High temperature resistant anti-fouling coating for a gas turbine vane and method of spraying the same

Abstract

The application discloses a spraying method of a high-temperature-resistant anti-fouling coating for a flue gas turbine blade, adopts a full-automatic supersonic flame spraying device to spray a tungsten carbide-chromium carbide mixed coating on the surface of the flue gas turbine blade, then carries out laser cladding treatment on the tungsten carbide-chromium carbide mixed coating obtained through the supersonic flame spraying, and carries out polishing treatment on the tungsten carbide-chromium carbide mixed coating obtained through the laser cladding treatment, the obtained high-temperature-resistant anti-fouling coating is the tungsten carbide-chromium carbide mixed coating, can have higher hardness to meet the erosion resistance requirement, can have high-temperature-resistant performance, has high hardness, is suitable for the use of the flue gas turbine blade under high temperature, and can reduce the fouling of catalyst particles on the surface of the flue gas turbine blade.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flue gas turbine blade coating, in particular to a high-temperature-resistant and anti-fouling coating for flue gas turbine blades and a spraying method thereof. BACKGROUND

[0002] Energy recovery is an important part of the catalytic cracking unit, and the flue gas turbine is one of the most important equipment for energy recovery. However, the working environment of the flue gas turbine is harsh, the temperature of the flue gas reaches 620℃, and the cyclone separator cannot completely separate the catalyst particles, resulting in a small amount of catalyst particles still contained in the flue gas. The flue gas turbine blade will be eroded by the catalyst particles with large particle size, and the catalyst particles with small particle size will be deposited on the flue gas turbine blade to cause fouling, which will increase the energy consumption of the flue gas turbine, reduce the efficiency, and significantly reduce the service life of the flue gas turbine. In severe cases, it will change the balance of the rotor and affect the normal operation of the flue gas turbine. Therefore, the flue gas turbine blade needs to have the properties of high-temperature resistance, erosion resistance and anti-fouling.

[0003] To improve the high-temperature resistance, erosion resistance and anti-fouling properties of the flue gas turbine blade and prolong its service life, in addition to improving the separation effect of the previous unit cyclone separator, protective measures such as coating protection can also be provided for the flue gas turbine blade itself. At present, the more commonly used coating is "Great Wall No. 1", which is sprayed by plasma and mainly composed of Co, 30Cr, 10Ni, W, Si, C, etc. The designed service life is 2-3 years. The American coating is of chromium carbide type and tungsten carbide type, which is sprayed by explosion and also has a designed service life of 2-3 years, which is difficult to meet the current demand of 4-year or even 5-year maintenance of the catalytic device. In addition, Chinese patent CN 106906437 A discloses a high-corrosion-resistant and anti-fouling composite coating for flue gas turbine blades, which combines chromium carbide metal ceramic coating and alumina-titanium oxide ceramic coating to improve the erosion resistance and anti-fouling ability of the flue gas turbine blade and prolong the service life of the blade. However, the erosion resistance of chromium carbide relative to the base material has no substantial improvement. At room temperature, the erosion resistance of chromium carbide is much smaller than that of tungsten carbide. However, tungsten carbide will be oxidized at high temperatures exceeding 500℃, which limits the application of tungsten carbide. Therefore, the present application proposes a mixed coating of chromium carbide and tungsten carbide, and improves the spraying process, which is applied to the flue gas turbine blades working in high-temperature environments. SUMMARY

[0004] To solve the above technical problems, the present application provides a high-temperature-resistant and anti-fouling coating for flue gas turbine blades and a spraying method thereof. The high-temperature-resistant and anti-fouling coating adopts a mixed coating of tungsten carbide and chromium carbide, which can not only have high hardness to meet the erosion resistance requirement, but also have high-temperature resistance, high hardness and low porosity, and is suitable for the flue gas turbine blades used at high temperatures.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is:

[0006] A high-temperature-resistant anti-fouling coating for a flue gas turbine blade, the coating is a tungsten carbide-chromium carbide mixed coating, the tungsten carbide-chromium carbide mixed coating is formed by supersonic flame spraying of a mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles, the content of C in the mixed powder is 5.5-8.5wt%, the content of Cr is 15.5-21wt%, the content of Ni is 5.5-8.5wt%, and the balance is W, the particle size of the tungsten carbide particles, the chromium carbide particles and the nickel particles in the mixed powder is 5-10μm.

[0007] Further, the tungsten carbide and chromium carbide particles in the tungsten carbide-chromium carbide coating are hard phases, and the nickel particles are a binder phase.

