Wear-resistant and corrosion-resistant drill rod inner coating paint and preparation method thereof

Abstract

The invention discloses a wear-resistant and corrosion-resistant drill rod inner coating paint and a preparation method thereof, and belongs to the technical field of drill rod inner coating paints.The drill rod inner coating paint comprises a bottom layer paint and a surface layer paint which are of a gradient structure; the prime paint of the gradient structure is prepared through a laser cladding technology, is a metal ceramic composite coating material and is sprayed on the surface of the inner wall of the drill rod; the metal ceramic composite coating material is composed of metal and ceramic powder, and the proportion of the ceramic powder in the prime paint is gradually increased from the inner wall of the drill rod to the bottom layer. The coating can effectively isolate a corrosive medium from being in contact with a drill rod base body, slow down the corrosion rate of the inner wall, resist erosion of drilling mud, improve the bonding strength of an inner coating of the drill rod and the inner wall of the drill rod and relieve the influence of local stress and high temperature of the drill rod on the inner coating of the drill rod.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of drill pipe inner coating paint, in particular to a wear-resistant and corrosion-resistant drill pipe inner coating paint and a preparation method thereof. BACKGROUND

[0002] As a major fuel resource of national economy, oil exploitation technology has been greatly developed. Drilling tools such as drill pipes are used in the process of oil drilling. In addition, drilling fluid, mud and other materials mostly contain corrosive media, which will cause corrosion of the drill string to varying degrees during use. Therefore, the oil drilling tool inner coating technology emerges as the times require, effectively alleviates the corrosion of the drilling tool, delays the service period and saves the exploitation cost.

[0003] Well operations are performed with the rotation of the drill bit. Drilling mud is pumped to the bottom of the well through the drill string, cools and lubricates the drill bit, and cleans the wellbore by transferring cuttings to the surface.

[0004] Drill pipe failures usually occur in four places: threaded connections, drill pipe inner surfaces, drill pipe body outer surfaces, and upset locations. Among them, the corrosion point of the drill pipe inner surface is a small hole formed due to the removal of the inner coating of the drill pipe, forming a stress concentration point. Since the drilling mud can be corrosive and erosive, the mud will damage and remove the inner coating of the drill pipe, making it a suitable location for crack generation. Although the inner wall of the drill pipe is mainly subjected to fluid dynamic action, it may also be subjected to certain mechanical stresses in some cases, such as friction, collision, etc. during tripping. The drill pipe is an important component of the drill string, and during operation, complex loads such as tension, compression, torsion, bending, hydrostatic pressure and vibration act on the drill pipe. The number, location and induction time of these loads are not constant, but constantly changing. In addition, in deviated wells, the loads and stresses will be more different and complex, and fatigue cracks will be generated at the stress concentration points. With the continuation of the load, these cracks expand radially and circumferentially, perpendicular to the drill pipe axis. At the same time, high-pressure drilling mud penetrates the crack wall, accelerating the development of crack propagation by increasing the corrosion and erosion process. If the crack can pass through the wall thickness and reach the other surface (internal or external), it can form an opening called erosion. During drilling, this phenomenon can be identified by the pressure drop at the surface. If the surface pressure drop is not obvious, and the driller continues to push the drill bit, the crack will expand to the critical section through erosion, where it cannot withstand the load, and the drill pipe will be twisted off.

[0005] When circulation is poor or absent, the heat generated by friction between the drill string and the wellbore wall cannot be promptly dissipated, leading to localized temperature increases. Frictional heating failure occurs when steel is heated to 704-815°C. This is because the steel's microstructure and mechanical properties change within this temperature range, resulting in a decrease in hardness and strength, and reduced wear resistance and friction resistance. The formation of these localized high-temperature zones accelerates fatigue failure of the drill string material, making it more susceptible to fatigue cracks, especially under repeated stress. High temperatures reduce the toughness of the drill string material and increase its brittleness, making it more susceptible to brittle fracture. Summary of the Invention

[0006] As described in the above-mentioned prior art, one of the purposes of the present invention is to provide a wear-resistant and corrosion-resistant drill pipe inner coating, which can effectively isolate the contact between the corrosive medium and the drill pipe substrate, slow down the corrosion rate of the inner wall, and resist the erosion of drilling mud, thereby improving the bonding strength between the drill pipe inner coating and the inner wall of the drill pipe, and alleviating the influence of local stress and high temperature of the drill pipe on the drill pipe inner coating.

