But in the process of oil gathering, there are more than 500 drilling tool failure accidents every year in China, which cause serious economic losses and cost tens of millions of dollars of imported downhole drilling tools of various specifications.
It is not enough for petroleum machinery and equipment to meet the requirements of high resistance (resistance to adverse working conditions), high strength, high wear resistance, excellent self-lubricating property, corrosion resistance and erosion resistance only by optimizing materials. It is also necessary to match the surface treatment process of materials to improve the comprehensive performance of materials.
Laser surface treatment technology plays an important role because of its technical advantages.
Figure 1 oil gathering site
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What is laser surface treatment technology?
Laser surface treatment technology is a kind of thermal processing method, which uses the high energy of laser to treat the workpiece.
The laser beam irradiates the surface of the workpiece to heat the material losslessly. The high temperature makes it melt, evaporate, vaporize and splash. Then the laser beam is cut off or moved away, and the surface of the workpiece condenses rapidly to achieve the purpose of surface modification. The laser has the characteristics of high energy and high density, the power density can reach 108 ~ 1010w / cm2, and the temperature can reach more than 10000 ℃. It can realize non-contact processing and is very suitable for material surface treatment.
Laser surface treatment technology has the following characteristics
1) The laser beam is easy to transmit and guide, and can deal with the surface and interior of part or complex part;
2) The energy is concentrated, the processing time is short, the heat affected zone is small, and the workpiece deformation is small;
3) It is easy to cooperate with CNC system to realize automatic control and high labor productivity;
4) Low processing cost, energy saving and no environmental pollution;
5) Generally, it can only deal with some sheet metal, not suitable for thick sheet metal;
6) The harm of laser to human eyes may affect the safety of workers, so efforts should be made to develop safety facilities.
It can improve the mechanical properties, metallurgical properties and physical properties of the material surface, so as to improve the wear resistance, corrosion resistance and fatigue resistance of parts and workpieces. It can be roughly divided into laser quenching, laser cladding, laser alloying, laser shock hardening and laser amorphization.
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Different laser surface treatment technology and Application
Laser surface treatment technology is mainly used in remanufacturing rotor bearing position of generator, blade and rotor of steam turbine, disc of flue gas turbine, laser anti-corrosion cladding of various corrosive pump body surface, laser strengthening of oil transportation pipeline, laser anti-corrosion and wear-resistant cladding of drilling screw, centralizer, stabilizer and other parts of oil production platform .
Many domestic companies, research institutes and universities are committed to the research of laser surface treatment, such as Wuhan Huagong Laser Engineering Co., Ltd., Changchun Institute of optics, precision mechanics and physics, Chinese Academy of Sciences, Semiconductor Research Institute, Chinese Academy of Sciences, Tsinghua University, etc. All solid state light source Laboratory of Institute of semiconductors, Chinese Academy of Sciences is dedicated to the research of laser cleaning and laser cladding. Zhong minlin, the project leader of Tsinghua University, devoted himself to the research of laser surface treatment technologies, such as laser alloying, laser cladding, laser micro nano processing, etc., and is at the leading level at home and abroad.
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Laser quenching
Compared with conventional surface quenching, laser quenching has the advantages of extremely fast heating speed, fast cooling speed, no need of cooling medium, high surface roughness, high surface hardness and no need of tempering.
Compared with the conventional quenching, the hardness of laser quenching is increased by 15% ~ 20%, and the wear resistance is increased by 2 ~ 4 times. At the same time, the corrosion resistance of hardened layer is also greatly improved. The comprehensive mechanical properties of workpieces are good, and even the ordinary materials can reach the strength and hardness of high-quality materials.
However, the application of laser surface hardening technology is limited, and it is suitable for the parts with shallow hardened layer. Therefore, the laser surface hardening process is usually applied to the workpiece which does not need overall hardening, has high precision requirements, or is difficult to be treated by other quenching methods, and has complex shape and needs to further improve the hardness and wear resistance. It is more suitable for the surface treatment of gears, crankshafts, cylinders, integral pump barrel and other slender pipes. Laser quenching has been applied to the surface modification of cylinder liner, integral pump barrel, tubing thread and drill pipe joint thread of combination pump, which effectively improves the wear resistance, prolongs the service life and replacement cycle of parts.
After decades of development, domestic laser quenching has made great progress in R & D and application. However, there is still a big gap compared with the international leading level, but it has great advantages compared with the traditional quenching method, so it is more and more valued. As the most commonly used processing method of laser surface treatment technology for petroleum machinery, laser quenching is still a research hotspot at present. The research on laser quenching of various metal materials has never stopped, such as 20CrMnTi gear steel, 35CrMoA, 42CrMo, 45 steel and so on.
