A method for preparing a functionally graded, high-hardness, and wear-resistant drive gear

Abstract

The present invention provides a method for preparing a functionally gradient, high-hardness, and wear-resistant driving gear, comprising the following steps: using a first alloy powder as a laser cladding raw material, laser cladding the outer cylindrical surface of a bar stock to obtain a driving gear intermediate V01; performing surface heat treatment on the driving gear intermediate V01 to increase the surface hardness; using a second alloy powder as a laser cladding raw material, laser cladding the outer cylindrical surface of the driving gear intermediate V01 to obtain a driving gear intermediate V02; and performing characteristic structural processing on the driving gear intermediate V02 to obtain the functionally gradient, high-hardness, and wear-resistant driving gear. The present invention uses laser cladding to clad two layers of gradient material, and the effective hardened layer depth of the driving gear is ≥6mm, which effectively improves the wear resistance of the driving gear and further extends the effective service life of the driving gear. At the same time, by controlling the thickness of the original bar stock and the cladding layer, stress concentration on the cladding joint surface is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of drive gear manufacturing, in particular to a method for preparing a functionally gradient high-hardness wear-resistant drive gear. Background Art

[0002] To date, increasing oil and gas recovery by drilling horizontal wells and increasing the length of the horizontal well section through the reservoir has become an important method for increasing oil and gas production in oil fields. Using downhole tractors to pull horizontal well coiled tubing and transport logging tools offers advantages such as low cost and reduced time consumption. Common tractors include wheeled and telescopic types. Wheeled tractors are characterized by their small size, strong adaptability to well diameters, and a wide range of applications. The traction force of wheeled tractors is determined by the contact friction between the drive gear and the pipe wall. The sharp teeth press into the pipe wall to create a plowing effect, increasing friction and thereby traction.

[0003] At present, the commonly used material for drive gears is low-carbon carburized steel. In order to improve the hardness and wear resistance of the gear teeth, carburizing is a common treatment method. However, network carbides may be produced during the carburizing process, resulting in increased brittleness of the gear teeth and decreased impact toughness. At the same time, the effective hardened layer depth after carburizing is only 1-1.5mm. After the effective hardened layer depth is worn, the gear tooth hardness decreases significantly, and the wear amount will increase rapidly in geometric multiples, causing damage to the drive gear. At this time, the tractor needs to be removed from the drilling platform to replace the drive gear, which greatly reduces the drilling efficiency.

[0004] One of the current solutions to address the issues of insufficient effective hardened layer depth and wear resistance in drive gears is laser direct energy deposition (LDED). LDED uses a laser as a heat source to rapidly melt the laser cladding material and the substrate surface, forming a metallurgical bond between the cladding material and the substrate. Through layer-by-layer deposition, structural components can be manufactured and repaired. This LDED technology boasts high forming precision, a high degree of automation, and a minimal heat-affected zone. By adjusting process parameters such as powder feed rate, laser power, and laser spot size, the size and precision of structural components can be controlled.

[0005] Patent publication number CN116100267A discloses a method for fabricating lightweight, wear-resistant titanium alloy logging gears. The method uses laser cladding to deposit a controllable thickness of alloy steel coating onto a titanium alloy gear blank, and then directly processes the coating into the tooth surface. However, the single-layer alloy steel cladding provides limited improvement in hardness and wear resistance. Furthermore, the induction hardening process after hobbing can easily cause material deformation, compromising the dimensional accuracy of the logging gear.

[0006] Patent document with publication number CN113981441A discloses a method for preparing a gear surface strengthening coating and a gear, which improves the strength and wear resistance of the gear surface by forming a cladding strengthening layer on the gear surface. However, the cladding strengthening layer is only formed on the surface of the gear, and its tooth material is still the original gear material. The overall strength and service life of the gear are limited, and the interface between the cladding layer and the substrate is on the gear tooth, which easily causes stress concentration at the interface between the cladding layer and the substrate. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the present invention provides a method for preparing a functionally gradient high-hardness wear-resistant driving gear, which effectively improves the hardness and wear resistance of the gear teeth, avoids stress concentration on the cladding bonding surface, and effectively improves the overall performance of the driving gear.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a functionally gradient high-hardness wear-resistant drive gear, comprising the following steps:

[0009] S1: Using the first alloy powder as the laser cladding raw material, laser cladding is performed on the outer cylindrical surface of the bar to obtain a driving gear intermediate V01 with a first alloy cladding layer;

