A double glow plasma nitriding treatment method for the inner surface of a titanium alloy round tube

Abstract

The present invention belongs to the technical field of metal materials and their processing, and discloses a treatment method for double glow plasma nitriding on the inner wall surface of a titanium alloy round tube, and obtains a TC4 round tube with a nitriding layer on the inner wall, which significantly improves the hardness and wear resistance of the inner wall of the TC4 titanium alloy round tube, prolongs the service life of the parts, and meets the urgent needs of modern industry for high wear-resistant parts. After cleaning, drying, vacuuming, double glow plasma nitriding, furnace cooling, and precise control of parameters such as heating rate, gas ratio and nitriding time, the thickness and performance of the nitriding layer are precisely controlled, ensuring the stability and repeatability of the treatment effect. The obtained TC4 round tube sample was tested, and the metallographic structure of the nitriding layer on the inner wall was closely combined with the matrix, with a small risk of falling off and a relatively thick layer thickness of up to 17±1µm, and an average hardness of up to 713.04HV, which can reach 2.2 times the hardness of the matrix.

Description

Technical Field

[0001] The invention relates to the technical field of metal materials and processing thereof, and in particular to a double glow plasma nitriding treatment method for the inner wall surface of a titanium alloy round tube. Background Art

[0002] Titanium and titanium alloys have been widely used in aviation, aerospace, military and other fields due to their excellent strength-to-weight ratio and good corrosion resistance. However, with the rapid development of modern industry, important components in different fields have put forward higher requirements on the wear resistance and service life of titanium alloys.

[0003] Traditional surface treatment technologies, such as thermal spraying, magnetron sputtering and laser cladding, can improve the surface properties of titanium alloys to a certain extent, but they generally have problems such as insufficient coating stability, easy falling off or cracking, and high processing costs. They can hardly meet the current industry's urgent demand for high-quality, long-life wear-resistant coatings. Summary of the invention

[0004] The purpose of the present invention is to provide a double glow plasma nitriding treatment method for the inner wall surface of a titanium alloy round tube, wherein the inner wall surface of a TC4 round tube is subjected to plasma nitriding treatment to form a nitrided wear-resistant coating, so as to improve the wear resistance of TC4 titanium alloy shaft barrel parts.

[0005] To achieve the above-mentioned purpose, the solution of the present invention is: a treatment method for double glow plasma nitriding of the inner wall surface of a titanium alloy round tube, the equipment used in the treatment method is a double-layer glow ion metallization heat treatment furnace, the heat treatment furnace includes a furnace bottom plate and a hood-shaped furnace body, and the heat treatment furnace is connected with an opening and closing device, a power supply system, an atmosphere system, a glow device and a cooling system;

[0006] The processing method includes the following steps:

[0007] S1 processes the as-cast TC4 bar into TC4 round tube;

[0008] S2 Equipment installation: Open the furnace body through the opening and closing device set on the heat treatment furnace, and then evenly hoist the long tube with holes on the source platform in the furnace;

[0009] S3 Sample surface cleaning and coating: Wipe the inner wall of the TC4 round tube sample with acetone and alcohol and blow dry, then clean the outer wall of the TC4 round tube sample and apply anti-seepage coating;

[0010] S4 Vacuuming: Place the TC4 round tube sample after the above treatment into the heat treatment furnace; turn on the power, start the atmosphere system, and use the vacuum pump to evacuate the furnace until the vacuum pressure is less than 1Pa, and turn on the water cooling switch;

[0011] S5 Heating: Set the voltage to 750V, and gradually heat up the TC4 round tube sample in the furnace. When it is heated to 50℃, the gas switch of the atmosphere system is automatically turned on to pass argon. When the temperature rises to 60℃, set the gas pressure to 200Pa. Wait until the gas pressure in the furnace cannot rise and the sample temperature rises slowly, and pass argon and nitrogen at the same time, so that N2:Ar=3:1 in the furnace. Then adjust the control output knob to change the heating rate, and adjust the temperature until the sample temperature is 900℃±15℃.

