Drill pipe and method of making same

Abstract

The application provides a drill pipe and a preparation method thereof. The drill pipe comprises a drill pipe body, a carburized-silicon-nitrogen layer, a corrosion-resistant layer and a female joint and a male joint connected with the drill pipe body, which are sequentially arranged on the surface of the drill pipe body. The corrosion-resistant layer comprises a nano titanium nitride layer and a nano titanium carbide layer. The nano titanium nitride layer is arranged on the surface of the carburized-silicon-nitrogen layer away from the drill pipe body. The nano titanium carbide layer is arranged on the surface of the nano titanium nitride layer away from the carburized-silicon-nitrogen layer. The composite structure layer formed by the carburized-silicon-nitrogen layer, the nano titanium nitride layer and the nano titanium carbide layer has excellent properties such as high hardness, strong combination, low wear and high corrosion resistance. The surface hardness of the drill pipe can be significantly improved, the wear rate of the drill pipe can be reduced, and the wear resistance and corrosion resistance of the drill pipe can be improved.

Description

Technical Field

[0001] This invention relates to the field of drill pipe manufacturing, and more specifically, to a drill pipe and its preparation method. Background Technology

[0002] Drill pipe is a commonly used downhole tool in oil and gas field development, facing increasingly harsh corrosive environments. How to protect drill pipes from corrosion has become a crucial issue in extending their service life. Currently, there are two main methods for improving drill pipe life: one is to use corrosion-resistant alloys, such as titanium alloys. Compared to carbon steel drill pipes, titanium alloy drill pipes have better corrosion resistance and a longer service life. However, due to the low hardness and poor wear resistance of titanium alloys, they still suffer from significant wear and corrosion problems. The other method is to apply a metallic coating to the surface of the carbon steel drill pipe using electroplating or chemical plating to achieve wear and corrosion resistance. However, existing electroplating and chemical plating processes produce coatings with low hardness, weak adhesion, and poor wear resistance, which easily lead to the protective coating peeling off and causing drill pipe wear and corrosion, thus shortening the service life of the carbon steel drill pipe.

[0003] Given the aforementioned problems, there is a need to provide a drill pipe with both good corrosion resistance and wear resistance, as well as a method for its preparation. Summary of the Invention

[0004] The main objective of this invention is to provide a drill pipe and its manufacturing method to solve the problem of poor corrosion resistance and wear resistance in existing drill pipes.

[0005] To achieve the above objectives, the present invention provides a drill pipe comprising a drill pipe body, a carburized-silicon-nitride layer, a corrosion-resistant layer, and a female connector and a male connector connected to the drill pipe body, wherein the corrosion-resistant layer comprises: a nano-titanium nitride layer disposed on the surface of the carburized-silicon-nitride layer away from the drill pipe body; and a nano-titanium carbide layer disposed on the surface of the nano-titanium carbide layer away from the carburized-silicon-nitride layer.

[0006] Furthermore, the thickness of the carburized-silicon-nitride layer is 100–200 μm, and the total thickness of the nano-titanium nitride layer and the nano-titanium carbide layer is 4–10 μm.

[0007] Furthermore, the thickness of the nano-titanium nitride layer is 3–6 μm, and the thickness of the nano-titanium carbide layer is 1–4 μm.

[0008] Furthermore, the particle size of the nano-titanium nitride particles in the nano-titanium nitride layer is 100–400 nm.

[0009] Furthermore, the nano-titanium nitride layer comprises multiple layers, and along the direction from the carburized-silicon-nitrogen layer to the nano-titanium carbide, the particle size of the nano-titanium nitride layer is arranged in order of larger to smaller.

[0010] Furthermore, the nano-titanium carbide in the nano-titanium carbide layer is in the form of bulk particles, with a particle size of 100–200 nm.

[0011] Furthermore, the ratio of the particle size of the nano-titanium nitride particles in the nano-titanium nitride layer to the particle size of the nano-titanium carbide particles in the nano-titanium carbide layer is 1:2 to 4:1.

