High-temperature-resistant ultrasonic probe and preparation method thereof

Abstract

The invention relates to a high-temperature-resistant ultrasonic probe and a preparation method thereof, and the high-temperature-resistant ultrasonic probe comprises an ultra-high-temperature piezoelectric element formed by bismuth scandate-based composite ceramic, a thermal protection layer coating the outer surface of the ultra-high-temperature piezoelectric element, and a gradient matching layer arranged on the radiation surface side of the ultra-high-temperature piezoelectric element, the heat sink backing layer is arranged on the non-radiating surface side of the ultra-high-temperature piezoelectric element; the high-temperature-resistant electrode is in ohmic contact with the ultra-high-temperature piezoelectric element; the thermal protection layer comprises a boron nitride-based composite coating, the thickness of the thermal protection layer is 0.2-0.5 mm, the heat conductivity coefficient is smaller than or equal to 5 W / (m.K), and the matching degree of the thermal expansion coefficient and the ultra-high-temperature piezoelectric element is larger than or equal to 95%. The gradient matching layer is made of an aluminum oxide-silicon carbide gradient composite material; the heat sink backing layer is made of a tungsten copper alloy material and is provided with a cooling channel; and the high-temperature-resistant electrode is formed by compounding a platinum-rhodium alloy wire and high-temperature conductive ceramic. The temperature limitation of a traditional ultrasonic probe in steelmaking application is broken through through material system innovation, structure innovation and process innovation.

Description

Technical Field

[0001] This invention belongs to the field of metallurgy, specifically relating to a high-temperature resistant ultrasonic probe and its preparation method, which can be applied in the smelting, refining and non-destructive testing of high-temperature melts such as molten steel. Background Technology

[0002] Ultrasonic waves, due to their unique cavitation and acoustic flow effects, are an important technology for improving the purity of molten steel and other metal melts and improving their solidification structure. They are also a high-precision detection method with broad industrial application prospects. However, traditional ultrasonic probes have many limitations in high-temperature environments, mainly in the following aspects: (1) Insufficient high-temperature resistance: Traditional ultrasonic probes are mostly made of materials such as polyethylene and ordinary piezoelectric ceramics (such as lead zirconate titanate). In high-temperature environments (such as steelmaking molten steel temperature > 1500℃), they are prone to thermal expansion mismatch, elastic degradation, or even melting, leading to probe failure. At the same time, the Curie temperature of conventional piezoelectric ceramics is usually below 400℃, and the piezoelectric performance decreases significantly at high temperatures, making it impossible to stably generate ultrasonic signals. (2) Limited acoustic performance: In high-temperature environments, the propagation characteristics of ultrasonic waves will change, leading to increased attenuation and scattering of sound waves. The penetration ability and resolution of traditional ultrasonic probes in high-temperature environments are severely affected. (3) Heat dissipation and cooling problems: Ultrasonic probes in high-temperature environments require effective heat dissipation and cooling measures to prevent overheating of the probe. Existing probes mostly use passive heat dissipation, which has low heat dissipation efficiency and cannot meet the needs of long-term, high-frequency detection. (4) Unreasonable structural design: The traditional ultrasonic probe structure design fails to fully consider the special requirements of high-temperature environments, resulting in insufficient stability and reliability of the probe at high temperatures. For example, the installation and disassembly of the probe are cumbersome, and the cooling device is not an integral structure with the probe, making it more troublesome to use. Based on the above points, the operating temperature of existing high-temperature probes is no more than 800℃, the continuous working time is extremely short, and they rely on external cooling systems, making it difficult to meet the application needs of extreme environments such as steelmaking.

[0003] The Chinese patent document CN116698991A discloses "An ultrasonic probe for high-temperature non-destructive testing and a method for manufacturing the high-temperature resistant matching layer thereof". It adopts a four-layer matching layer structure composed of metal-high-temperature resistant adhesive-metal-high-temperature resistant adhesive to improve the acoustic performance of ultrasonic waves. However, the probe is difficult to withstand high-temperature environments above 1600℃.

