Preparation method and application of anti-adhesion chromizing powder

Abstract

The present invention discloses a preparation method of anti-adhesion chromium-permeated powder, which comprises the following steps: Step 1, preparing an aluminum-chromium precursor; Step 2, preparing alumina semi-coated chromium powder; Step 3, preparing anti-adhesion chromium-permeated powder. The present invention uses alumina semi-coated chromium powder instead of metal chromium powder to prepare anti-adhesion chromium-permeated powder. Through the semi-coating of chromium powder by alumina, the direct contact between chromium-permeated powder particles and between chromium-permeated powder particles and the substrate is avoided, thereby effectively preventing the sintering of chromium-permeated powder during the chromium permeation process and its adhesion behavior on the stainless steel surface. After the chromium permeation treatment, the chromium-permeated powder has good fluidity, and the stainless steel substrate can be easily taken out from the chromium permeation container, greatly reducing the labor intensity on the premise of ensuring the chromium permeation quality. Moreover, the preparation method of the present invention is simple and low in cost, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of stainless steel surface hardening coatings, and particularly relates to a preparation method and application of anti-bonding chromiumizing powder. Background Art

[0002] Austenitic stainless steel has excellent corrosion resistance and is widely used in industries such as chemical engineering, marine, and petrochemical industries. However, the hardness of austenitic stainless steel is relatively low (200 - 250 HV), the surface is extremely soft, it is difficult to withstand frictional damage, and the anti-wear performance is poor, which restricts its application in a harsh frictional environment under special working conditions.

[0003] In order to overcome the non-wear-resistant characteristics of austenitic stainless steel, chromiumizing treatment is carried out on the surface of austenitic stainless steel by chemical heat treatment method to form a chromiumizing layer with a hardness above 1000 HV on its surface, which can greatly improve the wear resistance of the substrate. For example, a chromiumizing agent and its chromiumizing process disclosed in Chinese patent document CN107881462A use a chromium supply agent, an activator, an inert filler, and a foam inorganic material as the chromiumizing agent, and carry out chromiumizing treatment at a temperature of 850°C - 1250°C to form a corrosion-resistant and oxidation-resistant chromiumizing layer on the substrate surface. A solid powder method chromiumizing process and a chromiumizing agent formula disclosed in Chinese patent document CN107794494A use pure chromium powder, aluminum oxide, and ammonium chloride as the chromiumizing agent, and prepare a chromiumizing layer with a surface hardness of 1200 - 1500 HV at a temperature of 980 ± 10°C, meeting the long-term service performance of parts in the marine environment.

[0004] The general chemical reaction process of metal chromiumizing is: at high temperature, halides (ammonium iodide and / or ammonium chloride) react with metal Cr to generate chromium halide gas, so that active [Cr] reaches the surface of the metal to be chromiumized, forming a diffusion layer. To prevent metal Cr powder from sticking to the surface of metal parts, the traditional method is to add 30 - 55 wt% of filler (usually alumina) to the chromiumizing powder. However, it is found in actual production that when the chromiumizing temperature reaches above 1000°C and the chromiumizing time is above 10 h, the traditional method of directly adding filler cannot play a very effective anti-bonding role. Sintering, curing, and bonding will occur significantly between chromiumizing powder particles and between chromiumizing powder particles and the stainless steel substrate. A large number of chromiumizing powder particles will stick to the surface of the prepared product, and the chromiumizing powder will be severely hardened, making it extremely difficult to remove the parts after chromiumizing. Not only is the labor intensity high, but also the surface quality of the parts is easily damaged, and there is an urgent need to improve the existing technology.

[0005] Therefore, a preparation method and application of anti-bonding chromiumizing powder are needed. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of anti-bonding chromium-permeated powder in view of the deficiencies of the above-mentioned prior art. This method uses alumina to semi-coat chromium powder instead of metallic chromium powder. Alumina forms a semi-coating effect outside the chromium particles, which not only ensures the reaction between the halide and chromium, but also avoids the direct contact between chromium-permeated powder particles and between chromium-permeated powder particles and the stainless steel substrate. Therefore, it effectively prevents the sintering of chromium-permeated powder during the chromium permeation process and its bonding behavior on the stainless steel surface. After the chromium permeation treatment, the chromium-permeated powder has good fluidity, and the substrate can be easily taken out from the chromium permeation container, greatly reducing the labor intensity on the premise of ensuring the chromium permeation quality. Moreover, the preparation method of the present invention is simple and has low cost, and is suitable for large-scale industrial production.

