CN115896774A - Method for preparing niobium coating by cold spraying technology - Google Patents
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- CN115896774A CN115896774A CN202111119660.8A CN202111119660A CN115896774A CN 115896774 A CN115896774 A CN 115896774A CN 202111119660 A CN202111119660 A CN 202111119660A CN 115896774 A CN115896774 A CN 115896774A
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Abstract
The invention discloses a cold spraying method and a cold spraying device for preparing a niobium coating, and belongs to the technical field of cold spraying. The technological parameters for preparing the niobium coating are as follows: preheating carrier gas at 200-600 deg.c, spraying distance of 10-30 mm, spraying pressure of 1.5-3.0 MPa and powder feeding heating temperature of 0-300 deg.c; the cold spraying device comprises a control system, a powder feeder, a gas heater, a Lavel nozzle and a powder heater; one end of the gas heater is connected with the Lavel nozzle, the other end of the gas heater is connected with the powder feeder, one end of the powder feeder is connected with the control system, the other end of the powder feeder is connected with one end of the powder heater, and the other end of the powder heater is connected with the Lavel nozzle. The invention adopts cold spraying equipment which can heat the powder feeding powder to heat the niobium powder from the powder feeder, and combines specific process parameters to obtain the niobium coating which is tightly combined with the matrix and is compact.
Description
Technical Field
The invention relates to the technical field of cold spraying, in particular to a cold spraying method and a cold spraying device for preparing a niobium coating.
Background
(Niobium) is a metal element. The chemical symbol Nb, atomic number 41, atomic number 92.90638, belongs to group VB of the periodic system. Niobium is an off-white metal with a melting point of 2468 ℃, a boiling point of 4742 ℃ and a density of 8.57g/cm 3 . Niobium is a bright gray metal with paramagnetism belonging to group 5 of the periodic table. High purity niobium metal is more ductile but becomes harder as the impurity level increases. Niobium thermal neutron capture cross sectionIs very low and therefore of considerable use in the nuclear industry. It is envisaged that if a niobium coating is provided on the surface of carbon steel or other low cost ferrous products, both cost reduction and corrosion resistance can be achieved. There have been attempts by researchers to produce niobium coatings on steel articles using thermal spray techniques. Thermal spraying (including flame spraying, electric arc spraying, plasma spraying, detonation spraying, and high velocity fuel spraying (HVOF), etc.) has been widely used. They have the common feature that the spray powder is melted at a high temperature and is adhered to the surface of a workpiece as a molten drop to form a coating. Because certain oxidation inevitably exists in the preparation process, the components and the performance of the coating have certain gap compared with those of bulk pure niobium.
Lugscheideder et al performed low pressure plasma spraying of tantalum and niobium, respectively. The tantalum powder for spray coating has a particle size of 5-20 μm, is massive in shape, has oxygen and hydrogen contents of 1400ppm and 10ppm, and has a hardness of 220HV 0.025 . Different niobium powders were used for the spray coating, all of which had good flow properties, under a pressure of 150 mbar, with 28 l/min Ar and 7.5 l/min H 2 With a delivery of 21 g/min, a dense niobium coating was produced (Wangzhijun, low-pressure plasma spraying of rare metals, rare metals materials & engineering, 1989 (6): 56-60).
The electric spark deposition technology is a metal surface strengthening technology developed on the basis of the traditional technology, and has the advantages of simple equipment operation, high coating bonding strength, low heat input and the like, the process comprises the steps of utilizing pulse micro-arcs formed between an electrode and a metal base material to instantly release high-energy electric energy stored by a power supply at high frequency on the surfaces of the electrode and the metal base material so as to ionize air, instantly releasing the electrode material and the surface of the metal base material at high frequency so as to ionize air, melting the electrode material and the surface of the metal base material, mutually combining, reacting and rapidly cooling to form a metallurgically combined deposition layer (grouping, wangwang, 37021centi, research on the structure and the performance of the Nb coating formed by electric spark deposition on the surface of H13 steel, and the surface technology, 2019 (1): 285-290.
Cold spray coating (also called cold gas dynamic spray coating) is a novel spray coating technique in which metal particles are driven by compressed gas to collide with a substrate at a very high speed in a completely solid state, so that the particles are subjected to severe plastic deformation and deposited to form a coating. The cold spraying has the characteristic of solid deposition at low temperature, can obviously reduce or even completely eliminate adverse effects of oxidation, phase change, segregation, residual tensile stress, grain growth and the like in the traditional hot spraying, and is concerned by more and more in academia and industry.
