Forming Method for Complex Components of Titanium Aluminum Alloy

Abstract

The present invention discloses a forming method for a complex component of a titanium-aluminum alloy, comprising the following steps: fabricating a graphite shell mold and a graphite pouring cup; respectively coating a high-temperature resistant ceramic coating on the inner cavity surfaces of the graphite shell mold and the graphite pouring cup; performing vacuum degassing treatment on the graphite shell mold and the graphite pouring cup; placing the titanium-aluminum alloy material into the graphite pouring cup above the graphite shell mold; placing the graphite shell mold, the graphite pouring cup, and the titanium-aluminum alloy material in the graphite pouring cup as a whole into a crucible in a vacuum induction melting furnace for gas washing treatment; starting the vacuum induction melting furnace for heating, and during the heating process, accompanied by the pouring and filling of the titanium-aluminum alloy material; taking out the graphite shell mold, the graphite pouring cup, and the complex component that has been poured and filled in the graphite shell mold as a whole from the vacuum induction melting furnace and performing annealing treatment; taking out the titanium-aluminum alloy complex component from the graphite shell mold. The present invention solves the technical barriers of high melting point and poor fluidity of the titanium-aluminum alloy, improves the superheat degree of the titanium-aluminum alloy liquid, and shortens the pouring time.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material forming, and particularly relates to a forming method for complex components of titanium aluminide alloy. Background Art

[0002] The long-term service temperature of TiAl intermetallic compound alloy is 650 - 800 °C. It combines the high-temperature performance advantages of nickel-based superalloys and the light weight advantages of titanium alloys, and is one of the most promising lightweight high-temperature structural materials at present. Precision casting technology can achieve the integrated forming of complex components, reduce connections, improve the stiffness of the overall structure, and meet the needs of the integrated forming of complex components. Therefore, the development of TiAl alloy and its precision casting technology is an important technical approach to meet the requirements of high-temperature resistance, weight reduction, and integrated forming of complex components such as the combustion chamber of high-performance aeroengines.

[0003] The casting process is a relatively conventional means for the forming of complex components of titanium aluminide alloy. At present, the main casting process is the investment precision casting technology of near-net-shape forming process, and this technology has also achieved the most remarkable results. However, with the continuous improvement of the requirements for aerospace castings, the disadvantages of the investment precision casting process are becoming more and more prominent. The most important disadvantage is that due to the high melting point and poor fluidity of titanium aluminide alloy, for complex components of titanium aluminide alloy, the forming is unstable, especially for thin-walled parts (such as the edges of blades, etc.), and the filling is often incomplete.

[0004] The invention patent with the application publication number of CN102019401A discloses a casting forming method for small complex castings of titanium alloy or titanium aluminide alloy. The method includes the following steps: preparing a permeable shell by investment casting method; preparing a bottom leakage type vacuum suction casting container, which consists of a cavity and an upper cover, and the upper cover is provided with a pouring gate; fixing the shell in the container with a permeable filling material, covering the upper cover of the container, and then fixing the container in the suction casting chamber of the melting furnace so that the graphite suction port, the pouring gate of the container upper cover, and the sprue of the shell are aligned; putting the titanium alloy or titanium aluminide alloy raw material into the melting crucible of the vacuum arc melting furnace, evacuating the melting chamber, and then energizing for arc melting to obtain a button ingot; turning the button ingot over to the suction casting crucible of the vacuum arc melting furnace for re-melting; opening the vacuum system of the suction casting chamber of the vacuum arc melting furnace, and the melt fills the cavity under the combined action of vacuum pressure and its own gravity. After the casting in the cavity cools to room temperature, releasing the vacuum of the suction casting chamber, cleaning the shell, and obtaining the casting. The forming process of this technical solution is very complex. It is necessary to prepare an ingot first, then melt the ingot into a melt, and then fill the melt into the cavity. The more complex the process, the more unstable the forming and the more incomplete the filling.

[0005] The invention patent with the publication number of CN109550898A discloses a precision investment casting method for titanium aluminide alloy, including the following steps: preparing a mold shell; transferring the mold shell to a melting and pouring device and placing it inside an intermediate frequency induction heating coil; heating and insulating the mold shell; melting the TiAl alloy into a liquid by means of induction heating and consumable electrode arc melting, and injecting it into a copper crucible; cooling the TiAl alloy liquid in the copper crucible, and after cooling to a temperature below the preset temperature, cooling it in the furnace for a preset time; transferring the mold shell outside the melting and pouring device, cleaning it, and taking out the casting. This technical solution is a relatively traditional pouring method, which requires flipping the copper crucible to pour the liquid into the mold shell. Due to the high melting point and poor fluidity of the titanium aluminide alloy, for the preparation of complex components of titanium aluminide alloy, the forming is unstable and the filling is incomplete. Summary of the Invention

