Oxidized alloys resistant to corrosion accompanied by metallic dust formation

FIELD: materials resistant to corrosion accompanied by metallic dust formation; methods of manufacture of such materials, reactor materials in particular subjected to action of media supersaturated with carbon.

SUBSTANCE: proposed material contains alloy and protective oxide coat on base of alloy. Protective oxide coat consists of at least two oxide layers: first layer which is farthest from surface of alloy is made from manganese oxide. Alloy contains base metals including iron, nickel and cobalt and alloying metals including chromium and manganese; concentration of manganese is at least 10 mass-% and concentration of chromium is at least 25 mass-%. Total content of chromium and manganese is no less than 40 mass-%.

EFFECT: enhanced resistance of material to corrosion with metallic dust formation in media supersaturated with carbon.

2 dwg, 1 tbl, 1 ex

 

The technical field

The invention concerns a method for controlling corrosion of metal dust in the case of reactor materials exposed to environments that are saturated with carbon, and also relates to the composition of the material.

The level of technology

In many processes for the conversion of hydrocarbons, such as, for example, conversion of CH4to synthetic gas, faced with the fact that environments have high activity carbon and relatively low oxygen activity. Materials for high temperature reactors and materials for heat exchangers used in such processes can fail during operation under the action of a very aggressive form of corrosion known as metal dusting.

Metal dusting is a very destructive form of corrosion that affects the alloys based on Fe, Ni and Co at a temperature in the range from 400 to 900°in environments saturated with carbon (active carbon >1), and with relatively low (approximately 10-10up to 10-20ATM) partial pressure of oxygen. This form of corrosion is characterized by a decaying lump of metal with the formation of the metal powder. Despite the fact that many commercially available alloys are designed to form a protective film of Cr2 3or Al2About3in environments with low partial pressure of oxygen, the formation of crystallization centers and the kinetics of growth of these oxides are often not high enough to block the penetration of carbon in the case of environments with active carbon over units.

Described in the literature methods of regulation corrosion with metal dust generation include the application of surface coatings and gaseous inhibitors, especially N2S. the Coating may deteriorate due to diffusion of the constituents of the coating to the substrate alloy. Thus, although the coverage and represent a viable approach to solving the problem in the case of short-term protection, in General, they cannot be recommended for long-term conditions services for a period of 20 years or more. Inhibition of H2S has two drawbacks. First, H2S tends to poisoning of the most catalysts used in the conversion of hydrocarbons. In addition, H2S should be removed from the exit stream that can significantly increase the cost of the process.

Thus, in the art there is a need in the material, resistant to corrosion with metal dust formation in supersaturated with carbon (active carbon >1) environments with low (approximately 10-10up to 10-20atmospheres) p is realnum pressure of oxygen.

Disclosure of inventions

The invention relates to a material resistant to metal dusting, and includes (a) an alloy capable of forming a protective oxide coating on its surface under the influence of environments saturated with carbon, (b) a protective oxide coating, comprising on the surface of the specified alloy of at least two layers, which are formed under the influence of contributing to metal dusting environments with low partial pressure of oxygen. The outer layer, also called the first layer (the layer in contact with supersaturated with carbon environment, or the most remote from the alloy layer), made of a thermodynamically stable oxide, which can quickly cover the surface of the alloy and to block the flow of carbon in the alloy. The first layer is thermodynamically stable oxide of manganese, which is formed faster than the carbon supersaturated environment they can penetrate the surface of the alloy. Therefore, the manganese oxide is attributed to the rapidly forming layer. Under a layer of manganese oxide, the second layer (here he named the second oxide layer) is formed or simultaneously with the formation of this layer of manganese, or after him. The second layer of the protective oxide coating is an oxide film, which is created under a layer of oxide is manganese and is adjacent to a layer of oxide of manganese, and its composition depends on the composition of the alloy from which it is formed. Consequently, the invention relates to a corrosion resistant metal dust material, comprising (a) alloy and (b) a protective oxide coating on the specified alloy, where the specified protective oxide coating includes at least two oxide layer, the first oxide layer is a layer of oxide of manganese, and the specified alloy includes alloying metals and base metals, and these alloying metals include a mixture of chromium and manganese, and these metals include iron, Nickel and cobalt, with the specified manganese is present in the specified alloy at a concentration of at least about 10 wt.% Mn, and the chromium is present in the specified alloy at a concentration of at least about 25 wt.% Cr and the total amount of chromium and manganese is ≥40 wt.%, and said first oxide layer is the most remote from the said surface of the alloy layer.

The protective oxide coating can be formed in situ during use of the alloy in an environment saturated with carbon, or you can cook it, subjecting the alloy, before application of the environment, saturated with carbon. The advantage of this invention is that in the event of cracking of the protective oxide layer when using the implement of the alloy in the environment, saturated with carbon, the protective coating is formed in the fracture will heal oxide layers, shielding, thereby, when using the alloy from the metal dust.

