DE1483235A1 - Use of a nickel-chromium alloy - Google Patents

Description

4 Düsseldorf, October 7, 1968

Km ^ Cecilienallee 76 III / Ka.

Dr. Ing.Eichenberg Dipl.-f ng. Sauerfand

Dr, Ing.König P H 83 235.0

International Nickel Limited, Thames House, Millbank,

London, S.W, 1, England

"Use of a nickel-chromium alloy"

The invention relates to the use | Formation of a nickel-chromium alloy, consisting of 5 to 10 $ chromium, 7 to 16 $ tungsten, 0 to 5 $ molybdenum, 0 to M> niobium, 2 to 8 $ aluminum, less than 0.03 $ carbon, 0 to 15ε Zirconium, 0 to 0.08 $ boron, the remainder including impurities caused by the melting nickel

In the development of alloys for cast rotors and blades for gas turbines, the main focus so far has primarily been on high creep strength. Although many known alloys have sufficient creep strength, their notched impact strength, especially \ when exposed for long periods to high temperatures, insufficient. In addition, the known nickel-chromium alloys have poor fatigue strength.

In US Pat. No. 2,920,956, among other things, nickel-chromium alloys with 0 to $ 0.5 Carbon, $ 4 to $ 30 chromium, $ 0 to $ 15 tungsten, $ 0 to

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New documents {Art 7 ί T Abs. 2 Nr. 1 Satt 3 dee amendments. v. 4.9.1967}.

-Z-

30 $ molybdenum, 0 to 6 $ niobium, Q to 8 $ aluminum, 0.005 to 0.5 $ zirconium, 0 to 0.05 $ boron and 35.0 to 90, nickel, which also contain cobalt, titanium and vanadium can. The known alloys are suitable as a material for high-temperature-resistant parts of jet engines, gas turbines or the like, since they have high strength, in particular creep strength, and should be resistant to oxidation. The high creep strength is due to the addition of boron and / or zirconium; Nevertheless, the alloys have ⁰ G at 95O and a load of 23.6

ο
kg / mm a service life well below 30 hours.

The object on which the invention is based is based on the known heat-resistant nickel-chromium alloys to create a material which, in addition to high creep strength at high temperatures, also has good notched impact strength and fatigue strength. This object is achieved according to the invention by the proposal, as a material for the production of cast iron pieces, which, like turbine rotors and blades, ^{have a minimum service life of 30 hours in addition to high impact strength and fatigue strength at 95O 0} C and a load of 23.6 kg / mm must use a nickel-chromium alloy made up of $ 5 to $ 10 chromium, $ 7 to $ 16 tungsten, $ 0 to $ 5 molybdenum, $ 0 to $ 4 niobium, with a total of tungsten, molybdenum, niobium and 2 / 3 of the chromium content consists of 17.5 to 20.5 $, 2 to 8 $ aluminum, less than 0.03 $ carbon, 0 to 1 $ zirconium, 0 to 0.08 $ boron, the remainder including impurities caused by the smelting process nickel.

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mm * \ mm

The main impurities can be iron, silicon and manganese, the total content of these elements should be as low as possible and not exceed $ 3. The iron content preferably does not exceed $ 0.5, the silicon content $ 0.3 and the manganese content does not exceed $ 0.3. Small amounts of tantalum are generally contained in commercially available niobium. Niobium is traded as an alloy with nominally 40 $ nickel and 60 $ niobium, with a tenth of the nominal niobium content of this alloy often consisting of tantalum. The proposed alloy can therefore contain tantalum, the tantalum being regarded as a part of the niobium content.

To the improved notched impact strength and To maintain fatigue strength, it is especially important to keep the carbon content below $ 0.03, for example in the range of $ 0.001 to $ 0.0275. The carbon content is preferably so as low as possible, for example less than $ 0.02 or even less than $ 0.01, although traces of carbon are always present. To achieve the best possible creep strength, the Chromium content does not exceed $ 9 and is preferably between $ 5 and $ 7. The creep rupture strength |

also depends on the total content of tungsten, molybdenum and niobium, and for a certain chromium content there is an optimal value for the total content of these elements at which a very high long-term stability is achieved. For alloys with chromium Sfo to scored the best creep strength when the ^r Gfesamtgehalt of tungsten, molybdenum and niobium is about $ 15. With increasing Ohrora levels increases

909 8 1 line

the optimal total content of tungsten, molybdenum and niobium and for alloys with 9 $ chromium is 1 In general, the creep rupture strength of the alloys falls sharply off when the value of the equation

+ JiNb + 2/3

falls below 17 »5 or exceeds the value of 20.5 ·

The aluminum content of the alloy is also important, and for alloys with a level of concern Basic composition leads to the change dee Aluminum content has a noticeable influence on the creep rupture strength. The best creep strength is achieved with an aluminum content of $ 5 to $ 7, so that alloys with an aluminum content within this limit are particularly good for the turbine blades of gas turbines are suitable. At lower aluminum contents, the alloys have one higher melting point, and alloys with 5 to 3 »5 # or. $ 2 aluminum can be used for such ropes make good use of such as turbine stator blades, which require a high melting point, but are less stressed than rotor blades. * "

Zirconium and boron improve the creep strength of the alloys and are therefore both preferably at levels of at least $ 0.003 boron and $ 0.01 Zirconium present, the boron content being preferred * does not exceed 0.059t * Preferably the Boron content 0.01 to 0.05 # »during the zirconium cold is between 0.05 and 0.7 # and the following equation must be adhered to

+ 10 χ (56B) β 0.2 to 0.85 #.