[0007] The second object of the present invention is to provide a method for manufacturing the wear-resistant and corrosion-resistant drill pipe inner coating paint. The method has simple steps and can industrially produce the wear-resistant and corrosion-resistant drill pipe inner coating paint.

[0008] One of the purposes of the present invention is achieved by the following technical solution: A wear-resistant and corrosion-resistant drill pipe inner coating, comprising a base coating and a surface coating with a gradient structure; The gradient structured primer is prepared by laser cladding technology. The gradient structured primer is a metal-ceramic composite coating material, which is sprayed onto the surface of the inner wall of the drill pipe. The metal-ceramic composite coating material is composed of metal and ceramic powder, and the proportion of the ceramic powder in the primer gradually increases from the inner wall of the drill pipe to the bottom layer. The metals include basic components, alloying elements, and rare earth elements; The basic component is iron; The alloying elements are nickel (Ni), cobalt (Co), chromium (Cr), molybdenum (Mo), and tungsten (W); The rare earth elements are yttrium (Y) and lanthanum (La); The powder particle size of the primer is in the range of 10-50 microns; The surface coating is a nano-composite coating material, which is sprayed on the surface of the drill pipe substrate; the nano-composite coating material is composed of nano-alumina, nano-silicon dioxide and ceramic powder; the particle size of the ceramic powder in the surface coating ranges from 0.1 to 10 microns.

[0009] Furthermore, the ceramic powder includes one of titanium carbide, tungsten carbide and silicon nitride.

[0010] The second object of the present invention is achieved by adopting the following technical solution: A method for manufacturing a wear-resistant and corrosion-resistant drill pipe inner coating comprises the following steps: S1. Material preparation S11, metal powder: preparing the metal powder whose basic component is iron, as well as alloy element powder, ceramic powder and rare earth element powder; S12, preparing mixed powder: uniformly mixing the metal powder, the ceramic powder and the rare earth element powder according to a designed ratio, with a powder particle size ranging from 10 to 50 μm, to obtain composite powders containing different amounts of ceramic powder; S2. Pretreatment of the inner surface of the drill pipe S21. Cleaning: Clean the inner wall of the drill pipe to remove oil, rust and impurities on the surface to ensure the surface is clean; S22, roughening treatment: sandblasting the inner wall of the drill pipe to increase the surface roughness and improve the bonding strength between the bottom layer and the inner wall of the drill pipe; S3, Laser Cladding Process A high-power fiber laser is selected, and the high-power fiber laser is equipped with a double-barrel powder feeder, wherein the laser cladding parameters are: laser power 2000W-3000W, scanning speed 10mm / s-20mm / s, and powder feeding rate 1g / min-3g / min; the composite powder containing ceramic powder is uniformly sprayed onto the inner wall surface of the drill pipe through the double-barrel powder feeder, and the laser is simultaneously started to melt and solidify the composite powder containing ceramic powder under the action of the laser beam, first cladding the composite powder with a low ceramic powder content, and then gradually increasing the ceramic powder content layer by layer, with the ceramic powder content increasing at a rate of 10%-20% in each layer, to form a gradient structure bottom layer by layer cladding; S4. Post-processing S41, cooling: after the cladding is completed, the bottom layer of the gradient structure is allowed to cool naturally to room temperature; S42, surface treatment: lightly polishing the surface of the bottom layer of the gradient structure to remove uneven portions of the surface, thereby ensuring that the surface of the bottom layer of the gradient structure is smooth; S5. Preparation of surface layer S51, nanocomposite coating material: preparing the nanocomposite coating material composed of nanoalumina, nanosilicon dioxide and ceramic powder; S52, spraying process: select plasma spraying equipment, set the power of the spray gun is 30-60 kilowatt, the current is 400-600 ampere, the voltage is 70-120 volts; control the distance between the spray gun and the inner wall surface of the drill pipe is between 100-200 millimeters, the spraying speed is kept at 3-6 meters / minute; keep the included angle between the spray gun and the inner wall surface of the drill pipe is between 60-90 degrees; the nano composite coating material is uniformly sprayed on the surface of the bottom layer to form a surface layer; the coating thickness should be ensured uniform during spraying, generally controlled at 10-50 microns; S53, curing treatment: Drying: after spraying, the sprayed surface layer is naturally dried at room temperature, or accelerated drying is carried out by using appropriate heating equipment; Curing: after drying, the sprayed surface layer is placed in an oven, the curing temperature is between 100℃-300℃, the curing time is 1-5 hours, and a wear-resistant and corrosion-resistant drill pipe inner coating is formed on the inner wall surface of the drill pipe.

