High-hardness and high-temperature-resistant AlCrN piezoelectric coating material as well as preparation and application thereof

Abstract

The invention provides a high-hardness and high-temperature-resistant AlCrN piezoelectric coating material as well as preparation and application thereof, and relates to the technical field of piezoelectric film materials. The preparation method of the AlCrN piezoelectric coating material comprises the steps that an alloy target material composed of Al and Cr is adopted, the content of Al is higher than 70%, the content of Cr is smaller than 30%, and an AlCrN hard piezoelectric coating is formed on the surface of a base body through magnetron sputtering; the AlCrN hard piezoelectric coating grows in various orientations in the deposition process by controlling the gas flow ratio of argon to nitrogen, the temperature, the sputtering power, the deposition air pressure and the target-substrate distance in magnetron sputtering. The prepared AlCrN piezoelectric coating material has good mechanical properties, temperature resistance and corrosion resistance, longitudinal waves, longitudinal waves, transverse waves and transverse waves can be excited at the same time to achieve defect detection and stress measurement of steel plates, weld joints and steel pipes in various media when the coating material is deposited on a base body, and on the premise that a protective layer is not needed, the thickness of the coating material is reduced, and the cost is reduced. And the long-term stable service capacity is achieved under the high-temperature and severe working conditions, the long-term use requirement is met, batch production is easy, and application and popularization prospects are achieved.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric thin film materials technology, and particularly to AlCrN piezoelectric coating materials with high hardness and high temperature resistance, as well as their preparation and application. Background Technology

[0002] Ultrasonic testing, with its advantages of convenience, speed, and non-harm to the human body, has become one of the most important methods for inspecting and testing special equipment. Ultrasonic sensors are widely used in defect detection, stress measurement, thickness measurement, and bolt axial force measurement. Taking bolt stress measurement as an example, according to the principle of acoustoelasticity, the propagation speed of ultrasonic waves in a bolt is related to the bolt stress. By observing the propagation time of ultrasonic waves in the bolt, a functional relationship between the ultrasonic wave propagation time and the bolt axial stress is established. Through calibration experiments, the correlation coefficient in the functional relationship is obtained. Therefore, the bolt stress value can be quantitatively measured by measuring the propagation time of ultrasonic waves in the bolt, thereby judging the health condition of the bolted connection.

[0003] Existing ultrasonic sensors are mainly suitable for ambient temperature environments (<100°C). With the increasing demand for high-parameterization in high-temperature and high-pressure special equipment, ultrasonic detection under high-temperature conditions is gaining attention, necessitating the development of high-temperature resistant ultrasonic sensors. A key challenge in developing ultrasonic sensors for high-temperature conditions is the Curie temperature limitation of piezoelectric wafers. Traditional PZT (lead zirconate titanate) materials have low Curie temperatures, making them unsuitable for use as piezoelectric wafers in high-temperature probes. Existing high-temperature piezoelectric films are prone to cracking and detachment from the substrate during repeated high and low temperature changes and long-term use. Therefore, improving the bonding force between the piezoelectric film and the substrate material is crucial for stable sensor operation.

[0004] Currently, the main piezoelectric materials that can be used to generate ultrasonic waves are ZnO and AlN. Both of these materials have a hexagonal wurtzite structure, and their piezoelectric effect depends entirely on their crystal orientation without polarization. ZnO films have higher conductivity; however, their low processing temperature and poor resistance to acid and alkali corrosion make them difficult to use for extended periods in high-temperature, acidic, alkaline, or inorganic salt environments, which severely limits the application of ZnO-based piezoelectric films.

[0005] AlN thin films possess very high Curie temperatures (over 2000°C) and can maintain their usable piezoelectric properties in Ar up to 1150°C. They also exhibit excellent physical and chemical stability, displaying a fairly wide operating bandwidth as thin-film piezoelectric transducers at atmospheric temperatures exceeding 700°C. The surface acoustic wave propagation speed of AlN-based devices is significantly higher than that of ZnO-based devices. The elastic constant of AlN-based devices is also much higher than that of ZnO-based devices, resulting in lower transmission losses. The piezoelectric coefficient of AlN is 1 / 1 that of PZT, while its dielectric constant is less than one percent of that of PZT. This results in improved signal-to-noise ratios for AlN thin-film devices compared to those using PZT thin films. Among all its properties, AlN's high acoustic velocity makes it the material of choice for thin-film-based high-frequency acoustic devices, used in mobile phones, alarm and security systems, military equipment, sensors, and more. AlN exhibits high stability in harsh environments, leading to better sensor performance. Therefore, compared with ZnO-based devices, the use of AlN thin films has promoted the development of acoustic devices, which can operate at higher frequencies, temperatures and harsher environments, and have higher sensitivity.