[0012] The second aspect of this application also provides a method for preparing the above-mentioned drill pipe, characterized in that the method includes: performing carburizing-silicon-nitriding treatment on the inner and outer surfaces of the drill pipe body to form a carburizing-silicon-nitriding layer; performing a first chemical deposition on the surface of the carburizing-silicon-nitriding layer to form a nano-titanium nitride layer; and performing a second chemical deposition on the surface of the nano-titanium carbide layer to form a nano-titanium carbide layer, thereby obtaining the drill pipe.

[0013] Furthermore, the temperature for the carburizing-silicon-nitriding treatment is 400–550℃, and the carburizing-silicon-nitriding time is 2–6 hours.

[0014] Furthermore, the temperature for the first chemical deposition is 450–650°C, and the processing time is 1–5 hours.

[0015] Furthermore, the temperature for the second chemical deposition is 450–650°C, and the processing time is 1–5 hours.

[0016] By applying the technical solution of this invention, the carburized-silicon-nitride layer disposed on the inner and outer surfaces of the drill pipe body can improve the hardness and strength of the drill pipe body, while forming a carbon-silicon-nitride transition layer to alleviate the mismatch in thermal expansion coefficients between the nano-titanium nitride layer and the drill pipe body, and reduce interfacial stress, thereby enhancing the film-substrate bonding strength. Because the titanium nitride in the nano-titanium nitride layer is in the nano-sized particle form, it can form a strong interfacial bond with the carburized-silicon-nitride layer on the surface of the drill pipe body compared to ordinary titanium nitride layers, thus improving its bonding force with the carburized-silicon-nitride layer and the wear resistance of the nano-titanium nitride layer. Compared to ordinary titanium carbide layers, the nano-titanium carbide layer has better bonding ability with the nano-titanium nitride layer, and the nano-titanium carbide particles have higher hardness, which can further enhance the overall hardness, wear resistance, and corrosion resistance of the coating. Based on this, the composite structure layer formed by the above-mentioned carburized-silicon-nitrogen layer, nano-titanium nitride layer and nano-titanium carbide layer has excellent properties such as high hardness, strong bonding, low wear and high corrosion resistance, which can significantly improve the surface hardness of the drill pipe and reduce the wear rate of the drill pipe, thereby improving the wear resistance and corrosion resistance of the drill pipe. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of a corrosion-resistant drill pipe structure provided for a preferred embodiment of the present invention.

[0019] Figure 2 A schematic diagram of the carburized-silicon-nitrogen layer and corrosion-resistant coating structure on the surface of a corrosion-resistant drill pipe body, provided as a preferred embodiment of the present invention.

[0020] Figure 3 This is a morphology test image of the titanium carbide layer in the corrosion-resistant layer of the drill pipe prepared in Example 1 of this application.

[0021] Figure 4 This is a test diagram of the friction performance of the corrosion-resistant layer in the drill pipe prepared in Example 1 of this application.

[0022] Figure 5 This is a test diagram of the wear performance of the corrosion-resistant layer in the drill pipe prepared in Example 1 of this application.

[0023] The above figures include the following reference numerals:

[0024] 10. Drill pipe body; 20. Carburized-silicon-nitrided layer;

[0025] 30. Corrosion-resistant layer; 31. Nano-titanium nitride layer; 32. Nano-titanium carbide layer;

[0026] 40. Female connector; 50. Male connector. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0028] As described in the background section, existing drill pipes suffer from poor corrosion and wear resistance. To address these issues, this application provides a drill pipe comprising a drill pipe body 10, a carburized-silicon-nitride layer 20, a corrosion-resistant layer 30, and a female connector 40 and a male connector 50 connected to the drill pipe body 10, wherein the corrosion-resistant layer 30 comprises a nano-titanium nitride layer 31 and a nano-titanium carbide layer 32, the nano-titanium nitride being disposed on the surface of the carburized-silicon-nitride layer 20 away from the drill pipe body 10, and the nano-titanium carbide layer 32 being disposed on the surface of the nano-titanium carbide layer 32 away from the carburized-silicon-nitride layer 20.

