A cermet composite gradient coating on the surface of a superalloy and a preparation method thereof

Abstract

A metal / ceramic composite gradient coating on the surface of a superalloy and a preparation method thereof. The present invention belongs to the field of chemical heat treatment, and specifically relates to a metal / ceramic composite gradient coating on the surface of a superalloy and a preparation method thereof. The coating is a multi-layer structure, which consists of an aluminide ceramic layer / a metal aluminide layer / a substrate from the outside to the inside in sequence; the preparation method of the coating is: pack cementation + micro-arc oxidation. In the first step, a metal aluminide coating is prepared by the method of pack cementation, and in the second step, an aluminide ceramic layer is prepared by the method of micro-arc oxidation; through this process, a coating with good bonding strength and uniformity can be obtained, the thermal protection performance of the superalloy can be improved, and it has the advantages of simple process, convenient operation, easy implementation, high efficiency, etc., and is suitable for production and application.

Description

Technical Field

[0001] The present invention belongs to the field of chemical heat treatment, and particularly relates to a metal / ceramic composite gradient coating on the surface of a superalloy and a preparation method thereof. Background Art

[0002] Superalloys such as titanium alloys, nickel alloys, and niobium alloys have characteristics such as high specific strength, specific stiffness, and high creep resistance, and are widely used in components such as aeroengine blades and turbine blades. Their service conditions are harsh, and they are prone to high-temperature oxidation, wear, and hot corrosion. The above-mentioned failure forms mainly occur and develop on the surface of the material. Therefore, it is necessary to prepare a coating on the surface of the alloy to improve its surface performance.

[0003] In recent years, the research on coatings on the surface of superalloys mainly includes plasma spraying, thermal spraying, magnetron sputtering, micro-arc oxidation, diffusion infiltration, laser cladding, etc. By preparing coatings through the above surface modification technologies, since the matrix alloy and the protective coating can be designed separately, the alloy components with the protective coating have excellent high-temperature corrosion resistance on the surface of the alloy components while maintaining sufficient high-temperature strength of the alloy.

[0004] The aluminide coating has a high melting point, good thermal stability, and excellent corrosion resistance, and is suitable for high-temperature oxidation protection of superalloys. However, when a single aluminide coating is oxidized, large internal stresses will be generated in the coating, resulting in the peeling off of the surface oxide film and loss of protection. Therefore, it is necessary to add other elements to modify it. Elements such as Cr, Si, B, Y, and Ce have significant effects in improving the densification of the coating and its bonding force with the matrix, reducing the oxidation rate of the alloy, and improving the spallation resistance of the oxide film. Micro-arc oxidation (MAO) is a surface modification technology for in-situ growth of an oxide film layer on the metal surface. In the technology of forming a ceramic layer, strong film-substrate bonding is achieved, and the wear and corrosion resistance of the coating is greatly improved.

[0005] At present, the preparation technology and application of a metal / ceramic composite gradient coating with high-temperature corrosion resistance and wear resistance on the surface of superalloys by the diffusion infiltration method + micro-arc oxidation technology are still blank. Therefore, the research and realization of the preparation technology of a metal / ceramic composite gradient coating with oxidation resistance, corrosion resistance, and wear resistance on the surface of superalloys are of great significance to the engineering application of superalloys. Summary of the Invention

[0006] In order to improve the thermal protection performance of superalloys such as titanium alloys, nickel alloys, and niobium alloys, the present invention provides a metal / ceramic composite gradient coating on the surface of a superalloy and a preparation method thereof. Through this process, a coating with good bonding force and uniformity can be obtained, the thermal protection performance of the superalloy is improved, and it has the advantages of simple process, convenient operation, easy realization, high efficiency, etc., and is suitable for production and application.

