High-temperature-resistant aln piezoelectric coating material capable of exciting multiple ultrasonic waves and preparation method and application thereof

Abstract

The application provides a preparation method of a high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves, and comprises the following steps: forming an AlN piezoelectric functional layer on the surface of a substrate by using an Al target through magnetron sputtering; and controlling the volume ratio of argon and nitrogen, the temperature, the sputtering power, the deposition pressure and the target-substrate distance in the magnetron sputtering so that the AlN piezoelectric functional layer grows in multiple orientations during the deposition process. The AlN piezoelectric coating material prepared by the application has good mechanical properties, temperature resistance and corrosion resistance, and can ensure the long-term stable service ability of the AlN piezoelectric coating under high temperature and harsh working conditions without a protective layer, reduce the failure possibility caused by corrosion and other factors, and realize the accurate nondestructive measurement of the bolt pretightening force, or realize the steel substrate defect detection and stress measurement. The sputtering technology adopted by the application is a general technology in the industry, and the industrial production batch is easy to realize, the processing efficiency is high, and the production cost of the manufacturer can be greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of coating materials, and particularly relates to a high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves and a preparation method thereof, and also relates to application of the AlN piezoelectric coating material in ultrasonic detection. BACKGROUND

[0002] Bolt fasteners are the most widely used connection method at present due to low cost, good interchangeability, convenient installation and removal, etc. Typical bolt connection forms include a bolt, a nut and a clamping component. When the bolt or the nut is tightened, the bolt is elongated and generates a pre-tightening force. Adequate pre-tightening force is crucial to ensure the connection and fastening performance and improve product reliability. Especially, aerospace equipment is often subjected to complex and variable working conditions, and usually encounters harsh working conditions such as high temperature, high stress and long-term mutual friction, which often causes the bolt connection joint to have a pre-tightening force drop, a joint surface loosening, slippage and an abnormal sound, etc. Finally, the system stiffness is reduced, the structural integrity is damaged, the vibration is intensified and the energy dissipation is increased, thereby affecting the working performance and safety and reliability of the equipment.

[0003] The ultrasonic detection pre-tightening force technology has the advantages of high precision, good real-time performance and strong penetration. The ultrasonic stress measurement method is one for measuring by using an ultrasonic probe and a coupling agent, and another is for pasting a piezoelectric ceramic sheet on a detected part. The above methods have complicated operations, corrosion problems and also need to consider the influence of the adhesive on signal propagation. The thin film with piezoelectric effect has a simple preparation method, high stability and wide applicability. Direct deposition of the piezoelectric coating on the bolt surface can avoid all adverse effects caused by the coupling agent or the adhesive, and the measurement is fast and accurate. A large number of studies have shown that when the stress is detected by using the combined method of the transverse wave and the longitudinal wave, in addition to the constant related to the material performance and geometry, only the initial temperature and the longitudinal wave and transverse wave flight time of the bolt in the unloaded state need to be measured. This method can reduce the number of compensation factors and simplify the detection steps, and improve the measurement accuracy.

[0004] At present, the piezoelectric materials that can be used to excite ultrasonic waves mainly include ZnO and AlN. Both of the two materials are hexagonal wurtzite structure, and the performance of the piezoelectric effect is completely dependent on the crystal orientation without polarization. ZnO does not have good high-temperature resistance, and generally cannot be used in working conditions with large stress and long-term wear and high temperature. The AlN piezoelectric material has good mechanical properties, corrosion resistance and high-temperature resistance, can grow on various substrates, and has low epitaxial growth temperature requirement, and the stoichiometry and texture are easier to control. Therefore, the AlN coating with excellent high-temperature resistance and mechanical properties can be selected as the acoustic-electric conversion layer for exciting ultrasonic waves.

[0005] Based on this, a high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves and a preparation method thereof are provided, and the material is applied to the manufacture of high-temperature-resistant intelligent bolts, which is of great significance for realizing accurate nondestructive measurement of pre-tightening force and is a technical problem that researchers urgently need to solve. SUMMARY

[0006] One of the purposes of the present application is to provide a preparation method of an AlN piezoelectric coating that has high mechanical properties, corrosion resistance and high-temperature resistance and can excite multiple ultrasonic waves.

[0007] The second purpose of the present application is to provide an AlN piezoelectric coating that has high mechanical properties, corrosion resistance, high-temperature resistance and can excite multiple ultrasonic waves.

[0008] The third purpose of the present application is to provide an application of a high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves in ultrasonic detection.

[0009] The technical solution adopted by one of the purposes of the present application is to provide a preparation method of a high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves, comprising: using an Al target to form an AlN piezoelectric functional layer on the surface of a substrate by magnetron sputtering.

[0010] In the magnetron sputtering, the sputtering temperature is 60-250 DEG C, the target-substrate distance is 40-80 mm, the mixed gas of argon and nitrogen with a volume ratio of 3:1-1:3 is introduced into the cavity to a pressure of 0.6-4.0 Pa, the sputtering power is 500-900 W, and the sputtering time is 3-15 h.