[0007] To solve the above technical problem, the technical solution adopted by the present invention is: a preparation method of anti-bonding chromium-permeated powder, characterized in that the method comprises the following steps:

[0008] Step 1, prepare an aluminum-chromium precursor: mix alumina powder and chromium powder with a mass ratio of 15-25:75-85, compact them, and then put them into a vacuum furnace filled with Ar gas for calcination to obtain an aluminum-chromium precursor;

[0009] Step 2, prepare alumina semi-coated chromium powder: successively crush and screen the aluminum-chromium precursor obtained in Step 1 to obtain alumina semi-coated chromium powder;

[0010] Step 3, prepare anti-bonding chromium-permeated powder: put the alumina semi-coated chromium powder, alumina powder and halide catalyst obtained in Step 2 into a mixer for mixing to obtain anti-bonding chromium-permeated powder; the mass ratio of the alumina semi-coated chromium powder, alumina powder and halide catalyst in the anti-bonding chromium-permeated powder is 63-74:25-35:1-3.

[0011] In the present invention, alumina powder and chromium powder are first mixed and their ratio is controlled to ensure sufficient contact between alumina particles and metal chromium particles, initially forming a semi-coated structure with a good semi-coating effect. If the alumina content is less than 15%, the coating effect will be poor, and there will still be chromium powder particles that are not coated, resulting in bonding during the high-temperature chromizing reaction at 1000°C for 10 hours or more. If the alumina content is higher than 25%, the coating will be too strict, and some chromium powder will be completely coated, causing the halide to be unable to contact the chromium powder particles during the chromizing process, unable to form sufficient chromium halide reaction gas, and resulting in insufficient chromizing reaction and affecting the preparation of the chromized layer on the metal surface. Through vacuum calcination, melting and sintering reactions occur between alumina particles and chromium particles, and smaller alumina particles and larger chromium particles can form a "connected" mixed powder. After pulverization and sieving, a state where alumina semi-coats the surface of chromium particles can be formed, that is, alumina semi-coated chromium powder. By mixing the alumina semi-coated chromium powder, alumina powder, and halide catalyst in a mixer, anti-bonding chromizing powder is obtained. The chromium content in the obtained chromizing powder should reach 50 - 60 wt%. When it is lower than 50 wt%, the chromizing powder cannot provide sufficient chromium source for the part surface. When it is higher than 60 wt%, it will lead to insufficient filler (i.e., alumina), serious powder bonding, and poor surface quality of the prepared chromized layer. Similarly, the content of the halide catalyst is generally 1 - 3 wt%. When it is lower than 1 wt%, the chromizing reaction will be insufficient. When it is higher than 3 wt%, the reaction will be too violent, both of which will affect the performance quality of the chromized layer. Therefore, the chromium content in the anti-bonding chromizing powder prepared by the present invention is 50 - 60 wt%, and the content of the halide catalyst is 1 - 3 wt%. According to the chromium content in the prepared alumina semi-coated chromium powder being 75 - 85 wt%. Therefore, the mass ratio of the alumina semi-coated chromium powder, alumina powder, and halide catalyst can be calculated to be 63 - 74:25 - 35:1 - 3.

[0012] In the above method for preparing anti-bonding chromizing powder, it is characterized in that in step one, the particle size of the alumina powder is 150 mesh - 250 mesh, the mass purity of the alumina powder is not less than 99.99%, the particle size of the chromium powder is 30 mesh - 200 mesh, and the mass purity of the chromium powder is not less than 99.99%. The present invention controls the particle size of the alumina powder and the chromium powder, enables the alumina powder and the chromium powder to cooperate with each other to form alumina semi-coated chromium powder, and ensures the purity of the obtained anti-bonding chromizing powder and improves the performance by controlling the particle size of the alumina powder and the mass purity of the chromium powder.

[0013] Preferably, the particle size of the alumina powder is 200 mesh, and the particle size of the chromium powder is 80 mesh.

[0014] The above-mentioned method for preparing anti-adhesion chromium-permeated powder is characterized in that in step one, the mass purity of the Ar gas is not less than 99.999%, the flow rate of the Ar gas is 10 sccm to 50 sccm, the pressure in the vacuum furnace is 200 Pa to 1000 Pa, the calcination temperature is 1000 °C to 1200 °C, and the time is 5 h to 10 h. The present invention prevents the introduction of impurities by controlling the mass purity of the Ar gas, provides a suitable external environment to protect the calcination process by controlling the flow rate of the Ar gas and the pressure in the vacuum furnace, and ensures the connection between the alumina powder and the chromium powder by controlling the calcination temperature and time.

[0015] Preferably, the flow rate of the Ar is 30 sccm, the pressure in the vacuum furnace is 200 Pa, the temperature in the vacuum furnace is 1100 °C, and preferably, the high-temperature calcination time is 7 h.

[0016] The above-mentioned method for preparing anti-adhesion chromium-permeated powder is characterized in that the particle size of the alumina semi-coated chromium powder is 80 mesh to 200 mesh. The present invention ensures the subsequent full and uniform mixing of the alumina semi-coated chromium powder, the alumina powder and the halide catalyst by controlling the particle size of the alumina semi-coated chromium powder, so that the prepared anti-adhesion chromium-permeated powder has the best performance.