[0029] The carburized-silicon-nitrogen layer 20, applied to the inner and outer surfaces of the drill pipe body 10, improves the hardness and strength of the drill pipe body 10. Simultaneously, it forms a carbon-silicon-nitrogen transition layer to alleviate the thermal expansion coefficient mismatch between the nano-titanium nitride layer and the drill pipe body, and reduces interfacial stress, thereby enhancing the film-substrate bonding strength. Because the titanium nitride in the nano-titanium nitride layer 31 consists of nano-sized particles, it can form a strong interfacial bond with the carburized-silicon-nitrogen layer 20 on the surface of the drill pipe body 10 compared to ordinary titanium nitride layers, thus improving its bonding strength with the carburized-silicon-nitrogen layer 20 and the wear resistance of the nano-titanium nitride layer 31. Compared to ordinary titanium carbide layers, the nano-titanium carbide layer 32 has a better bonding ability with the nano-titanium nitride layer 31, and the nano-titanium carbide particles have higher hardness, which further enhances the coating's hardness, wear resistance, and corrosion resistance. Based on this, the composite structure layer formed by the above-mentioned carburized-silicon-nitrogen layer 20, nano-titanium nitride layer 31 and nano-titanium carbide layer 32 has excellent properties such as high hardness, strong bonding, low wear and high corrosion resistance, which can significantly improve the surface hardness of the drill pipe and reduce the wear rate of the drill pipe, thereby improving the wear resistance and corrosion resistance of the drill pipe.

[0030] It should be noted that the carburized-silicon-nitrogen layer 20 and the corrosion-resistant layer 30 may be provided only on the inner surface of the drill pipe body 10, or only on its outer surface, or both the carburized-silicon-nitrogen layer 20 and the corrosion-resistant layer 30 may be provided on both the inner and outer surfaces.

[0031] The main function of the carburized-silicon-nitride layer 20 is to enhance the surface hardness of the drill pipe body 10 and to match the coefficients of thermal expansion with the nano-titanium nitride layer 31 and the nano-titanium carbide layer 32, thereby reducing interfacial stress and enhancing the bonding strength between the drill pipe body 10 and the nano-titanium nitride layer 31 and the nano-titanium carbide layer 32. Preferably, the thickness of the carburized-silicon-nitride layer 20 is 100–200 μm.

[0032] While maintaining the aforementioned thickness of the carburized-silicon-nitride layer 20, preferably, the total thickness of the nano-titanium nitride layer 31 and the nano-titanium carbide layer 32 is 4–10 μm. The composite structure layer formed by the aforementioned carburized-silicon-nitride layer 20, nano-titanium nitride layer 31, and nano-titanium carbide layer 32 can significantly improve the wear resistance and corrosion resistance of the drill pipe. More preferably, the thickness of the nano-titanium nitride layer 31 is 3–6 μm, and the thickness of the nano-titanium carbide layer 32 is 1–4 μm. The structures of the nano-titanium nitride layer 31 and the nano-titanium carbide layer 32 include, but are not limited to, the aforementioned ranges, and limiting them to these ranges is beneficial for further improving the wear resistance and corrosion resistance of the drill pipe.

[0033] The titanium nitride particles in the nano-titanium nitride layer 31 are nano-sized, which gives them high bonding strength with both the carburized-silicon-nitrogen layer 20 and the titanium carbide layer. Preferably, the particle size of the nano-titanium nitride particles in the nano-titanium nitride layer 31 is 100–400 nm.

[0034] In a preferred embodiment, the particle size of the titanium carbide nanoparticles in the titanium carbide nanolayer 32 is 100–200 nm. Limiting the particle size of the titanium carbide nanoparticles in the titanium carbide nanolayer 32 to this range can further improve the compactness of the titanium carbide nanolayer 32 and its bonding strength with the titanium nitride nanolayer 31, thereby further improving its wear resistance and corrosion resistance. More preferably, the ratio of the particle size of the titanium nitride nanoparticles in the titanium nitride nanolayer 31 to the particle size of the titanium carbide nanoparticles in the titanium carbide nanolayer 32 is 1:2 to 4:1.

[0035] Preferably, the coefficient of friction of the drill pipe surface is 0.1 to 0.3; the volumetric wear rate is ≤3.5×10⁻⁶. -6 mm 3 / N·m.

