DE2265686C2 - Use of a nickel-chromium alloy - Google Patents

Description

The invention relates to the use of a nickel-chromium alloy with 20 to 24% chromium, 0.8 to 1.5% aluminum, 9.5 to 20% cobalt, 7 to 12% Molybdenum, up to 0.15% carbon, 0 to 0.6% titanium, 0 to 0.01% boron, 0 to 0.1% zirconium, 0 to 0.05% magnesium and 0 to 0.15% cerium and / or lanthanum, the remainder including impurities caused by melting nickel.

Certain objects such as combustion chambers of gas turbines, which ^{are subject to temperatures of 1093 °} C. and more during operation under oxidizing conditions, must have a high creep strength as well as a high resistance to oxidation in the event of cyclic heating and good structural stability in the event of long-term stress in a wide temperature range. Such parts are subject to oxidation in the event of cyclical heating during startup and shutdown of the turbine. In addition, the heating and cooling at medium temperatures, for example at 760 ° C, as well as the high operating temperatures, require high structural stability. The structural stability at intermediate temperatures is also of great importance with regard to repair welding, especially for thin-walled parts.

In the case of many known high-temperature alloys, the strength depends on a hardening level Elimination phase, for example a / phase. The temperature at which this phase is in the basic structure Solution goes, but is usually around 1040 ° C, so that made from such alloys Objects can generally only be used at temperatures up to about 870 ° C., because up to at this temperature the solution of the y-phase is negligible is low.

The invention is based on the object of a to propose highly heat-resistant Legiening, whose strengthening

is not caused by an elimination base and which are particularly suitable as a material for objects the wfe gas turbine chambers have a high creep strength chain, high resistance to oxidation with cyclical heating and good structural stability must have long-term exposure to different temperatures, the solution is this The task is to propose an alloy with 20 to 24% chromium, 0.8 to 1.5% Aluminum, 9.5 to 20% cobalt, 7 to 12% molybdenum, up to 0.15% carbon, 0 to 0.6% titanium, 0 to 0.01% boron, 0 up to 0.1% zirconium, 0 to 0.05% magnesium and 0 to 0.15% cerium and / or lanthanum, the remainder inclusive impurities caused by the melting process, nickel, should be used.

The contents of impurities such as sulfur, phosphorus and copper should be as low as possible and not exceed 0.015% sulfur, 0.03% phosphorus and 1% copper. In addition, the iron content of the alloy should also be limited. With regard to very high creep strength, in particular at 1093 ^° C., the alloy should contain a maximum of 5%, preferably a maximum of 2% iron. Tungsten in contents of up to 8%, for example, has no noticeable effect on the strength of the alloy and is therefore not a suitable alloy component in view of its high price and the density that changes with the tungsten content. Niobium, on the other hand, impairs the resistance to oxidation in the event of cyclical heating and should therefore only be present as an impurity.

Furthermore, the alloy can be used as an impurity in

also contain small amounts of silicon and manganese.

It is essential that the contents

of chromium and molybdenum in the aforementioned

Move salary limits to ensure sufficient oxygen

tion resistance, especially in the case of oxidation ensure cyclical heating.

The cobalt and molybdenum contents of the alloy are of exceptional importance with regard to the high-temperature strength wedge, which must therefore also be within the above-mentioned content limits. The highest heat strengths result when the cobalt content is at least 10% and preferably does not exceed 15%
The alloy can contain up to 0.15% carbon; the carbon content is however for optimal

Strength at temperatures of at least 982 ° C,

preferably 0.04 to 0.1 Vo, more preferably 0.06 to 0.08%.

The alloy can also contain titanium, boron, Zirconium and Magnesium in the specified

Content limits individually or next to each other in connection with a deoxidation of the alloy contain. Preferably, however, the boron content does not exceed 0.006% in view of the low contents No hardening takes place on titanium and aluminum in the alloy to be used according to the invention.

Small additions of rare earths such as cerium in the form of mischmetal and Lanfhan result a better resistance to oxidation with cyclical heating at IO93 ° C, which is why the Alloy can contain up to 0.15% of these elements without harmful side effects on the strength.

