Use of a nickel-iron-chromium alloy having high resistance in highly corrosive environments and simultaneously good processability and strength

Abstract

The invention relates to the use of a nickel-iron-chromium alloy having excellent high-temperature corrosion resistance as a powder, the powder consisting of spherical particles of a size of 5 to 250 pm, and said alloy comprising (in wt.%): 35.0 to 38% nickel, 26.0 to 30.0% chromium, > 0.7 to 1.50% silicon, 0.40 to 1.30% aluminium, 0.00 to 1.0% manganese, 0.0001 to 0.05% each of magnesium and / or calcium, 0.015 to 0.12% carbon, 0.001 to 0.150% nitrogen, 0.001 to 0.030% phosphorus, 0.0001 to 0.020% oxygen, a maximum of 0.010% sulphur, less than 1.0% molybdenum, less than 1.0 % cobalt, less than 0.5% copper, less than 1.0% tungsten, the remainder being iron and the usual process-related impurities, it being necessary to satisfy the following equation: Fc = - 1.2 + 0.29*Ni - 4.6*Si - 4.4*AI < 2.5 (1 a), where Ni, Si and AI are the concentration of the elements in question in wt.%.

Description

[0001] Use of a nickel-iron-chromium alloy with high resistance in highly corrosive environments while maintaining good processability and strength

[0002] The invention relates to the use of a nickel-iron-chromium alloy with good high-temperature corrosion resistance in highly corrosive environments and at the same time good processability and strength.

[0003] Austenitic nickel-iron-chromium alloys with varying nickel, chromium, and iron contents have long been used in furnace construction and in the chemical and petrochemical industries. These applications require good high-temperature corrosion resistance, even in highly corrosive environments such as carburizing, sulfidizing, and chlorinating environments, as well as good high-temperature strength.

[0004] In general, it should be noted that the high-temperature corrosion resistance of the alloys listed in Table 1 increases with increasing chromium content. All of these alloys form a chromium oxide layer (Cr20s) with an underlying, more or less continuous, silicon oxide layer. Small additions of elements with a strong oxygen affinity, such as yttrium or cerium, improve corrosion resistance. The chromium content is slowly consumed over the course of use in the application to build up the protective layer. Therefore, a higher chromium content increases the service life of the material, since a higher content of the element chromium, which forms the protective layer, delays the point at which the chromium content falls below the critical limit and oxides other than Cr203 form, such as iron-containing and nickel-containing oxides. A further increase in high-temperature corrosion resistance can be achieved by adding silicon or aluminum.Above a certain minimum concentration, these elements form a continuous layer beneath the chromium oxide layer, thus reducing chromium consumption. In carburizing environments (CO, H2, CH4, CO2, H2O mixtures), carbon can penetrate the material, leading to the formation of internal carbides. These cause a loss of impact toughness. Transformation processes can also occur due to chromium depletion of the matrix.

[0005] High resistance to carburization is achieved by materials with low carbon solubility and a low carbon diffusion rate. Nickel alloys are therefore generally more resistant to carburization than iron-based alloys because both carbon diffusion and carbon solubility are lower in nickel than in iron. Increasing the chromium content results in greater carburization resistance through the formation of a protective chromium oxide layer, unless the oxygen partial pressure in the gas is insufficient to form this protective chromium oxide layer. At very low oxygen partial pressures, materials can be used that form a layer of silicon oxide or the even more stable aluminum oxide; both of these can form protective oxide layers even at significantly lower oxygen contents.

[0006] In carburizing, sulfidizing environments with low oxygen partial pressure (CO, H2, H2O, CO2, H2S mixtures), sulfur can penetrate the material, potentially leading to the formation of sulfides. The melting point can also drop to very low values ​​(635°C for the Ni-NisS2 eutectic, 988°C for the Fe-FeS eutectic). High-nickel nickel-iron-chromium alloys are often more sensitive in sulfidizing environments than high-ferrous nickel-iron-chromium alloys. Here, too, a further increase in high-temperature corrosion resistance can be achieved by adding silicon or aluminum.

[0007] In chlorinating environments with low oxygen partial pressures, volatile metal chlorides with high vapor pressures and / or low melting points can form, thus generating high corrosion rates. A high content of chromium and / or nickel improves corrosion resistance. DE 41 30 139 C1 describes a heat-resistant, hot-formable austenitic nickel alloy consisting of (in mass %) 0.05 to 0.15% carbon, 2.5 to 3.0% silicon, 0.2 to 0.5% manganese, max. 0.015% phosphorus, max. 0.005% sulfur, 25 to 30% chromium, 20 to 27% iron, 0.05 to 0.15% aluminum, 0.001 to 0.005% calcium, 0.05 to 0.15% rare earths, 0.05 to 0.20% nitrogen, with the remainder nickel and the usual impurities resulting from the melting process.

[0008] The alloy described in DE 41 30 139 C1 is known under the designations “NiCr28FeSiCe”, Alloy 45TM, Nicrofer 45TM or under the material number 2.4889 and is referred to below as “45TM”.

[0009] Alloy 45TM is highly resistant to carburizing and sulfidizing media, making it suitable for use in waste incineration plants or coal gasification plants. Figure 1 shows the metallographically measured corrosion attack depth for various alloys after 2100 hours of exposure in a PRENFLO coal gasification pilot plant in Fürstenhausen in a gas containing H2S as a function of temperature for various alloys. Table 1 shows the composition of the alloys tested according to the state of the art. A high chromium and silicon content significantly reduces the corrosion attack depth. Due to the high silicon content of > 2.5%, a silicon oxide layer can form beneath the protective chromium oxide layer, which results in the material's high corrosion resistance.45TM with 26 to 29% chromium and 2.5 to 3% silicon shows the lowest corrosion attack depth at all temperatures, followed by AC66 with 26 to 28% chromium and a maximum of 0.3% silicon.

[0010] However, alloy 45TM is very difficult to process. This is evident, for example, in the formation of cracks during hot forming. 45TM is also prone to cracking during welding, which makes native welding (using a filler metal in the composition range of the material to be welded), which would be advisable for corrosion protection reasons, impossible and complicates the practical use of the material. The reasons for the increased hot cracking in austenitic FeCrNi weld metals with primary austenite solidification are cited as the formation of low-melting phases due to silicon enrichment at the austenite grain boundaries (eutectic Fe-Fe2Si: 1212°C; eutectic NiSi-NisSi2: 964°C and NiSi: 996°C) and the expanding solidification range.

[0011] The alloy AC66 (composition see Table 1 ), on the other hand, has sufficient weldability and workability, but is not as corrosion-resistant in a coal gasification plant, as Figure 1 shows.

[0012] The demands on the material increase further when the carburizing, sulfidizing conditions are combined with attack by chlorine, as occurs in coal gasification plants, waste incineration plants, etc.

[0013] For materials used in carburizing, sulfidizing and chlorinating environments, especially atmospheres, a compromise must be made regarding composition.

[0014] High-temperature strength is improved, among other things, by a high carbon content. High contents of solid-solution strengthening elements such as chromium, aluminum, silicon, molybdenum, and tungsten also improve heat strength.

