Application of nickel-chromium-molybdenum alloy

Abstract

The invention relates to the use of an alloy of the following composition in mass% as a plating material in the field of heat recycling and alternative material incineration plants: Cr 20.0-23.0%, Mo 18.5-21.05%, Fe < = 1.5%, Mn < = 0.5%, Si < = 0.1%, Co < = 0.3%, W < = 0.3%, Cu < = 0.5%, Al < = 0.4%, C < = 0.01%, P < = 0.015%, S < = 0.01%, N 0.02-0.15%, optionally V < = 0.3%, Nb < = 0.2%, Ti < = 0.02%, with the balance being Fe and unavoidable impurities. And the balance of Ni and impurities caused by melting.

Description

[0001] This application is a divisional application of patent application number 201780071437.6.

[0002] This invention relates to the use of a nitrogen-alloyed nickel-chromium-molybdenum alloy for coating steel, the alloy having high corrosion resistance to corrosive media that may be generated during heat recovery.

[0003] WO 98 / 55661 discloses a kneadable homogeneous austenitic nickel alloy that exhibits high corrosion resistance under both oxidizing and reducing conditions, as well as excellent resistance to localized corrosion in acidic, chlorine-containing media. The alloy comprises (wt%): chromium 20.0-23.0%, molybdenum 18.5-21.0%, iron maximum 1.5%, manganese maximum 0.5%, silicon maximum 0.1%, cobalt maximum 0.3%, tungsten maximum 0.3%, copper maximum 0.3%, aluminum 0.1-0.3%, magnesium 0.001-0.15%, calcium 0.001-0.01%, carbon maximum 0.01%, nitrogen 0.05-0.15%, vanadium 0.1-0.3%, with the balance being nickel and other impurities resulting from melting. This alloy is suitable as a material for components that must withstand chemical corrosion and is also suitable as a welding additive for the superalloying of other nickel-based materials.

[0004] Nickel alloys (such as FM 625, FM 622, and FM 686) are currently used as plating materials in heat recovery applications (such as waste incineration plants, alternative material incineration plants, or biomass plants). Although plating provides multiple layers of protection against corrosion for heat exchanger pipes, heating surfaces, and surfaces in contact with flue gas, overheating occurs in overheated pipes and other components under high heat loads, depending on the materials used and the operating conditions. This forces operators to shut down and perform costly maintenance.

[0005] The purpose of this invention is to provide alloys that have been used for many years according to existing technology to new application areas in the field of coating.

[0006] This objective is achieved by using an alloy having the following composition (in mass %):

[0007] Cr 20.0-23.0%

[0008] Mo 18.5-21.05%

[0009] Fe≤1.5%

[0010] Mn≤0.5%

[0011] Si≤0.1%

[0012] Co ≤ 0.3%

[0013] W≤0.3%

[0014] Cu≤0.5%

[0015] Al≤0.4%

[0016] C≤0.01%

[0017] P≤0.015%

[0018] S≤0.01%

[0019] N 0.03-0.15%

[0020] Optional

[0021] V≤0.3%

[0022] Nb≤0.2%

[0023] Ti≤0.02%

[0024] Balance Ni and impurities caused by melting

[0025] The alloy is used as a coating material in the fields of heat recovery equipment and alternative material incineration equipment.

[0026] Advantageous improvements to the subject matter of this invention can be obtained from the dependent claims.

[0027] In studying the aforementioned material, which has so far been used only in the field of wet corrosion, it has been unexpectedly determined that the material can also be advantageously used in the temperature range of heat recovery.

[0028] The preferred chemical composition (in mass%) is given below:

[0029] Cr >20.0% - <23.0%

[0030] Mo > 18.5% - < 21.0%

[0031] Fe > 0.1% - < 1.0%

[0032] Mn > 0.05% - < 0.4%

[0033] Si > 0.05% - < 0.10%

[0034] Co ≤ 0.2%

[0035] W≤0.25%

[0036] Cu≤0.4%

[0037] Al≤0.3%

[0038] C≤0.05%

[0039] P≤0.015%

[0040] S≤0.005%

[0041] N 0.04-<0.10%

[0042] Optional

[0043] V≤0.25%

[0044] Nb≤0.2%

[0045] Ti≤0.02%

[0046] The balance of Ni and impurities caused by melting.

[0047] The corrosion loads on components and surfaces in contact with flue gas in heat recovery equipment are diverse and complex. Consequently, different types of (diffusion-controlled) high-temperature corrosion emerge, such as corrosion caused by carburization, molten salts, or halogens (especially chlorine). Furthermore, the materials used are also strongly affected by wet corrosion mechanisms during downtime and maintenance.

[0048] This material, already known in its own right, has been found to be exceptionally suitable for use as a coating material in the field of heat recovery equipment. Various studies have confirmed its excellent weldability (high tear resistance and good wetting ability) in welding coating methods. In addition to coating welding, the coating can also be applied, for example, by means of flame or plasma jetting of powder or wire.

[0049] In the test medium "Grüner Tod" solution, the critical pitting temperature, starting from the second coated weld position, is approximately 135°C. Therefore, it is unlikely that enhanced wet corrosion due to pitting will occur during downtime and maintenance.

