CN109868440B

CN109868440B - Preparation method of anti-balling wear-resistant modified layer on surface of drill steel body

Info

Publication number: CN109868440B
Application number: CN201711197734.3A
Authority: CN
Inventors: 朱丽娜; 乔娟; 岳�文; 付志强; 康嘉杰; 王成彪
Original assignee: China University of Geosciences Beijing
Current assignee: Zhengzhou Research Institute of China University of Geosciences (Beijing); China University of Geosciences Beijing
Priority date: 2017-11-25
Filing date: 2017-11-25
Publication date: 2020-05-01
Anticipated expiration: 2037-11-25
Also published as: CN109868440A

Abstract

The invention discloses a preparation method of a mud-proof wear-resistant modified layer on the surface of a drill steel body, which comprises the following steps: (1) polishing and sand blasting pretreatment are carried out on the alloy steel; (2) spraying by adopting a supersonic flame spraying system; (3) grinding, polishing and cleaning the SiC sand paper; (4) preparing a texture by using a laser; (5) polishing, ultrasonic cleaning and drying, namely preparing the surface anti-balling wear-resistant modified layer on the surface of the alloy steel. The preparation method is simple and feasible. The prepared modified layer has the advantages of high hardness, low porosity and decarburization rate, excellent wear resistance and the like, and is suitable for strengthening the drill steel body so as to improve the wear resistance of the drill steel body. The laser surface texture technology has no pollution to the environment, is simple to manufacture, has controllable appearance, can improve the anti-balling performance of the coating surface, and is helpful to the improvement of the wear resistance. The obtained composite strengthening layer has improved mud bag resistance and frictional wear resistance.

Description

Preparation method of anti-balling wear-resistant modified layer on surface of drill steel body

Technical Field

The invention belongs to the technical field of drilling bits, and particularly relates to a preparation method of a mud-bag-preventing wear-resistant modified layer on the surface of a bit steel body.

Background

1.1 present and existing problems

With the rapid development of industrial economy, the global demand for oil and gas resources also sharply increases, but as the discovery amount of conventional oil and gas fields is reduced year by year and the exploitation difficulty is gradually increased, the development demand for unconventional oil and gas resources such as shale oil and gas, coal bed gas, natural gas hydrate and the like is increasingly urgent. The shale oil gas resource amount in China is quite rich, and the shale oil gas resource amount is an important field for future oil gas exploration and exploitation. However, shale has the particularity of large specific surface area, small pores, complex structure, easy water absorption and expansion, and the like, so that the shale poses severe requirements and great challenges for the performance of the drilling machine.

The performance of the drill bit as a main rock breaking tool in the exploration and development of petroleum and mineral products directly influences the drilling quality, the drilling speed and the drilling cost. Polycrystalline Diamond Compact (hereinafter referred to as "PDC bit") is the most widely used bit at present, and is a bit steel body machined from nickel, chromium and molybdenum alloys, and after heat treatment, a hole is drilled in the bit steel body, and the Polycrystalline Diamond Compact is pressed into or brazed into the bit steel body. The PDC drill bit has unique rock cutting and breaking modes and has the advantages of high drilling speed, high efficiency, long service life and the like, so that the PDC drill bit becomes a main drill bit for oil and gas drilling at present.

