EP1420075A1 - Nickel-base superalloy - Google Patents

Abstract

Nickel-base superalloy contains chromium (in weight %) (7-13), cobalt (4-10), molybdenum (0.5-2), tungsten (2-8), tantalum (4-6), aluminum (3-6), titanium (1-4), ruthenium (0.1-6), hafnium (0.01-0.5), silicon (0.001-0.15), carbon (0-700 ppm), boron (0-300 ppm) and remainder containing nickel and production-related impurities.

Description

Technical field

The invention relates to the field of materials technology. It affects a nickel-based superalloy, especially for the production of Single crystal components, such as blades for gas turbines.

State of the art

Such nickel-based superalloys are known. Single-crystal components of these alloys exhibit a high temperature very good material strength. This can, for. B. the inlet temperature of Gas turbines are increased, which increases the efficiency of the gas turbine.

Nickel-based superalloys for single crystal components, such as those from US 4,643,782, EP 0 208 645 and US 5,270,123 are known mixed crystal strengthening alloy elements, for example Re, W, Mo, Co, Cr, and γ'-phase-forming elements, for example Al, Ta, and Ti. Der Content of high melting alloy elements (W, Mo, Re) in the Basic matrix (austenitic γ phase) increases continuously with the increase the stress temperature of the alloy. So contain z. B. usual Nickel-based superalloys for single crystals 6-8% W, up to 6% Re and up 2% Mo (figures in% by weight). The in the above mentioned publications Alloys disclosed have high creep resistance, good LCF (Fatigue with low number of load cycles) - and HCF (fatigue with high Number of load cycles) properties and a high oxidation resistance.

These known alloys have been developed and used for aircraft turbines therefore optimized for short and medium-term use, i.e. the The duration of use is designed for up to 20,000 hours. in the In contrast, industrial gas turbine components must be on one Of up to 75,000 hours.

After a stress period of 300 hours, for. B. the alloy CMSX-4 from US 4,643,782 for trial use in a gas turbine a severe coarsening of the γ'-phase at a temperature above 1000 ° C., the disadvantageous with an increase in the creep speed of the Alloy goes hand in hand.

The alloys known, for example, from US Pat. No. 5,270,123 also have comparable disadvantages. The alloying elements selected there result in the above-mentioned alloys a positive or a negative lattice offset between the γ-phase forming the matrix and the γ'-phase, ie the secondary intermetallic phase Ni ₃ Al, in which Ta, Ti, Hf partially Al and Co, and Cr can partially replace Ni. This lattice distortion prevents dislocations when sliding or cutting the γ 'grains. The lattice distortion causes an increase in the short-term strength, but with prolonged stress, the structure becomes coarser and then a degradation of the γ 'structure and thus a long-term mechanical weakening of the alloy.

This disadvantage is overcome with the alloy known from EP 0 914 483 B1 eliminated. This nickel-based superalloy consists essentially of (measured in% by weight) 6.0-6.8% Cr, 8.0-10.0% Co, 0.5-0.7% Mo, 6.2-6.6% W, 2.7-3.2% Re, 5.4-5.8% Al, 0.5-0.9% Ti, 7.2-7.8% Ta, 0.15-0.3% Hf, 0.02-0.04% C, 40-100 ppm B, 0-400 ppm Y, balance Ni with impurities, where the ratio of (Ta + 1.5 Hf + 0.5 Mo - 0.5 Ti) / (W + 1.2 Re) ≥ 0.7 is. Due to the ratio mentioned, these alloys have the Alloy elements at operating temperature no lattice offset between the γ-phase and the γ'-phase, which ensures high long-term stability moderate load is reached. It also has rhenium alloyed nickel-based superalloy excellent castability and great phase stability combined with the best mechanical Characteristics. It is also characterized by high fatigue strength and Creep stability even with long-term exposure.

