DE2052252A1 - Nickel alloy - Google Patents

Description

The invention relates to a precipitation hardenable nickel alloy having high toughness.

In the case of high-temperature alloys, such as those used as a material for steam or gas turbines, the difficulty has hitherto always arisen in ensuring adequate ductility without impairing the other material properties such as creep strength, creep resistance and corrosion resistance. This is especially true for alloys with a low chromium content. Thus DAB such alloys was found at 600 to 900 ⁰ C a toughness drop subject, which is often the cause of errors λ at portions which are subjected at this temperature.

The aforementioned disadvantages occur in the case of the invention Nickel alloy with 0 to 14.5% chromium, 0 to 2096 Cobalt, 0 to 2596 tungsten, 0 to 596 iron, 0 to IO96 Molybdenum, 4 to 1296 titanium and aluminum, 0 to 1296 Tantalum, 0 to 6j6 niobium, 0 to 396 vanadium, 0 to 1.596 Zirconium and a total of 0.005 to 0.1596 at least one the elements yttrium, lanthanum, thorium and cerium, the remainder nickel including impurities caused by the smelting

109818 / 150Ö

good, not up. The alloy according to the invention preferably contains 0.02 to 0.12% yttrium or lanthanum, for example 0.05 to 0.10%, more preferably 0.02 to 0.07%. If the alloy contains cerium, its content is preferably from 0.005 to 0.07%. In addition, the alloy according to the invention can contain up to 0.5% carbon, up to 0.5% Manganese, up to 0.3% silicon and up to 0.3% boron.

The alloy according to the invention is normally in a vacuum; for example melted in a vacuum induction furnace, where yttrium, lanthanum, thorium or cerium are added after melting and the melt is preferred is cast under inert gas. The alloy can, however, also before the addition of yttrium, lanthanum, thorium or cerium in a vacuum, for example by stirring the melt for a long time in a vacuum induction furnace, for example by stirring for 15 to 60 minutes at 100 to 160 ° C, preferably at about 1500 ° C and a pressure of 100 microns or less, preferably 10 microns or less, but better of at most 2 microns, followed by the introduction of inert gas, for example argon, at moderate Pressure of, for example, 100 mm QS fine and then the yttrium, lanthanum, thorium and / or cerium are added. Preferably the melt is refined for 30 minutes at a pressure of about 1 micron in a vacuum induction furnace, its crucible is completely within the induction winding and only one to two thirds with it vigorously moving melt is filled. The upper part of the coil is located above the bathroom mirror, whereby the stirring effect is increased when the furnace is in operation.

The object on which the invention is based is primarily to reduce the aforementioned drop in ductility

1098 18/1506

to avoid, but also the ductility other temperatures as well as the other mechanical properties, in particular the creep rupture strength and improve creep behavior. To demonstrate the higher ductility, the effect of yttrium, Lanthanum, thorium and cerium in various test alloys with those given in Table I below Compositions studied.

109818/1506

Table I.

Alloy C Cr Co Mo W Nb Ta Ti Al Zr B Fe Ni

(96) 00 06) 06) 06) 06) 06) 00 00 (96) (96) (96) (96)

1 0.1 8.1 9.9 6.05 - - 4.1 0.95 5.75 0.12 0.019 - remainder

2 0.1 10.1 10.0 4.05 - - 3.65 5.8 0.14 0.015 - ⁿ

3 0.13 5.8 - 2.02 10.9 1.40 - - 6.7 0.13 0.018 - »

4 0.05 12 4.7 - 2 - 0.65 6.0 0.10 0.012 - »

5 0.10 12.2 - 4.2 - 2.3 - 0.8 6.3 0.12 0.018 - «

6 0.15 9.1 10.0 2.2 9.8 - 1.5 1.3 5.5 0.05 0.018 «

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In each of the tests, 50 kg melts were melted down in a 55 kg 3 kHz vacuum induction furnace and held at 1500 ^° C. under a pressure of about 1 micron for 30 minutes. The melts were then poured into 10 kg bars in the usual way. The bars were divided into 4 kg pieces and remelted in a 10 kg 4 kHz vacuum induction furnace in the usual manner. Various amounts of yttrium, lanthanum, thorium and cerium were added to the 4 kg melts after introducing argon under a pressure of mm QS and the melts were poured into heated refractory molds to form test wedges. For comparison purposes i

Magnesium added to a test melt of alloy 1.

