RU2039112C1 - Titanium-base heat resistant alloy - Google Patents

Abstract

FIELD: heat resistant alloys. SUBSTANCE: alloy has, wt.-% aluminium 6.3-7.0; zirconium 3.5-4.5; tin 2.2-3.5; niobium 0.5-1.5; molybdenum 0.4-1.0; silicon 0.1-0.2; carbon 0.02-0.1; oxygen 0.05-0.12 at the total content of aluminium and tin 9.2-9.7% and silicon and oxygen 0.22-0.25% and titanium the rest. Strength limit of proposed alloy is more that known one by 15-20 kgf/cm² at 20 C and 7-10 kgf/mm² at 550 C. Alloy shows increased specific strength at indicated temperatures. EFFECT: enhanced quality of proposed alloy. 1 tbl

Description

 The invention relates to metallurgy, and in particular to the development of heat-resistant alloys based on titanium, intended for the manufacture of parts operating at elevated temperatures.

 The invention can be used for the manufacture of parts in the aviation industry, mechanical engineering and other industries.

Among titanium alloys having improved heat resistance at the operating temperatures 500-600 ^{° C,} are known overseas IMI 829 alloy (UK patent N 1492262), IMI 834 (European Patent N 0107419), domestic alloys VT25U (SU, N 533050) and VT18U (ed. St. N 473757). All these alloys have drawbacks: IMI 829 alloy has lower strength values at 20 ^о (σ _at 95 kgf / mm ² ) and 540 (σ _at 65 kgf / mm ² ), IMI 834 alloys and according to the author. St. N 473757 have fairly high heat resistance characteristics, but low thermal stability (CCT).

The closest in technical essence to the claimed is an alloy based on titanium, which contains the ingredients in the following ratio, wt. aluminum 5.0-6.0 zirconium 2.0-4.0 tin 2.5-4.5 silicon 0.2-0.4 niobium 0.75-1.25 molybdenum 0.1-0.6 titanium else
This alloy has insufficiently high tensile strengths. In addition, in the prototype there is no restriction on the total content of aluminum and tin, silicon and oxygen, as a result of which the alloy has lower thermal stability and lower values of the characteristics of KST and K _IC .

 The technical problem is to develop an alloy having the optimal combination of heat resistance and thermal stability, as well as fracture characteristics. The task is achieved due to the fact that the alloy additionally contains carbon and oxygen in the following ratio of ingredients, wt. aluminum 6.2-7.0 zirconium 3.5-4.5 tin 2.2-3.5 niobium 0.5-1.5 molybdenum 0.4-1.0 silicon 0.1-0.2 carbon 0 , 02-0.1 oxygen 0.05-0.12 with a total aluminum and tin content of 9.2-9.7% silicon and oxygen 0.22-0.25% titanium the rest.

 The introduction of carbon and oxygen within the indicated limits contributes to an increase in the polymorphic transformation temperature, which allows heating processes to be carried out during deformation and heat treatment at higher temperatures, without leading to grain growth, which makes it possible to obtain an optimal structure providing a high level of strength and heat-resistant characteristics, ductility and low cycle endurance.

 In addition, carbon within the specified limits increases the limit of short-term strength and long-term strength, without reducing ductility.

Oxygen in the amounts indicated increases the tensile strength at ^about 20. A decrease in oxygen of less than 0.03% does not provide the required strength, and an increase in it in an alloy of more than 0.12% leads to a decrease in impact strength, creep limit.

Limiting the total content of aluminum and tin to 9.2–9.7% and silicon + oxygen to 0.22–0.25% helps to limit the release of particles of intermetallic phases α ₂ and silicides TiZr ₅ Si ₃ , which are responsible for increasing heat resistance and reducing thermal stability and reliability characteristics of KST and K _IC .

As a result of the proposed alloying, an optimal combination of high heat-resistant properties up to 600 ^° C with a sufficiently high thermal stability and reliability characteristics of KST and K _{IC is} obtained, which helps to increase the service life of parts.

For laboratory research of the experimental alloy used semi-finished products (rods with a diameter of 12-35 mm) in the annealed state of the following composition (wt.):
Alloy 1: 6.2 Al 4.5 Zr 3.5 Sn 1 Nb 0.8 Mo 0.2 Si 0.02 C 0.05 O ₂ Ti, Σ Al + + Sn 9.7, Σ Si + O ₂ 0.25.

Alloy 2: 6.5 Al 4 Zr 3.0 Sn 0.5 Nb 0.15 Si 0.4 Mo 0.06 C 0.03 O ₂ Ti, Σ Al + + Sn 9.5, Σ Si + O ₂ 0.23.

Alloy 3: 7.0 Al 3.5 Zr 2.2 Sn 1.5 Nb 1.0 Mo 0.1 Si 0.1 C 0.12 O ₂ Ti, Σ Al + + Sn 9.2, Σ Si + O ₂ 0.22.

Alloy 4: 6.1 Al 3.4 Zr 2.1 Sn 0.4 Nb 0.3 Mo 0.009 Si 0.01 C 0.04 O ₂ Ti.

Alloy 5: 7.1 Al 4.6 Zr 3.6 Sn 1.6 Nb 1.1 Mo 0.23 Si 0.11 C 0.13 O ₂ Ti.

Alloys were smelted in a vacuum arc furnace by the double remelting method. The rods were subjected to heat treatment according to the regime: 950 ^о С 1 h, air cooling + 600 ^о С 5 h, air cooling.

 Comparative properties of the proposed (N 1-5) and known (N 6) alloys are shown in the table.

Presented in the table show that the proposed alloy surpasses known by tensile strength at ²⁰ ° C for 15-20 kgf / mm ² and at 550 ^{° C} for 7-10 kgf / mm ^2. Alloys are close in heat resistance. The proposed alloy has a higher specific strength at these temperatures compared with the known.

The use of the proposed alloy will reduce the weight of the product and increase its technical data. A high level of heat resistance and thermal stability will allow us to recommend the alloy for operation at temperatures up to 500-600 ^o C.

Claims (1)

 HEAT-RESISTANT ALLOY ON THE BASIS OF TITANIUM, containing aluminum, tin, zirconium, molybdenum, niobium, silicon, characterized in that it additionally contains carbon and oxygen in the following ratio of components, wt. Aluminum 6.2 7.0
Tin 2.2 3.5
Zirconium 3.5 4.5
Niobium 0.5 1.5
Molybdenum 0.4 1.0
Silicon 0.1 0.22
Carbon 0.02 0.1
Oxygen 0.05 - 0.12
Titanium rest
with a total content of aluminum and tin of 9.2 to 9.7 wt. and silicon and oxygen 0.22 0.25 wt.

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