High-temperature stable multi-component alloy film getter and preparation method thereof

Abstract

The invention relates to the field of getter alloys, and discloses a high-temperature stable multi-component alloy film getter and a preparation method thereof.The film getter is deposited on a metal matrix and sequentially comprises a diffusion barrier layer, a first metal layer, a second metal layer, a third metal layer and a fourth metal layer from the matrix to the top, the thermal expansion coefficient gradient transition layer is made of chromium-zirconium alloy, pure zirconium or a combination of the chromium-zirconium alloy and the pure zirconium, and the thermal expansion coefficient of the gradient transition layer is between the thermal expansion coefficient of the diffusion barrier layer and the thermal expansion coefficient of the air suction functional layer; the air suction functional layer is made of zirconium-based multi-component alloy; the diffusion barrier layer is used for inhibiting mutual diffusion of matrix elements and elements of the air suction functional layer at high temperature, and the gradient transition layer is used for relieving thermal stress generated by mismatch of thermal expansion coefficients. A multi-layer gradient transition structure is designed, the phenomena of cracking, bubbling and stripping of the film layer in the high-temperature thermal cycle process are effectively avoided, and excellent thermal shock resistance is shown.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of getter alloys, in particular to a high-temperature stable multi-element alloy thin film getter and a preparation method thereof. BACKGROUND

[0002] Non-evaporable getters are the core and key materials in modern vacuum electronic devices, such as X-ray tubes, traveling wave tubes, magnetrons, particle accelerators, and vacuum insulation devices. The working principle is that the material surface and its bulk phase can effectively capture and fix active gas molecules through chemical adsorption and diffusion adsorption, thereby maintaining and improving the internal vacuum degree of the device after sealing, and ensuring the performance, reliability and service life of the device.

[0003] With the rapid development of cutting-edge technology fields such as aerospace, nuclear energy, and high-energy physics, related vacuum devices are evolving towards miniaturization, high power, and high reliability. This puts forward more stringent requirements for internal getters: the heat generated during device operation or external high-temperature environment requires the getter to work stably at high temperature for a long time and maintain excellent gettering performance.

[0004] At present, the widely used non-evaporable getters are mainly zirconium-based multi-element alloys, such as the mature Zr-V-Fe series getters. These materials have excellent initial gettering performance at medium temperatures. However, when they are used at high temperatures for a long time, their performance will significantly decrease. SUMMARY

[0005] The main purpose of the present application is to solve the technical problem that the performance of the existing getter film significantly decreases when it is used at high temperature for a long time. A high-temperature stable multi-element alloy thin film getter is deposited on a metal substrate, and the getter film includes, from the substrate upwards: a diffusion barrier layer made of chromium or chromium alloy; a thermal expansion coefficient gradient transition layer made of chromium-zirconium alloy, pure zirconium or a combination thereof, the thermal expansion coefficient of the gradient transition layer being between that of the diffusion barrier layer and the getter functional layer; a getter functional layer made of zirconium-based multi-element alloy; The diffusion barrier layer is used to inhibit the interdiffusion of the base elements and the getter functional layer elements at high temperature, and the gradient transition layer is used to relieve the thermal stress caused by the mismatch of the thermal expansion coefficients.

[0006] The second aspect of the present application provides a preparation method of a high-temperature stable multi-element alloy thin film getter, comprising: The method comprises: depositing the following metal layers on the substrate: a 100-200 nanometer pure chromium layer; 300-400 nm of Zr-Cr alloy layer; 200-500 nm of pure zirconium layer; 800-2000 nm of a gettering alloy layer.

[0007] The present application has the following beneficial effects: The present application designs a multi-layer gradient transition structure, which realizes a smooth and continuous transition of the thermal expansion coefficient from the metal substrate to the ceramic functional layer. The design greatly relieves the concentrated thermal stress at the film-substrate interface due to the CTE mismatch, effectively avoids the cracking, bubbling and peeling of the film layer during high-temperature thermal cycling, and shows excellent thermal shock resistance.