[0004] Chinese patent CN109604539B, entitled "Ultrasonic Vibration Device Suitable for Processing Molten Cast Iron," addresses the problems of severe probe corrosion and ceramic cracking by wrapping a cooling pipe around a titanium probe and circulating cooling water through it. While this method is simple and easy to implement, it still suffers from a short probe lifespan, and the circulation of cooling water within the pipes can easily lead to safety accidents. Summary of the Invention

[0005] This invention aims to provide a high-temperature resistant ultrasonic probe and its preparation method. Through innovative material system (bismuth layered piezoelectric ceramic + gradient SiC protective layer), structural innovation (channel active cooling), and process innovation (discharge plasma sintering + vacuum brazing), it breaks through the temperature limitations of traditional ultrasonic probes in steelmaking applications.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A high-temperature resistant ultrasonic probe includes an ultra-high temperature piezoelectric element made of bismuth scandate (BiScO3)-based composite ceramic, a heat protection layer covering the outer surface of the ultra-high temperature piezoelectric element, a gradient matching layer disposed on the radiating side of the ultra-high temperature piezoelectric element, a heat sink backing layer disposed on the non-radiating side of the ultra-high temperature piezoelectric element, and a high-temperature resistant electrode forming an ohmic contact with the ultra-high temperature piezoelectric element. The heat protection layer comprises a boron nitride-based composite coating, the thickness of the heat protection layer is 0.2–0.5 mm, the thermal conductivity is ≤5 W / (m·K), and the thermal expansion coefficient matches the ultra-high temperature piezoelectric element by ≥95%. The gradient matching layer is made of alumina-silicon carbide gradient composite material. The heat sink backing layer is made of tungsten-copper alloy material and has cooling channels. The high-temperature resistant electrode is made of platinum-rhodium alloy wire and high-temperature conductive ceramic composite.

[0008] Furthermore, the specific composition of the ultra-high temperature piezoelectric element is as follows: BiScO3 matrix: 70wt%~85wt%; Ta2O5 high-temperature stabilizer: 3wt%~8wt%; nano-cubic boron nitride (c-BN) reinforcing phase: 5wt%~20wt%; rare earth oxide Yb2O3 / Sm2O co-doperant: 0.5wt%~2wt%; the Curie temperature of the ultra-high temperature piezoelectric element is ≥1650℃, and the piezoelectric constant d at 1600℃ is... 33 ≥30pC / N.

[0009] Furthermore, the gradient matching layer has a four-layer structure, and the material composition of each layer according to the direction of sound wave propagation is as follows: First layer: Al2O3 80~85 vol% + SiC 15~20 vol%, thickness 0.8~1.2 mm; Second layer: Al2O3 60~65 vol% + SiC 35~40 vol%, thickness 0.6~0.8 mm; Third layer: Al2O3 40~45 vol% + SiC 55~60 vol%, thickness 0.4~0.6 mm; Fourth layer: SiC 90~95 vol% + Y2O3 5~10 vol%, thickness 0.2~0.4 mm; The layers are metallurgically bonded by plasma spraying.

[0010] Furthermore, the diameter of the cooling channel is 2-3 mm; the cooling medium is at least one of argon and helium, and the flow rate is controlled at 5-10 m / s.

[0011] Furthermore, the high-temperature resistant electrode comprises: a cylindrical electrode body with a diameter of 0.5-1 mm, containing 80-85 wt% Pt and 15-20 wt% Rh; and an interface transition layer composed of ZrO2-Y2O3 conductive ceramic with a thickness of 50-100 μm.

[0012] A method for preparing a high-temperature resistant ultrasonic probe, comprising the following steps:

[0013] 1) Fabrication of ultra-high temperature piezoelectric components:

[0014] The mixed raw materials were sintered using a spark plasma sintering process, and held at 1200–1350℃ and 50–80MPa for 10–30 minutes.

[0015] Perform step-polarization treatment:

[0016] First stage: Apply an electric field of 6~8kV / mm at 600~650℃ and maintain it for 25~30 minutes;

[0017] Second stage: Cool down to 350-400℃ at a rate of 2-5℃ / min, and reduce the electric field to 3-5kV / mm;

[0018] Third stage: After holding at 350~400℃ for 2 hours, allow to cool naturally;

[0019] 2) Preparation of gradient matching layer:

[0020] A multi-gun plasma spraying system is used to achieve four-layer gradient deposition through real-time composition control; the substrate preheating temperature is maintained at 800-850℃ during each layer deposition; laser remelting is used between layers with a power density of 15-20 J / mm².

[0021] 3) Processing the heat sink backing layer:

[0022] Selective laser melting technology was used to form a tungsten-copper alloy matrix with a copper content of 15-25 vol%; micro-electrical discharge machining was used to form cooling channels, and the surface roughness of the cooling channels (6) was between 2.8 and 3.2 μm.

[0023] 4) Overall assembly:

[0024] The assembly of each layer of the structure is completed in a vacuum brazing furnace at a brazing temperature of 950–1000℃; an axial pressure of 0.5–1 MPa is applied and the holding time is 30–60 minutes; finally, hot isostatic pressing is performed at 1000–1100℃ and 100–120 MPa for 1.5–2 hours.