[0008] By the above technical solution, the nickel particles are used as the binder phase, which has good matching with the nickel-based high-temperature alloy GH864 used in the flue gas turbine blade and small difference in thermal expansion coefficient, so that the coating can be prevented from falling off due to thermal fatigue caused by high-temperature thermal stress or start-stop; the tungsten carbide and chromium carbide mixed coating has high hardness to meet the requirement of erosion resistance and high-temperature resistance, and is suitable for use of the flue gas turbine blade at high temperature.

[0009] Another object of the present application is to provide a spraying method for the high-temperature-resistant anti-fouling coating for the flue gas turbine blade, comprising the following steps:

[0010] (1) the flue gas turbine blade is pretreated by sand blasting;

[0011] (2) the flue gas turbine blade after sand blasting pretreatment is pickled, alkali washed and washed with water, and is blown dry after water washing to keep the surface of the flue gas turbine blade dry;

[0012] (3) a mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles is prepared, and the mixed powder is dried to keep it dry;

[0013] (4) the flue gas turbine blade is fixed on a full-automatic supersonic flame spraying device, and the flue gas turbine blade is supersonic flame sprayed by using a full-automatic supersonic flame spraying equipment to cover the surface of the flue gas turbine blade with a layer of tungsten carbide-chromium carbide mixed coating;

[0014] (5) after the coating is cooled, the tungsten carbide-chromium carbide mixed coating obtained by supersonic flame spraying is subjected to laser cladding treatment;

[0015] (6) the tungsten carbide-chromium carbide mixed coating obtained by laser cladding treatment is subjected to polishing treatment.

[0016] Further, the specific step of the sand blasting pretreatment in step (1) is: firstly, a first sand blasting pretreatment is performed by using an abrasive with a particle size of 100 mesh to remove the scale and oxidation layer on the surface of the flue gas turbine blade until the metallic luster of the flue gas turbine blade is observed; and then, a second sand blasting pretreatment is performed by using an abrasive with a particle size of 400 mesh to remove burrs and other defects on the surface of the flue gas turbine blade, so as to control the uniformity of the surface roughness of the flue gas turbine blade.

[0017] By the above technical solution, burrs and other defects caused by the oversize sand particles can be removed, and the uniformity of the surface roughness of the flue gas turbine blade is controlled, so as to improve the bonding force between the sprayed coating and the blade substrate.

[0018] Further, the sand blasting pretreatment in step (1) is performed by using a manual sand blasting method, the sand blasting pressure is controlled to be 0.08-0.15 MPa, and the distance between the spray gun and the flue gas turbine blade is controlled to be 80-120 mm.

[0019] Further, the acid pickling solution in step (2) is a sulfuric acid solution with a concentration of 5%-20%, and the flue gas turbine blade is soaked in the acid pickling solution during the acid pickling process, and the soaking time is 1-2 min.

[0020] Further, the alkali pickling solution in step (2) is a sodium hydroxide solution with a concentration of 5%-10%, and the flue gas turbine blade is soaked in the alkali pickling solution during the alkali pickling process, and the soaking time is 3-5 min.

[0021] By the above technical solution, the flue gas turbine blade after the sand blasting pretreatment is subjected to acid pickling, alkali pickling and water washing, so as to further remove the catalyst, sand particles, oil stains and the like remaining on the surface of the blade, and ensure the cleanliness of the surface of the flue gas turbine blade.

[0022] Further, in step (4), during the high-velocity oxy-fuel spraying, the flue gas turbine blade is fixed at the center of the full-automatic high-velocity oxy-fuel spraying device and rotates at a constant speed at the center of the spraying device, the spray gun is fixed at one side of the full-automatic high-velocity oxy-fuel spraying device and moves up and down at a constant speed, the side surface of the flue gas turbine blade is sprayed by the full-automatic high-velocity oxy-fuel spraying device, and then the top and bottom of the flue gas turbine blade are sprayed by the handheld spray gun.

[0023] By the above technical solution, since the flue gas turbine blade is an irregular sabre-shaped blade and the coating spraying is required to be performed on both the front and back surfaces of the flue gas turbine blade, a full-automatic high-velocity oxy-fuel spraying device suitable for the flue gas turbine blade spraying is designed, in the spraying process, the flue gas turbine blade rotates by itself, and the spray gun moves from bottom to top or from top to bottom at one side of the flue gas turbine blade, so as to realize the spraying of the flue gas turbine blade.