It was also found that there was a mechanical Stress and long-term high-temperature stress to a directed coarsening of the γ'-particles, the so-called raft formation (rafting) comes and, at high γ'-contents (i.e. with a γ'-volume fraction of at least 50%), for inverting the microstructure, i.e. γ 'becomes continuous phase in which the previous γ matrix is embedded. Since the intermetallic γ'-phase for environmental embrittlement (environmental embrittlement), this leads to certain stress conditions massive drop in mechanical properties, especially the Yield point, at room temperature (degradation of properties). The Environment embrittlement occurs especially when moisture and there are long holding times under tensile load.

Presentation of the invention

The aim of the invention is to avoid the disadvantages mentioned. The The object of the invention is to provide a nickel-based superalloy develop which on the one hand has a solid and strong γ phase as a matrix and which on the other hand only a small proportion, i.e. less than 50%, has γ'-phase, and is therefore very resistant to oxidation and a exhibits good creep behavior.

7-13 Cr

4-10 Co

0.5-2 Mo

2-8 W

4-6 Ta

3-6 Al

1-4 Ti

0.1-6 Ru

0.01-0.5 Hf

0.001-0.15 Si

0-700 ppm C

0-300 ppm B

Rest Nickel und herstellungsbedingte Verunreinigungen.According to the invention, this object is achieved in that the nickel-based superalloy according to the invention is characterized by the following chemical composition (details in% by weight):

7-13 cr

4-10 co

0.5-2 mo

2-8 W.

4-6 days

3-6 Al

1-4 Ti

0.1-6 Ru

0.01-0.5 Hf

0.001-0.15 Si

0-700 ppm C

0-300 ppm B

Balance nickel and manufacturing-related impurities.

The advantages of the invention are that the alloy is a good one Has degradation behavior. The γ phase (matrix) is determined by the Alloying of ruthenium solidifies, despite the absence of Rhenium, which according to the known prior art is particularly good Mixed crystal strengthener applies and therefore the properties of the γ matrix strongly improved. The alloy according to the invention is characterized by good ones Creep rupture strength, stable structure and good castability.

In addition, the oxidation resistance of the alloy is very good. she is excellently suited for the production of single crystal components, for example, blades for gas turbines.

Due to the low proportion of secondary precipitation-hardening γ'-phase, which is embedded in the strongly solidified γ phase is that Degradation behavior of the alloy according to the invention is good. There is no Single crystal crack growth and no sharp drop in the yield strength Room temperature in the degraded state compared to not degraded state.

10-13 Cr

8-9 Co

1.5-2 Mo

3-5 W

4-5 Ta

3-5 Al

2-4 Ti

0.3-4 Ru

0.01-0.5 Hf

0.001-0.15 Si

0-700 ppm C

0-300 ppm B

Rest Nickel und herstellungsbedingte Verunreinigungen.Preferred ranges of the nickel-based superalloy according to the invention are (details in% by weight):

10-13 cr

8-9 Co

1.5-2 months

3-5 W

4-5 days

3-5 Al

2-4 ti

0.3-4 Ru

0.01-0.5 Hf

0.001-0.15 Si

0-700 ppm C

0-300 ppm B

Balance nickel and manufacturing-related impurities.

10-13 Cr

8-9 Co

1.5-2 Mo

3.5-4 W

4-5 Ta

3.5-5 Al

3-4 Ti

0.3-1.5 Ru

0.5 Hf

10-500 ppm Si

250-350 ppm C

80-100 ppm B

Rest Nickel und herstellungsbedingte Verunreinigungen.A particularly preferred area of the nickel-based superalloy according to the invention is as follows:

10-13 cr

8-9 Co

1.5-2 months

3.5-4 W.

4-5 days

3.5-5 Al

3-4 ti

0.3-1.5 Ru

0.5 Hf

10-500 ppm Si

250-350 ppm C

80-100 ppm B

Balance nickel and manufacturing-related impurities.