[0007] A metal / ceramic composite gradient coating on the surface of a superalloy, specifically including the following:

[0008] ① The elements to be infiltrated: including 10%-15% Al by mass percentage, with a particle size less than or equal to 100 mesh, 1%-2% Cr by mass percentage, with a particle size less than or equal to 100 mesh, 1%-2% Si by mass percentage, with a particle size less than or equal to 100 mesh, 0.2%-0.4% B by mass percentage, with a particle size less than or equal to 100 mesh, 0.5%-1% Y by mass percentage, with a particle size less than or equal to 100 mesh, 0.5%-1% Ce by mass percentage, with a particle size less than or equal to 100 mesh

[0009] ② The catalyst: including 4%-6% NH4Cl by mass percentage, 2%-3% NaF by mass percentage;

[0010] ③ The filler: Al2O3 with a particle size less than or equal to 200 mesh.

[0011] Preferably, the purity of NaF in the catalyst is analytical pure;

[0012] Preferably, the coating is a multi-layer structure, consisting of an aluminide ceramic layer / metal aluminide layer / substrate from outside to inside, and the coating contains rare earth elements Y and Ce. The ceramic oxide layer is in-situ grown as an aluminide ceramic layer / metal aluminide layer / substrate by the micro-arc oxidation method of the infiltrated elements.

[0013] A preparation method of a metal / ceramic composite gradient coating on the surface of a superalloy, which is a complete process route formed by the following steps:

[0014] The technical solution adopted by the present invention to solve its technical problems includes the following steps: as Figure 5 shown;

[0015] The first step: preparing a metal coating by the diffusion infiltration method

[0016] ① The specimen is polished with 80-600# sandpaper, then ultrasonically cleaned and dried;

[0017] ② Prepare the infiltration agent;

[0018] ③ Place the prepared infiltration agent in a ball mill and grind it to make it fully mixed;

[0019] ④ Place the infiltration agent in an oven at 95°C and keep it warm for 2 hours for drying;

[0020] ⑤ Put the dried infiltration agent into a crucible, and bury the specimen in the infiltration agent. The distance between adjacent parallel specimens is not less than 12 mm,

[0021] ⑥ Cover the crucible containing the specimen, seal it with water glass + clay, and place it in a high-temperature resistance furnace;

[0022] ⑦Heat the high-temperature resistance furnace to 910 - 930 °C in 2 h, hold at 910 - 930 °C for 1 - 2 h, then heat to 1050 °C in 0.5 h, hold at 1050 °C for 0.5 - 1 h, and air-cool to room temperature;

[0023] ⑧Rinse the sample after pack cementation with running water, then clean it with alcohol, and then dry it to end.

[0024] Preferably, it further includes the second step: in-situ growth of ceramic oxide layer by micro-arc oxidation method

[0025] ①Slightly polish the sample after pack cementation with 600# sandpaper, remove the surface adhesives, wash it with cold water, degrease it with acetone, ultrasonically clean it with alcohol, and then dry it for later use;

[0026] ②Prepare the micro-arc oxidation solution according to the formula, and stir the prepared solution evenly with a glass rod;

[0027] ③Connect the sample to the anode electrode of the micro-arc oxidation equipment, and use a stainless steel sheet as the cathode electrode;

[0028] ④Put the connected cathode and anode into the prepared solution, and place the cathode and anode parallel to each other;

[0029] ⑤To ensure the temperature of the solution during the experiment, use circulating water cooling (cool the circulating water with a refrigerator during the experiment), and keep the solution temperature at about 25 °C;

[0030] ⑥Start the micro-arc oxidation equipment, set its working voltage to 430 - 450 V, duty cycle to 24%, current frequency to 650 HZ, and working time to 5 - 10 min;

[0031] ⑦After the coating is prepared, turn off the micro-arc oxidation equipment;

[0032] ⑧Remove the sample after micro-arc oxidation, ultrasonically clean it with alcohol, and dry it to end.

[0033] Preferably, in step ③, a large cathode and small anode structure is adopted, and the area ratio of the cathode electrode to the anode electrode is ≥ 2:1.