[0036] Preferably, the female connector 40, the male connector 50, and the drill pipe body 10 are all made of carbon steel. The female connector 40, the male connector 50, and the drill pipe body 10 are all connected by threads to obtain a complete corrosion-resistant drill pipe.

[0037] The second aspect of this application also provides a method for preparing the above-mentioned drill pipe, the method comprising: performing carburizing-silicon-nitriding treatment on the inner and outer surfaces of the drill pipe body 10 to form a carburizing-silicon-nitriding layer 20; performing a first chemical deposition on the surface of the carburizing-silicon-nitriding layer 20 to form a nano-titanium nitride layer 31; and performing a second chemical deposition on the surface of the nano-titanium carbide layer 32 to form a nano-titanium carbide layer 32, thereby obtaining the drill pipe.

[0038] Forming a carburized-silicon-nitrided layer 20 on the inner and outer surfaces of the drill pipe body 10 using a plasma carburizing-silicon-nitriding process can improve the hardness and strength of the drill pipe body 10. A nano-titanium nitride layer 31 and a nano-titanium carbide layer 32 are then sequentially formed on the surface of the carburized-silicon-nitrided layer 20 through a first chemical deposition process and a second chemical deposition process. This ultimately yields a drill pipe with a composite structure consisting of the carburized-silicon-nitrided layer 20, the nano-titanium nitride layer 31, and the nano-titanium carbide layer 32. Compared to existing drill pipes, the drill pipe produced by the above method exhibits higher surface hardness, lower wear rate, and better corrosion resistance. Furthermore, the above method is simple, efficient, and suitable for industrial application.

[0039] In a preferred embodiment, the carburizing-silicon-nitriding treatment temperature is 400–550°C, and the carburizing-silicon-nitriding time is 2–6 hours. The carburizing-silicon-nitriding treatment temperature and time include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial for further increasing the carburizing-silicon-nitriding depth, thereby further improving the hardness and strength of the drill pipe.

[0040] In a preferred embodiment, the temperature of the first chemical deposition is 450–650°C, and the processing time is 1–5 hours; the temperature of the second chemical deposition is 450–650°C, and the processing time is 1–5 hours. The temperature and processing time of the first and second chemical depositions include, but are not limited to, the above ranges. Limiting them to the above ranges is beneficial to further improve the bonding between the nano-titanium nitride layer 31 and the nano-titanium carbide layer 32, thereby further improving the overall performance of the drill pipe, such as wear resistance and corrosion resistance.

[0041] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0042] Example 1

[0043] A corrosion-resistant drill pipe includes a drill pipe body 10 made of carbon steel. The inner and outer surfaces of the drill pipe body 10 have a carburized-silicon-nitrogen layer 20 and a corrosion-resistant coating. The left end of the drill pipe body 10 is connected to a female connector 40 by a thread, and the right end is connected to a male connector 50 by a thread. The female connector 40 is an internal thread connector, and the male connector 50 is an external thread connector. Both the female connector 40 and the male connector 50 are made of carbon steel.

[0044] A carburized-silicon-nitrogen layer 20, a nano-titanium nitride layer, and a nano-titanium carbide layer 32 are sequentially disposed on both the inner and outer surfaces of the drill pipe body 10. The carburized-silicon-nitrogen layer 20 has a carburized-silicon-nitrogen temperature of 480℃, a carburized-silicon-nitrogen time of 5h, and a thickness of 180μm. On the surface of the carburized-silicon-nitride layer 20, a nano-titanium nitride layer 31 is first prepared using a low-temperature chemical vapor deposition (LCVD) method. The deposition temperature is 630℃, and the deposition time is 4.5 h, resulting in a titanium nitride grain size of 300 nm and a titanium nitride layer thickness of 6 μm. Then, a nano-titanium carbide layer 32 is prepared on the surface of the nano-titanium nitride layer 31 using a low-temperature chemical vapor deposition (LCVD) method. The deposition temperature is 620℃, and the deposition time is 3 h, resulting in a titanium carbide grain size of 130 nm and a titanium carbide layer thickness of 4 μm. A double-layer structure of nano-titanium nitride layer 31 and nano-titanium carbide layer 32 is obtained, and the corrosion-resistant layer 30 is composed of this double-layer structure. Finally, the female connector 40 and the male connector 50 are respectively connected to the drill pipe body 10 by threads, thus obtaining a complete corrosion-resistant drill pipe.

