A method for producing a molten salt non-electrolytic modified coating on a molybdenum or molybdenum alloy surface

Abstract

This invention belongs to the field of metal coating preparation technology, specifically a method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloys. The method involves selecting at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder. A Mo-Si-B-Hf composite coating is prepared on the surface of the molybdenum alloy using a molten salt non-electrolytic process. MoSi2, as the base material of the coating, ensures the antioxidant properties of the composite coating. Adding appropriate amounts of B and Hf elements further improves the antioxidant properties of the coating, ultimately achieving good antioxidant properties, good density, and durability, meeting the requirements for applications of molybdenum or molybdenum alloys in high-temperature service environments.

Description

Technical Field

[0001] This invention belongs to the field of metal coating preparation technology, specifically a method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy. Background Technology

[0002] Molybdenum and molybdenum alloys, as commonly used refractory metals, possess high strength and hardness, high melting point, low coefficient of thermal expansion, good electrical and thermal conductivity, and excellent corrosion resistance even at 1500℃. They are widely used in structural components operating under high-temperature conditions in industries such as aerospace, metallurgy, glass, and electronics. In molybdenum alloys, titanium and zirconium form Mo-Ti and Mo-Zr solid solutions with molybdenum, respectively, resulting in solid solution strengthening. Carbon in the matrix forms TiC and ZrC dispersed particles with titanium and zirconium, creating dispersion strengthening. Therefore, molybdenum alloys exhibit good mechanical properties, especially at high temperatures, where their mechanical properties are better than pure molybdenum. However, under high-temperature operating conditions, molybdenum alloys are highly susceptible to rapid oxidation, causing them to lose their excellent high-temperature properties and leading to structural component failure, thus limiting their wider application. Therefore, improving the oxidation resistance of molybdenum and molybdenum alloys is crucial to ensuring their long-term safe service.

[0003] Current research indicates that the limited alloying of molybdenum alloys results in high-temperature oxidation resistance that does not yet meet service requirements. Therefore, surface coatings are commonly used to improve the oxidation resistance of molybdenum alloys and ensure their safe service. MoSi2 coatings are widely used in the design of anti-oxidation surfaces for molybdenum alloys because they can react with O2 at high temperatures to form a chemically stable SiO2 glass phase. The low oxygen diffusion rate of MoSi2 can prevent O2 from diffusing into the coating interior, thereby reducing the rate of oxygen erosion. However, it still has defects such as weak substrate adhesion, poor coating density, and internal microcracks, so it needs to be modified and optimized. Summary of the Invention

[0004] To address the problems existing in the prior art, the main objective of this invention is to propose a method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloys, optimizing the density and microstructure of existing MoSi2 coatings, achieving atomic penetration of Hf and B elements into the coating, and improving the coating's oxidation resistance and durability.

[0005] To address the aforementioned technical problems, according to one aspect of the present invention, the present invention provides the following technical solution:

[0006] A method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloys includes the following steps:

[0007] B1. A molybdenum or molybdenum alloy matrix is ​​embedded in a modified powder for the surface of molybdenum or molybdenum alloy; wherein the modified powder for the surface of molybdenum or molybdenum alloy contains 35-94.8 wt% NaCl-KCl-NaF powder, 0-20 wt% Na2SiF6 powder, 5-20 wt% Si powder, at least one of borax and B4C powder, and 0.1-10 wt% HfB2 powder;

[0008] B2. By controlling the heating temperature and heating time, a molten salt non-electrolytic modified coating is obtained on the surface of molybdenum or molybdenum alloy.

[0009] In a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention, the method further includes, before step B1, the following steps:

[0010] B0. Polish the molybdenum or molybdenum alloy substrate with sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0011] As a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention, in step B1, the thickness of the modified powder for the surface of molybdenum or molybdenum alloy covering the molybdenum or molybdenum alloy substrate is ≥3mm.

[0012] In a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy as described in this invention, in step B2, the heating temperature is 850–1050°C and the heating time is 2–8 h.

[0013] As a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention, the method for preparing the modified powder for the surface of molybdenum or molybdenum alloy includes the following steps:

[0014] S1. Take at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder for later use;

[0015] S2. Place at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 150-250 rpm and the ball milling time is 2-3 hours.

[0016] S3. Place the mixed powder in a dryer and dry it to obtain a modified powder for use on the surface of molybdenum or molybdenum alloys.