[0012] S6 Double glow ion nitriding: ① Equipment parameters during stable operation: source voltage of glow system 750V, pressure 200Pa, N2:Ar=3:1; source control output 27.6%, current 30A; cathode control output 50.7%, current 24A; ② Double glow ion nitriding operation time: When the surface of TC4 round tube sample rises to 900℃, start timing for 8 hours;

[0013] S7 Cooling: ① After running for the required time, the voltage on both sides of the source and cathode return to 0, the gas flow rate returns to 0, and the control output knob is adjusted to the minimum; ② When the gas pressure is pumped to 100Pa, turn off the vacuum pump and keep the cooling water flowing until the sample is cooled to room temperature with the furnace.

[0014] Furthermore, the TC4 round tube has the following chemical elements by weight (wt%): Al: 6.01, V: 3.84, Fe: 0.30, C: 0.10, N: 0.05, O: 0.20, H: 0.015, Ti: 89, and the rest are impurities.

[0015] Further, after cooling is completed, sampling, cleaning and testing steps are performed, as follows:

[0016] S8 Sampling: After the temperature is lowered, open the vacuum valve to make the pressure in the furnace consistent with the atmospheric pressure, turn off the cooling water, open the furnace body, and take out the sample;

[0017] S9 Cleaning: Take out the TC4 round tube sample, clean it with clean water, and wipe off the special anti-seepage coating on the surface;

[0018] S10 Testing, analysis and characterization: Testing, analysis and characterization of the inner wall morphology, color, metallographic structure and mechanical properties of TC4 round tube samples; metallographic structure analysis using a metallographic microscope; hardness analysis using a Vickers hardness tester.

[0019] Furthermore, the as-cast TC4 rod is processed into a TC4 round tube with an outer diameter of 60 mm, an inner diameter of 30 mm and a length of 1100 mm by turning, boring and sawing.

[0020] Furthermore, during the equipment installation in step S2, a pre-customized round tube sleeve is prepared and placed on the cathode platform in the furnace.

[0021] Further, in step S4, the processed TC4 round tube sample is placed in a round tube sleeve in a heat treatment furnace, and a sample fixing ring is used to cooperate with the round tube sleeve to fix the TC4 round tube sample.

[0022] Furthermore, the power supply system includes a 50A power supply and a 75A power supply, and the 50A voltage stabilizer and the 75A voltage stabilizer matched with the power supply are respectively connected to the heat treatment furnace through wires.

[0023] Furthermore, the atmosphere system includes a vacuum pump, a high-purity argon gas bottle and a high-purity nitrogen gas bottle. The vacuum pump is provided with a vacuum pump outlet. A vacuum pump connecting pipe is provided between the vacuum pump and the heat treatment furnace. A vacuum breaking knob is provided on the vacuum pump connecting pipe. The furnace body is connected to different gas cylinders through a ventilation hose.

[0024] Furthermore, the glow device includes a source platform and a cathode platform located in the furnace, the source platform is connected to a 50A power supply wire; the cathode platform is connected to a 75A power supply wire.

[0025] Furthermore, the heat treatment furnace is provided with an observation hole connected to the furnace, a cooling water inlet and a cooling water outlet pipe;

[0026] The heat treatment furnace is also equipped with a thermometer to measure the real-time surface temperature of the samples in the furnace.

[0027] After adopting the above scheme, the beneficial effects of the present invention are:

[0028] The present invention performs double glow plasma nitriding treatment on the inner wall surface of the titanium alloy round tube to obtain a TC4 round tube with a nitrided layer on the inner wall, which significantly improves the hardness and wear resistance of the inner wall of the TC4 titanium alloy round tube, extends the service life of the parts, and meets the urgent needs of modern industry for high-wear-resistant parts.

[0029] After cleaning, drying, vacuuming, double glow plasma nitriding, and furnace cooling, and by precisely controlling parameters such as the heating rate, gas ratio, and nitriding time, the thickness and performance of the nitriding layer are precisely controlled, ensuring the stability and repeatability of the treatment effect. The TC4 round tube sample obtained has been tested and the metallographic structure of the nitriding layer on the inner wall is closely integrated with the matrix, with a low risk of falling off and a relatively thick layer thickness of up to 17±1µm, and an average hardness of up to 713.04HV, which is 2.2 times the hardness of the matrix.