In recent years, thermal spraying including electric arc spraying, supersonic spraying and high-energy micro-arc deposition have been reported to prepare niobium coatings, and the obtained products not only have relatively low cost, but also have the characteristics of niobium basically. In addition, the niobium coating is prepared by adopting a laser multi-pass lapping method in the early period, but the performance is relatively poor. Sundararajan and the like adopt a cold spraying technology to prepare SS niobium coatings, but the coating quality is not high, obvious holes exist at the interface of the coating and a substrate, and the coating is not compact; they heat-treated the cold-sprayed niobium coatings at 400 deg.c, 800 deg.c and 1100 deg.c in order to increase the compactness of the coatings, but the effect was not significant. In addition, no other reports on the cold spray technique for producing niobium coatings have been found.
Disclosure of Invention
The invention aims to provide a method and equipment for preparing a niobium coating by using a cold spraying technology, which solve the problem of poor coating quality in the process of preparing the niobium coating by using the existing hot spraying technology, and simultaneously integrate the low cost of common carbon steel and iron products and the high performance of niobium to achieve the purpose of reducing the cost on the premise of ensuring the performance.
In order to achieve the purpose, the invention adopts the technical scheme that:
A cold spraying method for preparing a niobium coating is to prepare the niobium coating by adopting a cold spraying device, and the technological parameters are as follows: the heating temperature of carrier gas is 200-600 ℃, the spraying distance is 10-30 mm, the spraying pressure is 1.5-3.0 MPa, and the powder feeding heating temperature is 0-300 ℃.
The spraying material is niobium powder with-400 to-500 meshes.
The spraying substrate material is carbon steel, stainless steel, high-temperature alloy, titanium alloy or cast iron.
Before spraying, the substrate is degreased by acetone and ethanol, and then is subjected to sand blasting and oxide layer removing treatment by using 240-mesh white corundum.
A device for preparing a niobium coating by a cold spraying technology comprises a powder feeder and a Lavel nozzle, wherein a powder heater is additionally arranged between the powder feeder and the Lavel nozzle and used for heating powder sent by the powder feeder.
The device also comprises an air compressor, a control system and a gas heater, wherein compressed air output by the air compressor is divided into two paths, one path of compressed air is heated by the gas heater and then is conveyed to the Lavel nozzle, and the other path of compressed air is conveyed to the powder feeder; the powder feeder is connected with the control system at the same time.
And the joint of the gas heater and the Lavel nozzle and the joint of the powder heater and the Lavel nozzle are respectively provided with a temperature sensor, and the temperature sensors respectively feed back the temperatures heated by the gas heater and the powder heater to the control system.
The power of the powder heater and the power of the gas heater are adjusted through a control system.
The invention aims to prepare a niobium coating by adopting a cold spraying process, and the coating with less defects and high quality can be obtained by adjusting the temperature of powder feeding powder, and a whole set of reasonable process parameters needs to be formulated. Although the carrier gas is heated to increase the velocity of the particles and thus increase the kinetic energy of the particles so as to be more easily combined with the matrix, the excessive temperature of the carrier gas causes the growth of crystal grains inside the powder particles and deteriorates the performance of the sprayed particles; at the same time, the spray particles will melt in the spray gun and clog the spray gun. Of course, the gas temperature cannot be too low, otherwise the acceleration of the sprayed particles is not favoured. In the case of a reduced gas temperature, the gas pressure needs to be increased to deposit the sprayed particles, which is limited by the capacity of the apparatus. Therefore, under the condition that the temperature of the carrier gas and the pressure of the gas cannot be further improved, the cold spraying equipment is improved, the powder feeding heater is added, the sprayed powder is directly heated, the plastic deformation capacity of the sprayed powder is improved, and the optimization of the cold spraying process of a specific material is very important. The powder feeding heater is added, and the powder is directly heated by using a heat source in the cold spraying process, so that the compactness of the coating can be greatly improved, the defects of holes and the like in the coating are effectively reduced, and the quality of the coating is obviously improved. This is mainly because heating the powder directly favors softening of the powder over heating by means of a carrier gas, increasing its tendency to plastic deformation and improving the quality of the coating.