[0050] Furthermore, it was shown that the pure solder with a working load of at least 600 MPa exhibited a surprisingly high tensile strength RP0.2. It was also determined that the working load resulted in an increase in hardness, as shown in Table 1. In addition to the high chromium and molybdenum content of the alloy and the mixed crystal hardening mechanism, a further increase in hardness under working conditions was also achieved due to the deposition of intermetallic phases.

[0051] These experimental results suggest that this material will exhibit novel characteristic curves under the harsh conditions of heat recovery equipment, namely, not only pure diffusion-controlled / electrochemical corrosion, but also, in particular, a combination of material resistance to mechanical loads, such as mechanical loads (abrasive or erosive corrosion) caused by scattering particles (Streupartikel) and flue gas particles.

[0052] The invention will be explained in detail below with the aid of embodiments:

[0053] Figure 1 A heat exchanger pipe 1 is shown as an example, which can be used in a waste incineration plant (not shown). In this embodiment, pipe 1 should be a water-cooled component made of C steel. A coating of welding material 4 is applied while pipe 1 is rotated, using a welding incinerator 2 (e.g., MSG or WIG) shown only in this illustration.

[0054] Table 1 provides the composition of the coating welding material of the present invention, as well as the composition of the alternative materials used to date.

[0055] Material FM 2120 FM 625 FM 622 Batch number 115544*) 115949 122001 C 0.003 0.015 0.005 S 0.002 0.002 0.004 N 0.068 0.018 0.016 Cr 20.7 22.3 21.4 Ni 59.2 (balance) 64.3 (Balance) 59.2 (balance) Mn 0.13 0.01 0.16 Si 0.04 0.07 0.03 Mo 18.83 9.21 13.7 Fe 0.52 0.20 2.2 Al 0.19 0.06 0.11 B 0.002 <0.001 0.001 V 0.15 <0.01p 0.17 W 0.10 0.02 2.87

[0056] *Impurities caused by melting: Co, Cu, P, Nb, Ti

[0057] Table 1 lists the material data of the materials given in Table 1 in the post-weld state in Table 2.

[0058] FM 2120 FM 625 FM 622 R p 0.2 (MPa) 648 519 512 Rm (MPa) 841 768 746 A5(％) 40 41 46 KV(RT,J) 33, 164 148 Corrosion resistance ISO 3651-2o.K. SEP 1877IIo.K. SEP 1877IIo.K.

[0059] Table 2

[0060]

[0061]

[0062] Table 3: Comparison of HV 0.1 values ​​for solder coating in the initial state (e.g., after soldering) and in the age-hardened state.

[0063] The material FM 2120, which can be used in components for waste incineration equipment, stands out from comparable materials in its higher strength values ​​RP 0.2 and Rm. Calculations using Calphad software later showed that this effect is particularly pronounced through the formation of intermetallic phases (e.g., μ phase). This can also be confirmed through metallographic studies.

[0064] Phase diagram calculations show that an intermetallic μ phase exists for thermodynamic equilibrium in the temperature range below 920°C. Figure 2 The amount of these phases at 650°C is approximately 27% by weight. Figure 3This leads to changes in the mechanical properties and structural configuration of the coated material. The μ phase is formed in the coated material through long-term, sustained thermal influence within a temperature range where this phase exists.

Claims

1. Use of an alloy, by weight percent, comprising the following components, as a coating material in the fields of heat recovery equipment and alternative material incineration equipment: Cr 20.0-23.0％ Mo 18.5-21.05% Fe≤1.5% Mn≤0.5% Si≤0.1% Co ≤ 0.3% W≤0.3％ Cu≤0.5% Al≤0.4％ C≤0.01％ P≤0.015％ S≤0.01％ N 0.02-0.15％ Optional V≤0.3％ Nb≤0.2% Ti≤0.02% The remaining amount of Ni and impurities caused by melting, wherein the coating material has a tensile strength Rp 0.2 of at least 600 MPa under working load after coating and the coating material as a coating welding material has a tensile strength Rm (MPa) of more than 800, and wherein the amount of intermetallic μ phase is about 27% by weight at 650°C and causes changes in the mechanical properties and structural configuration of the coating material.

2. The use according to claim 1, wherein the alloy has the following composition in weight percent: Cr>20.0-<23.0％ Mo > 18.5% - < 21.0% Fe > 0.1% - < 1.0% Mn > 0.05% - < 0.4% Si > 0.001 - < 0.10% Co ≤ 0.2% W≤0.25％ Cu≤0.4% Al≤0.3％ C≤0.05％ P≤0.015％ S≤0.005％ N 0.04-<0.1％ Optional V≤0.25％ Nb≤0.2% Ti≤0.02% The balance of Ni and impurities caused by melting.

3. The use according to claim 1 or 2, wherein the coating material is used in the field of heat exchanger pipes of waste incineration equipment.

4. The use according to any one of claims 1 to 3, wherein the plating material, as a coating welding material, has a tensile strength Rp0.2 (MPa) higher than 640 MPa.

5. The use according to any one of claims 1 to 4, wherein the plating material, as a coating welding material, has a tensile strength Rm (MPa) higher than 840 MPa.

6. The use according to any one of claims 1 to 5, wherein the coating material is used for repair.

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