[0006] To solve the problems existing in the prior art, the present invention provides a forming method for complex components of titanium aluminide alloy, which includes the following steps in sequence:

[0007] Step 1: Design a graphite mold shell and a graphite pouring cup according to the structure of the complex component of titanium aluminide alloy to be poured;

[0008] Step 2: Manufacture the graphite mold shell and the graphite pouring cup by mechanical processing;

[0009] Step 3: Coat the inner cavity surfaces of the graphite mold shell and the graphite pouring cup with high-temperature resistant ceramic coatings respectively;

[0010] Step 4: Conduct vacuum degassing treatment on the graphite mold shell and the graphite pouring cup;

[0011] Step 5: After the vacuum degassing treatment is completed, assemble and seal the graphite mold shell and the graphite pouring cup according to the design drawings;

[0012] Step 6: Put the titanium aluminide alloy material into the graphite pouring cup above the graphite mold shell;

[0013] Step 7: Put the graphite mold shell, the graphite pouring cup, and the titanium aluminide alloy material in the graphite pouring cup as a whole into the crucible in a vacuum induction melting furnace;

[0014] Step 8: Conduct gas washing treatment on the graphite mold shell, the graphite pouring cup, and the titanium aluminide alloy material in the graphite pouring cup as a whole in the crucible;

[0015] Step 9: After the gas washing treatment is completed, turn on the vacuum induction melting furnace for heating, and during the heating process, the titanium aluminide alloy material is poured and filled;

[0016] Step 10: After the pouring and filling is completed, take out the graphite mold shell, the graphite pouring cup, and the complex component that has been poured and filled in the graphite mold shell as a whole from the vacuum induction melting furnace, and put the whole into an annealing furnace for annealing treatment;

[0017] Step Eleven: Take out the complex titanium-aluminum alloy component from the graphite shell, and clean the graphite shell and the graphite pouring cup.

[0018] Preferably, in Step Three, the inner cavity surface of the graphite shell is coated with four layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coatings are yttrium oxide and / or calcium oxide refractory materials; the thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.02 - 0.05 mm, the viscosity is 17 - 65 Pa·s, and the particle size of the ceramic powder is not less than 250 mesh; the thickness of the third layer of high-temperature resistant ceramic coating and the fourth layer of high-temperature resistant ceramic coating is 0.06 - 0.12 mm, the viscosity is 8 - 15 Pa·s, and the particle size of the ceramic powder is not less than 200 mesh. More preferably, the total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.05 - 0.08 mm, and the total thickness of the third layer of high-temperature resistant ceramic coating and the fourth layer of high-temperature resistant ceramic coating is 0.15 - 0.2 mm.

[0019] Preferably in any of the above solutions, in Step Three, the inner cavity surface of the graphite pouring cup is coated with two layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coatings are yttrium oxide and / or calcium oxide refractory materials; the thickness of the first layer of high-temperature resistant ceramic coating is 0.04 - 0.06 mm, the viscosity is 17 - 30 Pa·s, and the particle size of the ceramic powder is not less than 200 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.08 - 0.15 mm, the viscosity is 8 - 15 Pa·s, and the particle size of the ceramic powder is not less than 200 mesh. More preferably, the total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.15 - 0.2 mm.

[0020] Through a large number of experiments, it is proved that by coating yttrium oxide and / or calcium oxide refractory materials on the inner cavity surfaces of the graphite shell and the graphite pouring cup respectively, the parameters such as the number of coating layers, the thickness of each coating layer, the viscosity of the coating, and the particle size of the ceramic powder work together to maximize the collapsibility of the shell during the casting process and the density of the casting, and at the same time prevent carbon in the graphite from infiltrating into the titanium-aluminum alloy casting.

[0021] Preferably in any of the above solutions, in Step Four, the vacuum degassing treatment process for the graphite shell and the graphite pouring cup is: heating temperature 950 - 1060 °C, holding time 1 - 2 h, vacuum degree not higher than 0.02 MPa, and cooling with the furnace after the holding ends. The vacuum degassing treatment can ceramicize the coatings on the inner cavity surfaces of the graphite shell and the graphite pouring cup, thereby further improving the collapsibility of the shell and the density of the casting.

[0022] Preferably, in any of the above solutions, in step six, the titanium-aluminum alloy material is one or several of titanium-aluminum alloy blocks, titanium-aluminum alloy powders, and titanium-aluminum alloy rods.

[0023] Preferably, in any of the above solutions, in step seven, a high-temperature resistant ceramic material is used for isolation between the graphite mold shell and the crucible, and the thickness of the high-temperature resistant ceramic material is 8 - 20 mm. The isolation material used between the graphite mold shell and the crucible is a high-temperature resistant ceramic material such as alumina and yttrium oxide. This isolation material is equivalent to an insulating layer to avoid reactions between the graphite mold shell and the crucible after heating.