[0015] US 6,623,869 B1 describes a metallic material containing the following components in mass %: not more than 0.2% carbon, 0.01-4% silicon, 0.05-2% manganese, not more than 0.04% phosphorus, not more than 0.015% sulfur, 10-35% chromium, 30-78% nickel, not less than 0.005% aluminum but less than 4.5% aluminum, 0.005-0.2% nitrogen, and one or both of 0.015-3% copper and 0.015-3% cobalt, with the remainder being essentially iron. The value of 40 Si + Ni + 5 Al + 40 N + 10 (Cu + Co) is not less than 50, where the symbols of the elements represent the alloying content of the respective elements. The metallic material has excellent corrosion resistance in an environment where metal dusting may occur and can therefore be used in furnace tubes, piping systems, heat exchanger tubes, etc. in an oil refinery or petrochemical plant.It can significantly improve the durability and safety of the system.

[0016] US 3,833,358 A describes an iron-based refractory alloy offering high resistance to creep, thermal shock, thermal fatigue and intergranular oxidation as well as good weldability, essentially consisting of the following elements (in parts by weight):

[0017] C 0.05-0.20

[0018] Ni 30-40

[0019] Cr 20 - 30

[0020] Nb 0.2-2

[0021] N 0.04-0.2

[0022] Mn 0.6-2

[0023] Si 0.6-2

[0024] Ta 0-0.3

[0025] Ti0-1

[0026] Mon 0-0.5

[0027] AI 0-0.05

[0028] Pb 0-0.01

[0029] Sn 0-0.01

[0030] Zn 0-0.01

[0031] Cu 0-0.25 and the remainder is essentially iron. The weight proportions of the aforementioned elements meet the following formulas

[0032] 30 * C% + Ni% + 0.5 * Mn% + 16 * N% =

[0033] Cr% + 0.5 * (Nb + 1 / 2 Ta)% + 3.5 * Ti% + 1.5* Si% + Mo% + (11 + / - 2)% A = B + / - 20% with A = 30*C% B = 2 * Ti% + 6 * (Nb + 1 / 2 Ta)%. US 3,865,581 A describes a heat-resistant alloy with hot formability, containing 0.01 to 0.5% C, 0.01 to 2.0% Si, 0.01 to 3.0% Mn, 22 to 80% Ni, and 10 to 40% Cr as the main components, together with one or both of 0.0005 to 0.20% B and 0.001 to 6.0% Zr, and further one or more of 0.001 to 0.5% Ce, 0.001 to 0.2% Mg, and 0.001 to 1.0% Be, the balance being iron and unavoidable impurities. It is suitable for use in furnace construction (burner tips, protective housings, thermocouple protection tubes, etc.).

[0034] DE 1024719 A describes a method for adding cerium and / or lanthanum to a nickel-iron alloy. This is a hot-formable alloy characterized by the following composition: 0 to 0.5% carbon, 10 to 60% of one or more of the elements chromium, molybdenum, and tungsten, with the amount of each of these elements not exceeding 30%, 0 to 73% iron, 0.02 to 1.10% cerium or lanthanum or both, the remainder 4 to 70% nickel including impurities, with the proviso that the rare earth metal content is balanced with the nickel content as follows: % nickel % cerium or lanthanum or both

[0035] 4 about 0.02 to 1.10

[0036] 10 about 0.02 to 1.05

[0037] 20 about 0.02 to 0.90

[0038] 30 about 0.02 to 0.75

[0039] 40 about 0.02 to 0.60

[0040] 50 about 0.02 to 0.45

[0041] 60 about 0.02 to 0.30

[0042] 70 about 0.02 to 0.15

[0043] EP 0 812 926 A1 describes a nickel-based alloy whose strength increases with use, consisting of 0.06 - 0.14% carbon, 35 - 46% nickel, 22.5 - 26.5% chromium, 0 - 1.5% manganese, 0.5 - 2% silicon, 0.1 - 1% titanium, 0.05 - 2% aluminum, 1 - 3% molybdenum, 0.2 - 1% niobium, 0.1 - 1% tantalum, 0 - 0.3% tungsten, 0 - 0.008% boron, 0 - 0.05% zirconium and the remainder being iron and incidental impurities.

[0044] WO 2007 / 124996 A1 describes a reaction vessel for use in the production of hydrogen sulfide by reaction between sulfur and hydrogen, wherein the reaction vessel and, if applicable, connecting lines, fittings, and measuring and control elements are made partially or entirely of a material that is resistant to the reaction mixture and contains aluminum. In particular, the material contains the following components: 0-0.3% C, 0-2.5% Si, 0-2.5% Mn, 0-0.1% P, 0-0.3% S, 15.0-28.0% Cr, 0-1.0% Cu, 0-0.0% Fe (balance), 1.0-5.0% Al, 0-2.5% Co, 0-1.5% Ti, 0-0.4% Y, and up to 70% Ni (% by weight).

[0045] DE 10 2007 005 605 A1 describes an iron-nickel-chromium-silicon alloy containing (in wt. %) 34 to 42% nickel, 18 to 26% chromium, 1.0 to 2.5% silicon, and additions of 0.05 to 1% Al, 0.01 to 1% Mn, 0.01 to 0.26% lanthanum, 0.0005 to 0.05% magnesium, 0.01 to 0.14% carbon, 0.01 to 0.14% nitrogen, max. 0.01% sulfur, max. 0.005% boron, the remainder iron, and the usual process-related impurities. This alloy is used in heating elements.

[0046] US 5,021,215 A discloses a high-strength, heat-resistant steel with improved formability, which essentially consists of (wt%):

[0047] C: 0.05 - 0.30%, Si: not more than 3.0%

[0048] Mn: not more than 10%, Cr: 15 - 35%,

[0049] Ni: 15 - 50%, Mg: 0.001 - 0.02%,

[0050] B: 0.001 - 0.01%, Zr: 0.001 - 0.10%, at least one element of Ti: 0.05 - 1.0%, Nb: 0.1 - 2.0%, and

[0051] AI: 0.05 - 1.0%,

[0052] Mon: 0 - 3.0%, Winter: 0 - 6.0%,

[0053] (Mo + 1 / 2 W = 3.0% or less) balance Fe and incidental impurities, wherein the impurities oxygen and nitrogen are limited to 50 ppm or less and 200 ppm or less, respectively, and wherein the austenite grain size number is limited to No. 4 or coarser.

[0054] JPS 56163244 A describes the improvement of hot workability and oxidation resistance of an austenitic steel by adding a specific amount of C, Si, Mn, Ni, Cr, Al, B, a rare earth element, and Ca to the steel. This is achieved by an austenitic steel containing the following composition in wt%: <0.2% C, 1.5-3.5% Si, <2% Mn, 8-35% Ni, 15-30% Cr, <2% Al, 0.0005-0.005% B, 0.005-0.1% of a rare earth element, and 0.0005-0.02% Ca, or additionally adding 0.0005-0.03% Mg if required. The resulting austenitic steel is refined in an ordinary steelmaking furnace, and this molten steel is formed into a billet, which is then hot-rolled.