[0006] Although the piezoelectric modulus of pure AlN thin films is very low (d 33=5.5 pC / N), but this can be improved by adding one or more doping elements. Most notably, Akiyama et al. (Akiyama, Morito, et al. "Enhancement of piezoelectric response in scandium aluminum nitride alloy thin films prepared by dual reactive cosputtering." Advanced Materials 21.5 (2009): 593-596.) found that when doped with scandium (Sc), the d33 modulus in sputtered deposited AlN films can be increased by nearly 500%. Subsequent research (Startt, J., Quazi, M., Sharma, P., Vazquez, I., Poudyal, A., Jackson, N., & Dingreville, R. (2023). Unlocking AlN piezoelectric performance with earth‐abundant dopants. Advanced Electronic Materials, 9(4), 2201187.) found that other rare earth elements such as yttrium (Y) and ytterbium (Yb) can also enhance the piezoelectric performance of AlN-based thin films. However, two factors limit the doping of these metals: first, rare earth sputtering targets (such as Sc and Yb) are expensive; and second, the stability of the prepared thin film material decreases with increasing concentration of these dopants. Therefore, there is an urgent need to develop an AlN thin film with widely available and relatively low-cost metal raw materials and higher piezoelectric performance. Summary of the Invention

[0007] Addressing the shortcomings of existing AlN thin-film piezoelectric materials, this invention provides a high-hardness, high-temperature-resistant AlCrN piezoelectric coating material, its preparation, and its applications. This AlCrN piezoelectric coating material simultaneously possesses high hardness, high temperature resistance, and high corrosion resistance, exhibits strong adhesion to the substrate, and can generate different types (transverse / longitudinal waves) of ultrasonic waves according to application requirements. Ultrasonic sensors prepared using this material can not only achieve high-precision and high-efficiency measurement of bolt preload, but also effectively measure defects and stress in substrates such as steel plates, welds, and steel pipes. Specifically, this is achieved through the following techniques.

[0008] This invention provides a method for preparing a high-hardness, high-temperature-resistant AlCrN piezoelectric coating material, which uses an AlCr alloy target and forms an AlCrN piezoelectric coating on the substrate surface by magnetron sputtering.

[0009] The AlCr alloy target is composed of 75-96 at% Al and 4-25 at% Cr. Here, at% refers to atomic percentage.

[0010] Furthermore, the AlCr alloy target is composed of 96 at% Al and 4 at% Cr, or 92 at% Al and 8 at% Cr.

[0011] Furthermore, the magnetron sputtering method is as follows: the temperature is 60-250℃, the gas flow rate ratio of argon and nitrogen is (1-81):9, the sputtering power is 700-900 W, the deposition pressure is P=0.6-3.0 Pa, the target-substrate distance is d=40-80 mm, and the deposition time is 3-15 h.

[0012] Furthermore, the temperature for magnetron sputtering is 150-250℃.

[0013] Furthermore, a vacuum process is performed before magnetron sputtering to ensure that the vacuum level in the vacuum chamber does not exceed 7 × 10⁻⁶. -3 Pa.

[0014] Furthermore, the substrate is subjected to surface plasma etching prior to magnetron sputtering.

[0015] Furthermore, the surface plasma etching is performed in an argon atmosphere at 60-250℃ and 0.5-2.0 Pa, with a duty cycle of 30-80%, a current of 70-110 A, a bias voltage of -100~-200 V, and an etching time of 0.5-2 h.

[0016] Furthermore, a protective layer is deposited on the surface of the AlCrN piezoelectric coating.

