A method for manufacturing a b-modified ti750 alloy blade

Abstract

The application provides a pouring forming and processing method of B-modified Ti750 alloy blade, and belongs to the technical field of titanium alloy precision casting. TiB2 particles are mixed into electrodes as intermediate alloy, and then are smelted for 2-3 times in a vacuum consumable furnace to prepare a B-modified Ti750 alloy ingot with uniform composition; a sand box provided with a blade mold shell is placed in a heating furnace; the B-modified Ti750 alloy ingot is smelted into a liquid state and then is poured into the mold to pour and form a B-modified Ti750 alloy blade; after the B-modified Ti750 alloy blade is demolded, the blade is subjected to hot isostatic pressing treatment, and is furnace-cooled after being kept at temperature and pressure for 2-4 hours in an argon protection environment; and the B-modified Ti750 alloy blade is placed in an oxygen atmosphere with 2-5 times of standard atmospheric pressure or a mixed atmosphere with equivalent oxygen concentration to be subjected to surface oxygen permeation treatment. After the above treatment, the B-modified Ti750 alloy has a room temperature fatigue limit of not less than 550MPa and a 600 DEG C high temperature fatigue limit of not less than 420MPa.

Description

Technical Field

[0001] This invention belongs to the field of precision casting technology of titanium alloys, specifically relating to a casting and processing method for B-modified Ti750 alloy blades. Background Technology

[0002] Maximizing the use of high-strength titanium alloys is a major development direction for future advanced aerospace vehicles. In recent years, the use of titanium alloys in aircraft both domestically and internationally has increased significantly, making the amount and level of titanium alloy usage an important indicator of the sophistication of domestic and international aerospace technology and aircraft performance.

[0003] Ti750 alloy is a titanium alloy with a "fine lamellar" structure developed by the Institute of Metal Research. The invention patent for this alloy is titled "A Titanium Alloy with Fine Lamellar Microstructure and Its Manufacturing Method," patent number: CN200910012757.1. It possesses high strength and a good balance of ductility and toughness, making it a potential high-strength, high-toughness, and high-temperature resistant titanium alloy material suitable for the fabrication of critical load-bearing components such as compressor blades. However, the significant challenges in process control, high forging and forming costs severely limit its application prospects in the aerospace field. Therefore, finding a simple, effective, and highly reliable processing method for Ti750 alloy components is of great significance for its application and promotion in the aerospace field. Summary of the Invention

[0004] The technical problem solved by this invention: In view of the defects in the prior art, this invention proposes a casting and processing method for B-modified Ti750 alloy blades. This method is simple, effective and highly reliable, and can be widely applied and promoted in the aerospace field.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A casting and processing method for B-modified Ti750 alloy blades, the specific steps of which are as follows:

[0007] Step 1: After mixing TiB2 particles as intermediate alloy into the electrode, press it into a ready electrode, and melt it 2-3 times in a vacuum arc remelting furnace to produce a uniformly composed B-modified Ti750 alloy ingot.

[0008] Step 2: Place the sand box containing the blade mold shell in a heating furnace and keep it at 800℃~1000℃ for 2h~8h;

[0009] Step 3: Melt the B-modified Ti750 alloy ingot into a liquid state in a vacuum arc furnace and then pour it into the blade mold to make the B-modified Ti750 alloy blade. The pouring temperature is 1700℃~1800℃.

[0010] Step 4: After the B-modified Ti750 alloy blades are demolded, they undergo hot isostatic pressing treatment at a temperature of 900℃~1000℃ and a pressure of 120~180MPa. They are then held at this temperature and pressure for 2h~4h under the protection of argon gas before furnace cooling.

[0011] Step 5: Place the B-modified Ti750 alloy blades in an oxygen atmosphere at 2 to 5 times the standard atmospheric pressure or a mixed atmosphere with an equivalent oxygen concentration for surface oxygen infiltration treatment.

[0012] The preferred embodiment of the casting and processing method for B-modified Ti750 alloy blades is as follows: In step one above, the electrode in the B-modified Ti750 alloy ingot, which is mixed with TiB2 particles as intermediate alloy, exists in the form of short fibrous TiB in the solid state after melting, and the volume fraction of TiB in the alloy is 1 vol.% to 5 vol.%.

[0013] The preferred embodiment of the casting and processing method for B-modified Ti750 alloy blades is that, in step four above, the B-modified Ti750 alloy blades are polished and cleaned after hot isostatic pressing, and the roughness Ra≤0.2.

[0014] The preferred embodiment of the casting and processing method for B-modified Ti750 alloy blades is as follows: in step five above, the B-modified Ti750 alloy blades are subjected to surface oxygen infiltration treatment in the range of 590℃~610℃, and the blades are kept at this temperature for 15h~30h before being air-cooled.

[0015] The preferred embodiment of the casting and processing method for B-modified Ti750 alloy blades is as follows: in step five above, the B-modified Ti750 alloy blades are surface-polished after surface oxygen diffusion treatment, with a polishing depth of 20μm to 50μm.

[0016] The advantages and beneficial effects of this invention compared with the prior art are as follows:

[0017] 1. In this scheme, an appropriate amount of TiB is introduced into the Ti750 alloy for reinforcement modification, which can greatly refine the grain and improve the strength of the alloy, making it possible to apply the as-cast B-modified Ti750 alloy in engineering. The processing steps of Ti750 alloy are greatly simplified, and manufacturing costs are also saved.