[0055] US 7,118,636 B2 describes a nickel-iron-chromium alloy containing a strengthening phase capable of maintaining a fine grain structure during forging and processing of the alloy at high temperatures. The alloy contains sufficient amounts of titanium, zirconium carbon, and nitrogen to form fine titanium and zirconium nitride, even though these are close to their solubility limit in the molten state of the alloy. When an article is manufactured from such an alloy by thermomechanical processing, a dispersion of the fine titanium and zirconium carbonitride precipitates forms during solidification of the melt and remains in the alloy during subsequent processing steps (at elevated temperatures) to prevent austenitic grain growth. The nickel-iron-chromium alloy contains less than 0.05 wt.-% niobium, at least 0.05% zirconium, at least 0.05% carbon, at least 0.05% nitrogen, a carbon to nitrogen weight ratio of at least 1 to 2 to less than 1 to 1, sufficient titanium, zirconium and / or aluminum to be free from chromium carbides, and titanium, zirconium, carbon and nitrogen in sufficient quantities to form a uniform dispersion of fine titanium and zirconium carbonitride [(Ti. x Zn- x ) (C y Ni- y)] in a sufficient amount near the solubility limit of the titanium and zirconium carbonitride precipitates in a molten state of the alloy. This nickel-iron-chromium alloy also consists of about 32 wt.% to about 38 wt.% iron, about 22 wt.% to about 28 wt.% chromium, about 0.10 wt.% to about 0.60 titanium, about 0.05 wt.% to about 0.30 zirconium, about 0.05 wt.% to about 0.30 carbon, about 0.05 wt.% to about 0.30 nitrogen, about 0.05 wt.% to about 0.50 aluminum, up to 0.99 wt.% molybdenum, up to about 0.01 wt.% boron, up to about 1 wt.% silicon, up to about 1 wt.% manganese, the balance nickel and incidental impurities.

[0056] JPS 57134544 A describes the improvement of stress corrosion cracking resistance of oil drilling pipes by adding specific amounts of Mo, W, etc. to a high Cr-Ni steel as pipe material. For this purpose, an alloyed steel with a composition of < 0.10% C, < 1.0% Si, < 2.0% Mn, < 0.030% P, < 0.005% S, < 0.5% AI, 22.5-30% Cr, 25-60% Ni and Mo and / or W is used, which satisfies the equations

[0057] Cr(%) + 10*Mo(%) + 5*W(%) > 70%

[0058] 4% < Mo(%) + W(%) < 8%. This steel is used for oil well pipe used in the highly corrosive, harsh environment of an oil well, a natural gas well, etc. The alloy may contain < 1% Cu and / or < 2% Co and / or < 0.10% of one or more of the rare earth elements, < 0.20% Y, < 0.10% Mg, < 0.10% Ca, and < 0.5% Ti. It can be used to produce oil well pipe with superior stress corrosion cracking resistance in the highly corrosive environment of an oil well containing H2S, CO2, and Cl.

[0059] The object underlying this invention is therefore to design the use of a nickel-iron-chromium alloy which a) has good high-temperature corrosion resistance in a highly corrosive environment such as carburizing, sulfidizing and chlorinating environments, comparable to that of alloy 45TM, b) has sufficient processability, in particular weldability, as similar as possible to that of alloy AC66, and c) has sufficient high-temperature strength at 500°C similar to that of alloy AC66.

[0060] The object underlying this invention is achieved by using a nickel-iron-chromium alloy with excellent high-temperature corrosion resistance as a powder, wherein the powder consists of spherical particles with a size of 5 to 250 pm, and wherein this alloy contains (in mass%): 35.0 to 38% nickel, 26.0 to 30.0% chromium,

[0061] > 0.7 to 1.50% silicon,

[0062] 0.40 to 1.30% aluminum,

[0063] 0.00 to 1.0% manganese, 0.0001 to 0.05% each magnesium and / or calcium,

[0064] 0.015 to 0.12% carbon,

[0065] 0.001 to 0.150% nitrogen, 0.001 to 0.030% phosphorus, 0.0001 to 0.100% oxygen, maximum 0.010% sulfur, less than 1.0% molybdenum, less than 1.0% cobalt, less than 0.5% copper, less than 1.0% tungsten,

[0066] The remainder is iron and the usual process-related impurities, whereby the following relationship must be fulfilled: Fc = - 1 ,2 + 0.29*Ni - 4.6*Si - 4.4*AI < 2.5 (1 a), where Ni, Si and AI are the concentration of the respective elements in mass%.

[0067] Advantageous further developments of the subject matter of the invention can be found in the associated subclaims.

[0068] The nickel content is between 35.0 and 38.0%, with preferred contents being adjustable within the following ranges:

[0069] 35 or > 35.0 to < 38.0%

[0070] 35 or > 35.0 to 37 or < 37.0%.

[0071] The spread range for the element chromium is between 26.0 and 30.0%, with preferred ranges being set as follows:

[0072] > 26.0 to < 30.0%

[0073] 27.0 or > 27.0 to 30.0 or < 30.0%

[0074] 28.0 or > 28.0 to 30.0 or < 30.0%

[0075] The silicon content is between > 0.70 and 1.50%. Preferably, silicon can be adjusted within the range in the alloy as follows:

[0076] > 0.70 to < 1.50%

[0077] 0.80 or > 0.80 to 1.50 or < 1.50%

[0078] 0.90 or > 0.90 to 1.50 or < 1.50%

[0079] 0.80 or > 0.80 to 1.50 or < 1.50%

[0080] 0.80 or > 0.80 to 1.45 or < 1.45%.

[0081] The aluminum content is between 0.40 and 1.30%, whereby preferred aluminum contents can be set as follows:

[0082] > 0.40 to < 1.30%

[0083] 0.50 or > 0.50 to 1.30 or < 1.30%

[0084] 0.50 or > 0.50 to 1.20 or < 1.20%

[0085] 0.50 or > 0.50 to 1.10 or < 1.10%

[0086] 0.60 or > 0.60 to 1.10 or < 1.10%. The same applies to the element manganese, which can be present in the alloy at 0.0 to 1.0%. Alternatively, the following range is also conceivable:

[0087] > 0.0 to < 1.00%

[0088] > 0.0 to 0.50 or < 0.50%

[0089] > 0.0 to 0.05 or < 0.05%

[0090] 0.005 or > 0.005 to 0.20 or < 0.20%

[0091] 0.005 or > 0.005 to 0.10 or < 0.10%.

[0092] Magnesium and / or calcium are also present in concentrations of 0.0001 to 0.05%. These elements can preferably be adjusted in the alloy as follows:

[0093] 0.0001 to 0.030%

[0094] 0.0001 to 0.020%

[0095] 0.0002 to 0.015%

[0096] 0.0010 to 0.010%.

[0097] The alloy contains 0.015 to 0.12% carbon. This can preferably be adjusted within the alloy within the following range: > 0.015 to < 0.12%.

[0098] 0.03 or > 0.03 to 0.10 or < 0.10%

[0099] 0.04 or > 0.04 to 0.10 or < 0.10%

[0100] 0.05 or > 0.05 to 0.10 or < 0.10%

[0101] 0.05 or > 0.05 to 0.09 or < 0.09%.

[0102] This also applies to the element nitrogen, which is present in concentrations between 0.001 and 0.150%. Preferred concentrations can be as follows:

[0103] > 0.001 to < 0.150%

[0104] 0.010 or > 0.010 to 0.140 or < 0.140%

[0105] 0.020 or > 0.020 to 0.140 or < 0.140%

[0106] 0.050 or > 0.050 to 0.140 or < 0.140%. The alloy also contains phosphorus in amounts between 0.001 and 0.030%. Preferred contents can be as follows:

[0107] 0.001 to 0.015%.

[0108] The alloy also contains oxygen in concentrations between 0.0001 and 0.100%.

[0109] The element sulfur is present in the alloy at a maximum of 0.010%. Preferred contents can be as follows:

[0110] Sulfur max. 0.008%.