[0045] Results Measurement

[0046] Figure 3 This is a morphology test image of the titanium carbide layer in the corrosion-resistant layer of the drill pipe prepared in Example 1. According to... Figure 3 It can be seen that the nano-titanium carbide layer 32 in the corrosion-resistant coating on the surface of the corrosion-resistant drill pipe body 10 obtained in Example 1 has a nano-size, with a grain size of 80-150nm. The grains are tightly bonded and the coating has high density.

[0047] Figure 4 This is a test diagram showing the frictional properties of the corrosion-resistant layer in the drill pipe prepared in Example 1. Figure 4 It can be seen that the average friction coefficient of the corrosion-resistant coating on the surface of the corrosion-resistant drill pipe body 10 obtained in Example 1 is 0.13.

[0048] Figure 5 This is a test diagram showing the wear performance of the corrosion-resistant layer in the drill pipe prepared in Example 1. Figure 5 It can be seen that the volumetric wear rate of the corrosion-resistant coating on the surface of the corrosion-resistant drill pipe body 10 obtained in Example 1 is 2.6 × 10⁻⁶. -6 mm 3 / N·m.

[0049] According to calculations, the corrosion-resistant layer on the surface of the drill pipe body 10 obtained in Example 1 consists of titanium and carbon elements, with a carbon element weight percentage of 53.06% and a titanium element weight percentage of 46.94% (as shown in Table 1).

[0050] Table 1

[0051] element % by weight C 53.06 Ti 46.94 total 100.00

[0052] Example 2

[0053] The difference from Example 1 is that when forming the carburized-silicon-nitrogen layer 20, the temperature of the carburized-silicon-nitrogen process is 400°C, the carburized-silicon-nitrogen time is 6 hours, and the thickness is 200 μm.

[0054] A corrosion-resistant layer 30 was prepared on the surface of a carburized-silicon-nitride layer 20 using plasma-enhanced chemical vapor deposition (PECVD). The corrosion-resistant layer had a thickness of 8 μm, with a nano-titanium nitride layer 31 having a thickness of 6 μm and a nano-titanium carbide layer 32 having a thickness of 2 μm. The nano-titanium nitride layer was deposited at 520℃ for 3 h, resulting in a titanium nitride grain size of 100 nm and a titanium nitride layer thickness of 2 μm. The nano-titanium carbide layer was deposited at 500℃ for 2 h, resulting in a titanium carbide grain size of 100 nm and a titanium carbide layer thickness of 1.5 μm.

[0055] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.26; the volumetric wear rate is 3.4 × 10⁻⁶. -7 cm 3 / N·m.

[0056] Example 3

[0057] The difference from Example 1 is that when forming the carburized-silicon-nitrogen layer 20, the temperature of the carburized-silicon-nitrogen process is 500°C, the carburized-silicon-nitrogen time is 2 hours, and the thickness is 100 μm.

[0058] A corrosion-resistant layer 30 was prepared on the surface of a carburized-silicon-nitride layer 20 using plasma-enhanced chemical vapor deposition (PECVD). The corrosion-resistant layer had a thickness of 5 μm, with a nano-titanium nitride layer 31 having a thickness of 3 μm and a nano-titanium carbide layer 32 having a thickness of 2 μm. The nano-titanium nitride layer was deposited at 550℃ for 3 h, resulting in a titanium nitride grain size of 200 nm and a titanium nitride layer thickness of 3 μm. The nano-titanium carbide layer was deposited at 520℃ for 3 h, resulting in a titanium carbide grain size of 170 nm and a titanium carbide layer thickness of 2.0 μm.

[0059] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.23; the volumetric wear rate is 3.2 × 10⁻⁶. -7 cm 3 / N·m.

[0060] Example 4

[0061] The difference from Example 1 is that when forming the carburized-silicon-nitrogen layer 20, the temperature of the carburized-silicon-nitrogen process is 550°C, the carburized-silicon-nitrogen time is 3 hours, and the thickness is 150 μm.