[0008] The pure Cr bonding layer of the present application not only has a strong adhesion to the commonly used substrate such as stainless steel, but more importantly, it acts as an efficient diffusion barrier wall, effectively blocking the diffusion of the substrate elements to the functional layer and the penetration of the functional layer elements to the substrate, completely inhibiting the formation of brittle intermetallic compounds at the interface, ensuring the stability of the chemical composition and mechanical properties of the interface region after high-temperature aging, and making the film-substrate bonding force durable and reliable.

[0009] The present application designs an ultra-thin Y protective layer, which can spontaneously form a dense oxide film in the air to prevent the internal active components from being deeply oxidized; when activated in vacuum, the oxide film can be reduced by Zr to expose a fresh and active surface, realizing the perfect unity of easy activation and storage stability, and ensuring the complete release of the getter performance before the device is sealed off. DETAILED DESCRIPTION

[0010] The terms “first”, “second”, “third”, “fourth” and the like in the specification and claims of the present application, if any, are used to distinguish similar objects, and do not necessarily have to describe a particular order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances. In addition, the terms “include” or “have” and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0011] For the sake of understanding, the specific process of the embodiments of the present application is described below. The first embodiment of a high-temperature stable multi-element alloy thin film getter of the embodiments of the present application includes: The thin film getter is deposited on a metal substrate, which includes, in order from the substrate upwards: A diffusion barrier layer made of chromium or chromium alloy; a thermal expansion coefficient gradient transition layer, which is made of chromium-zirconium alloy, pure zirconium or a combination thereof, and has a thermal expansion coefficient between the diffusion barrier layer and the getter functional layer; a getter functional layer, which is made of zirconium-based multi-element alloy; The diffusion barrier layer is used to inhibit the interdiffusion of base elements and getter functional layer elements at high temperature, and the gradient transition layer is used to relieve thermal stress caused by mismatch of thermal expansion coefficients.

[0012] As an optional technical solution, the diffusion barrier layer is a pure chromium layer with a thickness of 100-200 nanometers. As an optional technical solution, the thermal expansion coefficient gradient transition layer is composed of a 300-400 nanometer Zr-Cr alloy layer, a 200-500 nanometer pure zirconium layer, and a 200-500 nanometer pure zirconium layer. As an optional technical solution, the pure zirconium layer is an α-Zr columnar crystal layer.

[0013] As an optional technical solution, the thin film getter further includes a 20-50 nanometer surface protection layer located at the outermost layer of the thin film getter. As an optional technical solution, the surface protection layer is pure yttrium or yttrium-rich alloy.

[0014] As an optional technical solution, the composition of the Zr-Cr alloy layer is Zr 20-40 Cr 60-80 .

[0015] As an optional technical solution, the composition of the getter functional layer is yttrium-containing getter alloy. As an optional technical solution, the composition of the getter functional layer is Zr 50-60 V 25-35 Fe 5-10 Y 3-5 .

[0016] The scheme of the present application is as follows: Layer 1, transition bonding layer composed of pure chromium, which solves the problem of interface bonding and interdiffusion. The designed Cr has excellent compatibility and adhesion with the stainless steel substrate, and can effectively block the diffusion of subsequent elements (such as Zr) to the substrate, preventing the formation of brittle phases.

[0017] Layer 2, stress buffer layer 1 composed of Zr-Cr alloy, as an optional, for example: Zr70Cr30, this layer has a CTE between Cr and pure Zr, which can effectively gradient transition thermal stress and avoid sharp changes in stress.

[0018] Layer 3, stress buffer layer 2 / getter functional base layer Zr, consisting of pure zirconium, provides the base of the main gettering capability and further buffers the stress. Zr is an excellent gettering element and its CTE matches perfectly with the upper functional layers. As preferred, this layer is deposited as a dense, ductile, alpha-Zr columnar grain layer.

[0019] 4th layer core gettering functional layer The optional alloy can be Zr-V-Fe-Y multicomponent alloy, or other specific gettering alloy. The goal of this layer is to achieve high temperature stable gettering. The addition of Y refines the grain and improves the creep resistance of the alloy, thus maintaining the microstructure stable at high temperature and ensuring the long term gettering performance.