A particularly preferred alloy contains 0.06 to 0.08% carbon, 22% chromium, 1% aluminum, 12.5%

Cobalt, 9% molybdenum, 0.35% titanium and Q.003% boron, Remainder including impurities caused by the melting process Nod],

The alloy in question has in the kneaded state after annealing at II 77 ° C with subsequent cooling in air in general a room temperature yield point of about 290ΜΝΛη ^? , a tensile strength of about 730 MWm ² , an elongation of about 70% and a necking of about 57% and at tO93 ° C a yield point of about 48 MN / m ² , a tensile strength of about 76 MN / m ² , an elongation of about 90% and a necking of about 77%. Preferred alloys generally have a service life of 100 hours at 816 ° C and a load of about 138 MN / m ² or at 927 ° C and a load of 61 MN / m ² or at 1038 ° ^{C and a load of 254 MN / m 2} .

The alloy mentioned can be melted in the usual way in air or in a vacuum induction furnace or in an electric slag furnace. The alloy is preferably each melted in a vacuum in view of its high-quality properties. In addition, the alloy has a high resistance to long-term oxidation under cyclic heating at 1093 ⁰ C and developed according to a long-term temperature stress at 650 to 870 ° C, no brittle phases. Finally, the alloy can also be welded under protective gas; it is particularly suitable for MIG welding using a filler material with the same composition or

other filler metals suitable for welding connections using the proposed alloy as an additional material at room temperature same strength as at about 1095 ° C; they are also resistant to oxidation when welded like the kneaded alloy.

The invention is explained in more detail below on the basis of exemplary embodiments:

example 1

A total of 10 alloys were produced in the form of 10 kg melts of the type shown in Table I below specified composition melted. Alloys 1 to 7 were processed in the induction furnace Air melted while alloys 8 to 10 were melted in the Vafcium induction furnace. To After casting, the blocks were forged into square bars with an edge length of 143 mm

The rods were then annealed for one hour at 1177 ° C. with air cooling Short tensile tests carried out at room temperature and at 1093 ° C. The test results are in the Table II compiled

The creep tests were carried out at 816 ° C. under a load of 166 MN / m ² and at 1093 ° C. with a load of 21 MN / m ² after annealing for one hour at 1177 ° C. with the results compiled in Table IH

Table I.

Legie Cr II Al Co Room temperature Zugf. fc * o C. Γι B. Fe Si (%) Ni tion (%) (%) (%) Stretch (MN / m ² ) (%) (%) (%) (%) (%) (%) _ (%) 1 21.82 0.89 14.14 (MN / m ² ) 800 9.41 0.04 0.29 0.005 0.13 0.03 0.038 Ce rest 2 21.96 0.91 10.24 305 638 9.05 0.04 0.30 0.005 0.10 0.03 0.03 La rest 3 21.92 0.97 10.16 255 848 8.85 0.04 0.31 0.005 0.12 0.03 - rest 4th 21.70 0.92 9.98 322 800 9.10 0.04 0 _r 40 0.005 0.17 0.08 - rest 5 21.89 1.02 10.16 319 792 9.24 0.05 0.38 0.0057 3.13 0.03 - rest 6th 21.94 1.01 10.12 315 769 9.28 0.06 0.39 0.0046 0.16 0.41 - rest 7th 21.43 0.90 19.80 307 869 9.07 0.04 0.30 0.005 0.10 0.05 - rest 8th 21.62 0.89 9.92 462 9.01 0.007 0.35 0.0079 1.16 0.03 - rest 9 21.66 0.92 10.13 9.28 0.016 0.35 0.0069 0.22 0.03 - rest 10 21.69 0.93 10.04 9.23 0.06 0.35 0.0061 0.16 0.02 rest Tabel Legie 1093X strain tion strain Snug Stretch Zugf. (%) Snug (%) (%) (MN / m ² ) (MN / m ² ) 70.0 (%) 1 64.0 61.3 75 75 45.0 68.7 2 39.0 54.5 73 74 47.0 45.0 3 54.0 65.3 73 73 79.0 43.6 4th 56.0 58.7 72 72 74.0 73.6 5 58.0 60.3 39 70 88.5 55.3 6th 59.0 54.4 52 124 43.0 68.7 7th 50.0 64.5 107 107 78.0

continuation

alloy

Room temperature

Stretch ZugT. (MN / m ² ) (MN / m ² ) 1Q93 "C

Elongation Einn, Streckgr, ZugC Elongation Einn.