[0024] Further, in the step (4), the supersonic flame spraying is performed by using 0.25-0.35 L / min of aviation kerosene as fuel and 0.6-0.7 m 3 / min of mixed gas of oxygen and nitrogen (the proportion of nitrogen is less than 10%) as gas, and the powder feeding speed is 5-7 g / min. The spraying distance is 100-150 mm, the rotating speed of the gas turbine blade is 3-4 r / min, the moving speed of the spray gun is 15-25 mm / min, and the spraying thickness is 0.3-0.5 mm.

[0025] Further, the full-automatic supersonic flame spraying device comprises a base, a plurality of supporting legs are arranged below the base, the gas turbine blade is arranged at the center of the base through a rotating mechanism, and the spray gun is arranged at one side of the gas turbine blade through a lifting mechanism.

[0026] The rotating mechanism comprises a transmission shaft and a first servo motor, the bottom of the gas turbine blade is fixed to the top of the transmission shaft, the upper part of the transmission shaft is rotatably arranged at the center of the base through a bearing, the first servo motor is fixed below the base, a matched bevel gear set is arranged on the transmission shaft and the output shaft of the first servo motor, and the first servo motor drives the transmission shaft and the gas turbine blade to rotate.

[0027] The lifting mechanism comprises a second servo motor, a rack and a directional sliding groove, the second servo motor is fixed below the base, a gear is fixedly arranged on the output shaft of the second servo motor, the directional sliding groove is fixedly arranged above the base and penetrates the base at the bottom, the rack is arranged in the directional sliding groove and is slidably connected with the directional sliding groove, the rack is engaged with the gear on the output shaft of the second servo motor, and the spray gun is fixedly arranged at one side of the rack.

[0028] Further, a glass fiber reinforced plastic cover is arranged above the base, the glass fiber reinforced plastic cover is detachably connected with the base, and a rectangular opening is arranged on the side of the glass fiber reinforced plastic cover close to the rack.

[0029] Through the above technical scheme, the first servo motor is used to drive the rotation of the gas turbine blade and the second servo motor is used to control the up-down movement of the spray gun in the full-automatic supersonic flame spraying device, so that the spraying speed can be conveniently controlled.

[0030] Further, the laser cladding treatment in the step (5) is performed by fixing the laser on one side of the rack and moving the rack, and one side of the laser is fixed with an argon gas nozzle, and the argon gas nozzle is at an angle of 15-20 degrees with the laser; the power of the laser is 3.5-4.0 kW, the size of the cladding spot is 5-10 mm, the overlap coefficient is 3-5%, the rotation speed of the gas turbine blade is 6-10 r / min, and the lifting speed of the laser is 25-50 mm / min; after the laser cladding treatment, the porosity of the tungsten carbide-chromium carbide mixed coating is less than 0.5%.

[0031] By the above technical solution, the laser cladding treatment can be performed by using the full-automatic supersonic spraying device, the rotation speed of the gas turbine blade and the moving speed of the laser are controlled, and the overlap coefficient is controlled to avoid the hardness reduction of the coating caused by multiple cladding, and the rotation speed of the gas turbine blade is controlled to avoid the excessive roughness caused by the slow cooling speed during the solidification of the coating; in addition, after the supersonic spraying of the tungsten carbide-chromium carbide coating, the laser cladding treatment is performed to improve the bonding force between the substrate and the coating, avoid the coating falling off caused by multiple thermal changes during the use of the gas turbine blade, and improve the properties of the coating surface and the surface density of the coating by the laser cladding.

[0032] Further, the polishing treatment in the step (6) specifically includes rough polishing and fine polishing; the rough polishing is performed by using a handheld grinding machine, and the rough polishing is wet polishing; the fine polishing is performed by using ultrasonic polishing, and the abrasive is W5 diamond particles; the fine polishing is dry polishing; and after the fine polishing, the roughness Ra of the surface of the gas turbine blade is less than or equal to 0.6 microns.

[0033] By the above polishing treatment, the catalyst particles can be prevented from being deposited on the gas turbine blade.