[0025] Furthermore, in step 1), the discharge plasma sintering is performed using a pulsed current mode with a pulse frequency of 100–500 Hz, a duty cycle of 60%–80%, and a heating rate of 200–300 °C / min.

[0026] Furthermore, in step 2), the plasma spraying parameters include: main gas flow rate: Ar: 40-50 SLPM, H2: 10-15 SLPM; spraying distance: 80-120 mm; particle velocity: 400-600 m / s; interlayer temperature difference control ≤30℃.

[0027] Furthermore, in step 4), the vacuum brazing uses Au-Ni solder with a composition of 80~82wt% Au + 18~20wt% Ni and a solder layer thickness of 50~80μm; the hot isostatic pressing process uses argon gas as the medium and the heating and cooling rate is ≤5℃ / min.

[0028] Furthermore, it also includes a post-processing step: depositing a 2-5 μm thick amorphous silicon carbide coating on the probe surface at a deposition temperature of 650-700℃.

[0029] Specifically, the present invention achieves its objective through the following design:

[0030] Ultra-high temperature piezoelectric element: Bismuth scandate (BiScO3) based composite ceramic is used as the material for the piezoelectric element. This material has a high Curie temperature (≥1650℃) and good piezoelectric properties (piezoelectric constant d at 1600℃). 33 (≥30pC / N) to ensure the stability and reliability of the probe in high-temperature environments.

[0031] Thermal protection layer: A boron nitride-based composite coating that covers the outer surface of ultra-high temperature piezoelectric components. It has a low thermal conductivity (≤5W / (m·K)) and a high thermal expansion coefficient matching degree (≥95%), effectively protecting piezoelectric components from high temperature and extending their service life.

[0032] Gradient matching layer: A four-layer structure composed of alumina-silicon carbide gradient composite material, which realizes a continuous transition of acoustic impedance and improves the transmission efficiency of sound waves.

[0033] Heat sink backing layer: Made of tungsten copper alloy material and equipped with channel cooling structure, it effectively dissipates heat through the flow of cooling medium (argon and helium) to ensure stable operation of the probe in high-temperature environment.

[0034] High-temperature resistant electrode: Made of platinum-rhodium alloy wire and high-temperature conductive ceramic composite, ensuring good electrical contact between the electrode and the piezoelectric element, with a contact resistance ≤0.1Ω·cm. 2 (at 1600℃).

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] 1) High temperature stability: The high temperature resistant ultrasonic probe of the present invention can work stably in high temperature environments above 1600℃, which significantly improves the high temperature adaptability of the probe and meets the needs of high temperature non-destructive testing.

[0037] 2) High detection accuracy: Through the design of the gradient matching layer, a continuous transition of acoustic impedance is achieved, which improves the transmission efficiency of sound waves and improves the attenuation of the sound field.

[0038] 3) Excellent heat dissipation performance: The channel cooling structure design of the heat sink backing layer effectively dissipates heat, ensuring stable operation of the probe in high-temperature environments and extending the service life of the probe.

[0039] 4) Reliable electrical performance: The high-temperature resistant electrode design ensures good electrical contact between the electrode and the piezoelectric element, resulting in low contact resistance.

[0040] 5) Compact structure: The probe structure of the present invention is compact, and each layer is tightly combined through advanced manufacturing process to ensure the overall stability and reliability of the probe.

[0041] In summary, the high-temperature resistant ultrasonic probe of the present invention is suitable for energy input and non-destructive testing in various high-temperature environments. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the structure of a high-temperature resistant ultrasonic probe according to the present invention.

[0043] In the figure: 1. Ultra-high temperature piezoelectric element; 2. Thermal protection layer; 3. Gradient matching layer; 4. Heat sink backing layer; 5. High temperature resistant electrode; 6. Cooling channel; 7. Electrode body; 8. Interface transition layer. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the specific implementation methods of this invention will be further described below in conjunction with the embodiments. The following embodiments are used to specifically illustrate the content of this invention. These embodiments are only general descriptions of the content of this invention and do not limit the content of this invention.