However, when the PDC drill bit is used for drilling in shale, a "balling" phenomenon is easily generated, that is, when the argillaceous debris cut in the drilling process meets water, the argillaceous debris cannot be timely discharged from the bottom of the hole and adheres to the drill bit, so that the balling of the drill bit is formed. The PDC drill bit is an integral drill bit, and the whole drill bit has no movable parts, so that mud pockets are easier to generate than common roller cone drill bits. Once the PDC drill bit generates mud bags, the mechanical drilling speed is greatly reduced by a light person, and the drilling efficiency is influenced; when the heavy person stops drilling, the heavy person is forced to pull out the drill bit to clean the drill bit; even more serious accidents in the hole, such as sticking, endanger the safety of the equipment and cause great economic loss. In addition, if the oil and gas are buried deeply, the phenomenon of mud entrapment is in an aggravating trend along with the increase of the drilling depth, so that the drill bit slips seriously when the drilling depth is large, and the drill cannot drill effectively or even abandons the drilling result. Therefore, the phenomenon of 'balling' seriously restricts the wider application of the PDC drill bit in the field of drilling of special strata such as shale oil-gas layers and the like, so that the problem of 'balling' of the PDC drill bit is solved, and the PDC drill bit has important significance for improving the drilling efficiency, shortening the drilling period and reducing the drilling cost.

The PDC bit balling is caused by a plurality of factors, which mainly comprise geological factors in the aspects of geological characteristics of the stratum and the like, structural design factors of the bit, component performance factors of drilling fluid and the like. (1) Geological factors: the shale is easy to hydrate and disperse, so that the solid phase content such as mud in a well is obviously increased, and the shale is adsorbed on the surface of a drill bit to cause a drill bit mud pack. (2) Structural factors of the drill bit: the hydraulic structure of the drill bit is unreasonable in design, so that the bottom hole cleaning effect and the smooth discharge of rock debris are directly influenced; the unreasonable design of the drill flow channel can not ensure that the drill cuttings are smoothly separated from the well bottom. (3) Drilling fluid factors: the drilling fluid has weak inhibitive performance, so that the hydration expansion of the shale in the stratum can not be effectively inhibited; the poor lubricating property of the drilling fluid can not form an effective protective film on the surface of the drill bit, so that the poor solid phase in the drilling fluid is easy to be adsorbed on the drill bit. Therefore, in addition to geological factors, other factors can be avoided in the inducement of the PDC bit balling phenomenon.

In view of the above-mentioned factors that cause the bit balling problem, researchers in this field have conducted targeted research around the following scientific questions: (1) increasing the velocity of fluid flowing through the PDC bit cutters based on computational fluid dynamics; (2) the wettability of the drilling fluid on rock debris is improved through physical and chemical actions; (3) the mechanical adhesion and chemical adhesion of the rock debris on the surface of the drill bit are eliminated based on a coating technology.

Through comprehensive analysis on the research results, the following results are found: if the coating with excellent hydrophobicity and wear resistance can be prepared, the problems of balling and service durability of the PDC drill bit are expected to be solved. At present, a WC-CoCr metal ceramic coating prepared by a supersonic flame spraying technology (HVOF) has excellent wear resistance, corrosion resistance and good bonding strength, is already mature to be applied to surface strengthening of drilling machine parts such as drill rods, sleeves and the like, and is also suitable for strengthening a drill steel body. However, how to improve the hydrophobic property of the WC-CoCr coating to achieve the purposes of wear resistance and mud pack prevention becomes a problem to be solved urgently.

1.2 purpose and significance of the study

Supersonic flame spraying (HVOF) was developed by Browing corporation in the last 80 th century. Compared with the traditional flame spraying method, the supersonic flame spraying method improves the heating temperature and the spraying speed of the spraying material, the particle spraying speed can reach more than 500m/s, and the supersonic flame spraying technology is obtained. The supersonic flame spraying has high productivity, and the prepared coating has excellent performance, and is the main method for preparing the metal ceramic coating and the metal coating at present. The WC-CoCr coating prepared by the supersonic flame spraying technology has the advantages of high hardness, low porosity and decarburization rate, excellent wear resistance and the like, and a passive film is generated on the surface of a material by Cr element in a corrosive environment to reduce the corrosion rate. Therefore, the WC-CoCr cermet coating prepared by the supersonic flame spraying technology (HVOF) is already mature to be applied to surface strengthening of drilling machine parts such as drill rods, sleeves and the like, and is also suitable for strengthening of drill steel bodies. But the anti-mud property of the coating needs to be improved.

