A, the arc voltage is 20V, the pulse bias is 400V, the duty cycle is 40%, and the frequency 51KHz, deposit Cu film on the magnesium alloy sample, time 10min.

(3) After the deposition of the Cu film, the sample was heated in situ at 500°C and kept for 1.0 hour.

(4) Take out the Cu-deposited and aged sample from the vacuum chamber, wash it in distilled water for a while, and put it in the electroplating solution for electroplating. Plating solution composition and process: nickel sulfate 300g/L, nickel chloride 20g/L, boric acid 40g/L, coumarin 2 g/L, Ni plating additive 1 g/L, the balance is deionized water, pre-plating solution The pH value is 6; the electroplating temperature is room temperature, the current density is 5A/dm ² , pre-plating at room temperature for 1 hour, and rinsed with running water to dry after taking it out.

(5) The Ni-plated and dried sample is placed on the substrate holder in the arc ion plating chamber, the high-purity Cr target is 200mm away from the sample, and the vacuum is pumped to 6.7×10 ^-3 Pa.

(6) Introduce Ar gas, when the vacuum is stable at 0.6Pa, turn on the target power supply, the arc current is 70A, the arc voltage is 20V, the pulse bias voltage is 600V, the duty cycle is 40%, the frequency is 51KHz, and the bombardment is carried out for 2 minutes .

(3) After the sample is bombarded, Ar gas and N ₂ gas are periodically introduced, the time ratio is 2min:2min, the gas pressure is kept at 0.6Pa, the pulse bias is 200V, the duty cycle is 20%, the frequency is kept at 51KHz, and the Cr /CrN multilayer film growth. The growth time is 60min.

(4) After the deposition, turn off the pulse bias voltage and arc power supply, turn off the gas, wait for the sample to cool to room temperature in the vacuum chamber, open the vacuum chamber to take out the sample.

Figure 1 shows the Cr/CrN multilayer film grown on the surface of magnesium alloy under this condition.

The invention proposes a method for preparing a CrN single-layer film or a Cr/CrN multi-layer film on the surface of a magnesium alloy with good bonding force and no pollution to the environment, so as to realize the purpose of surface protection and modification of magnesium alloy components.

Claims (9)

1. a method for preparing a hard protective film on the surface of a magnesium alloy is characterized in that: first adopt arc ion plating, select high-purity Cu target and use Ar gas as working gas, deposit metal Cu layer; then by electroplating, deposit metal Ni layer; finally through arc ion plating, select high-purity high-purity Cr target, use high-purity Ar gas and _N2 gas as working gas, deposit CrN single-layer film or Cr/CrN multi-layer film on the upper surface of magnesium alloy, specifically include the following step: (1) Before the magnesium alloy parts are placed in the deposition device, they are mechanically ground and polished, and then pretreated with organic solvent degreasing and chemical degreasing; (2) Fix the pre-treated magnesium alloy sample on the substrate holder in the arc ion plating device, and vacuum the equipment room of the arc ion plating device; (3) Using a high-purity Cu target, the Ar gas is passed into the vacuum chamber, the arc is ignited under low pressure, and the metal Cu layer is deposited on the magnesium alloy; then vacuum heat treatment is performed in situ; (4) The pre-deposited Cu film on the magnesium alloy should be subjected to vacuum aging treatment; the treatment temperature is 200°C-400°C, and the aging time is 0.5-2.0 hours; (5), take out the magnesium alloy sample of the deposited Cu layer after heat treatment from the vacuum chamber, carry out electroplating metal Ni layer, carry out surface cleaning subsequently, dry; (6) Put the sample of the dried electroplated metal Ni layer on the substrate support in the arc ion plating vacuum chamber, and evacuate the equipment room; introduce Ar gas, select a high-purity Cr target, start the arc, and use 600V-800V pulse bias with a duty cycle of 20%-40% for routine cleaning; (7) After electroplating the metal Ni layer on the magnesium alloy, the CrN hard film is deposited by arc ion plating; during deposition, the reaction gas _N2 gas is added to keep the total pressure of the gas in the vacuum chamber at 0.03-2.0Pa; When layering a protective film, the ambient gas Ar gas and N ₂ gas can also be added periodically and alternately to _keep the total pressure of the gas in the vacuum chamber at 0.03-2.0Pa. The thickness of Cr phase and CrN phase can prepare multi-layer films with different modulation periods; (8) After the deposition is completed, turn off the pulse bias voltage and arc power supply, turn off the gas, and wait for the sample to cool down to room temperature in the vacuum chamber, then open the vacuum chamber and take it out. 2. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (5) in the step, the thickness of the Ni layer is 10-30 μm; the composition and process of the electroplating solution used for electroplating the metal Ni layer are as follows : Nickel sulfate 200~350g/L, nickel chloride 20~40g/L, boric acid 20~40g/L, coumarin 1~2 g/L, Ni plating additive 1~2 g/L, the balance is deionized Water, pre-plating solution PH4~6; electroplating temperature at 10°C-25°C, current density 1-10A/dm ² , pre-plating at room temperature for 0.5h-2.0h, take it out and rinse with running water to dry. 3. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (3) the thickness of the metal Cu layer in the step is 0.1-1.0 μm. 4. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (1) the mechanical grinding in the step is sequentially polished with 400#, 800#, 1200# and 1500# water-grinding sandpaper; For mechanical polishing, a cloth wheel of 18-25m/s is used, and chromium oxide particle polishing paste is used; the organic solvent degreasing and chemical degreasing steps are to put the ground and polished magnesium alloy into alcohol or acetone and ultrasonically clean it for 5-10min at room temperature. , the ultrasonic frequency is 22KHz; dry with cold air. 5. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (2) the degree of vacuum in the step is less than 6.7×10 ^-3 Pa. 6. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (3) in the step, the distance between the high-purity Cu target and the magnesium alloy sample is 100-400mm; in this step, Ar gas is passed into Vacuum chamber, ignite the arc under the low pressure of 0.1-2.5Pa, deposit Cu film; Ratio 15-45%, frequency 51KHz. 7. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (5) The composition and process of the electroplating solution for electroplating the metal Ni layer in the step: nickel sulfate 200-350g/L, chloride Nickel 20~40g/L, boric acid 20~40g/L, coumarin 1~2 g/L, Ni plating additive 1~2 g/L, the balance is deionized water, pre-plating solution PH4~6; electroplating temperature Room temperature, current density 1-10A/dm ² , pre-plating for 0.5h-2.0h, rinse with running water and dry after taking it out. 8. The method for preparing a hard protective film on the surface of magnesium alloy according to claim 1, characterized in that: (6) in the step of vacuuming, after the vacuum degree is less than 6.7×10 ^-3 Pa, in this step, Ar gas Pass into the vacuum chamber, ignite the arc under the low pressure of 0.1-2.5Pa, the arc current is 40-80A, the arc voltage is 20-30V; apply pulse bias voltage 400-800V to bombard the magnesium alloy sample, the duty cycle is 15 -45%, frequency 51KHz; bombardment time 1-5min. 9. The method for preparing a hard protective film on the surface of a magnesium alloy according to claim 1, characterized in that: (7) the ambient gas in the step is Ar or _N gas, and the two gases can be fed separately or alternately , the feeding time of each gas can be adjusted. When Ar and N ₂ gas are fed alternately, the time ratio of Ar and N ₂ gas is 1:1~3; the pressure in the chamber is controlled at 0.1-2.5Pa; Apply pulse bias voltage 0-400V, duty cycle 10-40%, frequency 51KHz; magnesium alloy substrate temperature 25-200°C; arc current 40-80A, arc voltage 20-30V.

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