Highly densified alumina coating and process for its production

Abstract

The application discloses a high-densification alumina coating and a processing technology thereof, and belongs to the technical field of ceramic coating materials. The alumina coating comprises at least one alumina single layer, and a dense interface layer is formed on each alumina single layer by ion bombardment on the surface of the alumina single layer; the alumina single layer is composed of AlO x , wherein the oxygen content is 0

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic coating materials, in particular to a high densification alumina coating and a processing technology thereof. BACKGROUND

[0002] Alumina coating has been widely used in optics, reactor corrosion protection, high temperature protection, electronic insulation and other fields due to its excellent physical and chemical inertness and high temperature structural stability. The preparation of alumina coating mainly includes spraying, arc ion plating, pulsed laser deposition, high power pulsed magnetron sputtering and other technologies. However, the coating prepared by these technologies often has defects such as holes and cracks in the coating, which greatly reduces the density of the coating. With the development of the fourth generation lead-based reactor, there is a high requirement for the density of the alumina corrosion protection coating on the surface of the cladding tube. Therefore, improving the density of the alumina corrosion protection coating is the key to its commercial application.

[0003] At present, the methods for improving the density of the coating include: (1) increasing the deposition ion energy, which can avoid the generation of a large number of holes due to the sufficient energy diffusion of the ions on the substrate, but the stress of the coating is too high and the coating is easy to crack under external force. (2) Post-treatment of the coating, and optimization of the process parameters such as temperature, bias voltage and gas pressure in the deposition process. However, the post-treatment is difficult to promote the closure of large holes, the deposition temperature is limited by the substrate, the high bias voltage will cause high stress, and the low gas pressure will affect the sputtering efficiency. SUMMARY

[0004] The present application aims to provide a high densification alumina coating and a processing technology thereof, which solves the problem of many holes and poor density in the preparation process of the existing alumina coating. The present application combines high power pulsed magnetron sputtering and ion bombardment technology to realize high interface density in the preparation process, and realizes the preparation of high-performance alumina coating on the surface of high-temperature structural materials. It provides an advanced candidate material for the fourth generation lead-based reactor, high temperature protection and other fields, and also provides a new method for the development of coatings in the high-temperature industrial field of aviation and aerospace.

[0005] The present application is realized by the following technical scheme:

[0006] The present application provides a high densification alumina coating, which comprises at least one alumina single layer, and a dense interface layer formed on each alumina single layer by ion bombardment on the surface of the alumina single layer.

[0007] The alumina single layer is composed of AlO x , wherein the oxygen content is 0 < x < 1.5.

[0008] Further, in the high densification alumina coating, the thickness of the dense interface layer is 0-2 μm.

[0009] The application provides a processing technology of the high-densification alumina coating.

[0010] cleaning the substrate in a vacuum environment;

[0011] adopting high-power pulse magnetron sputtering to prepare an alumina single layer by taking argon as a sputtering gas and oxygen as a reaction gas;

[0012] adopting an arc discharge ion source to bombard the alumina single layer by using etching gas, so as to form a dense interface layer on the alumina single layer;

[0013] taking high-power pulse magnetron sputtering and arc discharge ion source bombardment as one cycle, and the processing technology is at least one cycle.

[0014] Further, in the processing technology of the high-densification alumina coating, the step of vacuum cleaning the substrate is as follows: the substrate is placed in a vacuum chamber, the vacuum chamber is vacuumized, and the vacuum degree is reduced to 3*10 -3 Pa, and then the vacuum chamber is heated to 200-400 ℃;

[0015] argon is filled, the gas pressure is controlled at 1-2 Pa, the pulse bias is turned on, the bias is controlled at 500-1000 V, the frequency is controlled at 50-80 KHz, and the pulse width is controlled at 20-100 μs.

[0016] Further, in the processing technology of the high-densification alumina coating, the substrate cleaning time is 10-20 min.

[0017] Further, in the processing technology of the high-densification alumina coating, the step of high-power pulse magnetron sputtering is as follows: argon and oxygen are filled, the gas pressure is controlled at 0.2-1 Pa, the pulse bias is turned on, the bias is controlled at 0-300 V, the frequency is controlled at 50-80 KHz, and the pulse width is controlled at 20-100 μs.