[0045] See Figure 1A high-temperature resistant ultrasonic probe includes an ultra-high temperature piezoelectric element 1 made of bismuth scandate (BiScO3)-based composite ceramic, a heat protection layer 2 covering the outer surface of the ultra-high temperature piezoelectric element 1, a gradient matching layer 3 disposed on the radiating side of the ultra-high temperature piezoelectric element 1, a heat sink backing layer 4 disposed on the non-radiating side of the ultra-high temperature piezoelectric element 1, and a high-temperature resistant electrode 5 forming an ohmic contact with the ultra-high temperature piezoelectric element 1; the heat protection layer 2 comprises a boron nitride-based composite coating, the thickness of the heat protection layer 20 is 0.2-0.5 mm, the thermal conductivity is ≤5 W / (m·K), and the thermal expansion coefficient matches the ultra-high temperature piezoelectric element 1 by ≥95%; the gradient matching layer 3 is made of alumina-silicon carbide gradient composite material; the heat sink backing layer 4 is made of tungsten copper alloy material and has cooling channels 6; the high-temperature resistant electrode 5 is made of platinum-rhodium alloy wire and high-temperature conductive ceramic composite.

[0046] Furthermore, the specific composition of the ultra-high temperature piezoelectric element 1 is as follows: BiScO3 matrix: 70wt%~85wt%; Ta2O5 high temperature stabilizer: 3wt%~8wt%; nano-cubic boron nitride (c-BN) reinforcing phase: 5wt%~20wt%; rare earth oxide Yb2O3 / Sm2O3 co-doperant: 0.5wt%~2wt%; the Curie temperature of the ultra-high temperature piezoelectric element (1) is ≥1650℃, and the piezoelectric constant d at 1600℃ is... 33 ≥30pC / N.

[0047] Furthermore, the gradient matching layer 3 has a four-layer structure, and the material composition of each layer according to the direction of sound wave propagation is as follows: First layer: Al2O3 80~85 vol% + SiC 15~20 vol%, thickness 0.8~1.2 mm; Second layer: Al2O3 60~65 vol% + SiC 35~40 vol%, thickness 0.6~0.8 mm; Third layer: Al2O3 40~45 vol% + SiC 55~60 vol%, thickness 0.4~0.6 mm; Fourth layer: SiC 90~95 vol% + Y2O3 5~10 vol%, thickness 0.2~0.4 mm; The layers are metallurgically bonded by plasma spraying.

[0048] Furthermore, the cooling channel 6 has a diameter of 2-3 mm; the cooling medium is at least one of argon and helium, and the flow rate is controlled at 5-10 m / s.

[0049] Furthermore, the high-temperature resistant electrode 5 includes: a cylindrical electrode body 7 with a diameter of 0.5-1 mm, containing 80-85 wt% Pt and 15-20 wt% Rh; and an interface transition layer 8 composed of ZrO2-Y2O3 conductive ceramic with a thickness of 50-100 μm.

[0050] A method for preparing a high-temperature resistant ultrasonic probe, comprising the following steps:

[0051] 1) Fabrication of ultra-high temperature piezoelectric element 1:

[0052] The mixed raw materials were sintered using a spark plasma sintering process, and held at 1200–1350℃ and 50–80MPa for 10–30 minutes.

[0053] Perform step-polarization treatment:

[0054] First stage: Apply an electric field of 6~8kV / mm at 600~650℃ and maintain it for 25~30 minutes;

[0055] Second stage: Cool down to 350-400℃ at a rate of 2-5℃ / min, and reduce the electric field to 3-5kV / mm;

[0056] Third stage: After holding at 350~400℃ for 2 hours, allow to cool naturally;

[0057] 2) Preparation of gradient matching layer 3:

[0058] A multi-gun plasma spraying system is used to achieve four-layer gradient deposition through real-time composition control; the substrate preheating temperature is maintained at 800-850℃ during each layer deposition; laser remelting is used between layers with a power density of 15-20 J / mm².

[0059] 3) Processing the heat sink backing layer 4:

[0060] Selective laser melting technology is used to form a tungsten-copper alloy matrix with a copper content of 15-25 vol%; micro-electrical discharge machining is used to form a cooling channel 6 with a surface roughness of 2.8-3.2 μm.

[0061] 4) Overall assembly:

[0062] The assembly of each layer of the structure is completed in a vacuum brazing furnace at a brazing temperature of 950–1000℃; an axial pressure of 0.5–1 MPa is applied and the holding time is 30–60 minutes; finally, hot isostatic pressing is performed at 1000–1100℃ and 100–120 MPa for 1.5–2 hours.

[0063] Furthermore, in step 1), the discharge plasma sintering is performed using a pulsed current mode with a pulse frequency of 100–500 Hz, a duty cycle of 60%–80%, and a heating rate of 200–300 °C / min.

[0064] Furthermore, in step 2), the plasma spraying parameters include: main gas flow rate: Ar: 40-50 SLPM, H2: 10-15 SLPM; spraying distance: 80-120 mm; particle velocity: 400-600 m / s; interlayer temperature difference control ≤30℃.