The surface texture technology can obviously improve the hydrophobicity and the frictional wear performance of the surface of the material. The surface texture technology is to change the surface property by processing a series of regular micro-structures such as pits, bulges, grooves and the like on the surface of a material. The key for improving the surface hydrophobic property is to change the physical structure of the solid surface by increasing the microstructure roughness of the solid surface and constructing a proper surface micro-morphology. Namely, the water drops are pressed on the texture surface to form a layer of air cushion between the surface of the film and the water drops, and the water drops are supported to finally reach a super-hydrophobic Cassie-Baxter state. In the aspects of antifriction and wear resistance, the texture can play the roles of accommodating abrasive dust, storing lubricant and improving dynamic pressure bearing, and the texture under certain conditions can improve the wear resistance. In addition, the laser surface texture technology has no pollution to the environment, simple manufacture, short time consumption, low cost, wide processing range and controllable size and shape.

Therefore, in the invention, the WC-CoCr cermet coating is prepared by supersonic flame spraying, then specific texture parameters are prepared on the coating by using laser equipment, and two surface modification technologies are effectively combined, so that the mud pocket prevention and wear resistance of the surface of the drill steel body can be simply and effectively improved.

Disclosure of Invention

In order to overcome the defects in the background art, the invention provides a preparation method of a mud-proof wear-resistant modified layer on the surface of a drill steel body, the preparation method is simple and easy to implement, low in cost and free of pollution, and the mud-proof performance and the friction and wear performance of the obtained composite modified strengthening layer are improved.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a preparation method of a mud-proof wear-resistant modified layer on the surface of a drill steel body comprises the following steps:

(1) selecting alloy steel as a substrate, and then polishing and sandblasting the alloy steel;

(2) spraying the sample subjected to sand blasting by adopting a supersonic flame spraying system;

(3) grinding the sprayed sample by SiC abrasive paper, finally polishing, and then sequentially cleaning in alcohol and acetone;

(4) placing the cleaned sample on a sample table of a laser, drawing a texture map in software, and starting the laser to prepare a texture to obtain a supersonic flame spraying/surface texture composite processed sample;

(5) and polishing the sample subjected to the supersonic flame spraying/surface texture composite treatment again to remove the fused oxide on the surface after the laser processing, then carrying out ultrasonic cleaning and drying to prepare the surface anti-balling wear-resistant modified layer on the surface of the alloy steel.

Preferably, in the step (1), the surface roughness of the alloy steel is polished to Ra of 0.65 μm; the sand material is brown corundum, the diameter of the sand material is 700 mu m, the sand blasting distance is 0.15m, the sand blasting pressure is 7MPa, and the sand blasting angle is 45 degrees.

Preferably, in the step (2), the alloy steel is fixed on a fixture in the spraying process, the fixture rotates and moves back and forth at a constant speed, and the process parameters of the supersonic flame spraying system are as follows: the kerosene flow is 26L/h, the oxygen flow is 900L/min, the spraying distance is 420mm, the powder feeding rate is 80-150g/min, and the carrier gas flow is 7L/min. After the parameters are adopted to carry out supersonic flame spraying, a spraying layer with the thickness of 200 mu m is generated on the surface of the matrix, and the prepared WC-CoCr coating has the characteristics of high hardness, low porosity and low decarburization rate. Compared with other parameters, the optimized process parameters used by the applicant greatly reduce the occurrence of oxidation reaction in the spraying process, and obviously improve the anti-friction performance of the surface of the matrix.

Preferably, in the step (3), the sprayed sample is ground sequentially through SiC sandpaper 600#, 800#, 1000#, 1200#, 1500# and 2000#, and polished until the surface roughness is 0.06-0.08 μm, and the time for cleaning in alcohol and acetone is 15 min.