[0017] In a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention, before step S1, the method further includes:

[0018] S0. Grind at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder using a grinding bowl.

[0019] As a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention, in step S1, the particle size of at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder is 3-50 μm.

[0020] As a preferred embodiment of the method for preparing the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention, in step S2, the ball milling is performed in both forward and reverse directions, and the forward and reverse directions are performed for the same time.

[0021] The beneficial effects of this invention are as follows:

[0022] This invention proposes a method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloys. The method involves selecting at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder. A Mo-Si-B-Hf composite coating is prepared on the surface of the molybdenum alloy using a molten salt non-electrolytic process. MoSi2 serves as the base material of the coating, ensuring its antioxidant properties. Adding appropriate amounts of B and Hf elements further enhances the coating's antioxidant properties, ultimately achieving good antioxidant performance, good density, and durability, thus meeting the application requirements of molybdenum or molybdenum alloys under high-temperature service environments. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy according to the present invention.

[0025] Figure 2 This is a cross-sectional SEM image of the coating in Embodiment 3 of the present invention.

[0026] Figure 3EDS characterization of the cross-section of the coating in Example 3 of the present invention.

[0027] Figure 4 This is a cross-sectional SEM image of the coating in Embodiment 6 of the present invention.

[0028] Figure 5 EDS characterization of the cross-section of the coating in Example 6 of the present invention.

[0029] Figure 6 This is a cross-sectional SEM image of the coating in Embodiment 9 of the present invention.

[0030] Figure 7 EDS characterization of the cross-section of the coating of Example 9 of the present invention.

[0031] Figure 8 This is a cross-sectional SEM image of the coating of Comparative Example 1 of the present invention.

[0032] Figure 9 EDS characterization of the cross-section of the coating of Comparative Example 1 of the present invention.

[0033] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0034] The technical solutions described below in conjunction with the embodiments will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention proposes a method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloys, which optimizes the density and microstructure of existing MoSi2 coatings, achieves atomic penetration of Hf and B elements into the coating, and improves the oxidation resistance and durability of the coating.

[0036] According to one aspect of the present invention, the present invention provides the following technical solution:

[0037] A method for preparing a molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloys includes the following steps:

[0038] B1. A molybdenum or molybdenum alloy matrix is ​​embedded in the aforementioned modified powder for the surface of molybdenum or molybdenum alloy; wherein the modified powder for the surface of molybdenum or molybdenum alloy contains 35–94.8 wt% NaCl-KCl-NaF powder, 0–20 wt% Na2SiF6 powder, 5–20 wt% Si powder, at least one of borax and B4C powder (0.1–10 wt%), and 0.1–15 wt% HfB2 powder; specifically, the content of NaCl-KCl-NaF powder in the modified powder for the surface of molybdenum or molybdenum alloy can be, for example, but not limited to, 35 wt%, 45 wt%, 55 wt%, 65 wt%, 75 wt%, etc. The content of Na2SiF6 powder can be, for example, but not limited to, 0 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, 20 wt%, or a range between any two; the content of at least one of borax and B4C powder can be, for example, but not limited to, 0.1 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, or a range between any two; the content of HfB2 powder can be, for example, but not limited to, 0.1 wt%, 1 wt%, 2 wt%, 5 wt%, 10 wt%, 15 wt%, or a range between any two.

[0039] B2. By controlling the heating temperature and heating time, a molten salt non-electrolytic modified coating is obtained on the surface of molybdenum or molybdenum alloys, such as... Figure 1 As shown, the molten salt non-electrolytic modified coating on the surface of molybdenum or molybdenum alloy has a smooth surface with no obvious macroscopic defects.

[0040] Preferably, the method further includes the following steps before step B1:

[0041] B0. The molybdenum or molybdenum alloy substrate is polished with sandpaper, then cleaned with anhydrous ethanol, and then dried for later use. The sandpaper used is 400-2000 grit sandpaper; different grits may be selected as needed for polishing.

[0042] Preferably, in step B1, the thickness of the modified powder covering the molybdenum or molybdenum alloy substrate for the surface of the molybdenum or molybdenum alloy is ≥3mm, and the molybdenum alloy is a commonly used molybdenum alloy in the art, such as Mo-Zr-C molybdenum alloy, etc.

