A corrosion and wear resistant coating for a petroleum motor rotor and a spraying method thereof

Abstract

This invention provides an anti-corrosion and wear-resistant coating for an oilfield motor rotor and its spraying method, belonging to the field of thermal spraying technology. The method includes the following steps: machining, degreasing, surface roughening, and preheating the oilfield motor rotor sequentially to obtain the part to be sprayed; spraying, sealing, rough polishing, and fine polishing are performed on the part to be sprayed sequentially to obtain the anti-corrosion and wear-resistant coating for the oilfield motor rotor; the part to be sprayed includes peaks, valleys, upslopes, downslopes, the junction of valleys and upslopes, and the junction of valleys and downslopes; tungsten carbide powder is used for spraying. This invention, by specifically defining the spraying process, makes the coating thickness easily controllable, resulting in a very uniform coating thickness across all parts of the rotor, with a thickness uniformity difference within 0.03 mm (3 mils). Furthermore, this invention utilizes tungsten carbide powder for spraying, resulting in a coating porosity of <1%, good corrosion resistance, and high bonding strength and hardness.

Description

Technical Field

[0001] This invention relates to the field of thermal spraying technology, and more particularly to an anti-corrosion and wear-resistant coating for a petroleum motor rotor and its spraying method. Background Technology

[0002] The working principle of an oil screw drill bit / oil motor rotor is as follows: High-pressure drilling fluid (mud) flows into the screw drill bit and is forced downwards through the helical channel between the stator (rubber bushing) and the oil motor rotor (referred to as rotor or screw), forming high-pressure and low-pressure chambers between the stator and rotor. The rotor shifts under the pressure difference, generating eccentric torque. As the drilling fluid (mud) continues to flow downwards, new high-pressure and low-pressure chambers are created, forcing the rotor to shift further under the pressure difference. With the continuous downward flow of the drilling fluid, new high-pressure and low-pressure chambers are constantly formed, and the rotor continuously shifts under the pressure difference, thus causing it to rotate. In short, the drilling fluid (mud) flows through the motor, creating a pressure difference at the motor's inlet and outlet, driving the rotor to rotate. The torque and speed are then transmitted to the drill bit through the universal joint and drive shaft, converting the pressure energy of the drilling fluid (mud) into mechanical energy, which drives the drill bit to rotate and perform the drilling action. Figure 1 This is a schematic diagram of the rotor and stator assembly structure.

[0003] The conventional anti-corrosion coating for oilfield motor rotors is electroplated hard chrome. Reservoir protection is a crucial aspect of horizontal well technology, especially for low-permeability tight reservoirs with inherently low production capacity. Using saturated brine drilling fluid effectively controls the impact of formation salts on drilling fluid performance, inhibits salt dissolution, seals bedding fractures, and prevents various downhole complications and accidents caused by wellbore enlargement and collapse in salt-bearing formations. However, in actual use of saturated brine drilling fluid, dissolved salts such as carbonates and sulfates in the bottom layer increase the conductivity of the drilling fluid, accelerating corrosion and causing severe corrosion of drilling equipment or components (chloride ion and high-mineralization corrosion). For oilfield motor rotors, chrome plating fails within 50 hours, failing to meet lifespan requirements. Tungsten carbide coatings offer superior corrosion and wear resistance compared to chrome plating and have been used in oilfield motor rotors. However, the complex structure of oilfield motor rotors and the poor uniformity of tungsten carbide coating thickness in existing technologies present challenges. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an anti-corrosion and wear-resistant coating for an oilfield motor rotor and a spraying method thereof. The spraying method provided by this invention produces an anti-corrosion and wear-resistant coating with good thickness uniformity on the oilfield motor rotor.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for spraying an anti-corrosion and wear-resistant coating on a petroleum motor rotor, comprising the following steps:

[0007] The petroleum motor rotor is sequentially machined, degreased, roughened, and preheated to obtain the part to be coated.

[0008] The parts to be coated are sequentially sprayed, sealed, rough polished, and fine polished to obtain an anti-corrosion and wear-resistant coating for the rotor of a petroleum motor.

[0009] The parts to be sprayed include peaks, valleys, upslopes, downslopes, the junction of valleys and upslopes, and the junction of valleys and downslopes;

[0010] The spraying uses tungsten carbide powder;

[0011] The spraying process includes the following steps:

[0012] Step (1): Rotate the part to be sprayed counterclockwise and perform a first flame spray on the upslope. The flame of the first flame spray is perpendicular to the upslope. A tungsten carbide coating will be formed at the junction of the peak, upslope, valley bottom, valley bottom and upslope. A tungsten carbide coating will not be formed at the junction of the downslope, valley bottom and downslope.

[0013] Step (2): Rotate the sprayed part after step (1) clockwise and perform a second flame spray on the downhill. The flame of the second flame spray is perpendicular to the downhill. A tungsten carbide coating will be formed at the junction of the peak, downhill, valley bottom, valley bottom and downhill. A tungsten carbide coating will not be formed at the junction of the uphill, valley bottom and uphill.