[0011] Compared with the prior art, the beneficial effects of the present application are: (1) The wear-resistant and corrosion-resistant drill pipe inner coating provided by the present application prevents the inner wall from being corroded and thinned: drilling fluid usually has a certain corrosive property, may contain acidic gas, salt and other corrosive media, which can cause corrosion to the inner wall of the drill pipe, resulting in the thickness of the inner wall being thinned. The surface coating is a nano composite coating material, which is sprayed on the surface of the drill pipe base body; the nano composite coating material is composed of nano alumina, nano silicon dioxide and ceramic powder, and the dense coating formed by the cooperation of high-hardness nano materials such as nano alumina and nano silicon dioxide and ceramic powder can effectively isolate the contact between corrosive media and the drill pipe base body, slow down the corrosion rate of the inner wall, thereby indirectly maintaining the stability and precision of the inner diameter, and improving the hardness of the coating; the high-hardness inner coating can effectively resist scratches, reduce the generation of defects on the inner wall surface of the drill pipe, reduce the risk of stress concentration and crack propagation caused by surface defects, and improve the overall strength and reliability of the drill pipe. The ceramic powder has good high-temperature stability and can maintain its performance unchanged under high-temperature environment encountered during drilling.

[0012] The drill pipe needs to withstand complex mechanical loads during the drilling process, including tension, compression, torsion and bending. The bonding strength between the coating and the substrate is directly related to the service life and reliability of the coating. The base coating is a metal-ceramic composite coating material, which is sprayed on the surface of the inner wall of the drill pipe; the metal-ceramic composite coating material is composed of a metal component and a ceramic component. The metal-ceramic composite coating material can significantly enhance the bonding strength between the base and the inner wall of the drill pipe through the metallurgical bonding of the metal component and the inner wall of the drill pipe, ensure the stability of the coating in a high-stress environment, and utilize the toughness of the metal and the wear resistance of the ceramic to form a coating with excellent performance. A gradient structure base layer is prepared, and the proportion of the ceramic powder in the base coating gradually increases from the inner wall of the drill pipe to the base layer, reducing the difference in thermal expansion coefficient and elastic modulus between the coating and the inner wall of the drill pipe, thereby reducing the residual stress between the base and the inner wall of the drill pipe caused by the sudden change in the coating composition, and improving the bonding strength and fatigue resistance between the base and the inner wall of the drill pipe. The metal components include basic components, alloying elements, and rare earth elements. Among them, rare earth elements: yttrium (Y) and lanthanum (La) in the primer can form chemical bonds with the metal atoms on the surface of the inner wall of the drill pipe, further enhancing the bonding strength between the primer and the inner wall of the drill pipe and improving the adhesion of the coating. In addition, rare earth elements can refine the grains in the primer, making the microstructure of the primer more uniform and dense, and improving the strength and toughness of the primer. Among them, the basic components and alloying elements have good metallurgical compatibility with the inner wall of the drill pipe (steel matrix), and can enhance the bonding strength between the primer and the inner wall of the drill pipe. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with specific embodiments. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0014] Reduce the thermal conductivity of the coating: Due to its hollow structure inside, the heat conduction path is blocked, thereby reducing the thermal conductivity of the coating, improving the thermal insulation performance of the coating, and reducing the generation of smoke caused by increased temperature.