[0011] In the above preparation method, the AlN piezoelectric functional layer is prepared by radio frequency magnetron sputtering, the sputtering temperature is controlled to be 60-250 DEG C, the temperature rise can make the particles have higher energy, and in this temperature range, the particles can have enough energy to migrate to the surface of the substrate to deposit the AlN coating; the volume ratio of argon and nitrogen is controlled, the atomic percentage of Al and N particles in the vacuum cavity can be controlled, the collision probability between particles can be adjusted, and the growth orientation of the coating can be adjusted; the sputtering power is 500-900 W, under which the energy of the particles can be adjusted, and the thickness of the prepared coating can be controlled; the deposition pressure (pressure after the reaction gas is introduced into the vacuum chamber) P is controlled to be 0.6-4.0 Pa, and the target-substrate distance (vertical distance between the target and the substrate) is controlled to be 40-80 mm, so that the average free path of Al and N particles can be adjusted, and multiple orientation growth AlN coatings can be prepared in this deposition range. Under the above preparation conditions, the AlN piezoelectric functional layer with high mechanical properties, corrosion resistance and high-temperature resistance and capable of exciting multiple ultrasonic waves can be prepared.

[0012] In the present application, the substrate is selected from stainless steel, aluminum, carbide, high-speed steel, titanium and other suitable substrates for ultrasonic testing.

[0013] Further, in the magnetron sputtering, the higher the sputtering power, the greater the degree of ionization of argon, and the Al particles sputtered have higher kinetic energy to migrate to the substrate surface; the extension of the deposition time increases the thickness of the coating, which helps to increase the amplitude of the ultrasonic signal excited by the coating. Preferably, the sputtering power is 800-900 W, and the deposition time is 8-10 h.

[0014] Further, the diameter of the Al target is 100-160 mm, and the thickness of the Al target is 4-8 mm. In the present application, the diameter and thickness of the target have a certain correspondence with the power of magnetron sputtering. The present application uses a larger diameter target in combination with a higher sputtering power, which can simultaneously prepare more samples during coating deposition, has higher deposition efficiency, is easy to mass produce, and is more easily popularized and used.

[0015] Further, the growth orientation of the AlN piezoelectric functional layer on the surface of the substrate includes one or a combination of (002) diffraction crystal face, (100) diffraction crystal face, (101) diffraction crystal face, and (102) diffraction crystal face.

[0016] Further, it has been found through research that, in the present application, by adjusting the deposition parameters in the magnetron sputtering process, such as the volume ratio of argon and nitrogen, the deposition pressure and the target-substrate distance, the AlN piezoelectric functional layer on the surface of the substrate can exhibit multiple growth orientations, can excite multiple ultrasonic waveforms, and can thus prepare AlN piezoelectric coating materials that can excite different ultrasonic waves according to detection needs:

[0017] Preferably, when the deposition temperature is 60-250℃, the sputtering power is 800-900 W, the deposition pressure is 3.5-4.0 Pa, and the volume ratio of argon and nitrogen is 1:1, the coating exhibits a high-c-axis-oriented (002) diffraction crystal face, and the coating can emit obvious longitudinal waves when excited;

[0018] Preferably, when the volume ratio of argon and nitrogen is 1:3, the coating can emit obvious transverse waves when excited;

[0019] Preferably, when the deposition pressure is 0.6-2.8 Pa and the volume ratio of argon to nitrogen is 3:1-1:2, the AlN piezoelectric functional layer presents typical multi-orientation growth on the substrate surface, including multi-orientation growth of (100) diffraction crystal face, (002) diffraction crystal face, (101) diffraction crystal face and (102) diffraction crystal face. Under the above conditions, the AlN piezoelectric coating material prepared by the application can emit combined waves of longitudinal waves and transverse waves when excited. A large number of studies have shown that when the stress is detected by using the combined method of longitudinal waves and transverse waves, in addition to the constant related to the performance and geometric shape of the material itself, only the longitudinal wave and transverse wave flight time of the bolt in the unloaded state and the initial temperature need to be measured, and then the real-time load of the bolt can be obtained by solving the eight-order polynomial without calibrating the original stress. This method can reduce the number of compensation factors and simplify the detection steps, reduce the error existing in the conversion calculation between the ultrasonic signal and the stress, and improve the measurement accuracy.

[0020] Further, the preparation method comprises the following steps: first, depositing a bonding layer on the surface of the substrate, then depositing an AlN piezoelectric functional layer on the surface of the bonding layer, and finally depositing an electrode layer on the surface of the AlN piezoelectric functional layer. The bonding layer can increase the bonding force between the substrate and the coating, avoiding problems such as cracking and falling off of the coating during long-term use. The electrode layer can provide an external electrode for the substrate (bolt or steel plate), so that a stable voltage can be applied to the two poles of the substrate to excite ultrasonic waves. The material of the bonding layer includes Cr, and the electrode layer can be one of Cr, Ti, Ag, Ag-Cr and high-temperature glue containing silver powder.

[0021] Preferably, the preparation method of the application can comprise the following steps:

[0022] S1, controlling the distance between the target material and the substrate to be 40-80 mm, and performing plasma etching on the surface of the substrate in a vacuum and argon environment at 60-250 DEG C;

[0023] S2, depositing a Cr bonding layer on the surface of the substrate after plasma etching at 0.5-1 Pa and a bias voltage of 50-250 V;

[0024] S3, forming an AlN piezoelectric functional layer on the surface of the Cr bonding layer by using a magnetron sputtering method;

[0025] S4, depositing an electrode layer on the surface of the AlN piezoelectric functional layer, and the electrode layer is selected from one of Cr, Ti, Ag, Ag-Cr and high-temperature glue containing silver powder, that is, the preparation of the AlN piezoelectric coating material is completed.

[0026] The technical scheme for achieving the second purpose of the present application is: providing a high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves, which is prepared according to the preparation method of the AlN piezoelectric coating material according to the first purpose of the present application.

