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CN-122007826-A - K-type thermocouple wire with high-temperature-resistant and oxidation-resistant coating and preparation method thereof

CN122007826ACN 122007826 ACN122007826 ACN 122007826ACN-122007826-A

Abstract

The invention provides a K-type thermocouple wire with a high-temperature-resistant and oxidation-resistant coating and a preparation method thereof, wherein the preparation method comprises the following steps of S1, adopting an argon arc welding process to weld a positive electrode thermocouple wire and a negative electrode thermocouple wire to obtain a thermocouple wire matrix; S2, carrying out sand blasting roughening treatment on the surface of a coupling wire matrix by adopting a sand blasting process to obtain a roughened coupling wire, S3, adding the roughened coupling wire into acetone for ultrasonic cleaning, then transferring into deionized water for cleaning, taking out, placing into a drying box for drying to obtain a pretreated coupling wire, S4, carrying out spraying treatment on the surface of the pretreated coupling wire by adopting an atmospheric plasma spraying process to form a transition layer to obtain a coupling wire A, S5, carrying out spraying treatment on the surface of the coupling wire A by adopting an atmospheric plasma spraying process to form a ceramic layer to obtain a coupling wire B, and S6, carrying out hole sealing treatment on the surface of the coupling wire B to form a SiO2 hole sealing layer to obtain the K-type thermocouple wire with a high-temperature-resistant and oxidation-resistant coating. The K-type thermocouple wire prepared by the invention has better oxidation resistance, thermal shock resistance and longer service life.

Inventors

  • CHEN XIAOJIE
  • LIU XIAOGANG
  • LIU JIA

Assignees

  • 苏州航制领航测控技术有限公司

Dates

Publication Date
20260512
Application Date
20260407

Claims (9)

  1. 1. A preparation method of a K-type thermocouple wire with a high-temperature-resistant and oxidation-resistant coating is characterized by comprising the following steps: s1, welding an anode dipole wire and a cathode dipole wire by adopting an argon arc welding process to obtain a dipole wire matrix; S2, carrying out sand blasting roughening treatment on the surface of the even wire matrix obtained in the step S1 by adopting a sand blasting process to obtain roughened even wires; s3, adding the coarsened coupling yarn obtained in the step S2 into acetone for ultrasonic cleaning, then transferring into deionized water for cleaning, taking out, and then placing into a drying oven for drying to obtain a pretreated coupling yarn; S4, spraying the surface of the pretreated coupling yarn obtained in the step S3 by adopting an atmospheric plasma spraying process to form a transition layer so as to obtain a coupling yarn nail; s5, spraying the surface of the even silk first obtained in the step S4 by adopting an atmospheric plasma spraying process to form a ceramic layer so as to obtain even silk second; S6, carrying out hole sealing treatment on the surface of the coupling wire II obtained in the step S5 to form a SiO 2 hole sealing layer, and obtaining the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating.
  2. 2. The preparation method of the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating is characterized in that in the step S1, an anode dipole wire is a NiCr dipole wire, a cathode dipole wire is a NiSi dipole wire, the diameters of the NiCr dipole wire and the NiSi dipole wire are 2.45mm, the lengths of the NiCr dipole wire and the NiSi dipole wire are 800mm, a direct-current TIG welding machine is adopted in an argon arc welding process, the diameter of a cerium tungsten electrode is 1.6mm, shielding gas is argon with the flow rate of 12L/min, the welding current is 10-15V, the welding time is 1 second, the extension length of the cerium tungsten electrode is 6mm, the tip angle of the cerium tungsten electrode is 35 degrees, the welding gun angle is 75 degrees, the diameter of a welding spot is 3-4mm, and the shape of a welding ball is spherical.
  3. 3. The method for preparing K-type thermocouple wires with high temperature resistant and oxidation resistant coatings according to claim 1, wherein in the step S2, the sand blasting medium adopted in the sand blasting process is glass beads with the diameter of 0.3mm, the sand blasting pressure is 0.3Mpa, the sand blasting distance is 80mm, the sand blasting angle is 45 degrees, and the surface roughness Ra of the roughened thermocouple wires is 3.2-6.3 μm.
  4. 4. The method for preparing the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating according to claim 1, wherein in the step S3, the power of ultrasonic cleaning is 200-300W, the time of ultrasonic cleaning is 10-15min, the time of deionized water cleaning is 10-15min, the drying temperature is 100 ℃, and the drying time is 1-2h.
  5. 5. The method for preparing the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating according to claim 1, wherein in the step S4, spraying powder adopted by an atmospheric plasma spraying process is Ni20Cr powder with the particle size of 2-5 mu m, spraying current is 400-600A, spraying voltage is 50-70V, main gas is argon with the flow rate of 40-60L/min, auxiliary gas is helium with the flow rate of 6-10L/min, spraying distance is 100-150mm, and thickness of a transition layer is 20-50 mu m.
  6. 6. The method for preparing the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating according to claim 1, wherein in the step S5, spraying powder adopted by an atmospheric plasma spraying process is Al 2 O 3 powder with the particle size of 2-5 mu m, spraying current is 500-700A, spraying voltage is 65-80V, main gas is argon with the flow rate of 50-70L/min, auxiliary gas is hydrogen with the flow rate of 8-12L/min, spraying distance is 120-180mm, and thickness of a ceramic layer is 100-200 mu m.
  7. 7. The method for preparing the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating, which is disclosed in claim 1, is characterized in that in the step S6, the hole sealing treatment process comprises the steps of uniformly mixing ethyl orthosilicate, deionized water, ethanol and 4-oxo-ethyl cyclohexanecarboxylate to obtain a mixed solution, adding hydrochloric acid into the mixed solution to adjust the pH value to 4, aging for 1-2 hours to obtain a hole sealing solution, immersing the even wire B obtained in the step S5 into the hole sealing solution, standing for 1-2 hours, taking out, transferring into a muffle furnace, heating to 400-600 ℃, preserving heat for 30-40 minutes, taking out, naturally cooling to room temperature, and obtaining the SiO 2 hole sealing layer with the thickness of 40-50 mu m.
  8. 8. The method for preparing the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating, which is disclosed in claim 7, is characterized in that in the hole sealing treatment process, the concentration of hydrochloric acid is 0.1mol/L, the volume ratio of tetraethoxysilane, deionized water, ethanol and 4-oxo-ethyl cyclohexanecarboxylate is 1 (1-2): 2-3): 0.1-0.2, and the temperature rising rate of a muffle furnace is 5 ℃ per minute.
  9. 9. The K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating, which is prepared by the preparation method according to claims 1-8.

