Aluminized silicon coating material composition, aluminized silicon coating and preparation method of aluminized silicon coating

Abstract

The invention provides an aluminized silicon coating material composition, an aluminized silicon coating and a preparation method of the aluminized silicon coating. The aluminized silicon coating material composition comprises the following components: 10%-50% of an aluminum supply agent, 0.5%-3% of an activating agent, 1%-3% of silicon powder, 1%-4% of a carbon supply agent and the balance of aluminum oxide, wherein the carbon supply agent comprises carbon powder and a compound containing carbon and nitrogen. The preparation method of the aluminized silicon coating comprises the following steps that a workpiece and the aluminized silicon coating material composition are placed in an infiltration box, the infiltration box is sealed, then the infiltration box is heated for element diffusion infiltration chemical heat treatment, and the aluminized silicon coating is obtained. According to the method, the influence of the Kirkendall effect can be reduced, the diffusion rate of Si and Al elements is effectively controlled, and the prepared coating has a compact tissue structure and has high high-temperature thermal stability.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy surface coating, and specifically, to an aluminosilicon coating material composition for pyrolysis furnace tubes, an aluminosilicon coating, and a preparation method thereof. Background Art

[0002] For traditional steam pyrolysis furnace tubes to meet high-temperature conditions, heat-resistant chromium-nickel alloy steel is often selected as the material. However, nickel and iron elements in this alloy will undergo elemental migration under high-temperature action, accumulate on the inner surface of the steam pyrolysis furnace tubes, and serve as catalytic active centers to accelerate coke formation, which greatly limits the operating efficiency of the steam pyrolysis furnace. To address this problem, the general approach is to prepare a single-layer or multi-layer coating on the surface of the alloy substrate based on solid powder pack cementation technology. These coatings can improve the oxidation resistance and thermal corrosion resistance of the alloy material while playing a barrier role to shield iron and nickel elements in the substrate, thereby inhibiting the formation of coke during the reaction.

[0003] Preparing a coating by powder pack cementation is a chemical heat treatment process in which metal atoms penetrate into the surface layer of a workpiece. The workpiece is placed in a cementation agent containing the elements to be infiltrated, heated to a certain temperature and maintained for an appropriate time. The active atoms generated by the thermal decomposition of the cementation agent are adsorbed onto the surface of the workpiece and diffuse into the surface layer of the workpiece, thereby changing the chemical composition, structure, and properties of the surface layer of the workpiece. An aluminosilicon coating on the surface of the workpiece forms a metal layer or compound layer rich in aluminum and silicon on the material surface, which can significantly change the surface characteristics of the workpiece and endow it with good oxidation resistance, corrosion resistance, anti-coking and carbonization resistance, etc. However, since both aluminum and silicon are ferritizing elements and have a high diffusion rate in ferrite, the coatings prepared by either powder pack cementation method, liquid method, or gas method often contain voids, which affect the quality and use of the coatings.

[0004] CN104264205B discloses a composite coating for inhibiting furnace tube coking, a preparation method thereof, and an application. The preparation method of this coating mainly involves preparing a composite coating on the surface of the material by co-electrodeposition composite electroplating method, depositing substances such as chromium, Me, and rare earth oxide Re x O y and so on. The Cr 2 O 3 in the coating obtained by this method can, to a certain extent, inhibit the erosion of the furnace tube by carbon. However, at high temperatures, H 2 O will accelerate the evaporation of chromium oxide, causing the chromium oxide layer to become thinner and reducing the protection effect of the composite coating.

[0005] CN107236925A discloses a solid powder silicon-aluminum co-infiltration process for improving the carburization corrosion resistance of ethylene cracking furnace tubes, and a surface infiltration layer composed of NiAl and FeAl intermetallic compounds is formed on the surface of the ethylene cracking furnace tubes. The silicon-aluminum layer prepared by this process has good anti-carburization ability, but the higher the concentration of silicon element, the faster the diffusion rate, so that during the interdiffusion process of Si and other elements, a serious Kirkendall effect will occur, resulting in the formation of gaps at the front of the silicon infiltration layer.

[0006] CN112853260B discloses a method for preparing a powder embedded infiltration coating, wherein metal powder, alumina, an activator, silicon powder, rare earth and graphite powder balls are uniformly mixed, and placed in an infiltration box with a workpiece for sealing treatment, and then the infiltration box is subjected to element diffusion infiltration chemical heat treatment. Although expandable graphite is added to the infiltration agent in this method, the carbon concentration is reduced with the reaction with oxygen, and a stable nitride cannot be formed, and the reduction in carbon concentration cannot ensure the inhibitory effect of carbon on the diffusion rate of elements such as Si and Al.

[0007] Therefore, developing a new type of aluminum-silicon infiltrated coating material composition and an aluminum-silicon infiltrated coating and a preparation method thereof is still one of the problems to be solved urgently in the field. Summary of the invention

[0008] To solve the above technical problems, the purpose of the present invention is to provide an aluminum-silicon coating material composition and an aluminum-silicon coating and a preparation method thereof. The technical solution of the present invention can effectively control the diffusion rate of Si and Al elements, so that the prepared coating has a dense organizational structure.