(%) TO (MN / m ² ) (MN / m ² ) (%) (%)

290 286 317

734 751 776

64.0 66.0 66.0

65.8 69.6 63.8 37
52
57

66
63
74

84.0
78.0
52.0

56.0
48.4
36.4

Table ΠΙ

alloy

816-C / 166 MN / m ²

Service life elongation (h) (%)

1093 ° C / 21 MN / m ²

Snug Service life elongation

Snug

1 2 3 4 5 6 7 8 9 10

26.3 86.0 65.5 23.2 116.0 72.0 16.9 97.0 73.5 24.7 117.0 73.0 22.1 105.0 70.0 32.8 97.0 70.6 46.0 105.0 67.0 26.4 115.0 79.5 30.4 129.0 79.5 39.9 100.0 70.0

57.4 26.5 25.5 19.2 174 22.5 17.9 21.5 214 50.0 70.0 56.5 36.1 61.5 44.0 36.1 50.0 46.0 38.1 46.7 43.9 18.5 128.0 68.0 19.5 664 47.0 73.5 43.5 324

Example 2

A 2268 kg melt of an alloy 11 with 0.02% carbon, 0.04% manganese, 0.23% iron, 0.05% silicon, 57.5% nickel, 21.85% Chromium, 1.07% aluminum, 0.4 ^c ; j titanium, 0.028% magnesium, 9.94% cobalt, 8.86% molybdenum and 0.0018% boron melted into blocks with the dimensions 279 1143 χ 1270 mm shed. Portions of the billets were hot rolled to a 51 mm thick plate and a 19 mm diameter rod and cold rolled to a 1.6 mm thick bend. rather, the sheet was subject to a cross-section decrease of 58.7% during the final cold forming. In the short tensile test at various temperatures, samples of the hot-rolled bar after annealing for one hour at 1177 ° C with air cooling and on the cold-rolled sheet after 5-minute annealing at 1177 ° C with air cooling resulted in the values listed in Table IV below.

Table IV Stretch limit tensile strenght strain Constriction hardness Temp. (MN / m ² ) (MN / m ² ) (%) (%) (Rb) CQ Rod 280 687 70.0 72.7 79 RT 196 543 71.0 60.3 73 538 183 531 71.0 64.0 77 649 178 428 83.0 67.5 72 760 176 254 122.0 88.5 74 871 163 163 109.0 90.0 66 982 66 66 132.0 91.0 66 1093 sheet 242 616 68.5 - 61 RT 61 61 102.0 - 80 1093

The cold-rolled sheet withstood without difficulty after being annealed at 982 to 1177 ° C severe bending test.

Creep tests resulted in both the rods and the sheet metal after annealing at ti77 ° C

Standing time of 100 hours at 816 ° C and a load of 121 MN / m ^2, at 927 ° C under a load of 49 MN / m ² and at 1093 ⁰ C under a load of 21 MN / m ^2.

Example 3

A 2268 kg melt was produced in a conventional vacuum induction furnace and cast under a flux cover in air to form a small block measuring 279 × 1143 × 1270 mm. This alloy 12 contained 0.07% carbon, 0.13% iron, 0.04% silicon, 22.51% chromium, 1.05% aluminum, 0.41% titanium, 0.029% magnesium. 12.67% cobalt, 8.91% molybdenum and 0.0051% boron, the remainder including impurities caused by the melting process, nickel. The block was press-forged into a body with a cross-section of 241 1067 mm and then hot rolled to the dimension 51 χ 1270 mm ^{without difficulty at 150 ° C.} Thereafter, three test pieces measuring 51 × 51 × 1270 mm were cut out and hot-rolled into bars with a diameter of 19 mm. The remainder was cut in half and hot rolled into strip with a cross section of 8.1 χ 1321 mm. One strip was continuously annealed at 1066 ⁰ C and cold rolled to a thickness of 4.8 mm, then intermediately annealed at 1066 ° C and to cold rolled down mm to a thickness of 1.6. This strip was then continuously annealed at 1177 ° C. Tensile tests with the test results compiled in Table V below were carried out at various temperatures on samples made from the hot-rolled bar and the sheets after annealing for one hour at ii 77 ^{= C.}

Table V Stretch train strain A Temp. border strength lacing (MN / m ² ) (MN / m ² ) (%) (%) (C) Rod 296 735 70.0 57.2 RT 195 580 69.0 57.6 538 171 568 75.0 54.5 649 177 447 84.0 64.6 760 196 281 120.0 92.5 871 145 148 124.0 94.1 982 51 79 90.0 77.5 1093 sheet 324 691 54.0 RT 217 590 56.0 538 197 579 62.0 649 207 464 76.0 760 210 248 92.0 871 100 134 58.0 982 52 72 58.0 1093

Further tests showed that the sheet metal after annealing at 1149 ° C and higher temperatures the Resistance to bending test without cracking.

