RU2790704C9 - Method for manufacturing gas turbine engine blades from alloy based on orthorhombic titanium aluminide - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method of deformation-heat treatment of blanks of blades of gas turbine engines from an alloy based on orthorhombic titanium aluminide includes stamping of blanks of blades at a temperature below the Ttt. The forging of blade blanks is carried out with a degree of deformation of at least 50% at a temperature below T_tt by 50-200°C, after which heat treatment is carried out, including two stages, at the first of which quenching in air at a temperature below T_tt by 50-150°C with an exposure of at least 0.5 hours is carried out, and at the second - aging at a temperature below T_tt by 200-300°C with an exposure of 1 to 36 hours, where T_tt is the transformation temperatureβ↔α₂.

EFFECT: provided high mechanical properties of the alloy based on orthorhombic titanium aluminide σ_0.2 ²⁰=1000-1300 MPa; σ_В ²⁰=1150-1400 MPa; δ²⁰=3-8 %; ψ²⁰=3-5%; σ_0.2 ⁶⁵⁰=1030 MPa; σ_В ⁶⁵⁰=1120 MPa; δ⁶⁵⁰=6 %; ψ⁶⁵⁰=4%.

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Description

SUBSTANCE: invention relates to pressure treatment of metals and alloys, namely to technology of pressure treatment of intermetallic alloys based on orthorhombic titanium aluminide and can be used in the aerospace industry to produce gas turbine engine parts from these materials with a regulated structure and specified mechanical properties.

Intermetallic alloys based on orthorhombic titanium aluminide have such properties as high thermal stability, high specific strength characteristics with a sufficient level of plasticity. The combination of these characteristics allows them to be used in gas turbine engines as parts with operating temperatures up to 650°C. However, a limiting factor for the use of these alloys is the difficulty in balancing strength, ductility and fracture toughness at room and operating temperatures. In these alloys, during crystallization, large grains up to several millimeters in size are formed, which hinders plastic deformation and does not allow realizing the full potential of the material. Although the microstructure is significantly refined during hot rolling, however, due to the narrow temperature range of the process, it is not possible to obtain the structure required to ensure a high complex of properties. Heat treatment also does not make it possible to fully improve the mechanical properties. The solution to this problem can be the use of a combination of isothermal forging and heat treatment, which allows, in addition to obtaining the final shape of the product, to form the required structure in blanks of blades made of intermetallic alloys based on orthorhombic titanium aluminide.

At the moment, there are several methods for processing intermetallic alloys based on orthorhombic titanium aluminide by hot deformation methods.

A known method for hot deformation of an alloy based on orthorhombic titanium aluminide Ti-11.4Al-1.31Zr-0.7V-39.9Nb-0.85Mo-0.14Si-0.065C wt. %) in order to obtain bar blanks [Patent of the Russian Federation No. RU 2644830 C2 dated 06/26/2017 "Method of manufacturing bar blanks from alloys based on titanium intermetallic compound with an ortho-phase"] including heating and preliminary deformation of the ingot to obtain a billet, intermediate and final deformation of the billet and the final heat treatment, characterized in that the intermediate deformation of the workpiece is carried out from 2 to 5 precipitates with a degree of 25-40%, combined with pressing with a degree of 55-70%, while heating the workpiece before the first of the intermediate deformations is carried out in steps to a temperature of T _pp + (100-200)°C, where T _PP is the temperature β↔α ₂ of the transformation with an exposure of 2-3 hours, and each subsequent of the intermediate deformations is carried out at a temperature of 50-100°C lower than the previous one with an exposure of 0.5-1 hour less than the previous one, and the last of the intermediate deformations is carried out at a temperature of T _pp -(20-50)°C, and the final deformation of the workpiece is carried out with a degree of not more than 30% at T _pp -(80-120)°C. After deformation, the workpiece was subjected to two-stage heat treatment: 1. heating to T=900°C holding for 2.5 hours, followed by cooling in air to room temperature; 2. heating up to T=850°C exposure for 12 hours, followed by cooling in air to room temperature. Mechanical characteristics at T=20°C: σ _0.2 =1040 MPa; σ _B =1110 MPa; δ=7.0%; ψ=7.5%; at T=650°C: σ _0.2 =860 MPa; σ _B \u003d 890 MPa; δ=13.0%; ψ=25.0%. The disadvantage of this method are high temperature deformation, leading to significant energy consumption and labor intensity of the process, as well as low strength after heat treatment.