[0009] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides an aluminum-silicon infiltrated coating material composition, which includes the following components in mass percentage: 10% to 50% aluminum supply agent, 0.5% to 3% activator, 1% to 3% silicon powder, 1% to 4% carbon supply agent and alumina remainder; wherein the carbon supply agent includes carbon powder and carbon and nitrogen-containing compounds, and the carbon and nitrogen-containing compounds include one or a combination of ammonium carbonate, ammonium bicarbonate and ammonium acetate.

[0010] According to a specific embodiment of the present invention, preferably, the aluminum-silicon infiltrated coating material composition includes the following components, measured in mass percentage: 15% to 35% of an aluminum supply agent, 1% to 3% of an activator, 1% to 3% of silicon powder, 1% to 4% of a carbon supply agent and a remainder of aluminum oxide; wherein the carbon supply agent includes carbon powder and a carbon- and nitrogen-containing compound, and the carbon- and nitrogen-containing compound includes one or a combination of ammonium carbonate, ammonium bicarbonate and ammonium acetate.

[0011] In the above aluminized silicon coating material composition, preferably, the aluminum donor includes pure aluminum powder and / or aluminum-silicon alloy, etc. Among them, the aluminum-silicon alloy has aluminum and silicon as the main components, and also contains a small amount of elements such as copper, iron, nickel, etc. More preferably, in terms of mass percentage, the content of silicon in the aluminum-silicon alloy is 11%, and the content of aluminum is more than 80%.

[0012] In the above aluminized silicon coating material composition, preferably, the activator includes one or a combination of several of aluminum chloride, aluminum fluoride, silicon chloride, etc.

[0013] In the above aluminized silicon coating material composition, preferably, based on the total mass of the carbon donor being 100%, the mass fraction of the carbon powder is 15 - 99%, and the mass fraction of the carbon and nitrogen-containing compound is 1 - 85%; more preferably, based on the total mass of the carbon donor being 100%, the mass fraction of the carbon powder is 28 - 70%, and the mass fraction of the carbon and nitrogen-containing compound is 30 - 72%.

[0014] In the above aluminized silicon coating material composition, preferably, the carbon powder includes graphite and / or activated carbon, etc.

[0015] According to the specific embodiments of the present invention, preferably, the aluminized silicon coating material composition is in powder form, and its particle size is -150 mesh to +400 mesh. It should be noted that, - represents the undersize, + represents the oversize, -150 mesh represents the undersize after screening with a 150-mesh sieve, and +400 mesh represents the oversize after screening with a 400-mesh sieve. That is to say, the particle size of the aluminized silicon coating material composition powder is 37μm to 100μm.

[0016] According to the specific embodiments of the present invention, preferably, the aluminized silicon coating material composition is prepared by the following steps: Mix the aluminum donor, the aluminum oxide, the activator, the silicon powder, and the carbon donor, and then perform ball milling and screening to obtain the aluminized silicon coating material composition. Specifically, the ball milling can be carried out using a ball mill, with corundum balls as the ball milling medium. Put the corundum balls, the aluminum donor, the aluminum oxide, the activator, the silicon powder, and the carbon donor into the ball mill tank, and ball mill at a rotation speed of 150 - 300 r / min for 1 - 2 h. Among them, preferably, the mass ratio of corundum balls to the combination of the aluminum donor, the aluminum oxide, the activator, the silicon powder, and the carbon donor is 1:1 to 3:1. Preferably, the composition obtained after ball milling can be screened through a sieve with a mesh size of -150 mesh to +400 mesh to obtain the aluminized silicon coating material composition.

[0017] The second aspect of the present invention provides a method for preparing an aluminized silicon coating, which uses the above aluminized silicon coating material composition to prepare an aluminized silicon coating. The preparation method includes the following steps:

[0018] Place the workpiece and the aluminized silicon coating material composition in a carburizing box, seal the carburizing box, and then heat the carburizing box for elemental diffusion carbo-thermochemical heat treatment to obtain the aluminized silicon coating.

[0019] In the above preparation method, preferably, the workpiece is a pre-treated workpiece, and the pre-treatment includes grinding and cleaning the workpiece.

[0020] In the above preparation method, preferably, the workpiece includes a cracking furnace tube. Specifically, the workpiece includes an ethylene cracking furnace tube.

[0021] In the above preparation method, preferably, the material of the workpiece includes alloy steel, etc., such as carbon steel or heat-resistant steel, etc. More preferably, by mass percentage, the material of the workpiece includes the following elements: Ni: 0 - 45%, Cr: 0 - 35%, Nb: 0 - 1%, Mo: 0 - 0.2%, C: 0 - 0.8%, Si: 0 - 2%, Mn: 0 - 1.5%, P: 0 - 0.04%, S: 0 - 0.03%, and the balance is Fe, and the content of at least one or more of the elements Ni, Cr, Nb, Mo, and C is not 0. Specifically, the material of the workpiece is a chromium-nickel alloy steel, such as GH series alloys, NS series alloys, or Incoloy series alloys, etc., preferably including Cr20Ni35 alloy, Cr20Ni30 alloy, Cr25Ni35 alloy, Cr35Ni45 alloy, or Cr25Ni20 alloy, etc.

[0022] In the above preparation method, preferably, the carburizing box is sealed in the following manner: Use high-temperature refractory mud to coat the connection between the carburizing box body and the lid to prevent air from entering. Specifically, the high-temperature refractory mud includes components such as hydroxycellulose and kaolin and / or bentonite, and its specific composition can refer to the solutions in the prior art.

