Method for improving the quality of the inner surface of an internal flow channel part

Abstract

The application relates to the field of additive manufacturing technology, and provides an improvement method for the inner surface quality of an inner runner part, which comprises the following steps: S1) preparing the inner runner part by using an additive manufacturing method; S2) passing liquid paraffin through the inner runner of the inner runner part, and then passing into liquid nitrogen; S3) arranging a conductive metal material outside one end of the inner runner part, and grounding the conductive metal material; S4) continuously spraying metal powder into the inner runner of the inner runner part from the end of the inner runner which is not arranged with the conductive metal material by using an electrostatic spraying device connected with high-voltage negative electricity; after a stable powder flow is formed, heating the inner runner part; S5) removing the conductive metal material, simultaneously stopping the electrostatic spraying device and grounding the inner runner part, and then removing the wire for grounding the inner runner part; and S6) heating the inner runner part. The improvement method provided by the application can improve the surface quality of the inner runner of the inner runner part, and solve the problems of poor inner runner surface quality and large roughness of the inner runner part.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for improving the inner surface quality of internal flow channel parts. Background Technology

[0002] Additive manufacturing technology uses the three-dimensional model data of a part to discretize the model into a series of two-dimensional slices, and then builds the part by stacking material layer by layer. Additive manufacturing technology can directly manufacture parts without the need for molds, significantly shortening the production cycle and improving production efficiency. It is especially suitable for manufacturing complex structures, small batches, and customized parts. Additive manufacturing technology is also commonly used to prepare internal flow channel parts with internal channel structures.

[0003] In additive manufacturing, the melting and solidification of each layer creates steps between them. These steps accumulate on the part surface, increasing surface roughness. Since internal flow channels involve fluid flow, poor surface roughness increases fluid flow resistance, reduces flow efficiency, and affects the part's functionality. Furthermore, poor surface roughness in internal flow channels can also lead to stress concentration, reducing mechanical properties.

[0004] Regarding surface finishing techniques for parts, most existing technologies are designed and developed for the outer surfaces of parts. Traditional surface processing methods struggle to reach the inner flow channels of additively manufactured parts. Even when they can reach them, the size and shape of the processing tools are limited, hindering effective processing. Therefore, there is a lack of effective solutions for the specific requirements of the inner surfaces of additively manufactured parts with internal flow channels.

[0005] Therefore, there is an urgent need to develop a treatment method to improve the surface quality of internal flow channel parts in additive manufacturing, which can not only improve the surface quality of internal flow channel parts, but also promote the wider engineering application of additive manufacturing technology. Summary of the Invention

[0006] The technical problem solved by this invention is to provide a method for improving the surface quality of an inner flow channel component. The method provided in this application can improve the roughness of the inner surface of the inner flow channel component.

[0007] In view of this, this application provides a method for improving the inner surface quality of an internal flow channel component, comprising the following steps:

[0008] S1) The internal flow channel parts are prepared using additive manufacturing methods;

[0009] S2) Liquid paraffin is passed through the inner channel of the inner channel component, and then liquid nitrogen is introduced into the inner channel of the inner channel component to form a paraffin film on the surface of the inner channel of the inner channel component.

[0010] S3) A conductive metal material is disposed on the outside of one end of the inner flow channel component obtained in step S2), the shape of the conductive metal material is the same as the shape of the corresponding end of the inner flow channel component, and the conductive metal material is grounded;

[0011] S4) Using an electrostatic spraying device connected to a high voltage negative voltage, metal powder is continuously sprayed into one end of the inner flow channel of the inner flow channel part obtained in step S2) where no conductive metal material is provided.

[0012] After the metal powder forms a stable powder flow in the inner channel of the inner channel component, the inner channel component is heated to cause the paraffin film to evaporate.

[0013] S5) Remove the conductive metal material, stop the electrostatic spraying device and ground the inner flow channel part, so that the metal powder is deposited on the inner flow channel surface of the inner flow channel part, and then remove the grounding wire of the inner flow channel part.

[0014] S6) Heat the inner flow channel part obtained in step S5).

[0015] In some specific embodiments, step S6) is followed by:

[0016] S7) Inject high-pressure gas into the inner flow channel of the inner flow channel component obtained in step S6).