[0111] Molybdenum is present in the alloy at a content of less than 1.0%.

[0112] The molybdenum content can also be limited as follows:

[0113] Mo max. 0.50 or < 0.50%

[0114] Mo max. 0.20 or < 0.20%

[0115] Mo max. 0.10 or < 0.10%

[0116] Mo max. 0.05 or < 0.05%

[0117] Mo max. 0.02 or < 0.02%.

[0118] Furthermore, the alloy contains less than 1.0% cobalt. The cobalt content can be further limited as follows:

[0119] Co max. 0.50 or < 0.50%

[0120] Co max. 0.20 or < 0.20%

[0121] Co max. 0.10 or < 0.10%

[0122] Co max. 0.05 or < 0.05%

[0123] Co max. 0.015 or < 0.015%.

[0124] Furthermore, the alloy may contain less than 0.5% copper. The copper content may be further limited as follows:

[0125] Cu max. 0.30 or < 0.30%

[0126] Cu max. 0.10 or < 0.10%

[0127] Cu max. 0.05 or < 0.05% Cu max. 0.015 or < 0.015%.

[0128] Tungsten is contained in the alloy at a maximum concentration of 1.0%. The tungsten content can be further limited as follows:

[0129] W < 1.0%

[0130] W max. 0.50 or < 0.50%

[0131] W max. 0.20 or < 0.20%

[0132] W max. 0.10 or < 0.10%

[0133] W max. 0.05 or < 0.05%

[0134] W max. 0.02 or < 0.02%.

[0135] The remainder of the alloy consists of iron and the usual manufacturing-related impurities. The iron content can be further limited as follows:

[0136] 28.0 or > 28.0 to 38.0%

[0137] 29.0 or > 29.0 to 38.0%

[0138] 30.0 or > 30.0 to 38.0 or < 38.0%.

[0139] The following relationship between nickel, silicon and aluminum must be met to ensure sufficient resistance in carburizing, sulfidizing and chlorinating environments:

[0140] Fc = - 1 ,2 + 0.29*Ni - 4.6*Si - 4.4*AI < 2.5 (1 a), where Ni, Si and AI and Si are the concentration of the respective elements in mass%.

[0141] Preferred areas can be set with

[0142] Fc = - 1.2 + 0.29*Ni - 4.6*Si - 4.4*Al < 1.5 (1 b)

[0143] Fc = - 1.2 + 0.29*Ni - 4.6*Si - 4.4*Al < 1.0 (1c)

[0144] Additions of oxygen-affine elements such as cerium, lanthanum, yttrium, zirconium, and hafnium improve corrosion resistance. They do this by being incorporated into the oxide layer and blocking oxygen diffusion paths at the grain boundaries.

[0145] If required, the alloy may contain 0.001 to 0.20% of one or more of the elements cerium, lanthanum, yttrium, zirconium and hafnium, whereby the following formula must be met:

[0146] FRE = 0.714*Ce + 0.720*La + 1 ,124*Y + 1 ,096*Zr + 0.560*Hf < 0.10 (2a) where Ce, La, Y, Zr and Hf are the concentration of the respective elements in mass%.

[0147] Preferably, if at least one of the elements cerium, lanthanum, yttrium, zirconium and hafnium is present, FRE can be set as follows:

[0148] FRE = 0.714*Ce + 0.720*La + 1.124*Y + 1.096*Zr + 0.560*Hf < 0.075 (2b)

[0149] FRE = 0.714*Ce + 0.720*La + 1 .124*Y + 1 .096*Zr + 0.560*Hf < 0.065 (2c)

[0150] Alternatively, if cerium and lanthanum are present simultaneously, cerium mixed metal (abbreviation CeMM) can be used in contents of 0.001 to 0.20%, whereby FRE must be modified as follows:

[0151] FRE= 0.716*CeMM + 1 ,124*Y + 1 ,096*Zr + 0.560*Hf < 0.10 (3a) where CeMM, Y, Zr and Hf are the concentration of the respective elements in mass%.

[0152] Preferably, when adding cerium mischmetal, FRE can be adjusted as follows:

[0153] FRE = 0.716*CeMM + 1 .124*Y + 1 .096*Zr + 0.560*Hf < 0.075 (3b)

[0154] FRE = 0.716*CeMM + 1 .124*Y + 1 .096*Zr + 0.560*Hf < 0.065 (3c)

[0155] Preferably, cerium, lanthanum, cerium-mischmetal, zirconium and hafnium can be contained in the alloy within the spread range as follows:

[0156] > 0.001 to < 0.20%

[0157] 0.001 or > 0.001 to 0.15 or < 0.15%

[0158] 0.001 or > 0.001 to 0.10 or < 0.10%

[0159] 0.001 or > 0.001 to 0.08 or < 0.08% 0.001 or > 0.001 to 0.05 or < 0.05%

[0160] 0.001 or > 0.001 to 0.04 or < 0.04%.

[0161] 0.01 or > 0.01 to 0.04 or < 0.04%

[0162] Preferably, yttrium can be contained in the alloy within the spread range as follows:

[0163] > 0.001 to < 0.20%

[0164] 0.001 or > 0.001 to 0.15 or < 0.15%

[0165] 0.001 or > 0.001 to 0.10 or < 0.10%

[0166] 0.001 or > 0.001 to 0.08 or < 0.08%

[0167] 0.01 or > 0.01 to 0.08 or < 0.08%

[0168] 0.01 or > 0.01 to < 0.045%.

[0169] Optionally, the element titanium may be present in the alloy in amounts ranging from 0.0 to 0.50%. Preferably, titanium may be present in the alloy within the following range:

[0170] > 0.0 to < 0.50%

[0171] > 0.0 to 0.50 or < 0.50%

[0172] 0.001 or > 0.001 to 0.20 or < 0.20%

[0173] 0.001 or > 0.001 to 0.15 or < 0.15%

[0174] 0.001 or > 0.001 to 0.10 or < 0.10%

[0175] 0.001 or > 0.001 to 0.05 or < 0.05%

[0176] 0.001 or > 0.001 to 0.04 or < 0.04%.

[0177] 0.005 or > 0.005 to 0.20 or < 0.20%.

[0178] 0.010 or > 0.010 to 0.20 or < 0.20%.

[0179] Optionally, the element niobium can be included in the alloy in amounts ranging from 0.0 to 0.2%. Niobium can preferably be contained in the alloy within the following range:

[0180] > 0.0 to < 0.20%

[0181] > 0.0 to 0.15 or < 0.15%

[0182] > 0.0 to 0.10 or < 0.10% > 0.0 to 0.05 or < 0.05%

[0183] > 0.0 to 0.02 or < 0.02%

[0184] 0.001 or > 0.001 to 0.20 or < 0.20%

[0185] 0.010 or > 0.010 to 0.20 or < 0.20%.

[0186] Optionally, the alloy may also contain 0.0 to 0.20% tantalum. Preferred contents can be as follows:

[0187] > 0.0 to < 0.20%

[0188] > 0.0 to 0.10 or < 0.10%

[0189] > 0.0 to 0.05 or < 0.05%.

[0190] Optionally, the element boron can be included in the alloy in amounts of 0.0001 - 0.008%. Preferred contents can be as follows:

[0191] Boron 0.0005 - 0.008%

[0192] Boron 0.0005 - 0.005%

[0193] Boron 0.0005 - 0.004%.