[0023] According to the specific embodiments of the present invention, preferably, the preparation method further includes the following steps: After sealing the carburizing box, dry the carburizing box, for example, dry it at 70 - 90 °C for 1 - 3 h.

[0024] In the above preparation method, preferably, the holding temperature for heating the carburizing box for elemental diffusion carbo-thermochemical heat treatment is 700 - 950 °C, the heating rate is 5 - 10 °C / min, and the holding time is 4 - 10 h. Specifically, the process of heating the carburizing box for elemental diffusion carbo-thermochemical heat treatment can be carried out in a conventional heating furnace.

[0025] The third aspect of the present invention provides an aluminized silicon coating, which is prepared by the above preparation method of the aluminized silicon coating.

[0026] According to a specific embodiment of the present invention, preferably, the thickness of the aluminized silicon coating is 85 μm to 110 μm.

[0027] In the prior art, the aluminized silicon coatings prepared by powder pack cementation method, liquid method, and gas method often contain voids, which affect the thermal stability of the coatings. The present invention provides a composition of aluminized silicon coating material, an aluminized silicon coating, and a preparation method thereof. The composition of the aluminized silicon coating material of the present invention includes an aluminum donor, alumina, an activator, silicon powder, and a carbon donor; by placing the workpiece and the aluminized silicon coating material composition in a permeation box, sealing the permeation box, and then heating the permeation box for element diffusion chemical heat treatment, a dense and flat surface coating can be obtained. The present invention can reduce the influence of the Kirkendall effect, effectively control the diffusion rates of Si and Al elements, enable the prepared coating to have a dense tissue structure, and the coating has high high-temperature thermal stability.

[0028] The technical solution of the present invention has at least the following beneficial effects:

[0029] (1) The present invention introduces a carbon donor (including carbon powder and a compound containing carbon and nitrogen) into the permeating agent (i.e., the aluminized silicon coating material composition). The carbon donor decomposes under high temperature to provide active carbon atoms. The introduction of carbon atoms can reduce the diffusion rates of elements such as Si and Al, so that the diffusion rates of elements such as Si and Al match those of matrix elements such as Fe, Ni, and Cr, reduce the influence of the Kirkendall effect, enable the prepared coating to have a dense tissue structure, and the coating has high high-temperature thermal stability, and its high-temperature service life is effectively improved. At the same time, since the diffusion of Si in the coating is more uniform, the spatter of the molten pool during the welding process is avoided, and the welding performance of the coating furnace tube is also improved.

[0030] (2) The carbon donor used in the present invention includes carbon powder and a compound containing carbon and nitrogen. Under high temperature, the compound containing carbon and nitrogen in the carbon donor will decompose to produce carbon dioxide, and then form a reaction equilibrium of carbon monoxide and carbon. The reduction gases such as CO generated can, on the one hand, eliminate the oxygen contained in the permeating agent, eliminate the oxidation effect of oxygen on the permeating agent, and improve the overall utilization efficiency of the permeating agent; on the other hand, the generated reduction gases will form an equilibrium relationship with the carbon component (such as graphite) activated at high temperature, and ensure the inhibitory effect of carbon on the diffusion rates of elements such as Si and Al during the high-temperature co-permeation process by maintaining the carbon concentration in the co-permeation system.

[0031] (3) The nitrogen atoms generated by the decomposition of the compound containing carbon and nitrogen in the carbon donor used in the present invention will combine with aluminum atoms under high temperature and form aluminum nitride on the surface of the workpiece. Since aluminum nitride has high thermal conductivity and thermal shock resistance, and is resistant to corrosion by molten metals, chemicals, and plasmas at high temperature, it can further improve the high-temperature thermal stability of the coating. Brief Description of the Drawings

[0032] Figure 1 It is the surface SEM image of the aluminized silicon coating of Example 1.

[0033] Figure 2 It is the cross-section SEM image of the aluminized silicon coating of Example 1.

[0034] Figure 3 It is the surface SEM image of the aluminized silicon coating of Comparative Example 1.

[0035] Figure 4 It is the surface selected point element distribution map of the aluminized silicon coating of Comparative Example 1.

[0036] Figure 5 It is the surface SEM image of the aluminized silicon coating of Comparative Example 2. Detailed Description of the Invention

[0037] For a clearer understanding of the technical features, objectives, and beneficial effects of the present invention, the technical solutions of the present invention are described in detail below, but it should not be construed as a limitation on the scope of implementation of the present invention.

[0038] Example 1

[0039] This example provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 25% aluminum-silicon alloy, 2% aluminum fluoride, 1% silicon powder, 1% carbon source, and the balance is alumina; wherein, the mass content of silicon in the aluminum-silicon alloy is 11%; the carbon source includes graphite and ammonium bicarbonate. Based on the total mass of the carbon source being 100%, the mass fraction of graphite is 70%, and the mass fraction of ammonium bicarbonate is 30%.