[0015] The hardness and toughness of the coating require a balance. Coatings with high hardness (such as ceramic coatings) generally have good wear resistance, but may have poor toughness and be prone to cracking when subjected to impact or vibration. Coatings with high toughness (such as rubber coatings) have advantages in impact resistance, but may lack wear resistance. Therefore, it is necessary to select a coating that matches the hardness and toughness according to the specific conditions of the drilling environment. For example, in drilling environments with both wear and certain impact, metal-ceramic coatings can be selected. They combine the toughness of metal with the hardness of ceramic, better adapting to these complex working conditions.

[0016] Mechanical stress Tensile stress: Drill pipe needs to withstand tensile force from the drilling rig during drilling, especially during tripping operations, drill pipe will be subjected to greater tensile stress. This stress will be transmitted to the coating, requiring the coating to have sufficient tensile strength.

[0017] Compression stress: During drilling, drill pipe may be subjected to compression from the ground reaction force, especially when drilling through hard formations, local areas of the drill pipe will be subjected to compression stress. The coating needs to be able to withstand this compression stress without deformation or peeling.

[0018] Torsional stress: Drill pipe will be subjected to torsional moment during rotary drilling, resulting in torsional stress. The coating needs to have good shear strength to prevent damage under torsional stress.

[0019] Bending stress: Drill pipe may bend in the wellbore due to factors such as hole deviation, irregular wellbore, etc., resulting in bending stress. The coating needs to be able to adapt to this bending deformation without cracking or peeling.

[0020] 2. Thermal stress Temperature change: Drill pipe will experience large temperature changes during drilling, especially in deep and high temperature wells. The thermal expansion coefficients of the coating material and the substrate material are different, which will cause thermal stress. When the temperature rises, the expansion of the coating and the substrate is different, which will generate tensile or compressive stress inside the coating; when the temperature decreases, the opposite stress will occur. This thermal stress will reduce the bonding strength of the coating and the substrate, and even cause the coating to crack or peel off.

[0021] Local high temperature: Drill pipe may encounter local high temperature areas during drilling, such as high temperature near the drill bit, local high temperature of the formation, etc. These local high temperatures will cause the properties of the coating material to degrade, and at the same time, thermal stress will be generated, affecting the stability of the coating.

[0022] Example 1

[0023] This embodiment provides a wear-resistant and corrosion-resistant drill pipe inner coating paint, including a gradient structure bottom coating and a surface coating. The gradient structure bottom coating is prepared by laser cladding technology, and the gradient structure bottom coating is a cermet composite coating material, which is sprayed on the surface of the inner wall of the drill pipe; the cermet composite coating material is composed of metal and ceramic powder titanium carbide, and the proportion of ceramic powder titanium carbide in the bottom coating gradually increases from the inner wall of the drill pipe to the bottom. The metal includes basic components, alloying elements and rare earth elements. The basic component is iron. The alloying elements are nickel (Ni), cobalt (Co), chromium (Cr), molybdenum (Mo) and tungsten (W). The rare earth elements are yttrium (Y) and lanthanum (La). The powder particle size of the base coating ranges from 10 microns; The surface coating is a nano-composite coating material, which is sprayed on the surface of the drill pipe base; the nano-composite coating material is composed of nano-alumina, nano-silicon dioxide and ceramic powder titanium carbide; the particle size of the ceramic powder titanium carbide in the surface coating ranges from 5 microns.

