RU2800270C1 - Method for manufacturing gas turbine engine blades from intermetallic alloy based on orthorhombic titanium aluminide - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to the pressure treatment of intermetallic alloys based on orthorhombic titanium aluminide. The method of manufacturing blanks of blades of gas turbine engines from intermetallic alloys based on orthorhombic titanium aluminide includes stamping of blanks of blades at a temperature below the transformation temperature (Ttt). Before stamping, the blade blanks are preheated to a temperature higher than the Ttt temperature by no more than 100°C, exposed for at least 0.5 hours, subjected to all-round forging at a temperature below Ttt by 50-150°C while carrying out at least 3 passes with a change in the axis of deformation by 90° and a degree of deformation of at least 40% per pass, the last pass being carried out with a degree of deformation of at least 50%. 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°С, 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°С with an exposure of at least 0.5 hours is carried out, and at the second of aging at a temperature below T_tt 200-300°С with an exposure of 1 to 36 hours, where T_tt is the transformation temperature ↔α₂.

EFFECT: obtaining high mechanical properties of blade blanks.

1 cl, 2 dwg, 6 ex

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. %) с целью получения прутковых заготовок [Патент РФ № RU 2 644 830 C2 от 26.06.2017 «Способ изготовления прутковых заготовок из сплавов на основе интерметаллида титана с орто – фазой»], включающий нагрев и предварительную деформацию слитка с получением заготовки, промежуточную и окончательную деформацию заготовки и заключительную термообработку, отличающийся тем, что промежуточную деформацию заготовки осуществляют от 2 до 5 осадок со степенью 25-40%, совмещенных с прессованием со степенью 55-70%, при этом нагрев заготовки перед первой из промежуточных деформаций проводят ступенчато до температуры Т _пп +(100-200)°С, где Т _пп температура β↔α ₂ превращения с выдержкой 2-3 часа, а каждую последующую из промежуточных деформаций проводят при температуре на 50-100°С ниже предыдущей с выдержкой на 0,5-1 час меньше, чем на предыдущей, а последнюю из промежуточных деформаций проводят при температуре Т _пп -(20-50)°С, причем окончательную деформацию заготовки осуществляют со степенью не более 30% при Т _пп -(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 titanium aluminum alloy based on ortho-phase"], which consists in multi-stage deformation of the ingot with heating above and then below the polymorphic transformation temperature (T _pp ) and subsequent thermal processing. 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 temperatures 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 12/08/2021 "Method of processing rods from ortho-titanium alloys to obtain gas turbine engine compressor blades" in order to improve mechanical characteristics, which includes heating the rod to 1100 ° C, flattening with a degree of deformation of at least 0.5, reheating to 1100°C and extrusion of the blank 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 blades of gas turbine engines from an intermetallic 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 provide high mechanical properties of blanks for blades of gas turbine engines from an intermetallic alloy based on orthorhombic titanium aluminide: σ _0.2 ²⁰ =1000-1200 MPa; σ _B ²⁰ =1150-1250 MPa; δ ²⁰ \u003d 5-8%; ψ ²⁰ =3-5%; σ _0.2 ⁶⁵⁰ = 850 MPa; σ _B ⁶⁵⁰ =1000 MPa; δ ⁶⁵⁰ = 9%; ψ ⁶⁵⁰ =7%; KCU ²⁰ =7.0 J/cm ² , time to fracture at T=650°C and σ=380 MPa up to 200 hours, due to the proposed method of isothermal stamping and subsequent heat treatment,

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

The novelty and inventive level of the proposed invention lies in the introduction of an additional operation of preliminary deformation-heat treatment in the form of isothermal forging of blanks of an intermetallic alloy based on orthorhombic titanium aluminide before stamping, as well as in carrying out isothermal stamping of blanks of blades at a temperature significantly lower than T _pp , 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 implementation of the invention on the example of an intermetallic alloy based on orthorhombic titanium aluminide VIT1. Temperature β↔α ₂ transformation (hereinafter T _PP ) was determined using differential scanning calorimetry and amounted to 1100°C. 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. After that, forging is carried out at a temperature below T _pp by 50-150°C with at least 3 passes with a change in the deformation axis by 90° and a degree of deformation of at least 40% per pass. 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, cooling in air;

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

The invention is characterized in the following images.

Fig. 1 – Microstructure of VIT1 alloy billet after deformation-thermal and heat treatment according to the regime: annealing T=1100°C, holding for 0.5 hour cooling in air; forging at a temperature of 950°C with at least 3 passes with a change in the axis of deformation by 90° and a degree of deformation of at least 40% per pass; 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).