[0014] Step (3): Rotate the sprayed part after step (2) and perform a third flame spray on the peak, valley bottom, upslope and downslope. The junction of the valley bottom and upslope and the junction of the valley bottom and downslope are thinner than the thickness of the tungsten carbide coating formed on the peak, valley bottom, upslope and downslope.

[0015] Step (4): Rotate the sprayed part after step (3) counterclockwise and perform flame spraying on the junction of the valley bottom and the upslope and the junction of the valley bottom and the downslope.

[0016] Preferably, the spraying parameters include: the rotation speed of the part to be sprayed is 50-80 r / min, the spray gun moving speed is 400-450 mm / min, and the spraying distance between the spray gun and the rotor is 360-380 mm.

[0017] Preferably, the spraying is flame spraying, and the flame spraying pressure is: oxygen 230-270 psi, kerosene 5-10 psi, cooling water minimum pressure 40 psi, maximum pressure 60 psi, carrier gas nitrogen minimum pressure 80 psi, maximum pressure 100 psi, flow rate: oxygen 2000 SCFH, kerosene 6.3 GPH, carrier gas 23 SCFH, powder feed rate 60-70 g / min.

[0018] Preferably, the tungsten carbide powder comprises the following elements in mass percentage: Co 9.5-11.5%, C 5.0-5.6%, Cr 3.5-4.5%, Fe <0.2%, O <1%, unavoidable impurities <0.2%, and the balance W.

[0019] Preferably, the tungsten carbide powder has an average particle size of 15–45 μm.

[0020] Preferably, the rough polishing includes sequentially performing rough polishing at the valley bottom, rough polishing at the peak, and rough polishing on the ups and downslopes.

[0021] Preferably, the coarse polishing of the valley bottom uses a 200-mesh diamond flap wheel; the coarse polishing of the peak and the coarse polishing of the upper and lower slopes both include the use of 120-mesh, 200-mesh, and 300-mesh diamond abrasive belts in sequence.

[0022] Preferably, the fine polishing includes sequentially using 400-mesh, 600-mesh, and 800-mesh wide diamond abrasive belts to polish the peaks and slopes.

[0023] The present invention also provides an anti-corrosion and wear-resistant coating for a petroleum motor rotor prepared by the spraying method described above.

[0024] Preferably, the anti-corrosion and wear-resistant coating of the petroleum motor rotor has a thickness of 0.23-0.3 mm, a hardness of 1100-1300 HV0.3, a bonding strength greater than 75 MPa, a porosity of <1%, and a thickness uniformity of less than 0.03 mm.

[0025] This invention provides a method for spraying an anti-corrosion and wear-resistant coating on a petroleum motor rotor, comprising the following steps: machining, degreasing, surface roughening, and preheating the petroleum motor rotor sequentially to obtain a part to be sprayed; spraying, sealing, rough polishing, and fine polishing are performed on the part to be sprayed sequentially to obtain an anti-corrosion and wear-resistant coating on the petroleum motor rotor; the part to be sprayed includes peaks, valleys, upslopes, downslopes, the junction of the valley and the upslope, and the junction of the valley and the downslope; the spraying uses tungsten carbide powder; the spraying includes the following steps: Step (1): rotating the part to be sprayed counterclockwise, performing a first flame spraying on the upslope, the flame of the first flame spraying being perpendicular to the upslope, and a tungsten carbide coating being formed at the peaks, upslopes, valleys, the junction of the valley and the upslope, while no tungsten carbide coating is formed at the downslope, the junction of the valley and the downslope. Tungsten carbide coating; Step (2): Rotate the sprayed part after step (1) clockwise and perform a second flame spray on the downhill. The flame of the second flame spray is perpendicular to the downhill. A tungsten carbide coating will be formed at the junction of the peak, downhill, valley, valley and downhill. A tungsten carbide coating will not be formed at the junction of the uphill, valley and uphill. Step (3): Rotate the sprayed part after step (2) and perform a third flame spray on the peak, valley, uphill and downhill. The junction of the valley and uphill and the junction of the valley and downhill are thinner than the tungsten carbide coating formed by the peak, valley, uphill and downhill. Step (4): Rotate the sprayed part after step (3) counterclockwise and perform flame spray on the junction of the valley and uphill and the junction of the valley and downhill.

[0026] The present invention specifically defines the spraying process, and the resulting coating thickness is easy to control. The coating thickness of each part of the rotor is very uniform, and the thickness uniformity difference is within 0.03mm (3 mils).

[0027] Furthermore, this invention utilizes tungsten carbide powder for spraying, resulting in a coating with a porosity of <1%, excellent corrosion resistance, high bonding strength and hardness, and a more environmentally friendly spraying process than electroplating chromium. Chromium is highly harmful to the human body, and the waste liquid from electroplating is not treated to standard, and indiscriminate discharge aggravates soil damage. The spraying method of this invention is operated in a closed space, and the generated dust can be effectively discharged through a dust removal system. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the rotor and stator assembly structure;

[0029] Figure 2 This diagram shows the peak, valley, uphill, downhill, the junction of valley and uphill, and the junction of valley and downhill of a petroleum motor rotor. 1 represents uphill, 2 represents valley, 3 represents downhill, 4 represents peak, 5 represents the junction of valley and uphill, and 6 represents the junction of valley and downhill.

