Preparation method for high velocity oxy-fuel spraying of chromium carbide-nickel chromium coating on surface of soluble fracturing ball seat

Abstract

The invention discloses a preparation method of a high velocity oxy-fuel spraying chromium carbide-nickel chromium coating on the surface of a soluble fracturing ball seat, and belongs to the technical field of preparation of wear-resistant and corrosion-resistant coatings by a thermal spraying method. Comprising the following steps: (1) preparation before spraying: drying chromium carbide-nickel chromium powder for thermal spraying in a drying oven; (2) cleaning a substrate: wiping and cleaning a spraying area and an adjacent area of the soluble fracturing ball seat by adopting absolute ethyl alcohol or acetone; (3) sand blasting treatment is conducted, specifically, 30-50-mesh white corundum sand is adopted for conducting sand blasting treatment on the soluble magnesium alloy under the pressure of 0.4-0.6 MPa; (4) high velocity oxy-fuel spraying is conducted, specifically, the chromium carbide-nickel chromium coating is finally prepared through an intermittent and multiple spraying method. The prepared high velocity oxy-fuel chromium carbide-based coating has the characteristics of high hardness, low porosity, wear resistance, erosion resistance and the like, has certain corrosion resistance, can meet the normal service of the soluble fracturing ball seat during fracturing operation, and has certain application value.

Description

Technical Field

[0001] This invention belongs to the technical field of thermal spraying for preparing wear-resistant and corrosion-resistant coatings, and specifically relates to a method for preparing a chromium carbide-nickel-chromium coating by supersonic flame spraying on the surface of a soluble fracturing ball seat for segmented fracturing wells. Background Technology

[0002] In existing technologies, the packer-based ball-sleeve multi-stage fracturing technology in horizontal well staged fracturing is an important means of developing low-permeability oil and gas reservoirs. The ball-sleeve system is the key to this technology, mainly composed of fracturing balls, ball seats, and sliding sleeves. In traditional ball-sleeve systems, the ball seats are made of alloy steel or cast iron. After fracturing, the ball seats are eroded and enlarged by the sand-carrying fluid, leading to problems such as incomplete sealing and difficulty in opening the sand-spraying nozzle. Furthermore, a second well run is required after fracturing to retrieve or remove the ball seats to achieve full wellbore patency. This is not only complex and time-consuming but also carries the risk of blockage. In recent years, to avoid the retrieval and removal of traditional alloy steel ball seats, soluble fracturing ball seats have been proposed and developed. These self-degradable ball seats can achieve full wellbore patency without retrieval or removal, offering safety, reliability, and cost savings.

[0003] However, the service conditions of soluble fracturing balls in wells are extremely harsh. They not only need to withstand the enormous pressure (20~80 MPa) generated by pressure buildup, but also need to face the corrosion of groundwater / fracturing fluid and the erosion and wear of sand-containing fracturing fluid under high temperature (50~150℃) and high hydrostatic pressure. Therefore, soluble fracturing balls must undergo surface treatment to improve surface performance and ensure normal service of soluble fracturing balls during fracturing operations. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing a chromium carbide-nickel-chromium coating by supersonic flame spraying on the surface of a soluble fracturing ball seat. This method eliminates the need for pre-spraying a nickel-based adhesive layer on the part, and the prepared chromium carbide-nickel-chromium coating exhibits high hardness, low porosity, and a distinct layered cross-sectional morphology without longitudinal cracks or coating peeling. This ensures the normal service of the soluble ball seat during fracturing operations.

[0005] The technical solution adopted in this invention is as follows:

[0006] Preparation before spraying: Before spraying, place the thermal spraying chromium carbide-nickel-chromium powder in an oven at 80°C for at least 1-2 hours to increase the flowability of the chromium carbide-nickel-chromium powder during carrier gas transport; the composition of the chromium carbide-nickel-chromium powder is: 75wt% Cr3C2, 25wt% NiCr, and the powder particle size is: 15um~40um.

[0007] The spraying process includes the following steps: S1: Cleaning the substrate: Wipe and clean the spraying area and adjacent areas of the soluble fracturing ball seat with anhydrous ethanol or acetone to thoroughly remove oil and other debris from the surface of the soluble ball seat. After degreasing, dry with clean compressed air. S2: Sandblasting: Sandblasting is performed using an automatic sandblasting machine with an adjustable air pressure source of 0~0.6MPa and equipped with an oil-water separator. S3: Thermal spraying: Apply a chromium carbide-nickel-chromium coating using a supersonic flame within the specified area. 1) Remove the floating dust from the surface of the soluble fracturing ball seat with clean compressed air and fix it on a special fixture. 2) Spray the soluble fracturing ball seat according to the following thermal spraying parameters. 3) Equip the coating with a coating cooling device and use compressed air to cool the parts. 4) During the spraying process, use intermittent, multiple spraying methods. Immediately after each spraying, use compressed air to cool the coating. After the coating surface temperature drops to 50~100℃, observe the coating surface condition. After confirming that the coating has no cracks, peeling, or other phenomena, spray again. Keep the interval between each spraying within 5 minutes to keep the temperature of the parts uniform during the spraying process. parameter Setting value spray gun model Wokastar610s Oxygen flow rate 900L / min kerosene flow 25.3L / h Carrier gas type N2 Carrier gas flow rate 5L / min Powder delivery rate 74±5g Spraying distance 320~360 mm Spraying angle 70°~90° Component / sample temperature <150℃

