Al-Cr coating and preparation method and application thereof

Abstract

The invention discloses an Al-Cr coating as well as a preparation method and application thereof. The Al-Cr coating comprises a toughness phase and a hardness strengthening phase, the toughness phase is an Al phase, and the hardness strengthening phase is an Al8Cr5 phase. The preparation method of the Al-Cr coating comprises the following steps that an Al < x > Cr < 100-x > alloy target material is sputtered and deposited on the surface of a base material through a direct current magnetron sputtering method or a pulse direct current magnetron sputtering method, the value of x ranges from 60 to 80, and then the Al-Cr coating is obtained. The Al-Cr coating provided by the invention has the advantages of high hardness, high toughness, high density, smooth surface, no crack and the like, is low in preparation cost, is green and environment-friendly in preparation process, can completely replace a hexavalent chromium coating, and is suitable for being used as a wear-resistant, corrosion-resistant and decorative coating on the surface of steel.

Description

Technical Field

[0001] The present invention relates to the technical field of surface strengthening of metal materials, and particularly relates to an Al-Cr coating and its preparation method and application. Background Art

[0002] Hexavalent chromium coatings have excellent properties such as high hardness, good wear resistance, good corrosion resistance, and the ability to maintain the bright metallic luster for a long time in the atmospheric environment, and are widely used as wear-resistant, corrosion-resistant, and decorative coatings on the surface of metal materials. However, although the hexavalent chromium coating has high hardness, it has high internal stress, which will cause the dimensional instability of the plated parts. Moreover, the hexavalent chromium coating will begin to lose its metallic luster when the temperature reaches above 500 °C, and its hardness will be significantly reduced. In addition, electroplating to form a hexavalent chromium coating usually requires a strongly acidic electroplating solution, and the current efficiency of electroplating chromium is low, and a large amount of hydrogen-containing bubbles will be generated at the cathode, entraining Cr 6+ Acid mist is emitted into the atmosphere, which will not only damage the digestive tract, respiratory tract, and nasal mucosa of people, but also cause dermatitis, eczema, and cancer when adhering to the skin. In addition, electroplating chromium plating solution is one of the most difficult electroplating pollution sources to treat, and it has great harm to the ecological environment and human health.

[0003] Physical vapor deposition (PVD) technology can be used to prepare Cr coatings. Compared with the electroplating chromium process, it is more environmentally friendly and has better application prospects. However, the Vickers hardness (HV) of the Cr coating prepared by the traditional PVD method is only 280-320, which is much lower than that of the hexavalent chromium coating (Vickers hardness is 800-1000). Although the Vickers hardness of the chromium nitride coating or chromium carbide coating deposited by the reactive PVD method can be increased to more than 2000, there are problems such as high brittleness of the coating, easy target poisoning, high cost of pure Cr targets, and low process stability, which are difficult to fully meet the actual application requirements, and currently cannot replace the hexavalent chromium coating prepared by the traditional electroplating method.

[0004] Therefore, it is of great significance to develop a Cr coating with high hardness, high toughness, high density, low preparation cost, green and environmentally friendly preparation process, and capable of completely replacing the hexavalent chromium coating. Summary of the Invention

[0005] The purpose of the present invention is to provide an Al-Cr coating and its preparation method and application.

[0006] The technical solution adopted by the present invention is as follows:

[0007] An Al-Cr coating, the composition of which includes a ductile phase and a hardness strengthening phase, the ductile phase is the Al phase, and the hardness strengthening phase is the Al8Cr5 phase.

[0008] Preferably, the Al-Cr coating is composed of nanocrystals with a particle size of 50 nm to 400 nm.

[0009] Preferably, the atomic percentage of Al in the Al-Cr coating is 20% to 80%.

[0010] More preferably, the atomic percentage of Al in the Al-Cr coating is 60% to 80%.

[0011] Preferably, the thickness of the Al-Cr coating is 1.2 μm to 1.8 μm.

[0012] A method for preparing the Al-Cr coating as described above includes the following steps: depositing an Al x Cr 100-x alloy target on the surface of a substrate by direct current magnetron sputtering or pulsed direct current magnetron sputtering, where the value of x is 60 to 80, thus obtaining the Al-Cr coating.

[0013] Preferably, the sputtering deposition is carried out under the condition of a temperature of 450 °C to 550 °C.

[0014] Preferably, the sputtering deposition is carried out under the condition of a target power density of 4 W / cm 2 ~6 W / cm 2 of.

[0015] Preferably, the sputtering deposition is carried out in a protective atmosphere.

[0016] Preferably, the protective atmosphere is an argon (Ar) atmosphere.

[0017] Preferably, the substrate is a metal substrate.

[0018] More preferably, the substrate is a steel material.

[0019] A steel material with the above Al-Cr coating covering its surface.

[0020] The beneficial effects of the present invention are as follows: The Al-Cr coating of the present invention has the advantages of high hardness, high toughness, high density, a flat surface without cracks, etc., and its preparation cost is low, the preparation process is green and environmentally friendly, and it can completely replace the hexavalent chromium coating, and is suitable as a wear-resistant, corrosion-resistant and decorative coating on the surface of steel materials.

