EP2547804B1 - Nickel-chromium-cobalt-molybdenum alloy - Google Patents

Description

The invention relates to a nickel-chromium-cobalt-molybdenum alloy having excellent strength and creep properties as well as exceptional resistance to high-temperature corrosion.

The EP 2 039 789 A1 discloses a nickel base alloy for a turbine rotor for a steam engine including: C 0.01 to 0.15%, Cr 18 to 28%, Co 10 to 15%, Mo 8 to 12%, Al 1.5 to 2%, Ti 0 , 1 to 0.6%, B 0.001 to 0.006%, Ta 0.01 to 0.7%, balance nickel and unavoidable impurities. This composition is said to have increased mechanical strength while retaining forging properties.

By the EP 0 358 211 B1 or the EP 2 204 462 A1 For example, a nickel-chromium-molybdenum-cobalt alloy having a particular carbide morphology has been disclosed which gives the alloy a better creep rupture strength at elevated temperatures. The alloy consists (in% by weight) of 15 to 30% chromium, 6 to 12% molybdenum, 5 to 20% cobalt, 0.5 to 3% aluminum, up to 5% titanium, 0.04 to 0.15% Carbon, up to 0.02% boron, up to 0.5% zirconium, up to 5% tungsten, up to 2.5% niobium or tantalum, up to 5% iron, up to 0.2% rare earth metals, up to 0.1% nitrogen, up to 1% copper, up to 0.015% sulfur, up to 0.03% phosphorus and up to 0.2% magnesium or calcium, balance except impurities nickel.

Although the alloys can contain up to 2.5% Nb or Ta, these elements compromise cyclic oxidation resistance, which is particularly pronounced with the simultaneous presence of chromium and aluminum.

The magazine " Materials and Corrosion 2008, 59, No. 7 "is on pages 484 to 590 the report "Parameters governing the reduction of oxide layers on Inconel 617 in impure VHTR HE atmosphere (Chapovaloff J et al)". In Table 1 of this report the material Inconel 617 is as follows Composition shown: Cr 21.56%, Co 12%, Mo 9.21%; Fe 0.95%, Mn 0.10%, Ti 0.41%, Al 1.01%, C 0.06%, Cu 0.07%, Si 0.15%, B 0.002%, balance nickel.

The datasheet " Nicrofer 5520 Co - Alloy 617 "of ThyssenKrupp VDM GmbH from January 2005 is on pages 1 to 12 to take the said material having the following composition Cr 20 to 24% Fe Max. 3% C 0.05 to 0.15% Mn Max. 1 % Si Max. 1 % Co 10 to 15% Cu Max. 0.5% Not a word 8 to 10% Ti Max. 0.6% al 0.8 to 1.5% P Max. 0.012% S Max. 0.015% B Max. 0.006% Ni rest

Such alloys have been used for many decades in practice and are known as "alloy 617". It has been found that components made from such alloys have some tendency to stress cracking in the temperature range of 550 to 850 ° C. This was particularly evident in welded joints thick-walled components. The causes for this are seen as residual stresses in connection with carbide precipitations. This could be partially corrected by a heat treatment lasting several hours at about 1,000 ° C, with a Such heat treatment could not be performed in some cases or only with great difficulty.

The invention has for its object to improve this known and proven alloy by targeted modification of individual alloying elements so that the disadvantages are no longer given.

This object is achieved by a nickel-chromium-cobalt-molybdenum alloy consisting of (in% by weight) Cr 21 - 23% Fe 0.05 - 1.5% C 0.05-0.08% Mn ≤ 0.5% Si ≤ 0.25% Co 11 - 13% Cu ≤ 0.15% Not a word 8.0 - 10.0% Ti 0,3 - 0,5% al 0.8 - 1.3% P <0.012% S <0.008% B > 0.002 - <0.006% Nb > 0-1% N ≤ 0.015% mg ≤ 0.025% Ca ≤ 0.01% V 0.005 - ≤ 0.6%, alternatively W in contents between 0.02 - max. 2% Ni Remainder as well as impurities caused by melting,