[0018] The aluminum target is sputtered by using a high-power pulse magnetron sputtering power source.

[0019] Further, in the processing technology of the high-densification alumina coating, the O / Al atomic ratio of the filled oxygen and argon is 1.37-1.7.

[0020] Further, in the processing technology of the high-densification alumina coating, the high-power pulse magnetron sputtering power source adopts a frequency control mode, the power is 1-5 kW, the peak current is 200-380 A, and the pulse width is 10-80 μs.

[0021] Further, in the processing technology of the high densification alumina coating, the step of arc discharge ion source bombardment is: the etching gas is introduced, the gas pressure is controlled at 0.3Pa-2Pa, the alumina monolayer is bombarded by the arc discharge ion source, the current is 50A-100A, and the ion energy is 50-200eV.

[0022] Further, in the processing technology of the high densification alumina coating, the etching gas includes but is not limited to argon, oxygen or nitrogen.

[0023] Compared with the prior art, the high densification alumina coating and the processing technology thereof have the following advantages and beneficial effects:

[0024] The high densification alumina coating and the processing technology thereof provided by the application combine ion bombardment and magnetron sputtering process, use the ion bombardment of the arc discharge ion source to form a dense interface layer of the alumina monolayer, effectively improve the densification of the whole alumina coating, effectively solve the problems of porosity and poor densification of the alumina coating, and ensure the structural stability of the alumina coating in a high-temperature and high-corrosion environment.

[0025] The ion bombardment of the arc discharge ion source can increase the kinetic energy of the deposited atoms on the substrate, improve the densification of the coating structure, and form a dense interface layer that can block the diffusion of cracks into the coating. The application provides a meaningful idea and preparation method for the protection of structural materials in high-temperature and strong-corrosion environments.

[0026] The high-power pulsed magnetron sputtering technology used in the application can deposit alumina in a non-stoichiometric ratio, continuously adjust the oxygen content in the coating, realize the controllable adjustment of the oxygen content, and obtain high-density alumina coatings with different interface densities by controlling the deposition time and the bombardment time. Through the adjustment of the interface density, the electrical, mechanical, crystallinity and other performances of the alumina are realized. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical scheme of the exemplary embodiments of the application, the following will briefly introduce the drawings needed in the embodiments. It should be understood that the following drawings only show some embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor. In the drawings:

[0028] Figure 1 The scanning electron microscope graph of the cross section of the high densification alumina of the test example 1 of the application and the traditional alumina;

[0029] Figure 2 The densification electron microscope graph of the high densification alumina of the test example 2 of the application;

[0030] Figure 3 The atomic ratio of high densification alumina of the present application test example 3;

[0031] Figure 4 The hardness and modulus of the alumina coating prepared under different oxygen flow before and after heat treatment of the present application test example 4;

[0032] Figure 5 The lead bismuth corrosion performance of the conventional and high densification alumina of the present application test example 5. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below with examples and drawings, the illustrative embodiments of the present application and their descriptions are only used to explain the present application, and do not limit the present application. The specific conditions are not marked in the examples, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked by the manufacturer, and are conventional products that can be purchased on the market.

[0034] The technical scheme of the specific embodiment of the present application is:

[0035] A high densification alumina coating, the alumina coating at least includes an alumina single layer, and a densification interface layer formed by ion bombardment on the surface of each alumina single layer is formed on each alumina single layer;

[0036] The alumina single layer is composed of AlO x , and the oxygen content is 0

[0037] The thickness of the alumina single layer can be adjusted according to the actual situation, and the thickness of the alumina single layer is determined by the deposition time, the longer the deposition time, the thicker the thickness of the alumina single layer. The thickness of the densification interface layer is 0-2 μm, and the thickness of the densification interface layer can be adjusted according to the actual situation, and is determined by the bombardment time, the longer the bombardment time, the thicker the thickness of the densification interface layer formed, and the thickness of the densification interface layer formed on the alumina single layer is usually less than the overall thickness of the alumina single layer. Each alumina single layer is composed of AlO x , 0