[0065] Furthermore, in step 4), the vacuum brazing uses Au-Ni solder with a composition of 80~82wt% Au + 18~20wt% Ni and a solder layer thickness of 50~80μm; the hot isostatic pressing process uses argon gas as the medium and the heating and cooling rate is ≤5℃ / min.

[0066] Furthermore, it also includes a post-processing step: depositing a 2-5 μm thick amorphous silicon carbide coating on the probe surface at a deposition temperature of 650-700℃.

[0067] Specifically, the present invention achieves its objective through the following design:

[0068] Ultra-high temperature piezoelectric element: Bismuth scandate (BiScO3) based composite ceramic is used as the material for the piezoelectric element. This material has a high Curie temperature (≥1650℃) and good piezoelectric properties (piezoelectric constant d at 1600℃). 33 (≥30pC / N) to ensure the stability and reliability of the probe in high-temperature environments.

[0069] Thermal protection layer: A boron nitride-based composite coating that covers the outer surface of ultra-high temperature piezoelectric components. It has a low thermal conductivity (≤5W / (m·K)) and a high thermal expansion coefficient matching degree (≥95%), effectively protecting piezoelectric components from high temperature and extending their service life.

[0070] Gradient matching layer: A four-layer structure composed of alumina-silicon carbide gradient composite material, which realizes a continuous transition of acoustic impedance and improves the transmission efficiency of sound waves.

[0071] Heat sink backing layer: Made of tungsten copper alloy material and equipped with channel cooling structure, it effectively dissipates heat through the flow of cooling medium (argon and helium) to ensure stable operation of the probe in high-temperature environment.

[0072] High-temperature resistant electrode: Made of platinum-rhodium alloy wire and high-temperature conductive ceramic composite, ensuring good electrical contact between the electrode and the piezoelectric element, with a contact resistance ≤0.1Ω·cm. 2 (at 1600℃).

[0073] Example 1:

[0074] 1. Probe structural parameters:

[0075] Ultra-high temperature piezoelectric element 1: BiScO3 matrix 70wt% + Ta2O5 8wt% + c-BN 20wt% + Yb2O3 / Sm2O3 2wt%, Curie temperature ≥1650℃, d at 1600℃ 33 =30pC / N.

[0076] Thermal protection layer 2: The material is a boron nitride-based composite coating with a thickness of 0.2 mm, a thermal conductivity of 5 W / (m·K), and a thermal expansion coefficient matching degree of 95%.

[0077] Gradient matching layer 3:

[0078] First layer: Al2O3 80 vol% + SiC 20 vol%, thickness 0.8 mm;

[0079] Second layer: Al2O3 60 vol% + SiC 40 vol%, thickness 0.6 mm;

[0080] Third layer: Al2O3 40 vol% + SiC 60 vol%, thickness 0.4 mm;

[0081] Fourth layer: SiC 90vol% + Y2O3 10vol%, thickness 0.2mm.

[0082] Cooling channel 6: 2mm in diameter, argon flow rate 5m / s.

[0083] High-temperature resistant electrode 5: Electrode body 7 diameter 0.5mm (Pt 80wt%+Rh 20wt%), interface transition layer 8 thickness 50μm.

[0084] 2. Preparation process parameters:

[0085] 1) Spark plasma sintering:

[0086] The sintering parameters were: 1200℃, 50MPa holding pressure for 10 min, pulse frequency of 100Hz, duty cycle of 60%, and heating rate of 200℃ / min. Then, a stepped polarization treatment was performed: First stage: applying a 6kV / mm electric field at 600℃ and holding for 30 minutes; Second stage: cooling to 350℃ at a rate of 2℃ / min, reducing the electric field to 5kV / mm; Third stage: holding at 400℃ for 2 hours followed by natural cooling.

[0087] 2) Plasma spraying:

[0088] A multi-gun plasma spraying system was employed to achieve four-layer gradient deposition through real-time composition control. Specific parameters were: main gas flow rate: Ar 40 SLPM + H2 10 SLPM; spraying distance: 80 mm; particle velocity: 400 m / s; interlayer temperature difference controlled at 30℃; and substrate preheating temperature maintained at 800℃ during each layer deposition. Laser remelting was used between layers at a power density of 15 J / mm². 2 ;

[0089] 3) Heat sink backing layer processing:

[0090] The copper content of the tungsten-copper alloy matrix is ​​15 vol%; the surface roughness of the cooling channel is 3.2 μm.

[0091] 4) Vacuum brazing:

[0092] The assembly of each layer of the structure was completed in a vacuum brazing furnace at a brazing temperature of 950℃. An axial pressure of 0.5MPa was applied, and the holding time was 30min. The brazing filler metal was Au82Ni18, and the thickness of the brazing filler layer was 50μm.