Description

K-type thermocouple wire with high-temperature-resistant and oxidation-resistant coating and preparation method thereof Technical Field The invention relates to a thermocouple wire, in particular to a K-type thermocouple wire with a high-temperature-resistant and oxidation-resistant coating and a preparation method thereof. Background Type K thermocouples (NiCr-NiSi) are the most widely used thermocouple types in industry today, typically ranging from-200 ℃ to +1200 ℃. However, when the use temperature exceeds 800 ℃ and is in an oxidizing atmosphere (e.g., air, oxygen-containing combustion atmosphere), severe oxidation of the surface of the positive and negative electrode alloy wires occurs, resulting in loose oxide films, leading to: 1) Alloy elements are selectively oxidized and volatilized, so that alloy components are changed; 2) The oxide film is peeled off to cause pollution of a hot junction; 3) After long-term use, the thermoelectric voltage drifts, and the measurement error is increased; 4) The mechanical strength is reduced, and fracture is easy to occur. The prior solution comprises the steps of selecting thicker coupling wires, using noble metal thermocouples, adopting a sealing protection sleeve and the like, but the problems of low response speed, high cost, complex structure and the like respectively exist. Disclosure of Invention The invention aims to provide a preparation method of a K-type thermocouple wire with a high-temperature-resistant and oxidation-resistant coating, and the K-type thermocouple wire prepared by the preparation method has good oxidation resistance, thermal shock resistance and long service life. In order to solve the technical problems, the technical scheme of the invention is as follows: a preparation method of a K-type thermocouple wire with a high-temperature-resistant and oxidation-resistant coating comprises the following steps: s1, welding an anode dipole wire and a cathode dipole wire by adopting an argon arc welding process to obtain a dipole wire matrix; S2, carrying out sand blasting roughening treatment on the surface of the even wire matrix obtained in the step S1 by adopting a sand blasting process to obtain roughened even wires; s3, adding the coarsened coupling yarn obtained in the step S2 into acetone for ultrasonic cleaning, then transferring into deionized water for cleaning, taking out, and then placing into a drying oven for drying to obtain a pretreated coupling yarn; S4, spraying the surface of the pretreated coupling yarn obtained in the step S3 by adopting an atmospheric plasma spraying process to form a transition layer so as to obtain a coupling yarn nail; s5, spraying the surface of the even silk first obtained in the step S4 by adopting an atmospheric plasma spraying process to form a ceramic layer so as to obtain even silk second; S6, carrying out hole sealing treatment on the surface of the coupling wire II obtained in the step S5 to form a SiO 2 hole sealing layer, and obtaining the K-type thermocouple wire with the high-temperature-resistant and oxidation-resistant coating. Further, in the step S1, the positive electrode dipole wire is a NiCr dipole wire, the negative electrode dipole wire is a NiSi dipole wire, the diameters of the NiCr dipole wire and the NiSi dipole wire are 2.45mm, the lengths of the NiCr dipole wire and the NiSi dipole wire are 800mm, the argon arc welding process adopts a direct-current TIG welding machine, the diameter of a cerium tungsten electrode is 1.6mm, shielding gas is argon with the flow rate of 12L/min, the welding current is 10-15V, the welding time is 1 second, the extension length of the cerium tungsten electrode is 6mm, the tip angle of the cerium tungsten electrode is 35 degrees, the welding gun angle is 75 degrees, the diameter of a welding spot is 3-4mm, and the shape of a welding ball is a sphere. Further, in the step S2, the sand blasting process adopts glass beads with the diameter of 0.3mm as a sand blasting medium, the sand blasting pressure is 0.3Mpa, the sand blasting distance is 80mm, the sand blasting angle is 45 degrees, and the surface roughness Ra of the coarsened coupling wires is 3.2-6.3 mu m. The sand blasting process can enhance the interface bonding strength between the subsequent coating and the even wire matrix and prevent the coating from falling off. Further, in the step S3, the power of ultrasonic cleaning is 200-300W, the time of ultrasonic cleaning is 10-15min, the time of deionized water cleaning is 10-15min, the drying temperature is 100 ℃, and the drying time is 1-2h. Step S3 is a surface purification treatment step, so that the surface of the coupling wire is purified before the spraying step, and impurities are avoided, and the spraying effect is prevented from being influenced. Further, in the step S4, the spraying powder adopted in the atmospheric plasma spraying process is Ni20Cr powder with the particle size of 2-5 mu m, the spraying current is 400-600A, the sprayi