阅读说明：本技术 一种用于超低压等离子喷涂的反极性等离子喷涂枪 (Reversed polarity plasma spraying gun for ultra-low pressure plasma spraying ) 是由 余德平 刘方圆 邱吉尔 尹政鑫 姚进 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种用于超低压等离子喷涂的反极性等离子喷涂枪,包括枪体部分和外部喷管部分；枪体部分采用前置中心通孔阴极和后置杯状阳极的反极性电极结构设计,使喷枪在较低电流条件下实现更大的功率,降低了电极的烧蚀和涂层的污染；外部喷管部分采用带有直筒状通孔的石墨喷管,通过压缩射流提高了低压下的射流温度,并大幅延长了粉末在高温射流区域的停留时间,使粉末可以在低压环境和较小喷枪功率条件下也能充分的熔融和气化；采用气体冷却来定量地冷却石墨喷管,使喷管内壁处于较高的温度,结合较大的等离子气体流量,有效解决了粉末在管壁内壁沉积堵塞的问题。(The invention discloses a reverse polarity plasma spraying gun for ultra-low pressure plasma spraying, which comprises a gun body part and an external spray pipe part; the gun body adopts the reverse polarity electrode structure design of the front center through hole cathode and the rear cup-shaped anode, so that the spray gun realizes higher power under the condition of lower current, and the ablation of the electrode and the pollution of a coating are reduced; the graphite spray pipe with the straight cylindrical through hole is adopted in the outer spray pipe part, the jet flow temperature under low pressure is improved through compressed jet flow, the retention time of powder in a high-temperature jet flow area is greatly prolonged, and the powder can be fully melted and gasified under the conditions of a low-pressure environment and low spray gun power; the graphite spray pipe is quantitatively cooled by adopting gas cooling, so that the inner wall of the spray pipe is at a higher temperature, and the problem of powder deposition and blockage on the inner wall of the pipe wall is effectively solved by combining with a larger plasma gas flow.)

1. The utility model provides a reverse polarity plasma spraying rifle for ultra low pressure plasma spraying which characterized in that: comprises a gun body 1 and an external spray pipe 10; the gun body 1 comprises a front center through hole cathode 2, a rear cup-shaped anode 3, an insulating main body 4, a main air inlet pipe 5, a main air distribution ring 6, a cooling water inlet pipe 7 and a cooling water outlet pipe 8; the external spray pipe 10 comprises a ceramic gasket 11, a graphite spray pipe 12, a tungsten lining 13, an air cooling sleeve 14, a cooling gas inlet pipe 15, a cooling gas outlet pipe 16, a powder feeding pipe 17 and a thermocouple 18; the gun body 1 and the external spray pipe 10 are tightly pressed and hermetically connected through bolts on an air cooling sleeve 14; the graphite spray pipe 12, the cathode 2 and the anode 3 are coaxially arranged in sequence from front to back, and are insulated from each other; water cooling grooves are formed in the outer portions of the cathode 2 and the anode 3, cooling water enters from a water inlet pipe 7, flows through the water cooling grooves in the outer portions of the anode 3 and the cathode 2 in sequence and then flows out from a water outlet pipe 8; a main gas distribution ring 6 is arranged between the cathode 2 and the anode 3, and plasma forming gas enters from a main gas inlet pipe 5 and flows into the arc chamber after flowing through the main gas distribution ring 6; a tungsten lining 13 is embedded in the graphite nozzle 12, and the rear end of the nozzle, which is close to the cathode outlet, is provided with a powder feeding hole 19 and communicated with a powder feeding pipe 17; a cooling groove is formed in the outer part of the graphite spray pipe 12, cooling gas enters from a cooling gas inlet pipe 15 and flows out from a cooling gas outlet pipe 16 after flowing through the cooling groove; the two ends of the outer part of the graphite nozzle 12 are respectively provided with a counter bore, the distance from the bottom of the counter bore to the graphite nozzle channel is 1-2mm, and the temperature measuring end of the thermocouple is contacted with the bottom of the counter bore for measuring temperature.

2. The reverse polarity plasma spray gun for ultra low pressure plasma spray coating of claim 1 wherein: the front central through hole cathode 2 is connected with the negative pole of a power supply, and the rear cup-shaped anode 3 is connected with the positive pole of the power supply.

3. The reverse polarity plasma spray gun for ultra low pressure plasma spray coating of claim 1 wherein: the cathode 2 is made of a copper embedded tungsten lining, and the anode 3 is made of a copper embedded molybdenum lining.