[0040] The aluminized silicon coating material composition is prepared through the following steps: After weighing the aluminum-silicon alloy, aluminum fluoride, silicon powder, carbon source, and alumina according to the ratio, they are stirred and mixed, and then put into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball milling at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1. Then, the composition obtained after ball milling is sieved through 150-mesh and 400-mesh sieves in sequence to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0041] This example also provides an aluminized silicon coating. The material of the workpiece used is Cr25Ni35Nb alloy. The preparation method of the coating includes the following steps:

[0042] (1) The workpiece is polished with 500-mesh silicon carbide sandpaper and ultrasonically cleaned with anhydrous ethanol to obtain the pretreated workpiece;

[0043] (2) Place the pre-treated workpiece and the aluminized silicon coating material composition of this embodiment in an impregnation box, and bury the workpiece in the aluminized silicon coating material composition and compact it. Apply high-temperature refractory mud to the connection between the box body and the lid of the impregnation box to seal the impregnation box and prevent air from entering. Then place the impregnation box in an oven and dry it at 80 °C for 2 h;

[0044] (3) Place the impregnation box in a heat treatment furnace, heat it at a heating rate of 10 °C / min to 750 °C, hold for 5 h, cool it in the furnace after the holding is completed, take it out, and obtain the aluminized silicon coating.

[0045] The thickness of the aluminized silicon coating in this embodiment is 108 μm.

[0046] Example 2

[0047] This embodiment provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 35% aluminum powder, 2% silicon chloride, 2% silicon powder, 1.5% carbon supplier, and the balance is alumina; wherein, the carbon supplier includes graphite and ammonium bicarbonate. Based on the total mass of the carbon supplier being 100%, the mass fraction of graphite is 62%, and the mass fraction of ammonium bicarbonate is 38%.

[0048] The aluminized silicon coating material composition is prepared by the following steps: After weighing aluminum powder, silicon chloride, silicon powder, carbon supplier and alumina according to the ratio, stir and mix them, and then put them into a ball mill for ball milling. Use corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 1.5 h, the ball-to-material ratio is 2:1. Then, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves in sequence to obtain the aluminized silicon coating material composition, which is in powder form and has a particle size of -150 mesh to +400 mesh.

[0049] This embodiment also provides an aluminized silicon coating. The material of the workpiece used is Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0050] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain a pre-treated workpiece;

[0051] (2) Place the pre-treated workpiece and the aluminized silicon coating material composition of this embodiment in an impregnation box, and bury the workpiece in the aluminized silicon coating material composition and compact it. Apply high-temperature refractory mud to the connection between the box body and the lid of the impregnation box to seal the impregnation box and prevent air from entering. Then place the impregnation box in an oven and dry it at 80 °C for 2 h;

[0052] (3) Place the impregnation box in a heat treatment furnace, heat it at a heating rate of 8 °C / min to 750 °C, hold for 5 h, cool it in the furnace after the holding is completed, take it out, and obtain the aluminized silicon coating.

[0053] The thickness of the aluminized silicon coating in this embodiment is 103 μm.

[0054] Example 3

[0055] This embodiment provides a material composition for an aluminized silicon coating. By mass percentage, it includes the following components: 20% aluminum powder, 1.8% silicon chloride, 2% silicon powder, 2% carbon donor, and the balance is alumina; wherein, the carbon donor includes graphite and ammonium acetate. Based on the total mass of the carbon donor being 100%, the mass fraction of graphite is 50%, and the mass fraction of ammonium acetate is 50%.

[0056] The material composition for the aluminized silicon coating is prepared through the following steps: After weighing the aluminum powder, silicon chloride, silicon powder, carbon donor, and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 3:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves successively to obtain the material composition for the aluminized silicon coating, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0057] This embodiment also provides an aluminized silicon coating. The material of the workpiece used is Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0058] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain the pretreated workpiece.

[0059] (2) Place the pretreated workpiece and the material composition for the aluminized silicon coating in this embodiment in an infiltration box, and bury the workpiece in the material composition for the aluminized silicon coating and compact it. Apply high-temperature refractory mud to the connection between the box body and the box cover of the infiltration box to seal the infiltration box and prevent air from entering. Then put the infiltration box into an oven and dry it at 80 °C for 2 h.

[0060] (3) Place the infiltration box in a heat treatment furnace, heat it to 730 °C at a heating rate of 10 °C / min, hold for 6 h, cool it in the furnace after holding, and take it out to obtain the aluminized silicon coating.

[0061] The thickness of the aluminized silicon coating in this embodiment is 95 μm.

[0062] Example 4

[0063] This embodiment provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 15% aluminum-silicon alloy, 1% aluminum chloride, 2% silicon powder, 1.8% carbon donor, and the balance alumina; wherein, the mass content of silicon in the aluminum-silicon alloy is 11%; the carbon donor includes graphite and ammonium acetate, and based on the total mass of the carbon donor being 100%, the mass fraction of graphite is 30% and the mass fraction of ammonium acetate is 70%.

[0064] The aluminized silicon coating material composition is prepared by the following steps: After weighing the aluminum-silicon alloy, aluminum chloride, silicon powder, carbon donor and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 180 r / min for 2 h, with a ball-to-material ratio of 1:1. Then, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves successively to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0065] This embodiment also provides an aluminized silicon coating. The material of the workpiece used is Cr35Ni45Nb alloy, and the preparation method of this coating includes the following steps:

[0066] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain a pretreated workpiece;

[0067] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this embodiment in a permeation box, and bury the workpiece in the aluminized silicon coating material composition and compact it. Apply high-temperature refractory mud to the connection between the permeation box body and the box cover to seal the permeation box and prevent air from entering. Then, put the permeation box into an oven and dry it at 80 °C for 2 h;

[0068] (3) Place the permeation box in a heat treatment furnace, heat it to 800 °C at a heating rate of 10 °C / min and hold for 4 h. After the holding is completed, cool it in the furnace and take it out to obtain the aluminized silicon coating.