[0017] In some specific embodiments, step S7) is followed by:

[0018] Repeat steps S2) to S7) 1 to 3 times in sequence.

[0019] In some specific embodiments, the metal powder in step S4) is made of the same material as the inner flow channel component; during the repeated 1 to 3 times, the metal powder is made of the same or different material as the inner flow channel component; and / or, the particle size of the metal powder is 5 to 20 μm.

[0020] In some specific embodiments, in step S3), the conductive metal material is a copper block, and / or the distance between the conductive metal material and the end near the inner flow channel component is 10~40mm.

[0021] In some specific embodiments, in step S4), the distance between the electrostatic spraying device and the end of the inner flow channel part that is not provided with conductive metal material is 5~10mm; and / or, in step S4), the heating is induction heating or a moving heating method of ceramic heating plate, and the heating temperature is greater than the boiling point of the liquid paraffin.

[0022] In some specific embodiments, in step S6), the heating method is as follows:

[0023] First, heat the inner flow channel part obtained in step S5) to 550~600℃, hold it at that temperature for 30~60min, and then heat it to 0.7~0.8 times the melting point of the metal powder, and hold it at that temperature for 120~180min.

[0024] In some specific embodiments, in step S7), the high-pressure gas is air or argon, and / or the flow rate of the high-pressure gas is 4~7 L / min.

[0025] In some specific embodiments, the material of the inner flow channel component includes GH3536 high-temperature alloy, TC4 titanium alloy, and GH5188 high-temperature alloy.

[0026] In some specific embodiments, step S1) specifically includes:

[0027] Establish CAD digital models of internal flow channel parts;

[0028] Metal powder is placed in the powder chamber of an additive manufacturing equipment, and internal flow channel parts are prepared by additive manufacturing based on the CAD digital model.

[0029] This application provides a method for improving the surface quality of an inner flow channel component. First, the inner flow channel component is prepared by additive manufacturing. Then, metal powder is sprayed onto the inner surface of the inner flow channel component using electrostatic spraying. At the same time, the movement direction of the metal powder is controlled by changing the direction of the electric field, so that the originally uneven surface of the inner surface of the inner flow channel component, especially the concave area, forms a dense metal layer with good bonding strength, thereby improving the roughness of the inner surface of the inner flow channel component and improving the surface quality of the inner flow channel component. Attached Figure Description

[0030] Figure 1 This is a schematic flowchart of the method for improving the inner surface quality of internal flow channel parts provided by the present invention. Detailed Implementation

[0031] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0032] In view of the problem that the surface quality of the inner flow channel of internal flow channel parts needs to be improved in the prior art, this application provides a method for improving the surface quality of the inner flow channel parts, and the process diagram is shown below. Figure 1As shown, the internal flow channel part is first prepared using additive manufacturing. Then, electrostatic spraying is used to control the movement direction of metal powder by changing the electric field direction, resulting in a dense metal material layer with good bonding strength on the surface of the internal flow channel, especially in the concave area, thus improving the surface quality of the internal flow channel. Specifically, this invention discloses a method for improving the surface quality of an internal flow channel part, including the following steps:

[0033] S1) The internal flow channel parts are prepared using additive manufacturing methods;

[0034] S2) Liquid paraffin is passed through the inner channel of the inner channel component, and then liquid nitrogen is introduced into the inner channel of the inner channel component to form a paraffin film on the surface of the inner channel of the inner channel component.

[0035] S3) A conductive metal material is disposed on the outside of one end of the inner flow channel component obtained in step S2), the shape of the conductive metal material is the same as the shape of the corresponding end of the inner flow channel component, and the conductive metal material is grounded;

[0036] S4) Using an electrostatic spraying device connected to a high voltage negative voltage, metal powder is continuously sprayed into one end of the inner flow channel of the inner flow channel part obtained in step S2) where no conductive metal material is provided.

[0037] After the metal powder forms a stable powder flow in the inner channel of the inner channel component, the inner channel component is heated to cause the paraffin film to evaporate.

[0038] S5) Remove the conductive metal material, stop the electrostatic spraying device and ground the inner flow channel part, so that the metal powder is deposited on the inner flow channel surface of the inner flow channel part, and then remove the grounding wire of the inner flow channel part.