[0038] The processing technology of the high densification alumina coating includes:

[0039] (1) cleaning the substrate in a vacuum environment; the specific steps are: placing the substrate into a vacuum chamber, vacuumizing the vacuum chamber, and when the vacuum degree is reduced to 3*10 -3 Pa, heating the vacuum chamber to 200-400℃;

[0040] Fill in argon, the gas pressure control in 1Pa ~ 2Pa, open pulse bias: bias control in 500V ~ 1000V, frequency control in 50KHz ~ 80KHz, pulse width control in 20us ~ 100us;Cleaning time for 10min ~ 20min.

[0041] (2) with argon as sputtering gas, oxygen as reaction gas, using high power pulse magnetron sputtering aluminum target to prepare aluminum oxide single layer;Specific steps are as follows: fill in argon and oxygen, the O / Al atomic ratio of the filled oxygen and argon is 0.5 ~ 1.5, the gas pressure is controlled in 0.2Pa ~ 1Pa, open pulse bias: bias control in 0 ~ 300V, frequency control in 50KHz ~ 80KHz, pulse width control in 20us ~ 100us;

[0042] Using high power pulse magnetron sputtering power source to sputter aluminum target, high power pulse magnetron sputtering power source uses frequency control mode, power 1kW ~ 5kW, peak current 200A ~ 380A, pulse width 10us ~ 80us.

[0043] (3) using arc discharge ion source, pass in etching gas, the gas pressure is controlled in 0.3Pa ~ 2Pa, using etching gas to bombard aluminum oxide single layer, current 50A ~ 100A, ion energy 50 ~ 200eV, forming a dense interface layer on the aluminum oxide single layer. The etching gas includes but is not limited to: argon, oxygen or nitrogen.

[0044] (4) with high power pulse magnetron sputtering to arc discharge ion source bombardment as a cycle, the processing technology at least completes one cycle.

[0045] After completing the processing technology, annealing treatment can also be carried out: adjust the temperature to 350℃ ~ 700℃, heat preservation 2h ~ 4h, through annealing treatment can further increase the density of coating structure.

[0046] High power pulse instantaneous release a large number of charged particles, it is difficult to ensure the stability of the whole deposition process, and then reduces the density of the coating. Arc discharge ion source by gas discharge in uniform magnetic field to draw high density electron flow, in the anode vacuum chamber makes the gas molecule ionization. Arc discharge ion source can be used for cleaning the surface of the sample, but also can increase the sputtering particles and reaction gas energy, improve the film base bonding force, etc. Formed on the basis of high power pulse magnetron sputtering aluminum oxide, with arc discharge ion source can improve the quality of aluminum oxide film as a whole, effectively solve the problem of high power pulse magnetron sputtering discharge instability, has strong practicability.

[0047] The present application is to high power pulse magnetron sputtering to arc discharge ion source bombardment as a cycle, the processing technology at least completes a cycle, so that the ion generated by the arc discharge ion source can form a dense interface layer by bombarding the single layer of aluminum oxide, and effectively improve the overall density of the aluminum oxide coating. The ion generated by the arc discharge ion source can increase the kinetic energy of the deposited atoms on the substrate, improve the density of the coating structure, and also form a dense interface layer to block the diffusion of cracks into the coating. Finally, the high densification of aluminum oxide has excellent performance in high temperature resistance and corrosion resistance.

[0048] The processing is carried out in a periodic step, because the deposition rate of high power pulse magnetron sputtering is low, and if the arc discharge ion source is turned on at the same time, the deposition rate of the coating will be further reduced. The high power pulse magnetron sputtering technology used in the present application can realize the deposition of aluminum oxide in a non-stoichiometric ratio, and can continuously adjust the oxygen content in the coating to realize controllable adjustment of the oxygen content. In the processing technology, by controlling the parameter conditions in the deposition step, the required morphology, structure and non-stoichiometric ratio of the single layer of aluminum oxide can be obtained; by controlling the parameter conditions of the bombardment step, the required interface density of the dense interface layer can be obtained, and finally the high density aluminum oxide coating with different interface densities can be obtained. By adjusting the interface density, the performance of the aluminum oxide in terms of electrical, mechanical, crystallinity and other aspects can be adjusted.