[0024] Preferably, in any of the above solutions, in step eight, the degassing treatment process for the entire titanium-aluminum alloy material in the graphite mold shell, graphite pouring cup, and graphite pouring ladle is as follows: evacuate the vacuum induction melting furnace. When the vacuum degree is less than 0.01 Pa, fill argon at a flow rate of 0.5 - 0.8 L / min until 900 Pa and then stop filling; after stopping filling for 10 - 30 s, continue to fill argon at a flow rate of 0.5 - 0.8 L / min until 900 Pa and then stop filling; after stopping filling for 10 - 30 s, continue to fill argon at a flow rate of 0.5 - 0.8 L / min until 900 Pa and then stop filling, thus completing the three degassing processes.

[0025] Preferably, in any of the above solutions, in step nine, the pouring and filling process of the titanium-aluminum alloy material is as follows: heat up at a heating rate of 20 - 30 °C / min to 1700 - 1800 °C. When the temperature reaches the melting point of the titanium-aluminum alloy material, the titanium-aluminum alloy material starts to melt and flows into the graphite mold shell for pouring and filling. After all the titanium-aluminum alloy material has melted and flowed into the graphite mold shell, keep it warm for 4 - 10 min and then stop heating.

[0026] Preferably, in any of the above solutions, in step ten, the annealing treatment process for the entire complex component that has been poured and filled in the graphite mold shell, graphite pouring cup, and graphite mold shell is as follows: annealing temperature is 950 - 980 °C, holding time is 2 - 3 h, and cooling is carried out in the furnace.

[0027] Preferably, a barrier sheet is provided between the graphite mold shell and the graphite pouring cup. The barrier sheet is a niobium sheet, and the thickness of the barrier sheet is 0.05 - 0.1 mm. If the technical solution of the present invention is used to pour the Ti 2 AlNb alloy complex component, then a niobium sheet needs to be provided between the graphite mold shell and the graphite pouring cup. First, put the alloy material in the graphite pouring cup. At low temperatures, even if the alloy material melts, it will not flow into the graphite mold shell. When the temperature continues to rise, the niobium sheet melts, and the alloy material melt flows into the graphite mold shell, thereby reducing the reaction time between the alloy material melt and the ceramic coating on the inner cavity surface of the graphite mold shell.

[0028] In the present invention, equipment such as the vacuum induction melting furnace, crucible, annealing furnace, and vacuum degassing furnace used are all conventional equipment, and there are no special requirements for specific models; the graphite mold shell used can be directly machined from graphite blanks such as square and cylindrical shapes into the shape of the component, and the positional relationship, connection relationship, etc. between the graphite pouring cup and the graphite mold shell can adopt conventional methods without special requirements.

[0029] The forming method of the complex component of titanium aluminum alloy in the present invention solves the technical barriers of high melting point and poor fluidity of titanium aluminum alloy, improves the superheat degree of the titanium aluminum alloy liquid, shortens the pouring time, and enables the titanium aluminum alloy liquid to complete filling in the liquid state. The present invention can be applied to the forming of complex components of refractory and low-fluidity titanium aluminum alloy, and can also be applied to the forming of other refractory alloys and alloys with poor fluidity, as well as the conventional forming of other metal alloys.

[0030] The forming method of the complex component of titanium aluminum alloy in the present invention has the following beneficial effects:

[0031] (1) Coating the inner cavity surfaces of the graphite mold shell and the graphite pouring cup with a high-temperature resistant ceramic coating can improve the collapsibility of the mold shell and the density of the casting during the pouring process, and at the same time can prevent carbon in the graphite from infiltrating into the titanium aluminum alloy casting.

[0032] (2) Using ceramic materials to isolate between the graphite mold shell and the crucible in the vacuum induction melting furnace to avoid the reaction between the graphite mold shell and the crucible after heating.

[0033] (3) The titanium aluminum alloy material can be in various shapes such as alloy blocks, alloy powders, alloy rods, etc. The alloy materials in various shapes can be directly placed in the graphite pouring cup above the graphite mold shell. After heating, the titanium aluminum alloy liquid flows into the graphite mold shell under the action of gravity.

[0034] (4) Using a vacuum induction melting furnace to rapidly heat the graphite mold shell, graphite pouring cup, and titanium aluminum alloy material as a whole, the titanium aluminum alloy material is rapidly melted into titanium aluminum alloy liquid. At high temperature, the titanium aluminum alloy liquid fills the entire graphite mold shell, thereby realizing the forming of the complex component of titanium aluminum alloy, and the forming effect is good without blind spots; for complex components with low requirements for carbon content, a vacuum heat treatment furnace with a working temperature of about 1800 °C can also be used for heating. Description of the Drawings

[0035] Figure 1 It is a product photo of a preferred embodiment of the forming method of the complex component of titanium aluminum alloy according to the present invention, that is, a large TiAl alloy inner guide vane complex component (Φ580×90 mm);

[0036] Figure 2 It is a product photo of another preferred embodiment of the forming method of the complex component of titanium aluminum alloy according to the present invention, that is, a large Ti2 AlNb Guided Flight Control Cabin Housing (Φ304×550mm). Detailed Implementation Manner

[0037] To further understand the content of the present invention, the present invention will be elaborated in detail below in conjunction with specific embodiments.