7-9 Cr

8-9 Co

1.5-2 Mo

3-5 W

5-6 Ta

3-5 Al

1-2 Ti

0.5-1.5 Ru

0.5 Hf

700 ppm C

100 ppm B

500 ppm Si

Rest Nicckel und herstellungsbedingte Verunreinigungen.Another nickel-based superalloy according to the invention has the following chemical composition (data in% by weight):

7-9 cr

8-9 Co

1.5-2 months

3-5 W

5-6 days

3-5 Al

1-2 ti

0.5-1.5 Ru

0.5 Hf

700 ppm C.

100 ppm B

500 ppm Si

Rest Nicckel and manufacturing-related impurities.

Brief description of the drawings

Fig. 1

ein Gefügebild der Vergleichslegierung VL;

Fig. 2

ein Gefügebild der erfindungsgemässen Legierung L1;

Fig. 3

ein Gefügebild der erfindungsgemässen Legierung L1 nach Degradierung;

Fig. 4

ein Gefügebild der erfindungsgemässen Legierung L2 nach Degradierung;

Fig. 5

ein Diagramm, welches die Gewichtsänderung der Legierungen VL, L1 und L2 in Abhängigkeit von der Zeit angibt;

Fig. 6

ein Diagramm, welches die 0,2%-Streckgrenze der Legierungen VL, L1 und L2 in Abhängigkeit vom Degradations-Parameter angibt und

Fig. 7

ein Diagramm, welches die Spannung (1%-Dehngrenze) der Legierungen VL, L1 und L2 in Abhängigkeit vom Larson Miller-Parameter angibt.

Two exemplary embodiments of the invention are shown in the drawings. Show it:

Fig. 1

a microstructure of the comparative alloy VL;

Fig. 2

a micrograph of the alloy L1 according to the invention;

Fig. 3

a micrograph of the alloy L1 according to the invention after degradation;

Fig. 4

a micrograph of the alloy L2 according to the invention after degradation;

Fig. 5

a diagram indicating the change in weight of the alloys VL, L1 and L2 as a function of time;

Fig. 6

a diagram indicating the 0.2% yield strength of the alloys VL, L1 and L2 as a function of the degradation parameter and

Fig. 7

a diagram indicating the stress (1% proof stress) of the alloys VL, L1 and L2 as a function of the Larson Miller parameter.

Ways of Carrying Out the Invention

The invention is described below with the aid of exemplary embodiments and 1 to 7 explained in more detail.

Nickel-based superalloys with the chemical composition given in Table 1 were examined (data in% by weight): Chemical composition of the alloys examined L1 (AMN1) L2 (AMN3) VL (PW 1483) Ni rest rest rest Cr 9.96 12:34 12.8 Co 8.86 8.84 9 Mo 1:47 1.85 1.9 W 3:45 3.76 3.8 Ta 4 4.96 4 al 3:57 3:45 3.8 Ti 3.83 3.96 4 Hf 0.5 00:48 - C 0025 0033 - B 86 ppm 79 ppm - Si 10 ppm 10 ppm - Ru 1:07 00:28 -

Alloys L1 and L2 are alloys whose composition is below the claims of the present invention fall. In contrast to that the alloy VL is a comparison alloy, which is called PW 1483 is known prior art. It differs from the Alloys according to the invention especially in that they are not Ruthenium is alloyed and there is no significant Si content. In the Composition with respect to the elements are Cr, Co, Mo, Ta, Al, Ti and Ni the alloys L2 and VL are almost identical. This applies to the Cr content also towards the alloy L1. With L1 the Cr content is approx. 3% by weight less than with the comparison alloy VL.

All three alloys were subjected to the following heat treatment: 1 h / 1204 ° C + 1 h / 1265 ° C + 4 h 1080 ° C.

The Vickers hardness HV2 was measured. The results listed in Table 2 were achieved. Vickers hardness for the alloys examined L1 VL HV2 447 403

The alloy L1 thus has a hardness that is more than 10% higher than that Comparative alloy VL. The γ phase (matrix) of the Alloys are mainly solidified by the alloyed ruthenium.

