High-temperature-resistant composite coating and preparation method thereof

Abstract

The invention discloses a high-temperature-resistant composite coating and a preparation method thereof.According to the high-temperature-resistant composite coating, a first high-temperature-resistant coating is prepared on the surface of a base material through a plasma spraying method, and the first high-temperature-resistant coating is a composite coating composed of Al / Al2O3 with excellent high-temperature resistance; on the basis, a high-entropy alloy is introduced to serve as a second high-temperature-resistant coating, the high-temperature-resistant coating takes an aluminum element as a core element and can form good metallurgical bonding with the first high-temperature-resistant coating, and the second high-temperature-resistant coating is prepared through a laser cladding method, so that the bonding property with the first high-temperature-resistant coating is further enhanced. The high-entropy high-temperature alloy is used as the outermost coating, the porosity is low, the components are uniform, and certain mechanical properties are achieved while high temperature resistance is achieved. According to the composite coating disclosed by the invention, special powder components and a preparation process are adopted, so that the coating is difficult to deform or peel off in a long-time high-temperature environment, a base material is effectively protected, and the service life of the base material is prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of high temperature resistant coatings, and in particular relates to a high temperature resistant composite coating and a preparation method thereof. Background Art

[0002] In thermal power units, the boiler's water-cooled wall, superheater, reheater, economizer tubes and their hanging parts are in direct contact with the boiler's high-temperature steam (steam temperature is above 600°C), which causes the high-temperature steam to have a greater impact on the boiler tube wall, leading to thermal fatigue and corrosion of the tube wall. These problems will not only reduce the efficiency of the boiler, but may also lead to serious safety accidents.

[0003] In order to address the high-temperature corrosion of the boiler tube wall caused by the high-temperature steam of the boiler, high-temperature and corrosion-resistant materials are usually selected, such as stainless steel and alloy steel. At the same time, the boiler production parameters can be optimized, such as reasonably controlling the temperature of the steam flowing into the boiler tube wall.

[0004] In order to improve the high-temperature corrosion of boiler tube walls, grain refinement and inner wall shot peening technology can be adopted. These two technologies change the inner wall structure of the tube, so that the alloy can quickly grow the Cr2O3 film required for anti-oxidation; or use Al2O3 film, but the stability of these two types of films in steam above 600℃ is crossed, and the loose oxide film caused by volatile products will cause the oxide film to peel off, and further lead to tube blockage and tube explosion accidents. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a high-temperature resistant composite coating and a preparation method thereof to solve the problems in the prior art that the boiler tube wall is easily exposed to a high-temperature steam environment for a long time, is easily corroded by high-temperature steam, and the existing coating is easy to fall off.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a high temperature resistant composite coating comprises the following steps:

[0008] Step 1, pre-treating the substrate;

[0009] Step 2, Al powder, Si powder, Al2O3 powder and NH4Br powder are mixed, and a first solid phase powder is obtained after ball milling, and the first solid phase powder is sprayed on the surface of the substrate by plasma spraying to obtain a first high temperature resistant coating;

[0010] Step 3, mix Al powder, Co powder, Cr powder, Ni powder, and Fe powder, obtain a second solid phase powder after ball milling, and obtain a second high temperature resistant coating by laser cladding the second solid phase powder on the first high temperature resistant coating; the molar fraction of Al powder in the second solid phase powder is 25% to 30%, and the other four powders are equal.

[0011] A further improvement of the present invention is:

[0012] Preferably, in step 1, the substrate pretreatment is to wash the substrate surface with anhydrous ethanol and deionized water in sequence for several times;

[0013] In step 2, the substrate is preheated before plasma spraying.

[0014] Preferably, in step 2, the ball milling speed is 350-450 r / min, and the ball milling time is 6-24 h.

[0015] Preferably, in step 2, the first solid phase powder is composed of 60-80% Al powder, 5-30% Si powder, 2-10% Al2O3 powder and 1-5% NH4Br powder, by mass fraction.

[0016] Preferably, in step 3, before placing the second solid phase powder on the first high temperature resistant coating, the surface of the first high temperature resistant coating is cleaned with dilute hydrochloric acid.

[0017] Preferably, in step 3, the ball milling speed during the ball milling of Al powder, Co powder, Cr powder, Ni powder and Fe powder is 200-300 r / min, and the ball milling time is 8-20 h.

[0018] Preferably, the second solid phase powder is dried after being mixed, the drying temperature is 100-120° C., and the drying time is 1-2 h.