[0034] Preferably, the distance between the anode and cathode electrodes in step ③ is 4 cm;

[0035] Preferably, the composition of the micro-arc oxidation solution is: 11 - 12 g / L sodium silicate Na2SiO3 (analytical pure), 2 - 4 g / L trisodium phosphate (analytical pure), 1 - 1.5 g / L sodium hydroxide (analytical pure), and the solvent is distilled water.

[0036] The beneficial effects of the present invention are as follows: The coating designed and prepared in the present invention has a multi-layer structure, which consists of an aluminide ceramic layer / a metal aluminide layer / a substrate from outside to inside. Moreover, the coating contains rare earth elements Y and Ce, and the ceramic oxide layer is in-situ grown into the aluminide ceramic layer / the metal aluminide layer / the substrate by the micro-arc oxidation method of the infiltrated elements.

[0037] Through this process, a coating with good bonding strength and uniformity can be obtained, which improves the thermal protection performance of superalloys. Additionally, it has the advantages of simple process, convenient operation, easy implementation, and high efficiency, being suitable for production and application. It solves the technical problems of poor oxidation resistance, corrosion resistance, and wear resistance of superalloys such as titanium alloys, niobium alloys, and nickel alloys. At the same time, the prepared metal / ceramic composite gradient coating can relieve the thermal stress between the film and the substrate during service. The equipment required for preparing the coating is simple, the process is stable and reliable, the coating has good bonding strength, uniform microstructure, and is easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1(a) is a micrograph of the surface of the metal / ceramic composite gradient coating obtained by Example 1 of the present invention;

[0039] Figure 1(b) is a micrograph of the cross-section of the metal / ceramic composite gradient coating obtained by Example 1 of the present invention;

[0040] Figure 2(a) is a micrograph of the surface of the metal / ceramic composite gradient coating obtained by Example 2 of the present invention;

[0041] Figure 2(b) is a micrograph of the cross-section of the metal / ceramic composite gradient coating obtained by Example 2 of the present invention;

[0042] Figure 3(a) is a micrograph of the surface of the metal / ceramic composite gradient coating obtained by Example 3 of the present invention;

[0043] Figure 3(b) is a micrograph of the cross-section of the metal / ceramic composite gradient coating obtained by Example 3 of the present invention;

[0044] Figure 4 It is an illustration of the structure of the cross-section of the metal / ceramic composite gradient coating obtained by Example 1 of the present invention.

[0045] Figure 5 It is a flow chart of the preparation steps of the metal-ceramic composite gradient coating by the method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0046] Example 1

[0047] The method flow of adopting the technical solution of the present invention is as follows: The first step: preparing a metal coating by the diffusion infiltration method: ① The sample is polished with 80 - 600# sandpaper and then ultrasonically cleaned and dried. ② Prepare the infiltration agent. By weight percentage, the composition of the infiltration agent is: 10% Al, 1% Cr, 1% Si, 0.2% B, 0.5% Y, 0.5% Ce, 4% NH4Cl, 2NaF, and the balance is Al2O3. ③ Place the prepared infiltration agent in a ball mill and grind it to make it fully mixed. ④ Place the infiltration agent in an oven at 95°C and keep it warm for 2 h for drying. ⑤ Load the dried infiltration agent into a crucible and bury the sample in the infiltration agent. The distance between adjacent parallel samples is not less than 12 mm. ⑥ Cover the crucible containing the sample and seal it with water glass + clay, and then place it in a high-temperature resistance furnace. ⑦ The high-temperature resistance furnace is heated for 2 h to 910°C, kept warm at 910°C for 1 h, then heated for 0.5 h to 1050°C, and kept warm at 1050°C for 0.5 h, and then air-cooled to room temperature. ⑧ The sample after embedding and infiltration is rinsed with running water, then cleaned with alcohol, and then dried to end. The second step: in-situ growing a ceramic oxide layer by the micro-arc oxidation method: ① The sample after embedding and infiltration is slightly polished with 600# sandpaper, the surface adherents are removed, then it is cleaned with cold water, degreased with acetone, ultrasonically cleaned with alcohol, and then dried for standby. ② Prepare the micro-arc oxidation solution: 11 g / L sodium silicate (Na2SiO3 analytical pure), 2 g / L trisodium phosphate (analytical pure), 1 g / L sodium hydroxide (analytical pure), and the solvent is distilled water. The prepared solution is stirred evenly with a glass rod. ③ Connect the sample to the anode of the micro-arc oxidation equipment, and the stainless steel sheet is the cathode, adopting a large cathode and small anode structure (cathode area: anode area ≥ 2:1). ④ Place the connected cathode and anode into the prepared solution, and the cathode and anode are placed in parallel with a distance of about 4 cm. ⑤ To ensure the temperature of the solution during the experiment, circulating water cooling is adopted (a refrigerator is used to cool the circulating water during the experiment), and the solution temperature is kept at about 25 degrees Celsius. ⑥ Start the micro-arc oxidation equipment, set its working voltage to 430 V, duty cycle to 24%, current frequency to 650 HZ, and working time to 5 min. ⑦ After the coating is prepared, turn off the micro-arc oxidation equipment. ⑧ Unload the sample after micro-arc oxidation, ultrasonically clean it with alcohol, and dry it to end.