[0030] In addition, before carburizing treatment, the sample surface was cleaned to ensure the cleanliness of the inner wall of the TC4 round tube, effectively preventing impurity contamination during the nitriding process and improving the quality of the nitriding layer. The outer wall of the sample was treated with anti-seepage coating to protect the non-nitriding area. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural diagram of the equipment used for double glow plasma nitriding treatment of the present invention;

[0032] Figure 2 This is a metallographic microstructure morphology of the inner wall of the TC4 round tube sample prepared by the present invention;

[0033] Figure 3 It is a hardness performance diagram of the inner wall of the TC4 round tube sample prepared by the present invention.

[0034] Description of reference numerals:

[0035] 1. High-purity argon gas cylinder; 2. High-purity nitrogen gas cylinder; 3. Control output display screen; 4. Gas pressure control display screen; 5. Temperature control display screen; 6. Nitrogen flow display screen; 7. Argon flow display screen; 8. Current indicator; 9. Voltage indicator; 10. Start control screen; 11. 50A power supply; 12. 50A voltage regulator; 13. Ventilation hose;

[0036] 14. Electric wire; 15. Vacuum pump connecting pipe; 16. Vacuum pump; 17. 75A voltage regulator; 18. 75A power supply; 19. Control output knob; 20. Current display screen; 21. Voltage fine-tuning knob; 22. Nitrogen gas flow control knob; 23. Voltage control knob; 24. Voltage indicator light; 25. Argon gas flow control knob; 26. Vacuum pump outlet; 27. Cooling water inlet; 28. Temperature measuring thermocouple; 29. ​​Furnace body; 30. Long tube with holes; 31. Round tube sleeve; 32. TC4 round tube sample; 33. Source platform; 34. Screw nut; 35. Screw; 36. Cathode platform; 37. Sample fixing ring; 38. Observation hole; 39. Cooling water outlet pipe; 40. Hydraulic lifting system; 41. Thermometer; 42. Infrared; 43. Vacuum breaking knob. DETAILED DESCRIPTION

[0037] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] The present embodiment provides a double glow plasma nitriding treatment method for the inner wall surface of a titanium alloy round tube. The treatment object is TC4 titanium alloy, and the chemical elements mass ratio (wt%) is: Al: 6.01, V: 3.84, Fe: 0.30, C: 0.10, N: 0.05, O: 0.20, H: 0.015, Ti: 89, and the rest are impurities.

[0039] The equipment used in this treatment method is a double-layer glow ion metallization heat treatment furnace, such as Figure 1As shown, the heat treatment furnace includes a furnace bottom plate and a hood-shaped furnace body 29. The furnace body 29 is provided with an observation hole 38 connected to the furnace, a cooling water inlet 27 and a cooling water outlet pipe 39. The cooling water flows in from the tap water pipe, passes through the furnace wall and is discharged after cooling, forming a cooling system. The heat treatment furnace is also connected to an opening and closing device, a power system, an atmosphere system and a glow device.

[0040] The opening and closing device includes a hydraulic lifting system 40 and a lead screw transmission mechanism. The hydraulic lifting system 40 provides power support, while the lead screw 35 and the lead screw nut 34 are precisely matched to achieve the opening and closing of the furnace body 29.

[0041] The power supply system includes a 50A power supply 11 and a 75A power supply 18, and the 50A voltage regulator 12 and the 75A voltage regulator 17 matched with the power supply are respectively connected to the heat treatment furnace through the wire 14. Here, the power supply system is provided with a control output display screen 3, a gas pressure control display screen 4, a temperature control display screen 5, a nitrogen flow display screen 6, an argon flow display screen 7, a current indicator 8, a voltage indicator 9, a start control screen 10, a control output knob 19, a current display screen 20, a voltage fine-tuning knob 21, a nitrogen gas flow control knob 22, a voltage control knob 23, a voltage indicator 24 and an argon gas flow control knob 25.