[0010] S2: performing surface heat treatment on the driving gear intermediate V01 obtained in step S1 to increase its surface hardness;

[0011] S3: Using the second alloy powder as a laser cladding raw material, laser cladding is performed on the outer cylindrical surface of the driving gear intermediate body V01 processed in step S2 to obtain a driving gear intermediate body V02 having a first alloy cladding layer and a second alloy cladding layer;

[0012] S4: performing characteristic structural processing on the driving gear intermediate V02 to obtain the functionally gradient high hardness wear-resistant driving gear;

[0013] The thickness of the first alloy cladding layer is the same as the tooth height, and starts from 0.5-2 mm below the tooth root circle and ends at 0.5-2 mm below the tooth top circle.

[0014] Furthermore, the first alloy powder is composed of the following components in percentage by weight: 0.4-0.5% C, 0.17-0.37% Si, 0.3-1.2% Mn, 0.6-1.0% Cr, 0.10-0.35% Mo, 2.25-4.25% Ni, and the balance Fe.

[0015] Furthermore, the second alloy powder is composed of the following components in percentage by weight: 16-20% Cr, 0-1.5% Ni, 0-0.8% Mn, 0.1-0.3% C, 0.5-1.2% W, and the balance Fe.

[0016] Furthermore, the thickness of the second alloy cladding layer starts from the outer circumference of the first alloy cladding layer (ie, starts from 0.5-2 mm below the tooth top circle) and ends at 0.5-2 mm above the tooth top circle.

[0017] Furthermore, after the surface heat treatment in step S2, the surface hardness of the first cladding layer is 53-58HRC; and after the treatment in step S4, the tooth top hardness of the functionally gradient high hardness wear-resistant driving gear obtained is ≥62HRC.

[0018] Furthermore, the effective hardened layer depth of the functionally gradient high-hardness wear-resistant driving gear, that is, the surface depth with a hardness of 50HRC or above, is ≥6mm.

[0019] Furthermore, the cladding parameters of the laser cladding in step S1 are: laser power 1200-1500 W, spot diameter 2-4 mm; powder feeding rate 0.1-1 r / min; scanning speed 500-1000 mm / min.

[0020] Furthermore, the cladding parameters of the laser cladding in step S3 are: laser power 500-800 W, spot diameter 3-4 mm; powder feeding rate 0.5-1.1 r / min; scanning speed 300-400 mm / min.

[0021] Furthermore, the surface heat treatment in step S2 is medium frequency induction hardening treatment.

[0022] Furthermore, the bar material is polished and ultrasonically cleaned before step S1.

[0023] Positive effects of the present invention: The present invention adopts laser cladding to clad two layers of gradient materials, wherein the inner layer is an alloy steel layer and the outer layer is a W-containing high-hardness alloy layer, which effectively improves the wear resistance of the driving gear, while retaining the original core material of the driving gear wheel, so that its toughness and wear resistance are well matched. In addition, after being treated by the present invention, the effective hardened layer depth of the driving gear is ≥6mm, thereby further improving the wear resistance of the driving gear teeth and extending the effective service life of the driving gear. At the same time, by controlling the thickness of the original bar stock and the cladding layer, the position of the bonding surface between the cladding layer and the bar stock substrate is adjusted, avoiding stress concentration on the cladding bonding surface. In short, the present invention can achieve a good match between the toughness of the driving gear core and the hardness and wear resistance of the gear teeth, so that the driving gear can achieve optimal performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the functionally gradient high hardness wear-resistant drive gear;

[0025] Figure 2 yes Figure 1 Schematic diagram of the AA cross-section structure;

[0026] Figure 3a This is a picture of the actual object before processing;

[0027] Figure 3b This is the actual picture after processing;

[0028] Figure 4 This is a Vickers hardness variation curve from the surface to the inside of the functionally gradient high hardness wear-resistant drive gear.