[0027] The AlN piezoelectric coating material is composed of a bonding layer, an AlN piezoelectric functional layer and an electrode layer. The AlN piezoelectric coating material prepared according to the present application has high mechanical properties, corrosion resistance and high-temperature resistance, and can excite multiple ultrasonic waves. In some preferred embodiments, the high-temperature-resistant AlN piezoelectric coating material is heat-treated at 800℃ for 200h, and its surface morphology and ultrasonic wave excitation performance do not change. Without the need for a protective layer, the high-temperature-resistant AlN piezoelectric coating material can meet the requirements for long-term use in harsh working conditions and high-temperature environments.

[0028] The technical scheme for achieving the third purpose of the present application is: providing an application of the high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves according to the second purpose of the present application, wherein the high-temperature-resistant AlN piezoelectric coating material excites multiple ultrasonic waveforms, and is used for pre-tightening force detection of a bolt, or for defect detection and stress measurement of a steel plate, a weld seam or a steel pipe.

[0029] In some preferred embodiments, the substrate of the AlN piezoelectric coating material is a smart bolt, and the bonding layer, the AlN piezoelectric functional layer and the electrode layer are sequentially deposited on the surface of the smart bolt according to the preparation method provided by the present application. According to the specific requirements of bolt pre-tightening force measurement, the relevant parameters in the preparation method of the AlN piezoelectric coating material are adjusted to make the smart bolt with the piezoelectric coating material on the surface excite different waveforms (longitudinal wave, transverse wave or longitudinal-transverse wave). The above features can simplify the bolt pre-tightening force calculation steps and improve the measurement accuracy. The AlN piezoelectric coating of the smart bolt also has high mechanical properties, corrosion resistance, high-temperature resistance and other advantages, which can widen the working temperature range, improve the working performance in harsh working conditions, and prolong the service life of the smart bolt.

[0030] Compared with the prior art, the present application has the following advantages:

[0031] (1) The application provides a preparation method of a high-temperature-resistant AlN piezoelectric coating capable of exciting multiple ultrasonic waves, wherein the AlN piezoelectric coating is prepared by radio frequency magnetron sputtering, and by adjusting different deposition temperatures, sputtering powers, deposition air pressures, flow ratios of argon and nitrogen, and distances between a target material and a substrate, a piezoelectric coating material capable of exciting different waveforms at the same time can be prepared, and the bolt pre-tightening force can be accurately measured. In addition, the AlN piezoelectric coating serves as a hard coating, is different from a ZnO piezoelectric coating, has high hardness, high wear resistance and high corrosion resistance, does not need to be additionally deposited with a protective layer, and has high-temperature resistance and can be used for a long time at 800 DEG C, can be used for a long time under harsh working conditions, and is simple to prepare and high in working efficiency.

[0032] (2) The AlN piezoelectric coating prepared by the application forms an AlN piezoelectric functional layer by magnetron sputtering and has the following advantages: first, the AlN coating with high piezoelectric coefficient, high electromechanical coupling coefficient and low epitaxial growth temperature can be applied to various materials with large acoustic attenuation coefficient; second, the AlN coating in the application is directly deposited on the surface of a bolt as an ultrasonic excitation acoustic-electric conversion layer, and nondestructive testing technology can be realized; third, the AlN piezoelectric coating has high hardness, and the hardness is greater than 15 GPa; fourth, the AlN piezoelectric coating has high wear resistance and can achieve extremely low wear rate and excellent wear resistance in the wear test; fifth, the AlN piezoelectric coating has high bonding strength, and the bonding strength can be greater than 10 MPa; sixth, the AlN piezoelectric coating has high corrosion resistance, can resist neutral salt spray corrosion for more than 1000 h, has excellent alkaline corrosion resistance and can be soaked in a 5% NaOH solution for a long time and still be used normally; seventh, the AlN coating prepared in the application has excellent temperature resistance and can be used between -196 DEG C and 700 DEG C; eighth, the AlN piezoelectric coating prepared in the application has high accuracy, and the accuracy can be less than 5%; ninth, the AlN piezoelectric coating capable of exciting ultrasonic longitudinal waves and ultrasonic longitudinal-transverse waves at the same time can be prepared by adjusting the deposition temperature, the sputtering power, the deposition air pressure, the flow ratio of argon and nitrogen, and the distance between the target material and the substrate, the preparation method is simple and feasible, has wide adaptability, and can provide important value for the field of new ultrasonic transducers.

[0033] (3) The AlN piezoelectric coating prepared by the application has high hardness, high wear resistance, high bonding force, high corrosion resistance and excellent temperature resistance, can simultaneously excite ultrasonic longitudinal and transverse waves, can measure the pre-tightening force of a bolt with high precision, can be used for defect detection and stress measurement of a steel plate, a weld and a steel pipe, can ensure long-term stable work of the piezoelectric coating on the surface of various alloy bolts and reduce the possibility of failure. Meanwhile, the preparation technology and equipment are close to the existing industrial equipment, industrial production batches are easy to realize, the processing efficiency is high, the production cost of manufacturers can be greatly reduced, and the application prospect is wide. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The device schematic diagram for preparing the AlN piezoelectric coating material used in the embodiment of the application;

[0035] Figure 2 The XRD pattern of the thin film prepared in the embodiment 1 of the application under different deposition powers;

[0036] Figure 3 The ultrasonic wave signal diagram of the AlN thin film prepared in the embodiment 2 of the application under different deposition temperatures;

[0037] Figure 4 The ultrasonic signal diagram of the AlN thin film prepared in the embodiment 3 of the application under different sputtering gas pressures;