[0020] 5th layer surface protection / activation layer This layer consists of pure yttrium (Y) or yttrium-rich alloy, which acts as a protection and self-sacrifice, ultra-thin layer. In the air, Y will preferentially form a dense Y2O3 protective film to prevent deep oxidation of the internal Zr. When activated at high temperature in vacuum, Y2O3 is easily reduced by Zr, exposing a fresh active surface, while the Y element diffuses into the functional layer, replenishing its content.

[0021] 1. Experimental comparison of multi-layer structure: On 304 stainless steel substrates, a variety of thin film structures were prepared using magnetron sputtering technology: Single layer control group (Comparative Example 1): Zr-V-Fe thin film Single layer experimental group (Comparative Example 2): Zr-V-Fe-Y thin film Multi-layer experimental group (Example 1): Cr / Zr / Zr-V-Fe-Y / Y gradient functional thin film.

[0022] Multi-layer experimental group (Example 2): Cr / Zr-V-Fe-Y / Y gradient functional thin film.

[0023] Multi-layer experimental group (Example 3): Zr / Zr-V-Fe-Y / Y gradient functional thin film.

[0024] Multi-layer experimental group (Example 4): Zr-Cr / Zr-V-Fe-Y / Y gradient functional thin film.

[0025] Multi-layer experimental group (Example 5): Ti / Zr-V-Fe-Y / Y gradient functional thin film.

[0026] Multi-layer experimental group (Example 6): V-Cr / Zr-V-Fe-Y / Y gradient functional thin film.

[0027] Multi-layer experimental group (Example 7): Zr-V-Fe-Y / Y gradient functional thin film.

[0028] Multi-layer experimental group (Example 8): Cr / Zr-Cr / Zr / Zr-V-Fe-Y gradient functional thin film.

[0029] Multi-layer experimental group (Example 9): Cr / Zr-Cr / Zr / Zr-V-Fe-Y / Y gradient functional thin film.

[0030] The thickness of Cr, Zr, Ti, Zr-Cr, V-Cr is controlled at 200 nanometers; the thickness of Zr-V-Fe-Y is controlled at 1000 nanometers, and the thickness of Y layer is controlled at 30 nanometers.

[0031] 2. Surface protective layer experiment comparison On the 304 stainless steel substrate, a variety of thin film structures were prepared by magnetron sputtering technology, as shown in Table 1: Table 1 Specific preparation method 1. Substrate and target material: Substrate: 304 stainless steel sheet (20mm × 20mm × 0.5mm) Target material (purity > 99.9%), composition as described in the foregoing section.

[0032] 2. Equipment: Ultrasonic cleaning machine Magnetron sputtering system: equipped with at least 4 radio frequency (RF) target positions, with substrate heating, rotation and baffle switching functions, vacuum ≤ 5.0×10 -5 Pa.

[0033] High vacuum annealing furnace: maximum temperature ≥ 1000°C, vacuum degree ≤ 1.0×10⁻ 3 Pa.

[0034] Phase 1: Substrate pretreatment Polishing: polish the stainless steel sheet to 2000# with sandpaper, then use diamond polishing paste for mechanical polishing to obtain a smooth surface.

[0035] Ultrasonic cleaning: ultrasonic cleaning in acetone, anhydrous ethanol and deionized water for 15 minutes each.

[0036] Drying and storage: dry with high-purity nitrogen and immediately place the sample on the sample holder in the sputtering chamber.

[0037] Phase 2: Thin film preparation (magnetron sputtering) Parameters: The base vacuum is pumped to ≤ 5.0×10⁻ 5Pa, working gas is high purity Ar (99.999%), working pressure is set to 0.5 Pa, substrate rotation speed is 20 rpm, and the substrate is heated to 300°C.

[0038] Before depositing each layer, the corresponding target is pre-sputtered for 10 minutes to clean the surface.

[0039] Evaluation method: High temperature aging treatment Put all the deposited samples into a high vacuum annealing furnace. Vacuumize to ≤ 1.0×10⁻ 3 Pa. Perform the following heat treatment program: heat to 800°C at a rate of 10°C / min. Keep at 800°C for 48 hours. After the program ends, cool to room temperature with the furnace.

[0040] Performance test and characterization Mechanical property test (after aging): Thermal shock experiment: keep the sample in an 800°C muffle furnace for 5 minutes, then quickly drop it into room temperature deionized water for quenching. After 10 cycles, observe the surface cracks and peeling.