[0093] 5) Hot isostatic pressing:

[0094] The isostatic pressure parameters were maintained at 1000℃ and 100MPa for 1.5h, with a cooling rate of 5℃ / min.

[0095] 6) Post-processing:

[0096] A 2μm amorphous SiC coating was deposited on the probe surface at a deposition temperature of 650℃.

[0097] Example 2:

[0098] 1. Probe structural parameters:

[0099] Ultra-high temperature piezoelectric element 1: BiScO3 matrix 85wt% + Ta2O5 3wt% + c-BN 11.5wt% + Yb2O3 / Sm2O3 0.5wt%; Curie temperature ≥1700℃, d at 1600℃ 33 =35pC / N.

[0100] Thermal protection layer 2: The material is a boron nitride-based composite coating with a thickness of 0.5 mm, a thermal conductivity of 3 W / (m·K), and a thermal expansion coefficient matching degree of 98%.

[0101] Gradient matching layer 3:

[0102] First layer: Al2O3 85 vol% + SiC 15 vol%, thickness 1.2 mm;

[0103] Second layer: Al2O3 65 vol% + SiC 35 vol%, thickness 0.8 mm;

[0104] Third layer: Al2O3 45 vol% + SiC 55 vol%, thickness 0.6 mm;

[0105] Fourth layer: SiC 95vol% + Y2O3 5vol%, thickness 0.4mm.

[0106] Cooling channel 6: 3mm in diameter, helium flow rate 10m / s.

[0107] High-temperature resistant electrode 5: Electrode body 7 diameter 1mm (Pt 85wt% + Rh 15wt%), interface transition layer 8 thickness 100μm, contact resistance 0.05Ω·cm 2 (at 1600℃).

[0108] 2. Preparation process parameters:

[0109] 1) Spark plasma sintering:

[0110] The sintering parameters were 1350℃ and 80MPa for 30 minutes. The pulse frequency used during sintering was 500Hz, the duty cycle was 80%, and the heating rate was 300℃ / min. Then, a stepped polarization treatment was performed: First stage: an electric field of 8kV / mm was applied at 650℃ and held for 25 minutes; Second stage: the temperature was reduced to 400℃ at a rate of 2℃ / min, and the electric field was reduced to 3kV / mm; Third stage: the temperature was held at 350℃ for 2 hours and then allowed to cool naturally.

[0111] 2) Plasma spraying:

[0112] A multi-gun plasma spraying system was used to achieve four-layer gradient deposition through real-time composition control. The specific parameters were as follows: main gas flow rate: Ar 50 SLPM + H2 15 SLPM, spraying distance 120 mm, particle velocity 600 m / s, interlayer temperature difference controlled at 28℃, and substrate preheating temperature maintained at 850℃ during each layer deposition; interlayer laser remelting was used with a power density of 20 J / mm².

[0113] 3) Heat sink backing layer processing:

[0114] The copper content of the tungsten-copper alloy matrix is ​​25 vol%; the surface roughness of cooling channel 6 is 2.8 μm.

[0115] 4) Vacuum brazing:

[0116] The assembly of each layer of the structure was completed in a vacuum brazing furnace at a brazing temperature of 1000℃; an axial pressure of 1MPa was applied, and the holding time was 60min. The brazing filler metal was Au82Ni18, and the thickness of the brazing filler layer was 80μm.

[0117] 5) Hot isostatic pressing:

[0118] The isostatic pressure parameters were maintained at 1100℃ and 120MPa for 2 hours, with a cooling rate of 3℃ / min.

[0119] 6) Post-processing:

[0120] A 5μm amorphous SiC coating was deposited on the probe surface at a deposition temperature of 700℃.

[0121] Example 3:

[0122] 1. Probe structural parameters:

[0123] High-temperature piezoelectric element 1: BiScO3 matrix 85wt% + Ta2O5 8wt% + c-BN 5wt% + Yb2O3 / Sm2O3 2wt%; Curie temperature ≥1675℃, d at 1600℃ 33 =33pC / N.

[0124] Thermal protection layer 2:

[0125] The material is a boron nitride-based composite coating with a thickness of 0.35 mm, a thermal conductivity of 4 W / (m·K), and a thermal expansion coefficient matching degree of 96.5%.