Preferably, in step (4), the processing parameters set by the laser are as follows: a wavelength of 1060nm, a frequency of 20kHz, a speed of 500mm/s, a voltage of 220V, a current of 10A and a frequency of 10W. By processing the parameters, regularly arranged pit-type textures with proper depth can be prepared on the surface of the coating, and the surface textures can effectively capture abrasive dust in the friction process and reduce the friction coefficient.

Preferably, in the step (4), the parameters of the laser surface texture are as follows: three textures of pits, grooves and grids with the width of 150 μm and the spacing of 100 μm, 150 μm and 300 μm. Through the processing of the parameters, the texture with proper parameters can increase the contact angle, lighten the mud pocket, capture abrasive dust and reduce the adverse effect caused by abrasive wear.

The invention has the advantages that:

(1) the preparation method is simple, environment-friendly, controllable in appearance, low in price and strong in applicability;

(2) the invention firstly carries out supersonic flame spraying on the surface of 35CrMo alloy steel to form a 200 mu m-thick WC-CoCr cermet coating which has the advantages of high hardness, low porosity and decarburization rate, excellent wear resistance and the like. The coating can obviously improve the wear resistance of the surface of the substrate. Meanwhile, the problem of mud bags is solved by carrying out laser surface texture treatment on the basis of the coating. The texture with different parameters can contain abrasive dust, store slurry, improve dynamic pressure bearing, and improve the problems of high friction coefficient and serious abrasion of the coating in the friction process;

(3) the invention combines the supersonic flame spraying technology and the laser surface texture technology, is applied to the 35CrMo alloy steel used as the drill steel body, solves the problem that the drill needs higher wear resistance under the working condition, increases the contact angle of the coating surface through the surface texture, and provides a feasible scheme for solving the problems of mud pocket prevention and high-requirement wear resistance of the drill.

Drawings

FIG. 1 is a schematic illustration of the contact angle of the surface of the original coating with deionized water and drilling fluid; wherein (a) is a schematic diagram of the contact angle of the surface of the original coating with deionized water, and (b) is a schematic diagram of the contact angle of the surface of the original coating with drilling fluid;

FIG. 2 is a graph of texture coverage versus contact angle;

FIG. 3 is a graph of contact angles of drops of distilled water and mud filtrate on a pitted textured surface at different spacings; wherein (a), (b) and (c) are respectively contact angles of distilled water drops on the pit texture surface with the spacing of 100 mu m, 150 mu m and 300 mu m; (d) the contact angles of the mud filtrate drops on the pit texture surface with the spacing of 100 mu m, 150 mu m and 300 mu m are respectively shown in (e) and (f);

FIG. 4 is a graph of contact angles of distilled water and mud filtrate droplets on textured surfaces of grooves at different spacings; wherein (a), (b) and (c) are respectively contact angles of distilled water drops on the groove texture surface with the spacing of 100 mu m, 150 mu m and 300 mu m; (d) the contact angles of the mud filtrate drops on the groove texture surface with the spacing of 100 mu m, 150 mu m and 300 mu m are respectively shown in (e) and (f);

FIG. 5 is a graph of contact angles of distilled water and mud filtrate droplets on a grid textured surface at different spacings; wherein (a), (b) and (c) are respectively contact angles of distilled water drops on the grid texture surface with the spacing of 100 mu m, 150 mu m and 300 mu m; (d) the contact angles of the mud filtrate drops on the grid texture surface with the spacing of 100 mu m, 150 mu m and 300 mu m are respectively shown in (e) and (f);

FIG. 6 is a graph of dry friction and mud lubrication of the original coating;

FIG. 7 is a graph of friction coefficient versus time obtained from a dry friction test of surface texture of all parameters; wherein (a) is the dry friction coefficient of the pit texture, (b) is the dry friction coefficient of the groove texture, and (c) is the dry friction coefficient of the grid texture;

FIG. 8 is a graph of friction coefficient versus texture for different parameters for a slurry lubrication friction test under the same conditions; wherein (a) is the mud friction coefficient of a pit texture, (b) is the mud friction coefficient of a groove texture, and (c) is the mud friction coefficient of a grid texture;

FIG. 9 is a graph of texture coverage versus wear volume; wherein (a) is dry friction and (b) mud lubrication.

