Carbonitriding process of metal stator for screw drill
By using a salt bath carbonitriding process, a uniform and dense carbonitriding layer is formed using composite carbon materials and a diffusion catalyst. This solves the problem of uneven diffusion layer in metal stators, improves wear resistance and corrosion resistance, and extends the service life of screw drills.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-02
- Publication Date
- 2026-03-10
AI Technical Summary
The uneven diffusion layer and poor bonding of existing metal stators result in limited improvement in wear resistance. In particular, under high load and high wear environments, early wear and spalling are prone to occur, affecting the service life and reliability of screw drills.
The salt bath carbonitriding process combines composite carbon materials (charcoal, carbon nanotubes, and light calcium carbonate) with infiltration catalysts (such as yttrium carbonate and rare earth fluorides). By controlling the temperature and atmosphere in stages, a uniform and dense carbonitriding layer is formed, which improves the wear resistance and corrosion resistance of the metal stator.
It significantly improves the wear resistance and corrosion resistance of the metal stator, extends the service life of the screw drill bit, reduces mass loss, and enhances stability and reliability under high load conditions.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of metal stator, in particular, relates to a carbonitriding process of metal stator for screw drill. BACKGROUND
[0002] As a kind of downhole power tool widely used in petroleum drilling, geological exploration and other fields, the metal stator, one of the core components of screw drill, needs to withstand high torque, high wear and complex and changeable downhole conditions during work process.The metal stator is usually meshed with rotor to form a sealed cavity, which converts the hydraulic energy of drilling fluid into mechanical energy to drive the drill bit to rotate and break rock.
[0003] At present, the common metal stator is usually made of alloy structural steel (such as 38CrMoAl, 42CrMo, etc.) and its wear resistance and corrosion resistance are improved by heat treatment or surface modification technology.However, the traditional carburizing, nitriding or carbonitriding process has problems such as uneven penetration layer, poor bonding force, limited wear resistance improvement, etc., especially in high load and high wear environment, the stator surface is prone to early wear, peeling and even failure, which seriously affects the service life and reliability of screw drill.
[0004] Therefore, it is of great significance to propose a carbonitriding process of metal stator for screw drill, which can obtain a metal stator for screw drill with uniform external penetration layer, thereby improving its wear resistance and prolonging the service life of metal stator for screw drill. SUMMARY
[0005] The present application proposes a carbonitriding process of metal stator for screw drill, which solves the problem of poor wear resistance of metal stator in the related art.
[0006] The technical scheme of the present application is as follows: The present application proposes a carbonitriding process of metal stator for screw drill, which includes the following steps: After preheating the metal stator, salt bath carbonitriding and salt bath oxidation treatment are carried out to obtain the metal stator for screw drill; When the salt bath carbonitriding is carried out, the carbonitriding agent used includes the following components by weight: Composite carbon material 24 parts, ammonium chloride 10~15 parts, urea 4~8 parts, yttrium oxide 3~6 parts, potassium ferrocyanide 4~8 parts, potassium chloride 10~15 parts; The raw materials of the composite carbon material include charcoal, carbon nanotubes and light calcium carbonate.
[0007] As a further technical scheme, the inner wall of the metal stator has a circular arc line type structure meshed with the rotor line type; The material of the metal stator is one of 38CrMoAl and 42CrMo.
[0008] In the application, the inner wall curve of the metal stator is a circular arc type, which can make the sealing cavity contact force of the circular arc type screw motor more stable, the sealing length longer, the working performance better, the reliability and stability better under the same load working condition during the use of the screw drill.
[0009] As a further technical solution, the preparation method of the composite carbon material comprises the following steps: A1, blending the charcoal and carbon nanotubes, and uniformly dispersing them in water to obtain a blended solution; A2, adding the light calcium carbonate to the blended solution, mixing uniformly, concentrating, and drying to obtain the composite carbon material.
[0010] As a further technical solution, the weight ratio of the charcoal and carbon nanotubes to the light calcium carbonate is 4-7:28.
[0011] In the application, when the weight ratio of the charcoal and carbon nanotubes to the light calcium carbonate is 4-7:28, the wear resistance of the metal stator for screw drill can be further improved, and the mass loss can be reduced to 2.71 mg.
[0012] As a further technical solution, the weight ratio of the charcoal and carbon nanotubes is 1.5-4:1, for example, it can be 1.5:1, 2:1, 3:1, 4:1, and preferably 3:1.