FIG. 1 shows the structure of the comparative alloy VL1, while FIG. 2 shows that Structure of the alloy L1 according to the invention shows.

Compared to alloy VL, alloy L1 is clearly the lower Proportion of γ'-phase (dark particles) can be seen. The γ 'phase (secondary, intermetallic phase formed by precipitation hardening) has in the Alloy VL has an approximately square shape and is strip-shaped in the matrix arranged. In contrast, the γ 'phase in L1 has a spherical shape, what an indication of a very slight lattice offset between the γ and the γ 'phase represents. This slight lattice offset and, above all, the small one Volume fraction of γ'-phase (less than 50%) have an effect on this positive that there is no γ / γ 'inversion of the microstructure, i.e. the γ'-phase is embedded in the γ-phase and does not form a continuous network. Thus, a good degradation behavior of the inventive Alloys achieved.

Figures 3 and 4 show micrographs of the inventive Alloys L1AD (Fig. 3) and L2AD (Fig. 4) in the degraded state (T = 1000 ° C, σ = 80 MPa, t = 747 h). The γ 'phase is embedded in the γ phase and does not form a continuous network. The alloy L1AD shows predominantly round to oval forms of the γ'-phase, while in the Alloy L2AD the γ'-phase is very stretched.

This affects the properties. 5 is the Weight change as a function of time for the three alloys shown. The alloys according to the invention show after degradation a significantly smaller change in weight than that from the prior art Comparative alloy known in the art, i.e. they have an essential better oxidation resistance.

6 shows the dependence of the 0.2% yield strength at room temperature on the degradation parameter P. P = (T-800) t 1.2 σ 1.5 ,

While the comparison alloy VL and the alloy L2AD are almost the same behavior, the voltage for L1AD is approx. 200 MPa below the values for VL and L2AD.

If you carry the 0.1 proof stress above the Larson Miller parameter LM, too LM = T (log t + 20) 7, the dependencies shown in FIG. 7 result. The alloy L2AD has higher yield strengths than the comparative alloy (with better oxidation behavior) over the entire range. Although the alloy L1AD only has lower yield strengths than the comparative alloy VL, it also has a much better resistance to oxidation.

Of course, the invention is not limited to that described Embodiments limited.

Claims (4)

Nickel-based superalloy for the production of single crystal components characterized by the following chemical composition (data in% by weight): 7-13 cr 4-10 co 0.5-2 mo 2-8 W. 4-6 days 3-6 Al 1-4 Ti 0.1-6 Ru 0.01-0.5 Hf 0.001-0.15 Si 0-700 ppm C 0-300 ppm B Balance nickel and manufacturing-related impurities. Nickel-based superalloy according to Claim 1, characterized by the following chemical composition (details in% by weight): 10-13 cr 8-9 Co 1.5-2 months 3-5 W 4-5 days 3-5 Al 2-4 ti 0.3-4 Ru 0.01-0.5 Hf 0.001-0.15 Si 0-700 ppm C 0-300 ppm B Balance nickel and manufacturing-related impurities. Nickel-based superalloy according to Claim 2, characterized by the following chemical composition (details in% by weight): 10-13 cr 8-9 Co 1.5-2 months 3.5-4 W. 4-5 days 3.5-5 Al 3-4 ti 0.3-1.5 Ru 0.5 Hf 10-500 ppm Si 250-350 ppm C 80-100 ppm B Balance nickel and manufacturing-related impurities. Nickel-based superalloy according to Claim 1, characterized by the following chemical composition (details in% by weight), 7-9 cr 8-9 Co 1.5-2 months 3-5 W 5-6 days 3-5 Al 1-2 ti 0.5-1.5 Ru 0.5 Hf 500 ppm Si 700 ppm C. 100 ppm B Balance nickel and manufacturing-related impurities.

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