[0024] The preparation method of the wear-resistant and corrosion-resistant drill pipe inner coating coating provided by the embodiment comprises the following steps: S1, material preparation S11, metal powder: prepare the metal powder of the base component iron, alloy element powder, ceramic powder titanium carbide and rare earth element powder; S12, mixed powder preparation: uniformly mix the metal powder, ceramic powder titanium carbide and rare earth element powder according to the designed proportion, and the powder particle size ranges from 10 microns to 50 microns, to obtain a composite powder containing ceramic powder titanium carbide with different contents; S2, drill pipe inner wall surface pretreatment S21, cleaning: clean the inner wall of the drill pipe to remove oil stains, rust marks and impurities on the surface and ensure the surface is clean; S22, roughening treatment: perform sand blasting treatment on the inner wall of the drill pipe to increase the surface roughness and improve the bonding strength of the base layer and the inner wall of the drill pipe; S3, laser cladding process Select a high-power fiber laser, and the high-power fiber laser is equipped with a double-cylinder powder feeder; the laser cladding parameters are as follows: laser power 2000W, scanning speed 15mm / s, and powder feeding rate 2g / min; the composite powder containing ceramic powder titanium carbide is uniformly sprayed to the inner wall surface of the drill pipe through the double-cylinder powder feeder, and the laser is started at the same time, so that the composite powder containing ceramic powder titanium carbide is melted and solidified under the action of the laser beam; first, the composite powder with a lower content of ceramic powder titanium carbide is cladded, and then the content of ceramic powder titanium carbide is increased layer by layer, and the content of ceramic powder titanium carbide of each layer is increased by 20%; through the layer-by-layer cladding, a gradient structure base layer is formed; S4, post-treatment S41, cooling: after the cladding is completed, the gradient structure base layer is naturally cooled to room temperature; S42, surface treatment: slightly polish the surface of the gradient structure base layer to remove the uneven parts on the surface and ensure the smoothness of the surface of the gradient structure base layer; S5, preparation of the surface layer S51, nano-composite coating material: prepare the nano-composite coating material composed of nano-alumina, nano-silicon dioxide and ceramic powder titanium carbide; S52. Spraying process: Select plasma spray equipment and set the spray gun power to 40 kilowatts, current to 500 amperes, and voltage to 100 volts; control the distance between the spray gun and the inner wall surface of the drill pipe to be between 100 mm and the spray speed to be maintained at 5 meters per minute; maintain the angle between the spray gun and the inner wall surface of the drill pipe to be between 80 degrees; spray the nanocomposite coating material evenly on the surface of the base layer to form a surface layer; ensure that the coating thickness is uniform during spraying, generally controlled at 10-50 microns; S53, curing treatment: Drying: After spraying, let the sprayed surface dry naturally at room temperature, or use appropriate heating equipment to accelerate drying; Curing: After drying, place the sprayed surface layer in an oven with a curing temperature of 300°C and a curing time of 5 hours to form a wear-resistant and corrosion-resistant drill pipe inner coating on the inner wall surface of the drill pipe.

[0025] In this embodiment, the sprayed surface is sealed with a silicate inorganic sealing agent to reduce pores and cracks on the surface of the wear-resistant and corrosion-resistant drill pipe inner coating and prevent the intrusion of corrosive media.

[0026] In this embodiment, ceramic materials with good compatibility with metal components are selected, such as titanium carbide, silicon nitride (Si3N4), tungsten carbide (WC), etc. These ceramic materials have good stability and compatibility with metals at high temperatures.

[0027] Example 2

[0028] This embodiment provides a wear-resistant and corrosion-resistant drill pipe inner coating paint, which includes a base coating and a surface coating with a gradient structure; The gradient structure of the primer is prepared by laser cladding technology. The gradient structure of the primer is a metal-ceramic composite coating material, which is sprayed on the surface of the inner wall of the drill pipe. The metal-ceramic composite coating material is composed of metal and ceramic powder tungsten carbide. The proportion of ceramic powder tungsten carbide in the primer gradually increases from the inner wall of the drill pipe to the bottom layer. Metals include basic components, alloying elements, and rare earth elements; The basic ingredient is iron; The alloying elements are nickel (Ni), cobalt (Co), chromium (Cr), molybdenum (Mo), and tungsten (W); Rare earth elements are yttrium (Y) and lanthanum (La); The powder particle size of the primer is in the range of 30 microns; The surface coating is a nano-composite coating material, which is sprayed on the surface of the drill pipe substrate; the nano-composite coating material is composed of nano-alumina, nano-silicon dioxide and ceramic powder tungsten carbide; the particle size of the ceramic powder tungsten carbide in the surface coating is in the range of 0.1 micron.