The powder feeding heater is added on the traditional cold spraying equipment, the working principle of the powder feeding heater is the same as that of the traditional cold spraying equipment, the improved cold spraying equipment is still based on the aerodynamic principle during working, and high-pressure gas (He and N) is utilized 2 Mixed gas or air) to carry powder particles through a convergent-divergent tube to generate supersonic two-phase flow, and the supersonic two-phase flow impacts a substrate in a complete solid state and is deposited on the surface of the substrate through large plastic flow deformation to form a coating. The spray gun is designed by utilizing the Lavel nozzle principle. In the spraying process, when the speed of the particles exceeds the corresponding critical speed, the particles are collided and then deposited on the surface of the substrate to form a coating; otherwise, erosion will occur.
The invention has the following beneficial effects:
1. the invention adopts a specific cold spraying process to prepare the niobium coating with excellent performance, and the coating with different performances (such as compactness) can be obtained by adjusting the heating temperature of the powder in the cold spraying process.
2. The cold spraying equipment used in the invention utilizes compressed air to send powder and accelerate the powder, and the driving gas and the carrier gas are provided by an air compressor with the maximum pressure of 3.5 MPa. The novel cold spraying equipment has two heaters: one part is used for heating carrier gas, and the functions of preheating powder and accelerating the expansion of the carrier gas can be achieved; the other part is positioned between the powder feeder and the Lavel nozzle, and directly heats the powder sent by the powder feeder to play the roles of softening the powder and improving the plastic deformation capacity of the powder, and also indirectly heats the carrier gas to promote the gas expansion and accelerate the powder. The spray gun is vertically fixed on the bracket; the sample moves relative to the spray gun on an X-Y two-dimensional moving platform.
3. The temperature of the cold spraying process is far lower than the melting point of the powder, and one third of the melting point is generally taken as the temperature for heating the carrier gas. After the powder feeding heater is added, the powder sprayed out of the powder feeder can be instantly heated to a set temperature in the spraying process, and the temperature of the powder is generally not higher than the temperature heated by the carrier gas. The temperature sensor is arranged on the equipment, so that the temperatures of carrier gas heating and powder feeding heating can be respectively fed back to the controller, and real-time monitoring and regulation can be realized.
4. The invention adds the powder heater by improving the cold spraying equipment, heats the niobium powder from the powder feeder to soften the powder and increase the plastic deformation capability of the niobium powder, obtains the high-quality niobium coating which is tightly combined with the matrix and compact per se, and can obtain the high-quality coating by adopting the cold spraying one step by the powder feeding and heating method, thereby omitting the subsequent heat treatment, saving the working procedure and reducing the cost, and having wide application prospect.
Drawings
FIG. 1 is a schematic view of a cold spray apparatus according to the present invention; in the figure: 1-a control system, 2-an air compressor, 3-a powder feeder, 4-a gas heater, 5-a powder heater, 6-de Lavel spray gun and 7-a substrate.
Detailed Description
As shown in figure 1, the invention adds a powder heater on the basis of the traditional cold spraying equipment (application number: 200410034941.3), and then prepares the high-quality niobium coating by optimizing the process parameters. The structure of the cold spraying device is shown in figure 1, and the cold spraying device comprises a control system 1, an air compressor 2, a powder feeder 3, a gas heater 4, a Lavel nozzle 6 and a powder heater 5; the compressed air output by the air compressor 2 is divided into two paths, one path is heated by the gas heater 4 and then conveyed to the Lavel nozzle 6, and the other path is conveyed to the powder feeder 3 for feeding powder; and a powder heater 5 is arranged between the powder feeder 3 and the level nozzle 6, and can be used for heating the niobium powder sent out by the powder feeder 3 to soften the niobium powder and enable the niobium powder to be easy to plastically deform, and after the niobium powder reaches the de level spray gun, the scaling process is more beneficial to forming a coating with good combination.
The Lavel nozzle 6 is vertically fixed on the bracket; the sample (substrate 7) is moved relative to the spray gun on an X-Y two-dimensional moving platform.
Temperature sensors are respectively arranged at the joint of the gas heater 2 and the Lavel nozzle 6 and the joint of the powder heater 5 and the Lavel nozzle 6; the power of the powder heater 5 and the gas heater 2 and the pressure of the compressed gas source are regulated by the control system 1; by adjusting the power of the powder heater, the temperature of the niobium powder can be controlled within the range of room temperature to 300 ℃, so that the powder is softened, and the flowability of the powder is not influenced.