[0042] The atmosphere system includes a vacuum pump 16, a high-purity argon gas cylinder 1 and a high-purity nitrogen gas cylinder 2. The vacuum pump 16 is provided with a vacuum pump outlet 26. A vacuum pump connecting pipe 15 is provided between the vacuum pump 16 and the heat treatment furnace. The vacuum pump connecting pipe 15 is provided with a vacuum breaking knob 43. The furnace body 29 is connected to different gas cylinders through a ventilation hose 13.

[0043] The glow device includes a source platform 33 and a cathode platform 36 located in the furnace. The source platform 33 is connected to the 50A power supply 11 wire 14; the cathode platform 36 is connected to the 75A power supply 18 wire 14. 12 pure titanium perforated long tubes 30 are evenly distributed and connected to the source platform 33 through nuts. The round tube sleeve 31 for installing the TC4 round tube is placed on the cathode platform 36, located in the middle of the furnace body 29.

[0044] The heat treatment furnace is also provided with a temperature measuring instrument 41, which is usually a special temperature measuring gun. The temperature measuring gun measures the real-time surface temperature of the sample in the furnace by emitting infrared rays 42. The final temperature of the round tube sample is based on the temperature measured by the temperature measuring gun. The inner wall temperature can be adjusted by adjusting the up and down buttons of the temperature control display screen 5, and the temperature of the temperature control display screen 5 is the temperature measured by the temperature measuring thermocouple 28.

[0045] The above equipment adopted in the method has reasonable structural design and is easy to operate, and can effectively control costs while ensuring the treatment effect.

[0046] The double glow plasma nitriding treatment method for the inner wall surface of titanium alloy round tube includes the following steps:

[0047] S1 The as-cast TC4 bar is processed into a TC4 round tube with an outer diameter of 60 mm, an inner diameter of 30 mm and a length of 1100 mm by turning, boring and sawing;

[0048] S2 Equipment installation: unscrew the water pipes, gas pipes, and electric wires 14 that affect the opening of the furnace body 29, replace the large screw with a dedicated small screw, open the furnace body 29, and then evenly hoist the long tube 30 with holes on the source platform 33 in the furnace, and place the round tube sleeve 31 on the cathode platform 36 in the furnace;

[0049] S3 Sample surface cleaning and coating:

[0050] ① Dip cotton in acetone, use a pry bar to repeatedly push the cotton to evenly wipe the inner wall of TC4 round tube sample 32, and use a hair dryer to dry it;

[0051] ② Take another piece of cotton and dip it in alcohol. Use a pry bar to push the cotton repeatedly to evenly wipe the inner wall of TC4 round tube sample 32 to remove the oil stains, and then blow dry.

[0052] ③ Similarly, clean and dry the outer wall of TC4 round tube sample 32, then evenly apply the ion nitriding special anti-seepage coating on the outer wall with a brush, and wait for half an hour for the coating to air dry and close to the metal sample;

[0053] S4 Vacuuming:

[0054] ① Open the furnace body 29, put the processed TC4 round tube sample 32 into the round tube sleeve 31 in the heat treatment furnace, put in the sample fixing ring 37 to fix the round tube, close the furnace body 29, replace the small screw with the large screw, and connect the water pipe, air pipe, wire 14 and other connecting devices;

[0055] ② Turn on the power, start the atmosphere system, run the vacuum pump 16, open the butterfly valve to allow the vacuum pump 16 to evacuate the furnace until the vacuum pressure is less than 1Pa, and turn on the water cooling switch;

[0056] S5 Temperature Rise:

[0057] ① Adjust the voltage to 750V, the temperature of the TC4 round tube sample 32 in the furnace begins to rise, and when it is heated to 50℃, the gas switch of the atmosphere system automatically opens;

[0058] ② Rotate the argon knob to 100, and when the temperature rises to 60°C, the vacuum pump 16 runs stably, the gas pressure rises steadily, and the gas pressure is set to 200Pa. At the same time, adjust the special temperature measuring instrument 41 to measure the real-time surface temperature of the internal TC4 round tube sample 32;