[0029] The present embodiment provides a method for preparing a wear-resistant and corrosion-resistant drill pipe inner coating, comprising the following steps: S1. Material preparation S11. Metal powder: prepare metal powder whose basic component is iron, as well as alloy element powder, ceramic powder, tungsten carbide and rare earth element powder; S12, mixed powder preparation: metal powder, ceramic powder tungsten carbide and rare earth element powder are mixed uniformly according to the designed ratio, the powder particle size range is 10-50 microns, and composite powders containing ceramic powder tungsten carbide with different contents are obtained; S2. Pretreatment of the inner surface of the drill pipe S21. Cleaning: Clean the inner wall of the drill pipe to remove oil, rust and impurities on the surface to ensure the surface is clean; S22, roughening treatment: sandblasting the inner wall of the drill pipe to increase the surface roughness and improve the bonding strength between the bottom layer and the inner wall of the drill pipe; S3, Laser Cladding Process A high-power fiber laser was selected, equipped with a double-barrel powder feeder. The laser cladding parameters were as follows: laser power 2450W, scanning speed 10mm / s, and powder feeding rate 1g / min. A composite powder containing ceramic powder and tungsten carbide was evenly sprayed onto the inner wall surface of the drill pipe through the double-barrel powder feeder. The laser was simultaneously started to melt and solidify the composite powder containing ceramic powder and tungsten carbide under the action of the laser beam. The composite powder with a low ceramic powder and tungsten carbide content was first clad, and then the ceramic powder and tungsten carbide content was gradually increased. The increase rate of the ceramic powder and tungsten carbide content in each layer was 10%. Through layer-by-layer cladding, a gradient structure bottom layer was formed. S4. Post-processing S41, cooling: after the cladding is completed, the bottom layer of the gradient structure is allowed to cool naturally to room temperature; S42. Surface treatment: lightly polish the surface of the bottom layer of the gradient structure to remove uneven parts of the surface and ensure that the surface of the bottom layer of the gradient structure is smooth; S5. Preparation of surface layer S51. Nanocomposite coating material: preparing a nanocomposite coating material composed of nanoalumina, nanosilicon dioxide and ceramic powder tungsten carbide; S52, spraying process: select plasma spraying equipment, set the power of the spray gun to 30 kilowatts, the current to 600 amperes, the voltage to 70 volts; control the distance between the spray gun and the inner wall surface of the drill pipe to be between 150 millimeters, and the spraying speed to be kept at 6 meters / minute; keep the included angle between the spray gun and the inner wall surface of the drill pipe to be between 60 degrees; uniformly spray the nano composite coating material on the surface of the bottom layer to form a surface layer; ensure uniform coating thickness during spraying, generally controlled at 10-50 microns; S53, curing treatment: Drying: after spraying is completed, the sprayed surface layer is naturally dried at room temperature, or accelerated drying is performed using appropriate heating equipment; Curing: after drying, the sprayed surface layer is placed in an oven, the curing temperature is between 200°C, and the curing time is 1 hour, forming a wear-resistant and corrosion-resistant drill pipe inner coating on the inner wall surface of the drill pipe.

[0030] Example 3

[0031] The wear-resistant and corrosion-resistant drill pipe inner coating provided in this embodiment is a wear-resistant and corrosion-resistant drill pipe inner coating, which comprises a gradient structure bottom layer coating and a surface layer coating. The gradient structure bottom layer coating is prepared by laser cladding technology, and the gradient structure bottom layer coating is a metal ceramic composite coating material sprayed on the surface of the inner wall of the drill pipe; the metal ceramic composite coating material is composed of metal and ceramic powder silicon nitride, and the proportion of ceramic powder silicon nitride in the bottom layer coating gradually increases from the inner wall of the drill pipe to the bottom layer; The metal includes a basic component, alloying elements, and rare earth elements; The basic component is iron; The alloying elements are nickel (Ni), cobalt (Co), chromium (Cr), molybdenum (Mo), and tungsten (W); The rare earth elements are yttrium (Y) and lanthanum (La); The powder particle size of the bottom layer coating ranges from 50 microns; The surface layer coating is a nano composite coating material, which is sprayed on the surface of the drill pipe substrate; the nano composite coating material is composed of nano alumina, nano silicon dioxide, and ceramic powder silicon nitride; the particle size of the ceramic powder silicon nitride in the surface layer coating ranges from 10 microns.