[0008] Furthermore, the sandblasting process parameters in step S2 are shown in the table below: Sandblasting machine types Types of abrasives Abrasive grit size Sandblasting pressure Sandblasting distance Sandblasting angle Pressure type White corundum sand 30-50 mesh 0.4-0.6 MPa 100-150 mm 60~85°

[0009] Furthermore, in step S3, four thermal spraying and cooling operations are performed, and the prepared chromium carbide-nickel-chromium coating has a distinct layered structure.

[0010] After cleaning and spraying, remove the spraying protective clamps, clean the surface dust of the parts, and mark them.

[0011] The beneficial effects of this invention are:

[0012] (1) This invention has determined the process of supersonic flame spraying of chromium carbide-nickel chromium coating on the surface of soluble rare earth magnesium alloy through experimental demonstration.

[0013] (2) The process of preparing a corrosion-resistant and wear-resistant coating on the surface of a soluble fracturing ball seat does not require the pre-spraying of a nickel-based adhesive layer. This not only makes the operation convenient and the quality stable, but also reduces the production cost.

[0014] (3) Experiments have shown that the nickel-chromium-chromium carbide coating prepared on the surface of the soluble fracturing ball seat using this process meets the performance requirements of the parts in terms of hardness, bonding strength, porosity, and oxide content. The dissolution rates of the soluble magnesium alloy substrate and the thermally sprayed chromium carbide coating are shown in the table below: the dissolution rate of the substrate decreases significantly after thermal spraying of the chromium carbide coating; if the coating cracks during the dissolution process and the substrate and coating are exposed to the corrosive medium environment at the same time, the dissolution rate increases significantly due to galvanic corrosion; this can significantly reduce the time required for the complete dissolution of the workpiece.

[0015] Material Dissolution environment Dissolution time (h) Weight loss (g) Surface area (cm 2 ) dissolution rate (mg / cm 2 .h)]]> Soluble magnesium alloy 50℃, 0.84% ​​KCl 0.5h 0.35 28 25 Soluble magnesium alloy 50℃, 3% KCl 0.5h 0.49 28 35 Soluble magnesium alloy 70℃, 3% KCl 0.5h 0.422 20 42.2 Soluble magnesium alloy 90℃, 3% KCl 0.5h 1.31 28 93 HVOF-Cr3C2 50℃, 3% KCl 6 0.0173 1 2.883 HVOF-Cr3C2 70℃, 3% KCl 6 0.0454 0.9 8.407 HVOF-Cr3C2 (rupture) 80℃, 3% KCl 6 1.1616 1 193.6

[0016] Furthermore, the erosion rates of soluble magnesium alloys and thermally sprayed chromium carbide coatings are shown in the table below: Material erosion environment Erosion time (h) Erosion velocity (m / s) Weight loss (g) Surface area (cm 2 )]> Erosion rate (mg / cm 2 .h)]]> Soluble magnesium alloy Room temperature: 10 Wt% quartz sand 18000 mg / L of Cl - solution 3h 5 0.1052 1 350.66 HVOF-Cr3C2 Room temperature: 10 Wt% quartz sand 18000 mg / L of Cl - solution 3h 5 0.0007 1 2.33 HVOF-Cr3C2 Room temperature: 10 Wt% quartz sand 18000 mg / L of Cl - solution 6h 7.5 0.0714 1 11.9 HVOF-Cr3C2 Room temperature: 10 Wt% quartz sand 18000 mg / L of Cl - solution 6h 10 0.1405 1 23.41

[0017] (4) The coating prepared by the process of the present invention has a thickness of 180±5mm and a surface micro Vickers hardness of up to 900HV. 0.2 The coating exhibits no cracks, uniform pore distribution, and a porosity of less than 1%. Compared to the substrate, the coating demonstrates superior wear resistance; after dry abrasive wear testing, the wear rate decreased from 42.29 mm. 3 / Nm decreased to 1.45×10-3mm 3 / Nm.