[0030] Figure 3 This is a schematic diagram of flame spraying at the junction of the valley floor and the uphill slope;

[0031] Figure 4 This is a schematic diagram of flame spraying at the junction of the valley floor and the downhill slope;

[0032] Figure 5 and 6 This is a schematic diagram of the valley bottom.

[0033] Figure 7 This is a schematic diagram of the rough traverse peak and the rough traverse uphill and downhill slopes;

[0034] Figure 8 These are optical photographs of the sandblasting process before and after in Example 1;

[0035] Figures 9-11 Optical photographs taken during the spraying process;

[0036] Figure 12 An optical photograph after fine polishing;

[0037] Figure 13 A cross-sectional metallographic image of the corrosion-resistant and wear-resistant coating for the petroleum motor rotor at low magnification.

[0038] Figure 14 High-magnification cross-sectional metallographic image of the corrosion-resistant and wear-resistant coating for the petroleum motor rotor;

[0039] Figure 15 An optical photograph of the petroleum motor rotor with anti-corrosion and wear-resistant coating prepared in Example 1 after use. Detailed Implementation

[0040] This invention provides a method for spraying an anti-corrosion and wear-resistant coating on a petroleum motor rotor, comprising the following steps:

[0041] The petroleum motor rotor is sequentially machined, degreased, roughened, and preheated to obtain the part to be coated.

[0042] The parts to be coated are sequentially sprayed, sealed, rough polished, and fine polished to obtain an anti-corrosion and wear-resistant coating for the rotor of a petroleum motor.

[0043] The parts to be sprayed include peaks, valleys, upslopes, downslopes, the junction of valleys and upslopes, and the junction of valleys and downslopes;

[0044] The spraying uses tungsten carbide powder;

[0045] The spraying process includes the following steps:

[0046] Step (1): Rotate the part to be sprayed counterclockwise and perform a first flame spray on the upslope. The flame of the first flame spray is perpendicular to the upslope. A tungsten carbide coating will be formed at the junction of the peak, upslope, valley bottom, valley bottom and upslope. A tungsten carbide coating will not be formed at the junction of the downslope, valley bottom and downslope.

[0047] Step (2): Rotate the sprayed part after step (1) clockwise and perform a second flame spray on the downhill. The flame of the second flame spray is perpendicular to the downhill. A tungsten carbide coating will be formed at the junction of the peak, downhill, valley bottom, valley bottom and downhill. A tungsten carbide coating will not be formed at the junction of the uphill, valley bottom and uphill.

[0048] Step (3): Rotate the sprayed part after step (2) and perform a third flame spray on the peak, valley bottom, upslope and downslope. The junction of the valley bottom and upslope and the junction of the valley bottom and downslope are smaller than the thickness of the tungsten carbide coating formed on the peak, valley bottom, upslope and downslope.

[0049] Step (4): Rotate the sprayed part after step (3) counterclockwise and perform flame spraying on the junction of the valley bottom and the upslope and the junction of the valley bottom and the downslope.

[0050] This invention involves sequentially machining, degreasing, surface roughening, and preheating a petroleum motor rotor to obtain a part to be coated.

[0051] The present invention does not have any special limitation on the source of the oil motor rotor; commercially available oil motor rotors known to those skilled in the art can be used.

[0052] In this invention, the material of the oil motor rotor is preferably carbon steel that has undergone quenching and tempering treatment, more preferably 45# carbon steel or 42CrMo carbon steel, and the quenching and tempering hardness of the carbon steel is preferably 270-350HB.

[0053] In this invention, the Ra of the rotor obtained after machining is preferably ≤1.6μm. Preferably, the rotor of the petroleum motor is first milled into the required profile using a rotor milling machine, and the surface roughness Ra is preferably ≤3.2μm, and then polished to Ra ≤1.6μm.

[0054] The present invention does not have any particular limitation on the degreasing method, and any method known to those skilled in the art can be used, such as cleaning with acetone or solvent oil or flame treatment.

[0055] In this invention, the surface roughening is preferably sandblasting, and the surface roughness Ra after roughening is preferably 5 to 7 μm.

[0056] In this invention, the oil motor rotor is preferably clamped in a clamping machine tool and placed in a sandblasting room. The sandblasting treatment is performed using a pressure sandblasting machine with compressed air. The preferred parameters include: 20-40 mesh diamond abrasive, a spray gun pressure of 0.4-0.6 MPa, a compressed air supply pressure of 0.6-0.8 MPa, and a sandblasting distance of 100-150 mm between the sandblasting gun and the rotor.