[0013] As a further technical solution, in step A1, when uniformly dispersing, an ultrasonic method is used, the ultrasonic frequency is 20-30 kHz, and the ultrasonic time is 20-30 min.
[0014] As a further technical solution, in step A2, when uniformly mixing, an ultrasonic method is used, the ultrasonic frequency is 20-30 kHz, and the ultrasonic time is 1-2 h.
[0015] As a further technical solution, when the salt bath carbonitriding is performed, a permeation accelerator is also added, and the permeation accelerator comprises the following components by weight: Yttrium carbonate 4-6 parts, rare earth fluoride 5-8 parts.
[0016] In the application, the rare earth fluoride is any one or more rare earth fluorides in the art, for example, it can be lanthanum fluoride, yttrium fluoride, and preferably yttrium fluoride.
[0017] As a further technical solution, before preheating, the metal stator is cleaned with anhydrous ethanol.
[0018] As a further technical solution, the preheating is carried out at a temperature increasing rate of 10-15 ℃ / min to 350-400 ℃, and the preheating time is 3-6 min.
[0019] As a further technical solution, the salt bath carbonitriding is divided into a first-stage salt bath carbonitriding and a second-stage salt bath carbonitriding. In the first-stage salt bath carbonitriding, the temperature is 560-580 ℃, the time is 1-2 h, and a mixed gas of nitrogen and triethanolamine is introduced. In the second-stage salt bath carbonitriding, the temperature is 600-630 ℃, the time is 1-2 h, and compressed air is introduced.
[0020] In the present application, when the salt bath carbonitriding is divided into a first-stage salt bath carbonitriding and a second-stage salt bath carbonitriding, in the first-stage salt bath carbonitriding, a mixed gas of nitrogen and triethanolamine is introduced, and the carbonitriding treatment is carried out at 560-580 ℃. After that, at a relatively low temperature, the activation of nitrogen is easier to form nitrides, and the active carbon produced by triethanolamine can provide an appropriate amount of carbon source during the formation of the nitride layer, thereby preventing the brittleness of the nitride layer in the early stage due to the lack of carbon, so that a more uniform and dense carbonitriding transition layer is formed. Then, in the second-stage salt bath carbonitriding, the carbonitriding treatment is carried out at 600-630 ℃ in an air atmosphere. The increase in temperature accelerates the diffusion speed of atoms, so that the transition layer formed in the first-stage salt bath carbonitriding is further densified. At the same time, the oxygen in the compressed air reacts with the carbon and nitrogen on the metal surface to form a continuous and dense protective film on the metal surface, thereby effectively blocking the intrusion of corrosive media, so that the metal stator for a screw drill has good wear resistance and corrosion resistance.
[0021] As a further technical solution, the volume ratio of the nitrogen and triethanolamine is 2:1.
[0022] As a further technical solution, in the first-stage salt bath carbonitriding, the temperature is increased to 560-580 ℃ at a temperature increasing rate of 10-15 ℃ / min; and in the second-stage salt bath carbonitriding, the temperature is increased to 600-630 ℃ from 560-580 ℃ at a temperature increasing rate of 3-5 ℃ / min.
[0023] In the first-stage salt bath carbonitriding and the second-stage salt bath carbonitriding, the gas flow is independently 3-5 L / min.
[0024] As a further technical solution, the salt bath oxidation is divided into a first-time salt bath oxidation and a second-time salt bath oxidation. The first salt bath oxidation is cooled to 350-400 DEG C at a cooling rate of 10-15 DEG C / min, and after holding for 10-20 min, water cooling is performed to 25-30 DEG C. The second salt bath oxidation is heated to 350-400 DEG C at a heating rate of 10-15 DEG C / min, and after holding for 10-20 min, water cooling is performed to 25-30 DEG C.
[0025] As a further technical solution, the first salt bath oxidation and the second salt bath oxidation each independently include the following components in parts by weight: Sodium nitrate 10-20 parts, sodium carbonate 6-10 parts, sodium hydroxide 2-5 parts.
[0026] As a further technical solution, after the first salt bath oxidation is completed, polishing and drying treatment are further included, and the polishing time is 20-25 min.
[0027] As a further technical solution, after the second salt bath oxidation, cleaning, drying and oil immersion treatment are further included, and the oil immersion time is 5-10 min.