[0039] S6) Heat the inner flow channel part obtained in step S5).

[0040] In the method for improving the inner surface quality of internal flow channel parts, this application first uses an additive manufacturing method to prepare the internal flow channel parts, wherein the additive manufacturing method specifically includes:

[0041] A CAD digital model of the internal flow channel component is established based on its dimensions. Metal powder is placed into the hopper of the additive manufacturing equipment according to the material of the internal flow channel component. The internal flow channel component is then prepared using additive manufacturing technology based on the CAD digital model.

[0042] In the above-described process of preparing internal flow channel parts using additive manufacturing, the metal powder can be a single metal powder or a powder of multiple metals, i.e., an alloy powder. For alloy powders, this application does not have a particular limitation on their composition; the metal powder can be selected according to the material of the internal flow channel part. For example, if the internal flow channel part is a GH3536 high-temperature alloy vortex generator, then the metal powder is GH3536 high-temperature alloy powder; if the internal flow channel part is a TC titanium alloy ventilation pipe, then the metal powder is TC titanium alloy powder; if the internal flow channel part is a GH5188 high-temperature alloy nozzle, then the metal powder is GH5188 high-temperature alloy. The additive manufacturing method is performed according to methods well known to those skilled in the art, and this application does not impose any particular limitations on it. The internal flow channel of the internal flow channel part can be a regular-shaped internal flow channel or an irregular-shaped internal flow channel; the improvement methods provided in this application are applicable to both.

[0043] After the inner flow channel component is prepared, in step S2), liquid paraffin is passed through the inner flow channel of the component, and then liquid nitrogen is introduced into the inner flow channel to form a paraffin film on the surface of the inner flow channel. During this process, the liquid paraffin enters from one end of the inner flow channel and flows out from the other end. The fluidity of the liquid paraffin allows it to fully cover the surface of the inner flow channel in a liquid state, which is a prerequisite for forming the paraffin film covering the inner flow channel surface. After the liquid nitrogen is introduced, a paraffin film is formed on the surface of the inner flow channel. This paraffin film acts as an insulating layer on the surface of the inner flow channel, preventing metal powder from accumulating at the inlet of the inner flow channel when it first enters, thus preventing uneven distribution of the metal powder, failure to form a stable powder flow, and affecting the heating and sintering effect of the metal powder. Therefore, it is beneficial for forming a metal powder flow within the inner flow channel.

[0044] In step S3), a conductive metal material is placed on the outside of one end of the inner flow channel component. The shape of the conductive metal material is the same as that of the inner flow channel component at the opposite end, and the conductive metal material is grounded. During this process, the grounded conductive metal material forms a positive electrode, while the metal powder sprayed by the electrostatic spraying device carries a negative charge. This arrangement is to allow the metal powder to move from the electrostatic spraying device towards the conductive metal material, thereby facilitating the formation of a metal powder flow in the inner flow channel. In this application, the conductive metal material is selected from copper blocks, and the distance between the copper block and the port near the inner flow channel is 10mm to 40mm. If the distance is less than 10mm, the space between the copper block and the inner flow channel component is too small, making positioning difficult and increasing operational complexity. If the distance is greater than 40mm, the metal powder flow cannot be completely adsorbed on the surface of the copper block, and there is a possibility that the metal powder will splash outside the copper block, resulting in waste of metal powder. Therefore, the distance between the copper block and the port near the inner flow channel of the component is selected to be between 10mm and 40mm, specifically, the distance between the copper block and the port near the inner flow channel of the component is 20mm to 30mm. The shape and size of the port of the inner flow channel component near the copper block end are the same as those of the copper block. This setting can control the diameter of the metal powder flow to be similar to the diameter of the inner flow channel, which is beneficial to forming a stable flow of metal powder in the inner flow channel.