[0057] In this invention, the oil motor rotor is preferably subjected to the sandblasting treatment while rotating, and the rotation speed is preferably 50 to 80 r / min.

[0058] In this invention, the oil motor rotor rotates counterclockwise when spraying the upper position and clockwise when spraying the lower position, once for each position. The spraying is preferably carried out within 2 hours after the sandblasting is completed. If more than 2 hours have passed, the sandblasting must be repeated. This is because the outer surface of the oil motor rotor comes into contact with moisture in the air, which causes oxidation and affects the bonding strength between the coating and the substrate.

[0059] In this invention, the preheating temperature is preferably 60-120°C.

[0060] The present invention preferably utilizes a supersonic flame to preheat the rotor of the petroleum motor.

[0061] In this invention, the oil motor rotor is preferably preheated while rotating, and the rotation speed is preferably 50-80 r / min.

[0062] After obtaining the part to be coated, the present invention sequentially performs spraying, sealing, rough polishing and fine polishing on the part to be coated to obtain an anti-corrosion and wear-resistant coating for the oil motor rotor.

[0063] In this invention, the spraying equipment is preferably the Praxair HP / HVOF JP8000 supersonic flame sprayer from the United States. The Praxair HP / HVOF JP8000 supersonic flame sprayer has a supersonic flame temperature of up to 3000℃, a spray particle flight speed of up to 1200 m / s, closed-loop control, and stable operating parameters.

[0064] In this invention, the tungsten carbide powder preferably comprises the following elements by mass percentage: Co 9.5–11.5%, C 5.0–5.6%, Cr 3.5–4.5%, Fe <0.2%, O <1%, unavoidable impurities <0.2%, and the balance W. More preferably, it comprises the following elements by mass percentage: Co 10.2%, C 5.54%, Cr 3.91%, Fe 0.15%, O <0.05%, unavoidable impurities, and the balance W. This invention does not impose any particular limitation on the source of the tungsten carbide powder; it can be obtained from commercially available products well known to those skilled in the art or by conventional sintering methods.

[0065] In this invention, the average particle size of the tungsten carbide powder is preferably 15 to 45 μm.

[0066] In this invention, the melting point of the tungsten carbide powder is preferably 2860±5℃.

[0067] In this invention, the spraying parameters preferably include: a rotation speed of 50-80 r / min for the part to be sprayed, more preferably 60-70 r / min; a spray gun moving speed of 400-450 mm / min, more preferably 420-430 r / min; and a spraying distance of 360-380 mm between the spray gun and the rotor, more preferably 370-375 r / min.

[0068] In this invention, the spraying is preferably flame spraying, and the flame spraying pressure is preferably: oxygen 230-270 psi, kerosene 5-10 psi (0.3-0.7 bar), the minimum pressure of cooling water is preferably 40 psi (2.7 bar), the maximum pressure is preferably 60 psi (4.1 bar), the minimum pressure of carrier gas nitrogen is preferably 80 psi (5.4 bar), the maximum pressure is preferably 100 psi (6.9 bar), the flow rate is preferably: oxygen 2000 SCFH, kerosene 6.3 GPH, carrier gas 23 SCFH, and the powder feed rate is preferably 60-70 g / min.

[0069] Figure 2 This diagram illustrates the peaks, valleys, uphill sections, downhill sections, and the junctions of valleys and uphill sections on an oil motor rotor. 1 represents an uphill section (red), 2 a valley (yellow), 3 a downhill section (white), 4 a peak (green), 5 a valley-uphill junction (black), and 6 a valley-downhill junction (purple). The diagram is further illustrated below. Figure 2 The spraying process will be described.

[0070] Step (1): Rotate the part to be sprayed counterclockwise and perform a first flame spray on the uphill 1. The flame of the first flame spray is perpendicular to the uphill 1. A tungsten carbide coating will be formed on the peak 4, uphill 1, valley 2, and the junction of the valley and the uphill 5. A tungsten carbide coating will not be formed on the downhill 3 and the junction of the valley and the downhill 6. The angle of the spray gun is preferably tilted to the left during the first flame spray.

[0071] Step (2): Rotate the coated part after step (1) clockwise and perform a second flame spray on the downhill slope. The flame of the second flame spray is perpendicular to the downhill slope 3. A tungsten carbide coating will be formed on the peak 4, downhill slope 3, valley bottom 2, valley bottom and downhill slope junction 6. A tungsten carbide coating will not be formed on the uphill slope 1 and valley bottom and uphill slope junction 5. The angle of the spray gun is preferably tilted to the right when performing the second flame spray.

[0072] Step (3): Rotate the sprayed part after step (2) (either counterclockwise or clockwise) to perform a third flame spray on the peak 4, valley 2, uphill 1 and downhill 3. At this time, tungsten carbide coatings will be formed on the peak 4, valley 2, uphill 1 and downhill 3. However, the valley bottom and uphill junction 5 and valley bottom and downhill junction 6 will be blocked because the position of the peak 4 is too high due to the rotation of the rotor. The powder accumulation is too small, that is, the valley bottom and uphill junction 5 and valley bottom and downhill junction 6 are thinner than the tungsten carbide coatings formed by the peak 4, valley 2, uphill 1 and downhill 3.