[0019] Preferably, in step 3, the laser cladding power is 2000-3000W, the scanning speed is 8-12mm / s, the powder feeding speed is 5-10g / min, the spot diameter is 3-5mm, the powder feeding gas and the shielding gas are high-purity argon, and the cladding overlap rate is 40-50%;

[0020] Preferably, the substrate is any one of TP304H, TP347H, Super304H, TP347HFG or HR3C.

[0021] A high temperature resistant composite coating prepared by any one of the above preparation methods, comprising a first high temperature resistant coating composited on a substrate and a second high temperature resistant coating composited on the first high temperature resistant coating;

[0022] The first high temperature resistant coating is composed of Al, Si, Al2O3 and NH4Br, and the second high temperature resistant coating is composed of Al, Co, Cr, Ni and Fe.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention discloses a method for preparing a high temperature resistant composite coating. The high temperature resistant composite coating first prepares a first layer of high temperature resistant coating on the surface of a substrate. The coating uses aluminum with excellent high temperature resistance as a core element. When sprayed by spraying technology, an Al2O3 layer with excellent high temperature resistance can be formed. Silicon is added to the first layer of high temperature resistant coating to generate a SiO2 protective film under a high temperature environment, thereby improving the oxidation resistance and corrosion resistance of the coating. At the same time, the silicon element can also promote the interaction between the coating and the substrate. On this basis, the invention also introduces a second high temperature resistant coating. The second high temperature resistant coating is based on the first high temperature resistant coating, and a high entropy alloy is introduced as the second layer of high temperature resistant coating. The high temperature resistant coating uses aluminum as a core element, and can have good metallurgical bonding with the first high temperature resistant coating. At the same time, because it is prepared by laser cladding, it can further strengthen the bonding with the first high temperature resistant coating at high temperature. The high entropy high temperature alloy is the outermost coating, and has low porosity and uniform composition. It has certain mechanical properties while being resistant to high temperatures. The composite coating of the present invention uses a special powder component and preparation process, so that the coating is difficult to deform or peel off in a long-term high-temperature environment, thereby effectively protecting the substrate and improving the service life of the substrate. In addition, since the coating is composed of multiple metals, the coating has excellent oxidation resistance and corrosion resistance, further improving the high-temperature resistance of the coating. The high-temperature resistant composite coating of the present invention, due to its special double-layer structure, makes the coating not only have excellent high-temperature resistance, but also have excellent thermal insulation performance, thereby improving the service life of the substrate.

[0025] Furthermore, before the first high temperature resistant coating is compounded, the substrate is cleaned to remove impurities on the surface of the substrate and the substrate is preheated, which can enhance the bonding strength between the first high temperature resistant coating and the substrate.

[0026] Furthermore, before laser cladding the second solid phase powder on the first high temperature resistant coating, the surface of the high temperature coating is cleaned with dilute hydrochloric acid, which can slightly etch the surface of the first high temperature resistant coating, increase the roughness of the surface of the first high temperature resistant coating, and enhance the bonding between the second solid phase powder and the first high temperature resistant coating.

[0027] Furthermore, the second solid phase powder is dried before being clad on the first high temperature resistant coating to avoid a certain amount of moisture in the second solid phase powder, which may affect the laser cladding process.

[0028] Furthermore, the second high temperature resistant coating is prepared by a laser cladding method, and the bonding strength between the second high temperature resistant coating and the first high temperature resistant coating is significantly improved, thereby improving the overall performance of the coating.

[0029] The second aspect of the present invention discloses a high temperature resistant composite coating, which comprises a first high temperature resistant coating composited on a substrate and a second high temperature resistant coating composited on the first high temperature resistant coating; the first high temperature resistant coating is composed of Al, Si, Al2O3 and NH4Br, and the second high temperature resistant coating is composed of Al, Co, Cr, Ni and Fe. Due to its special double-layer structure, the coating not only has excellent high temperature resistance, but also has excellent thermal insulation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of the composite coating structure prepared by the present invention. DETAILED DESCRIPTION

[0031] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0032] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0033] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0034] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0035] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0036] As mentioned in the background technology, the boiler tube wall in the prior art is easily corroded due to the influence of high temperature. In order to solve this problem, in addition to the requirements on the material of the tube wall, the prior art also coats the surface with a coating, but the prepared coating is easy to fall off, in order to solve the above problem.