[0048] Example 2

[0049] The method flow of adopting the technical solution of the present invention is as follows: The first step: preparing a metal coating by the diffusion infiltration method: ① The sample is polished with 80-600# sandpaper and then ultrasonically cleaned and dried. ② Prepare the infiltrant. By weight percentage, the composition of the infiltrant is: 12% Al, 1.5% Cr, 1.5% Si, 0.3% B, 0.7% Y, 0.7% Ce, 5% NH4Cl, 2.5% NaF, and the balance is Al2O3. ③ Place the prepared infiltrant in a ball mill and grind it to make it fully mixed. ④ Place the infiltrant in an oven at 95°C and keep it warm for 2 h for drying. ⑤ Load the dried infiltrant into a crucible and bury the sample in the infiltrant. The distance between adjacent parallel samples is not less than 12 mm. ⑥ Cover the crucible containing the sample, seal it with water glass + clay, and then place it in a high-temperature resistance furnace. ⑦ The high-temperature resistance furnace is heated to 920°C in 2 h, kept warm at 920°C for 1.5 h, then heated to 1050°C in 0.5 h, kept warm at 1050°C for 0.7 h, and air-cooled to room temperature. ⑧ Rinse the sample after embedding and infiltration with running water, then clean it with alcohol, and then dry it to end. The second step: in-situ growing a ceramic oxide layer by the micro-arc oxidation method: ① Slightly polish the sample after embedding and infiltration with 600# sandpaper, remove the surface adhesives, then wash it with cold water, degrease it with acetone, ultrasonically clean it with alcohol, and then dry it for later use. ② Prepare the micro-arc oxidation solution: 11.5 g / L sodium silicate (Na2SiO3, analytical pure), 3 g / L trisodium phosphate (analytical pure), 1.2 g / L sodium hydroxide (analytical pure), and the solvent is distilled water. Stir the prepared solution evenly with a glass rod. ③ Connect the sample to the anode of the micro-arc oxidation device, and use a stainless steel sheet as the cathode, adopting a large cathode and small anode structure (cathode area: anode area ≥ 2:1). ④ Place the connected cathode and anode into the prepared solution, place the cathode and anode parallel to each other, and the distance is about 4 cm. ⑤ To ensure the temperature of the solution during the experiment, use circulating water cooling (cool the circulating water with a refrigerator during the experiment) to keep the solution temperature at about 25 degrees Celsius. ⑥ Start the micro-arc oxidation device, set its working voltage to 440 V, duty cycle to 24%, current frequency to 650 HZ, and working time to 7 min. ⑦ Turn off the micro-arc oxidation device after the coating is prepared. ⑧ Remove the sample after micro-arc oxidation, ultrasonically clean it with alcohol, and dry it to end.