[0073] Step (4): Rotate the sprayed part after step (3) counterclockwise, and perform flame spraying on the junction of the valley bottom and the upslope and the junction of the valley bottom and the downslope. Figure 3 This is a schematic diagram of flame spraying at the junction of the valley floor and the uphill slope. Figure 4 This is a schematic diagram of flame spraying at the junction of the valley floor and the downhill slope.

[0074] In this invention, the vertical is defined as 90°±15°.

[0075] In this invention, during the spraying process, it is preferable to use a coating thickness gauge to repeatedly detect the coating thickness.

[0076] In this invention, during the spraying process, it is preferable to use a temperature controller to detect the temperature of the rotor to prevent workpiece deformation. The temperature is preferably no greater than 150°C. During the spraying process, it is preferable to control the tightness of the clamping machine tool tailstock. It should not be too tight, otherwise the rotor will bend and deform.

[0077] In this invention, the thickness of the coating is preferably 0.25 to 0.3 mm.

[0078] In this invention, the sealing is preferably achieved by brushing or spraying a sealing agent onto the outer surface of the rotor, ensuring that the sealing agent evenly and thoroughly penetrates the coating. This invention does not impose any specific limitations on the source of the sealing agent or the specific methods of brushing or spraying.

[0079] In this invention, the rough polishing preferably includes sequentially performing rough polishing at the valley bottom, rough polishing at the peak, and rough polishing at the top and bottom slopes.

[0080] In this invention, the coarse polishing of the valley bottom preferably uses a 200-mesh diamond flap wheel; the coarse polishing of the peak and the coarse polishing of the upper and lower slopes preferably include the use of 120-mesh, 200-mesh and 300-mesh diamond abrasive belts in sequence.

[0081] The present invention preferably employs a polishing machine to clamp the rotor. The rotor is supported by the polishing machine's top head on one of the valleys 2 of the rotor, and the polishing wheel is adjusted left and right to be in the middle of the valley 2 to be polished. The rotor is rotated by the movement of the polishing machine. Figure 5 Then, the polishing head is used to polish each valley of the rotor sequentially until the maximum thickness required by the process is achieved. Figure 6 .

[0082] In this invention, the use of 120-mesh diamond abrasive belt for the rough polishing peak and rough polishing uphill and downhill slopes preferably includes the following steps:

[0083] ① Adjust the angle between the rotor and the 120-mesh diamond abrasive belt (see...) Figure 7 Position 3), this position is the junction of the polishing valley bottom and the upslope or the junction of the valley bottom and the downslope. The polishing machine rotation speed is 50 r / min, the polishing machine travel speed is 450 mm / min, the rotor rotates clockwise, travels from one end of the rotor to the other, polishing the junction of the upslope and the valley bottom, then the rotor rotates counterclockwise, polishing the junction of the downslope and the valley bottom, and then polishes back from the other end. It is preferred to achieve Ra 0.4~0.8μm. If Ra does not reach the desired level, it is preferred to repeat the operation to reduce the roughness.

[0084] ② Adjust the angle between the rotor and the 120-mesh diamond abrasive belt (see...) Figure 7 Position 2), this position is the polishing slope (including the upper slope and the lower slope). Let the rotor rotate clockwise and walk from one end of the rotor to the other end to polish the upper slope position. Then let the rotor rotate counterclockwise and polish the lower slope position. Polish back from the other end. It is preferable to achieve Ra 0.4~0.8μm. If Ra cannot be achieved, it is preferable to repeat the operation.

[0085] ③ Adjust the angle between the rotor and the 120-mesh diamond abrasive belt (see...) Figure 7(Position 1 in the middle), at this position, the position of the polishing peak, let the rotor rotate clockwise, walk from one end of the rotor to the other end, polishing the position of the peak, then let the rotor rotate counterclockwise, continue polishing the position of the peak, polishing back from the other end, preferably achieving Ra 0.4~0.8μm, if Ra cannot be achieved, it is preferable to repeat the operation.

[0086] In this invention, the width of the 120-mesh diamond abrasive belt is preferably 30 mm, and the length is preferably 2500 mm.

[0087] In this invention, the width of the 200-mesh diamond abrasive belt is preferably 30 mm, and the length is preferably 2500 mm.

[0088] In this invention, the width of the 300-mesh diamond abrasive belt is preferably 30 mm, and the length is preferably 2500 mm.

[0089] Preferably, the fine polishing includes sequentially using 400-mesh, 600-mesh, and 800-mesh wide diamond abrasive belts to polish the peaks and slopes.

[0090] In this invention, the preferred steps for using 200-mesh and 300-mesh diamond abrasive belts for rough polishing peaks and rough polishing slopes include:

[0091] Repeat steps ①②③ above, replacing the 120-mesh diamond abrasive belt with a 200 or 300-mesh diamond abrasive belt.