[0018] (5) The electrochemical performance of the chromium carbide coating prepared by the process of the present invention is significantly improved compared with the substrate, that is, the impedance increases from 32 ohm to 22000 ohm, and the self-corrosion current decreases from 1.06×10-3 to 6.101×10-5 A / cm2. The improvement of electrochemical performance enables the soluble fracturing ball seat to serve normally during fracturing operations without dissolving prematurely. Attached Figure Description

[0019] Figure 1 Metallographic microstructure and surface SEM morphology of the cross-section of the supersonic flame-sprayed chromium carbide-nickel-chromium coating of this invention.

[0020] Figure 2 The EDS spectrum of the chromium carbide-nickel-chromium coating sprayed by supersonic flame according to the present invention.

[0021] Figure 3 Friction coefficient curve of chromium carbide-nickel-chromium coating and substrate for supersonic flame spraying in this invention.

[0022] Figure 4 X-ray diffraction pattern of the supersonic flame sprayed chromium carbide-nickel-chromium coating of this invention.

[0023] Figure 5The electrochemical performance diagram of the chromium carbide-nickel-chromium coating sprayed by supersonic flame according to the present invention is shown.

[0024] Figure 6 The surface SEM morphology of the supersonic flame-sprayed chromium carbide-nickel-chromium coating of the present invention under different erosion velocities is shown.

Claims

1. A method of producing a surface of a dissolvable frac ball seat with a high velocity oxy-fuel sprayed chromium carbide-nickel-chromium coating, characterized in that, It comprises the following steps: (1) Preparation before spraying: The chromium carbide-nickel chromium powder used for thermal spraying is put into an oven at 80℃ for 1h-2h to dry to increase the flowability of the powder during the gas delivery process (2) Cleaning the substrate: The spraying area and adjacent area of the soluble fracturing ball seat are wiped and cleaned with anhydrous ethanol or acetone to remove oil stains, dust and other impurities (3) Sand blasting treatment: The substrate of the soluble fracturing ball seat is treated by sand blasting with white corundum sand (4) High-velocity oxy-fuel spraying: The chromium carbide-nickel chromium coating is finally prepared on the surface of the treated substrate by intermittent and multiple spraying.

2. The method for preparing a soluble fracturing ball seat surface supersonic flame sprayed chromium carbide-nickel-chromium coating according to claim 1, characterized in that, The chromium carbide-nickel chromium powder composition in step (1) is 75wt% Cr3C2 and 25wt% NiCr, and the powder particle size is 15um-40um.

3. The method of claim 1, wherein the surface of the dissolvable ball seat is prepared by super sonic flame sprayed chromium carbide - nickel-chromium coating. The soluble fracturing ball seat in step (2) is a Mg-Cu-Ni-Re series soluble rare earth magnesium alloy. The Ni, Cu and RE elements in the alloy form a second phase (such as Mg2Ni, Mg2Cu, Mg12Nd, etc.) with the Mg matrix, and there is a significant potential difference between the second phase and the Mg matrix. This potential difference drives the micro-battery reaction and can accelerate the anodic dissolution of the magnesium matrix. After the fracturing operation is completed and the coating is broken, the soluble fracturing ball seat made of such alloy can spontaneously dissolve in the salt water downhole, eliminating the drilling and milling removal process, shortening the construction period, and reducing the fracturing operation cost during the period.

4. The method of producing a surface of a dissolvable frac ball according to claim 1, wherein, The sand blasting process parameters in step (3) include: abrasive particle size: 30-50 mesh; sand blasting pressure: 0.4MPa-0.6MPa; sand blasting distance: 100mm-150mm; sand blasting angle: 60°-85°.

5. The method of producing a surface of a dissolvable frac ball according to claim 1, wherein, During the spraying process, the intermittent and multiple spraying method is adopted, and after the single spraying is completed, the coating is air-cooled using compressed air. After the coating surface is cooled to 50-100℃, the coating surface state is observed, and the coating is sprayed again after confirming that there is no cracking, peeling and other phenomena. The thermal spraying process parameters include: oxygen flow: 900L / min; kerosene flow: 25.3 L / h; carrier gas type: N2; carrier gas flow: 5 L / min; powder feeding rate: 74±5g; spraying distance: 320-360mm; spraying angle: 70°-90°; part / sheet temperature: <150℃.

6. A method of producing a surface of a dissolvable frac ball according to claim 1, wherein a Ni-Cr-CrC coating is applied by supersonic flame spraying. The prepared coating has a thickness of 180±5mm, a surface micro Vickers hardness of more than 900HV0.2, no cracks, uniformly distributed pores, and a coating porosity of less than 1%. The coating has good wear resistance, erosion resistance and certain corrosion resistance.

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