[0038] Embodiment 1:

[0039] This embodiment is applicable to the preparation of refractory and poor-fluidity titanium-aluminum alloy complex components. According to a preferred embodiment of the forming method of the titanium-aluminum alloy complex components of the present invention, it includes the following steps in sequence:

[0040] Step 1: Design a graphite mold shell and a graphite pouring cup according to the structure of the titanium-aluminum alloy complex component to be cast;

[0041] Step 2: Use mechanical processing methods to fabricate the graphite mold shell and the graphite pouring cup;

[0042] Step 3: Coat the inner cavity surfaces of the graphite mold shell and the graphite pouring cup with high-temperature resistant ceramic coatings respectively;

[0043] Step 4: Conduct vacuum degassing treatment on the graphite mold shell and the graphite pouring cup;

[0044] Step 5: After the vacuum degassing treatment is completed, assemble and seal the graphite mold shell and the graphite pouring cup according to the design drawings;

[0045] Step 6: Place the titanium-aluminum alloy material into the graphite pouring cup above the graphite mold shell;

[0046] Step 7: Place the graphite mold shell, the graphite pouring cup, and the titanium-aluminum alloy material in the graphite pouring cup as a whole into the crucible in a vacuum induction melting furnace;

[0047] Step 8: Conduct gas washing treatment on the graphite mold shell, the graphite pouring cup, and the titanium-aluminum alloy material in the graphite pouring cup as a whole in the crucible;

[0048] Step 9: After the gas washing treatment is completed, start the vacuum induction melting furnace for heating, and during the heating process, the titanium-aluminum alloy material is poured and filled;

[0049] Step 10: After the pouring and filling is completed, take out the graphite mold shell, the graphite pouring cup, and the complex component that has been poured and filled in the graphite mold shell as a whole from the vacuum induction melting furnace, and place the whole into an annealing furnace for annealing treatment;

[0050] Step 11: Take out the titanium-aluminum alloy complex component from the graphite mold shell, and clean the graphite mold shell and the graphite pouring cup.

[0051] In Step 3, the inner cavity surface of the graphite shell is coated with four layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coating is yttrium oxide refractory material. The total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.06 mm, where: the thickness of the first layer of high-temperature resistant ceramic coating is 0.03 mm, the viscosity is 40 Pa·s, and the particle size of the ceramic powder is 250 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.03 mm, the viscosity is 40 Pa·s, and the particle size of the ceramic powder is 250 mesh. The total thickness of the third layer of high-temperature resistant ceramic coating and the fourth layer of high-temperature resistant ceramic coating is 0.18 mm, where: the thickness of the third layer of high-temperature resistant ceramic coating is 0.1 mm, the viscosity is 12 Pa·s, and the particle size of the ceramic powder is 200 mesh; the thickness of the fourth layer of high-temperature resistant ceramic coating is 0.08 mm, the viscosity is 12 Pa·s, and the particle size of the ceramic powder is 200 mesh.

[0052] In Step 3, the inner cavity surface of the graphite pouring cup is coated with two layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coating is yttrium oxide refractory material. The total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.18 mm, where: the thickness of the first layer of high-temperature resistant ceramic coating is 0.05 mm, the viscosity is 22 Pa·s, and the particle size of the ceramic powder is 200 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.13 mm, the viscosity is 12 Pa·s, and the particle size of the ceramic powder is 200 mesh.

[0053] In Step 4, the vacuum degassing treatment process for the graphite shell and the graphite pouring cup is: heating temperature 1000 °C, holding time 1.5 h, vacuum degree 0.02 MPa, and cooling with the furnace after the holding ends.

[0054] In Step 6, the titanium-aluminum alloy material is a titanium-aluminum alloy block or titanium-aluminum alloy powder.

[0055] In Step 7, a high-temperature resistant ceramic material is used for isolation between the graphite shell and the crucible, and the thickness of the high-temperature resistant ceramic material is 15 mm.

[0056] In Step 8, the washing gas treatment process for the graphite shell, the graphite pouring cup and the titanium-aluminum alloy material in the graphite pouring cup as a whole is: evacuating the vacuum induction melting furnace, when the vacuum degree is less than 0.01 Pa, filling argon at a flow rate of 0.6 L / min until 900 Pa and then stopping the gas filling; after stopping the gas filling for 20 s, continue to fill argon at a flow rate of 0.6 L / min until 900 Pa and then stop the gas filling; after stopping the gas filling for 20 s, continue to fill argon at a flow rate of 0.6 L / min until 900 Pa and then stop the gas filling, and then the three-time gas washing process can be completed.