[0194] Furthermore, the alloy may contain a maximum of 0.50% vanadium.

[0195] V < 0.50%

[0196] V max. 0.40 or < 0.50%

[0197] V max. 0.20 or < 0.20%

[0198] V max. 0.08 or < 0.10%

[0199] V max. 0.05 or < 0.05%

[0200] Finally, the elements lead, zinc and tin may be present as impurities in the following amounts:

[0201] Pb max. 0.002%, Zn max. 0.002%, Sn max. 0.002%

[0202] Then the element beryllium can be given as follows:

[0203] Be less than 0.001%. The powder according to the invention is preferably produced in a vacuum inert gas atomization system (VIGA). For this purpose, the alloy is first melted, optionally openly or in a vacuum, possibly with subsequent ESR and / or VAR remelting. The powder is then produced by atomizing the alloy melt in the vacuum inert gas atomization system (VIGA). In this system, the alloy is melted in a vacuum induction melting furnace (VIM) and fed into a pouring funnel leading to a gas nozzle in which the molten metal is atomized into metal particles with inert gas at high pressure of 5 to 100 bar. The melt is heated in the crucible at 5 to 400°C above the melting point. The metal flow rate during atomization is 0.5 to 80 kg / min and the gas flow rate is 2 to 150 m / s. 3 / min. Due to the rapid cooling, the metal particles solidify into spherical shapes (spherical particles). The inert gas used during atomization can contain 0.01 to 100% nitrogen, if required. The gas phase is then separated from the powder in a cyclone, and the powder is then packaged.

[0204] The particles have a particle size of 5 to 250 pm, gas inclusions of 0.0 to 4% pore area (pores > 1 pm) in relation to the total area of ​​evaluated objects, a bulk density of 2 to the density of the alloy of approx. 8.5 g / cm 3 and are packaged hermetically under a protective gas atmosphere with argon.

[0205] The particle size range of the powder is between 5 and 250 pm, with preferred ranges being between 5 and 150 pm and 10 and 150 pm. The preferred ranges are achieved by separating excessively fine and coarse particles using sieving and classifying processes. These processes are carried out under a protective gas atmosphere and can be repeated once or several times.

[0206] The powder has gas inclusions of 0.0 to 4% pore area (pores > 1 pm) in relation to the total area of ​​evaluated objects, with preferred ranges being 0.0 to 2%

[0207] 0.0 to 0.5%

[0208] 0.0 to 0.2%

[0209] 0.0 to 0.1%

[0210] 0.0 to 0.05%

[0211] The powder has a bulk density of 2 to the density of the alloy of approximately 8.5 g / cm 3 , whereby preferred ranges can be the following values.

[0212] 4 to 5 g / cm 3

[0213] 2 to 8 g / cm 3

[0214] 2 to 7 g / cm 3

[0215] 3 to 6 g / cm 3

[0216] The amount of gas inclusions in the powder allows for low residual porosity in the manufactured parts.

[0217] The inert gas used in powder production can be either argon or a mixture of argon with 0.01 to < 100% nitrogen. Possible limitations of the nitrogen content may include:

[0218] 0.01 to 80%

[0219] 0.01 to 50%

[0220] 0.01 to 30%

[0221] 0.01 to 20%

[0222] 0.01 to 10%

[0223] 0.01 to 10%

[0224] 0.1 to 5%

[0225] 0.5 to 10%

[0226] 1 to 5%

[0227] 2 to 3%.

[0228] Alternatively, the inert gas can be helium. The inert gas should preferably have a purity of at least 99.996 vol%. In particular, the nitrogen content should be between 0.0 and 10 ppmv, the oxygen content between 0.0 and 4 ppmv, and the H2O content should be < 5 ppmv.

[0229] In particular, the inert gas preferably has a purity of at least 99.999 vol%. In particular, the nitrogen content should be between 0.0 and 5 ppmv, the oxygen content between 0.0 and 2 ppmv, and the H2O content should be < 3 ppmv.

[0230] The dew point in the system is in the range of -10 to -120°C. It is preferably in the range of -30 to -100°C.

[0231] The pressure during powder atomization can preferably be 10 to 80 bar.

[0232] The powder produced from the alloy in this way can be used for any powder-based manufacturing process for producing components or layers on components.

[0233] The powder produced in this way can be used in particular for the additive manufacturing of components or layers on components.

[0234] Additive manufacturing also includes terms such as generative manufacturing, rapid technology, rapid tooling, rapid prototyping or the like.

[0235] In general, a distinction is made between:

[0236] 3D printing with powders,

[0237] Selective laser sintering and

[0238] Selective laser melting

[0239] Electron beam melting

[0240] Binder jetting

[0241] Laser cladding

[0242] High-speed laser cladding

[0243] Ultra-high-speed laser cladding, selective electron beam welding, or the like.

[0244] The components or layers on components produced using additive manufacturing are constructed from layer thicknesses ranging from 5 to 600 pm and, immediately after production, have a textured microstructure with grains elongated in the construction direction and an average grain size of 2 to 1000 pm. The preferred range is between 5 and 600 pm.

[0245] The powder produced from the alloy can be used for binder jetting processes. In this process, components are built up layer by layer. However, unlike laser reflow processes, an organic binder is locally introduced to ensure the cohesion of the powder particles. After the binder has hardened, the so-called green part is freed from any unbound powder and subsequently debound and sintered.

[0246] For the powder produced from the alloy, processes and additional devices for preheating and postheating can be advantageous. One example is the electron beam melting (EBM) process. The powder bed is selectively melted layer by layer using an electron beam. The process takes place under high vacuum. Therefore, this process is particularly suitable for hard materials with lower ductility and / or for reactive materials. The preheating and / or postheating device can also be implemented in laser-based processes.

[0247] In addition, the powder produced from the alloy can, if required, be used to manufacture components using HIP (hot isostatic pressing) or conventional sintering and extrusion processes. Furthermore, a combination of additive manufacturing and subsequent HIP treatment is possible. If required, it is also possible to subsequently carry out hot forming and / or cold forming, or alternating hot and cold forming. For hot forming, the component can be annealed at temperatures between 800 and 1290°C for 0.1 to 70 hours, followed by hot forming, possibly with intermediate annealing between 800 and 1290°C for 0.05 to 70 hours. The surface of the material can be chemically and / or mechanically removed for cleaning (even several times) during and / or at the end of hot forming. For cold forming, cold forming can be carried out with degrees of deformation of up to 98%, if necessary.with intermediate annealing between 800 and 1250°C for 0.05 minutes to 70 hours, if necessary under protective gas such as argon or hydrogen, followed by cooling in air, in the moving annealing atmosphere or in a water bath.

[0248] The components or coatings on components produced from the powder using various processes can optionally be subjected to solution annealing in the temperature range from 700 to 1250°C for 0.1 minutes to 70 hours, if necessary under a protective gas such as argon or hydrogen, followed by cooling in air, in a moving annealing atmosphere, or in a water bath. The surface can then be cleaned or machined by pickling, blasting, grinding, turning, peeling, or milling. This processing can be carried out partially or entirely even before annealing.

[0249] The components or coatings on components produced from the powder have an average grain size of 2 pm to 2000 pm after annealing. The preferred range is between 20 and 600 pm.