Detailed Description

The invention will be further described with reference to the accompanying drawings in which:

preparation of a sample:

In the step (1), the surface roughness of the alloy steel is polished to Ra of 0.65 μm; the sand material is brown corundum, the diameter of the sand material is 700 mu m, the sand blasting distance is 0.15m, the sand blasting pressure is 7MPa, and the sand blasting angle is 45 degrees.

In the step (2), in the spraying process, the alloy steel is fixed on a clamp, the clamp rotates and moves back and forth at a constant speed, and meanwhile, the technological parameters of the supersonic flame spraying system are as follows: the kerosene flow is 26L/h, the oxygen flow is 900L/min, the spraying distance is 420mm, the powder feeding rate is 80-150g/min, and the carrier gas flow is 7L/min.

In the step (3), the sprayed sample is ground sequentially through SiC sandpaper 600#, 800#, 1000#, 1200#, 1500# and 2000#, and polished until the surface roughness is 0.06-0.08 μm, and the time for cleaning in alcohol and acetone is 15 min.

In the step (4), the processing parameters set by the laser are as follows: the wavelength is 1060nm, the frequency is 20kHz, the speed is 500mm/s, the voltage is 220V, the current is 10A, the frequency is 10W, and the parameters of the laser surface texture are as follows: three textures of pits, grooves and grids with the width of 150 μm and the spacing of 100 μm, 150 μm and 300 μm.

Characterization and analysis of the samples:

as can be seen from fig. 1, the contact angles of the original coating surface which is not textured and is only polished with deionized water and drilling fluid are 81.5 ° and 69 °, respectively, and as can be seen from fig. 1 and 2, after the texturing, the contact angles are increased by 67.5% and 62.6% at most, and the hydrophobic property is greatly improved;

as can be seen from fig. 2, when compared in the lateral direction, the same texture shape shows a decrease in the texture coverage and a decrease in the contact angle with an increase in the pitch. When compared longitudinally, the same pitch is found and the contact angle is sequentially increased by the pits, grooves and grids, because the area of the texturing increases at the same width.

As can be seen from fig. 3, 4 and 5, the contact angle of deionized water is significantly larger than that of drilling fluid of the same parameters. The contact angle of the deionized water or the drilling fluid and the surface of the texture coating shows a similar rule, namely the larger the distance is, the larger the contact angle is, and the higher the hydrophobic property is, namely the contact angle is in direct proportion to the texture coverage rate R.

FIG. 6 is a plot of the coefficient of friction of the original coating at a load of 10N, and it can be seen that the dry coefficient of friction is about 0.65 and the mud lubrication coefficient of friction is about 0.05.

FIG. 7 is a graph of coefficient of friction versus time for dry friction experiments on surface textures of all parameters. From the experimental results, the friction coefficients of all the parameter textures show the same variation trend. After a running-in period of about 5-10 minutes after loading, the coefficient of friction gradually levels off. The stable friction coefficient of the surface textures of three different shapes basically shows a trend of increasing with the increasing of the texture pitch. At the same interval, the friction coefficients are grids, grooves and pits from small to large. The untreated original coating had a coefficient of friction of about 0.6, the coefficient of friction of the grid texture with a pitch of 150 μm, a pitch of 100 μm and a pitch of 100 μm was lower than that of the original coating, and the coefficient of friction of the grid texture with a D of 100 μm was about 0.47. The reason is that the texture processing area is large under the parameter, the capacity of containing abrasive dust is strong, and the friction resistance is reduced.