[0057] In Step 9, the casting filling process of the titanium aluminum alloy material is as follows: heating at a heating rate of 25 °C / min to 1750 °C. When the temperature reaches the melting point of the titanium aluminum alloy material, the titanium aluminum alloy material begins to melt and flows into the graphite mold shell for casting filling. After all the titanium aluminum alloy material has melted and flowed into the graphite mold shell, keep it warm for 8 minutes and then stop heating.

[0058] In Step 10, the annealing treatment process for the graphite mold shell, graphite pouring cup, and the overall complex component already cast and filled in the graphite mold shell is: annealing temperature 960 °C, holding time 2.5 h, and cooling in the furnace.

[0059] In this embodiment, equipment such as the vacuum induction melting furnace, crucible, annealing furnace, and vacuum degassing furnace used are all conventional equipment, and no special requirements are made for the specific models; the graphite mold shell used can be directly machined from graphite blanks such as square and cylindrical shapes into the shape of the component. The positional relationship, connection relationship, etc. between the graphite pouring cup and the graphite mold shell can adopt conventional methods and no special requirements are made.

[0060] The forming method of the titanium aluminum alloy complex component in this embodiment has the following beneficial effects: (1) Coating high-temperature resistant ceramic coatings on the inner cavity surfaces of the graphite mold shell and the graphite pouring cup can improve the collapsibility of the mold shell during the casting process and the density of the casting, and at the same time can prevent carbon in the graphite from infiltrating into the titanium aluminum alloy casting; (2) Using ceramic materials to isolate between the graphite mold shell and the crucible in the vacuum induction melting furnace to avoid the reaction between the graphite mold shell and the crucible after heating; (3) The titanium aluminum alloy material can be in various shapes such as alloy blocks and alloy powders. Various shaped alloy materials can be directly placed in the graphite pouring cup above the graphite mold shell. After heating, the titanium aluminum alloy liquid flows into the graphite mold shell under the action of gravity; (4) Using a vacuum induction melting furnace to rapidly heat the graphite mold shell, graphite pouring cup, and titanium aluminum alloy material as a whole, the titanium aluminum alloy material rapidly melts into titanium aluminum alloy liquid, and at high temperature, the titanium aluminum alloy liquid fills the entire graphite mold shell, thereby realizing the forming of the titanium aluminum alloy complex component, and the forming effect is good without blind spots. As Figure 1 shown, for the large TiAl alloy inner guide vane complex component (Φ580×90 mm) prepared according to the method of this embodiment, the complete forming of the component can be realized and the dimensions are accurate.

[0061] Example 2:

[0062] This embodiment is applicable to preparing refractory and poor-fluidity titanium aluminum alloy complex components. According to another preferred embodiment of the forming method of the titanium aluminum alloy complex component of the present invention, the specific process steps, equipment used, principles, beneficial effects, etc. are basically the same as those in Example 1, except that:

[0063] In Step 3, the inner cavity surface of the graphite shell is coated with four layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coating is yttrium oxide refractory material. The total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.05 mm, where: the thickness of the first layer of high-temperature resistant ceramic coating is 0.02 mm, the viscosity is 17 Pa·s, and the particle size of the ceramic powder is 250 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.03 mm, the viscosity is 17 Pa·s, and the particle size of the ceramic powder is 250 mesh. The total thickness of the third layer of high-temperature resistant ceramic coating and the fourth layer of high-temperature resistant ceramic coating is 0.15 mm, where: the thickness of the third layer of high-temperature resistant ceramic coating is 0.06 mm, the viscosity is 8 Pa·s, and the particle size of the ceramic powder is 200 mesh; the thickness of the fourth layer of high-temperature resistant ceramic coating is 0.09 mm, the viscosity is 8 Pa·s, and the particle size of the ceramic powder is 200 mesh.

[0064] In Step 3, the inner cavity surface of the graphite pouring cup is coated with two layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coating is yttrium oxide refractory material. The total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.15 mm, where: the thickness of the first layer of high-temperature resistant ceramic coating is 0.04 mm, the viscosity is 17 Pa·s, and the particle size of the ceramic powder is 200 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.11 mm, the viscosity is 8 Pa·s, and the particle size of the ceramic powder is 200 mesh.

[0065] In Step 4, the vacuum degassing treatment process for the graphite shell and the graphite pouring cup is: heating temperature 950 °C, holding time 2 h, vacuum degree 0.02 MPa, and cooling with the furnace after the holding ends.