4. The reverse polarity plasma spray gun for ultra low pressure plasma spray coating of claim 1 wherein: 8 air holes with the diameter of 1-2mm are uniformly distributed on the main air distribution ring 6, and the radial rotation angle of the air holes is 45 ℃.

5. The reverse polarity plasma spray gun for ultra low pressure plasma spray coating of claim 1 wherein: the aperture of the powder feeding hole 19 is 1-2mm, the distance between the outlet of the powder feeding hole and the outlet of the cathode is 2-5mm, and the distance between the outlet of the graphite spray pipe is 60-120 mm.

6. The reverse polarity plasma spray gun for ultra low pressure plasma spray coating of claim 1 wherein: the central through hole of the graphite nozzle 12 is in a straight cylinder shape, and the inner diameter is 4-10 mm.

7. The reverse polarity plasma spray gun for ultra low pressure plasma spray coating of claim 1 wherein: the external cooling tank of the graphite nozzle 12 is cooled by inert gas such as nitrogen, argon and the like.

Technical Field

The invention relates to the field of plasma spraying, in particular to a reverse polarity plasma spraying gun for ultra-low pressure plasma spraying.

Background

The ultra-low pressure plasma spraying can prepare a columnar structure thermal barrier coating similar to electron beam vapor deposition, and compared with the traditional atmospheric spraying coating, the coating has better tolerance and thermal shock resistance, so that the coating is widely applied to key hot-end components of aero-engines with higher requirements on the performance of the coating. Under the environment of ultra-low pressure (50-200 Pa), the plasma jet ejected from the outlet of the spray gun can be expanded to 2m long, and the diameter can be increased to 200-400 mm, but because the density of the plasma jet outside the outlet is obviously reduced, the heating capacity of the external plasma jet on the powder is also greatly reduced, and the realization of partial or complete gasification of the high-melting-point ceramic powder faces huge challenges.

The current solutions mainly include two, one is to use ultra high arc current (2500-; the other is to add a section of extended water-cooled flared nozzle at the outlet of the medium-power atmospheric spray gun to extend the residence time of the powder in the high-temperature region of the jet by feeding the powder into the longer water-cooled nozzle, such as a low-pressure plasma spray gun with the grant publication No. CN 101954324B. The above two schemes have the following disadvantages: 1) the two spray gun electrodes are rod-shaped cathodes and straight cylindrical anodes, and adopt a traditional positive connection method with a power supply, the structure has lower arc voltage (30-50V), and the electrode can be quickly ablated due to the increase of current only by increasing the current at the aim of realizing higher power and jet enthalpy, so that the service life of the electrode is shortened, the coating is polluted, and the further popularization and application of the spray gun are limited; 2) the outside of the spray pipe is cooled by cooling water, so that the heat of the spray pipe is rapidly taken away, the inner wall of the spray pipe is in a lower temperature state, and when the molten and gasified powder with higher temperature collides with the inner wall of the cold spray pipe, the molten and gasified powder is rapidly cooled, solidified and bonded, so that the spray pipe is blocked, and the spray gun cannot normally work for a long time; 3) the flared nozzle design that expands gradually can reduce the compression effect of spray tube to efflux to a certain extent to reduce the heating effect of efflux to the powder, make the powder hardly realize abundant melting and gasification.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a reversed polarity plasma spraying gun for ultralow pressure plasma spraying, which adopts the design of reversed electrode arrangement and an externally extended air-cooled straight cylindrical spray pipe, can realize higher arc voltage and spray gun power under the condition of lower input arc current, greatly improves the retention time of powder in a high temperature area of a jet flow core, inhibits the deposition and blockage of the powder by controlling the flow of plasma gas and the temperature of the inner wall of a graphite spray pipe, and maximally realizes the sufficient melting and gasification of the powder in an ultralow pressure environment.

In order to achieve the above object, the technical solution of the present invention is as follows.

The invention discloses a reverse polarity plasma spraying gun for ultra-low pressure plasma spraying, which comprises a gun body 1 and an external spray pipe 10; the gun body 1 comprises a front center through hole cathode 2, a rear cup-shaped anode 3, an insulating main body 4, a main air inlet pipe 5, a main air distribution ring 6, a cooling water inlet pipe 7 and a cooling water outlet pipe 8; the external spray pipe 10 comprises a ceramic gasket 11, a graphite spray pipe 12, a tungsten lining 13, an air cooling sleeve 14, a cooling gas inlet pipe 15, a cooling gas outlet pipe 16, a powder feeding pipe 17 and a thermocouple 18; the lance 1 and the outer lance 10 are connected in a pressure-tight manner by means of bolts on an air-cooled jacket 14.