[0021] Specifically:

[0022] 1) The Al-Cr coating of the present invention is composed of nanocrystals, with uniform grain size, no hydrogen, a dense and flat surface, and no cracks. Compared with the hexavalent chromium coating prepared by the traditional electroplating method, the coating is more dense, has no cracks, and has a higher actual use temperature (it can reach 650 °C);

[0023] 2) The hardness and toughness of the Al-Cr coating of the present invention can be flexibly adjusted (by adjusting the content of Al8Cr5 in the coating through the deposition temperature, thereby adjusting the hardness and toughness of the coating), and the applicable range is wider;

[0024] 3) The preparation cost of the Al-Cr coating of the present invention is significantly lower than that of the chromium nitride coating or chromium carbide coating deposited by the reactive PVD method (Al is the main component in the Al-Cr coating, and the price of Al is much lower than that of Cr, so the preparation cost of the coating is significantly reduced). Moreover, the preparation process of the Al-Cr coating is more stable and reliable, there is no problem of target poisoning, and the deposition rate is also faster, and the industrial application prospect is broader;

[0025] 4) The preparation method of the Al-Cr coating of the present invention is green and environmentally friendly, there is no problem of exhaust gas emission pollution, and it will not cause harm to the ecological environment and human health. Description of the Drawings

[0026] Figure 1 SEM diagram of the Al-Cr coating in Example 1.

[0027] Figure 2 XRD diagram of the Al-Cr coating in Example 1.

[0028] Figure 3 Nanohardness test result diagram of the Al-Cr coatings in Examples 1 to 3 at different temperatures. Detailed Embodiments

[0029] The present invention will be further explained and illustrated below in conjunction with specific embodiments.

[0030] Example 1:

[0031] An Al-Cr coating, and its preparation method is as follows:

[0032] 1) The No. 45 steel plate is mechanically ground and polished to a mirror surface, then ultrasonically cleaned with acetone and absolute ethanol for 15 minutes each in turn, dried, and then placed on the sample stage in the DC magnetron sputtering system. Then, the Al 70 Cr 30 alloy target (the target specification is Φ60mm×3mm) is installed on the corresponding target station of the DC magnetron sputtering system, and the distance between the target and the No. 45 steel plate is adjusted to 80 mm. Then, it is pre-pumped to the background vacuum degree of 5 Pa, and then the high-vacuum extraction system is started. After pumping the vacuum to the vacuum degree of 0.001 Pa to 0.01 Pa, the vacuum baking system is started to remove the residual adsorbed gas in the vacuum chamber;

[0033] 2) Turn off the vacuum baking system, evacuate to a vacuum of 0.001 Pa, then turn on the sample heating system and heat the No. 45 steel plate to 450 °C. Continue to evacuate to a vacuum of 5×10 -4 Pa, and then introduce Ar gas until the vacuum is 1.0 Pa. Start the DC magnetron sputtering system and adjust the target power density to 5 W / cm 2 , and sputter and clean the target;

[0034] 3) Remove the target baffle, maintain the vacuum in the chamber at 1.0 Pa and the target power density at 5 W / cm 2 for DC magnetron sputtering deposition. The deposition time is 60 min. Then turn off the DC sputtering deposition power supply, stop introducing Ar gas, turn off the sample heating system. Wait until the sample temperature drops below 100 °C, open the furnace and take out the sample to obtain an Al-Cr coating (thickness: 1.49 μm, atomic percentage of Al: 70%).

[0035] The scanning electron microscope (SEM) image of the Al-Cr coating in this example is as shown in Figure 1 the figure.

[0036] It can be seen from Figure 1 that the Al-Cr coating is composed of nanocrystals with particle sizes ranging from 50 nm to 400 nm. The coating is dense and there are no cracks.

[0037] The X-ray diffraction (XRD) pattern of the Al-Cr coating in this example is as shown in Figure 2 the figure.

[0038] It can be seen from Figure 2 that the Al-Cr coating is composed of Al phase (ductile phase) and Al8Cr5 phase (hardness strengthening phase).

[0039] The nano-hardness test results of the Al-Cr coating in this example at different temperatures are as shown in Figure 3 the figure.

[0040] It can be seen from Figure 3 that the nano-hardness of the Al-Cr coating at 450 °C is 12.7 GPa (high hardness), and the hardness is comparable to that of the hexavalent chromium coating prepared by the traditional electroplating method.