[0028] The working principle and beneficial effects of the present application are as follows: 1. In the present application, after preheating treatment of the metal stator, salt bath carbonitriding treatment is performed to infiltrate carbon and nitrogen atoms on the surface of the metal stator, which complement each other to improve the surface layer performance. Then, the carbonitriding workpiece is subjected to oxidation treatment to increase the density of the infiltration layer and eliminate residual cyanide ions to a certain extent, thereby obtaining a metal stator for screw drill with good wear resistance and safety.
[0029] 2. In the present application, during the salt bath carbonitriding treatment, the carbonitriding agent mainly comprises a composite carbon material, combined with ammonium chloride, urea, yttrium oxide, potassium ferrocyanide and potassium chloride, which can effectively improve the carbonitriding effect of the metal stator under the combined action of the components. The composite carbon material includes charcoal, carbon nanotubes and light calcium carbonate. The charcoal is subjected to composite treatment with carbon nanotubes and light calcium carbonate. The light calcium carbonate can reduce the defect of easy agglomeration of charcoal. The carbon nanotubes promote the combustion of charcoal, and the high specific area characteristics of the carbon nanotubes increase the contact area of charcoal with other infiltrating agents and the metal surface, facilitating full combustion, thereby improving the carbonitriding effect and forming a uniform and stable carbonitriding layer, thereby improving the wear resistance of the metal stator for screw drill. DETAILED DESCRIPTION
[0030] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative effort are within the scope of protection of the present application.
[0031] In the following examples and comparative examples, the material of the metal stator is 38CrMoAl.
[0032] Example 1 The carbonitriding agent comprises the following components by weight: composite carbon material 24 parts, ammonium chloride 10 parts, urea 4 parts, yttrium oxide 3 parts, potassium ferrocyanide 4 parts, potassium chloride 10 parts; The preparation method of the composite carbon material comprises the following steps: A1, blend 1.5 parts of charcoal and 0.5 parts of carbon nanotubes, add 50 parts of water, and ultrasonically treat at 20 kHz for 30 min to obtain a blended solution; A2, add 28 parts of light calcium carbonate to the blended solution, ultrasonically treat at 20 kHz for 2 h, concentrate, and dry to obtain a composite carbon material; The catalyst comprises the following components by weight: yttrium fluoride 5 parts; The oxidizing agent comprises the following components by weight: sodium nitrate 10 parts, sodium carbonate 6 parts, sodium hydroxide 2 parts; A carbonitriding process for a metal stator of a screw drill tool comprises the following steps: After the metal stator is cleaned on the surface with anhydrous ethanol, the temperature is raised to 350℃ at a temperature raising rate of 10℃ / min, preheating treatment is performed for 6 min, the temperature is raised from 350℃ to 560℃ at a temperature raising rate of 10℃ / min, carbonitriding treatment is performed for 3 h in the presence of a carbonitriding agent and a catalyst under an air atmosphere with a gas flow of 3 L / min, cooling is performed to 350℃ at a cooling rate of 10℃ / min, heat treatment is performed for 20 min under the action of an oxidizing agent, then water cooling is performed to 25℃, polishing treatment is performed for 20 min, drying is performed, the temperature is raised to 350℃ at a temperature raising rate of 10℃ / min, heat treatment is performed for 20 min under the action of an oxidizing agent, water cooling is performed to 25℃ again, cleaning, drying are performed with anhydrous ethanol, oil immersion treatment is performed for 5 min, and then the screw drill tool is obtained after standing for 10 min to dry the oil drops.
[0033] Example 2 The carbonitriding agent comprises the following components by weight: Composite carbon material 24 parts, ammonium chloride 13 parts, urea 6 parts, yttrium oxide 4.5 parts, potassium ferrocyanide 6 parts, potassium chloride 12 parts; The preparation method of the composite carbon material comprises the following steps: A1, 1.5 parts of charcoal and 0.5 parts of carbon nanotubes are blended, then 50 parts of water are added, and ultrasonic treatment is carried out at 25 kHz for 25 min to obtain a blended solution; A2, 28 parts of light calcium carbonate are added to the blended solution, ultrasonic treatment is carried out at 25 kHz for 1.5 h, and then concentration and drying are carried out to obtain a composite carbon material; The catalyst for permeation includes the following components by weight: Yttrium carbonate 5 parts, yttrium fluoride 6 parts; The oxidizing agent includes the following components by weight: Sodium nitrate 15 parts, sodium carbonate 8 parts, sodium hydroxide 4 parts; A carbonitriding process for a metal stator of a screw drill tool, comprising the following steps: After the metal stator is cleaned with anhydrous ethanol, it is heated to 380℃ at a heating rate of 10℃ / min, preheated for 6 min, then heated from 380℃ to 560℃ at a heating rate of 10℃ / min, carbonitriding treatment is carried out for 3 h in the presence of carbonitriding agent and catalyst, under an air atmosphere with a gas flow of 4 L / min, then cooled to 380℃ at a cooling rate of 10℃ / min, heat treatment is carried out for 15 min under the action of the oxidizing agent, then water-cooled to 30℃, polished for 25 min, dried, then heated to 380℃ at a heating rate of 10℃ / min, heat treatment is carried out for 15 min under the action of the oxidizing agent, then water-cooled to 25℃, cleaned with anhydrous ethanol, dried, then immersed in oil for 10 min, placed for 10 min to dry the oil droplets, to obtain a metal stator of a screw drill tool.