[0045] In step S4), metal powder is first continuously sprayed into the inner channel of the part without conductive metal material using an electrostatic spraying device connected to a high-voltage negative electrode. During this process, the distance between the electrostatic spraying device and the port of the inner channel is 5mm to 10mm. If the distance is less than 5mm, the space between the electrostatic spraying device and the part is too small, making positioning difficult and increasing operational complexity. If the distance is greater than 10mm, the metal powder flow cannot fully enter the inner channel, and there is a possibility of metal powder splashing onto the outside of the part, resulting in waste. Therefore, the distance between the electrostatic spraying device and the port of the inner channel is selected to be between 5mm and 10mm. The chemical composition of the metal powder is the same as the material of the inner channel part, and the particle size of the metal powder is 5μm to 20μm. The introduction of the metal powder ensures that, through the subsequent heating and sintering process, a dense and well-bonded metal coating is formed on the original uneven surface of the inner channel, especially in the recessed areas, thereby improving surface roughness by filling the recessed areas. The metal powder and the inner flow channel component can be made of the same or different materials. Using metal powder with the same chemical composition as the component ensures optimal bonding strength and avoids potential metallurgical incompatibility issues at the interface of dissimilar materials. If the particle size of the metal powder is greater than 20 μm, it is prone to detaching from the inner flow channel surface under its own gravity after electrostatic treatment, resulting in poor bonding. Furthermore, excessively large particle sizes make it difficult to fill the recessed areas on the inner flow channel surface, limiting its effectiveness in improving surface roughness. In addition, excessively large particle sizes result in poor sintering during subsequent heating of the inner flow channel component, leading to more porosity in the sintered metal, which not only affects the bonding strength with the inner flow channel surface but also fails to achieve optimal surface roughness improvement. If the particle size of the metal powder is less than 5 μm, it is prone to agglomeration, resulting in poor flowability and difficulty in forming a stable powder flow. Therefore, the particle size of the metal powder used is between 5 μm and 20 μm.

[0046] As the electrostatic spraying device continuously sprays metal powder, once a stable powder flow is formed within the inner channel of the inner flow channel component, the component is heated to evaporate the paraffin film on the inner channel surface. During this process, visual observation shows that the diameter and flow rate of the powder flow remain constant, indicating a stable powder flow. Heating removes the paraffin film, allowing the metal powder to cover the surface of the inner channel in step S5). If the paraffin film remains between the inner channel surface and the metal powder, it will worsen the bonding strength between them. The inner channel component is heated using induction heating, ceramic heating plates, or other movable heating methods. Movable heating is used because the electrostatic spraying device is still spraying powder, making it difficult to heat in a heat treatment furnace; movable heating is simpler and more operable. The heating temperature is higher than the boiling point of the liquid paraffin to ensure sufficient evaporation of the paraffin film and prevent residual paraffin from forming impurities on the metal and inner channel surface after sintering, thus affecting the bonding strength.

[0047] In step S5), the conductive metal material is first removed, and the electrostatic spraying device is stopped while the inner flow channel component is grounded. In this step, by removing the externally placed conductive metal material and grounding the inner flow channel component to form a positive electrode, the direction of metal powder movement is changed. This causes the metal powder, which was originally moving within the inner flow channel, to adhere to the surface of the inner flow channel, forming a uniform metal powder layer covering the surface. At this point, the deposition of the metal powder layer on the inner surface of the inner flow channel component is complete. Then, the grounding wire of the inner flow channel component is removed, i.e., the external device of the inner flow channel component is removed, in preparation for subsequent steps.