There is a known method of hot deformation of an alloy based on orthorhombic titanium aluminide to obtain forgings [RF Patent No. RU 2 520 924 C1 dated 06/27/2014 "Method of manufacturing forgings of disks from an alloy of titanium aluminum based on the ortho-phase"], which consists in multi-stage deformation of an ingot with heating above and then below the temperature of polymorphic transformation (T _pp ) and subsequent heat treatment. In addition, the ingot is subjected to preliminary high-temperature gas-static treatment above the temperature T _PP . Mechanical characteristics at T=20°C: σ _V ~1200 MPa; δ=6-7%; at T=650°C: σ _В ~1000 MPa; δ=9-12%. The disadvantage of this method is the high deformation temperature at the initial stages, which leads to increased requirements for stamping materials and additional costs for heating to higher temperatures.

A known method for hot deformation of an alloy based on orthorhombic titanium aluminide VIT1 [RF Patent No. RU 2 761 398 C1 dated 08.12.2021 "Method of processing rods from ortho-titanium alloys to obtain compressor blades for a gas turbine engine" in order to improve mechanical characteristics, which includes heating bar up to 1100°C, flattening with a degree of deformation of at least 0.5, reheating up to 1100°C and extrusion of the workpiece in a closed die to form a forging with a lock and a blade feather. Then the forging was heated to 1100°C, subjected first to rough and then to finishing stamping of the blades. After low annealing, the following properties were obtained at a temperature of 20°C: ultimate strength σv =1230 MPa; relative elongation δ=20.5% and relative contraction ψ=46.3%. The disadvantage of this method is the high temperature of forging and subsequent stamping, which significantly increases the requirements for stamping materials and increases the cost of production. In addition, there are no data on the heat-resistant characteristics of the obtained state, which does not allow to fully evaluate the developed method.

SUMMARY OF THE INVENTION

The objective of the invention is to provide a high complex of mechanical characteristics of blanks for gas turbine engine blades made of an alloy based on orthorhombic titanium aluminide, combining high strength and heat resistance with a sufficient level of low-temperature ductility.

The technical result of the invention is to obtain high mechanical properties of blanks for blades of gas turbine engines from an alloy based on orthorhombic titanium aluminide as at room temperature: σ _0.2 ²⁰ =1000-1300 MPa; σ _B ²⁰ =1150-1400 MPa; δ ²⁰ \u003d 3-8%; ψ ²⁰ =3-5%; and at operating temperature: σ _0.2 ⁶⁵⁰ = 1030 MPa; σ _B ⁶⁵⁰ =1120 MPa; δ ⁶⁵⁰ = 6%; ψ ⁶⁵⁰ =4%, due to the claimed method of isothermal stamping and subsequent heat treatment.

The objective of the invention is solved by using the proposed method for manufacturing gas turbine engine blades from an alloy based on orthorhombic titanium aluminide, including forging blades with a degree of deformation of at least 50% at a temperature below T _pp by 50-200 ° C, where T _pp is the temperature β↔α ₂ of the transformation , heat treatment, including two stages: quenching in air from a temperature below T _pp by 50-150 ° C with an exposure of at least 0.5 hours and aging at a temperature below T _pp by 200-300 ° C with an exposure of 1 to 36 hours .

The novelty and inventive level of the proposed invention lies in the fact that isothermal forging of blanks of blades and two-stage heat treatment at a temperature significantly below T _pt , where T _{PP is} the temperature β↔α ₂ of the transformation, provides a high complex of mechanical characteristics both at room and operating temperatures alloy VIT1.