[0037] The first aspect of the present invention discloses a method for preparing a high temperature resistant composite coating, comprising the following steps:

[0038] Step 1, pre-treating the substrate;

[0039] The substrate heat treatment comprises cleaning the substrate surface with anhydrous ethanol and deionized water alternately for several times; and preheating the substrate before performing step 2.

[0040] Among them, the preheating temperature is 220℃ and the preheating time is 30-60min.

[0041] The substrate is targeted at common boiler tube wall materials, such as TP304H, TP347H, Super304H, TP347HFG, HR3C or nickel-iron based alloys.

[0042] Step 2, preparing a first high temperature resistant coating;

[0043] Al powder, Si powder, Al2O3 powder and NH4Br powder are mixed, and a first solid phase powder is obtained after ball milling. The first solid phase powder is sprayed on the surface of the substrate to obtain a first high temperature resistant coating; in step 2, the ball milling speed is 350-450r / min, and the ball milling time is 6-24h.

[0044] In terms of mass fraction, the first solid phase powder is composed of 60-80% Al powder, 5-30% Si powder, 2-10% Al2O3 powder and 1-5% NH4Br powder. Among the components, Al powder is the main material for high temperature resistance. During the service process of the coating, a dense Al2O3 oxide film can be formed to protect the metal substrate from the erosion of high temperature steam. By adding an appropriate amount of Al2O3 powder to the solid phase powder, it can be directly melted into the infiltration layer during the plasma spraying process to form an α-Al2O3 phase, accelerating the transformation of the θ-Al2O3 oxide film formed during the service process to α-Al2O3, thereby further improving the high temperature resistance of the first high temperature resistant coating.

[0045] The spraying voltage is 550-650V, and the spraying current is 60-110A. The powder feeding gas and protective gas are high-purity argon, hydrogen and nitrogen, and the gas flow rates are 35-60, 10-24 and 10-25L / min respectively, and the powder feeding amount is 20-40dm 3 / h, the spraying distance is 80 ~ 120mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to achieve better adhesion between the coating and the substrate.

[0046] As a preferred solution, high-temperature sintering is performed after spraying, the high-temperature sintering temperature is 980-1150° C., the high-temperature sintering time is 8-15 minutes, and inert gas protection is used during the sintering process.

[0047] After sintering, the residue is treated by high-pressure water gun or high-pressure air flow and then naturally dried.

[0048] Step 3, mix Al powder, Co powder, Cr powder, Ni powder, and Fe powder, obtain a second solid phase powder after ball milling, and obtain a second high temperature resistant coating by laser cladding the second solid phase powder on the first high temperature resistant coating; the molar fraction of Al powder in the second solid phase powder is 25% to 30%, and the other four powders are equal.

[0049] In this process, before placing the second solid phase powder on the first high temperature resistant coating, the surface of the first high temperature resistant coating is cleaned with dilute hydrochloric acid to etch the surface of the first high temperature resistant coating, thereby increasing the roughness of the surface of the first high temperature resistant coating and improving the metallurgical bonding performance between the second high temperature resistant coating and the first high temperature resistant coating.

[0050] Al powder, Co powder, Cr powder, Ni powder and Fe powder are mixed by a planetary ball mill. The ball milling speed during the ball milling process is 200-300 r / min and the ball milling time is 8-20 hours.

[0051] The second solid phase powder after ball milling is dried in a drying oven at a drying temperature of 100-120° C. for 1-2 hours in a vacuum environment or a protective gas environment.

[0052] The second solid phase powder is laid on the first layer of high temperature resistant coating, and then laser cladding is performed. The laser cladding power is 2000-3000W, the scanning speed is 8-12mm / s, the powder feeding speed is 5-10g / min, the spot diameter is 3-5mm, the powder feeding gas and the protective gas are high-purity argon, and the cladding overlap rate is 40-50%.

[0053] The second aspect of the present invention discloses a high-temperature resistant composite coating prepared by the above-mentioned preparation method, which coating includes a first high-temperature resistant coating composited on a substrate and a second high-temperature resistant coating composited on the first high-temperature resistant coating; the first high-temperature resistant coating is composed of Al, Si, Al2O3 and NH4Br, and the second high-temperature resistant coating is composed of Al, Co, Cr, Ni and Fe.

[0054] The thickness of the composite coating prepared in the present invention is 310-380 μm, wherein the thickness of the first high-temperature resistant Al / Al2O3 composite coating is 230-280 μm, and the thickness of the second high-temperature resistant high-entropy alloy coating is 80-100 μm.