[0066] In Step 6, the titanium-aluminum alloy material is a titanium-aluminum alloy block or titanium-aluminum alloy powder.

[0067] In Step 7, a high-temperature resistant ceramic material is used for isolation between the graphite shell and the crucible, and the thickness of the high-temperature resistant ceramic material is 8 mm.

[0068] In Step 8, the gas washing treatment process for the graphite shell, the graphite pouring cup and the titanium-aluminum alloy material in the graphite pouring cup as a whole is: evacuating the vacuum induction melting furnace, when the vacuum degree is less than 0.01 Pa, filling argon at a flow rate of 0.5 L / min until 900 Pa and then stopping the gas filling; after stopping the gas filling for 30 s, continuing to fill argon at a flow rate of 0.5 L / min until 900 Pa and then stopping the gas filling; after stopping the gas filling for 30 s, continuing to fill argon at a flow rate of 0.5 L / min until 900 Pa and then stopping the gas filling, and thus the three gas washing processes can be completed.

[0069] In Step 9, the casting filling process of the titanium-aluminum alloy material is as follows: heating at a rate of 20 °C / min to 1700 °C. When the temperature reaches the melting point of the titanium-aluminum alloy material, the titanium-aluminum alloy material starts to melt and flows into the graphite mold shell for casting filling. After all the titanium-aluminum alloy material has melted and flowed into the graphite mold shell, keep it warm for 10 min and then stop heating.

[0070] In Step 10, the annealing treatment process for the graphite mold shell, graphite pouring cup and the overall complex component already cast and filled in the graphite mold shell is as follows: annealing temperature is 950 °C, holding time is 3 h, and cooling is carried out in the furnace.

[0071] Example 3:

[0072] This example is applicable to the preparation of refractory and poor-fluidity titanium-aluminum alloy complex components. According to another preferred embodiment of the forming method of the titanium-aluminum alloy complex components of the present invention, the specific process steps, equipment used, principles, beneficial effects, etc. are basically the same as those in Example 1, except that:

[0073] In Step 3, the inner cavity surface of the graphite mold shell is coated with four layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coatings are yttrium oxide refractory materials. The total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.08 mm, where: the thickness of the first layer of high-temperature resistant ceramic coating is 0.04 mm, the viscosity is 65 Pa·s, and the particle size of the ceramic powder is 250 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.04 mm, the viscosity is 65 Pa·s, and the particle size of the ceramic powder is 250 mesh. The total thickness of the third layer of high-temperature resistant ceramic coating and the fourth layer of high-temperature resistant ceramic coating is 0.2 mm, where: the thickness of the third layer of high-temperature resistant ceramic coating is 0.12 mm, the viscosity is 15 Pa·s, and the particle size of the ceramic powder is 200 mesh; the thickness of the fourth layer of high-temperature resistant ceramic coating is 0.08 mm, the viscosity is 15 Pa·s, and the particle size of the ceramic powder is 200 mesh.

[0074] In Step 3, the inner cavity surface of the graphite pouring cup is coated with two layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coatings are yttrium oxide refractory materials. The total thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.2 mm, where: the thickness of the first layer of high-temperature resistant ceramic coating is 0.06 mm, the viscosity is 30 Pa·s, and the particle size of the ceramic powder is 200 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.14 mm, the viscosity is 15 Pa·s, and the particle size of the ceramic powder is 200 mesh.

[0075] In Step 4, the vacuum degassing treatment process for the graphite mold shell and the graphite pouring cup is as follows: heating temperature is 1060 °C, holding time is 1 h, vacuum degree is 0.02 MPa, and after the holding is over, cooling is carried out in the furnace.

[0076] In Step 6, the titanium-aluminum alloy material is a titanium-aluminum alloy block or titanium-aluminum alloy powder.

[0077] In Step 7, a high-temperature resistant ceramic material is used to isolate the graphite mold shell from the crucible, and the thickness of the high-temperature resistant ceramic material is 20 mm.

[0078] In Step 8, the degassing treatment process for the graphite mold shell, graphite pouring cup and the titanium-aluminum alloy material in the graphite pouring cup as a whole is as follows: evacuate the vacuum induction melting furnace. When the vacuum degree is less than 0.01 Pa, fill argon at a flow rate of 0.8 L / min until 900 Pa and then stop filling; after stopping filling for 10 s, continue to fill argon at a flow rate of 0.8 L / min until 900 Pa and then stop filling; after stopping filling for 10 s, continue to fill argon at a flow rate of 0.8 L / min until 900 Pa and then stop filling, and thus the three degassing processes can be completed.

[0079] In Step 9, the casting filling process of the titanium-aluminum alloy material is as follows: heat up at a heating rate of 30 °C / min to 1800 °C. When the temperature reaches the melting point of the titanium-aluminum alloy material, the titanium-aluminum alloy material starts to melt and flows into the graphite mold shell for casting filling. After all the titanium-aluminum alloy material has melted and completely flowed into the graphite mold shell, keep it warm for 4 min and then stop heating.