[0034] Example 3 The carbonitriding agent includes the following components by weight: Composite carbon material 24 parts, ammonium chloride 15 parts, urea 8 parts, yttrium oxide 6 parts, potassium ferrocyanide 8 parts, potassium chloride 15 parts; The preparation method of the composite carbon material comprises the following steps: A1, 1.5 parts of charcoal and 0.5 parts of carbon nanotubes are blended, then 50 parts of water are added, and ultrasonic treatment is carried out at 30 kHz for 20 min to obtain a blended solution; A2, 28 parts of light calcium carbonate are added to the blended solution, ultrasonic treatment is carried out at 30 kHz for 1 h, and then concentration and drying are carried out to obtain a composite carbon material; The catalyst for permeation includes the following components by weight: Yttrium carbonate 6 parts, yttrium fluoride 8 parts; The oxidizing agent includes the following components by weight: Sodium nitrate 20 parts, sodium carbonate 10 parts, sodium hydroxide 5 parts; A carbonitriding process for a metal stator used in screw drills includes the following steps: After cleaning the surface of the metal stator with anhydrous ethanol, it is heated to 400℃ at a heating rate of 15℃ / min and preheated for 6 minutes. Then, it is heated from 400℃ to 560℃ at a heating rate of 15℃ / min and co-diffused in air at a gas flow rate of 5L / min for 3 hours. After cooling to 400℃ at a cooling rate of 15℃ / min, it is held at the temperature for 10 minutes under the action of an oxidant. Then, it is water-cooled to 30℃, polished for 20 minutes, dried, and then heated to 400℃ again at a heating rate of 15℃ / min. After holding at the temperature for 10 minutes under the action of an oxidant, it is water-cooled to 30℃ again, cleaned with anhydrous ethanol, dried, and then immersed in oil for 10 minutes. After standing for 10 minutes to allow the oil to drip dry, the metal stator for the screw drill tool is obtained.
[0035] Example 4 The only difference between this embodiment and Embodiment 2 is that in the preparation method of the composite carbon material in this embodiment, 6 parts of charcoal and 2 parts of carbon nanotubes are added.
[0036] Example 5 The only difference between this embodiment and Embodiment 2 is that in the preparation method of the composite carbon material in this embodiment, 3 parts of charcoal and 1 part of carbon nanotubes are added.
[0037] Example 6 The only difference between this embodiment and Embodiment 2 is that in the preparation method of the composite carbon material in this embodiment, 5.25 parts of charcoal and 1.75 parts of carbon nanotubes are added.
[0038] Example 7 The only difference between this embodiment and Embodiment 6 is that the carbonitriding process of the metal stator for the screw drill bit is different in this embodiment, specifically: After cleaning the surface of the metal stator with anhydrous ethanol, it is heated to 380°C at a heating rate of 10°C / min and preheated for 6 min. Then, it is heated from 380°C to 560°C at a heating rate of 10°C / min. In the presence of carbonitriding agent and infiltration catalyst, and in a mixed gas with a gas flow rate of 4 L / min (nitrogen and triethanolamine volume ratio of 2:1), it is co-diffused for 3 h. After cooling to 380°C at a cooling rate of 10°C / min, it is held at the temperature for 15 min under the action of an oxidant. Then, it is water-cooled to 30°C, polished for 25 min, dried, and then heated to 380°C again at a heating rate of 10°C / min. After holding at the temperature for 15 min under the action of an oxidant, it is water-cooled to 25°C again, cleaned with anhydrous ethanol, dried, and then immersed in oil for 10 min. After standing for 10 min, the oil is allowed to drip dry, and the metal stator for screw drill tools is obtained.