[0032] The preparation method of the wear-resistant and corrosion-resistant drill pipe inner coating provided in this embodiment comprises the following steps: S1, material preparation S11, metal powder: prepare metal powder with a basic component of iron, alloying element powder, ceramic powder silicon nitride, and rare earth element powder; S12, mixed powder preparation: metal powder, ceramic powder silicon nitride and rare earth element powder are mixed uniformly according to the designed ratio, the powder particle size range is 10-50 microns, and composite powders containing ceramic powder silicon nitride at different contents are obtained; S2. Pretreatment of the inner surface of the drill pipe S21. Cleaning: Clean the inner wall of the drill pipe to remove oil, rust and impurities on the surface to ensure the surface is clean; S22, roughening treatment: sandblasting the inner wall of the drill pipe to increase the surface roughness and improve the bonding strength between the bottom layer and the inner wall of the drill pipe; S3, Laser Cladding Process A high-power fiber laser was selected, equipped with a double-barrel powder feeder. The laser cladding parameters were: laser power 3000W, scanning speed 20mm / s, and powder feeding rate 3g / min. Composite powder containing ceramic powder silicon nitride was evenly sprayed onto the inner wall surface of the drill pipe through the double-barrel powder feeder. The laser was simultaneously activated to melt and solidify the composite powder containing ceramic powder silicon nitride under the action of the laser beam. The composite powder with a low ceramic powder silicon nitride content was first clad, and then the ceramic powder silicon nitride content was gradually increased layer by layer. The ceramic powder silicon nitride content increased by 15% in each layer. Through layer-by-layer cladding, a gradient structure bottom layer was formed. S4. Post-processing S41, cooling: after the cladding is completed, the bottom layer of the gradient structure is allowed to cool naturally to room temperature; S42. Surface treatment: lightly polish the surface of the bottom layer of the gradient structure to remove uneven parts of the surface and ensure that the surface of the bottom layer of the gradient structure is smooth; S5. Preparation of surface layer S51, nanocomposite coating material: preparing a nanocomposite coating material composed of nanoalumina, nanosilicon dioxide and ceramic powder silicon nitride; S52. Spraying process: Select plasma spray equipment and set the spray gun power to 60 kilowatts, current to 400 amperes, and voltage to 120 volts; control the distance between the spray gun and the inner wall surface of the drill pipe to be between 200 mm and the spray speed to be maintained at 3 meters per minute; maintain the angle between the spray gun and the inner wall surface of the drill pipe to be between 90 degrees; spray the nanocomposite coating material evenly on the surface of the base layer to form a surface layer; ensure that the coating thickness is uniform during spraying, generally controlled to be between 10 and 50 microns; S53, curing treatment: Drying: After spraying, let the sprayed surface dry naturally at room temperature, or use appropriate heating equipment to accelerate drying; Curing: After drying, place the sprayed surface layer in an oven with a curing temperature of 100°C and a curing time of 3 hours to form a wear-resistant and corrosion-resistant drill pipe inner coating on the inner wall surface of the drill pipe.

[0033] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A wear-resistant and corrosion-resistant drill pipe inner coating, characterized in that: Including base coating and surface coating with gradient structure; The gradient structured primer is prepared by laser cladding technology. The gradient structured primer is a metal-ceramic composite coating material, which is sprayed onto the surface of the inner wall of the drill pipe. The metal-ceramic composite coating material is composed of metal and ceramic powder, and the proportion of the ceramic powder in the primer gradually increases from the inner wall of the drill pipe to the bottom layer. The metals include basic components, alloying elements, and rare earth elements; The basic component is iron; The alloying elements are nickel (Ni), cobalt (Co), chromium (Cr), molybdenum (Mo), and tungsten (W); The rare earth elements are yttrium (Y) and lanthanum (La); The powder particle size of the primer is in the range of 10-50 microns; The surface coating is a nano-composite coating material, which is sprayed on the surface of the drill pipe substrate; the nano-composite coating material is composed of nano-alumina, nano-silicon dioxide and ceramic powder; the particle size of the ceramic powder in the surface coating ranges from 0.1 to 10 microns.