[0017] Alternatively, the protective layer may be made of one of the following materials: silicon dioxide (SiO2), silicon nitride (Si3N4), and high-entropy alloy oxides (such as AlCrNbSiTiO alloy, AlCrNbSiTiTaYO alloy, etc.).

[0018] Furthermore, the method for depositing the protective layer is as follows: SiO2 and / or high-entropy alloy oxide are deposited under a vacuum of 1-3 Pa and a power of 600-800 W to form the protective layer.

[0019] Furthermore, an Ag or AgCr electrode layer is deposited on the surface of the protective layer. The electrode layer provides an external electrode for the bolt, allowing a stable voltage to be applied to both poles of the bolt, thereby exciting ultrasonic waves.

[0020] Furthermore, the electrode layer is deposited under the following conditions: under an argon atmosphere, an ambient pressure of 0.25-1 Pa, a bias voltage of 0 to -100 V, a deposition temperature of room temperature to 250°C, a sputtering distance of 40-80 mm, and a sputtering power of 500-800 W, for 0.5-4 h.

[0021] Furthermore, the alloy target has a diameter of 140-160 mm and a thickness of 4-8 mm. In this invention, there is a certain correlation between the target diameter, thickness, and magnetron sputtering power. This application uses a larger diameter target in combination with higher sputtering power, enabling the simultaneous preparation of more samples during coating deposition, resulting in higher deposition efficiency; it is also easier to mass-produce and more readily applicable.

[0022] Furthermore, the thickness of the AlCrN piezoelectric coating is 5-20 μm. In conventional methods, the doping of Cr in AlCrN hard piezoelectric coatings significantly increases the stress of the AlN coating. When the piezoelectric coating is too thick, it easily leads to cracking and peeling, causing the piezoelectric coating to fail. Therefore, the thickness of AlCrN piezoelectric coatings prepared using conventional methods needs to be strictly controlled (typically <5 μm). This invention, by optimizing various parameters in the preparation method, not only improves the hardness and wear resistance of the AlCrN piezoelectric coating itself, but also significantly enhances the adhesion between the piezoelectric coating and the substrate, meeting the requirements for preparing thicker AlCrN piezoelectric coatings. This results in superior ultrasonic performance with a larger amplitude.

[0023] In the above preparation method, an AlCrN hard piezoelectric coating is prepared using radio frequency magnetron sputtering. The sputtering temperature is controlled between 60-250℃, within which Al, Cr, and N particles have sufficient energy to migrate to the substrate surface and deposit the AlCrN coating. Controlling the flow rate ratio of argon and nitrogen allows control over the atomic percentages of Al, Cr, and N particles in the vacuum chamber of the magnetron sputtering equipment, thus adjusting the collision probability between Al, Cr, and N particles and regulating the growth orientation of the coating. Using a sputtering power of 700-900 W allows adjustment of the energy levels of Al, Cr, and N particles, controlling the coating thickness. Controlling the sputtering deposition pressure (pressure after introducing the reactive gas into the vacuum chamber) to 0.6-3.0 Pa and the target-substrate distance (vertical distance between the target and the substrate) to 40-80 mm allows for adjustment of the mean free path of Al, Cr, and N particles, enabling the preparation of AlCrN coatings with various orientations within this deposition range. Ultimately, the preparation of an AlCrN piezoelectric coating with high hardness, high wear resistance, high corrosion resistance, and strong adhesion to the substrate was achieved.

[0024] The present invention also provides a high-hardness, high-temperature-resistant AlCrN piezoelectric coating material prepared by any of the above preparation methods.

[0025] The AlCrN piezoelectric coating material prepared by this invention has growth orientations on the substrate surface including (002) diffraction crystal planes, (102) diffraction crystal planes, or (103) diffraction crystal planes. Research has shown that by adjusting the deposition parameters during magnetron sputtering, including deposition pressure, target-substrate distance, and deposition time, the AlCrN hard piezoelectric coating can exhibit multiple growth orientations on the substrate surface, enabling the excitation of various ultrasonic waveforms, including a combined longitudinal and transverse wave. This allows for the preparation of AlCrN piezoelectric coating materials capable of exciting ultrasonic waves of different waveforms according to detection requirements.