[0250] The components or layers on components produced from the powder according to the invention should preferably be used in areas in which highly corrosive conditions prevail, such as carburizing or sulfidizing or chlorinating environments or carburizing and chlorinating environments or carburizing and chlorinating environments or carburizing and sulfidizing and chlorinating environments, in particular atmospheres. These environments occur, for example, in components in waste incineration plants, in pyrolysis plants, in refinery furnaces, in the chemical industry, in coal gasification plants and in industrial furnace construction, for activated carbon filters, waste pyrolysis and in precious metal recovery.

[0251] Examples:

[0252] Tests carried out

[0253] The assessment of high-temperature corrosion resistance in highly corrosive conditions is carried out using the example of a carburizing, sulfidizing and chlorinating environment via the resistance of the material in a flowing synthetic gas atmosphere with these properties at elevated temperatures (at the Dechema).

[0254] For this purpose, samples measuring 20 x 8 x 4 mm 3cut from the semi-finished product of the respective alloys, then drilled with a 3 mm diameter hole, and then wet-ground with SiC paper to 1200 grit (grain size ~15 μm). The samples were degreased and cleaned in an ultrasonic bath with isopropanol. Each sample was suspended in the reaction vessel via this hole over a ceramic crucible so that any flaking corrosion products were collected. The mass of the flaking could be determined by weighing the crucible containing the corrosion products. The sum of the mass of the flaking and the mass change of the samples is the gross mass change of the sample. The specific mass change is the mass change relative to the surface of the samples. These are referred to below as rriNet for the specific net mass change, mGross for the specific gross mass change, m S paii stands for the specific mass change of the flaked oxides.

[0255] A gas mixture consisting of 60% CO, 30% H2, 4% CO2, 1% H2S, 0.05% HCl, and 3.95% H2O flowed through the reaction vessel. This mixture has a carburizing (60% CO), sulfidizing (1% H2S), and chlorinating (0.05% HCl) effect. Tests were conducted at 500°C. The test duration was 1056 hours each, divided into 11 cycles of 96 hours each. Each test included two samples per alloy. The values ​​given are the averages of these two samples.

[0256] In the following tests, an alloy is considered to be resistant in carburizing, sulfidizing and chlorinating environments if it has a

[0257] Gross mass gain of < 2.0 mg / cm 2 (4) shows.

[0258] This is the case when the following relationship between nickel, silicon and aluminum is fulfilled:

[0259] Fc = - 1 ,2 + 0.29*Ni - 4.6*Si - 4.4*AI < 2.5 (1 a), where Ni, Si and AI and Si are the concentration of the respective elements in mass%.

[0260] Weldability is assessed based on the extent of hot cracking during welding. The greater the risk of hot cracking, the worse the weldability of a material.

[0261] To quantify their susceptibility to hot cracking, the various alloys were tested using the MVT (Modified Varestraint Transvarestraint) test at the BAM (Federal Institute for Materials Research and Testing). For this test, a sample measuring 100 mm x 40 mm x 10 mm is machined from the alloy. During the MVT test, a TIG (Tungsten Inert Gas) weld is applied lengthwise across the top of this sample in a fully mechanized process at a constant feed rate. When the arc passes the center of the sample, a defined bending strain is applied to the sample. The samples were bent longitudinally to the welding direction (Varestraint mode). During this bending phase, hot cracks form in a localized test zone on the MVT sample. The tests were carried out with 4% bending strain, a die speed of 2 mm / s, and a heat input of 7.5 kJ / cm, each under pure argon 4.8.

[0262] For the evaluation, the lengths of all solidification cracks and remelting cracks visible on the sample under a light microscope at 25x magnification are determined and summed. Based on these results, the material can then be classified into the categories "hot crack resistant" (range 1), "increasing hot crack tendency" (range 2), and "hot crack prone" (range 3), as shown in Table 2.

[0263] In the following tests, alloys are considered to be readily weldable if they fall into zone 1 "hot crack resistant" and zone 2 "increasing hot crack susceptibility" in the MVT test, since the weldable alloy according to the state-of-the-art AC66 test method falls into zone 2. Alloys that are in zone 3, which is susceptible to hot cracking, are generally difficult to weld. In particular, welding with a filler metal of the same type (comparable composition to the material to be welded) is difficult or even impossible.

[0264] The assessment of the high-temperature strength was determined by hot tensile tests. This is determined in a tensile test according to DIN EN ISO 6892-2 at the desired temperature. The yield strength R P o,2, the tensile strength Rm and the elongation A at break were determined. The tests were carried out on round specimens with a diameter of 6 mm in the measuring range and an initial gauge length Lo of 30 mm. The yield strength R P o,2 or the tensile strength Rm at 500°C should at least reach the minimum values ​​for the alloy AC66 according to the state of the art:

[0265] 500°C: R P O.2 > 95 MPa or Rm > 115 MPa (5a, 5b)

[0266] It would be desirable for them to be better than the minimum values ​​of the state-of-the-art alloy 45TM.

[0267] 500°C: R P O.2 — 150 MPa or Rm > 500 MPa. (6a, 6b)

[0268] The grain size is determined using a line-intercept method.

[0269] To determine the properties of the components made from the powder, alloys melted in a vacuum furnace are used on a laboratory scale.

[0270] Tables 3a and 3b show the analyses of the laboratory-scale melted batches along with some commercially produced state-of-the-art batches of AC66 (1.4877) and 45TM (2.4889) used for comparison. The state-of-the-art batches are marked with a T, and the inventive batches with an E. The laboratory-scale melted batches are marked with an L, and the commercially produced batches with a G.

[0271] The ingots of the laboratory-scale vacuum-melted alloys in Tables 3a and 3b were annealed between 900 and 1270°C for 8 hours and then hot-rolled to a final thickness of 13 and 6 mm, respectively, by hot rolling and further intermediate annealing between 900 and 1270°C for 0.1 to 1 hour. The resulting sheets were solution-annealed between 800 and 1250°C for 1 hour. The samples required for the measurements were prepared from these sheets.

[0272] For the large-scale melted alloys, a sample was taken from a factory-produced sheet of the appropriate thickness. The samples required for the measurements were made from these sheets.

[0273] All alloy variants typically had a grain size of 50 to 190 pm.

[0274] For the example batches in Table 3a and b), the following properties are compared: the high-temperature corrosion resistance in carburising, sulphidising and chlorinating environment as an example of high corrosion resistance in a highly corrosive environment the weldability using MVT tests the creep resistance using hot tensile tests

[0275] The results are summarized in Table 4.

[0276] Table 4 shows the results of the corrosion test in terms of gross mass change and spalling at 500°C after 1056 hours in an atmosphere of 60% CO, 30% H2, 4% CO2, 1% H2S, 0.05% HCl, and 3.95% H2O. All tested alloys have a chromium content of approximately 27 to 28%. The state-of-the-art alloy AC66, with only 0.2% silicon, shows by far the largest gross mass change of 10.92 mg / cm3. 2The state-of-the-art alloy 45TM with 2.6% silicon and all tested batches melted on a laboratory scale with a silicon content greater than 1.0% show a gross mass change of less than or equal to 2.0 mg / cm 2 (2209, 250098, 250101, 250105, 250102 and 250107). If the aluminum content is greater than 0.40%, a batch with a silicon content of less than or equal to 1.0% can also have a gross mass change of less than or equal to 2.0 mg / cm 2 if formula (1a) Fc < 2.5 is simultaneously satisfied. This is the case for batches 250084 (Si = 0.59% and AI = 0.95%), 250085 (Si = 0.90% and AI 0.98%), 250106 (Si = 0.98% and AI 0.80%), and 250108 (Si = 0.70% and AI = 0.86%).