[0034] The beneficial effects of the present application are as follows:

[0035] (1) The tungsten carbide-chromium carbide mixed coating of the present application is a mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles, and the nickel particles are used as the binder phase, which has good matching with the nickel-based high-temperature alloy GH864 used in the gas turbine blade, and the difference in the thermal expansion coefficient is small, so that the coating can be prevented from falling off caused by thermal fatigue due to high-temperature thermal stress or start-stop; the tungsten carbide-chromium carbide mixed coating has high hardness to meet the erosion resistance requirement, and has high-temperature resistance, and is suitable for the use of the gas turbine blade at high temperature;

[0036] (2) The present application adopts supersonic spraying combined with laser cladding treatment, which can improve the bonding force between the substrate and the coating, avoid the coating falling off of the flue gas turbine blade due to multiple thermal changes during use, and improve the properties of the coating surface and the surface density of the coating through laser cladding, the porosity of the tungsten carbide-chromium carbide mixed coating is less than 0.5%, and the corrosion resistance is improved;

[0037] (3) The tungsten carbide-chromium carbide mixed coating prepared by the process of the present application has a microhardness of more than 1000HV, can resist catalyst particle erosion, and has a bonding strength between the coating and the substrate of more than 100MPa, avoiding the coating falling off of the flue gas turbine blade due to multiple thermal changes during use;

[0038] (4) In order to reduce the surface fouling of the flue gas turbine blade, the present application also performs polishing treatment on the coating surface, reduces the deposition of catalyst particles on the flue gas turbine blade, prevents the surface fouling of the blade from causing changes in rotor balance and causing the flue gas heat efficiency to decrease;

[0039] (5) The present application also designs a full-automatic supersonic flame spraying device suitable for spraying the flue gas turbine blade, in the spraying process, the flue gas turbine blade rotates, the spray gun moves from bottom to top or from top to bottom on one side of the flue gas turbine blade, realizing the spraying of the flue gas turbine blade, and in the full-automatic supersonic flame spraying device, a first servo motor is used to drive the rotation of the flue gas turbine blade, and a second servo motor is used to control the up-down movement of the spray gun, facilitating the control of the spraying speed; in addition, the full-automatic supersonic spraying device can be used for laser cladding treatment, by controlling the rotation speed of the flue gas turbine blade and the movement speed of the laser, the lap coefficient is controlled, avoiding the hardness of the coating from decreasing due to multiple cladding, and at the same time, the rotation speed of the flue gas turbine blade is controlled, avoiding the roughness from being too large due to the slow cooling speed during the solidification of the coating. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0041] Figure 1 is the process flow chart of the present application;

[0042] Figure 2 is the overall structure schematic diagram of the full-automatic supersonic flame spraying device;

[0043] Figure 3 is the structure schematic diagram of the rotating mechanism in the full-automatic supersonic flame spraying device. DETAILED DESCRIPTION

[0044] In order to make the objects, technical solutions and effects of the present application clearer and more apparent, the present application will be further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not used to limit the present application. The present application will be described in detail below with reference to the drawings.

[0045] Embodiment 1

[0046] The embodiment provides a spraying method for a high-temperature resistant anti-fouling coating of a flue gas turbine blade, and adopts a full-automatic supersonic flame spraying device to spray the coating on the surface of the flue gas turbine blade. The flue gas turbine blade is forged by a nickel-based high-temperature alloy GH864, and the flue gas turbine blade can be cleaned and sprayed during the planned shutdown or overhaul after the flue gas turbine rotor is disassembled.

[0047] First, the specific structure of the full-automatic supersonic flame spraying device used in the spraying operation will be described in detail.

[0048] Referring to Figure 2 and Figure 3 , the full-automatic supersonic flame spraying device comprises a base 1, a supporting leg 2 is arranged below the base 1, a flue gas turbine blade 3 is rotationally arranged at the center position of the base 1 through a rotating mechanism 4, and a spraying gun 5 is arranged at one side of the flue gas turbine blade 3 through a lifting mechanism 6.

[0049] The rotating mechanism 4 comprises a transmission shaft 41 and a first servo motor 42, the bottom of the flue gas turbine blade 3 is fixed to the top of the transmission shaft 41, the upper part of the transmission shaft 41 is rotationally arranged at the center position of the base 2 through a bearing 43, the first servo motor 42 is fixed below the base 1, a matched bevel gear set 44 is arranged on the output shaft of the transmission shaft 41 and the first servo motor 42, and the first servo motor 42 drives the transmission shaft 41 and the flue gas turbine blade 3 to rotate.

[0050] The lifting mechanism 6 comprises a second servo motor 61, a rack 62 and a directional sliding groove 63, the second servo motor 61 is fixed below the base 1, a gear 64 is fixedly arranged on the output shaft of the second servo motor 61, the directional sliding groove 63 is fixedly arranged above the base 1 and penetrates through the base 1 at the bottom, the rack 62 is arranged in the directional sliding groove 63 and is in sliding connection with the directional sliding groove 63, the rack 64 is in mesh with the gear on the output shaft of the second servo motor 61, and the spraying gun 5 is fixedly arranged at one side surface of the rack 62, and the second servo motor 61 drives the rack 62 and the spraying gun 5 to lift.