[0029] In the figure: 1. core bar, 2. first alloy cladding layer, 3. second alloy cladding layer. DETAILED DESCRIPTION

[0030] The preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0031] A preferred embodiment of the present invention provides a method for manufacturing a functionally graded, high-hardness, wear-resistant drive gear. The drive gear is a petroleum logging drive gear. The drive gear manufactured in this embodiment has a maximum outer diameter of φ85 mm, a root diameter of φ75 mm, and a thickness of 16 mm. 20CrMo steel is used as the core bar stock. The manufacturing method comprises the following steps:

[0032] (1) Material preparation: Take a quenched and tempered 20CrMo rod with a thickness of 25 mm and an outer diameter of φ73 mm; polish the outer cylindrical surface of the rod with 80#, 200#, and 400# sandpaper in sequence to remove the oxide scale of the rod, and then use ultrasonic cleaning in anhydrous ethanol for 25 minutes to obtain the original core rod V0;

[0033] (2) Alloy cladding: The first alloy powder is used as the raw material for laser cladding, and the outer cylindrical surface of the bar is laser clad to obtain a driving gear intermediate V01 with a first alloy cladding layer;

[0034] Among them, the outer diameter of the rod after the alloy cladding is φ83.5-84 mm; the first alloy powder is composed of the following components in percentage by weight: 0.45% C, 0.28% Si, 0.77% Mn, 0.8% Cr, 0.25% Mo, 3.74% Ni, and Fe as a balance (the Ni-Cr-Mo elements ensure that the alloy has good hardenability, high fatigue strength, and stable metallographic structure, ensuring that the alloy has good strength and toughness matching; the carbon content of the alloy is above 0.4, ensuring that the hardness after induction quenching can reach above 55 HRC); the cladding parameters of the laser cladding are: laser power 1300 W, spot diameter 3.2 mm; powder feed rate 0.3 r / min; scanning speed 800 mm / min.

[0035] (3) Heat Treatment: The obtained drive gear intermediate V01 with an outer diameter of φ83.5-84 mm was subjected to medium frequency induction heat treatment (frequency 10,000 Hz, power 100 kW, drive gear movement speed 120 mm / min) to increase its surface hardness. After this heat treatment, the cylindrical surface hardness of the drive gear intermediate V01 was HRC 55 or above. During the heat treatment, the center temperature of the original core bar V0 did not exceed the tempering temperature during the bar quenching and tempering treatment, effectively preventing the core bar from softening and ensuring its strength, toughness, and stability.

[0036] (4) High-hardness alloy cladding: The second alloy powder is used as laser cladding powder to laser clad the outer surface of the driving gear intermediate V01 processed in step S2, and a driving gear intermediate V02 with a first alloy cladding layer and a second alloy cladding layer is obtained (the actual object is shown in FIG. Figure 3a wherein the thickness of the second alloy cladding layer starts from the outer circular surface of the first alloy cladding layer and ends at 1 mm above the tooth top circle.

[0037] Among them, the outer diameter of the rod after alloy cladding is φ86.3-86.8 mm; the second alloy powder is composed of the following components in percentage by weight: 18.2% Cr, 1.3% Ni, 0.6% Mn, 0.11% C, 0.88% W, and Fe as a balance (the carbon content is only 0.11%, which is a low-carbon alloy, ensuring it has good welding performance and will not cause cracking and other problems during the cladding process; secondly, adding 0.88% W to the alloying elements can further increase the hardness of the alloy and enhance its wear resistance). The cladding parameters of the laser cladding are: laser power 600 W, spot diameter 3.2 mm; powder feed rate 0.8 r / min; scanning speed 300 mm / min.

[0038] (5) Driving gear processing: The driving gear intermediate V02 is processed with characteristic structure, and the outer circle, core features and tooth shape are processed in sequence to the driving gear of the specified size. The driving gear after cladding processing is as follows Figure 3b As shown, the functionally gradient high hardness and wear-resistant driving gear is finally obtained.

[0039] like Figure 1-Figure 2As shown, the thickness of the first alloy cladding layer of the driving gear finally obtained is the same as the tooth height (the thickness of the first alloy layer is the same as the tooth height to ensure that after the first alloy cladding layer is clad, a 0.5-2mm thickness margin is reserved for the subsequent high-hardness alloy cladding. If the thickness of the first alloy cladding layer is too high, the subsequent high-hardness second alloy cladding layer will be completely processed away during the processing; if the thickness is too low, the subsequent high-hardness alloy layer cladding thickness is too thick, which may cause the outermost high-hardness alloy layer to crack), and its thickness starts from at least 0.5mm below the root circle of the tooth (that is, the original core bar V0 diameter is 0.5-2mm less than the root circle diameter of the tooth). This design can effectively avoid stress concentration at the cladding interface (metallurgical bonding interface between the cladding area and the core bar).