[0041] Example 2:

[0042] An Al-Cr coating, and its preparation method is as follows:

[0043] 1) Mechanically grind and polish the No. 45 steel plate to a mirror surface, then ultrasonically clean it with acetone and absolute ethanol for 15 min each, dry it, and then place it on the sample stage in the DC magnetron sputtering system. Then place the Al 80 Cr 20The alloy target (target specification: Φ60mm×3mm) is installed on the corresponding target station of the DC magnetron sputtering system, and the distance between the target and the No. 45 steel plate is adjusted to 80 mm. Then, it is pre-pumped to a background vacuum of 5 Pa, and the high-vacuum extraction system is started. After pumping the vacuum to a vacuum of 0.001 Pa to 0.01 Pa, the vacuum baking system is started to remove the residual adsorbed gas in the vacuum chamber;

[0044] 2) Close the vacuum baking system, pump the vacuum to 0.001 Pa, and start the sample heating system to heat the No. 45 steel plate to 550 °C. Continue to pump the vacuum to 5×10 -4 Pa, then introduce Ar gas until the vacuum is 1.0 Pa, start the DC magnetron sputtering system, and adjust the target power density to 5 W / cm 2 , and sputter and clean the target;

[0045] 3) Remove the target baffle, maintain the vacuum in the chamber at 1.0 Pa and the target power density at 5 W / cm 2 for DC magnetron sputtering deposition. The deposition time is 60 min. Then, turn off the DC sputtering deposition power supply, stop introducing Ar gas, turn off the sample heating system. Wait until the sample temperature drops below 100 °C, open the furnace and take out the sample to obtain an Al-Cr coating (thickness: 1.52 μm, atomic percentage of Al: 80%).

[0046] The nanohardness test results of the Al-Cr coating in this example at different temperatures are shown as Figure 3 follows.

[0047] It can be seen from Figure 3 that the nanohardness of the Al-Cr coating at 550 °C is 10.1 GPa (high hardness), and the hardness is equivalent to that of the hexavalent chromium coating prepared by the traditional electroplating method.

[0048] Example 3:

[0049] An Al-Cr coating is prepared as follows:

[0050] 1) Mechanically grind and polish the No. 45 steel plate to a mirror surface, then ultrasonically clean it with acetone and absolute ethanol for 15 min each, dry it, and place it on the sample stage in the DC magnetron sputtering system. Then, install the Al 60 Cr 40 alloy target (target specification: Φ60mm×3mm) on the corresponding target station of the DC magnetron sputtering system, and adjust the distance between the target and the No. 45 steel plate to 80 mm. Then, pre-pump to a background vacuum of 5 Pa, and start the high-vacuum extraction system. After pumping the vacuum to a vacuum of 0.001 Pa to 0.01 Pa, start the vacuum baking system to remove the residual adsorbed gas in the vacuum chamber;

[0051] 2) Turn off the vacuum baking system, evacuate to a vacuum degree of 0.001 Pa, then turn on the sample heating system to heat the No. 45 steel plate to 450 °C, continue to evacuate to a vacuum degree of 5×10 -4 Pa, then introduce Ar gas until the vacuum degree reaches 1.0 Pa, start the DC magnetron sputtering system, and adjust the target power density to 5 W / cm 2 , and sputter and clean the target material;

[0052] 3) Remove the target baffle, maintain the vacuum degree in the chamber at 1.0 Pa and the target power density at 5 W / cm 2 for DC magnetron sputtering deposition. The deposition time is 60 min. Then turn off the DC sputtering deposition power supply, stop introducing Ar gas, turn off the sample heating system. After the sample temperature drops below 100 °C, open the furnace to take out the sample to obtain an Al-Cr coating (thickness: 1.45 μm, atomic percentage of Al: 60%).

[0053] The nano-hardness test result graph of the Al-Cr coating in this embodiment at different temperatures is as Figure 3 shown.

[0054] It can be seen from Figure 3 that the nano-hardness of the Al-Cr coating at 450 °C is 11.1 GPa (high hardness), and the hardness is comparable to that of the hexavalent chromium coating prepared by the traditional electroplating method.

[0055] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. An Al-Cr coating, characterized in that, The composition includes a ductile phase and a hardness-strengthening phase. The ductile phase is the Al phase, and the hardness-strengthening phase is the Al8Cr5 phase.

2. The Al-Cr coating according to claim 1, wherein: The Al-Cr coating is composed of nanocrystals, and the particle size of the nanocrystals is 50 nm to 400 nm.

3. The Al-Cr coating according to claim 1 or 2, characterized in that: The atomic percentage of Al in the Al-Cr coating is 20% to 80%.

4. The Al-Cr coating according to claim 1 or 2, characterized in that: The thickness of the Al-Cr coating is 1.2 μm to 1.8 μm.

5. A method for preparing an Al-Cr coating according to any one of claims 1 to 4, characterized in that, It includes the following steps: Deposit an Al x Cr 100-x alloy target on the surface of the substrate by DC magnetron sputtering or pulsed DC magnetron sputtering, where the value of x is 60-80, to obtain an Al-Cr coating.

6. The preparation method according to claim 5, wherein: The sputtering deposition is carried out under the condition that the temperature is 450 °C to 550 °C.

7. The preparation method according to claim 5 or 6, characterized in that: The sputtering deposition is carried out under the condition that the target power density is 4 W / cm 2 to 6 W / cm 2 .

8. The preparation method according to claim 5 or 6, characterized in that: The sputtering deposition is carried out in a protective atmosphere.

9. The preparation method according to claim 5 or 6, characterized in that: The substrate is a metal substrate.

10. A kind of steel, characterized in that, The surface is covered with the Al-Cr coating according to any one of claims 1 to 4.

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