[0049] The high power pulse magnetron sputtering power supply used in the present application is Horting G4002, and the maximum oxygen input (1% to 25%) is changed by adjusting the pulse width (10 to 80 μs). The sputtering power supply adopts frequency control mode.

[0050] The density in the present application refers to the absence of voids and cracks in the cross section of the coating. Further, the coating is cut by a focused ion beam, and the structure of the coating is observed under a transmission electron microscope.

[0051] The specific embodiments of the present application are described in detail below

[0052] Example 1

[0053] The processing technology of the high densification of aluminum oxide coating in this embodiment includes:

[0054] (1) Put the substrate into the vacuum chamber, and vacuumize the vacuum chamber. After the vacuum degree is reduced to 3*10 -3 Pa, heat the vacuum chamber to 200℃;

[0055] Fill argon gas, control the gas pressure at 1 Pa, turn on the pulse bias: control the bias at 500 V, control the frequency at 50 KHz, control the pulse width at 20 μs, clean the substrate, and the cleaning time is 10 min.

[0056] (2) filling in argon and oxygen, the O / Al atomic ratio of the filled oxygen and argon is 0.5, the gas pressure is controlled at 0.2 Pa, the pulse bias is turned on: the bias is controlled at 10 V, the frequency is controlled at 50 KHz, and the pulse width is controlled at 20 μs;

[0057] The aluminum target is sputtered by using a high-power pulse magnetron sputtering power source, the high-power pulse magnetron sputtering power source adopts a frequency control mode, the power is 1 kW, the peak current is 200 A, and the pulse width is 10 μs.

[0058] (3) filling in etching gas argon, the gas pressure is controlled at 0.3 Pa, the aluminum oxide monolayer is bombarded by using an arc discharge ion source, the current is 50 A, the ion energy is 50 eV, the aluminum oxide monolayer is bombarded by using the etching gas, and a dense interface layer is formed on the aluminum oxide monolayer.

[0059] Embodiment 2:

[0060] The processing technology of the high-densification aluminum oxide coating in this embodiment comprises:

[0061] (1) the substrate is placed into a vacuum chamber, the vacuum chamber is vacuumized, and after the vacuum degree is reduced to 2.7*10 -3 Pa, the vacuum chamber is heated to 320 ℃;

[0062] argon is filled in, the gas pressure is controlled at 1.3 Pa, the pulse bias is turned on: the bias is controlled at 750 V, the frequency is controlled at 65 KHz, the pulse width is controlled at 55 μs, the substrate is cleaned, and the cleaning time is 14 min.

[0063] (2) filling in argon and oxygen, the O / Al atomic ratio of the filled oxygen and argon is 0.8, the gas pressure is controlled at 0.5 Pa, the pulse bias is turned on: the bias is controlled at 80 V, the frequency is controlled at 55 KHz, and the pulse width is controlled at 60 μs;

[0064] The aluminum target is sputtered by using a high-power pulse magnetron sputtering power source, the high-power pulse magnetron sputtering power source adopts a frequency control mode, the power is 2.5 kW, the peak current is 300 A, and the pulse width is 60 μs.

[0065] (3) filling in etching gas oxygen, the gas pressure is controlled at 1.8 Pa, the aluminum oxide monolayer is bombarded by using an arc discharge ion source, the current is 75 A, the ion energy is 100 eV, the aluminum oxide monolayer is bombarded by using the etching gas, and a dense interface layer is formed on the aluminum oxide monolayer.

[0066] (4) one cycle is taken as a period of high-power pulse magnetron sputtering to arc discharge ion source bombardment, and the processing technology is completed for 5 cycles.

[0067] Embodiment 3:

[0068] The processing technology of the high-densification aluminum oxide coating in this embodiment comprises:

[0069] (1) Place the substrate into the vacuum chamber and evacuate the chamber until the vacuum level drops to 2.5*10. -3 After Pa, the vacuum chamber is heated to 400°C;

[0070] Argon gas was introduced and the pressure was controlled at 2 Pa. Pulse bias was turned on: bias voltage controlled at 1000 V, frequency controlled at 80 kHz, and pulse width controlled at 100 μs. The substrate was cleaned for 20 min.

