RU2009251C1 - Columbium-base alloy and method for production thereof - Google Patents

Abstract

FIELD: nonferrous metallurgy. SUBSTANCE: columbium-base alloy contains columbium, titan, aluminium, vanadium, zirconium, and carbon in the proportion of (in % by mass): titan 29-32.5; aluminium 6.7- 7.7; vanadium 2-4; zirconium 0.5-1.5; carbon 0.07-0.15; columbium - the balance. The novelty is the introduction in the alloy of carbon in the proportion of 0.07-0.15% . The method for production of the alloy includes smelting, deformation, roasting, ageing, and mechanical-and-thermal treatment. The novelty are the roasting which is carried out prior to ageing at 930-1000 C for 1-5 hours, and the mechanical-and-thermal treatment which is carried out after the ageing in vacuum or in inert atmosphere at 500-700 o C for 20-100 hours under a stress ensuring the short-time residual deformation of 0.1-0.3 of the uniform elongation at these temperatures. EFFECT: increased reliability and service life, reduced sensitivity to stress concentrators. 2 cl, 1 tbl

Description

 The invention relates to the metallurgy of alloys, namely, niobium-based alloys, designed to operate under oxidizing conditions at elevated temperatures in components and parts of aerospace engineering.

 Known alloy BH7 containing niobium, titanium and aluminum with a ratio of ingredients, wt. %: titanium 40-45; aluminum 5-7; niobium rest [1].

A method of producing this alloy, comprising the smelting, the deformation of the ingot at temperatures 1050-1100 ^{° C,} repeated deformation at temperatures of 1000-1050 ^{° C} and annealing [1].

However, the known alloy after receiving by the known method has the structure of a β-solid solution and is characterized by low strength (σ _in ²⁰ = 650-700 MPa, σ _in ⁷⁰⁰ = 190-210 MPa). It is not able to work in heavily loaded parts and is usually used not independently, but as heat-resistant plating on niobium alloys.

Known alloy system niobium-titanium-aluminum, also containing hafnium at a ratio of ingredients, at. % (wt.%): Titanium 32-45 (18.4-29.3) Aluminum 3-18 (2-6.6) Hafnium 8-15 (17.1-36.4) Niobium The rest [2]
A known method of producing this alloy, including the production of powder by rapid crystallization methods and its subsequent compaction (hot isostatic pressing) [2].

However, this alloy after obtaining by the known method also has the structure of a β-solid solution, therefore its strength properties at room and moderate temperatures are low (σ _at ²⁰ = 882 MPa, σ _at ⁷⁶⁰ = 517 MPa). In addition, alloying with hafnium makes the alloy heavier (γ = 6.57 g / cm ³ ).

Known alloy containing niobium, titanium, aluminum, as well as vanadium and zirconium in the following ratio of components, wt. %: Titanium 29-32.5 Aluminum 6.7-7.7 Vanadium 2-4 Zirconium 0.5-1.5 Niobium Else [3]
- prototype (TU1-809-317-87).

 A known method of producing this alloy, including smelting, deformation and aging [3].

4= 0,5 г/м²x ч), подвержен термоупрочнению, в термоупрочненном состоянии высокопрочен (σ_в ²⁰≥ 1050 МПа), характеризуется высоким уровнем и стабильностью механических свойств при температурах до 700^оС вклю-чительно (σ_в ⁷⁰⁰≥ МПа, σ₁₀₀ ⁶⁰⁰ ≈ 600 МПа, σ₁₀₀ ⁷⁰⁰ ≈ 300 МПа).A well-known alloy after obtaining by a known method has a set of properties that allow it to be considered as a promising material for aerospace engineering. It is light (γ≅ 5.9 g / cm ³ ), heat-resistant (V

4 = 0.5 g / m ² x h) is exposed to heat strengthening, a thermohardening vysokoprochen state (σ 1050 ≥ ^₂₀ MPa), is characterized by high stability and mechanical properties at temperatures up to 700 ^{° C,} including The considerably (σ ≥ ^₇₀₀ MPa, σ ₁₀₀ ⁶⁰⁰ ≈ 600 MPa, σ ₁₀₀ ⁷⁰⁰ ≈ 300 MPa).