[0048] In step S6), the inner flow channel part obtained above is heated; during the heating process, the inner flow channel part is first heated from room temperature to 550℃~600℃, held for 30min~60min, then heated to 0.7~0.8 times the melting point of the metal powder, held for 120min~180min, and finally cooled to room temperature with the furnace; the above heating is preferably carried out in a heat treatment furnace. In the above heating process, the temperature is first raised from room temperature to 550℃~600℃ and held for 30min~60min to allow residual paraffin wax to fully volatilize and avoid forming defects and impurities in the sintered metal. If the heating temperature is less than 550℃, the paraffin wax volatilizes slowly and inefficiently, and the volatilization is insufficient. If the heating temperature is greater than 600℃, the paraffin wax volatilizes too quickly, easily forming pore defects, which will damage the density of the sintered metal. Therefore, the heating temperature is selected between 550℃~600℃. If the holding time is less than 30min, the paraffin wax volatilizes insufficiently. If the holding time is greater than 60min, it cannot significantly increase the volatilization effect of paraffin wax, but instead prolongs the processing time and reduces production efficiency. Therefore, the holding time is selected between 30min~60min. Specifically, the heating temperature is 570~590℃, and the holding time is 40~50min. After the first heat treatment, the metal powder is heated to 0.7-0.8 times its melting point and held for 120-180 minutes to allow it to sinter into a dense metal layer. If the heating temperature is less than 0.7-0.8 times the melting point, the growth of the metal powder is insufficient, resulting in an insignificant sintering effect. If the heating temperature is greater than 0.7-0.8 times the melting point, the grains in the sintered metal layer will grow rapidly, leading to a deterioration in the metal layer's properties. Therefore, the heating temperature is selected to be 0.7-0.8 times the melting point. If the holding time is less than 120 minutes, the sintering effect of the metal powder is insignificant. If the holding time is greater than 180 minutes, it will not significantly increase the sintering effect but will instead prolong the processing time and reduce production efficiency. Therefore, the holding time is selected to be between 120-180 minutes. Specifically, the heating temperature is 0.8 times the melting point of the metal powder, and the holding time is 130-150 minutes. After heating, the furnace is cooled to room temperature to achieve a slow cooling effect, allowing thermal stress to be released slowly and preventing the sintered metal from cracking or peeling.

[0049] Furthermore, this application injects high-pressure gas into the inner channel of the aforementioned inner channel component to further clean any unsintered metal powder, impurities, and other excess materials that may remain inside the inner channel component. The high-pressure gas is a commonly used industrial compressed gas such as air or argon, and its flow rate is 4 L / min to 7 L / min. If the flow rate is less than 4 L / min, the airflow is insufficient, resulting in poor cleaning. If the flow rate is greater than 7 L / min, the gas consumption increases, but this does not significantly improve the cleaning effect; instead, it increases the gas usage cost. Therefore, the flow rate of the high-pressure gas is selected between 4 L / min and 7 L / min, specifically 5 to 6 L / min. Commonly used industrial compressed gases such as air and argon are selected as the high-pressure gas.

[0050] Furthermore, to fully improve the surface quality of the inner flow channel parts, steps S2) to S8) are repeated 1 to 3 times, that is, after completing the above steps, the above steps are repeated 1, 2, or 3 times. If the number of repetitions is less than 1, the best effect cannot be achieved, and some areas may not be completely processed. If the number of repetitions is more than 3, the processing effect cannot be significantly improved, but rather the time is prolonged and the production efficiency is reduced. During the above repetition process, the metal powder can be the same as or different from the material of the inner flow channel parts.

[0051] This application provides a method for improving the surface quality of an internal flow channel component. By changing the direction of the electric field to control the movement direction of metal powder, a dense, well-bonded metal layer is formed in the recessed areas of the original uneven surface of the internal flow channel, thereby improving surface roughness by filling the recessed areas. This invention offers better accessibility and is suitable for improving the surface quality of internal flow channels in additive manufacturing.

[0052] To further understand the present invention, the method for improving the inner surface quality of internal flow channel parts provided by the present invention will be described in detail below with reference to embodiments. The scope of protection of the present invention is not limited by the following embodiments.

[0053] Example 1

[0054] This embodiment provides a method for improving the inner surface quality of a GH3536 high-temperature alloy eddy current generator, including the following steps:

[0055] 1) Establish a CAD digital model of the GH3536 high-temperature alloy eddy current generator;

[0056] 2) Place GH3536 high-temperature alloy powder into the powder chamber of the laser selective melting additive manufacturing equipment, and complete the laser selective melting additive manufacturing of the eddy current generator based on the established CAD digital model;

[0057] 3) Pour the liquid paraffin into one end of the flow channel inside the vortex generator and let it flow out from the other end;

[0058] 4) Introduce liquid nitrogen into the inner channel of the vortex generator to solidify the paraffin on the surface of the inner channel into a paraffin film.

[0059] 5) A copper block is placed outside one end of the inner channel of the vortex generator. The copper block is grounded through a wire. The distance between the copper block and the port of the inner channel of the vortex generator is 40mm. The shape of the opposite face of the copper block and the port of the inner channel is circular with a diameter of 35mm.