Samples were worked out from the wedges and short tests to determine the tensile strength and creep behavior and subjected to creep rupture strength.

The test results are compiled in Tables II and III below and show that the lanthanum, Alloys containing yttrium, thorium or cerium in an amount of 0.01 to 0.14% have an increased elongation and in some cases also the other mechanical properties such as creep toughness and creep strength speed at intermediate temperatures of, for example, 760 ° C and the tensile strength have been improved.

109818/1506

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The data in Table II show that some impairment in some cases resulted in the Zeitstahdverhaltens at ■ 980 ⁰ C. In general, however, it has been found that the slight impairment of the creep rupture behavior with the yttrium-containing alloy is somewhat less than with the lanthanum-containing alloy, for which reason the yttrium is to be preferred as an alloy additive.

The data in Table III relate to tests on alloys containing thorium, cerium, magnesium and mischmetal with 6596 cerium and 3596 lanthanum. Thorium has a similarly beneficial effect as yttrium, but with a slight impairment of the creep behavior at 98O ⁰ C, while the Zer has a favorable effect on the tensile and creep behavior at 760, but has an adverse ^{effect on the creep behavior at 980 0} C and the magnesium has all of the effects mentioned mechanical properties impaired. The use of mixed metal provides an inexpensive way for alloying with lanthanum is, although the mixed metal contains about twice the amount of cerium and, although a favorable effect on the ductility at 76o C, however, adversely affects the creep behavior at 980 ⁰ C.

Examples of other alloys whose elongation in the tensile test according to the invention by the addition of yttrium, • Lanthanum, thorium and / or cerium can be improved are listed in Table IV below.

Table IV

Legle- C Cr Co Mo W Nb Ta Ti Al Zr B Fe Ni tion (#) (J6) (96) (*) (96) (96) (96) (96) (96) (#) (96) (96) (96)

7th O ,1 3 12th 3 - 19 - 3 - 5, 75 0.35 0.03 - rest 8th O , 08 - 15th , 5 8th β - 6 0.05 0.10

109818/1506

Claims (7)

International Nickel Limited, Thames House, Millbarik, London. S. ¥. 1, UK claims; 1. Nickel alloy, consisting of 4 to 12% titanium and aluminum, 0 to 14.5% chromium, 0 to 20% cobalt, 0 to 25% tungsten, 0 up to 10% molybdenum, 0 to 12% tantalum ,. 0 to 6% niobium, 0 to 5% iron, 0 to 3% vanadium, 0 to 1.5% zirconium, up to 0.5% carbon, up to 9.5% manganese, up to 0.3% silicon, up to 0.3% boron, a total of 0.005 to 0.15% of at least one of the elements yttrium, lanthanum, thorium or cerium, the remainder including those caused by melting Impurities nickel. 2. Alloy according to claim 1, but containing 0.005 to 0.15% yttrium and / or lanthanum. 3. Alloy according to claim 2, but containing 0.05 to 0.1% yttrium and / or lanthanum. 4. Alloy according to claim 2, but containing 0.02 to 0.07% yttrium and / or lanthanum. Λ 5. The alloy of claim 1 but containing 0.005 to 0.07% cerium. 6. Use of an alloy according to claims 1 to 5 as Material for objects that must have a high degree of elongation. 1 0981 8/1 506 - ίο - 7. Verwendlang partially a temperature of 600 to 900 ⁰ C are subjected to an alloy according to claims 1 to 5 as a material for articles which, like steam or gas turbine parts and must have a high tensile elongation at this temperature. 109818/1506