[0069] The thickness of the aluminized silicon coating in this embodiment is 98 μm.

[0070] Example 5

[0071] This embodiment provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 26% aluminum powder, 1.3% silicon chloride, 2% silicon powder, 1.8% carbon donor, and the balance alumina; wherein, the carbon donor includes graphite and ammonium acetate, and based on the total mass of the carbon donor being 100%, the mass fraction of graphite is 45% and the mass fraction of ammonium acetate is 55%.

[0072] The aluminized silicon coating material composition is prepared through the following steps: After weighing aluminum powder, silicon chloride, silicon powder, carbon provider and alumina according to the ratio, stir and mix them, and then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 1.5 h, with a ball-to-material ratio of 1.5:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves successively to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0073] This embodiment also provides an aluminized silicon coating. The workpiece used is made of Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0074] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain the pretreated workpiece;

[0075] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this embodiment in an infiltration box, and bury the workpiece in the aluminized silicon coating material composition and compact it. Apply high-temperature refractory mud to the connection between the infiltration box body and the lid to seal the infiltration box and prevent air from entering. Then put the infiltration box into an oven and dry it at 80 °C for 2 h;

[0076] (3) Place the infiltration box in a heat treatment furnace, heat it to 850 °C at a heating rate of 10 °C / min, hold for 6 h, cool it in the furnace after the holding ends, and take it out to obtain the aluminized silicon coating.

[0077] The thickness of the aluminized silicon coating in this embodiment is 100 μm.

[0078] Example 6

[0079] This embodiment provides an aluminized silicon coating material composition. By mass percentage, it includes the following components: 30% aluminum powder, 3% aluminum fluoride, 1% silicon powder, 2.5% carbon provider, and the balance alumina; wherein, the carbon provider includes graphite and ammonium acetate. Based on the total mass of the carbon provider being 100%, the mass fraction of graphite is 37% and the mass fraction of ammonium acetate is 63%.

[0080] The aluminized silicon coating material composition is prepared through the following steps: After weighing aluminum powder, aluminum fluoride, silicon powder, carbon provider and alumina according to the ratio, stir and mix them, and then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 200 r / min for 1.5 h, with a ball-to-material ratio of 2:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves successively to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0081] This embodiment provides an aluminized silicon coating. The workpiece used is made of Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0082] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain a pretreated workpiece;

[0083] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this embodiment in a permeation box, bury the workpiece in the aluminized silicon coating material composition and compact it, smear high-temperature refractory mud at the connection between the permeation box body and the lid to seal the permeation box and prevent air from entering, and then place the permeation box in an oven and dry it at 80 °C for 2 h;

[0084] (3) Place the permeation box in a heat treatment furnace, heat it to 830 °C at a heating rate of 5 °C / min, hold for 7 h, cool it in the furnace after the holding is completed, take it out, and obtain the aluminized silicon coating.

[0085] The thickness of the aluminized silicon coating in this embodiment is 93 μm.

[0086] Example 7

[0087] This embodiment provides an aluminized silicon coating material composition. In terms of mass percentage, it includes the following components: 10% aluminum-silicon alloy, 0.5% silicon chloride, 1% silicon powder, 3% carbon provider, and the balance is alumina; wherein, the mass content of silicon in the aluminum-silicon alloy is 11%; the carbon provider includes graphite and ammonium carbonate. Based on the total mass of the carbon provider being 100%, the mass fraction of graphite is 32%, and the mass fraction of ammonium carbonate is 68%.

[0088] The aluminized silicon coating material composition is prepared through the following steps: Weigh the aluminum-silicon alloy, silicon chloride, silicon powder, carbon provider and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 280 r / min for 1.5 h, and the ball-to-material ratio is 3:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves in sequence to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0089] This embodiment provides an aluminized silicon coating. The workpiece used is made of Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0090] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain a pretreated workpiece;

[0091] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this embodiment in an infiltration box, bury the workpiece in the aluminized silicon coating material composition and compact it, apply high-temperature refractory mud to the connection between the box body and the lid of the infiltration box to seal the infiltration box and prevent air from entering, and then put the infiltration box into an oven and dry it at 80 °C for 2 h;

[0092] (3) Place the infiltration box in a heat treatment furnace, heat it to 950 °C at a heating rate of 8 °C / min and hold for 6 h, cool it in the furnace after the holding is completed, take it out, and obtain the aluminized silicon coating.

[0093] The thickness of the aluminized silicon coating in this embodiment is 88 μm.

[0094] Example 8

[0095] This embodiment provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 50% aluminum-silicon alloy, 2% aluminum fluoride, 2% silicon powder, 3.5% carbon provider, and the balance is alumina; wherein, the mass content of silicon in the aluminum-silicon alloy is 11%; the carbon provider includes activated carbon and ammonium carbonate, and taking the total mass of the carbon provider as 100%, the mass fraction of activated carbon is 15%, and the mass fraction of ammonium carbonate is 85%.

[0096] The aluminized silicon coating material composition is prepared by the following steps: Weigh the aluminum-silicon alloy, aluminum fluoride, silicon powder, carbon provider and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling, use corundum balls as the ball milling medium, ball mill at a speed of 180 r / min for 1.5 h, the ball-to-material ratio is 2.5:1, and then sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves in sequence to obtain the aluminized silicon coating material composition, which is in powder form and the particle size is -150 mesh to +400 mesh.