[0038] Figure 5 The ultrasonic signal diagram of the AlN thin film prepared in the embodiment 4 of the application under different argon-nitrogen ratios;

[0039] Figure 6 The ultrasonic signal diagram of the AlN thin film prepared in the embodiment 5 of the application under different target-substrate distances;

[0040] Figure 7 The ultrasonic signal diagram of the AlN thin film prepared in the embodiment 6 of the application under different deposition times;

[0041] Figure 8 The surface and cross-section morphology diagrams of the AlN thin film prepared in the embodiment 7 of the application after heat treatment annealing at 600 DEG C, 700 DEG C, 800 DEG C and 900 DEG C, respectively;

[0042] Figure 9 The ultrasonic echo signal diagram of the AlN thin film prepared in the embodiment 7 of the application on a stainless steel substrate after heat treatment at an annealing temperature of 600-800 DEG C for 1 h;

[0043] Figure 10The AlN thin film prepared under the condition of the embodiment 7 of the present application is respectively heat-treated and annealed at 800℃ for 1h, 5h, 20h, 50h, 100h and 200h, and the surface morphology diagram of the AlN thin film after annealing is shown in Fig. 2;

[0044] Figure 11 The ultrasonic echo signal diagram of the AlN thin film prepared on the base of the bolt under the deposition condition of the AlN piezoelectric functional layer of the embodiment 7 of the present application after heat treatment at the annealing temperature of 800℃ for 1-200h is shown in Fig. 3;

[0045] In the figure, 1 is a radio frequency magnetron sputtering (RF); 2 is an Al target; 3 is a bolt sample; 4 is an etching source; 5 is a sample holder; 6 is a workpiece holder; 7 is a heater; 8 is an air outlet; and 9 is a furnace door. DETAILED DESCRIPTION

[0046] The technical solutions of the present application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0047] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0048] Figure 1 As shown in the figure, the vacuum chamber of the device used in the present application is surrounded by the furnace wall, and the size of the vacuum chamber is 400x400x400 mm. The vacuum chamber is provided with an air outlet 8, and a vacuum pumping unit performs vacuum pumping on the vacuum chamber through the air outlet 8. The upper two corners of the vacuum chamber are provided with a heater 7, and the heating power is 25 kW, so that the heating efficiency is improved. The lower two corners of the vacuum chamber are provided with an etching source 4, which can remove impurities on the surface of the base to ensure the cleanliness of the surface of the base. The Al target 2 is installed on the furnace wall and connected with the radio frequency magnetron sputtering (RF) 1 together, so that the sputtering power can be adjusted. The back of the Al target 2 is opposite to the furnace door 9, and the front of the Al target 2 is the sample 3. The sample 3 is placed on the sample holder 5, and the sample holder is installed on the workpiece holder 6. This layout greatly increases the plasma density in the vacuum chamber, and the workpiece is completely immersed in the plasma. The coating deposition rate, hardness and adhesion are greatly improved. Since the target structure is optimized, the magnetic field distribution is more uniform, the magnetron sputtering target surface etching is uniform, and the uniformity of the coating is improved.

[0049] The overall preparation method of the high-temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves provided by the embodiment of the present application is as follows:

[0050] The distance between the target and the base is controlled to be 40-80 mm, the vacuum is pumped to be not more than 5x10- 3 Pa, the position of the substrate is controlled to face the center of the target material, a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%) is introduced, the flow ratio of argon and nitrogen is between 3:1 and 1:3, the gas pressure in the cavity is 0.6-4.0 Pa, the RF power is 500-900 W, and the sputtering time is 3-15 h.

[0051] After the etching, the vacuum is extracted to not more than 5*10 -3 Pa, the position of the substrate is controlled to face the center of the target material, a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%) is introduced, the flow ratio of argon and nitrogen is between 3:1 and 1:3, the gas pressure in the cavity is 0.6-4.0 Pa, the RF power is 500-900 W, and the sputtering time is 3-15 h.

[0052] The application is further described below in combination with specific examples, but is not limited to the application. The main parameters and variables involved in the preparation of the AlN piezoelectric coating in each example of the application are shown in Table 1.

[0053] Table 1

[0054]

[0055]

[0056] In each of the above examples, the substrate is a Si substrate, a stainless steel substrate or a bolt, and the target material is a pure Al (purity 99.9999%) target material.

[0057] Example 1

[0058] The distance between the target material and the substrate is controlled to be 55 mm, the vacuum is extracted to not more than 5*10 -3 Pa, the position of the substrate is controlled to face the center of the target material, a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%) is introduced, the flow ratio of argon and nitrogen is between 3:1 and 1:3, the gas pressure in the cavity is 0.6-4.0 Pa, the RF power is 500-900 W, and the sputtering time is 3-15 h.

[0059] After the etching, the vacuum is extracted to not more than 5*10 -3Pa, control the position of the substrate directly opposite the center of the target, pass in the mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow ratio of argon and nitrogen is 1:1, to the gas pressure in the cavity is 3.5 Pa, open the radio frequency power source, the sputtering power is 500 W, 600 W, 700 W, 800 W and 900 W respectively, the sputtering time is 8 h; after the preparation of the AlN piezoelectric coating, naturally cool to room temperature, the high temperature-resistant AlN piezoelectric coating material that can excite various ultrasonic waves can be obtained on the surface of the substrate.

[0060] Example 2

[0061] Control the distance between the target and the substrate to be 55 mm, under the conditions of the temperature being 60℃, 100℃, 150℃, 200℃ and 250℃ respectively, vacuum to not more than 5*10 -3 Pa, pass in 50-100 sccm of argon (purity 99.99%), open the bias and arc power source, under the conditions of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, current 70-90 A, carry out plasma etching on the substrate to remove the impurities attached to the surface of the substrate and improve the bonding force between the film layer and the substrate.