[0018] 2. In this scheme, the precipitation direction of TiB during solidification is affected by the temperature gradient. Based on the blade shell structure, TiB is mostly distributed in clusters along the blade axis, which can better play the role of short fiber reinforcement phase bearing.

[0019] 3. In this scheme, after surface oxygen diffusion treatment and polishing, the oxide layer is removed from the surface of the B-modified Ti750 alloy blade, while retaining the gradient oxygen diffusion structure. This allows for a slow transition in strength from the surface of the ring component to the substrate, which can simultaneously improve the room temperature and high temperature fatigue performance of the alloy. After the above treatment, the room temperature fatigue limit of the B-modified Ti750 alloy is not less than 550 MPa, and the high temperature fatigue limit at 600℃ is not less than 350 MPa. Attached Figure Description

[0020] Figure 1 This is a high-magnification microstructure photograph of the B-modified Ti750 alloy blade prepared in Example 1 of this invention;

[0021] Figure 2 Photographs of the oxide layer and gradient oxygen permeation structure on the surface of the B-modified Ti750 alloy blade prepared in Example 1 of this invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] The present invention will be further described below with reference to the embodiments.

[0024] Example 1: Please refer to Figure 1-2 As shown, the raw material used is a Ti750 alloy with a composition (wt%) of Ti-5.7Al-3.9Sn-4.5Zr-0.45Mo-0.5Si-0.35Nb-2.0Ta-0.05C. A TiB-reinforced modification was introduced at a volume fraction of 4 vol.%, and the alloy was then melted three times in a vacuum arc remelting furnace to produce a B-modified Ti750 alloy ingot. A sand box containing the blade mold was placed in a heating furnace and held at 900℃ for 4 hours before casting. The B-modified Ti750 alloy ingot was melted into a liquid state in a vacuum arc remelting furnace and poured into the blade mold to produce the B-modified Ti750 alloy blade at a casting temperature of 1700℃. After solidification and demolding, the blade underwent hot isostatic pressing at 970℃ and 150MPa, held at this temperature and pressure for 4 hours under argon protection, and then furnace cooled. After grinding and cleaning the blades, they were placed in an oxygen atmosphere at 3 times the standard atmosphere for surface oxygen infiltration treatment at a temperature of 595℃. After holding at this temperature for 20 hours, the blades were air-cooled and the surface was polished to remove the oxide layer while retaining the gradient oxygen infiltration structure.

[0025] Table 1. Tensile properties of B-modified Ti750 alloy blades in Example 1

[0026] Test temperature <![CDATA[R m , MPa]]> <![CDATA[R p0.2 , Mpa]]> A, % Z, % room temperature 1223 1108 6.0 8 600℃ 784 621 15.5 31

[0027] Table 2 Fatigue properties of B-modified Ti750 alloy blades in Example 1

[0028] Test conditions Fatigue Limit Room temperature, R=-1 575Mpa 600℃，R=-1 455Mpa

[0029] As can be seen from the above embodiments, the B-modified Ti750 alloy blades prepared by this invention not only possess high room temperature and high temperature strength (room temperature strength above 1200 MPa and high temperature strength between 750 MPa at 600℃), but also maintain high fatigue resistance, with a room temperature fatigue limit exceeding 550 MPa and a high temperature fatigue limit exceeding 420 MPa at 600℃.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0031] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for manufacturing a B-modified Ti750 alloy blade, characterized in that: The specific steps are as follows: Step 1: After mixing TiB2 particles as intermediate alloy into the electrode, press it into a ready electrode, and melt it 2-3 times in a vacuum arc remelting furnace to produce a uniformly composed B-modified Ti750 alloy ingot. Step 2: Place the sand box containing the blade mold shell in a heating furnace and keep it at 800℃~1000℃ for 2h~8h; Step 3: Melt the B-modified Ti750 alloy ingot into a liquid state in a vacuum arc furnace and then pour it into the blade mold to make the B-modified Ti750 alloy blade. The pouring temperature is 1700℃~1800℃. Step 4: After the B-modified Ti750 alloy blades are demolded, they undergo hot isostatic pressing treatment at a temperature of 900℃~1000℃ and a pressure of 120~180MPa. They are then held at this temperature and pressure for 2h~4h under the protection of argon gas before furnace cooling. Step 5: Place the B-modified Ti750 alloy blades in an oxygen atmosphere of 2 to 5 times the standard atmosphere or a mixed atmosphere with an equivalent oxygen concentration for surface oxygen infiltration treatment. In step one above, the electrode in the B-modified Ti750 alloy ingot, which is mixed with TiB2 particles as an intermediate alloy, exists in the form of short fibrous TiB in the solid state after melting, and the volume fraction of TiB in the alloy is 1 vol.% to 5 vol.%.

2. The method for manufacturing a B-modified Ti750 alloy blade according to claim 1, characterized in that: In step four above, the B-modified Ti750 alloy blades are polished and cleaned after hot isostatic pressing, with a roughness Ra≤0.

2.

3. The method for manufacturing a B-modified Ti750 alloy blade according to claim 1, characterized in that: In step five above, the surface oxygen infiltration treatment temperature is 590℃~610℃, and the temperature is maintained for 15h~30h before air cooling.

4. The method for manufacturing a B-modified Ti750 alloy blade according to claim 1, characterized in that: In step five above, the B-modified Ti750 alloy blades are surface-polished after surface oxygen diffusion treatment, with a polishing depth of 20μm to 50μm.

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