[0092] In this invention, the roughness Ra of the coating after coarse polishing is preferably 0.2 to 0.4 μm. If Ra does not reach this level, the operation should be repeated.

[0093] In this invention, the fine polishing preferably includes polishing with diamond abrasive belts of 400 mesh, 600 mesh, and 800 mesh widths in sequence, and with both upper and lower slopes.

[0094] In this invention, the fine polishing preferably includes the following steps: repeating steps ①②③ above, replacing the 120-mesh diamond abrasive belt with a 400, 600, or 800-mesh diamond abrasive belt.

[0095] In this invention, the fine polishing does not thin the coating; its function is to reduce roughness. It is preferably repeated to achieve a roughness Ra≤0.2μm. The lower the roughness, the less wear the stator rubber (which is stationary) will experience when the rotor rotates. A roughness Ra≤0.2μm can reduce friction and drag, effectively control the interference fit dimensions between the rotor and the stator, and extend the service life.

[0096] The present invention also provides an anti-corrosion and wear-resistant coating for a petroleum motor rotor prepared by the spraying method described above.

[0097] In this invention, the thickness of the anti-corrosion and wear-resistant coating of the petroleum motor rotor is preferably 0.25-0.3 mm, the hardness is preferably 1100-1300 HV0.3, the bonding strength is preferably greater than 75 MPa, the porosity is preferably <1%, and the thickness uniformity is preferably less than 0.03 mm.

[0098] In this invention, the thickness is preferably 0.27 to 0.27 mm.

[0099] In this invention, the porosity is preferably 0.3% to 0.6%, and the lower the porosity, the better the corrosion resistance.

[0100] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0101] Example 1

[0102] The rotor is made of tempered carbon steel 45# with a hardness of 350HB. It is then milled into the required profile using a rotor milling machine, achieving a surface roughness Ra of 3.2μm. After polishing to Ra 1.6μm, the rotor is degreased with acetone. The degreased rotor is then clamped in a clamping machine and sandblasted in a sandblasting room using a pressure sandblasting machine with compressed air. The parameters are: 20-40 mesh diamond abrasive, gun pressure 0.6MPa, compressed air supply pressure 0.8MPa, sandblasting gun distance 150mm, clamping rotation speed 80r / min, and gun movement speed 500mm / min. The rotor rotates counterclockwise when sandblasting the upper part and clockwise when sandblasting the lower part, repeating once for each part. The surface roughness Ra is achieved to be 5-7μm. Coating is performed within 2 hours after sandblasting.

[0103] Figure 8 These are optical photographs before and after sandblasting.

[0104] Spraying WC (tungsten carbide) coating

[0105] Equipment: The spraying was performed using a Praxair HP / HVOF JP8000 supersonic flame spraying system from the USA. The supersonic flame temperature was 3000℃, the particle velocity was 1200 m / s, and the system featured closed-loop control and stable operating parameters. The spraying material was tungsten carbide powder with a particle size of 15–45 μm. The WC powder had a melting point of 2860℃ and contained the following elements by mass percentage: Co 10.2%, C 5.54%, Cr 3.91%, Fe 0.15%, O <0.05%, unavoidable impurities, and a balance of W.

[0106] Equipment parameter settings: ① Pressure: Oxygen 230~270psi, Kerosene 5~10psi (0.3~0.7bar), Cooling water minimum pressure 40psi (2.7bar), maximum pressure 60psi (4.1bar), Carrier gas (nitrogen) minimum pressure 80psi (5.4bar), maximum pressure 100psi (6.9bar);

[0107] ② Flow rate: Oxygen 2000 SCFH, Kerosene 6.3 GPH, Carrier gas 23 SCFH;

[0108] ③ Powder delivery rate: 60-70g / min;

[0109] ④ 6-inch barrel;

[0110] Rotor clamping and three-dimensional walking mechanism parameter settings: rotor rotation speed 70r / min, spray gun moving speed 420mm / min, spray gun and rotor spraying distance 370mm.

[0111] Areas and methods of spraying:

[0112] The rotor is divided into the following sections: peak 4 (green), valley 2 (yellow), uphill 1 (red), downhill 3 (white), the junction of valley and uphill 5 (black), and the junction of valley and downhill 6 (purple). See [link / description]. Figure 2 .

[0113] First, spray the upper position: the rotor rotates counterclockwise, and when spraying the upper position, the spray gun is tilted to the left to ensure that the flame of the spray gun is perpendicular to the upper slope of the rotor. At this time, the peak 4, the upper slope 1, the valley bottom 2, and the junction of the valley bottom and the upper slope 5 will be sprayed with tungsten carbide coating, while the lower slope 3 and the junction of the valley bottom and the lower slope 6 will not be sprayed with tungsten carbide coating.