[0097] This embodiment provides an aluminized silicon coating. The material of the workpiece used is Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0098] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a Scotch-Brite pad and acetone to obtain a pretreated workpiece;

[0099] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this embodiment in an infiltration box, bury the workpiece in the aluminized silicon coating material composition and compact it, apply high-temperature refractory mud to the connection between the box body and the lid of the infiltration box to seal the infiltration box and prevent air from entering, and then put the infiltration box into an oven and dry it at 80 °C for 2 h;

[0100] (3) Place the permeation box in a heat treatment furnace, heat it to 860 °C at a heating rate of 7 °C / min, hold for 7 h, then cool it in the furnace, take it out, and obtain the aluminized silicon coating described above.

[0101] The thickness of the aluminized silicon coating in this example is 89 μm.

[0102] Example 9

[0103] This example provides a material composition for an aluminized silicon coating. By mass percentage, it includes the following components: 28% aluminum powder, 2.7% silicon chloride, 3% silicon powder, 4% carbon donor, and the balance is alumina; among them, the carbon donor includes graphite and ammonium acetate. Based on the total mass of the carbon donor being 100%, the mass fraction of graphite is 99%, and the mass fraction of ammonium acetate is 1%.

[0104] The material composition for the aluminized silicon coating is prepared by the following steps: After weighing the aluminum powder, silicon chloride, silicon powder, carbon donor, and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1. Then, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves in sequence to obtain the material composition for the aluminized silicon coating, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0105] This example provides an aluminized silicon coating. The material of the workpiece used is Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0106] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain the pretreated workpiece.

[0107] (2) Place the pretreated workpiece and the material composition for the aluminized silicon coating in this example in a permeation box, and bury the workpiece in the material composition for the aluminized silicon coating and compact it. Apply high-temperature refractory mud to the connection between the permeation box body and the lid to seal the permeation box and prevent air from entering. Then, place the permeation box in an oven and dry it at 80 °C for 2 h.

[0108] (3) Place the permeation box in a heat treatment furnace, heat it to 950 °C at a heating rate of 10 °C / min, hold for 8 h, then cool it in the furnace, take it out, and obtain the aluminized silicon coating described above.

[0109] The thickness of the aluminized silicon coating in this example is 85 μm.

[0110] Example 10

[0111] This embodiment provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 33% aluminum powder, 3% aluminum fluoride, 1% silicon powder, 2.8% carbon donor, and the balance is alumina; wherein, the carbon donor includes graphite and ammonium carbonate. Based on the total mass of the carbon donor being 100%, the mass fraction of graphite is 28% and the mass fraction of ammonium carbonate is 72%.

[0112] The aluminized silicon coating material composition is prepared through the following steps: After weighing aluminum powder, aluminum fluoride, silicon powder, carbon donor and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 1.8 h, with a ball-to-material ratio of 1:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves in sequence to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0113] This embodiment provides an aluminized silicon coating. The workpiece used is made of Cr35Ni45Nb alloy. The preparation method of this coating includes the following steps:

[0114] (1) Grind the workpiece with 200-mesh pneumatic sandpaper and clean it with a scouring pad and acetone to obtain the pretreated workpiece;

[0115] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this embodiment in an infiltration box, and bury the workpiece in the aluminized silicon coating material composition and compact it. Apply high-temperature refractory mud to the connection between the infiltration box body and the box cover to seal the infiltration box to prevent air from entering. Then put the infiltration box into an oven and dry it at 80°C for 2 h;

[0116] (3) Place the infiltration box in a heat treatment furnace, heat it to 700°C at a heating rate of 8°C / min and hold for 10 h. After the holding is completed, cool it with the furnace and take it out to obtain the aluminized silicon coating.

[0117] The thickness of the aluminized silicon coating in this embodiment is 90 μm.

[0118] Comparative Example 1

[0119] This comparative example provides an aluminized silicon coating material composition, which includes the following components by mass percentage: 25% aluminum-silicon alloy, 2% ammonium chloride, 1% silicon powder, and the balance is alumina; wherein, the mass content of silicon in the aluminum-silicon alloy is 11%.

[0120] The aluminized silicon coating material composition is prepared by the following steps: Weigh aluminum-silicon alloy, ammonium chloride, silicon powder and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves successively to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0121] This comparative example also provides an aluminized silicon coating. The workpiece used is made of Cr35Ni35Nb alloy. The preparation method of this coating includes the following steps:

[0122] (1) Grind the workpiece with 500-mesh silicon carbide sandpaper and ultrasonically clean it with absolute ethanol to obtain the pretreated workpiece;

[0123] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this comparative example in a permeation box, and bury the workpiece in the aluminized silicon coating material composition and compact it. Apply high-temperature refractory mud to the connection between the permeation box body and the box cover to seal the permeation box and prevent air from entering. Then put the permeation box into an oven and dry it at 80 °C for 2 h;

[0124] (3) Place the permeation box in a heat treatment furnace, heat it to 750 °C at a heating rate of 10 °C / min, hold for 5 h, cool it in the furnace after the holding is completed, and take it out to obtain the aluminized silicon coating.

[0125] The thickness of the aluminized silicon coating in this comparative example is 54 μm.