[0080] In Step 10, the annealing treatment process for the graphite mold shell, graphite pouring cup and the complex component that has been cast and filled in the graphite mold shell as a whole is as follows: the annealing temperature is 980 °C, the holding time is 2 h, and it is cooled in the furnace.

[0081] Example 4:

[0082] This example is applicable to the preparation of refractory and poor-fluidity Ti 2 AlNb alloy complex components. According to another preferred embodiment of the forming method of the titanium-aluminum alloy complex components of the present invention, the specific process steps, the equipment used, the principle, the beneficial effects, etc. are basically the same as those in Examples 1 to 3. The differences are as follows:

[0083] A barrier sheet is arranged between the graphite mold shell and the graphite pouring cup. The barrier sheet is a niobium sheet with a thickness of 0.05 mm. First, put the alloy material in the graphite pouring cup. At low temperatures, even if the alloy material melts, it will not flow into the graphite mold shell. When the temperature continues to rise, the niobium sheet melts and the alloy material melt flows into the graphite mold shell, thereby reducing the reaction time between the alloy material melt and the ceramic coating on the inner cavity surface of the graphite mold shell. As Figure 2 shown, for the large-sized Ti 2 AlNb guided flight control cabin shell (Φ304×550 mm) prepared by the method of this example, the complete forming of the component can be realized and the dimensions are accurate.

[0084] Example 5:

[0085] This embodiment is applicable to the preparation of refractory and poor-fluidity Ti 2 AlNb alloy complex components. According to another preferred embodiment of the forming method of the titanium-aluminum alloy complex components of the present invention, the specific process steps, the equipment used, the principle, the beneficial effects, etc. are basically the same as those in Embodiments 1 to 3. The difference is that:

[0086] A barrier sheet is arranged between the graphite shell and the graphite pouring cup. The barrier sheet is a niobium sheet with a thickness of 0.5 mm. First, alloy materials are placed in the graphite pouring cup. At low temperatures, even if the alloy materials melt, they will not flow into the graphite shell. When the temperature continues to rise, the niobium sheet melts, and the alloy material melt flows into the graphite shell, thereby reducing the reaction time between the alloy material melt and the ceramic coating on the inner cavity surface of the graphite shell.

[0087] Embodiment 6:

[0088] This embodiment is applicable to the preparation of refractory and poor-fluidity Ti 2 AlNb alloy complex components. According to another preferred embodiment of the forming method of the titanium-aluminum alloy complex components of the present invention, the specific process steps, the equipment used, the principle, the beneficial effects, etc. are basically the same as those in Embodiments 1 to 3. The difference is that:

[0089] A barrier sheet is arranged between the graphite shell and the graphite pouring cup. The barrier sheet is a niobium sheet with a thickness of 1 mm. First, alloy materials are placed in the graphite pouring cup. At low temperatures, even if the alloy materials melt, they will not flow into the graphite shell. When the temperature continues to rise, the niobium sheet melts, and the alloy material melt flows into the graphite shell, thereby reducing the reaction time between the alloy material melt and the ceramic coating on the inner cavity surface of the graphite shell.

[0090] Special note: Many parameters are involved in the technical solution of the present invention. The synergistic effects of various parameters need to be comprehensively considered to obtain the beneficial effects and significant progress of the present invention. Moreover, the value ranges of various parameters in the technical solution are obtained through a large number of experiments. For each parameter and the combination of various parameters, the inventor has recorded a large amount of experimental data. Due to space limitations, the specific experimental data are not disclosed herein.