[0051] The base 1 is further provided with a glass fiber reinforced plastic cover 7, which avoids pollution to the surrounding environment during spraying. The glass fiber reinforced plastic cover 7 is detachably connected with the base 1. The glass fiber reinforced plastic cover 7 is provided with a rectangular opening 8 on the side close to the rack 62, so that the spray gun can be inserted into the glass fiber reinforced plastic cover to spray the surface of the flue gas turbine blade without affecting the up-and-down movement of the spray gun.

[0052] Before supersonic flame spraying, the flue gas turbine blade 3 is first fixed on the top of the transmission shaft 41 through the tenon slot at the bottom of the flue gas turbine blade 3 and is fixed by bolts to prevent the flue gas turbine blade 3 from being thrown out during rotation. Then, the spray gun 5 is fixed on the side surface of the rack 62. By controlling the current of the first servo motor 42 and the second servo motor 61, the rotation speed of the flue gas turbine blade and the spraying speed of the spray gun can be controlled.

[0053] With reference to Figure 1 , the flue gas turbine blade is sprayed by the full-automatic supersonic flame spraying device. The spraying process specifically includes the following steps:

[0054] (1) The flue gas turbine blade is pretreated by sand blasting. The specific steps of sand blasting pretreatment are as follows: first, 100-mesh abrasive is used for first sand blasting pretreatment to remove the scale layer and the oxidation layer on the surface of the flue gas turbine blade until the metallic luster of the flue gas turbine blade is seen; then, 400-mesh abrasive is used for second sand blasting pretreatment to remove burrs and other defects on the surface of the flue gas turbine blade to control the uniformity of the overall surface roughness of the flue gas turbine blade. The sand blasting pretreatment is performed in a manual sand blasting mode, the sand blasting pressure is controlled to be 0.1 MPa, and the distance between the spray gun and the flue gas turbine blade is 100 mm.

[0055] (2) The flue gas turbine blade after sand blasting pretreatment is subjected to pickling, alkali washing and water washing. After water washing, the flue gas turbine blade is blown dry to keep the surface of the flue gas turbine blade dry. The pickling solution is a 10% sulfuric acid solution. During pickling, the flue gas turbine blade is soaked in the pickling solution for 1 min. The alkali washing solution is a 10% sodium hydroxide solution. During alkali washing, the flue gas turbine blade is soaked in the alkali washing solution for 4 min.

[0056] (3) A mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles is prepared and dried to keep the mixed powder dry. The content of C in the mixed powder is 6.2 wt%, the content of Cr is 16.0 wt%, the content of Ni is 6.0 wt%, and the balance is W. The particle size of the tungsten carbide particles, the chromium carbide particles and the nickel particles in the mixed powder is 10 μm. The tungsten carbide particles and the chromium carbide particles are hard phases, and the nickel particles are a binder phase.

[0057] (4) fixing the turbine blade on the full-automatic high-velocity oxygen fuel spraying device, i.e. the turbine blade is fixed on the top of the transmission shaft through the tenon slot at the bottom of the turbine blade and is fixed by bolts, then the spraying gun is fixed on the side surface of the rack, the turbine blade is sprayed by the full-automatic high-velocity oxygen fuel spraying device, so that the turbine blade surface is covered with a layer of tungsten carbide-chromium carbide mixed coating; during the high-velocity oxygen fuel spraying process, the first servo motor drives the turbine blade to rotate at a constant speed, the second servo motor drives the spraying gun to move upwards at a constant speed for spraying, when the side surface of the turbine blade is sprayed, the top and bottom of the turbine blade are sprayed by the hand-held spraying gun, and the bottom of the turbine blade needs to be detached from the transmission shaft for spraying.

[0058] During the high-velocity oxygen fuel spraying process in step (4), aviation kerosene is used as fuel, and the mixed gas of oxygen and nitrogen is used as gas, the feeding speed is 6 g / min, the spraying distance is 100 mm, the rotating speed of the turbine blade is 3 r / min, the moving speed of the spraying gun is 15 mm / min, and the spraying thickness is 0.5 mm, so that the tungsten carbide-chromium carbide mixed coating is obtained.