However, the known alloy has a high sensitivity to stress concentrators during prolonged operation in aggressive (oxidizing) environments. For example, when tested in air at 600 ^{° C} for long-term strength limit 100 h determined on samples in the notch, only 40% of similar characteristics, determined on smooth samples. At a temperature of 700 ^about C, this ratio is 60%. Cases of early destruction of samples of a known alloy are associated with increased sensitivity to notching; therefore, it is not recommended to use it in parts and structures of responsible designation.

 An alloy based on niobium is proposed, containing titanium, aluminum, vanadium, zirconium and carbon in the following ratio of components, wt. %: Titanium 29-32.5 Aluminum 6.7-7.7 Vanadium 2-4 Zirconium 0.5-1.5 Carbon 0.07-0.15 Niobium The rest [4].

The difference between the proposed alloy from the known one is that the alloy additionally contains carbon in the following components, wt. %: Titanium 29-32.5 Aluminum 6.7-7.7 Vanadium 2-4 Zirconium 0.5-1.5 Carbon 0.07-0.15 Niobium Else
A method for producing alloy comprising melting, annealing at a temperature of 930-1000 ^C for 1-5 hours, and aging of the mechanical-thermal treatment in vacuum or in an inert atmosphere at 500-700 ^{° C} for 20-100 hours under voltage, providing short-term residual deformation of 0.1-0.3 of the uniform elongation at these temperatures.

 The proposed alloy and the method of its production can increase the service life and reliability of parts and products by reducing sensitivity to stress concentrators. Moreover, the additional introduction of carbon impedes the penetration of oxygen into the volumes where plastic and microplastic flow occurs (in the zones near the surface of the sample, at the top of the notch, in front of the growing crack), and increases the cohesive strength of the material. Carrying out annealing before aging helps to reduce the intensity of oxygen saturation during operation by creating a more perfect crystallized structure. Carrying out the mechanical-thermal treatment causes strain aging and thus complicates the local plastic flow in critical areas during operation.

 To obtain the alloy, its ingredients were taken (niobium NBSh-00, titanium VT1-00, aluminum AD1-00, iodide zirconium, electrolytic vanadium, graphite fabric) in the proportions corresponding to the proposed alloy, the ultimate compositions and the prototype alloy.

 The ingredients of the alloy were remelted by the GRE + VDP method into ingots with a diameter of 115 mm.

= 0,2-0,3 с^-1) и сортовой прокаткой (t_пр = 1100^оС, ε = 92% ,

= 2-3 с^-1), прутки отжигали, затем выполняли старение по режиму 800^оС, 25 ч, после которого проводили механико-термическую обработку. Отжиг выполняли на воздухе в печах сопротивления по режимам 930^оС, 5 ч; 950^оС 3 ч; 1000^оС 1 ч; 900^оС 7 ч и 1020^оС 0,5 ч.The alloy obtained by the proposed method: after melting ingots deformipovali on compression bars (t _ave = ^{1200 °} C, ε = 77%;

= 0.2-0.3 s ^-1 ) and high-quality rolling (t _ol = 1100 ^о С, ε = 92%,

= 2.3 s ^-1) rods annealed, and then aging was performed under the regime ^of 800 C, 25 h, after which was carried mechanical-thermal treatment. Annealing was performed in air at 930 ^C. regimes resistance furnaces, 5 h; 950 ^{° C} for 3 hours; 1000 ^about With 1 h; 900 ^{° C} for 7 hours and 1020 ^C for 0.5 hours.

Annealing was performed in air at 930 regimes resistance furnaces ^C for 5 hours; 950 ^{° C} for 3 hours; 1000 ^about With 1 h; 900 ^{° C} for 7 hours and 1020 ^C for 0.5 hours.