The invention also covers a method of preventing metal dust on metal surfaces exposed to environments that are saturated with carbon; this method involves the creation of the specified metal surface of a material resistant to metal dusting, or the application of a specified metal surface coating of such resistant to metal dusting material comprising a metal alloy comprising alloying metals and base metals, and these alloying metals include a mixture of chromium and manganese, and these metals include iron, Nickel and cobalt, while the manganese is present in the specified alloy at a concentration of at least about 10 wt., % Mn, and the chromium is present in the specified alloy at a concentration of at least about 25 wt.% Cr and the total amount of chromium and manganese is ≥40 wt.%, and said first oxide layer is furthest from the surface of the alloy layer.

Metal surfaces can be created from this alloy, or covered in this alloy, as described above protective hydroxy is Naya film is formed in situ during operation of the plant in the environment, supersaturated with carbon.

Therefore, the invention also covers protective oxide coating that includes at least two oxide layer, where the first layer is a layer of oxide of manganese, and the first layer is the layer at the specified alloy, which is the most remote from the specified alloy layer.

Brief description of drawings

Figure 1 shows performed using scanning electron microscopy image of a two-layer oxide protective film on the alloy, the composition of which 20,1 Fe, 39,4 Ni, 10,0 Mn, 30,5 Cr, after the metal dust at 650°C for 160 hours in an environment of 50 CO-50 N2.

The implementation of the invention

Alloys are formed is described in the application of the protective film include alloys containing a mixture of chromium and manganese. Chromium and manganese in this context referred to as alloying elements. In addition to these alloying elements, alloys contains basic metals. Basic metals form a large part of the alloy and, therefore, are present in amounts of more than about 44% of the total alloy. Thus, in addition to chromium and manganese, alloys can be other metals, called in the context of this application, basic metals, including iron, Nickel, cobalt and mixtures thereof. The alloys can also be additional legious the e elements, such as silicon and aluminum. It is preferable to use Fe-Ni-Mn-Cr alloys.

Basic metals forming alloys in the context of this application, are selected from iron, Nickel and cobalt, or mixtures of these three elements. Base metals may be present in any combination or alloys can be applied only base metal.

The alloys according to this invention can be applied to construct surface facilities that will be exposed to environments conducive to metal dusts, or can existing surface susceptible to metal dusting, to cover such alloys using techniques known in the art. For example, you can apply techniques such as thermal spraying, plasma deposition, chemical deposition from the gas phase and the metallization coating. Therefore, oil installation, you can either design described in this application alloys, or to put on them cover their these alloys, while the protective oxide film is formed or at the time of installation, or prior to use installation.

When used as coatings on existing surfaces, the thickness of such coatings will be in the range from about 10 microns to about 200 microns, site is preferably from about 50 microns to about 100 microns.

Surface, which will benefit from the use of this invention include the surface of any installations or reaction systems that are in operation in contact with environments, supersaturated with carbon, including the surface of the reactors, heat exchangers, pipelines, etc.

Described in this application of the protective coating or film on the surfaces of the alloys are formed on this alloy under the influence of an environment conducive metal dusts, such as a mixture of 50 CO:50 H2. Therefore, the protective coating can be formed during the application of the alloys under the reaction conditions at which the alloys are exposed to environments conducive to metal dusts, or before such application. The preferred range of temperature is from about 350°up to about 1050°C, preferably from about 550°up to about 1050°With a typical exposure time may be in the range from about 1 hour to about 200 hours, preferably from about 1 hour to about 100 hours.

The following examples, which are illustrative and do not limit the invention.

Examples

Electric-arc smelting prepared alloys with different concentrations of Fe, Ni, Mn and Co. Received arc melting alloys are laminated in t is nkiye sheets of a thickness of about 1/16 inch (strength of 0.159 cm). The sheets were annealed overnight at a temperature of 1100°in the inert atmosphere of argon and cooled in the furnace to room temperature. These sheets are then cut out samples of rectangular shape with a size of 0.5 inch×0.25 inch (1.27 cm×0,635 cm). The sample surface was polished or until surface conditions, with the degree of roughness 600, or until the surface condition Linde (alumina powder of 0.05 μm) and washed in acetone. Samples of all metals used in experiments on metal dusting, were analyzed by energy dispersive x-ray spectroscope attached to a scanning electron microscope. The results of chemical analysis are presented in table 1.