[0055] The following is further described in conjunction with specific embodiments.

[0056] Example 1

[0057] Step 1, pre-treating TP304H, washing it alternately with anhydrous ethanol and deionized water for 3 times, and preheating it at 220°C for 30 minutes.

[0058] Step 2: According to the mass fraction, 70% Al powder, 20% Si powder, 5% Al2O3 powder and 5% NH4Br powder are ball-milled for 20 hours to obtain the first solid phase powder, and the first solid phase powder is sprayed on the preheated substrate surface. The spraying voltage is 550V, the spraying current is 60A, the powder feeding gas and the protective gas are high-purity argon, hydrogen and nitrogen, and the gas flow rates are 45, 10 and 10L / min respectively, and the powder feeding amount is 20dm 3 / h, the spraying distance is 80mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to achieve better adhesion between the coating and the substrate.

[0059] After spraying, high temperature sintering is performed at 1000°C for 10 minutes, and argon gas is introduced during the sintering process.

[0060] Step 3, weigh each powder according to molar fraction, according to 30% aluminum powder, 17.5% Co powder, 17.5% Cr powder, 17.5% Ni powder and 17.5% Fe powder, and obtain the second solid phase powder after ball milling, the ball milling speed is 300r / min, and the ball milling time is 10h.

[0061] The second solid phase powder after ball milling was dried in a vacuum drying oven at a drying temperature of 100° C. for 2 h to obtain a dried second solid phase powder.

[0062] The dried second solid phase powder is laid on the first layer of high temperature resistant coating, and then laser cladding is performed. The laser cladding power is 3000W, the scanning speed is 8mm / s, the powder feeding speed is 10g / min, the spot diameter is 5mm, the powder feeding gas and the protective gas are high-purity argon, the cladding overlap rate is 50%, and a composite coating is obtained.

[0063] The prepared composite coating is shown in Figure 1As shown in the figure, the anti-oxidation ability of the pipe wall treated with the composite coating is about 40 times higher than that of the base material in a 600℃ pure water vapor environment, and about 50 times higher than that of the base material in a 650℃ pure water vapor environment.

[0064] Example 2

[0065] Step 1, pre-treating TP304H, washing it alternately with anhydrous ethanol and deionized water for 3 times, and preheating it at 220°C for 40 minutes.

[0066] Step 2: According to the mass fraction, 60% Al powder, 30% Si powder, 5% Al2O3 powder and 5% NH4Br powder are ball-milled for 20 hours to obtain the first solid phase powder, and the first solid phase powder is sprayed on the preheated substrate surface at a spraying voltage of 650V and a spraying current of 110A. The powder feeding gas and protective gas are high-purity argon, hydrogen and nitrogen, with gas flow rates of 60, 24 and 25L / min respectively, and the powder feeding amount is 40dm 3 / h, spraying distance is 120mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to make the coating and substrate have better adhesion. After spraying, high temperature sintering is carried out at 980℃ for 15min, and argon is introduced during the sintering process.

[0067] Step 3, weigh each powder according to molar fraction, according to 30% aluminum powder, 17.5% Co powder, 17.5% Cr powder, 17.5% Ni powder and 17.5% Fe powder, and obtain the second solid phase powder after ball milling, the ball milling speed is 300r / min, and the ball milling time is 10h.

[0068] The second solid phase powder after ball milling was dried in a vacuum drying oven at a drying temperature of 100° C. for 2 h to obtain a dried second solid phase powder.

[0069] The dried second solid phase powder is laid on the first layer of high temperature resistant coating, and then laser cladding is performed. The laser cladding power is 2000W, the scanning speed is 10mm / s, the powder feeding speed is 8g / min, the spot diameter is 3mm, the powder feeding gas and the protective gas are high-purity argon, the cladding overlap rate is 40%, and a composite coating is obtained.

[0070] Example 3

[0071] Step 1, pre-treating TP347H by alternately washing with anhydrous ethanol and deionized water for 3 times, and preheating at 220°C for 60 minutes.

[0072] Step 2: According to the mass fraction, 80% Al powder, 15% Si powder, 2% Al2O3 powder and 3% NH4Br powder are ball-milled for 6 hours to obtain the first solid phase powder, and the first solid phase powder is sprayed on the preheated substrate surface at a spraying voltage of 650V and a spraying current of 100A. The powder feeding gas and protective gas are high-purity argon, hydrogen and nitrogen, with gas flow rates of 50, 24 and 25L / min respectively, and the powder feeding amount is 35dm 3 / h, the spraying distance is 110mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to achieve better adhesion between the coating and the substrate.