[0060] 6) Using an electrostatic spraying device, spray GH3536 high-temperature alloy powder with a particle size between 5μm and 20μm from the end of the eddy current channel without copper blocks. Connect the spraying device to a high voltage negative power supply. The distance between the electrostatic spraying device and the port of the eddy current channel is 10mm.

[0061] 7) After the GH3536 high-temperature alloy powder forms a stable powder flow in the inner channel of the vortex generator, use a ceramic heating plate to heat the vortex generator to 400°C to make the paraffin film on the surface of the inner channel evaporate.

[0062] 8) Remove the external copper block and ground the eddy current generator through a wire, and stop using the electrostatic spraying device to spray powder.

[0063] 9) Remove the grounding wire from the eddy current generator;

[0064] 10) Place the vortex generator into the heat treatment furnace and first heat it from room temperature to 550°C, hold it for 30 minutes, then heat it to 1036°C, hold it for 120 minutes, and finally cool it to room temperature with the furnace.

[0065] 11) Inject high-pressure air into the flow channel inside the vortex generator at a flow rate of 4 L / min for 1 min.

[0066] 12) Repeat steps 3) to 11) once.

[0067] The surface roughness of the inner channel of the additively manufactured vortex generator was measured using a roughness tester. The results showed that the surface roughness of the inner channel of the vortex generator was Ra6.3μm, which was significantly improved compared with the surface roughness Ra12.6μm before treatment using the method of the present invention.

[0068] Example 2

[0069] This embodiment provides a method for improving the inner surface quality of TC4 titanium alloy ventilation pipes, including the following steps:

[0070] 1) Establish a CAD digital model of the TC4 titanium alloy ventilation duct;

[0071] 2) Place TC4 titanium alloy powder into the powder chamber of the laser selective melting additive manufacturing equipment, and complete the laser selective melting additive manufacturing of the ventilation duct based on the established CAD digital model;

[0072] 3) Pour the liquid paraffin into the ventilation duct from one end and let it flow out from the other end;

[0073] 4) Introduce liquid nitrogen into the flow channel of the ventilation duct to solidify the paraffin on the surface of the flow channel into a paraffin film;

[0074] 5) A copper block is installed on the outside of one end of the flow channel in the ventilation duct. The copper block is grounded through a wire. The distance between the copper block and the port of the flow channel in the ventilation duct is 20mm. The shape of the opposite face of the copper block and the port of the flow channel is circular with a diameter of 18mm.

[0075] 6) Using an electrostatic spraying device, spray TC4 titanium alloy powder with a particle size between 5μm and 20μm into the flow channel of the ventilation duct from the end without the copper block. The spraying device is connected to a high voltage negative power supply, and the distance between the electrostatic spraying device and the port of the flow channel in the ventilation duct is 8mm.

[0076] 7) After the TC4 titanium alloy powder forms a stable powder flow in the flow channel of the ventilation pipe, use an induction heating device to heat the ventilation pipe to 350°C, so that the paraffin film on the surface of the inner flow channel evaporates.

[0077] 8) Remove the external copper block and ground the ventilation pipe through a wire at the same time, and stop using the electrostatic spraying device to spray powder.

[0078] 9) Remove the grounding wire from the ventilation duct;

[0079] 10) Place the ventilation pipe into the heat treatment furnace and first heat it from room temperature to 570°C, hold it for 40 minutes, then heat it to 1232°C, hold it for 150 minutes, and finally cool it to room temperature with the furnace.

[0080] 11) Inject high-pressure air into the ventilation duct at a flow rate of 6 L / min for 2 min.

[0081] 12) Repeat steps 3) to 11) twice.

[0082] The surface roughness of the above-mentioned additively manufactured ventilation duct was measured using a roughness tester. The results showed that the surface roughness of the inner flow channel of the ventilation duct was Ra5.2 μm, which was significantly improved compared with the surface roughness Ra11.5 μm before treatment using the method of the present invention.