2. The wear-resistant and corrosion-resistant drill pipe inner coating according to claim 1, characterized in that: The ceramic powder includes one of titanium carbide, tungsten carbide and silicon nitride.

3. The method for preparing a wear-resistant and corrosion-resistant drill pipe inner coating according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1. Material preparation S11, metal powder: preparing the metal powder whose basic component is iron, as well as alloy element powder, ceramic powder and rare earth element powder; S12, preparing mixed powder: uniformly mixing the metal powder, the ceramic powder and the rare earth element powder according to a designed ratio, with a powder particle size ranging from 10 to 50 μm, to obtain composite powders containing different amounts of ceramic powder; S2. Pretreatment of the inner surface of the drill pipe S21. Cleaning: Clean the inner wall of the drill pipe to remove oil, rust and impurities on the surface to ensure the surface is clean; S22, roughening treatment: sandblasting the inner wall of the drill pipe to increase the surface roughness and improve the bonding strength between the bottom layer and the inner wall of the drill pipe; S3, Laser Cladding Process A high-power fiber laser is selected, and the high-power fiber laser is equipped with a double-barrel powder feeder, wherein the laser cladding parameters are: laser power 2000W-3000W, scanning speed 10mm / s-20mm / s, and powder feeding rate 1g / min-3g / min; the composite powder containing ceramic powder is uniformly sprayed onto the inner wall surface of the drill pipe through the double-barrel powder feeder, and the laser is simultaneously started to melt and solidify the composite powder containing ceramic powder under the action of the laser beam, first cladding the composite powder with a low ceramic powder content, and then gradually increasing the ceramic powder content layer by layer, with the ceramic powder content increasing at a rate of 10%-20% in each layer, to form a gradient structure bottom layer by layer cladding; S4. Post-processing S41, cooling: after the cladding is completed, the bottom layer of the gradient structure is allowed to cool naturally to room temperature; S42, surface treatment: lightly polishing the surface of the bottom layer of the gradient structure to remove uneven portions of the surface, thereby ensuring that the surface of the bottom layer of the gradient structure is smooth; S5. Preparation of surface layer S51, nanocomposite coating material: preparing the nanocomposite coating material composed of nanoalumina, nanosilicon dioxide and ceramic powder; S52. Spraying process: Select plasma spraying equipment, set the spray gun power to 30-60 kilowatts, the current to 400-600 amperes, and the voltage to 70-120 volts; control the distance between the spray gun and the inner wall surface of the drill pipe to be between 100-200 mm, and maintain the spray speed at 3-6 meters per minute; maintain the angle between the spray gun and the inner wall surface of the drill pipe to be between 60-90 degrees; uniformly spray the nanocomposite coating material onto the surface of the base layer to form a surface layer; ensure that the coating thickness is uniform during spraying, generally controlled to be 10-50 microns; S53, curing treatment: Drying: After spraying, let the sprayed surface dry naturally at room temperature, or use appropriate heating equipment to accelerate drying; Curing: After drying, the sprayed surface layer is placed in an oven at a curing temperature between 100° C. and 300° C. for 1 to 5 hours to form a wear-resistant and corrosion-resistant drill pipe inner coating on the inner wall surface of the drill pipe.

4. The method for preparing a wear-resistant and corrosion-resistant drill pipe inner coating according to claim 3, characterized in that: The sprayed surface is sealed with a silicate inorganic sealing agent to reduce pores and cracks on the surface of the wear-resistant and corrosion-resistant drill pipe inner coating and prevent the intrusion of corrosive media.