Graphite spray tube 12, negative pole 2, positive pole 3 from preceding backward in proper order with the axle center arrangement, realize keeping apart and insulating through main gas distribution ring 6 of polytetrafluoroethylene between negative pole 2 and the positive pole 3, keep apart and insulating through boron nitride ceramic gasket 11 between graphite spray tube 12 and the negative pole 2, prevent that the negative pole arc root from transferring to the graphite spray tube on, and then ablating spray tube and pollution coating.

The outside of the cathode 2 and the anode 3 is provided with a water cooling tank, cooling water enters from a water inlet pipe 7, flows through the water cooling tank outside the anode 3 and the cathode 2 in sequence and then flows out from a water outlet pipe 8, and forced cooling of the cathode 2 and the anode 3 is realized.

A main gas distribution ring 6 is arranged between the cathode 2 and the anode 3, plasma forming gas enters from a main gas inlet pipe 5, flows through the main gas distribution ring 6 with a rotary gas distribution hole and then enters into an arc chamber channel, and an initial arc 9 between the cathode and the anode is stretched and prolonged by the gas flow with a rotary direction and is kept in a dynamic stable state.

A tungsten lining 13 is embedded in the graphite spray pipe 12, and the tungsten lining has a high melting point and good mechanical properties, so that the erosion and abrasion of powder to the spray pipe can be effectively reduced; the rear end of the nozzle, close to the cathode outlet, is provided with a powder feeding hole 19 and is communicated with a powder feeding pipe 17, and the powder is fed into a central jet flow high-temperature area in the nozzle along the powder feeding hole 19 by carrier gas.

The graphite spray pipe 12 is provided with a cooling groove on the outside, inert cooling gas with a certain flow controlled by a mass flow meter enters from a cooling gas inlet pipe 15 and flows out from a cooling gas outlet pipe 16 after flowing through the cooling groove, and therefore quantitative cooling and protection of the graphite spray pipe are achieved.

Counter bores are respectively arranged at two ends of the outer part of the graphite spray pipe 12, the distance between the bottom of each counter bore and a graphite spray pipe channel is 1-2mm, the temperature measuring end of a thermocouple is in contact with the bottom of each counter bore for measuring temperature, the flow of cooling gas outside the spray pipe is adjusted according to the power of a spray gun and the size of the spray pipe, and the temperature of the inner wall of the spray pipe is controlled within the range of 2000 ℃ and 2500 ℃ through real-time temperature measurement of the thermocouple; therefore, by reducing the temperature difference between the inner wall of the nozzle and the melted and gasified powder and using a larger plasma gas flow rate, the deposition and blockage of the melted and gasified powder on the hot wall of the nozzle can be effectively inhibited.

The front center through hole cathode 2 is connected with a power supply cathode, the rear cup-shaped anode 3 is connected with a power supply anode, and through the design of the reverse electrode structure, an electric arc can be stretched to the maximum extent on a two-electrode gun structure, so that a cathode arc root is easily stretched and fixed at a cathode outlet, a larger electric arc voltage is realized, and further, a larger spray gun power can be realized under a small current; therefore, the design can increase the temperature and enthalpy of the jet flow and simultaneously reduce electrode erosion, thereby prolonging the service life of the electrode and the spray gun.

The cathode 2 is made of a copper embedded tungsten lining, and the anode 3 is made of a copper embedded molybdenum lining, so that the ablation of the electrode and the pollution to a coating can be further reduced.

8 air holes with the diameter of 1-2mm are uniformly distributed on the main air distribution ring 6, the radial rotation angle of the air holes is 45 ℃, electric arcs can be effectively stabilized and arc roots can periodically rotate through rotary air inlet, and the arc roots are prevented from being continuously ablated at a certain point of an electrode.

The aperture of the powder feeding hole 19 is 1-2mm, and the distance between the outlet of the powder feeding hole and the cathode outlet is 2-5mm, so that powder can be fed into a central high-temperature area close to the cathode outlet of the spray gun; the distance between the outlet of the powder feeding hole and the outlet of the graphite spray pipe is 60-120 mm, so that the heating time of the powder in the high-temperature jet of the spray pipe can be greatly prolonged, the jet energy utilization rate is improved, and the powder is fully melted and gasified.