[0062] After the etching is completed, vacuum to not more than 5*10 -3 Pa, control the position of the substrate directly opposite the center of the target, pass in the mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow ratio of argon and nitrogen is 1:1, to the gas pressure in the cavity is 3.5 Pa, open the radio frequency power source, the sputtering power is 900 W, the sputtering time is 8 h; after the preparation of the AlN piezoelectric coating, naturally cool to room temperature, the high temperature-resistant AlN piezoelectric coating material that can excite various ultrasonic waves can be obtained on the surface of the substrate.

[0063] Example 3

[0064] Control the distance between the target and the substrate to be 55 mm, under the conditions of the temperature being 60℃, 100℃, 150℃, 200℃ and 250℃ respectively, vacuum to not more than 5*10 -3 Pa, pass in 50-100 sccm of argon (purity 99.99%), open the bias and arc power source, under the conditions of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, current 70-90 A, carry out plasma etching on the substrate to remove the impurities attached to the surface of the substrate and improve the bonding force between the film layer and the substrate.

[0065] After the etching is completed, vacuum to not more than 5*10 -3Pa, control the position of the substrate directly opposite the center of the target, pass in a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow ratio of argon and nitrogen being 1:1, until the gas pressure in the cavity is 0.6 Pa, 1.2 Pa, 2.0 Pa, 2.6 Pa and 3.5 Pa respectively, turn on the radio frequency power supply, the sputtering power being 900 W, and the sputtering time being 8 h; after the AlN piezoelectric coating is prepared, naturally cool to room temperature, and the high temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves can be obtained on the surface of the substrate.

[0066] Example 4

[0067] Control the distance between the target and the substrate to be 55 mm, vacuumize to not more than 5*10 -3 Pa at 100℃, pass in 50-100 sccm of argon (purity 99.99%), turn on the bias voltage and arc power supply, carry out plasma etching on the substrate under the condition of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, and current 70-90 A, remove the impurities adhered to the surface of the substrate, and improve the adhesion between the film layer and the substrate.

[0068] After the etching is completed, vacuumize to not more than 5*10 -3 Pa, control the position of the substrate directly opposite the center of the target, pass in a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow ratio of argon and nitrogen being 1:1, until the gas pressure in the cavity is 0.6 Pa, 1.2 Pa, 2.0 Pa, 2.6 Pa and 3.5 Pa respectively, turn on the radio frequency power supply, the sputtering power being 900 W, and the sputtering time being 8 h; after the AlN piezoelectric coating is prepared, naturally cool to room temperature, and the high temperature-resistant AlN piezoelectric coating material capable of exciting multiple ultrasonic waves can be obtained on the surface of the substrate.

[0069] Example 5

[0070] Control the distance between the target and the substrate to be 55 mm, vacuumize to not more than 5*10 -3 Pa at 100℃, pass in 50-100 sccm of argon (purity 99.99%), turn on the bias voltage and arc power supply, carry out plasma etching on the substrate under the condition of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, and current 70-90 A, remove the impurities adhered to the surface of the substrate, and improve the adhesion between the film layer and the substrate.

[0071] After the etching is completed, vacuumize to not more than 5*10 -3Pa, control the position of the substrate directly opposite the center of the target, pass in a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow ratio of argon and nitrogen being between 1:1, to an internal gas pressure of 0.6 Pa in the chamber, turn on the radio frequency power supply, the sputtering power being 900 W, and the sputtering time being 8 h; after the AlN piezoelectric coating is prepared, naturally cool to room temperature, and the high-temperature-resistant AlN piezoelectric coating material capable of exciting various ultrasonic waves can be obtained on the surface of the substrate.

[0072] Example 6

[0073] Control the distance between the target and the substrate to be 60 mm, vacuumize to not more than 5*10 -3 Pa, pass in 50-100 sccm of argon (purity 99.99%), turn on the bias voltage and arc power supply, carry out plasma etching on the substrate under the conditions of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, and current 70-90 A, remove the impurities adhered to the surface of the substrate, and improve the adhesion between the film layer and the substrate.

[0074] After the etching is completed, vacuumize to not more than 5*10 -3 Pa, control the position of the substrate directly opposite the center of the target, pass in a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow ratio of argon and nitrogen being between 1:1, to an internal gas pressure of 3.6 Pa in the chamber, turn on the radio frequency power supply, the sputtering power being 900 W, and the sputtering time being 4 h, 6 h, 8 h, and 10 h respectively; after the AlN piezoelectric coating is prepared, naturally cool to room temperature, and the high-temperature-resistant AlN piezoelectric coating material capable of exciting various ultrasonic waves can be obtained on the surface of the substrate.

[0075] Example 7

[0076] Control the distance between the target and the substrate to be 55 mm, vacuumize to not more than 5*10 -3 Pa, pass in 50-100 sccm of argon (purity 99.99%), turn on the bias voltage and arc power supply, carry out plasma etching on the substrate under the conditions of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, and current 70-90 A, remove the impurities adhered to the surface of the substrate, and improve the adhesion between the film layer and the substrate.

[0077] After the etching is completed, vacuumize to not more than 5*10 -3Pa, control the position of the substrate opposite the center of the target, the mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%) is input into the cavity, the flow ratio of argon and nitrogen is 1:1, the gas pressure in the cavity is 3.5Pa, the radio frequency power is turned on, the sputtering power is 900W, the sputtering time is 8h; after the preparation of the AlN piezoelectric coating, the substrate is naturally cooled to room temperature, and the high-temperature-resistant AlN piezoelectric coating material capable of exciting various ultrasonic waves can be obtained on the surface of the substrate.