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Laser cladding
Fig. 2 Laser Cladding
By adding cladding materials on the surface of the substrate, laser cladding uses high energy density laser beam to rapidly melt the alloy with different composition and properties and form an alloy layer with completely different composition and properties on the surface of the substrate. The specific process diagram is shown in the figure below.
Fig. 3 Schematic diagram of laser cladding
Cladding materials are mainly divided into metal powder, ceramic powder and composite powder. Compared with other coating technologies, laser cladding layer has the following characteristics because of its good bonding strength and high hardness
The cooling speed is fast;
The results show that the heat input and distortion are small, the dilution ratio of the coating is low (generally less than 5%), and the coating is metallurgically bonded with the substrate;
It can carry out selective cladding with low material consumption and excellent performance price ratio;
Laser beam aiming can make the inaccessible area cladding, green and pollution-free.
As an efficient additive manufacturing process, laser cladding is often used for surface strengthening and repairing of high value-added parts such as oil pipeline valve, plunger of water injection pump, polished sucker rod and valve seat of fracturing pump.
In terms of research, Sun Quan from the equipment maintenance department of Liaoyang Petrochemical Company of PetroChina studied the repair of the shell and the male and female rotors of the flare gas screw compressor in the refinery by laser cladding technology. The multi-layer cladding process was adopted, and the large-area cladding was successful. After the repair, the equipment function recovered well, and the compression basically met the production process requirements.
Zhang Zailiang of China Petroleum Engineering and Construction Corporation used 20CrMo steel, which is commonly used in polished rod of pumping unit, as matrix material, and selected Co based, Ni based and Fe based alloy powder as cladding material. The results show that the hardness of the specimen is significantly higher than that of the matrix, and its wear resistance is improved. Cheng Hao et al. Studied the laser cladding repair technology of water injection pump plunger used in the oilfield, selected nickel based powder as the coating material, compared the coating hardness under different laser parameters, which can prolong the service life of water injection pump plunger by 50% and reduce the cost by more than 38%.
Xiao Zhen of Xi'an Petroleum University takes the deformation fault of steam turbine cylinder joint surface in Puguang natural gas purification plant as the research object. The laser cladding technology is used to repair the deformation position of the cylinder on site. The penetration detection and ultrasonic detection of the cladding layer show that the cladding layer is in good condition without defects. After the cylinder is reassembled, the air leakage phenomenon of the cylinder is eliminated.
Sun Jianbo of China University of Petroleum (East China) and others have laser cladding a layer of wear-resistant iron-based alloy coating on the surface of oil drill pipe joint, which has the advantages of good molding, dense structure, uniform parts and no cracks, and the thickness of laser cladding wear-resistant and corrosion-resistant iron-based alloy coating can be accurately controlled within 0.3 ~ 1.5 Mm, which solves the problem of drill pipe joint failure too fast, and the automation of the manufacturing and processing process of drill pipe joint is easy to realize.
Laser cladding has not been fully industrialized in the surface treatment of petroleum machinery. The main reason is that the quality of cladding layer is unstable and the coating is easy to crack. There is no good solution for the problem. There is no unified standard for the selection of binder and preset film. It is difficult to control the microhardness of material surface in large area cladding. Many key technologies need to be further explored, and many researchers are also committed to solving these problems.
Yu Chengxue of Shandong Jianzhu University studied the formation mechanism of laser cladding cracks, and expounded the influencing factors and control methods of cracks. The CaF2 / Ni60 composite coating was prepared on Q235A steel by Zhang Jinchao, Zhejiang Key Laboratory of laser processing robot. In view of the incomparable advantages of laser cladding technology compared with traditional coating technology, it will play a great role in the surface treatment of petroleum machinery and equipment in the future.
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Laser alloying
Fig. 4 laser alloying
Laser alloying is to use high-energy laser beam to melt the surface of the base metal and add alloying elements to form a high concentration and uniform alloy layer on the basis of matrix as solvent and alloying elements as solute. The surface alloy layer with wear resistance, corrosion resistance, high temperature resistance and oxidation resistance can be prepared on the surface of some cheap matrix materials with poor surface properties, so as to replace the expensive whole alloy, save precious metal materials and strategic materials, and greatly reduce the production cost.
Compared with conventional heat treatment, laser alloying has many advantages, such as low dilution ratio of coating, hard to peel off alloying layer, wide use of powder and matrix materials, less melting of matrix, less deformation of workpiece, clean and pollution-free, easy to realize automation, etc.
Compared with laser cladding, the alloying elements of laser alloying are completely dissolved in the surface layer, and the obtained thin layer is uniform in composition and insensitive to cracking and spalling. It is suitable for manufacturing heavy-duty transmission parts with high hardness and high wear resistance, such as shafts, connecting rods, bolts, screws, sleeves, inlet valves and important gears. In petroleum machinery and equipment, laser alloying is mainly used for surface treatment of oil pipe, screw and turbine blade.