[0059] The roughness of the surface of the tungsten carbide-chromium carbide mixed coating obtained by the above high-velocity oxygen fuel spraying is detected to be 4 μm.

[0060] (5) laser cladding treatment is performed on the tungsten carbide-chromium carbide mixed coating obtained by the high-velocity oxygen fuel spraying; during the laser cladding treatment, the turbine blade is fixed on the top of the transmission shaft, the laser is arranged on the side surface of the rack, and an argon gas nozzle is fixed on one side of the laser, and the argon gas nozzle and the laser form an angle of 20°; the power of the laser is 3.5 kW, the size of the cladding spot is 10 mm, the overlap coefficient is 5%, the rotating speed of the turbine blade is 8 r / min, and the lifting speed of the laser is 30 mm / min.

[0061] The roughness of the surface of the tungsten carbide-chromium carbide mixed coating obtained by the above laser cladding treatment is detected to be 3 μm.

[0062] (6) polishing treatment is performed on the tungsten carbide-chromium carbide mixed coating obtained by the laser cladding treatment after cooling; the polishing treatment specifically includes coarse polishing and fine polishing: during the coarse polishing, a hand-held grinding machine is used for coarse polishing, and wet polishing is used for coarse polishing, water flow is added during polishing, and the type of the turbine blade sandpaper is 220 mesh, 400 mesh and 800 mesh in turn; during the fine polishing, ultrasonic polishing is used, the abrasive is W5 diamond particles, and dry polishing is used during the fine polishing without adding working fluid. After the above polishing treatment, the roughness of the coating surface is 0.56 μm.

[0063] Example 2

[0064] The present embodiment 2 provides a spraying method for high-temperature resistant anti-fouling coating of flue gas turbine blade, the coating is tungsten carbide-chromium carbide mixed coating, the tungsten carbide-chromium carbide mixed coating is mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles by high-velocity oxygen fuel spraying, and laser cladding treatment is carried out on the surface of the tungsten carbide-chromium carbide coating, and polishing treatment is carried out after the laser cladding treatment is completed and cooled. The present embodiment also uses the full-automatic high-velocity oxygen fuel spraying device described in the above embodiment 1 for spraying, which specifically comprises the following steps:

[0065] (1) The flue gas turbine blade is pretreated by sand blasting, and the specific sand blasting pretreatment steps are the same as those of embodiment 1.

[0066] (2) The flue gas turbine blade after sand blasting pretreatment is pickled, alkali washed and washed with water, and then dried, so that the surface of the flue gas turbine blade is kept dry, and the specific pickling and alkali washing steps are the same as those of embodiment 1.

[0067] (3) The mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles is prepared, and the mixed powder is dried to keep the mixed powder dry; the content of C in the mixed powder is 8.2wt%, the content of Cr is 20.1wt%, the content of Ni is 7.5wt%, and the balance is W; the particle size of the tungsten carbide particles, chromium carbide particles and nickel particles in the mixed powder is 10μm, wherein the tungsten carbide and chromium carbide particles are hard phases, and the nickel particles are binder phases.

[0068] (4) The flue gas turbine blade is fixed on the full-automatic high-velocity oxygen fuel spraying device, that is, the flue gas turbine blade is fixed on the top of the transmission shaft through the tenon and slot at the bottom of the flue gas turbine blade, and fixed by bolts, then the spray gun is fixed on one side of the rack, and the flue gas turbine blade is sprayed by the full-automatic high-velocity oxygen fuel spraying equipment, so that the surface of the flue gas turbine blade is covered with a layer of tungsten carbide-chromium carbide mixed coating; during the high-velocity oxygen fuel spraying process, the first servo motor drives the flue gas turbine blade to rotate at a constant speed, the second servo motor drives the spray gun to move upwards at a constant speed for spraying, when the side of the flue gas turbine blade is sprayed, the top and bottom of the flue gas turbine blade are sprayed by hand, and the bottom of the flue gas turbine blade needs to be disassembled from the transmission shaft for spraying.

[0069] In this step (4), aviation kerosene is used as fuel, and the mixed gas of oxygen and nitrogen is used as gas, the feeding speed is 7g / min, the spraying distance is 100mm, the rotating speed of the flue gas turbine blade is 4r / min, the moving speed of the spray gun is 20mm / min, and the spraying thickness is 0.5mm, so that the tungsten carbide-chromium carbide mixed coating is obtained.

[0070] The roughness of the surface of the tungsten carbide-chromium carbide mixed coating obtained by the above supersonic flame spraying is detected to be 4.5 μm.