[0126] Comparative Example 2

[0127] This comparative example provides an aluminized silicon coating material composition. By mass percentage, it includes the following components: 25% aluminum-silicon alloy, 2% aluminum fluoride, 1% silicon powder, 1% graphite, and the balance is alumina; wherein, the mass content of silicon in the aluminum-silicon alloy is 11%.

[0128] The aluminized silicon coating material composition is prepared by the following steps: Weigh aluminum-silicon alloy, aluminum fluoride, silicon powder, graphite and alumina according to the ratio, stir and mix them, then put them into a ball mill for ball milling. Using corundum balls as the ball milling medium, ball mill at a speed of 300 r / min for 2 h, with a ball-to-material ratio of 2:1. After that, sieve the composition obtained after ball milling through 150-mesh and 400-mesh sieves successively to obtain the aluminized silicon coating material composition, which is in powder form with a particle size of -150 mesh to +400 mesh.

[0129] This comparative example also provides an aluminized silicon coating. The workpiece used is made of Cr25Ni35Nb alloy. The preparation method of this coating includes the following steps:

[0130] (1) Grind the workpiece with 500 - mesh silicon carbide sandpaper and ultrasonically clean it with absolute ethanol to obtain the pretreated workpiece;

[0131] (2) Place the pretreated workpiece and the aluminized silicon coating material composition of this comparative example in an infiltration box, bury the workpiece in the aluminized silicon coating material composition and compact it, smear high - temperature refractory mud at the connection between the box body and the lid of the infiltration box to seal the infiltration box and prevent air from entering, and then put the infiltration box into an oven and dry it at 80 °C for 2 h;

[0132] (3) Place the infiltration box in a heat treatment furnace, heat it to 750 °C at a heating rate of 10 °C / min, hold for 5 h, cool it in the furnace after the holding is completed, take it out to obtain the aluminized silicon coating.

[0133] The thickness of the aluminized silicon coating of this comparative example is 58 μm.

[0134] Test Example

[0135] Perform SEM detection on the aluminized silicon coatings of Example 1, 3, 9 and Comparative Examples 1 - 2, and conduct surface point - selected element analysis. The obtained results are as Figures 1 to 5 and Table 1 shows.

[0136] Table 1 Statistical table of surface element mass percentage contents of the coatings of Comparative Example 2 and Examples 1, 3, 9

[0137] Element type Comparative Example 2 (%) Example 1 (%) Example 3 (%) Example 9 (%) CK 7.49 10.33 9.43 8.92 AlK 23.85 25 24.73 24.01 SiK 1.45 3.37 2.98 2.38

[0138] Figure 1 is the surface SEM image of the aluminized silicon coating of Example 1. Figure 2 is the cross - section SEM image of the aluminized silicon coating of Example 1. It can be seen from Figure 1 and Figure 2 that the surface of the aluminized silicon coating prepared in Example 1 of the present invention is dense and flat, and the coating has a dense organizational structure. Figure 3 is the surface SEM image of the aluminized silicon coating of Comparative Example 1, and it can be seen that the coating contains obvious holes; Figure 4 is the surface point - selected element distribution map of the aluminized silicon coating of Comparative Example 1, where Figure 4 (a) of Figure 3 is the element distribution map at the "1" position in Figure 4 (b) of Figure 3 is the element distribution map at the "2" position in Figure 4 (c) of Figure 3 is the element distribution map at the "3" position in . It can be seen that the surface element distribution of the coating is uneven, and the Si content at the hole position is significantly higher. Thus, it can be seen that Comparative Example 1 uses a conventional aluminized silicon process, and there are obvious defects in the coating. Although the surface layer is mainly aluminum element, the Si aggregation is obvious inside.Figure 5 SEM image of the surface of the aluminized silicon coating of Comparative Example 2. From Figure 5 the comparison with Figure 1 it can be seen that the surface of the coating in Example 1 of the present invention is smoother than that of Comparative Example 2.

[0139] Table 1 is a statistical table of the surface element mass percentage content of the coatings of Comparative Example 2 and Examples 1, 3, and 9. By comparing Comparative Example 2 with Example 1 of the present invention, it can be seen that the Al and Si elements contained in the carburizer used in the present invention are higher than those in the coating prepared by using only graphite as the carburizer, indicating that the carburizer used in the present invention can generate reducing gas and form an equilibrium relationship with the graphite component after high-temperature activation. The stable carbon concentration in the co-permeation system can ensure the inhibitory effect of carbon element on the diffusion of elements such as Si and Al into the workpiece during the high-temperature co-permeation process. Compared with using only graphite as the carburizer, the inhibitory effect of the carburizer used in the present invention on the diffusion of Al and Si elements is more obvious.

[0140] The aluminized silicon coatings of Examples 1 to 10 and Comparative Examples 1 to 2 were tested for coking inhibition performance.

[0141] The coking inhibition performance of the coating was tested using a coupon evaluation device. This device suspends the coating coupon in a tubular reactor and simulates the steam cracking reaction conditions under high temperature by introducing steam and hydrocarbon raw material gas into the reaction tube. The same evaluation conditions were used for each example and comparative example of the present invention. The specific evaluation conditions were as follows: Naphtha was used as the cracking raw material to test the coking inhibition performance of the coating coupon. The reaction conditions were that the mass ratio of naphtha to deionized water was 2:1, the naphtha flow rate was 8 mL / min, the deionized water flow rate was 3 mL / min. After mixing the two, they were preheated to 360 °C and then introduced into the reaction tube for cracking reaction. The reaction temperature of the cracking furnace was maintained at 840 °C, the reaction pressure was 30 kPa, and the cracking reaction time was 5 h. After the reaction, the coating coupon was taken out, and the total mass Wtotal of the coked coating coupon was weighed using an electronic balance. After deducting the mass W0 of the coupon before the evaluation test through Equation (1), the coking amount Wcoke of the coating coupon was obtained.