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Titanium is an undesirable contaminant and should therefore be avoided. With the usual Heratell longitudinal processes, however, the scrap used for the batch may contain small amounts of titanium, whereby care should be taken, however, that the titanium content that got into the melt in this way does not exceed 0.5 $ and is preferably less than 0, #

An important feature of the proposed alloy is that it does not contain vanadium . j Resistance to oxidation at high temperatures and does not improve creep rupture strength. .

It is also important that the alloy be substantially free of cobalt, and if cobalt is present as an impurity, it does not exceed the value of about 1 Si.

An alloy, which is particularly suitable in the as-cast state, contains $ 6 chromium, $ 11 tungsten, 256 molybdenum, 1.5S ^ niobium, 696 aluminum, less than 0.0156 carbon, 0.1 to 0.3? I zirconium, 0 , 02 $ boron, remainder d

Niokel and impurities.

The alloy to be used according to the invention can be melted in air, but preferably it is melted in a vacuum. Under these conditions The desired low carbon content is easily achieved because the carbon is with reacts with the oxides of the constituents of the batch and is essentially removed as carbon monoxide. Independent

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Regardless of whether the alloy is vacuum melted or not, it is preferably subjected to a refined vacuum treatment such that it is kept in the melted state before casting under high vacuum. The melt should preferably be kept under vacuum at temperatures of 1400 to 1600 ⁰ O at a pressure of not more than 100 microns for a period of at least 15 minutes, but preferably for 60 minutes or more. The acidity of this treatment depends essentially on the The degree of unity of the alloy components, whereby ^ a longer treatment time is then required,

* if less pure Sohmelt additives are used

When making small castings, for example turbine blades or specimens for the test of the fatigue strength, the alloy preferably cast under vacuum. When casting large castings from melts, either in a vacuum melted or refined under vacuum, there is only a slight difference in the properties, if the casting takes place in a vacuum under protective gas or in air. All test results that are reproduced below, were tested on

* pieces determined that came from casting samples, which

melted under vacuum, potted and at least 15 minutes at 1500 ⁰ C and one:
1 micron have been refined.

15 minutes at 1500 ⁰ C and a pressure of less than

The results of the comparative experiments in Table I illustrate the improvement of the impact strength at 850 ⁰ O that is duroh causes the reduction of the KohlenBtoffgehaltes. Alloy 2 corresponds to the invention, while alloy 1

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- 7 - I ^ OOZOO

does not fall under the alloys to be used according to the invention. The tests were carried out on cast specimens produced by vacuum melting a charge of nickel, chromium, molybdenum, tungsten and, in the case of alloy 1, an addition of carbon. In addition, the melts were vacuum treated at a pressure of less than 10 microns the carbon Sauer t off reaction essentially stopped · niobium, aluminum, zirconium, and boron were then added to the melt, and this was refined for 30 minutes at a temperature of 150o ⁰ C under a pressure of less than 1 micron. The remainder of each alloy was made of nickel.

Alloy notch bottom toughness Service life Elongation 850 ^ö 0 (kgm) 23.6 kg / W7950 ° 0 W

(Hours)

4.5 4.9 75

11.3 12.5 58.63 4.6

* β analyzed carbon content of the samples for the creep strength and notch bottom toughness V.

σ * Cr Mon ¥ Tabel I. Zr B. 02 Le W. W. W. (Ji) Nb Al W- (? 0 02 gie W- W. tion 0.06 6th 2 11 0.12 ο, 1 0.004 6th 2 11 1.5 6th 0.12 ο, 2 1.5 6th

9 0 9 812/07 S 2

The slight decrease in the creep behavior "when the carbon content is reduced is largely offset by the improvement in the notch toughness avdr.

These results are in clear contrast to those obtained after changing the carbon content of other alloys that are completely similar · The results of the two alloys 3 and 4 and of alloys 5 and 6, which are shown in table II are shown show that in no case does the reduction in the carbon content become essential Improvement in the notched impact strength and the creep rupture behavior of alloy 4 resulted greatly deteriorated.

Table II

Legie
tion O
W. Or Oo
W. Mon
W. V
W. Ti Al
W- Zr 3 0.08 10 15th 3 0.65 5.2 5.7 0.07 4th 0.01 10 "15 3 0.65 5.2 5.7 0.07 5 0.05 10 10 4th - 5th 5.3 0.12 6th 0.007 10 10 4th - 5 5.3 0.12

Notched Alloy Stand Tent

850 ⁰ O (kgm) 23.6 kg / mm ^2/950 ° 0

(Hours)

4.1 4.5 20

5.1 5.9 - 2.2

6.5 6.8 21 S09812 / Ü7Ö2-

5.8 7.0 ^l Ί5 ^:

♦ All alloys were nominally $ 0.015 Boron, the remainder nickel.