[0059] ③ Wait for about 20 minutes until the pressure can no longer rise and the temperature rises slowly, then turn the argon knob to 200 and the nitrogen knob to 0.6 to make N2:Ar=3:1;

[0060] ④ Then, the duty cycle is gradually increased by rotating the control output knob 19 to change the heating rate, and the temperature is changed by adjusting the temperature meter until the temperature measured by the dedicated temperature meter 41 is 900°C ± 15°C;

[0061] S6 double glow ion nitriding:

[0062] ① Equipment parameters during stable operation: source voltage of glow system is 750V, pressure is 200Pa, N2:Ar=3:1; source control output is 27.6%, current is 30A; cathode control output is 50.7%, current is 24A;

[0063] ② Double glow ion nitriding operation time: When the sample surface rises to 900℃ for the first time, the time starts to count down for 8 hours;

[0064] S7 Cooling:

[0065] ① After running for the required time, the voltage on both sides of the source and cathode return to 0, the gas flow rate returns to 0, and the control output knob 19 is adjusted to the minimum; ② When the gas pressure is pumped to 100Pa, turn off the vacuum pump 16 and keep the cooling water flowing until the sample is cooled to room temperature with the furnace.

[0066] S8 Sampling:

[0067] After the temperature is lowered, the vacuum valve is opened to make the pressure in the furnace consistent with the atmospheric pressure, the cooling water is turned off, the water pipe, gas pipe, electric wire 14 and other connecting devices that affect the opening of the furnace body 29 are disconnected, the furnace body 29 is opened, and the sample is taken out;

[0068] S9 Cleaning:

[0069] Take out the TC4 round tube sample 32, clean it with clean water, and wipe off the special anti-seepage coating on the surface;

[0070] S10 Detection, Analysis, Characterization:

[0071] The inner wall morphology, color, metallographic structure, and mechanical properties of TC4 round tube sample 32 were tested, analyzed, and characterized. A metallographic microscope was used for metallographic structure analysis. A Vickers hardness tester was used for hardness analysis.

[0072] The test results of the TC4 round tube sample prepared by the present invention are as follows:

[0073] Figure 2 The metallographic microstructure of the inner wall of the TC4 round tube sample 32 prepared by the present invention is shown in FIG. Figure 2It can be seen that the metallographic matrix of the inner wall of the TC4 round tube sample 32 prepared by the present invention has no change, and the inner wall has a nitriding layer. The metallographic structure of the nitriding layer is tightly combined with the matrix, the risk of falling off is small, and the layer thickness can reach 17±1µm.

[0074] Figure 3 This is a hardness performance diagram of the inner wall of the TC4 round tube sample 32 prepared in the present invention. As shown in the figure, the average hardness of the inner wall of the TC4 round tube sample 32 prepared in the present invention is as high as 713.04 HV, which is 2.2 times the hardness of the matrix.

[0075] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0076] Meanwhile, the directions such as front, back, left, and right involved in this embodiment are only used as a reference for directions and do not represent directions in actual use. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0077] The above description is only a preferred embodiment of the present invention and is not a limitation on the design of this case. Any equivalent changes made based on the design key of this case shall fall within the protection scope of this case.