The mechanical-thermal treatment was carried out in vacuum in an apparatus for long-term heat-resistant tests. The operation consisted of holding the material at elevated temperature for a certain time under voltage. Temperature-time regimes of MTO-500 ^о С 20 h, 600 ^о С 50 h and 700 ^о С 100 h - corresponded to the proposed production method, and 450 ^о С 15 h and 750 ^о С 108 h - to its beyond limits.

 To determine the required MTO stress, preliminary control tensile tests of the control samples were carried out at a temperature of the subsequent mechanical-thermal treatment with the recording of stress-strain diagrams. The diagram graphically determined the magnitude of the stresses providing a deformation of 0.1-0.3 of the uniform elongation.

Voltage needs for smooth samples are as follows: at ⁵⁰⁰ ° C - 1200 MPa, which provides short term residual strain 0.1 of uniform elongation values; at 600 ^о С - 1120 MPa, which provides a short-term residual deformation of 0.2 of the uniform elongation; at 700 ^о С - 1060 MPa, which provides a short-term residual deformation of 0.3 of the uniform elongation.

 During the mechanical-thermal treatment of notched specimens taking into account the stress concentration at the notch apex (K ≈ 4) to ensure the same residual deformation as on smooth specimens, the stresses were reduced by 4 times.

 The compositions of the alloys and methods for their preparation are summarized in the table. The proposed method and the method of its production correspond to paragraphs. 1-3, transcendental compositions and modes of production - paragraphs. 4 and 5.

The alloy taken as a prototype prepared by the known method, ie. E. After the melting was carried deformation (pressing, followed by rolling on the profiled bars 14 mm in diameter) and aging at 800 ^{° C} regime 25 (n. 6 table).

Prepared as described by the material to evaluate its reliability in operation were tested for rupture strength at temperatures of the proposed operation 600 and 700 ^C. During the tests evaluated the sensitivity to stress concentrators, which compared the results of smooth test samples in accordance with GOST 10145-81 (diameter working part 5 mm, with a gauge length of 25 mm) and specimens notched OST 90294-80 (diameter 5 mm incision, the incision is - 7 mm, apex angle notch disclosure - ^60, the notch tip radius - 0.15 mm). The test results are shown in the table.

 As can be seen from the table, the sensitivity to stress concentrators during prolonged operation in air at elevated temperatures for the alloy of the proposed composition with the proposed method for its preparation is significantly (2 or more times) reduced in comparison with the prototype alloy obtained by the known method. At the same time, the reliability of structures increases, and as a result, their service life increases.

 Thus, the test results showed that the proposed alloy and the method of its production will allow the use of very promising light, high strength, heat-resistant and heat-resistant material in aerospace parts for critical purposes. (56) 1. TU 1-809-307-88 "Deformable niobium alloys of grades BH2AEM, BH3, BH4 and LN1".

 2. US patent N 4956144, CL. C 22 C 30/00, 1990.

 3. TU-1-809-317-87 "Alloy titanium-niobium grade VN-10."

 4. Collection "Metal science and heat treatment of titanium and heat-resistant alloys." M.: VILS, 1991, p. 358-365.

Claims (1)

1. An alloy based on niobium containing titanium, aluminum, vanadium and zirconium, characterized in that it additionally contains carbon in the following ratio of components, wt. %:
Titanium 29 - 32.5
Aluminum 6.7 - 7.7
Vanadium 2 - 4
Zirconium 0.5 - 1.5
Carbon 0.07 - 0.15
Niobium rest
2. A method of producing an alloy based on niobium, including melting, deformation and aging, characterized in that before aging annealing is carried out at 930 - 1000 ^o C for 1 to 5 hours, and after aging, they are subjected to mechanical-thermal treatment in a vacuum or inert medium at 500 - 700 ^o C for 20 - 100 hours under stress, providing a short-term permanent deformation of 0.1 - 0.3 of the uniform elongation at these temperatures.

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