[0071] (5) The laser cladding treatment is performed on the tungsten carbide-chromium carbide mixed coating obtained by the supersonic flame spraying; when the laser cladding treatment is performed, the flue gas turbine blade is fixed on the top of the transmission shaft, the laser is fixed on one side of the rack, and one side of the laser is fixed with an argon gas nozzle, the argon gas nozzle is at an angle of 20° with the laser; the power range of the laser is 4.0 kW, the size of the cladding spot is 10 mm, the lap coefficient is 5%, the rotation speed of the flue gas turbine blade is 10 r / min, and the lifting speed of the laser is 40 mm / min.

[0072] The roughness of the surface of the tungsten carbide-chromium carbide mixed coating obtained by the above laser cladding treatment is detected to be 3.2 μm.

[0073] (6) The polishing treatment is performed on the tungsten carbide-chromium carbide mixed coating obtained by the laser cladding treatment after cooling; the polishing treatment specifically includes rough polishing and fine polishing: when the rough polishing is performed, the handheld grinding machine is used for rough polishing, and the wet polishing is used for rough polishing, water flow is added during polishing, and the blade sandpaper of the grinding machine is used in the order of 220 mesh, 400 mesh and 800 mesh; when the fine polishing is performed, the ultrasonic polishing is used, the abrasive is W5 diamond particles, and the dry polishing is used for fine polishing without adding working fluid. After the above polishing treatment, the roughness of the surface of the coating is 0.6 μm.

[0074] Comparative Example 1

[0075] The difference between the comparative example 1 and the example 1 is that in the comparative example 1, only the tungsten carbide-chromium carbide mixed coating is obtained by the supersonic flame spraying, and then the polishing treatment is performed on the tungsten carbide-chromium carbide mixed coating, the roughness of the surface of the coating after the polishing treatment is 0.62 μm, and the laser cladding treatment is not performed on the comparative example 1.

[0076] The flue gas turbine blade with the tungsten carbide-chromium carbide mixed coating obtained by the example 1, the example 2 and the comparative example 1 is subjected to the porosity detection, the hardness detection, and the bonding strength detection between the coating and the substrate, and the detection results are shown in Table 1.

[0077] Table 1 Detection results of the example 1, 2 and the comparative example 1

[0078]

[0079]

[0080] As can be seen from Table 1, after the laser cladding treatment is applied, the porosity of the coating is significantly reduced, the microhardness slightly decreases, but the decrease degree is small, the bonding strength between the coating and the substrate is significantly improved, and the falling rate of the coating during use can be reduced.

[0081] The parts not mentioned in the present application can be realized by using or referring to the existing technology.