[0071] (2) Fill with argon and oxygen. The O / Al atomic ratio of the oxygen and argon is 1.5. The gas pressure is controlled at 1Pa. Turn on the pulse bias: the bias is controlled at 300V, the frequency is controlled at 80KHz, and the pulse width is controlled at 100μs.

[0072] A high-power pulsed magnetron sputtering power supply is used to sputter aluminum targets. The high-power pulsed magnetron sputtering power supply adopts frequency control mode, with a power of 5kW, a peak current of 380A, and a pulse width of 80μs.

[0073] (3) Introduce etching gas nitrogen, control the gas pressure at 2 Pa, and bombard the alumina monolayer with an arc discharge ion source. The current is 100 A and the ion energy is 200 eV. The etching gas bombards the alumina monolayer to form a dense interface layer in the alumina monolayer.

[0074] (4) One cycle is defined as high-power pulsed magnetron sputtering to an arc discharge ion source for bombardment, and the processing technology completes ten cycles.

[0075] Experimental Example 1

[0076] Highly dense alumina was obtained by experiments following the processing procedure of Example 2, and compared with conventional alumina obtained solely by high-power pulsed magnetron sputtering. The results are shown in [Figure 2]. Figure 1 .

[0077] Figure 1 The left image shows an alumina coating prepared by conventional magnetron sputtering, which grows in columnar form with numerous gaps between the columns; Figure 1 The right figure shows the highly dense alumina coating prepared by the processing technology of this invention. The etching process improves the diffusion ability of deposited atoms, and its structural compactness is much higher than that of traditional alumina, which has a good suppression effect on micropores.

[0078] Experimental Example 2

[0079] The density of the highly densified alumina prepared in Example 2 was tested, and the results are shown in [the table below]. Figure 2 .

[0080] from Figure 2As can be seen, the highly dense alumina obtained by this invention has an interfacial spacing of 130 nm, and the crystalline alumina phase is dispersed in the amorphous coating, with no voids or cracks found in the coating. Furthermore, this result indicates that the deposition process of this invention is stable and conducive to the formation of a high-quality coating.

[0081] Experimental Example 3

[0082] Following the processing method of high-density alumina in Example 1, the sputtering voltage was set to 80V and the deposition temperature to 400℃ to prepare high-density alumina. The change in the O / Al atomic ratio in the coating was observed by changing the oxygen flow rate. The results are shown in [Figure 1]. Figure 3 .

[0083] from Figure 3 It can be seen that the oxygen flow rate changes with the O / Al atomic ratio in the coating in a curve. As the oxygen flow rate increases from HD40 to HD140, the O / Al atomic ratio in the coating is between 1.37 and 1.7. The O / Al atomic ratio can be adjusted by controlling the oxygen flow rate.

[0084] Test Example 4

[0085] Following the processing technology of highly dense alumina in Example 3, different alumina coatings were prepared by varying the oxygen flow rate, and their hardness and modulus were measured. Simultaneously, a heat treatment group was set up, and different alumina coatings were heat-treated at 700°C for 2 hours. The hardness and modulus of the different alumina coatings after heat treatment were measured, and the results are shown in […]. Figure 4 . Figure 4 To determine the hardness and modulus of alumina coatings prepared under different oxygen flow rates, Figure 4 (a) is the alumina coating of the present invention. Figure 4 (b) is an alumina coating that has been heat-treated at 700°C for 2 hours.

[0086] from Figure 4 As shown in (a), with increasing oxygen flow rate, the hardness and modulus reach their maximum at 120 sccm, at 11.82 ± 1.12 GPa and 192 ± 12.4 GPa, respectively. The hardness and modulus of the coating reach saturation after the oxygen flow rate exceeds 120 sccm. Figure 4 As can be seen in (b), the hardness and modulus of the coating did not change significantly after heat treatment, indicating that the coating has good structural stability at high temperatures.