Claims

1. A method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding, characterized in that: The equipment used in the treatment method is a double-layer glow ion metal diffusion heat treatment furnace, which includes a furnace bottom plate and a hood-shaped furnace body, and is connected to an opening and closing device, a power supply system, an atmosphere system, a glow device and a cooling system; The processing method includes the following steps: S1 processes the as-cast TC4 bar into TC4 round tube; S2 Equipment installation: Open the furnace body through the opening and closing device set on the heat treatment furnace, and then evenly hoist the long tube with holes on the source platform in the furnace; S3 Sample surface cleaning and coating: Wipe the inner wall of the TC4 round tube sample with acetone and alcohol and blow dry, then clean the outer wall of the TC4 round tube sample and apply anti-seepage coating; S4 Vacuuming: Place the TC4 round tube sample after the above treatment into the heat treatment furnace; turn on the power, start the atmosphere system, and use the vacuum pump to evacuate the furnace until the vacuum pressure is less than 1Pa, and turn on the water cooling switch; S5 Heating: Set the voltage to 750V, and gradually heat up the TC4 round tube sample in the furnace. When it is heated to 50℃, the gas switch of the atmosphere system is automatically turned on to pass argon. When the temperature rises to 60℃, set the gas pressure to 200Pa. Wait until the gas pressure in the furnace cannot rise and the sample temperature rises slowly, and pass argon and nitrogen at the same time, so that N2:Ar=3:1 in the furnace. Then adjust the control output knob to change the heating rate, and adjust the temperature until the sample temperature is 900℃±15℃. S6 Double glow ion nitriding: ① Equipment parameters during stable operation: source voltage of glow system 750V, pressure 200Pa, N2:Ar=3:1; source control output 27.6%, current 30A; cathode control output 50.7%, current 24A; ② Double glow ion nitriding operation time: When the surface of TC4 round tube sample rises to 900℃, start timing for 8 hours; S7 Cooling: ① After running for the required time, the voltage on both sides of the source and cathode return to 0, the gas flow rate returns to 0, and the control output knob is adjusted to the minimum; ② When the gas pressure is pumped to 100Pa, turn off the vacuum pump and keep the cooling water flowing until the sample is cooled to room temperature with the furnace; In step S1, the as-cast TC4 rod is processed into a TC4 round tube with an outer diameter of 60 mm, an inner diameter of 30 mm, and a length of 1100 mm; In step S2, during the equipment installation, a pre-customized round tube sleeve is prepared and placed on the cathode platform in the furnace; In step S4, the processed TC4 round tube sample is placed in a round tube sleeve in a heat treatment furnace, and a sample fixing ring is used to cooperate with the round tube sleeve to fix the TC4 round tube sample.

2. A method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: The TC4 round tube has the following chemical elements by weight (wt%): Al: 6.01, V: 3.84, Fe: 0.30, C: 0.10, N: 0.05, O: 0.20, H: 0.015, Ti: 89, and the rest are impurities.

3. The method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: After cooling is completed, the sampling, cleaning and testing steps are carried out as follows: S8 Sampling: After the temperature is lowered, open the vacuum valve to make the pressure in the furnace consistent with the atmospheric pressure, turn off the cooling water, open the furnace body, and take out the sample; S9 Cleaning: Take out the TC4 round tube sample, clean it with clean water, and wipe off the special anti-seepage coating on the surface; S10 Inspection, analysis, and characterization: Inspection, analysis, and characterization of the inner wall morphology, color, metallographic structure, and mechanical properties of TC4 round tube samples; metallographic structure analysis using a metallographic microscope; The hardness analysis was carried out using a Vickers hardness tester.

4. A method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: The as-cast TC4 rod is processed into round tubes by turning, boring and sawing.

5. The method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: The power supply system includes a 50A power supply and a 75A power supply. The 50A voltage stabilizer and the 75A voltage stabilizer matched with the power supply are respectively connected to the heat treatment furnace through electric wires.

6. A method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: The atmosphere system includes a vacuum pump, a high-purity argon gas cylinder and a high-purity nitrogen gas cylinder. The vacuum pump is provided with a vacuum pump outlet. A vacuum pump connecting pipe is provided between the vacuum pump and the heat treatment furnace. A vacuum breaking knob is provided on the vacuum pump connecting pipe. The furnace body is connected to different gas cylinders through a ventilation hose.

7. A method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: The glow device includes a source platform and a cathode platform located in the furnace, and the source platform is connected to a 50A power supply wire; The cathode platform is connected to a 75A power supply wire.

8. The method for treating the inner wall surface of a titanium alloy round tube by double glow plasma nitriding as claimed in claim 1, characterized in that: The heat treatment furnace is provided with an observation hole connected to the furnace, a cooling water inlet and a cooling water outlet pipe; The heat treatment furnace is also equipped with a thermometer to measure the real-time surface temperature of the samples in the furnace.

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