The Kerbsohlagzähigkeit the alloy 2 was only slightly reduced by a longer annealing at 850 ⁰ O. After an annealing time of 3000 hours, it was still 9.6 kgm.

The fatigue strength of alloy 2 is compared in Table III with that of alloy 1a, which is identical to alloy 1, with the exception that it has a carbon content of $ 0.12. It can be seen that the reduction in the carbon content significantly improves the fatigue strength determined in the rotary bending test at room temperature and in the impact-tensile test at 6QO ^{0 O.}

Table III

alloy test _fi breaking load (kg / mm ² ) 10 changes 10 changes 10 changes

1a overflow bending - +17.8 + 12.6 search at 20 ⁰ O """

+ 39 +22 + 20.2

1a Sohlag-Zug-Ver +15.7 - + 12.6 to i

search at 600 ° 0 ~ H, 2

«Ir + 18.6 + J7.3 + 16.5

The effect of a change in the boron and zirconium \ vice haltes the proposed alloy, the creep behavior and the impact strength results from i! Table IV. Besides the references noted j contents of carbon, boron and zirconium contained!

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the alloys 6 $ chromium, 2 ° β> molybdenum, 11 $ 6 tungsten, 1.5 $ £ niobium and 6 $ aluminum, the remainder nickel and impurities »They were produced in the same way as alloys 1 and 2. Alloys 7 to H correspond to the proposal according to the invention, while alloys 1 and 15 do not come under the invention.

Table IV

Alloy C
tion ($) 0.06 Zr B. Notched impact
toughness
850 ⁰ C (kgm) 16.8 Service life
c, j λ ο && / τητη
/ 95O ⁰ C (hrs) 1 0.002 0.12 0.02 4.8 10.3 75 7th 0.002 0.15 0.02 13.6 12.4 68.5 8th 0.002 0.25 0.02 11.9 11.6 91 9 0.002 0.5 ' 0.02 8.4 3.4 73 10 0.006 0.75 0.02 10.1 37 11 0.006 0.25 0.01 13.8 57 12th 0.006 0.25 0.025 9.8 58 13th 0.006 0.25 0.05 11.7 65 Η 0.006 0, -25 0.075 9.8 68 15th 0.25 0.20 3.4 55

The creep behavior of alloy 10,

which is more than the preferred maximum zirconium content exhibited is particularly unfavorable.

Items and parts which are cast from the proposed alloy can ußzustand-G at high temperatures, for example at 850 ⁰ C or above, or even at temperatures of

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ORiGiNAL INSPECTED

_ _ri "_ ■". ■■■ U832.35

100O ⁰ O, can be used. If necessary, this alloy can be subjected to a homogenizing annealing at a temperature of 850 to 1250 ^{0 O before use «}

Hei use mr! Temperatures above 1Q00 ° 0 under conditions as prevail in gas turbines, ie with strong oxidizing conditions and a sulfur attack, can use the items and \ parts deijerfindungsgemäß to use alloy, preferably with a protective coating, for example, aluminum, accidentally will. a

909812/0782

Claims (1)

International Nickel Limited, Ihames House, Millbank, London, S _e ¥ 1, England Claims t ( 1. Use a Niokel-Chromium alloy, consisting of 5 to 10 $ chromium, 7 to 16 $ tungsten, O Ms 5 $ Mo- lybdenum, 0 to 4 $ niobium with a total content of Wolf " ram, molybdenum, niobium and 2/3 the chromium content of $ 17.5 to $ 20.5, $ 2 to $ 8 aluminum, under $ 0.03 carbon, 0 to 1 $ zirconium, 0 to 0.08 $ boron, the remainder including impurities caused by the melting process Nickel as a material for making castings, such as turbine rotors and blades, in addition to a high notched impact strength and fatigue strength at 950 C and a load of 23.6 kg / mm must have a minimum service life of 30 hours » 2. Use of an alloy according to claim 1, the boron content of which but not more than $ 0.05 "for the purpose of claim 1. f 3. Use of an alloy according to claims 1 and 2, but containing $ 0.01 to $ 0.05 boron, $ 0.05 to $ 0.7 zirconium and their boron and zirconium contents of the equation ($ Zr) + 10 ($ B) = 0.2 to 0.85 $ suffice for the purpose according to claim 1 » 4ο Use of an alloy according to claims 1 to 3 whose carbon content ^ but is less than $ 0.01, for the purpose of claim 1. 9 0 9 8 12/0782 Documents (Art. L% 1 2 # 1 Abs., Set of 3 Änderungsges. V. 4. 9. 1367) I H O O Δ OQ 5 · Use of an alloy according to claims 1 to 4, but whose chromium content is 5 "to $ 7, for the Two after. Claim 1. 6. Use of an alloy according to claims 1 "to 5, but containing no more than $ 4 molybdenum, no more than $ 2.5 kiob and 9 to H # tungsten, for the purpose of claim 1. 7 · Use of an alloy according to claims 1 to 6, the aluminum content of which is, however, 5 to 7 $, for a purpose according to claim 1 · 909812/0782