[0087] Experimental Example 5

[0088] The high-density alumina prepared in Example 2 and the conventional magnetron sputtered alumina coating were subjected to lead-bismuth corrosion tests. The corrosion conditions were as follows: stainless steel with an alumina coating was immersed in saturated oxygen liquid lead-bismuth at 550°C for 2000 hours. The corrosion results are shown in [Figure number missing]. Figure 5 , Figure 5(1) The corrosion of lead bismuth of traditional magnetron sputtering aluminum oxide coating, Figure 5 (2) The corrosion of lead bismuth of high densification aluminum oxide of the present application.

[0089] It can be seen from Figure 5 The surface of the coating prepared by traditional magnetron sputtering is corroded and a certain amount of the substrate steel is consumed. However, the surface structure of the high densification aluminum oxide coating is still complete after corrosion, which effectively protects the substrate steel from corrosion and exhibits excellent corrosion resistance.

[0090] The above-described specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above-described specific embodiments are merely specific embodiments of the present application and are not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A highly dense alumina coating, characterized in that, The alumina coating, applied to the surface of a high-temperature structural material, comprises at least one alumina monolayer, and each alumina monolayer has a dense interface layer formed by ion bombardment of its surface; the alumina monolayer is composed of AlO₂ in a non-stoichiometric ratio. x Composition, of which oxygen content: 0 <x<1.5; The dense interface layer is obtained by bombardment with an arc discharge ion source. The steps of the arc discharge ion source bombardment include introducing an etching gas with a pressure controlled at 0.3 Pa to 2 Pa, bombarding the alumina monolayer with an arc discharge ion source at a current of 50 A to 100 A and an ion energy of 50 to 200 eV.

2. The highly dense alumina coating according to claim 1, characterized in that, The thickness of the dense interface layer is greater than 0 μm and less than or equal to 2 μm.

3. A processing method for a high-density alumina coating as described in claim 1 or 2, characterized in that, include: Clean the substrate in a vacuum environment; Alumina monolayers were prepared by high-power pulsed magnetron sputtering of an aluminum target using argon as the sputtering gas and oxygen as the reactant gas. An arc discharge ion source is used to bombard the alumina monolayer with etching gas to form a dense interface layer in the alumina monolayer. The processing technology completes at least one cycle, consisting of high-power pulsed magnetron sputtering to an arc discharge ion source for bombardment.

4. The processing technology for the high-density alumina coating according to claim 3, characterized in that, The steps for vacuum cleaning the substrate are as follows: place the substrate into a vacuum chamber, evacuate the chamber, and wait until the vacuum level drops to 3×10⁻⁶. -3 After Pa is below, the vacuum chamber is heated to 200℃~400℃; Argon gas is introduced, and the gas pressure is controlled at 1Pa to 2Pa. Pulse bias is turned on: bias voltage is controlled at 500V to 1000V, frequency is controlled at 50KHz to 80KHz, and pulse width is controlled at 20μs to 100μs.

5. The processing technology for the high-density alumina coating according to claim 4, characterized in that, The substrate cleaning time is 10 min to 20 min.

6. The processing technology for the high-density alumina coating according to claim 3, characterized in that, The steps for high-power pulsed magnetron sputtering are as follows: argon and oxygen are introduced, the gas pressure is controlled at 0.2Pa to 1Pa, and the pulse bias is turned on: the bias is controlled at 0 to 300V, the frequency is controlled at 50KHz to 80KHz, and the pulse width is controlled at 20μs to 100μs. A high-power pulsed magnetron sputtering power supply is used to sputter aluminum targets.

7. The processing technology for the high-density alumina coating according to claim 3 or 6, characterized in that, The O / Ar atomic ratio of the oxygen and argon gas introduced is 1.37 to 1.

7.

8. The processing technology for the high-density alumina coating according to claim 6, characterized in that, The high-power pulsed magnetron sputtering power supply adopts a frequency control mode, with a power of 1kW to 5kW, a peak current of 200A to 380A, and a pulse width of 10μs to 80μs.

9. The processing technology for the high-density alumina coating according to claim 3, characterized in that, The etching gas includes argon, oxygen, or nitrogen.

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