[0083] Example 3

[0084] This embodiment provides a method for improving the inner surface quality of a GH5188 high-temperature alloy nozzle, including the following steps:

[0085] 1) Establish a CAD digital model of the GH5188 high-temperature alloy nozzle;

[0086] 2) Place GH5188 high-temperature alloy powder into the powder chamber of the laser selective melting additive manufacturing equipment, and complete the laser selective melting additive manufacturing of the nozzle based on the established CAD digital model;

[0087] 3) Pour the liquid paraffin into the nozzle from one end of the flow channel and let it flow out from the other end;

[0088] 4) Introduce liquid nitrogen into the inner flow channel of the nozzle to solidify the paraffin on the surface of the inner flow channel into a paraffin film;

[0089] 5) A copper block is installed outside one end of the inner flow channel of the nozzle. The copper block is grounded through a wire. The distance between the copper block and the port of the inner flow channel of the nozzle is 10mm. The shape of the opposite face of the copper block and the port of the inner flow channel is circular with a diameter of 15mm.

[0090] 6) Using an electrostatic spraying device, spray GH5188 high-temperature alloy powder with a particle size between 5μm and 20μm from the end of the nozzle inner channel without copper block. Connect the spraying device to a high voltage negative power supply. The distance between the electrostatic spraying device and the nozzle inner channel port is 5mm.

[0091] 7) After the GH5188 high-temperature alloy powder forms a stable powder flow in the inner channel of the nozzle, use a ceramic heating plate to heat the nozzle to 360°C to make the paraffin film on the surface of the inner channel evaporate.

[0092] 8) Remove the external copper block and ground the nozzle through a wire at the same time, and stop using the electrostatic spraying device to spray powder.

[0093] 9) Remove the grounding wire from the nozzle;

[0094] 10) Place the nozzle into the heat treatment furnace and first heat it from room temperature to 600°C, hold it for 60 minutes, then heat it to 1040°C, hold it for 180 minutes, and finally cool it to room temperature with the furnace.

[0095] 11) Inject high-pressure air into the flow channel inside the nozzle at a flow rate of 7 L / min for 4 min.

[0096] 12) Repeat steps 3) to 11) 3 times.

[0097] The surface roughness of the inner flow channel of the above-mentioned additive manufacturing nozzle was measured using a roughness tester. The results showed that the surface roughness of the inner flow channel of the nozzle was Ra6.6μm, which was significantly improved compared with the surface roughness Ra12.3μm before treatment using the method of the present invention.

[0098] Example 4

[0099] This embodiment provides a method for improving the inner surface quality of GH3625 high-temperature alloy fuel injector rods, including the following steps:

[0100] 1) Establish a CAD digital model of the GH3625 high-temperature alloy fuel injector;

[0101] 2) Place GH3625 high-temperature alloy powder into the powder chamber of the laser selective melting additive manufacturing equipment, and complete the laser selective melting additive manufacturing of the fuel injector based on the established CAD digital model;

[0102] 3) Pour the liquid paraffin into one end of the fuel injector's inner channel and let it flow out from the other end;

[0103] 4) Introduce liquid nitrogen into the inner channel of the fuel injector to solidify the paraffin on the surface of the inner channel into a paraffin film.

[0104] 5) A copper block is installed outside one end of the inner flow channel of the fuel injector. The copper block is grounded through a wire. The distance between the copper block and the port of the inner flow channel of the fuel injector is 40mm. The shape of the opposite face of the copper block and the port of the inner flow channel is circular with a diameter of 20mm.

[0105] 6) Using an electrostatic spraying device, spray GH5188 high-temperature alloy powder with a particle size between 5μm and 20μm from the end of the fuel injector rod without the copper block. Connect the spraying device to a high voltage negative power supply. The distance between the electrostatic spraying device and the port of the nozzle's inner flow channel is 10mm.

[0106] 7) After the GH5188 high-temperature alloy powder forms a stable powder flow in the inner channel of the fuel injector, use a ceramic heating plate to heat the fuel injector to 380°C to make the paraffin film on the surface of the inner channel evaporate.

[0107] 8) Remove the external copper block and simultaneously ground the fuel injector via a wire, while stopping the use of the electrostatic spraying device to spray powder;

[0108] 9) Remove the grounding wire from the fuel injector;

[0109] 10) Place the fuel injection rod into the heat treatment furnace and first heat it from room temperature to 600°C, hold it for 60 minutes, then heat it to 910°C, hold it for 120 minutes, and finally cool it to room temperature with the furnace.