The implementation of the invention on the example of an alloy based on orthorhombic titanium aluminide VIT1. Temperature β↔α ₂ transformation (T _PP ) determined using differential scanning calorimetry and amounted to 1100°C. Forging blanks of blades is carried out at a temperature of 50-200°C below T _PP with a degree of deformation of 50%. After that, the blanks are subjected to a two-stage heat treatment:

- hardening in air from a temperature of 50-200 ° C below T _pp , exposure from 0.5 hours, but not more than two hours, because longer exposure is not economically feasible;

- aging at a temperature of 200-300°C below T _pp , exposure 1-36 hours, cooling with an oven.

The invention is characterized in the following images.

Figure 1 - Microstructure of the VIT1 alloy workpiece after deformation-thermal and heat treatment according to the regime: isothermal forging at T=950°C with a degree of deformation of 50%, hardening in air from 1000°C, holding for 1 hour; aging at T=800°C, exposure 6 hours (a - scanning electron microscopy, b - transmission electron microscopy).

Figure 2 - Table "Mechanical properties of VIT1 alloy after isothermal forging and heat treatment"

The possibility of carrying out the invention is illustrated by the following examples of the technological process of isothermal forging of blanks of blades from an alloy based on orthorhombic titanium aluminide VIT1. Mechanical tests of the obtained alloys were carried out using the following setups: universal electromechanical testing machine Instron 5882.

Example 1

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 950°C with a degree of deformation of 50%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=1000°C, holding for 1 hour, aging at 800°C, holding for 6 hours. The microstructure of the resulting stamping is shown in figure 1. The results of mechanical tests are presented in the table in figure 2.

Example 2

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 1050°C with a degree of deformation of 80%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=1050°C, holding for 0.5 hours, aging at 800°C, holding for 6 hours. The results of mechanical tests are presented in the table in figure 2.

Example 3

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 900°C with a degree of deformation of 50%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=1000°C, holding for 0.5 hours, aging at 800°C, holding for 6 hours. The results of mechanical tests are presented in the table in figure 2.

Example 4

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 900°C with a degree of deformation of 50%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=950°C, holding for 1 hour, aging at 800°C, holding for 6 hours. The results of mechanical tests are presented in the table in figure 2.

Example 5

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 1000°C with a degree of deformation of 50%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=1000°C, holding for 0.5 hours, aging at 900°C, holding for 6 hours. The results of mechanical tests are presented in the table in figure 2.

Example 6

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 950°C with a degree of deformation of 50%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=975°C, holding for 2 hours, aging at 850°C, holding for 1 hour. The results of mechanical tests are presented in the table in figure 2.

Example 7

Deformation-heat treatment of VIT1 alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. The workpieces were subjected to isothermal forging at 900°C with a degree of deformation of 50%. After that, the blanks were subjected to heat treatment: quenching in air from a temperature of T=1000°C, holding for 1 hour, aging at 800°C, holding for 36 hours. The results of mechanical tests are presented in the table in figure 2.

The above examples confirm the achievement of the claimed technical result of the invention, which consists in the fact that the proposed modes of thermal and deformation-thermal treatments provide high mechanical properties of the alloy based on orthorhombic titanium aluminide VIT1 σ _0.2 ²⁰ =1000-1300 MPa; σ _B ²⁰ =1150-1400 MPa; δ ²⁰ \u003d 3-8%; ψ ²⁰ =3-5%; σ _0.2 ⁶⁵⁰ = 1030 MPa; σ _B ⁶⁵⁰ =1120 MPa; δ ⁶⁵⁰ = 6%; ψ ⁶⁵⁰ =4%.

Claims (1)

A method for thermal deformation treatment of blanks for blades of gas turbine engines made of an alloy based on orthorhombic titanium aluminide, including forging blanks of blades at a temperature below _{T pp} 200 ° C, after which heat treatment is carried out, including two stages, the first of which is quenched in air at a temperature below T _pp by 50-150 ° C with a holding time of at least 0.5 hours, and the second - aging at a temperature below T _PP at 200-300°C with exposure from 1 to 36 hours, where T _PP is the transformation temperature β↔α ₂ .

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