Although laser alloying has been widely concerned and studied in the surface treatment of petroleum machinery and equipment, its technology and theoretical research are not yet mature, and there are still many problems in practical application, such as cracks, uneven surface and holes in the alloying layer, and the laser treatment equipment has not reached the level of large-scale industrial application. Because of the advantages of surface treatment, the research of laser alloying is still a hot spot.
With the exploration of treatment technology and material strengthening theory, it is believed that the laser surface alloying technology will soon transit from theoretical research to practical application, and play a great role in practice.
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Other laser surface treatment technologies
Since the advent of laser, more than 20 laser surface treatment technologies have been formed. In addition to the above three, there are laser shock strengthening, laser cleaning, laser amorphization, laser glazing, laser marking, laser texturing, laser deformation and so on. Although they are also applied in the surface treatment of petroleum machinery and equipment, they are relatively few.
Laser shock strengthening is a new surface modification technology which uses laser-induced plasma shock wave to improve the fatigue life of materials. It has the advantages of remarkable strengthening effect, strong controllability and good adaptability. It plays an important role in improving the structural reliability and fatigue strength of components and prolonging the service life of materials. The schematic diagram is shown in the figure below.
Fig. 5 Schematic diagram of laser shock
At present, it is widely used in aerospace and military industry, and has a huge potential application market in petrochemical industry. The fatigue strength of X80 pipeline steel welded joint was increased by 11.2% after laser shock treatment by Kong Dejun.
Laser cleaning is a new green cleaning technology based on the interaction between laser and material. Compared with traditional cleaning methods such as mechanical friction cleaning, chemical corrosion cleaning, liquid solid strong impact cleaning and high frequency ultrasonic cleaning, laser cleaning has the advantages of less damage to the substrate, good quality, high efficiency, clean and pollution-free. It can be applied to oil drill pipe, pipeline, storage tank and screw Derusting, deoxidizing, degreasing, paint removing and pre welding treatment of rod surface.
Laser marking is a kind of surface treatment method, in which the workpiece to be processed is locally irradiated by the focused laser beam with high power density to leave permanent marks on the surface material to be processed.
Dai Wei used the fiber laser marking machine to process the dry gas seal ring with arbitrary groove number, arbitrary groove shape, outer diameter of 40 ~ 300 mm, groove depth of 0.002 ~ 0.01 mm and accuracy of ± 0.002 mm. Chang Qiuying et al. Used lm-ylp-20f - Ⅱ laser marking machine to process round micro pit array with regular arrangement on the surface of 45 ° steel specimen, which can improve the wear performance of dry friction under certain conditions.
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Summary
Laser surface treatment technology is suitable for manufacturing high-end petroleum equipment because of its high precision, small deformation, clean and pollution-free
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In order to meet the needs of processing larger and more complex workpieces, new lasers are developed to increase laser power, and auxiliary equipment such as beam forming and guidance system are developed.
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Strengthen the theoretical research on the modification mechanism of laser surface treatment technology, and make in-depth research on the mechanism of residual tensile stress and cracks in theory, and put forward specific solutions.
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Combined with computer simulation technology, the research on the influence of laser surface treatment process parameters, material properties and surface conditions on the surface layer properties after treatment is strengthened, and the optimal combination of process parameters is explored to develop the forming process.
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Strengthen the composite technology of laser and new materials and new processes, such as laser cladding / micro arc oxidation, laser quenching / ion implantation and other composite surface treatment technologies, laser surface nano technology, laser 3D printing, laser electroplating and other new processes, laser cladding amorphous coating, high entropy coating and other new material composite treatment technologies. The composite technology can integrate the advantages of various treatment technologies, and the treatment effect is far higher than that of the simple laser surface treatment technology.
Compared with other surface treatment technologies, laser surface treatment technology still has great development potential because of its great advantages. In the surface treatment of petroleum machinery and equipment, laser surface treatment technology still has broad application and development prospects.
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With the further deepening of the reform of the management system, each oilfield pursues both the oil and gas production and the overall economic benefits, and requires to reduce the production cost and improve the production efficiency. The characteristics of laser surface treatment technology determine that this technology is one of the most effective ways to reduce the cost of oil production machinery and equipment.
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With the deterioration of oil and gas production conditions in various oilfields, the number of high temperature and high pressure, deep wells and ultra deep wells is gradually increasing, which puts forward higher requirements for the material properties of petroleum machinery and equipment. The application scope of laser surface treatment technology in petroleum machinery is expanding.
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The core of made in China 2025 is intelligent manufacturing. One of the cores of intelligent manufacturing is optoelectronic technology, and one of the cores of optoelectronic technology is laser technology. Although the market scale of laser industry itself is small, it is one of the core forces driving the development of manufacturing industry. Its importance is self-evident. Laser surface treatment technology is bound to develop according to the situation and become an indispensable backbone in the surface treatment technology of petroleum machinery.
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