The central through hole of the graphite spray pipe 12 is in a straight cylinder shape, the inner diameter is 4-10mm, and the design of a cylindrical flow channel with relatively small diameter can effectively compress jet flow, improve jet flow temperature, and enable powder to be always in a high-temperature jet flow area in the process of entering the spray pipe and leaving the spray pipe.

The external cooling tank of the graphite nozzle 12 is cooled by inert gases such as nitrogen and argon, and the inert gases are used for cooling, so that the oxidation and consumption of graphite at high temperature can be prevented, and the service life of the graphite nozzle is greatly prolonged.

The reversed polarity plasma spraying gun for ultra-low pressure plasma spraying has the following advantages: 1) under the condition of lower arc current (500A), the power of the spray gun can reach 60 Kw, so that the ablation effect of large current on the electrode can be greatly reduced, and the service life of the spray gun is prolonged; 2) the design of the external small-caliber straight cylindrical spray pipe greatly improves the retention time of the powder in a high-temperature jet area, improves the utilization rate of the energy of the spray gun, and ensures that the spray gun can realize the full melting and gasification of the ceramic powder with relatively low power in an ultra-low pressure environment; 3) the design of the gas-cooled additional spray pipe can accurately control the temperature of the inner wall of the spray pipe, and the deposition and blockage problems of the fused and gasified powder in the spray pipe are effectively solved by combining the higher temperature of the inner wall and the faster plasma jet speed.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of the present invention.

Reference numerals: 1-gun body; 2-front centered through hole cathode; 3-rear cup-shaped anode; 4-an insulating body; 5, main air inlet pipe; 6-main gas distribution ring; 7-cooling water inlet pipe; 8-a cooling water outlet pipe; 9-electric arc; 10-an external nozzle; 11-a ceramic gasket; 12-a graphite nozzle; 13-tungsten liner; 14-air-cooled sleeve; 15-cooling gas inlet pipe; 16-a cooling gas outlet pipe; 17-powder feeding pipe; 18-a thermocouple; 19-powder feeding hole.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived from the embodiments of the present invention by a person skilled in the art without any creative effort, should be included in the protection scope of the present invention.

As shown in fig. 1, a reverse polarity plasma spray gun for ultra low pressure plasma spray according to the present invention includes a gun body 1 and an outer nozzle 10; the gun body 1 comprises a front center through hole cathode 2, a rear cup-shaped anode 3, an insulating main body 4, a main air inlet pipe 5, a main air distribution ring 6, a cooling water inlet pipe 7 and a cooling water outlet pipe 8; the external spray pipe 10 comprises a ceramic gasket 11, a graphite spray pipe 12, a tungsten lining 13, an air cooling sleeve 14, a cooling gas inlet pipe 15, a cooling gas outlet pipe 16, a powder feeding pipe 17 and a thermocouple 18; the lance 1 and the outer lance 10 are connected in a pressure-tight manner by means of bolts on an air-cooled jacket 14.

Graphite spray tube 12, negative pole 2, positive pole 3 from preceding backward in proper order with the axle center arrangement, realize keeping apart and insulating through main gas distribution ring 6 of polytetrafluoroethylene between negative pole 2 and the positive pole 3, keep apart and insulating through boron nitride ceramic gasket 11 between graphite spray tube 12 and the negative pole 2, prevent that the negative pole arc root from transferring to the graphite spray tube on, and then ablating spray tube and pollution coating.

The outside of the cathode 2 and the anode 3 is provided with a water cooling tank, cooling water enters from a water inlet pipe 7, flows through the water cooling tank outside the anode 3 and the cathode 2 in sequence and then flows out from a water outlet pipe 8, and forced cooling of the cathode 2 and the anode 3 is realized.

A main gas distribution ring 6 is arranged between the cathode 2 and the anode 3, plasma forming gas enters from a main gas inlet pipe 5, flows through the main gas distribution ring 6 with a rotary gas distribution hole and then enters into an arc chamber channel, and an initial arc 9 between the cathode and the anode is stretched and prolonged by the gas flow with a rotary direction and is kept in a dynamic stable state.