[0142] Wcoke = Wtotal - W0 (1)

[0143] In order to better express the inhibitory effect of the coating on coke, the present invention uses the coking inhibition rate to describe the coking inhibition performance of the coating. The calculation formula of the coking inhibition rate is shown in Equation (2):

[0144] S = (Wreference - Wcoke) / Wreference × 100% (2)

[0145] Among them, S is the coking inhibition rate, Wcoke is the coking amount of the coating coupon, and Wreference is the coking amount of the reference coupon (i.e., the coupon without coating).

[0146] The preparation method of the reference coupon used in this test is as follows: Take a Cr35Ni45Nb alloy substrate, process it into a sample piece with a size of 30mm×15mm×5mm, polish it with 200-mesh pneumatic sandpaper, clean it with a scouring pad and acetone, and then dry it to obtain the reference coupon.

[0147] It should be noted that the size of the coated coupon in this test is also 30mm×15mm×5mm.

[0148] The coking inhibition performance evaluation experiments were carried out on the coatings prepared in Comparative Examples 1-2 and Examples 1-10, and the coking inhibition rates of each coating are shown in Table 2.

[0149] Table 2 Summary table of coking amount and coking inhibition rate of coatings

[0150]

[0151]

[0152] It can be seen from the data in Table 2 that the aluminized silicon coating prepared by the present invention has better coking inhibition effect and high-temperature thermal stability performance. Taking Example 1 as an example, the coking amount of Example 1 is significantly reduced compared with that of the blank coupon (i.e., the reference coupon) and the coupons of Comparative Examples 1 and 2. The coking inhibition rate of Example 1 is the highest, reaching 90.50%. It is increased by 35.72% and 27.52% respectively compared with Comparative Examples 1 and 2.

[0153] Therefore, the present invention reduces the influence of the Kirkendall effect, effectively inhibits the diffusion rates of Si and Al elements, the diffusion of elements such as Si and Al is more uniform, realizes the matching of the diffusion speeds of each element, makes the prepared coating smooth and defect-free, the coating has a dense organizational structure, and the coating has high high-temperature thermal stability performance.

[0154] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. It is impossible to list all the implementation manners here. Any obvious changes or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An aluminized silicon coating material composition, by mass percentage, it comprises the following components: aluminum donor 10% - 50%, activator 0.5% - 3%, silicon powder 1% - 3%, carbon donor 1% - 4%, and the balance is alumina; wherein, the carbon donor includes carbon powder and carbon- and nitrogen-containing compounds, and the carbon- and nitrogen-containing compounds include one or a combination of several of ammonium carbonate, ammonium bicarbonate, and ammonium acetate.

2. The aluminized silicon coating material composition according to claim 1, wherein, the aluminum donor includes pure aluminum powder and / or aluminum-silicon alloy.

3. The aluminized silicon coating material composition according to claim 1, wherein, the activator includes one or a combination of several of aluminum chloride, aluminum fluoride, and silicon chloride.

4. The aluminized silicon coating material composition according to claim 1, wherein, taking the total mass of the carbon donor as 100%, the mass fraction of the carbon powder is 15 - 99%, and the mass fraction of the carbon- and nitrogen-containing compounds is 1 - 85%; preferably, taking the total mass of the carbon donor as 100%, the mass fraction of the carbon powder is 28 - 70%, and the mass fraction of the carbon- and nitrogen-containing compounds is 30 - 72%.

5. The aluminized silicon coating material composition according to claim 1, wherein, the carbon powder includes graphite and / or activated carbon.

6. The aluminized silicon coating material composition according to claim 1, wherein, the aluminized silicon coating material composition is in powder form, and its particle size is -150 mesh to +400 mesh.

7. The aluminized silicon coating material composition according to any one of claims 1 - 6, wherein, the aluminized silicon coating material composition is prepared by the following steps: mixing the aluminum donor, the alumina, the activator, the silicon powder, and the carbon donor, followed by ball milling and screening to obtain the aluminized silicon coating material composition.

8. A method for preparing an aluminized silicon coating, which uses the aluminized silicon coating material composition according to any one of claims 1 - 7 to prepare an aluminized silicon coating, and the preparation method comprises the following steps: Placing the workpiece and the aluminized silicon coating material composition in a permeation box, sealing the permeation box, and then heating the permeation box for element diffusion chemical heat treatment to obtain the aluminized silicon coating.

9. The preparation method according to claim 8, wherein, the workpiece includes a cracking furnace tube; Preferably, the material of the workpiece includes alloy steel.

10. The preparation method according to claim 8, wherein, When heating the permeation box for element diffusion chemical heat treatment, the holding temperature is 700 - 950 °C, the heating rate is 5 - 10 °C / min, and the holding time is 4 - 10 h.

11. An aluminized silicon coating, which is prepared by the preparation method of the aluminized silicon coating according to any one of claims 8 - 10; Preferably, the thickness of the aluminized silicon coating is 85 μm - 110 μm.

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