[0041] Gas absorption performance test (after aging): Put the sample into a custom test system and vacuumize to high vacuum (≤ 10⁻ 6 Pa). Re-activation: heat the sample at 800°C for 30 minutes to reduce the surface oxide and obtain a fresh active surface. Cool the system to 400°C. Inject high purity H2 gas into the system, with an initial pressure set to 100 Pa. Use QMS and pressure sensor to monitor and record the gas partial pressure change curve P(t) in the cavity over time in real time, continuously monitor until the pressure is basically unchanged, calculate the initial absorption rate cm 3 ·s⁻ 1 ·cm⁻ 2 and the saturated absorption amount L·Pa·g⁻ 1 .

[0042] The experimental results are shown in Table 2.

[0043] Table 2 Example 8 has no Y protective layer, and the surface is slightly oxidized during the aging activation process, resulting in a slightly lower initial rate than the level corresponding to its saturated capacity.

[0044] Example 3 and Example 4 as transition layer, the effect is better than the embodiment 7 without transition layer, but not as good as the embodiment 9 containing pure Zr and Zr-Cr double transition layer. This shows that the step gradient (Cr -> Zr-Cr -> Zr) can more effectively relieve thermal stress than a single transition layer.

[0045] Example 5 and Example 6 as binding / transition layer, the effect is obviously not as good as Example 1 and Example 4, it can be seen that the material combination of selecting Cr as diffusion barrier layer and Zr-based alloy as transition layer has unexpected superiority.

[0046] The above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A high-temperature stable multi-element alloy thin-film getter, characterized in that, The thin-film getter is deposited on a metal substrate, characterized in that, from the substrate upwards, it comprises: A diffusion barrier layer, the material of which is chromium or chromium alloy; A gradient transition layer with a thermal expansion coefficient, the material of which is selected from chromium-zirconium alloy, pure zirconium or a combination thereof, wherein the thermal expansion coefficient of the gradient transition layer is between that of the diffusion barrier layer and the gas-absorbing functional layer; One air-absorbing functional layer is made of zirconium-based multi-element alloy; The diffusion barrier layer is used to suppress the interdiffusion between the matrix elements and the getter functional layer elements at high temperatures, and the gradient transition layer is used to alleviate the thermal stress caused by the mismatch of thermal expansion coefficients.

2. The high-temperature stable multi-element alloy thin-film getter according to claim 1, characterized in that, The diffusion barrier layer is a pure chromium layer of 100-200 nanometers.

3. The high-temperature stable multi-element alloy thin-film getter according to claim 1, characterized in that, The gradient transition layer of thermal expansion coefficient is composed of a Zr-Cr alloy layer of 300-400 nm, a pure zirconium layer of 200-500 nm, and a pure zirconium layer of 200-500 nm.

4. The high-temperature stable multi-element alloy thin-film getter according to claim 1, characterized in that, Thin-film getters also include a 20-50 nanometer surface protective layer located on the outermost layer of the thin-film getter.

5. The high-temperature stable multi-alloy thin-film getter according to claim 3, characterized in that, The pure zirconium layer is an α-Zr columnar crystal layer.

6. The high-temperature stable multi-element alloy thin-film getter according to claim 3, characterized in that, The Zr-Cr alloy layer is composed of Zr. 20-40 Cr 60-80 .

7. The high-temperature stable multi-alloy thin-film getter according to claim 1, characterized in that, The gas-getting functional layer is composed of a yttrium-containing gas-getting alloy.

8. The high-temperature stable multi-element alloy thin-film getter according to claim 1, characterized in that, The component of the inhalation functional layer is Zr. 50-60 V 25-35 Fe 5-10 Y 3-5 .

9. A high-temperature stable multi-element alloy thin-film getter according to claim 4, characterized in that, The surface protective layer is pure yttrium or a yttrium-rich alloy.

10. The method for preparing a high-temperature stable multi-element alloy thin film getter according to claim 1, characterized in that, The method includes: Deposit the following metal layer on the substrate: A pure chromium layer of 100-200 nanometers; A 300-400 nm Zr-Cr alloy layer; A pure zirconium layer of 200-500 nanometers; 800-2000 nanometers of getter alloy layer.

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