[0043] Preferably, in step B2, a muffle furnace / tube furnace is used with a thermocouple as the heat source, the heating temperature is controlled at 850–1050°C, and the heating time is 2–8 hours. The modified powder for the surface of molybdenum or molybdenum alloy is prepared on the molybdenum alloy substrate using a molten salt non-electrolytic method. Specifically, the heating temperature can be, for example, but not limited to, any one or any two of 850°C, 900°C, 950°C, 1000°C, and 1050°C; the heating time can be, for example, but not limited to, any one or any two of 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, and 8 hours.

[0044] Preferably, the method for preparing the modified powder for the surface of molybdenum or molybdenum alloy includes the following steps:

[0045] S1. Take at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder for later use;

[0046] S2. Place at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 150-250 rpm and the ball milling time is 2-3 hours.

[0047] S3. Place the mixed powder in a dryer and dry it to obtain a modified powder for use on the surface of molybdenum or molybdenum alloys.

[0048] Preferably, before step S1, the method further includes:

[0049] S0. Grind at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder using a grinding bowl.

[0050] Preferably, in step S1, the particle size of at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder is 3–50 μm. Specifically, the particle size of NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, at least one of borax and B4C powder, and HfB2 powder can be, for example, but not limited to, any one or any combination of 3 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, and 50 μm.

[0051] Preferably, in step S2, the ball milling speed can be, for example, but not limited to, any one or a range between any two of 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, and 250 rpm; the ball milling time can be, for example, but not limited to, any one or a range between any two of 2 h, 2 h 15 min, 2 h 30 min, 2 h 45 min, and 3 h; more preferably, the forward and reverse rotation during ball milling can be performed by first performing forward rotation for half the ball milling time, and then performing reverse rotation for the other half of the ball milling time; or it can be performed by first performing forward rotation for a certain time, then performing reverse rotation for the same time, then performing forward rotation for a certain time, then performing reverse rotation for the same time, until the ball milling is completed.

[0052] Preferably, in step S3, the drying can be performed using a conventional drying method in the art.

[0053] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0054] Example 1

[0055] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0056] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0057] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0058] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0059] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0060] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0061] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 5wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 5wt%, and the content of HfB2 powder is 5wt%.

[0062] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 850℃ and the heating time is 8h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the surface of molybdenum alloy.

[0063] Example 2

[0064] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum surface includes the following steps:

[0065] B0. Polish the molybdenum substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0066] B1. Embed the molybdenum matrix into the above-mentioned powder for molybdenum surface modification; the thickness of the powder covering the molybdenum matrix is ​​4 mm; the powder for molybdenum surface modification is prepared by the following method:

[0067] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax and HfB2 powders were ground using a grinding bowl;

[0068] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax and HfB2 powders are all 3 to 50 μm;

[0069] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax and HfB2 powders in a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0070] S3. The mixed powder is placed in a dryer and dried to obtain a powder for molybdenum surface modification, wherein the content of NaCl-KCl-NaF powder is 70wt%, the content of Na2SiF6 powder is 10wt%, the content of Si powder is 10wt%, the content of borax is 5wt%, and the content of HfB2 powder is 5wt%.

[0071] B2. Using a tube furnace with a thermocouple as the heat source, the heating temperature is controlled at 900℃ and the heating time is 4h. The powder used for molybdenum surface modification is prepared on the molybdenum substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the molybdenum surface.

[0072] Example 3

[0073] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0074] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0075] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0076] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0077] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0078] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0079] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 70wt%, the content of Na2SiF6 powder is 10wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 5wt%, and the content of HfB2 powder is 5wt%.

[0080] B2. Using a muffle furnace and a thermocouple as the heat source, the heating temperature was controlled at 950℃ for 6 hours. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate using a molten salt non-electrolytic method, resulting in a molten salt non-electrolytic modified coating on the surface of the molybdenum alloy. The cross-sectional SEM image is shown below. Figure 2 As shown, its cross-sectional EDS characterization is as follows Figure 3As shown, no obvious microcracks were observed inside the coating, the microstructure was fine, and the interface bonding was good. The Si, B, and Hf elements showed a clear stepped distribution in the EDS characterization diagram, indicating that the Mo-Si-B-Hf coating was successfully prepared.

[0081] Example 4

[0082] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0083] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0084] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder covering the molybdenum alloy substrate for molybdenum alloy surface modification is 5 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0085] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0086] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0087] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders in a ball mill and mix them to obtain a mixed powder. The ball milling speed is 150 rpm and the ball milling time is 3 hours, with 1.5 hours in each direction.