FIG. 8 is a graph of friction coefficient versus texture for different parameters when a mud lubrication friction test was performed under the same conditions. Under the condition of slurry lubrication, the texture can form local hydrodynamic lubrication, and a lubricating film is generated on the surface, so the friction coefficient is obviously smaller than that of dry friction. The trend of the lattice texture was observed to be most similar to that of the original coating, with a pit coefficient of friction of about 0.08 at a spacing of 300 μm. This is due to the smallest textured area, the surface condition closest to the original surface, and the smaller textured area not serving to contain the abrasive dust storage slurry. In addition, the friction coefficient of the grooves and the grids is relatively large, but under the same condition, the friction coefficient of the grids is smaller than that of the grooves. Taken together, the coefficients of friction for all three textures increase with increasing pitch and are substantially greater than the original surface under the slurry lubrication condition. This is due to the increased roughness of the surface texture and the presence of particulate matter in the slurry during lubrication of the slurry, which results in a textured surface having a higher coefficient of friction than the original surface. The grid texture achieves a better balance between roughness and texture function than the grooves.

Because the shape of the processed texture is regular, the texture coverage rate R of different parameters can be calculated. According to the order of decreasing pitch, the texture coverage is, in order, pit: 0.086, 0.1928, 0.2831; groove: 0.3305, 0.4955, 0.6005; grid: 0.5605, 0.7505, 0.8405. The texture coverage versus wear volume for the three textures can be plotted in fig. 9. Fig. 9(a) is the wear volume on dry rubbing, which shows that for three different surface textures, the pit wear volume increases with decreasing texture coverage, and the grooves and cells are reversed. The wear volume of the pits and grooves is slightly larger than the original coating surface, and the grid has larger wear volume because the grinding trace is deepest. Fig. 9(b) shows that when the slurry is wetted, the abrasion volume of the original coating and the pits and grooves is obviously larger than that of dry friction, and the grid is reduced and still increases with the reduction of the texture coverage. The ability of the mesh to store mud and swarf and to generate a dynamic pressure bearing effect is stronger than the pits and grooves under mud lubrication conditions.

Finally, it should be noted that: it should be understood that the above examples are only for clearly illustrating the present invention and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the scope of the invention.

Claims

1. A preparation method of a mud-proof wear-resistant modified layer on the surface of a drill steel body is characterized by comprising the following steps:

(5) polishing the sample subjected to the supersonic flame spraying/surface texture composite treatment again to remove the fused oxide on the surface after the laser processing, then performing ultrasonic cleaning and drying to prepare a surface anti-balling wear-resistant modified layer on the surface of the alloy steel;

wherein the content of the first and second substances,

in the step (1), the surface roughness of the alloy steel is polished to Ra of 0.65 μm; brown corundum is selected as the sand material, the diameter of the sand material is 700 mu m, the sand blasting distance is 0.15m, the sand blasting pressure is 7MPa, and the sand blasting angle is 45 degrees;

in the step (2), in the spraying process, the alloy steel is fixed on a clamp, the clamp rotates and moves back and forth at a constant speed, and meanwhile, the technological parameters of the supersonic flame spraying system are as follows: the kerosene flow is 26L/h, the oxygen flow is 900L/min, the spraying distance is 420mm, the powder feeding rate is 80-150g/min, and the carrier gas flow is 7L/min;

in the step (3), the sprayed sample is ground sequentially through SiC sand paper 600#, 800#, 1000#, 1200#, 1500# and 2000#, and is polished until the surface roughness is 0.06-0.08 mu m, and the time for cleaning in alcohol and acetone is 15 min;

in the step (4), the processing parameters set by the laser are as follows: the wavelength is 1060nm, the frequency is 20kHz, the speed is 500mm/s, the voltage is 220V, the current is 10A, and the frequency is 10W;

the parameters of the laser surface texture are as follows: three textures of pits, grooves and grids with the width of 150 μm and the spacing of 100 μm, 150 μm and 300 μm.