[0073] After spraying, high temperature sintering is performed at 1000°C for 10 minutes, and argon gas is introduced during the sintering process.

[0074] Step 3, weigh each powder according to molar fraction, according to 25% aluminum powder, 18.75% Co powder, 18.75% Cr powder, 18.75% Ni powder and 18.75% Fe powder, and obtain the second solid phase powder after ball milling, the ball milling speed is 300 r / min, and the ball milling time is 10 h.

[0075] The second solid phase powder after ball milling was dried in a vacuum drying oven at a drying temperature of 120° C. for 2 h to obtain a dried second solid phase powder.

[0076] The dried second solid phase powder was laid on the first layer of high temperature resistant coating, and then laser cladding was performed. The laser cladding power was 2500W, the scanning speed was 12mm / s, the powder feeding speed was 5g / min, the spot diameter was 4mm, the powder feeding gas and the protective gas were high-purity argon, the cladding overlap rate was 45%, and a composite coating was obtained.

[0077] Example 4

[0078] Step 1, pre-treat Super304H by alternately washing with anhydrous ethanol and deionized water for 3 times, and preheating at 220°C for 50 minutes.

[0079] Step 2: According to the mass fraction, 80% Al powder, 5% Si powder, 10% Al2O3 powder and 5% NH4Br powder are ball-milled for 24 hours to obtain the first solid phase powder, and the first solid phase powder is sprayed on the preheated substrate surface at a spraying voltage of 600V and a spraying current of 80A. The powder feeding gas and protective gas are high-purity argon, hydrogen and nitrogen, and the gas flow rates are 35, 10 and 10L / min respectively, and the powder feeding amount is 30dm 3 / h, the spraying distance is 90mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to achieve better adhesion between the coating and the substrate.

[0080] After spraying, high temperature sintering is performed at 1150°C for 10 minutes, and argon gas is introduced during the sintering process.

[0081] Step 3, weigh each powder in mole fraction according to 28% aluminum powder, 18% Co powder, 18% Cr powder, 18% Ni powder and 18% Fe powder, and obtain the second solid phase powder after ball milling. The ball milling speed is 200 r / min and the ball milling time is 20 h.

[0082] The second solid phase powder after ball milling was dried in a vacuum drying oven at a drying temperature of 110° C. for 2 h to obtain a dried second solid phase powder.

[0083] The dried second solid phase powder is laid on the first layer of high temperature resistant coating, and then laser cladding is performed. The laser cladding power is 2000W, the scanning speed is 10mm / s, the powder feeding speed is 8g / min, the spot diameter is 3mm, the powder feeding gas and the protective gas are high-purity argon, the cladding overlap rate is 40%, and a composite coating is obtained.

[0084] Example 5

[0085] Step 1, pre-treating TP347HFG, washing it alternately with anhydrous ethanol and deionized water for 3 times, and preheating it at 220°C for 30 minutes.

[0086] Step 2: According to the mass fraction, 65% Al powder, 25% Si powder, 9% Al2O3 powder and 1% NH4Br powder are ball-milled for 10 hours to obtain the first solid phase powder, and the first solid phase powder is sprayed on the preheated substrate surface at a spraying voltage of 550V and a spraying current of 80A. The powder feeding gas and protective gas are high-purity argon, hydrogen and nitrogen, with gas flow rates of 40, 14 and 15 L / min respectively, and the powder feeding amount is 30 dm 3 / h, the spraying distance is 100mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to achieve better adhesion between the coating and the substrate.

[0087] After spraying, high temperature sintering is performed at 1100°C for 8 minutes, and argon gas is introduced during the sintering process.

[0088] Step 3, weigh each powder according to molar fraction, according to 30% aluminum powder, 17.5% Co powder, 17.5% Cr powder, 17.5% Ni powder and 17.5% Fe powder, and obtain the second solid phase powder after ball milling, the ball milling speed is 250r / min, and the ball milling time is 8h.

[0089] The second solid phase powder after ball milling was dried in a vacuum drying oven at a drying temperature of 100° C. for 2 h to obtain a dried second solid phase powder.

[0090] The dried second solid phase powder is laid on the first layer of high temperature resistant coating, and then laser cladding is performed. The laser cladding power is 3000W, the scanning speed is 8mm / s, the powder feeding speed is 10g / min, the spot diameter is 5mm, the powder feeding gas and the protective gas are high-purity argon, the cladding overlap rate is 50%, and a composite coating is obtained.