[0078] Performance test

[0079] (I) Influence of different sputtering powers on growth orientation of thin films

[0080] Figure 2 The XRD pattern of the thin film prepared in Example 1 of the present application under different deposition powers can be seen from the figure, under the premise that the deposition gas pressure is 3.5Pa, the flow ratio of argon and nitrogen is 1:1, and the target-substrate distance is 55mm, with the change of the sputtering power, the diffraction peak position of the AlN thin film does not change, and the (002) diffraction peak c-axis preferential orientation growth appears at about 35.5°. With the increase of the sputtering power, the diffraction peak intensity and half-width of the thin film both show a trend of first increasing and then decreasing, when the sputtering power is 800W, the diffraction peak intensity reaches the maximum, and when the sputtering power is 900W, the half-width of the thin film is the smallest, because the greater the sputtering power, the greater the ionization degree of argon, and the Al particles sputtered have higher kinetic energy to migrate to the surface of the substrate, showing more significant c-axis preferential growth.

[0081] (II) Influence of different sputtering temperatures on growth orientation of thin films

[0082] Figure 3 The ultrasonic wave signals excited by the AlN thin film prepared in Example 2 under different deposition temperatures can be seen from the figure, under the premise that the deposition gas pressure is 3.5Pa, the flow ratio of argon and nitrogen is 1:1, the target-substrate distance is 55mm, and the sputtering power is 900W, the AlN piezoelectric thin films prepared under different deposition temperatures can all excite ultrasonic longitudinal waves, because the prepared AlN piezoelectric thin film shows c-axis preferential orientation growth, the growth structure is perpendicular to the substrate surface, and the particles are easy to vibrate in the direction parallel to the propagation direction of the ultrasonic wave, thereby exciting the ultrasonic longitudinal wave (LW).

[0083] (III) Ultrasonic signals excited by AlN thin films under different sputtering gas pressures

[0084] Figure 4The ultrasonic signals excited by the AlN thin films prepared in Example 3 under different sputtering gas pressures can be seen from the figures. The excited ultrasonic waves are two different ultrasonic wave types, i.e. ultrasonic longitudinal waves and ultrasonic transverse waves. As can be seen from the ultrasonic signal figures, under the premise that the sputtering power, sputtering time, flow ratio of argon and nitrogen is 1:1 and target-substrate distance is 55 mm, when the deposition pressure is 3.5 Pa, the excited ultrasonic wave is an ultrasonic longitudinal wave. With the decrease of the sputtering gas pressure, the ultrasonic wave excited by the thin film is a longitudinal-transverse mixed wave, which is related to the growth structure and morphology of the thin film. When the sputtering gas pressure is 3.5 Pa, the growth of the thin film is (002) growth, which shows a highly preferred growth orientation, and the morphology is a columnar crystal structure perpendicular to the substrate, so the excited ultrasonic wave is an ultrasonic longitudinal wave. With the decrease of the deposition pressure, the growth orientation of the thin film changes from (002) growth to multi-orientation growth of (100), (002) and (101), and the growth morphology of the thin film changes from columnar crystal growth perpendicular to the substrate to growth inclined to the substrate, so the excited ultrasonic wave changes from an ultrasonic longitudinal wave to an ultrasonic longitudinal-transverse mixed wave.

[0085] (Four) Ultrasonic signals excited by AlN thin films under different argon-nitrogen ratios

[0086] Figure 5 The ultrasonic signals excited by the AlN thin films prepared in Example 4 under different argon-nitrogen ratios can be seen from the figures. Under the conditions of a target-substrate distance of 55 mm and a deposition pressure of 0.6-2.8 Pa, the excited ultrasonic waves are two ultrasonic wave types, i.e. longitudinal waves and transverse waves. As can be seen from the ultrasonic signal figures, when the argon-nitrogen ratio is between 3:1 and 1:2, ultrasonic longitudinal-transverse waves can be excited, which is related to the growth orientation of the thin film. Since the growth orientation of the thin film shows multi-orientation growth structure of (100), (002), (101) and (102) in the argon-nitrogen ratio range, ultrasonic longitudinal-transverse waves can be excited. When the argon-nitrogen ratio is 1:3, the thin film shows obvious columnar crystal growth, which can excite obvious transverse waves (SW), which corresponds to the cross-sectional morphology of the thin film.

[0087] (Five) Ultrasonic signals excited by AlN thin films prepared under different target-substrate distances

[0088] Figure 6 The ultrasonic signals excited by the AlN thin films prepared under different target-substrate distances in Example 5 can be seen from the figures. Under the conditions of a deposition pressure of 0.6 Pa and a flow ratio of argon and nitrogen of 1:1, the excited ultrasonic waves are two ultrasonic wave types, i.e. longitudinal waves and transverse waves.

[0089] (Six) Ultrasonic signals excited by AlN thin films prepared under different times

[0090] Figure 7The ultrasonic signals excited by the AlN films prepared in different times of the embodiment 6 of the present application can be seen from the figure, under the premise that the deposition pressure is 3.6 Pa, the flow ratio of argon and nitrogen is 1:1, and the target-substrate distance is 60 mm, the excited ultrasonic signals are all ultrasonic longitudinal wave signals. With the increase of the deposition time, the amplitude of the ultrasonic signals excited by the coating increases, combined with the X-ray diffraction pattern and the scanning electron microscope image, with the increase of the deposition time, the c-axis preferred orientation of the coating is better, the thickness of the coating increases, and thus the ability of the coating to excite ultrasonic signals is enhanced, and at 10 h, the best is reached.