[0114] Spraying the lower position: The rotor rotates clockwise. When spraying the lower position, the spray gun is tilted to the right to ensure that the flame of the spray gun is perpendicular to the rotor's downward slope. At this time, the peak 4 and the lower slope 3, the valley bottom 2, and the junction of the valley bottom and the lower slope 6 will be sprayed with tungsten carbide coating. The upper slope 1 and the junction of the valley bottom and the upper slope 5 will not be sprayed with tungsten carbide coating.

[0115] Spraying in the middle position: The rotor can be rotated counterclockwise or clockwise. The spray gun is forward and the flame of the spray gun is perpendicular to the rotor. At this time, the peak 4, valley 2, uphill 1, and downhill 3 of the rotor will be sprayed with tungsten carbide coating. However, the junction of the valley and the uphill 5 and the junction of the valley and the downhill 6 will be blocked because the peak of the rotor is too high. The powder accumulation is too small and the coating thickness is thinner than other parts.

[0116] Spraying at the junction of the valley bottom and the uphill slope, point 5: Rotator rotates counterclockwise.

[0117] Spraying at the junction of the valley bottom and the downhill slope, position 6: The rotor rotates counterclockwise.

[0118] During the spraying process, the coating thickness is repeatedly checked using a coating thickness gauge. Areas with thinner coatings are then sprayed. The coating thickness must meet the process requirements and be uniform, with the overall thickness difference between different areas within 0.03mm (3 microns). The coating thickness is 0.25–0.3mm (including polishing). During spraying, the rotor temperature is monitored using a temperature controller to prevent workpiece deformation, keeping it below 150℃. Care must be taken to ensure the tightness of the machine tool tailstock during spraying; it should not be too tight, otherwise the rotor will bend and deform.

[0119] Sealing: Apply a sealing agent to the outer surface of the rotor to ensure that the sealing agent is evenly and fully penetrates the coating.

[0120] Figures 9-11 These are optical photographs taken during the spraying process.

[0121] polishing:

[0122] Valley bottom polishing: Using a polishing machine and polishing head, and a 200-grit diamond flap wheel, the valley bottom is polished. The method includes the following steps:

[0123] 1. The rotor is clamped using a polishing machine.

[0124] 2. Place the polishing machine's top head against one of the valleys of the rotor, adjust the polishing wheel left and right to the center of the valley to be polished, and use the polishing machine's movement to drive the rotor to rotate. See... Figure 5 ;

[0125] 3. Use a polishing head to polish each valley of the rotor sequentially until the maximum thickness required by the process is achieved. See [link / reference]. Figure 6 ;

[0126] Rough peaks and uphill / downhill slopes:

[0127] 1. Use 120-mesh, 30mm wide diamond abrasive belt to polish the peaks and slopes. The steps are as follows:

[0128] ① Adjust the angle between the rotor and the 120-mesh diamond abrasive belt (see...) Figure 7 Position 3), this position is the junction of the valley bottom and the upslope or the valley bottom and the downslope. The polishing machine rotation speed is 50 r / min, the polishing machine travel speed is 450 mm / min, the rotor rotates clockwise, travels from one end of the rotor to the other, polishing the junction of the upslope and the valley bottom, then the rotor rotates counterclockwise, polishing the junction of the downslope and the valley bottom, and then polishes back from the other end to achieve Ra 0.4~0.8μm. If Ra does not reach the target, repeat the operation to reduce the roughness.

[0129] ② Adjust the angle between the rotor and the 120-mesh diamond abrasive belt (see...) Figure 7 Position 2), this position is the polishing slope (including the upper slope and the lower slope). Let the rotor rotate clockwise and walk from one end of the rotor to the other end to polish the upper slope position. Then let the rotor rotate counterclockwise and polish the lower slope position. Polish back from the other end to achieve Ra 0.4~0.8μm. If Ra cannot be achieved, repeat the operation.

[0130] ③ Adjust the angle between the rotor and the 120-mesh diamond abrasive belt (see...) Figure 7 (Position 1 in the middle), at this position, the position of the polishing peak, let the rotor rotate clockwise, walk from one end of the rotor to the other end, polishing the position of the peak, then let the rotor rotate counterclockwise, continue polishing the position of the peak, polishing back from the other end, to achieve Ra 0.4~0.8μm. If Ra cannot be achieved, repeat the operation.

[0131] 2. Use 200-mesh and 300-mesh diamond abrasive belts, 30mm wide, to polish the peaks and blast the slopes.

[0132] Steps: Repeat steps ①②③. Control the coating thickness (polishing amount within 1-2 microns) to ensure the rotor tungsten carbide coating thickness is 0.25-0.26 mm. Roughness Ra 0.2-0.4 μm.

[0133] Fine polishing

[0134] The peaks were polished using 400-mesh, 600-mesh, and 800-mesh diamond abrasive belts with a width of 30mm, and the polishing was applied to both the upper and lower slopes.