[0091] Example 6

[0092] Step 1, pre-treat HR3C by washing it three times alternately with anhydrous ethanol and deionized water, and preheating it at 220°C for 30 minutes.

[0093] Step 2: According to the mass fraction, 75% Al powder, 10% Si powder, 10% Al2O3 powder and 5% NH4Br powder are ball-milled for 15 hours to obtain the first solid phase powder, and the first solid phase powder is sprayed on the preheated substrate surface at a spraying voltage of 600V and a spraying current of 90A. The powder feeding gas and protective gas are high-purity argon, hydrogen and nitrogen, with gas flow rates of 50, 14 and 15 L / min respectively, and the powder feeding amount is 25 dm 3 / h, the spraying distance is 90mm. Before spraying, the substrate is sandblasted and cleaned with acetone to ensure the surface is clean and provide a certain surface roughness to achieve better adhesion between the coating and the substrate.

[0094] After spraying, high temperature sintering is performed at 1050°C for 12 minutes, and argon gas is introduced during the sintering process.

[0095] Step 3, weigh each powder according to molar fraction, according to 30% aluminum powder, 17.5% Co powder, 17.5% Cr powder, 17.5% Ni powder and 17.5% Fe powder, and obtain the second solid phase powder after ball milling, the ball milling speed is 250r / min, and the ball milling time is 20h.

[0096] The second solid phase powder after ball milling was dried in a vacuum drying oven at a drying temperature of 100° C. for 2 h to obtain a dried second solid phase powder.

[0097] The dried second solid phase powder is laid on the first layer of high temperature resistant coating, and then laser cladding is performed. The laser cladding power is 3000W, the scanning speed is 8mm / s, the powder feeding speed is 10g / min, the spot diameter is 5mm, the powder feeding gas and the protective gas are high-purity argon, the cladding overlap rate is 50%, and a composite coating is obtained.

[0098] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a high temperature resistant composite coating, characterized in that: The following steps are involved: Step 1, pre-treating the substrate; Step 2, Al powder, Si powder, Al2O3 powder and NH4Br powder are mixed, and a first solid phase powder is obtained after ball milling, and the first solid phase powder is sprayed on the surface of the substrate by plasma spraying to obtain a first high temperature resistant coating; Step 3, mix Al powder, Co powder, Cr powder, Ni powder, and Fe powder, obtain a second solid phase powder after ball milling, and obtain a second high temperature resistant coating by laser cladding the second solid phase powder on the first high temperature resistant coating; the molar fraction of Al powder in the second solid phase powder is 25% to 30%, and the other four powders are equal.

2. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: In step 1, the substrate pretreatment is to wash the substrate surface with anhydrous ethanol and deionized water in sequence for several times; In step 2, the substrate is preheated before plasma spraying.

3. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: In step 2, the ball milling speed is 350-450 r / min, and the ball milling time is 6-24 h.

4. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: In step 2, the first solid phase powder is composed of 60-80% Al powder, 5-30% Si powder, 2-10% Al2O3 powder and 1-5% NH4Br powder by mass fraction.

5. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: In step 3, before placing the second solid phase powder on the first high temperature resistant coating, the surface of the first high temperature resistant coating is cleaned with dilute hydrochloric acid.

6. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: In step 3, the ball milling speed during the ball milling of Al powder, Co powder, Cr powder, Ni powder and Fe powder is 200-300 r / min, and the ball milling time is 8-20 h.

7. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: The second solid phase powder is mixed and then dried at a temperature of 100-120° C. for 1-2 hours.

8. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: In step 3, the laser cladding power is 2000-3000W, the scanning speed is 8-12mm / s, the powder feeding speed is 5-10g / min, the spot diameter is 3-5mm, the powder feeding gas and the protective gas are high-purity argon, and the cladding overlap rate is 40-50%.

9. The method for preparing a high temperature resistant composite coating according to claim 1, characterized in that: The substrate is any one of TP304H, TP347H, Super304H, TP347HFG or HR3C.

10. A high temperature resistant composite coating prepared by the preparation method according to any one of claims 1 to 9, characterized in that: It includes a first high temperature resistant coating composited on a substrate and a second high temperature resistant coating composited on the first high temperature resistant coating; The first high temperature resistant coating is composed of Al, Si, Al2O3 and NH4Br, and the second high temperature resistant coating is composed of Al, Co, Cr, Ni and Fe.

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