[0062] A corrosion-resistant layer 30 was prepared on the surface of a carburized-silicon-nitride layer 20 using plasma-enhanced chemical vapor deposition (PECVD). The corrosion-resistant layer had a thickness of 9 μm, with a nano-titanium nitride layer 31 having a thickness of 5 μm and a nano-titanium carbide layer 32 having a thickness of 4 μm. The nano-titanium nitride layer was deposited at 450 °C for 3 h, resulting in a titanium nitride grain size of 400 nm and a titanium nitride layer thickness of 4 μm. The nano-titanium carbide layer was deposited at 450 °C for 3 h, resulting in a titanium carbide grain size of 120 nm and a titanium carbide layer thickness of 2.5 μm.

[0063] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.26; the volumetric wear rate is 3.4 × 10⁻⁶. -7 cm 3 / N·m.

[0064] Example 5

[0065] The difference from Example 1 is that when forming the carburized-silicon-nitrogen layer 20, the temperature of the carburized-silicon-nitrogen process is 550°C, the carburized-silicon-nitrogen time is 4 hours, and the thickness is 200 μm.

[0066] A corrosion-resistant layer 30 was prepared on the surface of a carburized-silicon-nitride layer 20 using plasma-enhanced chemical vapor deposition (PECVD). The corrosion-resistant layer had a thickness of 10 μm, comprising a 6 μm thick nano-titanium nitride layer 31 and a 4 μm thick nano-titanium carbide layer 32. The nano-titanium nitride layer was deposited at 620 °C for 5 h, yielding a titanium nitride grain size of 350 nm and a layer thickness of 5.5 μm. The nano-titanium carbide layer was deposited at 610 °C for 5 h, yielding a titanium carbide grain size of 200 nm and a layer thickness of 3.5 μm.

[0067] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.24; the volumetric wear rate is 3.2 × 10⁻⁶. -7 cm 3 / N·m.

[0068] Example 6

[0069] The difference from Example 5 is that when forming the carburized-silicon-nitrogen layer 20, the temperature of the carburized-silicon-nitrogen process is 350°C, the carburized-silicon-nitrogen time is 2 hours, and the thickness is 110 μm.

[0070] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.26; the volumetric wear rate is 3.4 × 10⁻⁶. -6 cm 3 / N·m.

[0071] Example 7

[0072] The difference from Example 5 is that the low-temperature chemical deposition method in Example 1 is used to form nano-titanium nitride layer 31 and nano-titanium carbide layer 32, respectively.

[0073] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.16; the volumetric wear rate is 2.8 × 10⁻⁶. -7 cm 3 / N·m.

[0074] Example 8

[0075] The difference from Example 5 is as follows:

[0076] The thickness of the carburized-silicon-nitrogen layer 20 is 140 μm, the thickness of the nano-titanium nitride layer 31 is 3 μm, and the thickness of the nano-titanium carbide layer 32 is 4 μm.

[0077] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.23; the volumetric wear rate is 3.1 × 10⁻⁶. -7 cm 3 / N·m.

[0078] Example 9

[0079] The difference from Example 5 is as follows:

[0080] The thickness of the carburized-silicon-nitrogen layer 20 is 160 μm, the thickness of the nano-titanium nitride layer 31 is 6 μm, and the thickness of the nano-titanium carbide layer 32 is 1 μm.

[0081] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.24; the volumetric wear rate is 3.3 × 10⁻⁶. -7 cm 3 / N·m.

[0082] Example 10

[0083] The difference from Example 5 is as follows:

[0084] The thickness of the carburized-silicon-nitrogen layer 20 is 130 μm, the thickness of the nano-titanium nitride layer 31 is 2 μm, and the thickness of the nano-titanium carbide layer 32 is 6 μm.

[0085] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.26; the volumetric wear rate is 3.5 × 10⁻⁶. -6 cm 3 / N·m.

[0086] Example 11

[0087] The difference from Example 5 is that the particle size of the nano-titanium nitride layer 31 is 100 nm, and the particle size ratio of the nano-titanium carbide layer 32 is 2:1.

[0088] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.3; the volumetric wear rate is 3.5 × 10⁻⁶. -7 cm 3 / N·m.