[0091] (VII) High temperature resistance test of the AlN film

[0092] The AlN film prepared in the embodiment 7 is subjected to high temperature annealing experiment, the annealing experiment is carried out in a muffle furnace with the model of XMT-8000, the annealing temperature of the AlN film is 400-900 ℃, the heating rate is 5 ℃ / min, the holding time is between 1-200 h, after the annealing experiment is finished, the sample is taken out after being cooled to room temperature with the furnace.

[0093] Figure 8 The surface and cross-section morphology of the AlN film prepared in the embodiment 7 of the present application is subjected to heat treatment annealing at 600 ℃, 700 ℃, 800 ℃ and 900 ℃ respectively, from the surface morphology of the annealing, it can be seen that the surface of the AlN film is dense, without cracks and impurities such as large particles, the film surface presents obvious grain arrangement, and the grain boundary can be seen. When the annealing temperature is from 600-800 ℃, the surface morphology of the AlN film does not change, and the grain size and grain state are similar to those before annealing, which shows that the heat treatment of the prepared AlN film at 800 ℃ does not damage the morphology of the film, so that the surface morphology changes. With the increase of the annealing temperature, when the annealing temperature reaches 900 ℃, it can be clearly seen that the surface morphology has changed. It shows that short time annealing at 800 ℃ does not change the morphology of the AlN film, and the film can still be used normally.

[0094] Figure 9 The ultrasonic echo signals of the AlN film prepared in the embodiment 7 of the present application on the stainless steel substrate after heat treatment at 600-800 ℃ for 1 h can be seen from the figure, the increase of the annealing temperature does not change the amplitude and position of the ultrasonic signals excited by the AlN film, heat treatment at 800 ℃ for 1 h does not change the waveform and intensity of the ultrasonic waves excited by the AlN film, and the ultrasonic longitudinal wave can be excited after heat treatment, which is because the (002) growth orientation of the AlN film does not change in the annealing temperature range, and the ultrasonic longitudinal wave can be excited under the growth orientation.

[0095] The ultrasonic echo signal of the AlN film prepared on the base of the bolt after heat treatment at the annealing temperature of 600-800℃ for 1h is shown in Figure (b). Since the length of the bolt is much greater than the thickness of the stainless steel plate, the excited ultrasonic signal can be more obviously distinguished. It can also be seen that the AlN film prepared under the deposition condition has good piezoelectric properties on the bolt, which can excite obvious four bottom surface ultrasonic echo signals, and the amplitude of the echo signal gradually decreases. According to the flight time of the ultrasonic wave in the bolt of 8.09μs, the flight distance is the length of the bolt of 24mm, the propagation speed of the AlN film on the stainless steel bolt can be calculated as 5858m / s, which shows that the excited waveform is still ultrasonic longitudinal wave, which is consistent with the waveform excited on the stainless steel sheet. As can be seen from Figure (b), the position of the ultrasonic signal excited by the AlN film on the bolt does not change with the increase of the annealing temperature, and the AlN film on the bolt can still excite ultrasonic longitudinal wave after heat treatment at the annealing temperature of 800℃ for 1h. The amplitude of the first and second echo signals of the bolt after heat treatment at different annealing temperatures is shown in Figure (c). As can be seen from the figure, the amplitude of the excited ultrasonic echo signal presents the trend of first increasing and then decreasing, which is due to the increase of the particle energy in the AlN film with the increase of the temperature, and the ability of migration and rearrangement to the (002) direction is enhanced, which presents the reason for the more optimal c-axis oriented growth. Since the (002) growth orientation of the AlN film does not change, ultrasonic longitudinal wave can still be excited after annealing at different temperatures. The decay rate of the AlN film prepared on the bolt after 1h annealing at different annealing temperatures is calculated and plotted as shown in Figure (d). As can be seen from the figure, the decay rate is the smallest of 49.7% after annealing at 700℃, which shows that the AlN film heat treated at this temperature has excellent temperature resistance and can maintain a low decay rate.

[0096] Figure 10 The AlN film prepared in Example 7 of the application was annealed at 800℃ for 1h, 5h, 20h, 50h, 100h and 200h respectively. The surface morphology of the AlN film after annealing is shown in Figure Figure 10 As can be seen from the surface morphology of the AlN film after annealing, the surface of the AlN film is uniform, and the film presents obvious grain arrangement, and the surface is clean without large particles. The surface morphology of the AlN film does not change from 1h to 200h of annealing time, which presents similar grain size and grain state to that before annealing, which shows that the AlN film prepared at the temperature of 800℃ for 200h of annealing does not cause damage to the surface morphology of the film to change the surface morphology, which shows that the long-time annealing of the prepared AlN film at 800℃ does not change the morphology of the AlN film, and the film can still be used normally, which has good long-time high temperature resistance.