[0088] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 35wt%, the content of Na2SiF6 powder is 20wt%, the content of Si powder is 20wt%, the total content of borax and B4C powder is 10wt%, and the content of HfB2 powder is 15wt%.

[0089] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 1000℃ and the heating time is 4h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the surface of molybdenum alloy.

[0090] Example 5

[0091] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0092] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0093] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0094] S0. NaCl-KCl-NaF, Si, B4C and HfB2 powders were ground using a grinding bowl;

[0095] S1. Prepare NaCl-KCl-NaF, Si, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Si, B4C and HfB2 powders is 3-50 μm;

[0096] S2. Place NaCl-KCl-NaF, Si, B4C and HfB2 powders in a ball mill and mix them to obtain a mixed powder. The ball milling speed is 250 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0097] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 90wt%, the content of Si powder is 5wt%, the total content of B4C powder is 2wt%, and the content of HfB2 powder is 3wt%.

[0098] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 900℃ and the heating time is 6h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the surface of molybdenum alloy.

[0099] Example 6

[0100] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0101] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0102] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0103] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0104] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0105] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0106] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 70wt%, the content of Na2SiF6 powder is 10wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 2wt%, and the content of HfB2 powder is 8wt%.

[0107] B2. Using a muffle furnace and a thermocouple as the heat source, the heating temperature was controlled at 950℃ for 4 hours. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate using a molten salt non-electrolytic method, resulting in a molten salt non-electrolytic modified coating on the surface of the molybdenum alloy. The cross-sectional SEM image is shown below. Figure 4 As shown, its cross-sectional EDS characterization is as follows Figure 5 As shown, no obvious microcracks were observed inside the coating, the microstructure was fine, and the interface bonding was good. The Si, B, and Hf elements showed a clear stepped distribution in the EDS characterization diagram, indicating that the Mo-Si-B-Hf coating was successfully prepared.

[0108] Example 7

[0109] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0110] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0111] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0112] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0113] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0114] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0115] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 70wt%, the content of Na2SiF6 powder is 10wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 2wt%, and the content of HfB2 powder is 8wt%.

[0116] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 1000℃ and the heating time is 6h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the surface of molybdenum alloy.

[0117] Example 8

[0118] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0119] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0120] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0121] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0122] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0123] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0124] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 70wt%, the content of Na2SiF6 powder is 9wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 1wt%, and the content of HfB2 powder is 10wt%.

[0125] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 900℃ and the heating time is 6h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the surface of molybdenum alloy.

[0126] Example 9

[0127] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0128] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0129] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0130] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0131] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0132] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0133] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 70wt%, the content of Na2SiF6 powder is 9wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 1wt%, and the content of HfB2 powder is 10wt%.

[0134] B2. Using a muffle furnace and a thermocouple as the heat source, the heating temperature was controlled at 950℃ for 5 hours. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate using a molten salt non-electrolytic method, resulting in a molten salt non-electrolytic modified coating on the surface of the molybdenum alloy. The cross-sectional SEM image is shown below. Figure 6 As shown, its cross-sectional EDS characterization is as follows Figure 7 As shown, no obvious microcracks were observed inside the coating, the microstructure was fine, and the interface bonding was good. The Si, B, and Hf elements showed a clear stepped distribution in the EDS characterization diagram, indicating that the Mo-Si-B-Hf coating was successfully prepared.

[0135] Example 10

[0136] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0137] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0138] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0139] S0. NaCl-KCl-NaF, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0140] S1. Prepare NaCl-KCl-NaF, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Si, borax, B4C and HfB2 powders is 3-50 μm;

[0141] S2. Place NaCl-KCl-NaF, Si, borax, B4C and HfB2 powders in a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0142] S3. The mixed powder is dried in a dryer to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 94.8 wt%, the content of Si powder is 5 wt%, the total content of borax and B4C powder is 0.1 wt%, and the content of HfB2 powder is 0.1 wt%.

[0143] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 1000℃ and the heating time is 8h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis modified coating is obtained on the surface of molybdenum alloy.

[0144] Comparative Example 1

[0145] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0146] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0147] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0148] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, and B4C powders were ground using a grinding bowl;

[0149] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, and B4C powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, and B4C powders is 3-50 μm.