The quality of niobium coatings produced by using a cold spray apparatus of the present invention with an additional powder feeding heater and a conventional cold spray apparatus (application No.: 200410034941.3) will be described below by way of specific examples.
Example 1
The niobium coating is prepared by using cold spraying equipment with a powder feeding heater, wherein the spraying material is niobium powder with the granularity of-400 to-500 meshes, and the spraying base material is 45# steel. The specific process parameters are as follows: the carrier gas pressure is 2.0MPa, the carrier gas heating temperature is 500 ℃, the powder feeding heating temperature is 270 ℃, and the spraying distance is 20mm.
Example 2
The niobium coating is prepared by adopting the cold spraying equipment with the powder feeding heater, the spraying material is niobium powder with the granularity of-400 to-500 meshes, and the spraying substrate is 45# steel. The specific process parameters are as follows: the carrier gas pressure is 2.0MPa, the carrier gas heating temperature is 600 ℃, the powder feeding heating temperature is 200 ℃, and the spraying distance is 20mm.
Example 3
The niobium coating is prepared by using cold spraying equipment with a powder feeding heater, wherein the spraying material is niobium powder with the granularity of-400 to-500 meshes, and the spraying base material is 45# steel. The specific process parameters are as follows: the carrier gas pressure is 2.0MPa, the carrier gas heating temperature is 550 ℃, the powder feeding heating temperature is 200 ℃, and the spraying distance is 20mm.
Example 4
The niobium coating is prepared by using the cold spraying equipment with the powder feeding heater, the spraying material is niobium powder with the granularity of 400-500 meshes, and the spraying base material is 45# steel. The specific process parameters are as follows: the carrier gas pressure is 2.0MPa, the carrier gas heating temperature is 600 ℃, the powder feeding heating temperature is 220 ℃, and the spraying distance is 20mm.
Claims (8)
1. A cold spraying method for preparing a niobium coating is characterized by comprising the following steps: the method adopts a cold spraying device to prepare the niobium coating, and the technological parameters are as follows: the heating temperature of carrier gas is 200-600 ℃, the spraying distance is 10-30 mm, the spraying pressure is 1.5-3.0 MPa, and the powder feeding heating temperature is 0-300 ℃.
2. The cold spray method for making niobium coatings of claim 1, characterized in that: the spraying material is niobium powder with-400 to-500 meshes.
3. The cold spray method for making niobium coatings of claim 1, characterized in that: the spraying substrate material is carbon steel, stainless steel, high-temperature alloy, titanium alloy or cast iron.
4. The cold spray method for making niobium coatings of claim 1, characterized in that: before spraying, the substrate is degreased by acetone and ethanol, and then is subjected to sand blasting and oxide layer removing treatment by using 240-mesh white corundum.
5. The cold spraying device for preparing the niobium coating is characterized in that: the device comprises a powder feeder and a Lavel nozzle, wherein a powder heater is additionally arranged between the powder feeder and the Lavel nozzle and used for heating powder sent out by the powder feeder.
6. The cold spray apparatus for producing a niobium coating, as claimed in claim 5, wherein: the device also comprises an air compressor, a control system and a gas heater, wherein compressed air output by the air compressor is divided into two paths, one path of compressed air is heated by the gas heater and then is conveyed to the Lavel nozzle, and the other path of compressed air is conveyed to the powder feeder; the powder feeder is simultaneously connected with a control system.
7. The cold spray apparatus for producing a niobium coating, as claimed in claim 5, wherein: and the connection part of the gas heater and the Lavel nozzle and the connection part of the powder heater and the Lavel nozzle are respectively provided with a temperature sensor, and the temperature sensors respectively feed back the heating temperatures of the gas heater and the powder heater to the control system.
8. The cold spray apparatus for producing niobium coating according to claim 7, wherein: the power of the powder heater and the gas heater is adjusted by a control system.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN202111119660.8A CN115896774A (en) | 2021-09-24 | 2021-09-24 | Method for preparing niobium coating by cold spraying technology |
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| CN202111119660.8A CN115896774A (en) | 2021-09-24 | 2021-09-24 | Method for preparing niobium coating by cold spraying technology |
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