• X3 = 5 - 50, wobei
• $$\mathrm{X}\mathrm{3}=\mathrm{100}*\frac{\mathrm{X}\mathrm{1}}{\mathrm{X}\mathrm{2}}$$
  
• und X1 =C+5 N
• und X2=0,5 Ti+Nb+0,5 V ist.

in the form of tubes, sheets, wire, rods, strips or forgings, the alloy satisfying the following formula:

• X3 = 5 - 50, where
• $$\mathrm{X}\mathrm{3}=\mathrm{100}*\frac{\mathrm{X}\mathrm{1}}{\mathrm{X}\mathrm{2}}$$
  
• and X1 = C + 5N
• and X2 = 0.5 Ti + Nb + 0.5V.

• B 0,002 - 0,005 %

It is particularly advantageous if the content of B is set as follows:

• B 0.002 - 0.005%

The Mn content is advantageously ≦ 0.3%. If desired, the alloy may contain as further element W in amounts between 0.02 and 2%.

It is further advantageous if the vanadium content in the alloy according to the invention is set between 0.005 and ≦ 0.6%.

Surprisingly, it has been found that by selective addition of Nb and / or V and B, the precipitation of chromium carbide lines can be suppressed. This significantly reduces the tendency to form stress cracks during welding during operation.

• X3 = 5 - 50, wobei
• $$\mathrm{X}\mathrm{3}=\mathrm{100}*\frac{\mathrm{X}\mathrm{1}}{\mathrm{X}\mathrm{2}}$$
  
• und X1 =C+5N
• und X2 = 0,5 Ti + Nb + 0,5 V ist.

The alloy of the invention satisfies the formula:

• X3 = 5 - 50, where
• $$\mathrm{X}\mathrm{3}=\mathrm{100}*\frac{\mathrm{X}\mathrm{1}}{\mathrm{X}\mathrm{2}}$$
  
• and X1 = C + 5N
• and X2 = 0.5 Ti + Nb + 0.5V.

If necessary, the alloy according to the invention may be subjected to a heat treatment in the temperature range between 800 and 1000 ° C., preferably at 980 ° C., in order to increase the ductility and to remove stresses. The proportion of carbides should advantageously be> 0.9%. By targeted adjustment, in particular the contents of Nb, V and B, such a heat treatment can now be carried out without difficulty.

The subject invention provides a high temperature alloy for operating temperatures between 500 and 1200 ° C.

The alloy according to the invention can be used both in the form of pipes, sheets, wire, rods, forgings or castings and strips, as well as for welded constructions. Preferred fields of application are gas turbines, the Furnace and power plant construction, the petrochemical industry as well as the field of nuclear energy technology

Table 1 compares a prior art alloy 5 with variants V1 to V5 according to the invention. Table 1 element State of the art V1 V2 V3 V4 V5 VdTUV-Werkst B1.485 typical analysis Nb 0.5 Nb 0.5V 0.2 V 0.2 V 0.65 Mo up % By weight % By weight % By weight % By weight % By weight % By weight % By weight Ni rest rest rest rest rest rest rest Cr 20.0 to 23.0 2208 22 22 22 21.9 21.5 Co 100-130 11 54 12.2 122 124 124 12.4 Not a word 80-100 865 84 8.4 8.4 84 9.5 Ti 0.20 -0.50 039 041 0.4 0.4 0.4 0.41 al 060 to 1.50 1.09 0.86 0.84 0.84 0.82 0.88 Fe Max . 20 1 22 032 0.36 0.1 023 003 Mn max 0 70 0.1 002 0.02 0.02 002 002 Si max 0.70 02 <0.01 <0.01 <0.01 <0.01 0.01 C 0.050 - 0.100 0.062 005 005 0.05 005 0065 P Max. 0 012 0003 <0.001 <0.01 0,002 0002 0002 S Max. 0 008 <0.002 <0.001 <0.001 <0.001 <0.001 <0.001 ace Max. 0,010 0.001 <0.01 <.0,01 <0.01 <0.01 <0.01 B Max. 0.001 0.001 0.0033 0.0034 0.0034 0.0033 0.0028 pb Max. 0,007 0.0002 <0.005 <0.005 <0.005 <0.005 <0.005 V 0.02 <0.01 0.18 0.18 0.6 <0.01 N 0011 <0.01 <0.01 <0.01 <0.01 <0.01 Nb 002 0.55 05 <0.01 <0.01 <0.01 W 0.4 0.1 0.1 0.1 0.1 0.1