[0277] Batches 250084, 250106, 250105, 250108 and 250107 are in accordance with the invention, whereas batch 2209 with a silicon content of greater than 1.50% and batch 250098 with a nickel content of 44.0% are not.

[0278] Batch 250098 (Si = 1.20% and Al = 0.85%) shows a comparable or higher gross mass increase compared to batches 250106 (Si = 0.98% and Al = 0.80%) and 250101 (Si = 1.01% and Al = 0.75%), despite a significantly increased silicon content of 1.2%. Batch 250098 (Ni = 44.0%) has a significantly higher nickel content compared to batches 250106 (Ni = 35.6%) and 250101 (Ni = 38.2%). This shows that a higher nickel content worsens corrosion. The upper limit for nickel is therefore set at a maximum of 40%.

[0279] For the non-inventive batch 250100 (Ni = 38.2%, Si = 0.99% and Al = 0.43%) with a gross mass increase (3.43 mg / cm 2 ) of significantly greater than 2.0 mg / cm 2The aluminum content is slightly too low, so that formula (1a) is not fulfilled, in contrast to batch 250101 (Ni = 38.2%, Si = 1.01% and Al = 0.75%). In the non-inventive batches 250103 (Ni = 38.2%, Si = 0.36% and Al = 0.82%) and 250099 (Ni = 38.4%, Si = 1.00% and Al = 0.20%), which also have a gross mass increase (8.01 mg / cm 2 or 5.35 mg / cm 2 ) of significantly greater than 2.0 mg / cm 2 the silicon and aluminum content is outside the claimed limits and, in addition, formula (1a) is not fulfilled.

[0280] The alloys 250084 and 250106 according to the invention still show spalling. If the formula (1c) Fc < 1 .0 is also fulfilled, these alloys no longer show spalling (250107) and, surprisingly, at moderate silicon contents, also have a very low gross mass change of well below 1 .0 mg / cm 2in the order of 45TM with 2.6% silicon and 0.16% aluminum.

[0281] Table 4 shows the weldability classification of the alloys using the MVT test. The state-of-the-art weldable alloy AC66 is in Range 2. Alloy 45TM is classified in Range 3 (hot cracking prone) and thus has a strong tendency to crack formation, which makes welding difficult and makes welding with a similar filler metal difficult or even impossible.

[0282] Batches not according to the invention with a silicon content greater than or equal to 1.50% greater than 1.50% (45TM, batches 2091, 2099, 2100, 2200, 2203, 2207, 2208, 2209) are all in range 3. Of the batches with a silicon content of around 1.4%, the batches with an aluminum content below 0.1% are in range 2 (batches 2093, 2101), and those with a higher aluminum content are already in range 3 (batches 2103, 2096, 2097, 2098). The batches with a silicon content of less than 1.3% are all in range 1 or 2 (AC66, batches 2095, 2102, 250084 to 250108). All laboratory batches according to the invention are in range 1 (batches 250084, 250106, 250105, 250108 and 250107) or range 2 (batch 250102).

[0283] The results of the hot tensile tests at 500°C in the table show that for all alloys according to the invention melted on a laboratory scale, the yield strength R Po,2 is greater than or equal to 153 MPa, thus significantly exceeding the minimum of 95 MPa for AC66. They also exceed the minimum of 150 MPa for 45TM, albeit not significantly (see Formulas 5a and 6a). Likewise, the tensile strength Rm of all alloys according to the invention is greater than or equal to 192 MPa, thus also significantly exceeding the minimum of 115 MPa for AC66 (see Formula 5b). All hot tensile tests at 500°C showed an elongation of greater than 35%.

[0284] The claimed limits for the alloys “E” according to the invention as powder can therefore be justified in detail as follows:

[0285] A relatively low nickel content (with a higher iron content (balance)) promotes low corrosion in highly corrosive environments, such as carburizing, sulfidizing, and chlorinating atmospheres. Therefore, a nickel content of 40% is the upper limit. Too low a nickel content (with too high an iron content (balance)) promotes sigma phase formation, especially with high chromium and silicon contents. Therefore, a nickel content of 35% is the lower limit.

[0286] Chromium improves corrosion resistance in highly corrosive environments, such as carburizing, sulfiding, and chlorinating atmospheres. Too low a chromium content means that the chromium concentration drops very quickly below the critical limit when the alloy is used in a highly corrosive environment, preventing the formation of a continuous chromium oxide layer. Therefore, 26% chromium is the lower limit for chromium when used in highly corrosive environments, such as carburizing, sulfiding, and chlorinating atmospheres. Too high a chromium content promotes sigma phase formation in the alloy, especially at high chromium contents. Therefore, 30% chromium is considered the upper limit.

[0287] Silicon improves corrosion resistance in highly corrosive environments, such as carburizing, sulfiding, and chlorinating atmospheres. Therefore, a minimum content of 0.40% is required. Excessively high levels impair weldability and promote sigma phase formation, especially at high chromium contents. The silicon content is therefore limited to 1.50%.

[0288] A certain amount of aluminum improves corrosion resistance in highly corrosive environments, such as carburizing, sulfidizing, and chlorinating atmospheres. A minimum content of 0.40% is therefore required. Excessively high levels, in turn, impair weldability, especially with high chromium and silicon contents. The aluminum content is therefore limited to 1.30%.

[0289] Manganese is useful for improving workability. Manganese is limited to 1.0% because this element reduces high-temperature corrosion resistance.

[0290] Even very low magnesium and / or calcium contents improve processing by binding sulfur, thus preventing the formation of low-melting NiS eutectics. A minimum magnesium and / or calcium content of 0.0001% is therefore required. Excessively high contents can result in the formation of intermetallic Ni-Mg or Ni-Ca phases, which significantly impair processability. The magnesium and / or calcium content is therefore limited to a maximum of 0.05%. A minimum carbon content of 0.015% is necessary for good creep resistance. Carbon is limited to a maximum of 0.12%, as above this content, this element reduces processability due to the excessive formation of primary carbides.

[0291] A minimum nitrogen content of 0.001% is required, which improves the material's workability and high-temperature strength. Nitrogen is limited to a maximum of 0.150%, as this element reduces workability by forming coarse carbonitrides.

[0292] The phosphorus content should be less than or equal to 0.030%, as this surfactant impairs high-temperature corrosion resistance. Too low a phosphorus content increases costs. Therefore, the phosphorus content should be > 0.001%.

[0293] The oxygen content must be less than or equal to 0.100% to ensure the alloy's manufacturability. Too low an oxygen content increases costs. Therefore, the oxygen content should be > 0.0001%.

[0294] Sulfur levels should be kept as low as possible, as this surfactant impairs high-temperature corrosion resistance. Therefore, a maximum of 0.010% sulfur is specified.

[0295] Molybdenum is limited to less than 1.0% because this element reduces high-temperature corrosion resistance.

[0296] Tungsten is limited to less than 1.0% because this element also reduces high-temperature corrosion resistance.

[0297] Cobalt may be present in this alloy at less than 1.0%. Higher contents reduce high-temperature corrosion resistance. Copper is limited to less than 0.5% because this element reduces high-temperature corrosion resistance.