[0039] Example 8 The only difference between this embodiment and Embodiment 6 is that the carbonitriding process of the metal stator for the screw drill bit is different in this embodiment, specifically: After cleaning the surface of the metal stator with anhydrous ethanol, it was preheated to 380°C at a heating rate of 10°C / min for 6 minutes. Then, it was heated from 380°C to 560°C at a heating rate of 10°C / min. Co-diffusion treatment was then performed for 1 hour in the presence of a carbonitriding agent and a diffusion catalyst in a mixed gas (nitrogen and triethanolamine volume ratio of 2:1) with a gas flow rate of 4 L / min. Finally, it was heated from 560°C to 600°C at a heating rate of 3°C / min in an air atmosphere with a gas flow rate of 4 L / min. After co-infiltration treatment for 2 hours, the temperature was cooled from 600℃ to 380℃ at a cooling rate of 10℃ / min, and then kept at that temperature for 15 minutes under the action of an oxidant. After that, it was water-cooled to 30℃, polished for 25 minutes, dried, and then heated to 380℃ at a heating rate of 10℃ / min. After that, it was kept at that temperature for 15 minutes under the action of an oxidant, and then water-cooled to 25℃ again. After cleaning and drying with anhydrous ethanol, it was oil-immersed for 10 minutes and then left to stand for 10 minutes to allow the oil to drip dry, thus obtaining the metal stator for screw drill tools.
[0040] Example 9 The only difference between this embodiment and Embodiment 6 is that the carbonitriding process of the metal stator for the screw drill bit is different in this embodiment, specifically: After cleaning the surface of the metal stator with anhydrous ethanol, it was preheated to 380°C at a heating rate of 10°C / min for 6 minutes. Then, it was heated from 380°C to 580°C at a heating rate of 10°C / min. Co-diffusion treatment was then performed for 2 hours in the presence of a carbonitriding agent and a diffusion catalyst in a mixed gas (nitrogen and triethanolamine volume ratio of 2:1) with a gas flow rate of 4 L / min. Finally, it was heated from 580°C to 630°C at a heating rate of 5°C / min in an air atmosphere with a gas flow rate of 4 L / min. After co-infiltration treatment for 1 hour, the temperature was cooled from 630°C to 380°C at a cooling rate of 10°C / min. Then, it was kept at this temperature for 15 minutes under the action of an oxidant. After that, it was water-cooled to 30°C, polished for 25 minutes, and dried. Then, it was heated to 380°C at a heating rate of 10°C / min and kept at this temperature for 15 minutes under the action of an oxidant. After that, it was water-cooled to 25°C again. After cleaning and drying with anhydrous ethanol, it was oil-immersed for 10 minutes and then left to stand for 10 minutes to allow the oil to drip dry, thus obtaining the metal stator for screw drill tools.
[0041] Comparative Example 1 The only difference between this comparative example and Example 2 is that, in this comparative example, carbon nanotubes are replaced with an equal amount of charcoal.
[0042] Comparative Example 2 The only difference between this comparative example and Example 2 is that in this comparative example, charcoal is replaced with an equal amount of carbon nanotubes.
[0043] Comparative Example 3 The only difference between this comparative example and Example 2 is that in this comparative example, 24 parts of composite carbon material are used to replace 22.4 parts of light calcium carbonate, 1.2 parts of charcoal and 0.4 parts of carbon nanotubes.
[0044] Experimental Example 1 The metal stator samples for screw drills prepared in Examples 1-9 and Comparative Examples 1-3 were cleaned with anhydrous ethanol for 10 min, dried, and weighed to obtain the initial weight of the metal stator samples for screw drills. The metal stator samples for screw drills were then assembled onto the stage of a friction and wear testing machine and subjected to friction treatment for 1 h. After the test, the samples were cleaned and weighed, and the mass difference before and after wear was calculated as the mass wear amount. During the friction treatment, the vertical load was 1 kN, and the grinding body was made of WC material. The test results are shown in Table 1.
[0045] Table 1 Performance test results of Examples 1-9 and Comparative Examples 1-3
[0046] Compared with Comparative Examples 1-3, the mass wear of the metal stators for screw drills prepared in Examples 1-9 was reduced, indicating that the composite carbon material in the carbonitriding agent includes charcoal, carbon nanotubes, and light calcium carbonate. The composite treatment of charcoal with carbon nanotubes and light calcium carbonate can improve the carburizing effect and ultimately improve the wear resistance of the metal stators for screw drills.