[0150] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, and B4C powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0151] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 10wt%, the content of Si powder is 10wt%, and the total content of borax and B4C powder is 5wt%.

[0152] B2. Using a muffle furnace and a thermocouple as the heat source, the heating temperature was controlled at 950℃ for 3 hours. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate using a molten salt non-electrolytic method, resulting in a molten salt non-electrolytic B-modified coating on the surface of the molybdenum alloy. The cross-sectional SEM image is shown below. Figure 8 As shown, its cross-sectional EDS characterization is as follows Figure 9 As shown, there are obvious micro-cracks inside the coating. Antioxidant experiments show that the severe oxidation temperature is below 1300℃.

[0153] Comparative Example 2

[0154] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0155] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0156] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0157] S0. NaCl-KCl-NaF, Na2SiF6, and Si powders were ground using a grinding bowl;

[0158] S1. Prepare NaCl-KCl-NaF, Na2SiF6, and Si powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, and Si powders is 3-50 μm.

[0159] S2. Place NaCl-KCl-NaF, Na2SiF6, and Si powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0160] S3. The mixed powder is dried in a dryer to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 10wt%, and the content of Si powder is 15wt%.

[0161] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 950℃ and the heating time is 3h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method, and a molten salt non-electrolysis MoSi2 coating is obtained on the surface of the molybdenum alloy. The oxidation resistance temperature is still low, less than 1300℃.

[0162] Comparative Example 3

[0163] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0164] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0165] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0166] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0167] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0168] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0169] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 50wt%, the content of Na2SiF6 powder is 5wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 15wt%, and the content of HfB2 powder is 20wt%.

[0170] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature was controlled at 850℃ and the heating time was 8h. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate by molten salt non-electrolysis. It was found that as the content of B and Hf increased, the fluidity of the molten salt was poor and the coating was difficult to form.

[0171] Comparative Example 4

[0172] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0173] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0174] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0175] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0176] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0177] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0178] S3. The mixed powder is dried in a dryer to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 84.9 wt%, the content of Na2SiF6 powder is 5 wt%, the content of Si powder is 10 wt%, the total content of borax and B4C powder is 0.05 wt%, and the content of HfB2 powder is 0.05 wt%.

[0179] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature was controlled at 850℃ and the heating time was 8h. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate by molten salt non-electrolysis method. The study found that no B or Hf modifying elements were found in the coating.

[0180] Comparative Example 5

[0181] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0182] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0183] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0184] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0185] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0186] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0187] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 5wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 5wt%, and the content of HfB2 powder is 5wt%.

[0188] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature is controlled at 750℃ and the heating time is 8h. The powder used for surface modification of molybdenum alloy is prepared on the molybdenum alloy substrate by molten salt non-electrolysis method. Studies have shown that at lower temperatures, the diffusion rate of the modifying element Hf is slower and it is difficult to enter the coating.

[0189] Comparative Example 6

[0190] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0191] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0192] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0193] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0194] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0195] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0196] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 5wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 5wt%, and the content of HfB2 powder is 5wt%.

[0197] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature was controlled at 1200℃ and the heating time was 8h. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate by molten salt non-electrolysis. Studies have shown that if the heating temperature is too high, the prepared coating will crack.

[0198] Comparative Example 7

[0199] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0200] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0201] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0202] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0203] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0204] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0205] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 5wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 5wt%, and the content of HfB2 powder is 5wt%.

[0206] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature was controlled at 850℃ and the heating time was 1 hour. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate by molten salt non-electrolysis. Studies have shown that if the heating time is too short, the diffusion path of the modifying element Hf is too short, and uniform modification inside the coating cannot be completed.

[0207] Comparative Example 8

[0208] A method for preparing a molten salt non-electrolytic modified coating on a molybdenum alloy surface includes the following steps:

[0209] B0. Polish the molybdenum alloy substrate with 400-2000 grit sandpaper, then clean it with anhydrous ethanol, and then dry it for later use.

[0210] B1. Embed the molybdenum alloy substrate into the above-mentioned modified powder for molybdenum or molybdenum alloy surface; the thickness of the powder for molybdenum alloy surface modification covering the molybdenum alloy substrate is 3 mm; the powder for molybdenum alloy surface modification is prepared by the following method:

[0211] S0. NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders were ground using a grinding bowl;

[0212] S1. Prepare NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders for later use; the particle size of NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders are all 3 to 50 μm;

[0213] S2. Place NaCl-KCl-NaF, Na2SiF6, Si, borax, B4C and HfB2 powders into a ball mill and mix them to obtain a mixed powder. The ball milling speed is 200 rpm and the ball milling time is 2 hours, with 1 hour in each direction.