[0298] The following relationship between nickel, silicon and aluminum must be met to ensure sufficient resistance in a highly corrosive environment such as a carburizing, sulfidizing and chlorinating environment:

[0299] Fc = - 1.2 + 0.29*Ni - 4.6*Si - 4.4*AI < 2.5 (1a), where Ni, Si, and AI are the concentrations of the respective elements in mass %. The limit for Fc has been explained in detail in the previous text.

[0300] If necessary, high-temperature corrosion resistance can be further improved by adding oxygen-affine elements. They do this by being incorporated into the oxide layer and blocking oxygen diffusion paths at the grain boundaries.

[0301] A minimum content of 0.001% of one or more of the elements cerium, lanthanum, cerium mischmetal, yttrium, zirconium, and hafnium is required to achieve the high-temperature corrosion resistance-enhancing effect. For cost reasons, the upper limit for each element is set at 0.20%. The following formula must be met:

[0302] FRE = 0.714*Ce + 0.720*La + 1.124*Y + 1.096*Zr + 0.560*Hf < 0.10 (2a) where Ce, La, Y, Zr, and Hf are the concentrations of the respective elements in mass%. This formula limits the total content of elements such as cerium, lanthanum, yttrium, zirconium, and hafnium. Concentrations with FRE > 1.0 can increase corrosion rates and impair workability.

[0303] Titanium can be added if necessary. Titanium increases high-temperature strength. Above 0.50%, high-temperature corrosion resistance can be impaired, which is why 0.50% is the maximum value. Niobium can be added if necessary, as niobium also increases high-temperature strength. Higher contents significantly increase costs. The upper limit is therefore set at 0.20%.

[0304] If necessary, the alloy can also contain tantalum, as tantalum also increases high-temperature strength. Higher contents significantly increase costs. The upper limit is therefore set at 0.20%. A minimum content of 0.001% is required to achieve an effect.

[0305] If necessary, boron can be added to the alloy, as it improves creep resistance. Therefore, a minimum content of 0.0001% should be present. At the same time, this surfactant impairs high-temperature corrosion resistance. Therefore, a maximum of 0.008% boron is specified.

[0306] If necessary, vanadium is limited to a maximum of 0.50%, as this element reduces high-temperature corrosion resistance.

[0307] Where necessary, lead is limited to a maximum of 0.002%, as this element reduces high-temperature corrosion resistance. The same applies to zinc and tin.

[0308] A particle size that is too small below 5 pm impairs the flow behavior and should therefore be avoided; a particle size that is too large above 250 pm impairs the behavior in additive manufacturing.

[0309] A too low bulk density of 2 g / cm 2deteriorates the performance during additive manufacturing. The highest possible bulk density of approximately 8 g / cm 3 is determined by the density of the alloy. Table 1: State-of-the-art alloy compositions according to EN and UNS*), all values ​​in mass %. *) nified Numbering System for Metals and Alloys

[0310] Table 2: Weldability classification according to the total length of solidification and remelting cracks in mm (of the MVT Modified Varestraint-Transvarestraint) - hot crack tests of the BAM (Federal Institute for Materials Research and Testing).

[0311] Table 3a: Composition of the laboratory batches and the large-scale reference batches, Part 1. All values ​​in mass% (T: state-of-the-art alloy, E: alloy according to the invention, L: melted on a laboratory scale, G: melted on an industrial scale).

[0312] Table 3b: Composition of the laboratory batches and the large-scale reference batches, Part 2. All values ​​are in mass-% (For all alloys: W: <0.01; Y < 0.01; Pb: max. 0.002%, Zn: max. 0.002%, Sn: max. 0.002%) (Meaning of T, E, G, L, see Table 3a).

[0313] Table 4: Results of a) the corrosion test at 500°C after 1056 hours in an atmosphere of 60% CO, 30% H2, 4% CO2, 1% 2S, 0.05% HCl and 3.95% H2O, b) the weldability classification by MVT test and c) the hot tensile tests at 500°C.

[0314] Character description

[0315] Figure 1 : Corrosion attack depth of different alloys after aging for 2100 hours in a Prenflo pilot plant in a FhS-containing gas as a function of temperature.

Claims

Patent claims 1. Use of a nickel-iron-chromium alloy with excellent high-temperature corrosion resistance as a powder, wherein the powder consists of spherical particles of a size of 5 to 250 pm, and wherein this alloy comprises (in wt-%): 35.0 to 38% nickel, 26.0 to 30.0% chromium, > 0.7 to 1.50% silicon, 0.40 to 1.30% aluminum, 0.00 to 1.0% manganese, 0.0001 to 0.05% each of magnesium and / or calcium, 0.015 to 0.12% carbon, 0.001 to 0.150% nitrogen, 0.001 to 0.030% phosphorus, 0.0001 to 0.100% oxygen, maximum 0.010% sulfur, less than 1.0% molybdenum, less than 1.0% cobalt, less than 0.5% copper, less than 1.0% tungsten, Residual iron and the usual process-related impurities, whereby the following relationship must be satisfied: Fc = - 1 ,2 + 0.29*Ni - 4.6*Si - 4.4*AI < 2.5 (1a), where Ni, Si and AI are the concentrations of the elements concerned in mass %.

2. Use according to claim 1 with a nickel content of > 35.0 to < 38.0 %.

3. Use according to one of claims 1 to 2 with a chromium content of > 26.0 to 30.0%. Use according to any one of claims 1 to 3 with an aluminum content of > 0.50% or > 0.50% to < 1.30%. Use according to any one of claims 1 to 4 with a residual iron content of 28.0% or > 28.0% to 38.0%. Use according to any one of claims 1 to 5 containing 0.001% to 0.20% of one or more of the elements cerium, lanthanum, yttrium, zirconium, and hafnium, wherein the following formula must be satisfied: FRE = 0.714*Ce + 0.720*La + 1.124*Y + 1.096*Zr + 0.560*Hf < 0.10 (2a) where Ce, La, Y, Zr, and Hf are the concentrations of the elements in mass percent. Use according to one of claims 1 to 6, wherein, in the simultaneous presence of cerium and lanthanum, cerium mischmetal (abbreviated CeMM) is also used in contents of 0.001 to 0.20%, wherein FRE must be modified as follows: FRE = 0.716*CeMM + 1.124*Y + 1.096*Zr + 0.560*Hf < 0.10 (3a) where CeMM, Y, Zr, and Hf are the concentrations of the respective elements in mass percent. Use according to any one of claims 1 to 7, optionally with a titanium content of 0.0 to 0.50%. Use according to any one of claims 1 to 8, optionally with a niobium and / or tantalum content of 0.0 to 0.50% each. Use according to any one of claims 1 to 9, optionally with a boron content of 0.0001 to 0.008%. RECTIFIED SHEET (RULE 91 ) ISA / EP Use according to any one of claims 1 to 10, further optionally containing a maximum of 0.50% vanadium. Use according to any one of claims 1 to 11, wherein the impurities are adjusted to levels of max. 0.002% lead, max. 0.002% tin, max. 0.002% zinc. Use according to any one of claims 1 to 12, wherein the powder is produced by means of a vacuum inert gas atomization (VIGA) system. Use according to any one of claims 1 to 13 for any powder-using manufacturing process for the production of components or layers on components. Use according to any one of claims 1 to 14 for additive manufacturing. Use according to any one of claims 1 to 15 as a component or in a component in the chemical industry. Use according to any one of claims 1 to 15 as a component or in a component in a waste incineration or waste pyrolysis plant.

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