[0050] Example 3

[0051] The method flow of adopting the technical solution of the present invention is as follows: The first step: preparing a metal coating by diffusion infiltration method: ① The sample is polished with 80-600# sandpaper and then ultrasonically cleaned and dried. ② Prepare the infiltrant. By weight percentage, the composition of the infiltrant is: 15% Al, 2% Cr, 2% Si, 0.4% B, 1% Y, 1% Ce, 6% NH4Cl, 3% NaF, and the balance is Al2O3. ③ Place the prepared infiltrant in a ball mill and grind it to make it fully mixed. ④ Place the infiltrant in an oven at 95°C and keep it warm for 2 hours for drying. ⑤ Load the dried infiltrant into a crucible and bury the sample in the infiltrant. The distance between adjacent parallel samples is not less than 12 mm. ⑥ Cover the crucible containing the sample and seal it with water glass + clay, and then place it in a high-temperature resistance furnace. ⑦ The high-temperature resistance furnace is heated to 930°C in 2 hours, kept warm at 930°C for 2 hours, then heated to 1050°C in 0.5 hour, and kept warm at 1050°C for 1 hour, and then air-cooled to room temperature. ⑧ Wash the sample after embedding and infiltration with running water, then clean it with alcohol, and then dry it to end. The second step: in-situ growth of a ceramic oxide layer by micro-arc oxidation method: ① Slightly polish the sample after embedding and infiltration with 600# sandpaper, remove the surface adhesives, then wash it with cold water, degrease it with acetone, ultrasonically clean it with alcohol, and then dry it for later use. ② Prepare the micro-arc oxidation solution: 12 g / L sodium silicate (Na2SiO3, analytical pure), 4 g / L trisodium phosphate (analytical pure), 1.5 g / L sodium hydroxide (analytical pure), and the solvent is distilled water. Stir the prepared solution evenly with a glass rod. ③ Connect the sample to the anode of the micro-arc oxidation equipment, and use a stainless steel sheet as the cathode, adopting a large cathode and small anode structure (cathode area: anode area ≥ 2:1). ④ Place the connected cathode and anode into the prepared solution, place the cathode and anode parallel to each other, and the distance is about 4 cm. ⑤ To ensure the temperature of the solution during the experiment, use circulating water cooling (cool the circulating water with a refrigerator during the experiment) to keep the solution temperature at about 25 degrees Celsius. ⑥ Start the micro-arc oxidation equipment, set its working voltage to 450 V, duty cycle to 24%, current frequency to 650 HZ, and working time to 10 minutes. ⑦ After the coating is prepared, turn off the micro-arc oxidation equipment. ⑧ Remove the sample after micro-arc oxidation, ultrasonically clean it with alcohol, and dry it to end.

[0052] Figures 1 to 3 are the microscopic morphology diagrams of the surface and cross-section of the metal / ceramic composite gradient coatings obtained by using Embodiments 1 to 3 of the present invention. As Figure 4 shown, the coating is mainly composed of an aluminide layer and a ceramic layer. Therefore, the preparation of the metal / ceramic composite gradient coating on the surface of the superalloy is realized, and the quality of the whole coating is good.

Claims

1. A metal / ceramic composite gradient coating on the surface of a superalloy, characterized in that: Specifically, it includes the following contents: ① The elements to be infiltrated: including Al with a mass percentage of 10%-15% and a particle size less than or equal to 100 mesh, Cr with a mass percentage of 1%-2% and a particle size less than or equal to 100 mesh, Si with a mass percentage of 1%-2% and a particle size less than or equal to 100 mesh, B with a mass percentage of 0.2%-0.4% and a particle size less than or equal to 100 mesh, Y with a mass percentage of 0.5%-1% and a particle size less than or equal to 100 mesh, Ce with a mass percentage of 0.5%-1% and a particle size less than or equal to 100 mesh ② The catalyst: including NH4Cl with a mass percentage of 4%-6% and NaF with a mass percentage of 2%-3%; ③ The filler: Al2O3 with a particle size less than or equal to 200 mesh; This coating is a multi-layer structure, consisting of an aluminide ceramic layer / metal aluminide layer / substrate from outside to inside, and the coating contains rare earth elements Y and Ce. The ceramic oxide layer is in-situ grown by the micro-arc oxidation method of the infiltrated elements to form the aluminide ceramic layer / metal aluminide layer / substrate.