[0026] The present invention also provides a high-hardness and high-temperature-resistant AlCrN piezoelectric coating material prepared by any of the above preparation methods, which is used in bolt preload testing, or in defect detection and stress measurement of steel plates, welds, and steel pipes.

[0027] This invention, through extensive research, demonstrates that when using a combined transverse and longitudinal wave method to detect stress in steel plates, welds, and steel pipes, aside from constants related to material properties and geometry, only the flight time and initial temperature of the longitudinal and transverse waves under no-load conditions need to be measured. By simultaneously solving an eighth-order polynomial, the real-time load on the bolt can be obtained without calibrating the original stress. This method reduces the number of compensation factors, simplifies the detection process, minimizes errors in the conversion calculation between ultrasonic signals and stress, and improves measurement accuracy.

[0028] In some practical applications, the substrate for the AlCrN piezoelectric coating material can be a smart bolt. Following the preparation method provided by this invention, an AlCrN hard piezoelectric coating, a protective layer, and an electrode layer are sequentially deposited on the surface of the smart bolt. Based on the specific requirements of bolt preload measurement, relevant parameters of the AlCrN piezoelectric coating material during the preparation process are adjusted to enable the smart bolt with the piezoelectric coating material to generate different waveforms (longitudinal waves, transverse waves, or both). These features simplify the bolt preload calculation process, improve measurement accuracy, and the piezoelectric coating of the smart bolt has advantages such as high mechanical properties, good temperature resistance, and stronger adhesion to the bolt substrate, which can broaden its operating temperature range and extend the service life of the smart bolt.

[0029] Compared with the prior art, the advantages of the present invention are:

[0030] 1. The method for preparing AlCrN piezoelectric coating provided by the present invention utilizes radio frequency magnetron sputtering to prepare AlCrN piezoelectric coating on the substrate surface. By adjusting different gas pressures and target-substrate distances, piezoelectric coating materials that can simultaneously generate different waveforms can be obtained to achieve accurate measurement of bolt preload.

[0031] 2. The AlCrN piezoelectric coating obtained by this invention possesses excellent properties such as high hardness, high wear resistance, and high corrosion resistance. This ensures long-term stable operation of the piezoelectric coating on the surfaces of various alloy bolts, reducing the possibility of failure and meeting the application and testing requirements under harsh working conditions. The final coating material has a hardness of 15-35 GPa, a bonding strength with the substrate greater than 10 MPa, and an operating temperature range of -196 to 700℃.

[0032] 3. The AlCrN piezoelectric coating material provided by this invention serves as an acoustic-electric conversion layer for exciting ultrasound, enabling non-destructive testing; it can also emit longitudinal and transverse waves simultaneously under excitation, achieving high-precision (error < 5%) and high-efficiency measurement of bolt preload.

[0033] 4. The AlCrN piezoelectric coating obtained by this invention does not require an additional protective layer. The preparation process of the AlCrN piezoelectric coating is simple, easy to mass-produce industrially, has high processing efficiency, and low production cost. Attached Figure Description

[0034] Figure 1 The image shows the XRD patterns of the AlCrN piezoelectric coatings obtained in Example 2 under different argon-nitrogen ratios.

[0035] Figure 2 The XRD patterns of the AlCrN piezoelectric coatings obtained in Example 9 under different argon-nitrogen ratios are shown.

[0036] Figure 3 The image shows the XRD pattern of the AlCrN piezoelectric coating obtained in Comparative Example 1.

[0037] Figure 4 The image shows the SEM images of the AlCrN piezoelectric coatings obtained in Example 9 under different argon-nitrogen ratios after a tribological test.

[0038] Figure 5 The image shows the nanohardness of the AlCrN piezoelectric coatings obtained in Example 2 under different argon-nitrogen ratios.

[0039] Figure 6 The image shows the ultrasonic signal of the AlCrN piezoelectric coating obtained under different argon-nitrogen ratios in Example 2.

[0040] Figure 7The ultrasonic patterns of the AlCrN piezoelectric coating obtained in Example 9 under an argon-nitrogen gas flow ratio of 1:1, after annealing at 700°C for different times.