[0047] Experiment Example 2 The corrosion resistance of the metal stator samples for screw drilling tools prepared in Examples 6-9 was tested according to the neutral salt spray test method in GB / T 10125-2021 "Civilization Test in Artificial Atmosphere - Salt Spray Test". During the test, the sodium chloride mass fraction was 5%, the spray pressure was 70 kPa, and the test temperature was 35℃. The time when corrosion began to appear on the sample was recorded. The test results are shown in Table 2.
[0048] Table 2. Corrosion resistance test results of Examples 6-9
[0049] Compared with Examples 6-7, the corrosion time of the metal stator for screw drill tools prepared in Examples 8-9 after corrosion testing can be increased to more than 220 hours. This indicates that when salt bath carbonitriding is divided into a first-stage salt bath carbonitriding and a second-stage salt bath carbonitriding, the first-stage salt bath carbonitriding involves introducing a mixed gas of nitrogen and triethanolamine at 560-580°C, followed by the second-stage salt bath carbonitriding at 600-630°C in an air atmosphere. This approach ensures good wear resistance of the metal stator for screw drill tools while also improving its corrosion resistance.
[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A carbonitriding process for a metal stator for a screw drill, characterized by, The method comprises the following steps: The metal stator is preheated, then is subjected to salt bath carbonitriding and salt bath oxidation treatment to obtain the metal stator for the screw drill; The carbonitriding agent used in the salt bath carbonitriding comprises the following components in parts by weight: The composite carbon material 24 parts, ammonium chloride 10-15 parts, urea 4-8 parts, yttrium oxide 3-6 parts, potassium ferrocyanide 4-8 parts, potassium chloride 10-15 parts; The raw materials of the composite carbon material include charcoal, carbon nanotubes and light calcium carbonate.
2. The carbonitriding process for a metal stator of a screw drill according to claim 1, wherein The inner wall of the metal stator has a circular arc line type which is engaged with the rotor line type. The material of the metal stator is one of 38CrMoAl and 42CrMo.
3. The carbonitriding process for a metal stator of a screw drill according to claim 1, wherein The preparation method of the composite carbon material comprises the following steps: A1, the charcoal and carbon nanotubes are blended and then uniformly dispersed in water to obtain a blending liquid; A2, the light calcium carbonate is added to the blending liquid, mixed uniformly, concentrated, dried to obtain the composite carbon material.
4. The carbonitriding process for a metal stator of a screw drill according to claim 3, wherein The weight ratio of the charcoal and carbon nanotubes to the light calcium carbonate is 4-7:
28.
5. The carbonitriding process for a metal stator of a screw drill according to claim 1, wherein The carbonitriding agent used in the salt bath carbonitriding further comprises the following components in parts by weight: Yttrium carbonate 4-6 parts, rare earth fluoride 5-8 parts.
6. A carbonitriding process for a metal screw- in drill sub according to claim 1, characterized in that, The preheating temperature is 350-400℃ and the preheating time is 3-6 min.
7. The carbonitriding process for a metal stator of a screw drill according to claim 1, wherein The salt bath carbonitriding is divided into first-stage salt bath carbonitriding and second-stage salt bath carbonitriding. The first-stage salt bath carbonitriding is performed at a temperature of 560-580℃ for 1-2 h, and a mixed gas of nitrogen and triethanolamine is introduced. The second-stage salt bath carbonitriding is performed at a temperature of 600-630℃ for 1-2 h, and compressed air is introduced.
8. A carbonitriding process for a metal stator of a screw drill according to claim 7, characterized in that, The volume ratio of the nitrogen to triethanolamine is 2:
1.
9. The carbonitriding process for a metal screw- drill stator according to claim 1, wherein The salt bath oxidation is divided into first-stage salt bath oxidation and second-stage salt bath oxidation. In the first-stage salt bath oxidation, the temperature is cooled at a cooling rate of 15-20℃ / min to 350-400℃, and then the temperature is kept for 10-20 min, and then water cooling is performed to 25-30℃; In the second-stage salt bath oxidation, the temperature is raised at a heating rate of 15-20℃ / min to 350-400℃, and then the temperature is kept for 10-20 min, and then water cooling is performed to 25-30℃.
10. The carbonitriding process for a metal stator of a screw drill according to claim 9, wherein The oxidizing agent used in the first-stage salt bath oxidation and the second-stage salt bath oxidation independently comprises the following components in parts by weight: Sodium nitrate 10-20 parts, sodium carbonate 6-10 parts, sodium hydroxide 2-5 parts.