Table 2 compares prior art alloys and five inventive variants V1 to V5 with respect to the dissolution behavior of the carbides. Table 2 variant Lsg.Glüh temp. solvus Nb V Not a word Primary carbide M6C Cr carbide % By weight % By weight % By weight ° C ° C State of the art 0 0 8 - 10 1250-1290 990-1000 V1 0.55 <0.01 8.4 1237 1096 V2 0.5 0.18 8.4 1207 1153 V3 <0, 01 0.18 8.4 1228 1133 V4 <0, 01 0.6 8.4 1214 1182 V5 <0.01 <0.01 9.5 1290 839

Table 3 compares a prior art alloy and 5 inventive variants V1 to V5 with respect to ductility (SSRT experiment at 700 ° C.). Table 3 variant comment Constriction (Z) Elongation (A) ° C ° C State of the art Without boron 7.5 5 V1 14 8.5 V2 11 8.5 V3 21 24 V4 42 21 V5 20 10

Claims (11)

1. A nickel-chromium-cobalt-molybdenum alloy composed of (in % by mass): Cr 21 - 23 % Fe 0.05 - 1.5 % C 0.05 - 0.08 % Mn ≤ 0.5 % Si ≤ 0.25 % Co 11 - 13% Cu ≤ 0.15 % Mo 8.0 - 10.0 % Ti 0.3 - 0.5 % Al 0.8 - 1.3 % P < 0.012% S < 0.008 % B > 0.002 - < 0.006 % Nb > 0 - 1 % N ≤ 0.015 % Mg ≤ 0.025 % Ca ≤ 0.01 % V 0.005 - ≤ 0.6 %, optionally comprising contents of W comprised between 0.02 - max. 2 %,
   Ni being the rest, as well as melting dependent impurities,
   in form of tubes, sheet metals, wire, rods, bands or forged parts, wherein the alloy meets the conditions of the following formula:

   X3 = 5 - 50, wherein

   $$\mathrm{X}\mathrm{3}=\mathrm{100}*\frac{\mathrm{X}\mathrm{1}}{\mathrm{X}\mathrm{2}}$$

   

   and X1 =C+5 N

   and X2 = 0.5 Ti + Nb + 0.5 V.
2. An alloy according to claim 1, comprising (in % by mass):

   B > 0.002 - < 0.005 %.
3. An alloy according to claim 1 or 2, comprising (in % by mass):

   Mn ≤ 0.3 %.
4. An alloy according to one of the claims 1 through 3, characterized in that the percentage of carbides is > 0.9 %.
5. A use of the alloy according to one of the claims 1 through 4 as forged parts for components in gas and steam turbines.
6. A use of the alloy according to one of the claims 1 through 4 as weldment for gas and steam turbines.
7. A use of the alloy according to one of the claims 1 through 4 as boiler components for power plants of the energy technology.
8. A use of the alloy according to one of the claims 1 trough 4 in the furnace and power plant construction.
9. A use of the alloy according to one of the claims 1 through 4 in the petrochemical industry as well as in the field of nuclear energy technique.
10. A use of the alloy according to one of the claims 1 through 4 as cast parts for gas and steam turbines as well as in the furnace and power plant construction.
11. A use according to claim 10 as centrifugally cast construction parts.