[0041] Figure 8 The graph shows the elemental content changes of the AlCrN piezoelectric coatings prepared in Examples 2 and 9 under an argon-nitrogen flow rate ratio of 1:1. Detailed Implementation

[0042] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] In the embodiments provided by this invention, the method for preparing a high-hardness and high-temperature-resistant AlCrN piezoelectric coating material involves using an AlCr alloy target and forming an AlCrN piezoelectric coating on the substrate surface by magnetron sputtering.

[0044] The AlCr alloy target is composed of 75-96 at% Al and 4-25 at% Cr.

[0045] Optionally, the magnetron sputtering method is as follows: the temperature is 60-250℃, the gas flow rate ratio of argon and nitrogen is (1-81):9, the sputtering power is 700-900 W, the deposition pressure is P=0.6-3.0 Pa, the target-substrate distance is d=40-80 mm, and the deposition time is 3-15 h.

[0046] Optionally, the temperature of magnetron sputtering is 150-250℃.

[0047] Optionally, a vacuum process is performed before magnetron sputtering to ensure that the vacuum level in the vacuum chamber does not exceed 7 × 10⁻⁶. -3 Pa.

[0048] Optionally, the substrate is subjected to surface plasma etching prior to magnetron sputtering.

[0049] Specifically, surface plasma etching is performed in an argon atmosphere at 60-250℃ and 0.5-2.0 Pa, with a duty cycle of 30-80%, a current of 70-110 A, a bias voltage of -100~-200 V, and an etching time of 0.5-2 h.

[0050] Optionally, a protective layer is also deposited on the surface of the AlCrN piezoelectric coating. The protective layer may be made of one of the following materials: silicon dioxide (SiO2), silicon nitride (Si3N4), or high-entropy alloy oxides.

[0051] Specifically, the method for depositing the protective layer is as follows: SiO2 and / or high-entropy alloy oxides are deposited under a vacuum of 1-3 Pa and a power of 600-800 W to form the protective layer.

[0052] Optionally, an electrode layer is also deposited on the surface of the protective layer, and the electrode layer is made of a material selected from Ag, Ag-Cr, etc.

[0053] Specifically, the method for depositing the electrode layer is as follows: depositing the electrode layer under the conditions of a vacuum degree of 0.25-1 Pa, a bias voltage of 0 to -100 V, and a current of 0 to 100 A.

[0054] Optionally, the alloy target has a diameter of 140-160 mm and a thickness of 4-8 mm.

[0055] Optionally, the thickness of the AlCrN piezoelectric coating is 5-20 μm.

[0056] The method for preparing the AlCrN piezoelectric coating provided by this invention may specifically include the following steps:

[0057] S1. In an argon atmosphere at 60-250℃ and an Ar atmosphere at 0.5-2.0 Pa, with a duty cycle of 30-80%, a current of 70-110 A, a bias voltage of -100 to -200 V, and an etching time of 0.5-2 h. S2. Using an alloy target composed of Al and Cr, an AlCrN hard piezoelectric coating is deposited on the etched surface by magnetron sputtering; the alloy target consists of 75-96 at% Al and 4-25 at% Cr.

[0058] S3. Deposit a protective layer (SiO2 or high-entropy alloy oxide) on the surface of AlCrN piezoelectric coating under the conditions of 1-3 Pa and 500-700 W power.

[0059] S4. Under an argon atmosphere, with an ambient pressure of 0.25-1 Pa, a bias voltage of 0 to -100 V, a deposition temperature of room temperature to 250℃, a sputtering distance of 40-80 mm, and a sputtering power of 500-800 W, an electrode layer is deposited on the surface of the protective layer for 0.5-4 h, thus completing the preparation of the AlCrN piezoelectric coating material.

[0060] Example 1

[0061] The AlCrN piezoelectric coating provided in this embodiment uses stainless steel and Si wafers as substrates, and the specific preparation method is as follows:

[0062] S1. At 150℃, in an argon atmosphere, with a pressure of 1.0 Pa, a current of 100 A, a duty cycle of 50%, a bias voltage of -150 V, and an etching time of 1 h, plasma etching is performed on the substrate surface to remove impurities attached to the substrate surface.