[0097] Application Example

[0098] The application example adopts stainless steel bolts with a length of 24 mm as the base body, deposits AlN piezoelectric coating material on the surface of the base body, and realizes the preparation of high-temperature-resistant intelligent bolts that can excite multiple ultrasonic waves. The preparation method of the intelligent bolts comprises the following steps:

[0099] Step 1: control the distance between the target material and the base body to be 50-80 mm, vacuumize to not more than 5*10 -3 Pa, introduce 50-100 sccm of argon (purity 99.99%), open the bias voltage and arc power, and perform plasma etching on the base body under the conditions of -100 to -150 V, duty cycle 40-80%, gas pressure 0.5-1 Pa, and current 70-90 A to remove impurities attached to the surface of the base body and improve the bonding force between the film layer and the base body;

[0100] Step 2: after the etching is completed, a bonding layer Cr is prepared on the bolt base body under the conditions of 0.5-1 Pa and a bias voltage of 50-250 V, which can eliminate internal stress and increase the bonding force between the coating and the base body, and the thickness of the bonding layer is about 500 nm;

[0101] Step 3: after the preparation of the bonding layer is completed, vacuumize to 3*10 -3 Pa-7*10 -3 Pa at room temperature-250°C, control the position of the base body to be opposite to the center of the target material, introduce a mixed gas of argon (purity 99.99%) and nitrogen (purity 99.99%), the flow rate ratio of argon and nitrogen is between 3:1 and 1:3, the gas pressure in the cavity is 0.6 Pa-4 Pa, open the radio frequency power, the sputtering power is 500-900 W, the sputtering time is 3-10 h, and an AlN piezoelectric functional layer is formed;

[0102] Step 4: after the preparation of the AlN piezoelectric functional layer is completed, deposit an electrode layer under the conditions of 0.25-1 Pa, 0-100 V bias voltage, and 0-80 A current, the electrode layer is selected from one of Ag, Ag-Cr, Ti, and high-temperature glue containing silver powder; after the preparation is completed, naturally cool to room temperature, and a high-temperature-resistant intelligent bolt that can excite multiple ultrasonic waves is obtained.

[0103] Figure 11The ultrasonic echo signal diagram of the AlN thin film prepared on the bolt base using the deposition condition of the AlN piezoelectric functional layer of Example 7 and annealed at 800℃ for 1-200h. It can be seen that the AlN thin film on the bolt excited obvious four bottom surface ultrasonic echo signals, the amplitude of the echo signal gradually decreased, and the excited ultrasonic wave was ultrasonic longitudinal wave. After annealing at 800℃ for 200h, the amplitude of the bolt ultrasonic echo signal was weak, but the amplitude of the ultrasonic echo signal could be amplified by adjusting the gain of the ultrasonic measurement equipment. Therefore, the AlN thin film prepared in this paper has good temperature resistance, and can still excite ultrasonic waves after annealing at 800℃ for 200h, and can be used stably for a long time.

[0104] The above application example only takes the bolt base as an example, and the preparation method of the AlN piezoelectric coating material is also applicable to stainless steel, aluminum, hard alloy, high-speed steel, titanium and other bases, which are not limited here.

[0105] The above is only the preferred embodiment of the present application, and does not limit the implementation and protection scope of the present application. Those skilled in the art should be able to realize that any equivalent replacement and obvious changes made according to the content of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing a high-temperature resistant AlN piezoelectric coating material capable of exciting various ultrasonic waves, characterized in that, include: An AlN piezoelectric functional layer is formed on the substrate surface by magnetron sputtering using an Al target. In the magnetron sputtering process, the sputtering temperature is 60~250℃, the target-substrate distance is 40~80mm, a mixed gas of argon and nitrogen with a volume ratio of 3:1~1:2 is introduced into the cavity to a pressure of 1.0~2.8Pa, the sputtering power is 800~900W, and the deposition time is 8~10h. The growth orientation of the AlN piezoelectric functional layer on the substrate surface includes (002) diffraction crystal plane, (100) diffraction crystal plane, (101) diffraction crystal plane and (102) diffraction crystal plane; when excited, the AlN piezoelectric coating material can simultaneously emit a combined longitudinal wave and a transverse wave, which can be used for bolt preload detection, or for defect detection and stress measurement of steel plates, welds and steel pipes.

2. The preparation method according to claim 1, characterized in that, The Al target has a diameter of 100-160 mm and a thickness of 4-8 mm.

3. The preparation method according to claim 1, characterized in that, First, a bonding layer is deposited on the surface of the substrate, then an AlN piezoelectric functional layer is deposited on the surface of the bonding layer, and finally an electrode layer is deposited on the surface of the AlN piezoelectric functional layer.

4. The preparation method according to claim 1, characterized in that, Includes the following steps: S1. Control the distance between the target and the substrate to be 40~80mm, and perform plasma etching on the substrate surface in a vacuum and argon environment at 60~250℃. S2. A Cr bonding layer is deposited on the surface of the substrate after plasma etching at a bias voltage of 50-250V and a pressure of 0.5-1Pa. S3. An AlN piezoelectric functional layer is formed on the surface of the Cr bonding layer by magnetron sputtering; S4. Deposit an electrode layer on the surface of the AlN piezoelectric functional layer to complete the preparation of the AlN piezoelectric coating material.

5. The preparation method according to claim 4, characterized in that, In step S3, the electrode layer is selected from one of Cr, Ti, Ag, Ag-Cr, and high-temperature adhesive containing silver powder.

6. A high-temperature resistant AlN piezoelectric coating material capable of exciting various ultrasonic waves, characterized in that, The AlN piezoelectric coating material, prepared by any one of claims 1-5, comprises a bonding layer, an AlN piezoelectric functional layer, and an electrode layer.

7. The high-temperature resistant AlN piezoelectric coating material capable of exciting various ultrasonic waves according to claim 6, characterized in that, The high-temperature resistant AlN piezoelectric coating material, after being heat-treated and annealed at 800℃ for 200h, showed no change in its surface morphology and still maintained its ultrasonic excitation performance.

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