A tungsten lining 13 is embedded in the graphite spray pipe 12, and the tungsten lining has a high melting point and good mechanical properties, so that the erosion and abrasion of powder to the spray pipe can be effectively reduced; the rear end of the nozzle, close to the cathode outlet, is provided with a powder feeding hole 19 and is communicated with a powder feeding pipe 17, and the powder is fed into a central jet flow high-temperature area in the nozzle along the powder feeding hole 19 by carrier gas.

The graphite spray pipe 12 is provided with a cooling groove on the outside, inert cooling gas with a certain flow controlled by a mass flow meter enters from a cooling gas inlet pipe 15 and flows out from a cooling gas outlet pipe 16 after flowing through the cooling groove, and therefore quantitative cooling and protection of the graphite spray pipe are achieved.

Counter bores are respectively arranged at two ends of the outer part of the graphite spray pipe 12, the distance between the bottom of each counter bore and a graphite spray pipe channel is 1-2mm, the temperature measuring end of a thermocouple is in contact with the bottom of each counter bore for measuring temperature, the flow of cooling gas outside the spray pipe is adjusted according to the power of a spray gun and the size of the spray pipe, and the temperature of the inner wall of the spray pipe is controlled within the range of 2000 ℃ and 2500 ℃ through real-time temperature measurement of the thermocouple; therefore, by reducing the temperature difference between the inner wall of the nozzle and the melted and gasified powder and using a larger plasma gas flow rate, the deposition and blockage of the melted and gasified powder on the hot wall of the nozzle can be effectively inhibited.

The front center through hole cathode 2 is connected with a power supply cathode, the rear cup-shaped anode 3 is connected with a power supply anode, and through the design of the reverse electrode structure, an electric arc can be stretched to the maximum extent on a two-electrode gun structure, so that a cathode arc root is easily stretched and fixed at a cathode outlet, a larger electric arc voltage is realized, and further, a larger spray gun power can be realized under a small current; therefore, the design can increase the temperature and enthalpy of the jet flow and simultaneously reduce electrode erosion, thereby prolonging the service life of the electrode and the spray gun.

The cathode 2 is made of a copper embedded tungsten lining, and the anode 3 is made of a copper embedded molybdenum lining, so that the ablation of the electrode and the pollution to a coating can be further reduced.

8 air holes with the diameter of 1-2mm are uniformly distributed on the main air distribution ring 6, the radial rotation angle of the air holes is 45 ℃, electric arcs can be effectively stabilized and arc roots can periodically rotate through rotary air inlet, and the arc roots are prevented from being continuously ablated at a certain point of an electrode.

The aperture of the powder feeding hole 19 is 1-2mm, and the distance between the outlet of the powder feeding hole and the cathode outlet is 2-5mm, so that powder can be fed into a central high-temperature area close to the cathode outlet of the spray gun; the distance between the outlet of the powder feeding hole and the outlet of the graphite spray pipe is 60-120 mm, so that the heating time of the powder in the high-temperature jet of the spray pipe can be greatly prolonged, the jet energy utilization rate is improved, and the powder is fully melted and gasified.

The central through hole of the graphite spray pipe 12 is in a straight cylinder shape, the inner diameter is 4-10mm, and the design of a cylindrical flow channel with relatively small diameter can effectively compress jet flow, improve jet flow temperature, and enable powder to be always in a high-temperature jet flow area in the process of entering the spray pipe and leaving the spray pipe.

The external cooling tank of the graphite nozzle 12 is cooled by inert gases such as nitrogen and argon, and the inert gases are used for cooling, so that the oxidation and consumption of graphite at high temperature can be prevented, and the service life of the graphite nozzle is greatly prolonged.

The thermal barrier coating with the columnar-like structure and the higher gas phase content and the thickness of 150-200 mu m is prepared by the embodiment under the ultra-low pressure environment, and the selected powder is 8YSZ (Y) with the D50=12 mu m₂O₃ZrO in an amount of 7 to 8%₂Powder) nano agglomerated powderAnd finally, the substrate is high-temperature-resistant 316L stainless steel, and the specific spraying working parameters are as follows:

current of the spray gun: 400A;

spray gun voltage: 125V;

power of the spray gun: 50 Kw;

length/diameter of the nozzle: 80/6 mm;

temperature of inner wall of spray pipe: 2000 ℃;

plasma gas flow (argon-hydrogen): 45/15L/min;

cooling gas flow rate (nitrogen): 30L/min;

powder feeding amount: 5 g/min;

spraying distance: 1100 mm;

matrix temperature: 900 ℃ and 1000 ℃;

ambient pressure: 100 Pa.