[0063] S2. Adjust the vacuum chamber temperature of the magnetron sputtering equipment to 150℃, and first evacuate to a vacuum level of 3×10⁻⁶. -3 Pa uses an AlCr alloy target, with the substrate surface aligned with the center of the AlCr alloy target, and the target-substrate distance adjusted to 60 mm; the AlCr alloy target consists of 96 at% Al and 4 at% Cr.

[0064] Argon (99.99% purity) and nitrogen (99.99% purity) were introduced at a gas flow ratio of 2:3 until the gas pressure (deposition pressure) in the cavity was 2.0 Pa. The radio frequency power supply was turned on, the sputtering power was 900 W, and the sputtering time was 8 h. An AlCrN piezoelectric coating was deposited on the substrate surface by magnetron sputtering technology.

[0065] Example 2: Adjusting the gas flow ratio of argon and nitrogen

[0066] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the gas flow ratios of argon and nitrogen introduced during magnetron sputtering are 3:1, 2:1, 1:1, 1:2 and 1:3, respectively.

[0067] Example 3: Adjusting the gas pressure during magnetron sputtering

[0068] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the ambient air pressure during magnetron sputtering is 1.0 Pa, 1.5 Pa, 2.0 Pa, 2.5 Pa, and 3.0 Pa, respectively.

[0069] Example 4: Adjusting the deposition temperature during magnetron sputtering

[0070] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the deposition temperature is 60℃, 100℃, 150℃, 200℃, and 250℃ during magnetron sputtering.

[0071] Example 5: Adjusting the sputtering power during magnetron sputtering

[0072] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the sputtering power is 800 W and 900 W respectively during magnetron sputtering.

[0073] Example 6: Adjusting the target-base distance during magnetron sputtering

[0074] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the distance between the target and the substrate during magnetron sputtering is 55 mm, 60 mm, 65 mm, 70 mm, and 75 mm, respectively.

[0075] Example 7: Adjusting the magnetron sputtering time during magnetron sputtering

[0076] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the magnetron sputtering time is 6 h, 8 h, 9 h, 10 h, and 12 h.

[0077] Example 8: Adjusting the atomic percentage of each metal in the AlCr alloy target material

[0078] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 1, except that the AlCr alloy target is composed of 92 at% Al and 8 at% Cr.

[0079] Example 9: Adjusting the gas flow ratio of argon and nitrogen

[0080] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 8, except that the gas flow ratios of argon and nitrogen introduced during magnetron sputtering are 3:1, 2:1, 1:1, 1:2 and 1:3, respectively.

[0081] Example 10: Adjusting the gas pressure during magnetron sputtering

[0082] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 8, except that the deposition gas pressures during magnetron sputtering are 1.0 Pa, 1.5 Pa, 2.0 Pa, 2.5 Pa, and 3.0 Pa, respectively.

[0083] Example 11: Adjusting the deposition temperature during magnetron sputtering

[0084] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 8, except that the magnetron sputtering temperature is 60℃, 100℃, 150℃, 200℃, and 250℃.

[0085] Example 12: Adjusting the sputtering power during magnetron sputtering

[0086] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 8, except that the sputtering power is 800 W and 900 W respectively.

[0087] Example 13: Adjusting the target-base distance during magnetron sputtering

[0088] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 8, except that the distance between the target and the substrate during sputtering is 55 mm, 60 mm, 65 mm, 70 mm, and 75 mm, respectively.

[0089] Example 14: Adjusting the magnetron sputtering time during magnetron sputtering

[0090] The AlCrN piezoelectric coating provided in this embodiment is prepared in a method that is basically the same as that in Example 8, except that the magnetron sputtering time is 6 h, 8 h, 9 h, 10 h, and 12 h, respectively.

[0091] Comparative Example 1

[0092] The AlCrN piezoelectric coating provided in this comparative example is prepared in a method that is basically the same as that in Example 1, except that: the AlCr alloy target is composed of 70 at% Al and 30 at% Cr; the gas flow ratio of argon and nitrogen during magnetron sputtering is 1:1; and the sputtering power is 800 W.

[0093] Comparative Example 2

[0094] The AlCrN piezoelectric coating provided in this comparative example is prepared in a method that is basically the same as that of comparative example 1, except that the sputtering power is 800 W and the deposition time is 6 h during magnetron sputtering.

