RU2790711C1 - Method for manufacturing gas turbine engine blades from deformed blanks of an 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 transformation temperature (Ttt). Before stamping, the blanks of the blades are preheated to a temperature above the temperature Ttt from more than 0 to 100°C, held for at least 0.5 hours, stamping of blanks of blades is carried out with a degree of deformation of at least 50% at a temperature below the temperature Ttt by 50-200°C, after which heat treatment is carried out, including two stages, at the first of which quenching is carried out at a temperature below the temperature Ttt by 50-150°C with an exposure for at least of 0.5 hours, and at the second - aging at a temperature below the temperature Ttt by 200-300°C with an exposure from 1 to 36 hours.

EFFECT: high complex of mechanical characteristics both at room and operating temperatures of the alloy is provided.

1 cl, 2 dwg, 5 ex

Description

The invention relates to the processing of metals and alloys by pressure, and in particular to the technology of pressure treatment of intermetallic alloys based on orthorhombic titanium aluminide and can be used in the aerospace industry to obtain parts of gas turbine engines from these materials with a regulated structure and specified mechanical properties.

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 2 644 830 C2 dated 06/26/2017 "Method of manufacturing bar blanks from alloys based on titanium intermetallic compound with ortho-phase"], including heating and preliminary deformation of the ingot to obtain a billet, intermediate and final billet deformation and final heat treatment, characterized in that intermediate deformation of the billet is carried out by 2 to 5 drafts with a degree of 25-40%, combined with pressing with a degree of 55-70%, while heating the billet before the first of the intermediate deformations is carried out stepwise to a temperature T _pp +(100-200)°C, where T _pp is the temperature β↔α ₂ of the transformation with a holding time 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 a holding time 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% p ri T _pp - (80-120) ° С. 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 for 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 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.

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

EFFECT: high mechanical properties of gas turbine engine blade blanks made of an alloy based on orthorhombic titanium aluminide due to the use of the proposed isometric stamping mode with subsequent heat treatment: σ _0.2 20 =1050-1150 MPa; σ _B ²⁰ =1150-1400 MPa; δ ²⁰ \u003d 4-6%; ψ ²⁰ =3-4%; _σ0.2 ⁶⁵⁰ =1020 MPa; σ _B ⁶⁵⁰ =1110 MPa; δ ⁶⁵⁰ =5%; ψ ⁶⁵⁰ =3%;

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 of 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.

The technical result is achieved by the fact that the alloy based on orthorhombic titanium aluminide VIT1 is subjected to deformation-heat treatment of hot-rolled billets. The temperature β↔α ₂ transformation (hereinafter T _PP ) is determined using differential scanning calorimetry. The workpieces are subjected to preheating to a temperature above T _PP by 0 - 100°C with a holding time of at least 0.5 hours. Isothermal forging of blanks of blades is carried out at a temperature below T _pp by 50-200°C with a degree of deformation of 50%. After that, the blanks are subjected to a two-stage heat treatment:

- hardening from a temperature below T _PP by 50-200 ° C, exposure from 0.5 hours, cooled in air;

- aging at a temperature below T _pp by 200-300°C, exposure from 1 to 36 hours, cooled with an oven.

The distinguishing feature is.

The novelty and inventive level of the proposed invention lies in the application of the operation of preliminary heat treatment of deformed alloy blanks based on orthorhombic titanium aluminide before stamping, and carrying out isothermal stamping of blade blanks at a temperature significantly lower than T _pt , where T _PP is the temperature β↔α ₂ of the transformation. This approach makes it possible to obtain a recrystallized structure of deformed workpieces that is more favorable for further deformation before stamping, which in turn provides a high set of mechanical characteristics both at room and at operating temperatures of the VIT1 alloy.

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: annealing T=1200°C, holding for 0.5 hours cooling in air; isothermal forging at T=1000°C with a degree of deformation of 50%, heating to T=1000°C, holding for 0.5 hours air quenching; aging at T=850°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 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 hot-rolled blanks of VIT1 alloy based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1100°C and kept for 8 hours, followed by cooling in air. 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 at 1000°C, holding for 0.5 hours, cooling in air; aging at 850°C, exposure 6 hours. The results of mechanical tests are presented in the table in figure 2.

Example 2

Deformation-heat treatment of hot-rolled blanks of VIT1 alloy based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1200°C and kept for 0.5 hours, followed by cooling in air. 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 at 1000°C, holding for 0.5 hours, cooling in air; aging at 800°C, exposure 6 hours. The resulting microstructure of the workpiece is shown in figure 1. The results of mechanical tests are presented in the table in figure 2.

Example 3

Deformation-heat treatment of hot-rolled blanks of VIT1 alloy based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1200°C and kept for 0.5 hours, followed by cooling in air. The workpieces were subjected to isothermal forging at 900°C with a degree of deformation of 50%. After that, the workpieces were subjected to heat treatment: hardening 950°C, exposure 0.5 hours, cooling in air; aging at 800°C, exposure 6 hours. The results of mechanical tests are presented in the table in figure 2.

Example 4

Deformation-heat treatment of hot-rolled blanks of VIT1 alloy based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1200°C and kept for 0.5 hours, followed by cooling in air. 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 at 950°C, holding for 0.5 hours, cooling in air; aging at 900°C, exposure 1 hour. The results of mechanical tests are presented in the table in figure 2.

Example 5

Deformation-heat treatment of hot-rolled blanks of VIT1 alloy based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1100°C and kept for 1 hour, followed by cooling in air. 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: heating to 1100°C, holding for 1 hour, hardening in air; aging at 800°C, exposure 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 =1050-1150 MPa; σ _B ²⁰ =1150-1400 MPa; δ ²⁰ \u003d 4-6%; ψ ²⁰ =3-4%; σ _0.2 ⁶⁵⁰ = 1020 MPa; σ _B ⁶⁵⁰ =1110 MPa; δ ⁶⁵⁰ =5%; ψ ⁶⁵⁰ =3%;

Thus, the objective of the invention is solved using the proposed method of isothermal forging and two-stage heat treatment using the example of VIT1 alloy.

Claims (1)

A method for deformation-heat treatment of blade blanks for gas turbine engines made of an alloy based on orthorhombic titanium aluminide, including stamping of blade blanks at a temperature below the transformation temperature (Tf), characterized in that, before stamping, the blank of blades is preheated to a temperature above the temperature Tf from more than 0 to 100 °C, maintained for at least 0.5 hour, the forging of blanks of blades is carried out with a degree of deformation of at least 50% at a temperature below the temperature Tpp by 50-200°C, after which heat treatment is carried out, including two stages, the first of which is hardened at a temperature below the Tpp temperature by 50-150°C with an exposure of at least 0.5 hours, and on the second - aging at a temperature below the Tpp temperature by 200-300°C with an exposure of 1 to 36 hours.

Images