[0110] 11) Inject high-pressure air into the fuel injector's internal flow channel at a flow rate of 7 L / min for 6 minutes;

[0111] 12) Repeat steps 3) to 11) 3 times.

[0112] The surface roughness of the inner flow channel of the above-mentioned additively manufactured fuel injector was measured using a roughness tester. The results showed that the surface roughness of the inner flow channel of the fuel injector was Ra 6.3 μm, which is a significant improvement compared with the surface roughness before treatment using the method of this invention (surface roughness Ra 11.7 μm). Meanwhile, the maximum operating temperature of GH5188 high-temperature alloy is approximately 1000℃, while that of GH3625 high-temperature alloy is approximately 900℃. Treating the fuel injector with GH5188 high-temperature alloy powder not only improves the surface roughness of the inner flow channel but also leverages the high-temperature resistance of GH5188 high-temperature alloy, increasing the operating temperature of the part and further expanding its application scenarios.

[0113] The above description of the embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0114] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for improving the inner surface quality of an internal flow channel component, comprising the following steps: S1) The internal flow channel parts are prepared using additive manufacturing methods; S2) Liquid paraffin is passed through the inner channel of the inner channel component, and then liquid nitrogen is introduced into the inner channel of the inner channel component to form a paraffin film on the surface of the inner channel of the inner channel component. S3) A conductive metal material is disposed on the outside of one end of the inner flow channel component obtained in step S2), the shape of the conductive metal material is the same as the shape of the corresponding end of the inner flow channel component, and the conductive metal material is grounded; S4) Using an electrostatic spraying device connected to a high voltage negative voltage, metal powder is continuously sprayed into one end of the inner flow channel of the inner flow channel part obtained in step S2) where no conductive metal material is provided. After the metal powder forms a stable powder flow in the inner channel of the inner channel component, the inner channel component is heated to cause the paraffin film to evaporate. S5) Remove the conductive metal material, stop the electrostatic spraying device and ground the inner flow channel part, so that the metal powder is deposited on the inner flow channel surface of the inner flow channel part, and then remove the grounding wire of the inner flow channel part. S6) Heat the inner flow channel part obtained in step S5).

2. The improvement method according to claim 1, characterized in that, Step S6) is followed by: S7) Inject high-pressure gas into the inner flow channel of the inner flow channel component obtained in step S6).

3. The improved method according to claim 2, characterized in that, Step S7) is followed by: Repeat steps S2) to S7) 1 to 3 times in sequence.

4. The improved method according to claim 3, characterized in that, The metal powder in step S4) is made of the same material as the inner flow channel component; during the repeated 1 to 3 times, the metal powder is made of the same or different material as the inner flow channel component; and / or, the particle size of the metal powder is 5 to 20 μm.

5. The improved method according to claim 1 or 2, characterized in that, In step S3), the conductive metal material is a copper block, and / or the distance between the conductive metal material and the end near the inner flow channel component is 10~40mm.

6. The improved method according to claim 1 or 2, characterized in that, In step S4), the distance between the electrostatic spraying device and the end of the inner flow channel part that is not provided with conductive metal material is 5~10mm; and / or, in step S4), the heating is induction heating or a moving heating method of ceramic heating plate, and the heating temperature is greater than the boiling point of the liquid paraffin.

7. The improved method according to claim 1 or 2, characterized in that, In step S6), the heating method is as follows: First, heat the inner flow channel part obtained in step S5) to 550~600℃, hold it at that temperature for 30~60min, and then heat it to 0.7~0.8 times the melting point of the metal powder, and hold it at that temperature for 120~180min.

8. The improved method according to claim 2, characterized in that, In step S7), the high-pressure gas is air or argon, and / or the flow rate of the high-pressure gas is 4~7 L / min.

9. The improved method according to claim 1 or 2, characterized in that, The materials of the internal flow channel components include GH3536 high-temperature alloy, TC4 titanium alloy, and GH5188 high-temperature alloy.

10. The improved method according to claim 1 or 2, characterized in that, Step S1) specifically refers to: Establish CAD digital models of internal flow channel parts; Metal powder is placed in the powder chamber of an additive manufacturing equipment, and internal flow channel parts are prepared by additive manufacturing based on the CAD digital model.

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