[0095] Comparative Example 3

[0096] The AlCrN piezoelectric coating provided in this comparative example is prepared in a method that is basically the same as that of comparative example 1, except that the gas flow ratio of argon to nitrogen is 2:1 during magnetron sputtering.

[0097] Application examples

[0098] This application example involves preparing an AlCrN piezoelectric coating, a protective layer, and an electrode layer on a stainless steel bolt (substrate). The specific preparation method is as follows:

[0099] S1 and S2: Same as in Example 1.

[0100] S3. Using a polycrystalline silicon target (or a high-entropy target), a mixture of argon (99.99% purity) and oxygen (99.99% purity) with a flow rate ratio of 1:1 is introduced until the gas pressure (deposition pressure) in the cavity is 1.5 Pa; the radio frequency power supply is turned on, the sputtering power is 700 W, and the sputtering time is 3 h, thereby depositing a protective layer on the surface of the AlCrN piezoelectric coating.

[0101] S4. Using an Ag target (or AgCr target), argon gas (99.99% purity) is introduced until the gas pressure (deposition pressure) in the cavity is 1.0 Pa. The radio frequency power supply is turned on, the sputtering power is 700 W, and the sputtering time is 1 h to prepare the Ag electrode layer.

[0102] Experimental Examples: Performance Testing of Preparations from Examples, Comparative Examples, and Application Examples

[0103] 1. XRD pattern of AlCrN piezoelectric coating

[0104] Figure 1 To use the preparation method of Example 2, different gas flow ratios of argon and nitrogen were used during magnetron sputtering to prepare the XRD patterns of the AlCrN piezoelectric coatings. As can be seen from the figures, the AlCrN piezoelectric coatings exhibit a multi-oriented growth structure, including (002) and (103) oriented growth.

[0105] Figure 2 To follow the preparation method of Example 9, different gas flow ratios (2:1, 1:1, and 1:2) of argon and nitrogen were used during magnetron sputtering to obtain the XRD patterns of the AlCrN piezoelectric coatings. The figures show that the coating exhibits a multi-oriented growth structure.

[0106] Figure 3 The XRD pattern of the AlCrN coating obtained by the preparation method of Comparative Example 1 is shown. As can be seen from the figure, the film exists in a two-phase form, and the piezoelectric structure has been destroyed.

[0107] 2. Surface morphology diagram of the coating

[0108] Figure 4 To illustrate the preparation method described in Example 9, different gas flow ratios of argon and nitrogen were used during magnetron sputtering, resulting in surface and morphology screenshots of the prepared AlCrN coatings. As can be seen from the figures, with the increase of the argon-to-nitrogen gas flow ratio, the grain size gradually increases, and the thickness of the AlCrN piezoelectric coating also increases.

[0109] 3. Hardness test of AlCrN piezoelectric coating

[0110] Five AlCrN piezoelectric coatings prepared in Example 2 were selected, and their hardness performance was tested using a nanoindentation hardness tester.

[0111] Figure 5Using the preparation method of Example 2, different gas flow ratios of argon and nitrogen were used during magnetron sputtering to obtain hardness data for the AlCrN piezoelectric coatings prepared by nanohardness testing. As can be seen from the figures, the prepared AlCrN coatings all exhibit high hardness, exceeding 15 GPa. When the gas flow ratio of argon to nitrogen was 1:3, the hardness exceeded 30 GPa.

[0112] 4. Ultrasonic signal characterization

[0113] Using the preparation method of the application example, a protective layer was deposited on the surface of the AlCrN piezoelectric coating obtained in Example 2, and an Ag (or Ag-Cr) electrode layer was deposited on the surface of the protective layer for ultrasonic signal acquisition.

[0114] Figure 6 Using the preparation method of Example 2, AlCrN piezoelectric coatings prepared at different argon and nitrogen gas flow ratios were used to generate different ultrasonic waveforms. The waveforms show that the excited waveforms are a mixture of transverse and longitudinal waveforms. These various waveforms can meet the requirements for defect detection and stress measurement of steel plates, welds, and steel pipes in solid, liquid, and gaseous media.