[0091] It is not difficult for those skilled in the art to understand that the forming method of the titanium-aluminum alloy complex components of the present invention includes any combination of the above-mentioned invention content, specific implementation manners of the present invention specification, and various parts shown in the drawings. Due to space limitations and to make the specification concise, the various solutions formed by these combinations are not described one by one. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A forming method for a complex component of titanium-aluminum alloy, in sequential order includes the following steps: Step 1: Design a graphite mold shell and a graphite pouring cup according to the structure of the complex component of titanium-aluminum alloy to be cast; Step 2: Fabricate the graphite mold shell and the graphite pouring cup by mechanical processing; Step 3: Coat the inner cavity surfaces of the graphite mold shell and the graphite pouring cup with high-temperature resistant ceramic coatings respectively; Step 4: Conduct vacuum degassing treatment on the graphite mold shell and the graphite pouring cup; Step 5: After the vacuum degassing treatment is completed, assemble and seal the graphite mold shell and the graphite pouring cup according to the design drawings; Step 6: Place the titanium-aluminum alloy material into the graphite pouring cup above the graphite mold shell; Step 7: Integrally place the graphite mold shell, the graphite pouring cup, and the titanium-aluminum alloy material in the graphite pouring cup into the crucible in a vacuum induction melting furnace; Step 8: Conduct gas washing treatment on the graphite mold shell, the graphite pouring cup, and the titanium-aluminum alloy material in the graphite pouring cup as a whole; Step 9: After the gas washing treatment is completed, start the vacuum induction melting furnace for heating, and during the heating process, the titanium-aluminum alloy material is poured and filled; Step 10: After the pouring and filling are completed, take out the graphite mold shell, the graphite pouring cup, and the complex component that has been poured and filled in the graphite mold shell as a whole from the vacuum induction melting furnace, and place them as a whole into an annealing furnace for annealing treatment; Step 11: Take out the complex component of titanium-aluminum alloy from the graphite mold shell, and clean the graphite mold shell and the graphite pouring cup; In Step 7, a high-temperature resistant ceramic material is used to isolate between the graphite mold shell and the crucible, and the thickness of the high-temperature resistant ceramic material is 8 - 20 mm; In Step 8, the gas washing treatment process for the graphite mold shell, the graphite pouring cup, and the titanium-aluminum alloy material in the graphite pouring cup as a whole is as follows: evacuate the vacuum induction melting furnace, when the vacuum degree is less than 0.01 Pa, fill argon at a flow rate of 0.5 - 0.8 L / min until 900 Pa, and then stop filling; after stopping filling for 10 - 30 s, continue to fill argon at a flow rate of 0.5 - 0.8 L / min until 900 Pa and then stop filling; after stopping filling for 10 - 30 s, continue to fill argon at a flow rate of 0.5 - 0.8 L / min until 900 Pa and then stop filling, and thus the three gas washing processes can be completed; In Step 10, the annealing treatment process for the graphite mold shell, the graphite pouring cup, and the complex component that has been poured and filled in the graphite mold shell as a whole is as follows: the annealing temperature is 950 - 980 °C, the holding time is 2 - 3 h, and it is cooled with the furnace; A barrier sheet is arranged between the graphite mold shell and the graphite pouring cup, the barrier sheet is a niobium sheet, and the thickness of the barrier sheet is 0.05 - 0.1 mm.

2. According to the forming method for a complex component of titanium-aluminum alloy described in Claim 1, it is characterized in that: In step three, the inner cavity surface of the graphite shell is coated with four layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coatings are yttrium oxide and / or calcium oxide refractory materials; the thickness of the first layer of high-temperature resistant ceramic coating and the second layer of high-temperature resistant ceramic coating is 0.02 - 0.05 mm, the viscosity is 17 - 65 Pa·s, and the particle size of the ceramic powder is not less than 250 mesh; the thickness of the third layer of high-temperature resistant ceramic coating and the fourth layer of high-temperature resistant ceramic coating is 0.06 - 0.12 mm, the viscosity is 8 - 15 Pa·s, and the particle size of the ceramic powder is not less than 200 mesh.

3. The forming method of the titanium-aluminum alloy complex component according to claim 2, characterized in that: In step three, the inner cavity surface of the graphite pouring cup is coated with two layers of high-temperature resistant ceramic coatings, and the high-temperature resistant ceramic coatings are yttrium oxide and / or calcium oxide refractory materials; the thickness of the first layer of high-temperature resistant ceramic coating is 0.04 - 0.06 mm, the viscosity is 17 - 30 Pa·s, and the particle size of the ceramic powder is not less than 200 mesh; the thickness of the second layer of high-temperature resistant ceramic coating is 0.08 - 0.15 mm, the viscosity is 8 - 15 Pa·s, and the particle size of the ceramic powder is not less than 200 mesh.

4. The forming method of the titanium-aluminum alloy complex component according to claim 3, characterized in that: In step four, the vacuum degassing treatment process of the graphite shell and the graphite pouring cup is that the heating temperature is 950 - 1060 °C, the heat preservation time is 1 - 2 h, the vacuum degree is not higher than 0.02 MPa, and it is cooled with the furnace after the heat preservation ends.

5. The forming method of the titanium-aluminum alloy complex component according to claim 4, characterized in that: In step six, the titanium-aluminum alloy material is one or several of titanium-aluminum alloy blocks, titanium-aluminum alloy powders, and titanium-aluminum alloy rods.

6. The forming method of the titanium-aluminum alloy complex component according to claim 5, characterized in that: In step nine, the pouring and filling process of the titanium-aluminum alloy material is to heat up at a heating rate of 20 - 30 °C / min to 1700 - 1800 °C. When the temperature reaches the melting point of the titanium-aluminum alloy material, the titanium-aluminum alloy material starts to melt and flows into the graphite shell for pouring and filling. After the titanium-aluminum alloy material is completely melted and completely flows into the graphite shell, keep it warm for 4 - 10 min and then stop heating.

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