[0082] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades, characterized in that, The coating is a tungsten carbide-chromium carbide mixed coating, which is formed by spraying a mixture of tungsten carbide particles, chromium carbide particles and nickel particles with a supersonic flame. The mixed powder contains 5.5~8.5wt% C, 15.5~21wt% Cr, 5.5~8.5wt% Ni, with the balance being W. The particle size of the tungsten carbide particles, chromium carbide particles and nickel particles in the mixed powder is 5~10μm. The spraying method includes the following steps: (1) The flue gas turbine blades are pretreated by sandblasting; (2) After sandblasting pretreatment, the flue gas turbine blades are acid washed, alkali washed and water washed, and then blown dry to keep the surface of the flue gas turbine blades dry. (3) Prepare a mixed powder of tungsten carbide particles, chromium carbide particles and nickel particles, and dry the mixed powder to keep it dry; (4) Fix the flue gas turbine blades on the fully automatic supersonic flame spraying device, and use the fully automatic supersonic flame spraying device to spray the flue gas turbine blades with supersonic flame, so that the surface of the flue gas turbine blades is covered with a layer of tungsten carbide-chromium carbide mixed coating. (5) Laser cladding treatment is performed on the tungsten carbide-chromium carbide mixed coating obtained by supersonic flame spraying; (6) Polish the tungsten carbide-chromium carbide mixed coating obtained by laser cladding; In step (4), when supersonic flame spraying is performed, the flue gas turbine blades are fixed at the center of the fully automatic supersonic flame spraying device and the flue gas turbine blades rotate at a constant speed at the center of the spraying device. The spray gun is fixed on one side of the fully automatic supersonic flame spraying device and the spray gun can move up and down at a constant speed. The side of the flue gas turbine blades is sprayed through the fully automatic supersonic flame spraying device. After the side of the flue gas turbine blades is sprayed, the top and bottom of the flue gas turbine blades are sprayed by holding the spray gun. In step (4), during supersonic flame spraying, aviation kerosene is used at a flow rate of 0.25~0.35L / min, and the gas is a mixture of oxygen and nitrogen, with nitrogen accounting for <10%, and a flow rate of 0.6~0.7m³ / min. 3 The powder feeding speed is 5~7g / min, the spraying distance is 100~150mm, the rotation speed of the flue gas turbine blades is 3~4r / min, the moving speed of the spray gun is 15~25mm / min, and the spraying thickness is 0.3~0.5mm. When performing laser cladding in step (5), the laser power range is 3.5~4.0kW, the cladding spot size is 5~10 mm, the overlap coefficient is 3~5%, the rotation speed of the flue gas turbine blades is 6~10r / min, and the lifting speed of the laser is 25~50 mm / min. The bonding strength between the tungsten carbide-chromium carbide mixed coating obtained in step (6) and the flue gas turbine blade is 105~110MPa; The fully automatic supersonic flame spraying device includes a base, with support legs provided below the base. The flue gas turbine blades are rotatably positioned at the center of the base via a rotating mechanism, and the spray gun is positioned on one side of the flue gas turbine blades via a lifting mechanism. The rotating mechanism includes a drive shaft and a first servo motor. The bottom of the flue gas turbine blades is fixed to the top of the drive shaft. The upper part of the drive shaft is rotatably mounted at the center of the base via a bearing. The first servo motor is fixed below the base. The drive shaft and the output shaft of the first servo motor are provided with a bevel gear set that cooperates with each other. The first servo motor drives the drive shaft and the flue gas turbine blades to rotate. The lifting mechanism includes a second servo motor, a rack, and a directional slide. The second servo motor is fixed below the base, and a gear is fixedly installed on the output shaft of the second servo motor. The directional slide is fixed above the base, and the bottom of the directional slide penetrates the base. The rack is installed in the directional slide and is slidably connected to the directional slide. The rack meshes with the gear on the output shaft of the second servo motor. The spray gun is fixedly installed on one side of the rack. The second servo motor drives the rack and the spray gun to lift and lower. A fiberglass cover is provided above the base, and the fiberglass cover is detachably connected to the base. A rectangular opening is provided on the side of the fiberglass cover near the rack.

2. The method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 1, characterized in that, In the tungsten carbide-chromium carbide coating, tungsten carbide and chromium carbide particles are hard phases, and nickel particles are binder phases.

3. The method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 1, characterized in that, The specific steps of the sandblasting pretreatment in step (1) are as follows: First, a sandblasting pretreatment is performed using abrasive with a particle size of 100 mesh to remove the scale and oxide layer on the surface of the flue gas turbine blades until the metallic luster of the flue gas turbine blades is visible; then, a secondary pre-sandblasting treatment is performed using abrasive with a particle size of 400 mesh to remove burr defects on the surface of the flue gas turbine blades and control the overall surface roughness of the flue gas turbine blades to be uniform.

4. The method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 3, characterized in that, The sandblasting pretreatment in step (1) is carried out manually, with the sandblasting pressure controlled at 0.08~0.15MPa and the distance between the spray gun and the flue gas turbine blades at 80~120mm.

5. The method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 1, characterized in that, In step (2), the pickling solution is a sulfuric acid solution with a concentration of 5% to 20%. During the pickling process, the flue gas turbine blades are immersed in the pickling solution for 1 to 2 minutes.

6. The method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 1, characterized in that, In step (2), the alkaline washing solution is a sodium hydroxide solution with a concentration of 5% to 10%. During the alkaline washing process, the flue gas turbine blades are immersed in the alkaline washing solution for 3 to 5 minutes.

7. The method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 1, characterized in that, When performing laser cladding in step (5), the laser is fixed to one side of the rack and moves with the rack, and an argon nozzle is fixed to one side of the laser, with the argon nozzle at an angle of 15° to 20° to the laser.

8. A method for spraying a high-temperature resistant and anti-scaling coating for flue gas turbine blades according to claim 1, characterized in that, The polishing process in step (6) specifically includes rough polishing and fine polishing. During rough polishing, a hand-held grinding wheel is used for rough polishing, and the rough polishing is wet polishing. During fine polishing, ultrasonic polishing is used, and W5 diamond microparticles are used for abrasive. During fine polishing, dry polishing is used. After fine polishing, the surface roughness Ra of the flue gas turbine blades is ≤0.6μm.

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