[0089] Example 12

[0090] The difference from Example 5 is that the particle size of the nano-titanium nitride layer 31 is 300 nm, and the particle size ratio of the nano-titanium carbide layer 32 is 1:6.

[0091] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.32; the volumetric wear rate is 3.7 × 10⁻⁶. -7 cm 3 / N·m.

[0092] Comparative Example 1

[0093] The difference from Example 5 is that a titanium nitride layer with a particle size of 1 μm is used instead of the nano titanium nitride layer 31.

[0094] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.35; the volumetric wear rate is 7.5 × 10⁻⁶.-7 cm 3 / N·m.

[0095] Comparative Example 2

[0096] The difference from Example 5 is that a titanium carbide layer with a particle size of 1 μm is used instead of the nano titanium carbide layer 32.

[0097] The coefficient of friction of the corrosion-resistant layer on the surface of the drill pipe body 10 is 0.36; the volumetric wear rate is 7.1 × 10⁻⁶. -7 cm 3 / N·m.

[0098] As can be seen from the above description, the above embodiments of the present invention achieve the following technical effects: the composite structure layer formed by the above carburized-silicon-nitrogen layer, nano-titanium nitride layer and nano-titanium carbide layer has excellent properties such as high hardness, strong bonding, low wear and high corrosion resistance, which can significantly improve the surface hardness of the drill pipe and reduce the wear rate of the drill pipe, thereby improving the wear resistance and corrosion resistance of the drill pipe.

[0099] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A drill pipe, characterized in that, The drill pipe includes a drill pipe body (10), a carburized-silicon-nitrided layer (20), a corrosion-resistant layer (30), and a female connector (40) and a male connector (50) connected to the drill pipe body (10), wherein the corrosion-resistant layer (30) includes: Nano-titanium nitride layer (31), wherein the nano-titanium nitride is disposed on the surface of the carburized-silicon-nitrogen layer (20) away from the drill pipe body (10); Nano-titanium carbide layer (32), the nano-titanium carbide layer (32) is disposed on the surface of the nano-titanium carbide layer (32) away from the carburized-silicon-nitrogen layer (20); The ratio of the particle size of the nano-titanium nitride particles in the nano-titanium nitride layer (31) to the particle size of the nano-titanium carbide particles in the nano-titanium carbide layer (32) is 1:2 to 4:

1.

2. The drill pipe according to claim 1, characterized in that, The thickness of the carburized-silicon-nitrogen layer (20) is 100-200 mm, and the total thickness of the nano-titanium nitride layer (31) and the nano-titanium carbide layer (32) is 4-10 mm.

3. The drill pipe according to claim 2, characterized in that, The thickness of the nano-titanium nitride layer (31) is 3-6 mm, and the thickness of the nano-titanium carbide layer (32) is 1-4 mm.

4. The drill pipe according to any one of claims 1 to 3, characterized in that, The nano-titanium nitride particles in the nano-titanium nitride layer (31) have a particle size of 100-400 nm.

5. The drill pipe according to claim 4, characterized in that, The nano-titanium carbide layer (32) contains bulk titanium carbide particles with a particle size of 100-200 nm.

6. A method for preparing a drill pipe according to any one of claims 1 to 5, characterized in that, The method for preparing the drill pipe includes: The inner and outer surfaces of the drill pipe body (10) are subjected to carburizing-silicon-nitriding treatment to form a carburizing-silicon-nitriding layer (20). A first chemical deposition is performed on the surface of the carburized-silicon-nitride layer (20) to form a nano-titanium nitride layer (31); and A second chemical deposition is performed on the surface of the nano-titanium carbide layer (32) to form the nano-titanium carbide layer (32), thus obtaining the drill rod.

7. The method for preparing drill pipe according to claim 6, characterized in that, The carburizing-silicon-nitriding treatment is carried out at a temperature of 400–550°C for 2–6 hours.

8. The method for preparing drill pipe according to claim 6, characterized in that, The temperature of the first chemical deposition is 450–650°C, and the processing time is 1–5 hours.

9. The method for preparing drill pipe according to claim 6, characterized in that, The temperature for the second chemical deposition is 450–650°C, and the processing time is 1–5 hours.

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