Creep tests on the hot-rolled rod material annealed for one hour at 1177 ° C resulted in a service life of 100 hours each at 816 ° C and a load of 138 MN / m ² , at 927 ° C and a load of 65 MN'm ² and at 1093 ⁰ C and a load of 31 MN / m ² .

Example 4

Hot rolled bars of the alloys 6 and 8 to 12 were annealed for one hour at 1177 ° C and the Kurzzugversuch at 649 ° C 704 ⁰ C 760 ° C 816 "C and

Table VI compiled

An X-ray examination following a long-term glow showed that the structure as a result of the

Subject to 87 Γ C as well as only one carbide phase of the composition with regard to its impact annealing Toughness test The test results are in the MzjQ occurred.

Example 5

Cold rolled, 3.2 mm thick sheets of alloys 2 to 4, !! 12 and 1000 hours IaKg were subjected to cyclic oxidation, consisting in each cycle consists of a 15 minute annealing at 1093 ⁰ C and a 5 minute cooling. The total depth of attack = on the sheet metal sample after the test was only 0.066 mm for each of the alloys 2 and 3, only 0.11 mm for the alloy 4 and for each of the alloys

ίο

11 and 12 only 0.076 mm. A periodic weighing of the samples during the test showed that this virtually no change in weight and, consequently, subject were resistant to oxidation under cyclic heating at 1093 ⁰ C in a high degree. The alloy also has a high resistance to acid corrosion. In particular, the coating has a high resistance to common mineral acids, in particular to nitric acid

different concentration. In addition, it is resistant to sulfuric acid with a concentration of up to 30% at 80 ^° C. and to up to 10% boiling sulfuric acid. The alloy also has an average resistance to hydrochloric acid at a concentration of up to 30% or more at 80 ° C, and excellent resistance to phosphoric acid of 80 ⁰ C at any concentration even in the presence of up to 1% hydrofluoric acid.

Tabel VI (H) Alloy 6 hardness Alloy 10 hardness
Rb Alloy 11 hardness
Rb Alloy 12 hardness
Rb Heat treatment 50
iöOö Notch impact
toughness
(J) - Notch impact
toughness
(J) - Notch impact
toughness
(J) 81 Notch impact
toughness
(J) 82
94, (C) 50
1000 - 97 - 90 325 92 259
67 93
94 649
649 50
1000 81 93 173 93 165 85 107
68 89
88 704
704 50
1000 79 93 92 93 94 86 92
95 90
87 760
760 50
1000 62 93 87 92 53 83 99
107 87
84 816
816 53 91 71 117
118 871
871

The proposed alloy is particularly suitable as a material for gas turbine chambers and line systems of aircraft gas turbines; it is particularly for use in cyclic oxidation at temperatures of about 980 C, for example 1095 C and more suitable.

Claims (5)

Claims; 1. Use of an alloy with 20 to 24% chromium, O ₁ B to 1.5% aluminum, 9.5 to 20% cobalt, 7 to 12% molybdenum, up to 0.15% carbon, 0 to 0.6% titanium , 0 to 0.01% boron, 0 to 0.1% zirconium, 0 to 0.05% magnesium and 0 to 0.15% cerium and / or lanthanum, the remainder including impurities caused by the melting process, nickel as a material for objects such as gas turbine chambers must have a high creep strength, high resistance to oxidation in the event of cyclical heating and good structural stability in the event of long-term stress at different temperatures. 2. Use of an alloy according to claim 1, but containing not more than 0.006% boron, for the Purpose according to claim 1- 3. Use of an alloy according to claim 2 but containing 10 to 15% cobalt for the purpose according to claim 1. 4. Use of an alloy according to claim 2 or 3, which however contains 0.04 to 0.1% carbon, for the purpose of claim 1. 5. Use of an alloy according to one or more of claims 2 to 4, which, however, 0.06 to 0.08% carbon and 22% chromium, 1% aluminum, 124% cobalt, 9% molybdenum, 035% titanium and 0.003% boron, the remainder including melt-related Containing impurities nickel for the purpose of claim 1.