39,2
Table 1
The increase of mass due to the deposition of carbon (the unit of measurement of corrosion with metal dust) on finished surfaces Linde In a variety of Fe-Ni-Mn-Cr alloys at 550°and 650°C, gas mixture 50 CO-50 N2after 160 hours of corrosion
The composition of the alloy, wt.%Number (Mn+Cr), wt.%The increase in the mass (mg/cm2) at 550°The increase in the mass (mg/cm2) at 650°
30,4 Fe; 30,4 Ni; 14,7 Mn; 24,5 Cr118,0˜122,090,0˜95,0
20 Fe; 40,5 Ni; 14,9 Mn; 24,6 Cr39,565,0˜67,028,0˜32,0
20,1 Fe; 39,4 Ni; 10,0 Mn; 30,5 Cr40,521,0˜24,0carbon is missing
30,0 Fe; 29,5 Ni; 10,2 Mn; 30,3 Cr40,517,0˜19,0carbon is missing
19,7 Fe; 32,9 Ni; 14,4 Mn; 33,0 Cr47,40,7˜0,9carbon is missing
14,8 Fe; 39,3 Ni; 14,9 Mn; 31,0 Cr45,90,5˜0,9carbon is missing
45,0 Fe; 29,5 Mn; 25,5 Cr55,00,2˜0,5carbon is missing
24,9 Fe; 19,6 Ni; 28,9 Mn; 26,6 Cr55,50,7˜1,2carbon is missing
59,8 Ni; 14,0 Mn; 26,2 Cr40,21,2˜1,7carbon is missing
7 Fe; 77 Ni; 16 Cr (ln 600)*120,0˜130,060,0˜65,0
20 Fe; 45 Ni; 35 Cr (35/45)**230,0˜250,0140,0˜160,0
* - Alloy Inconel 600 (N06600)

** - Alloy, resistant to carburizing, 35/45 (KHR-45A)

The samples were subjected to gaseous sredy CO-50 N 2for 160 hours, which Is a particularly aggressive mixture of gases, in which most high-temperature alloys exposed to metal dust. A few selected for testing commercial alloys were also subjected to the same conditions.

Careful electron microscopy subjected to studies of the alloys showed that certain alloy compositions in the system Fe-Ni-Mn-Cr corrosion resistant metal dust. It was determined that a two-layer protective oxide film, which consists of external MnO layer and the inner MnCr2O4the layer is above reason, resistance to metal dusting. Figure 1 shows performed using scanning electron microscopy image of a two-layer protective film on the alloy composition 20,1 Fe; 39,4 Ni; 10,0 Mn; 30,5 Cr after exposure to saturated carbon environment (50 CO-50 N2)promoting metal dusts, at approximately 650°C for 160 hours. On the surface of the sample is not observed deposition of carbon, which is always accompanied by corrosion of metallic dust. Resistant to carburizing commercial alloy composition indicated in figure 2, has suffered as a result of extensive metal dust. Performed using scanning electron m is croscope image shown in figure 2, demonstrates the dot morphology correlated areas after metal dust at 650°C for 160 hours in an environment of 50 CO-50 N2that is a distinctive feature of metal dust. Figure 2 also shows the deposition of carbon, invariably accompanies such an effect.

In table 1 shows the resistance of the Fe-Ni-Mn-Cr alloys to corrosion with metal dust at a temperature of 550°and 650°C. Since the metal dust is usually accompanied by precipitation of carbon as the unit of measurement of corrosion with metal dust, you can use the increase in mass caused by the deposition of carbon. Determined the increase in mass of various Fe-Ni-Mn-Cr alloys with surface conditions that meet Linde, after corrosion in gas mixture 50 CO-50 N2for 160 hours at 550°and 650°respectively.

1. The material is resistant to corrosion with metal dust, including alloy and a protective oxide coating on the specified alloy, while the protective oxide coating contains at least two oxide layers, the first of which, the most remote from the surface of the alloy made of oxide of manganese and alloy contains basic metals, including iron, Nickel and cobalt, and alloy metals, Inc is committed to chromium and manganese, the concentration of manganese is at least 10 wt.%, the concentration of chromium is at least 25 wt.%, and the total content of chromium and manganese is not less than 40 wt.%.

2. The method of obtaining material, resistant to corrosion with metal dust when exposed to a saturated carbon environments, including the creation of a metallic surface of a metallic alloy containing metals, including iron, Nickel and cobalt, and alloy metals, including chromium and manganese, the concentration of manganese in the alloy is at least 10 wt.%, the concentration of chromium is at least 25 wt.%, while the total content of chromium and manganese is not less than 40 wt.%, and protective oxide coating containing the first oxide layer of the oxide of manganese, which is furthest from the surface of the alloy layer.

3. The method according to claim 2, in which the protective coating contains a second oxide layer.

4. The method according to claim 3, in which the protective oxide coating formed during use of the alloy in the saturated carbon environment conducive to metal dust.



 

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