[0126] Gradient matching layer 3:

[0127] First layer: Al2O3 82 vol% + SiC 18 vol%, thickness 1.02 mm;

[0128] Second layer: Al2O3 63 vol% + SiC 37 vol%, thickness 0.68 mm;

[0129] Third layer: Al2O3 44 vol% + SiC 56 vol%, thickness 0.51 mm;

[0130] Fourth layer: SiC 91 vol% + Y2O3 9 vol%, thickness 0.32 mm.

[0131] Cooling channel 6: 2.5 mm in diameter, argon-helium mixed gas flow rate 7.4 m / s.

[0132] High-temperature resistant electrode 5: Electrode body 7 diameter 0.75mm (Pt82wt%+Rh18wt%), interface transition layer 8 thickness 75μm.

[0133] 2. Preparation process parameters:

[0134] 1) Spark plasma sintering:

[0135] The sintering parameters were 1273℃ and 52MPa for 10 min, with a pulse frequency of 100Hz, a duty cycle of 61%, and a heating rate of 202℃ / min. Then, a stepped polarization treatment was performed: First stage: an electric field of 7kV / mm was applied at 620℃ and held for 28 minutes; Second stage: the temperature was reduced to 375℃ at a rate of 2℃ / min, and the electric field was reduced to 4kV / mm; Third stage: the temperature was held at 375℃ for 2 hours and then allowed to cool naturally.

[0136] 2) Plasma spraying:

[0137] A multi-gun plasma spraying system was used to achieve four-layer gradient deposition through real-time composition control. The specific parameters were as follows: main gas flow rate: Ar 45 SLPM + H2 12.5 SLPM, spraying distance: 82 mm, particle velocity: 412 m / s, interlayer temperature difference controlled at 30℃, and substrate preheating temperature maintained at 820℃ during each layer deposition; interlayer laser remelting was used with a power density of 18 J / mm².

[0138] 3) Processing of heat-sinking backing layer 4:

[0139] The copper content of the tungsten-copper alloy matrix is ​​18 vol%; the surface roughness of cooling channel 6 is 3.0 μm.

[0140] 4) Vacuum brazing:

[0141] The assembly of each layer of the structure was completed in a vacuum brazing furnace at a brazing temperature of 971℃. An axial pressure of 0.77MPa was applied, and the holding time was 46min. The brazing filler metal was Au82Ni18, and the thickness of the brazing filler layer was 64μm.

[0142] Hot isostatic pressing:

[0143] The isostatic pressure parameters were maintained at 1051℃ and 100MPa for 1.5h, with a cooling rate of 4℃ / min.

[0144] Post-processing:

[0145] A 3.3 μm amorphous SiC coating was deposited on the probe surface at a deposition temperature of 676 °C.

[0146] The ultrasonic probes described in Examples 1-3 were inserted into molten steel (Q235B) at temperatures of 1600, 1620, and 1650°C, respectively. The ultrasonic generator was turned on, and the frequency was adjusted to 30kHz and the power to 300W. The cavitation erosion of the probes was recorded. The values ​​in Table 1 represent the limit time for which the probes of Examples 1-3 did not cavitate in molten Q235B steel. It can be seen that the probes of Examples 1-3 can maintain cavitation erosion erosion for more than 1 hour at 1600 and 1620°C, and even at 1650°C, they can maintain cavitation erosion erosion erosion erosion for more than 50 minutes.

[0147] Table 1. Test results of the probe under high-temperature molten steel.

[0148] .

Claims

1. A high-temperature resistant ultrasonic probe, characterized in that, The device includes an ultra-high temperature piezoelectric element (1) made of bismuth scandate-based composite ceramic, a heat protection layer (2) covering the outer surface of the ultra-high temperature piezoelectric element (1), a gradient matching layer (3) disposed on the radiating side of the ultra-high temperature piezoelectric element (1), a heat sink backing layer (4) disposed on the non-radiating side of the ultra-high temperature piezoelectric element (1), and a high-temperature resistant electrode (5) forming an ohmic contact with the ultra-high temperature piezoelectric element (1); the heat protection layer (2) contains a boron nitride-based composite coating, the thickness of the heat protection layer (20) is 0.2-0.5 mm, the thermal conductivity is ≤5 W / (m·K), and the thermal expansion coefficient matches the ultra-high temperature piezoelectric element (1) with a degree of ≥95%; the gradient matching layer (3) is made of alumina-silicon carbide gradient composite material; the heat sink backing layer (4) is made of tungsten copper alloy material and is provided with cooling channels (6); the high-temperature resistant electrode (5) is made of platinum-rhodium alloy wire and high-temperature conductive ceramic composite.