[0214] S3. The mixed powder is placed in a dryer and dried to obtain a powder for surface modification of molybdenum alloy, wherein the content of NaCl-KCl-NaF powder is 75wt%, the content of Na2SiF6 powder is 5wt%, the content of Si powder is 10wt%, the total content of borax and B4C powder is 5wt%, and the content of HfB2 powder is 5wt%.

[0215] B2. Using a muffle furnace with a thermocouple as the heat source, the heating temperature was controlled at 850°C and the heating time was 12 hours. The powder used for surface modification of molybdenum alloy was prepared on the molybdenum alloy substrate by molten salt non-electrolysis. Studies have shown that long-term high-temperature heating during preparation leads to coating cracking.

[0216] This invention selects at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder to prepare a Mo-Si-B-Hf composite coating on the surface of a molybdenum alloy using a molten salt non-electrolysis process. MoSi2, as the base material of the coating, ensures the antioxidant properties of the composite coating. Adding appropriate amounts of B and Hf elements can further improve the antioxidant properties of the coating. Ultimately, the coating achieves good antioxidant properties, good density, and durability, which can meet the application requirements of molybdenum or molybdenum alloys in high-temperature service environments.

[0217] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for producing a molten salt non-electrolytically modified coating of a molybdenum or molybdenum alloy surface, characterized in that, The method comprises the following steps: B1, embedding a molybdenum or molybdenum alloy substrate into a modified powder for a molybdenum or molybdenum alloy surface; in the modified powder for the molybdenum or molybdenum alloy surface, the content of NaCl-KCl-NaF powder is 35-94.8wt%, the content of Na2SiF6 powder is 0-20wt%, the content of Si powder is 5-20wt%, the content of at least one of borax and B4C powder is 0.1-10wt%, and the content of HfB2 powder is 0.1-15wt%; B2, controlling the heating temperature and the heating time, the heating temperature is 850-1050℃, and the heating time is 2-8h, to obtain a molten salt non-electrolytic modified coating on the molybdenum or molybdenum alloy surface.

2. The method of claim 1, wherein the molten salt non-electrolytic modification coating of a molybdenum or molybdenum alloy surface is prepared by the steps of: Before the step B1, the method further comprises, B0, polishing the molybdenum or molybdenum alloy substrate by using sandpaper, then cleaning by using anhydrous ethanol, and then drying for standby.

3. The method of claim 1, wherein the molten salt non-electrolytic modification coating of a molybdenum or molybdenum alloy surface is prepared by the steps of: In the step B1, the thickness of the modified powder for the molybdenum or molybdenum alloy surface covering on the molybdenum or molybdenum alloy substrate is greater than or equal to 3mm.

4. The method of claim 1, wherein the molten salt non-electrolytic modification coating of a molybdenum or molybdenum alloy surface is prepared by the steps of: The preparation method of the modified powder for the molybdenum or molybdenum alloy surface comprises the following steps: S1. taking at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder for standby; S2. placing at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder in a ball mill for ball milling and mixing to obtain a mixed powder, the ball milling speed is 150-250 rpm, and the ball milling time is 2-3h; S3. placing the mixed powder in a drying machine to dry to obtain the modified powder for the molybdenum or molybdenum alloy surface.

5. The method of claim 4, wherein the molten salt non-electrolytic modification coating of a molybdenum or molybdenum alloy surface is prepared by the steps of: Before the step S1, the method further comprises, S0. grinding at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder by using a grinding bowl.

6. The method of claim 4, wherein the molten salt electrolysis-free modified coating of a molybdenum or molybdenum alloy surface is prepared by the steps of: In the step S1, the particle size of at least one of borax and B4C powder, NaCl-KCl-NaF powder, Na2SiF6 powder, Si powder, and HfB2 powder is 3-50 μm.

7. The method of claim 4, wherein the molten salt non-electrolytic modification coating of a molybdenum or molybdenum alloy surface is prepared by the steps of: In the step S2, the forward and reverse rotation is performed during the ball milling, and the forward and reverse rotation time is the same.

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