[0135] Steps: Repeat steps ①②③. 400 / 600 / 800 mesh abrasive belts will not thin the coating, they can only reduce roughness. Repeat the operation at each angle until the required roughness Ra ≤ 0.2μm, coating thickness 0.25~0.26mm, hardness 1300HV0.3 is achieved. According to GB / T 8642-2002 Determination of Tensile Bond Strength of Thermal Spraying, the measured bond strength is 75MPa (bonding failure), porosity is 0.3%, and thickness uniformity is 0.02mm.

[0136] Figure 12 This is an optical photograph after fine polishing.

[0137] Figure 13 The metallographic image of the corrosion-resistant and wear-resistant coating on the rotor of the petroleum motor is shown at low magnification. Figure 14 The cross-sectional metallographic image of the corrosion-resistant and wear-resistant coating of the petroleum motor rotor obtained by the present invention shows that the corrosion-resistant and wear-resistant coating of the petroleum motor rotor obtained by the present invention has low porosity and good corrosion resistance.

[0138] The oil motor rotor with anti-corrosion and wear-resistant coating prepared in Example 1 was put into drilling for repeated use. The well entry time was 407 hours, the circulation time was 339 hours, and the pure drilling time was 275 hours. The optical photograph of the oil motor rotor with anti-corrosion and wear-resistant coating after repeated use is shown below. Figure 15 It can be seen that the petroleum motor rotor with anti-corrosion and wear-resistant coating of the present invention has strong corrosion resistance and long service life, which is far greater than 50h.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for spraying an anti-corrosion and wear-resistant coating on a petroleum motor rotor, characterized in that, Includes the following steps: The petroleum motor rotor is sequentially machined, degreased, roughened, and preheated to obtain the part to be coated. The parts to be coated are sequentially sprayed, sealed, rough polished, and fine polished to obtain an anti-corrosion and wear-resistant coating for the rotor of a petroleum motor. The structure of the part to be sprayed includes peaks, valleys, upslopes, downslopes, the junction of the valley and the upslope, and the junction of the valley and the downslope. The spraying uses tungsten carbide powder; The spraying process includes the following steps: Step (1): Rotate the part to be sprayed counterclockwise and perform a first flame spray on the upslope. The flame of the first flame spray is perpendicular to the upslope. A tungsten carbide coating will be formed at the junction of the peak, upslope, valley bottom, valley bottom and upslope. A tungsten carbide coating will not be formed at the junction of the downslope, valley bottom and downslope. Step (2): Rotate the sprayed part after step (1) clockwise and perform a second flame spray on the downhill. The flame of the second flame spray is perpendicular to the downhill. A tungsten carbide coating will be formed at the junction of the peak, downhill, valley bottom, valley bottom and downhill. A tungsten carbide coating will not be formed at the junction of the uphill, valley bottom and uphill. Step (3): Rotate the sprayed part after step (2) and perform a third flame spray on the peak, valley bottom, upslope and downslope. The junction of the valley bottom and upslope and the junction of the valley bottom and downslope are thinner than the thickness of the tungsten carbide coating formed by the peak, valley bottom, upslope and downslope. Step (4): Rotate the sprayed part after step (3) counterclockwise and perform flame spraying on the junction of the valley bottom and the upslope and the junction of the valley bottom and the downslope; The spraying parameters include: the rotation speed of the part to be sprayed is 70 r / min, the spray gun moving speed is 420 mm / min, and the spraying distance between the spray gun and the rotor is 370 mm. The spraying is flame spraying, and the flame spraying pressure is: oxygen 230-270 psi, kerosene 5-10 psi, cooling water minimum pressure 40 psi, maximum pressure 60 psi, carrier gas nitrogen minimum pressure 80 psi, maximum pressure 100 psi, flow rate: oxygen 2000 SCFH, kerosene 6.3 GPH, carrier gas 23 SCFH, powder feed rate 60-70 g / min; The tungsten carbide powder comprises the following elements by mass percentage: Co 10.2%, C 5.54%, Cr 3.91%, Fe 0.15%, O <0.05%, unavoidable impurities <0.2%, and the balance W; The average particle size of the tungsten carbide powder is 15–45 μm; The rough polishing includes sequentially performing rough polishing at the valley bottom, rough polishing at the peak, and rough polishing on the ups and downslopes; The coarse polishing of the valley bottom uses a 200-mesh diamond flap wheel; the coarse polishing peaks and the coarse polishing uphill and downhill slopes both include diamond abrasive belts of 120 mesh, 200 mesh and 300 mesh used sequentially; The fine polishing includes sequentially using 400-mesh, 600-mesh, and 800-mesh wide diamond abrasive belts to polish the peaks and slopes.

2. The anti-corrosion and wear-resistant coating for a petroleum motor rotor prepared by the spraying method described in claim 1.

3. The anti-corrosion and wear-resistant coating for petroleum motor rotors according to claim 2, characterized in that, The corrosion-resistant and wear-resistant coating of the petroleum motor rotor has a thickness of 0.25-0.26 mm, a hardness of 1300HV0.3, a bonding strength of 75 MPa, a porosity of 0.3%, and a thickness uniformity of 0.02 mm.

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