Fig. 2 - Table "Mechanical properties of the resulting 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 intermetallic alloy based on orthorhombic titanium aluminide VIT1. The obtained alloys were mechanically tested using the following setups: universal electromechanical testing machine Instron 5882; pendulum hammer Instron SL-1M #SIK 5711; ATS Creep Tester 2330 Creep and Tensile Testing Machine.

Example 1

The deformation-heat treatment of intermetallic alloy blanks 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. Next, the workpieces were subjected to isothermal forging at 950°C with 3 passes with a degree of deformation per pass of 40%. 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 1000°C, holding for 4 hours, hardening in air; aging at 850°C, exposure 6 hours. The resulting microstructure is shown in Fig. 1. The results of mechanical tests are presented in the table in FIG. 2.

Example 2

The deformation-heat treatment of intermetallic alloy blanks 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 1050°C with 3 passes with a degree of deformation per pass of 40%. 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: heating to 1000°C, holding for 0.5 hours, hardening in air; aging at 800°C, exposure 36 hours. The results of mechanical tests are presented in the table in Fig. 2.

Example 3

The deformation-heat treatment of intermetallic alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1100°C and kept for 0.5 hours, followed by cooling in air. Next, the workpieces were subjected to isothermal forging at 950°C with 3 passes with a degree of deformation per pass of 40%. 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: heating to 1000°C, holding for 0.5 hours, hardening in air; aging at 900°C, exposure 1 hour. The results of mechanical tests are presented in the table in Fig. 2.

Example 4

The deformation-heat treatment of intermetallic alloy blanks 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 950°C with 3 passes with a degree of deformation per pass of 40%. The workpieces were subjected to isothermal forging at 950°C with a degree of deformation of 50%. After that, the workpieces were subjected to heat treatment: heating to 1000°C, holding for 0.5 hours, hardening in air; aging at 800°C, exposure 6 hours. The results of mechanical tests are presented in the table in Fig. 2.

Example 5

The deformation-heat treatment of intermetallic alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1000°C and kept for 4 hours, followed by cooling in air. The workpieces were subjected to isothermal forging at 1000°C with 3 passes with a degree of deformation per pass of 40%. The blanks were subjected to isothermal forging at 1050°C with a degree of deformation of 50%. After that, the workpieces were subjected to heat treatment: heating to 1050°C, holding for 0.5 hours, hardening in air; aging at 800°C, exposure 6 hours. The results of mechanical tests are presented in the table in Fig. 2.

Example 6

The deformation-heat treatment of intermetallic alloy blanks based on VIT1 orthorhombic titanium aluminide has been carried out. Before deformation, the workpiece was heated to T=1000°C and kept for 4 hours, followed by cooling in air. The workpieces were subjected to isothermal forging at 1000°C with 3 passes with a degree of deformation per pass of 40%. The workpieces were subjected to isothermal forging at 1000°C with a degree of deformation of 50%. After that, the workpieces were subjected to heat treatment: heating to 950°C, holding for 2 hours, hardening in air; aging at 800°C.

Additionally, the alloy obtained according to example 1 was tested for impact strength KCU20=7.0 J/cm ² and long-term strength: time to failure at T=650°C and σ=380 MPa up to 200 hours.

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 intermetallic alloy based on orthorhombic titanium aluminide VIT1: σ _0.2 ²⁰ =1000-1200 MPa; σ _B ²⁰ =1150-1250 MPa; δ ²⁰ \u003d 5-8%; ψ ²⁰ =3-5%; σ _0.2 ⁶⁵⁰ = 850 MPa; σ _B ⁶⁵⁰ =1000 MPa; δ ⁶⁵⁰ = 9%; ψ ⁶⁵⁰ =7%.

Claims (1)

A method for manufacturing blanks of blades for gas turbine engines from intermetallic alloys based on orthorhombic titanium aluminide, which includes forging blanks of blades at a temperature below the temperature of transformation (Tm), characterized in that before stamping, blanks of blades are preheated to a temperature above Tmt by no more than 100°C, held for at least 0.5 hour, subjected to all-round forging at a temperature below Tmt by 50-150°C with at least 3 passes with a change in the axis of deformation by 90° and a degree of deformation of at least 40% per pass, and the last pass is carried out with a degree of deformation of at least 50%, then the blanks of blades are stamped with a degree of deformation of at least 50% at a temperature below Tfm by 50-200°C, after which heat treatment is carried out, including two stages, the first of which is quenched at a temperature below the temperature of Tfm by 50-150°C with a holding time of at least 0.5 hours, and on the second - aging at a temperature below Tpp by 200-300°C with exposure from 1 to 36 hours, where Tpp is the temperature β↔α₂ transformations.