[0115] 5. High temperature resistance test

[0116] Figure 7 To illustrate the preparation method described in Example 9, the ultrasonic signal images of the AlCrN piezoelectric coatings prepared under an argon to nitrogen gas flow ratio of 1:1 were obtained after annealing at 700°C for different times (0 h, 5 h, 20 h, and 50 h). The images clearly show that the film still exhibits stable ultrasonic signals after annealing at 700°C.

[0117] 6. Thin film composition testing

[0118] After magnetron sputtering in Examples 2 and 9 at a gas flow ratio of 1:1 for argon and nitrogen, the composition of the thin film micro-regions was analyzed using the energy dispersive spectroscopy (EDS) instrument integrated into a field emission scanning electron microscope (MIRA 3, LMH).

[0119] from Figure 8 As can be seen from the figure, the thin film prepared in this embodiment has a uniform composition, and the ratio of Al to Cr is basically consistent with the composition of the target material, which is approximately 51:2 and 48:5, respectively.

[0120] Based on the above experimental results, the AlCrN piezoelectric coating prepared by the method of the present invention exhibits a multi-oriented growth structure, including (002) and (103) oriented growth, which can generate different ultrasonic waveforms; the hardness is greater than 15 GPa, and the highest exceeds 30 GPa; it can be used for a long time at high temperature, and can still generate stable ultrasonic signals under annealing conditions at 700℃, which can meet the usage requirements of the working temperature range of -196~700℃.

[0121] It should be noted that the above application examples only use high-temperature alloy bolt substrates as examples. The preparation method of AlCrN piezoelectric coating material provided by the present invention is also applicable to substrates such as stainless steel, aluminum, cemented carbide, and titanium, and is not limited here.

[0122] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-hardness, high-temperature-resistant AlCrN piezoelectric coating material, characterized in that, An AlCr alloy target was used to form an AlCrN piezoelectric coating on the substrate surface by magnetron sputtering. The AlCr alloy target material is composed of 75-96 at% Al and 4-25 at% Cr.

2. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 1, characterized in that, The magnetron sputtering method is as follows: the temperature is 60-250℃, a mixed gas with an argon and nitrogen flow rate ratio of (1-81):9 is introduced, the sputtering power is 700-900 W, the deposition pressure is P=0.6-3.0 Pa, the target-substrate distance is d=40-80 mm, and the deposition time is 3-15 h.

3. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 1, characterized in that, Prior to magnetron sputtering, the substrate is subjected to surface plasma etching; Furthermore, the surface plasma etching is performed in an argon atmosphere at 60-250℃ and 0.5-2.0 Pa, with a duty cycle of 30-80%, a current of 70-110 A, a bias voltage of -100~-200 V, and an etching time of 0.5-2 h.

4. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 1, characterized in that, A protective layer was also deposited on the surface of the AlCrN piezoelectric coating.

5. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 4, characterized in that, The method for depositing the protective layer is as follows: SiO2 and / or high-entropy alloy oxide are deposited under a vacuum of 1-3 Pa and a power of 600-800 W to form the protective layer.

6. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 5, characterized in that, An Ag or AgCr electrode layer is also deposited on the surface of the protective layer; Furthermore, the electrode layer is deposited under the following conditions: under an argon atmosphere, an ambient pressure of 0.25-1 Pa, a bias voltage of 0 to -100 V, a deposition temperature of room temperature to 250°C, a sputtering distance of 40-80 mm, and a sputtering power of 500-800 W, for 0.5-4 h.

7. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 1, characterized in that, The alloy target has a diameter of 140-160 mm and a thickness of 4-8 mm.

8. The method for preparing the high-hardness, high-temperature-resistant AlCrN piezoelectric coating material according to claim 1, characterized in that, The thickness of the AlCrN piezoelectric coating is 5-20 μm.

9. A high-hardness, high-temperature-resistant AlCrN piezoelectric coating material prepared by the preparation method according to any one of claims 1-8.

10. An AlCrN piezoelectric coating material with high hardness and high temperature resistance prepared by the preparation method according to any one of claims 1-8, or the AlCrN piezoelectric coating material with high hardness and high temperature resistance according to claim 9, for use in bolt preload testing, or in defect detection and stress measurement of steel plates, welds, and steel pipes.

Images