2. The high-temperature resistant ultrasonic probe according to claim 1, characterized in that, The specific composition of the ultra-high temperature piezoelectric element (1) is as follows: BiScO3 matrix: 70wt%~85wt%; Ta2O5 high temperature stabilizer: 3wt%~8wt%; nano-cubic boron nitride (c-BN) reinforcing phase: 5wt%~20wt%; rare earth oxide Yb2O3 / Sm2O3 co-doperant: 0.5wt%~2wt%; the Curie temperature of the ultra-high temperature piezoelectric element (1) is ≥1650℃, and the piezoelectric constant d at 1600℃ is... 33 ≥30pC / N.

3. The high-temperature resistant ultrasonic probe according to claim 1, characterized in that, The gradient matching layer (3) has a four-layer structure, and the material composition of each layer according to the direction of sound wave propagation is as follows: First layer: Al2O3 80~85vol% + SiC 15~20vol%, thickness 0.8~1.2mm; Second layer: Al2O3 60~65vol% + SiC 35~40vol%, thickness 0.6~0.8mm; Third layer: Al2O3 40~45vol% + SiC 55~60vol%, thickness 0.4~0.6mm; Fourth layer: SiC 90~95 vol% + Y2O3 5~10 vol%, thickness 0.2~0.4 mm.

4. The high-temperature resistant ultrasonic probe according to claim 1, characterized in that, The cooling channel (6) has a diameter of 2-3 mm; the cooling medium is at least one of argon and helium, and the flow rate is controlled at 5-10 m / s.

5. A high-temperature resistant ultrasonic probe according to claim 1, characterized in that, The high-temperature resistant electrode (5) includes: a cylindrical electrode body (7) with a diameter of 0.5-1 mm, containing 80-85 wt% Pt and 15-20 wt% Rh; and an interface transition layer (8) composed of ZrO2-Y2O3 conductive ceramic with a thickness of 50-100 μm.

6. A method for preparing a high-temperature resistant ultrasonic probe as described in any one of claims 1-5, characterized in that, Including the following steps: 1) Fabrication of ultra-high temperature piezoelectric components (1): The mixed raw materials were sintered using a spark plasma sintering process, and held at 1200–1350℃ and 50–80MPa for 10–30 minutes. Perform step-polarization treatment: First stage: Apply an electric field of 6~8kV / mm at 600~650℃ and maintain it for 25~30 minutes; Second stage: Cool down to 350-400℃ at a rate of 2-5℃ / min, and reduce the electric field to 3-5kV / mm; Third stage: After holding at 350~400℃ for 2 hours, allow to cool naturally; 2) Prepare gradient matching layer (3): A multi-gun plasma spraying system was employed to achieve four-layer gradient deposition through real-time composition control; the substrate preheating temperature was maintained at 800–850℃ during each layer deposition; laser remelting was used between layers, with a power density of 15–20 J / mm². 2 ; 3) Processing the heat sink backing layer (4): The tungsten-copper alloy matrix is ​​formed by selective laser melting technology with a copper content of 15-25 vol%; the cooling channel (6) is formed by micro-electrical discharge machining, and the surface roughness of the cooling channel (6) is between 2.8 and 3.2 μm. 4) Overall assembly: The assembly of each layer of the structure is completed in a vacuum brazing furnace at a brazing temperature of 950–1000℃; an axial pressure of 0.5–1 MPa is applied and the holding time is 30–60 minutes; finally, hot isostatic pressing is performed at 1000–1100℃ and 100–120 MPa for 1.5–2 hours.

7. The method for preparing a high-temperature resistant ultrasonic probe according to claim 6, characterized in that, In step 1), the discharge plasma sintering is performed in pulsed current mode with a pulse frequency of 100-500 Hz, a duty cycle of 60%-80%, and a heating rate of 200-300 °C / min.

8. The method for preparing a high-temperature resistant ultrasonic probe according to claim 6, characterized in that, Step 2) Plasma spraying parameters include: main gas flow rate: Ar: 40~50 SLPM, H2: 10~15 SLPM; spraying distance: 80~120mm; particle velocity: 400~600m / s; interlayer temperature difference control ≤30℃.

9. The method for preparing a high-temperature resistant ultrasonic probe according to claim 6, characterized in that, In step 4), vacuum brazing uses Au-Ni solder with a composition of 80~82wt% Au + 18~20wt% Ni and a solder layer thickness of 50~80μm. During hot isostatic pressing, argon gas is used as the medium and the heating and cooling rate is ≤5℃ / min.

10. The method for preparing a high-temperature resistant ultrasonic probe according to claim 6, characterized in that, It also includes a post-processing step: depositing a 2-5 μm thick amorphous silicon carbide coating on the probe surface at a deposition temperature of 650-700℃.

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