2. The metal / ceramic composite gradient coating on the surface of a superalloy according to claim 1, wherein: The purity of NaF in the said catalyst is analytical pure.

3. A method for preparing a metal / ceramic composite gradient coating on the surface of a superalloy, characterized in that: A complete process route formed by the following steps: The first step: preparing a metal coating by the diffusion infiltration method ① The specimen is polished with 80-600# sandpaper, then ultrasonically cleaned and dried. ② Prepare the infiltrant. ③ Place the prepared infiltrant in a ball mill and grind it to make it fully mixed. ④ Place the infiltrant in an oven at 95°C and keep it warm for 2h for drying. ⑤ Load the dried infiltrant into a crucible, and bury the specimen in the infiltrant. The distance between adjacent parallel specimens is not less than 12mm. ⑥ Cover the crucible containing the specimen, seal it with water glass + clay, and then place it in a high-temperature resistance furnace. ⑦ The high-temperature resistance furnace is heated for 2h to 910-930°C, kept warm at 910-930°C for 1-2h, then heated for 0.5h to 1050°C, kept warm at 1050°C for 0.5-1h, and air-cooled to room temperature. ⑧ The specimen after the embedding infiltration is rinsed with running water, then cleaned with alcohol, and then dried to end.

4. A method for preparing a metal / ceramic composite gradient coating on the surface of a superalloy as described in claim 3, characterized in that: It further includes the second step: in-situ growing a ceramic oxide layer by the micro-arc oxidation method ① The specimen after the embedding infiltration is slightly polished with 600# sandpaper, the surface adherents are removed, then it is cold-cleaned, degreased with acetone, ultrasonically cleaned with alcohol, and then dried for later use. ② Prepare the micro-arc oxidation solution according to the formula, and stir the prepared solution evenly with a glass rod. ③ Connect the specimen to the anode electrode of the micro-arc oxidation equipment, and use a stainless steel sheet as the cathode electrode. ④ Place the connected cathode and anode into the prepared solution, with the cathode and anode placed in parallel. ⑤ To ensure the temperature of the solution during the experiment, circulating water cooling is used, and a refrigerator is used to cool the circulating water during the experiment to keep the solution temperature at 25 degrees Celsius. ⑥ Start the micro-arc oxidation equipment, set its working voltage to 430-450V, duty cycle to 24%, current frequency to 650HZ, and working time to 5-10min. ⑦ After the coating preparation is completed, turn off the micro-arc oxidation equipment. ⑧ Remove the specimen after the micro-arc oxidation, ultrasonically clean it with alcohol, and dry it to end.

5. The preparation method of a metal / ceramic composite gradient coating on the surface of a superalloy according to claim 4, characterized in that: In step ③, a large cathode and small anode structure is adopted, and the area of the cathode electrode: the area of the anode electrode ≥ 2:

1.

6. The preparation method of a metal / ceramic composite gradient coating on the surface of a superalloy according to claim 4, characterized in that: In step ③, the electrode distance between the anode and the cathode is 4 cm.

7. A method for preparing a metal / ceramic composite gradient coating on the surface of a superalloy as described in claim 4, characterized in that: The composition of the micro-arc oxidation solution is as follows: 11-12 g / L of sodium silicate (Na2SiO3, analytical pure), 2-4 g / L of trisodium phosphate (analytical pure), 1-1.5 g / L of sodium hydroxide (analytical pure), and the solvent is distilled water.

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