[0040] like Figure 4 As shown, the resulting drive gear exhibits a gradient hardness from its outer surface to the core bar base. After surface heat treatment, the surface hardness of the first cladding layer is 53-58 HRC. The tooth tip hardness of the resulting functionally graded, high-hardness, wear-resistant oil well logging drive gear is ≥62 HRC. The effective hardened layer depth of the functionally graded, high-hardness, wear-resistant oil well logging drive gear, i.e., the surface depth reaching a hardness of 50 HRC or higher, is ≥6 mm.

[0041] In addition, the final process of this embodiment is a machining process of structural features rather than a heat treatment, which avoids deformation caused by the heat treatment process and is conducive to ensuring the dimensional accuracy of the driving gear.

[0042] The above are only preferred embodiments of the present invention. It should be understood that the description of the above embodiments is only used to help understand the method and core ideas of the present invention, and is not used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, etc. made within the ideas and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a functionally gradient high-hardness wear-resistant drive gear, characterized in that: The steps include: S1: Using a first alloy powder as a laser cladding raw material, laser cladding is performed on the outer cylindrical surface of a bar to obtain a driving gear intermediate V01 with a first alloy cladding layer; the first alloy powder is composed of the following components in percentage by weight: 0.4-0.5% C, 0.17-0.37% Si, 0.3-1.2% Mn, 0.6-1.0% Cr, 0.10-0.35% Mo, 2.25-4.25% Ni, and the balance Fe; S2: performing surface heat treatment on the driving gear intermediate V01 obtained in step S1 to increase its surface hardness; S3: Using a second alloy powder as a laser cladding raw material, laser cladding is performed on the outer cylindrical surface of the driving gear intermediate V01 processed in step S2 to obtain a driving gear intermediate V02 with a first alloy cladding layer and a second alloy cladding layer; the second alloy powder is composed of the following components in percentage by weight: 16-20% Cr, 0-1.5% Ni, 0-0.8% Mn, 0.1-0.3% C, 0.5-1.2% W, and the balance Fe; S4: performing characteristic structural processing on the driving gear intermediate V02 to obtain the functionally gradient high hardness wear-resistant driving gear; The thickness of the first alloy cladding layer is the same as the tooth height, and starts from 0.5-2 mm below the tooth root circle and ends at 0.5-2 mm below the tooth top circle.

2. The method for preparing a functionally graded, high-hardness, wear-resistant drive gear according to claim 1, characterized in that: The thickness of the second alloy cladding layer starts from the outer circumference of the first alloy cladding layer, that is, starts from 0.5-2 mm below the tooth top circle and ends at 0.5-2 mm above the tooth top circle.

3. The method for preparing a functionally graded, high-hardness, wear-resistant drive gear according to claim 1, characterized in that: After the surface heat treatment in step S2, the surface hardness of the first alloy cladding layer is 53-58 HRC; The tooth top hardness of the functionally gradient high-hardness wear-resistant drive gear obtained after the processing in step S4 is ≥62HRC.

4. The method for preparing a functionally graded, high-hardness, wear-resistant drive gear according to claim 3, characterized in that: The effective hardened layer depth of the functionally graded high-hardness wear-resistant driving gear, that is, the surface depth with a hardness of 50HRC or above, is ≥6mm.

5. The method for preparing a functionally gradient high-hardness wear-resistant driving gear according to claim 1, characterized in that: The cladding parameters of the laser cladding in step S1 are: laser power 1200-1500 W, spot diameter 2-4 mm; powder feeding rate 0.1-1 r / min; scanning speed 500-1000 mm / min.

6. The method for preparing a functionally gradient high-hardness wear-resistant driving gear according to claim 1, characterized in that: The cladding parameters of the laser cladding in step S3 are: laser power 500-800 W, spot diameter 3-4 mm; powder feeding rate 0.5-1.1 r / min; scanning speed 300-400 mm / min.

7. The method for preparing a functionally graded, high-hardness, wear-resistant drive gear according to claim 1, characterized in that: The surface heat treatment in step S2 is medium frequency induction hardening treatment.

8. The method for preparing a functionally graded, high-hardness, wear-resistant driving gear according to claim 1, characterized in that: Before step S1, the bar is ground and ultrasonically cleaned.

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