[0017] Preferably, the particle size of the alumina semi-coated chromium powder is 100 mesh.

[0018] The above-mentioned method for preparing anti-adhesion chromium-permeated powder is characterized in that in step three, the halide catalyst is ammonium chloride and / or ammonium iodide, and the mixing time is 30 min to 120 min. The present invention ensures the full progress of the mixing by controlling the mixing time.

[0019] Preferably, the mixing time is 80 min.

[0020] The above-mentioned method for preparing anti-adhesion chromium-permeated powder is characterized in that in step three, the particle size of the anti-adhesion chromium-permeated powder is 80 mesh to 200 mesh. The present invention ensures the use effect and has the best chromium-permeation performance by controlling the anti-adhesion chromium-permeated powder.

[0021] Preferably, the particle size of the alumina semi-coated chromium powder is 100 mesh.

[0022] In addition, the present invention also provides the application of the anti-adhesion chromium-permeated powder, which is characterized by including the following steps: placing a clean austenitic stainless steel substrate in a chromium-permeation container, then filling it with the anti-adhesion chromium-permeated powder, sealing it with water glass, and then placing it in a heat treatment furnace for heat treatment to prepare a chromium-permeated layer on the surface of the austenitic stainless steel.

[0023] The summary of the chromizing reaction process of the present invention is as follows: at high temperature, the halide catalyst decomposes and reacts with metallic chromium to form chromium halide gas. The chromium halide gas then reacts on the metal surface to form a high-concentration chromium layer on the metal surface. Under high-temperature conditions, an inward diffusion reaction occurs, and finally a chromized layer is formed on the metal surface. In the present invention, the surface of the clean austenitic stainless steel substrate is free of oil stains, water stains, and dirt.

[0024] For the above application, it is characterized in that the temperature of the heat treatment is 900°C to 1100°C, and the time is 10h to 50h. The present invention ensures the chromizing effect by controlling the temperature and time of the heat treatment.

[0025] Preferably, the temperature of the heat treatment is 1080°C, and the time of the heat treatment is 20h.

[0026] For the above application, it is characterized in that the austenitic stainless steel substrate is 316 stainless steel, 304 stainless steel, or 321 stainless steel. The present invention is applicable to chromizing of substrates made of various different materials.

[0027] For the above application, it is characterized in that the thickness of the chromized layer is 70μm to 150μm. The chromized layer obtained by the present invention is relatively thick and has an excellent chromizing effect.

[0028] Preferably, the thickness of the chromized layer is 110μm to 120μm.

[0029] The present invention has the following advantages compared with the prior art:

[0030] 1. The present invention uses alumina semi-coated chromium powder instead of metallic chromium powder. Alumina forms a semi-coated effect outside the chromium particles, which not only ensures the reaction between the halide and chromium but also avoids the direct contact between the chromizing powder particles and between the chromizing powder particles and the stainless steel substrate. Thus, it effectively prevents the sintering of the chromizing powder and its adhesion behavior on the stainless steel surface during the chromizing process. After the chromizing treatment, the chromizing powder has good fluidity, and the stainless steel substrate can be easily taken out of the chromizing container. On the premise of ensuring the chromizing quality, the labor intensity is greatly reduced. Moreover, the preparation method of the present invention is simple and the cost is low, which is suitable for large-scale industrial production.

[0031] 2. The present invention controls the ratio of alumina powder and chromium powder, making the finally prepared chromizing powder not easily adhere. Because adhesion occurs between chromium powder particles or between chromium powder particles and the metal surface, while in the chromizing powder prepared by the present invention, the particles are separated by inert alumina small particles, avoiding their direct contact. At the same time, the semi-coated effect does not completely wrap the chromium powder particles, leaving space, enabling the chromium powder particles to contact and react with the halide catalyst, form a chromium halide atmosphere, transfer to the metal surface, and undergo a chromizing reaction.

[0032] 3. The present invention uses alumina semi-coated chromium powder instead of metallic chromium powder to prepare anti-bonding chromizing powder, avoiding the bonding of powder during high-temperature chromizing treatment (1000 °C and above), reducing the labor intensity of powder discharging during the chromizing of large products, reducing the post-treatment process, and improving the surface quality of the product.

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is a schematic structural diagram of the anti-bonding chromizing powder of the present invention.

[0035] Figure 2 is an optical microscope image of the cross-section of the chromized layer prepared in Example 1 of the present invention.

[0036] Figure 3 is a schematic diagram of the elemental analysis position on the surface of the chromized layer prepared in Example 1 of the present invention.

[0037] Figure 4 is a diagram of the elemental analysis results on the surface of the chromized layer prepared in Example 1 of the present invention.

[0038] Figure 5 is a schematic diagram of austenitic stainless steel and anti-bonding chromizing powder after heat treatment in Example 1 of the present invention.

[0039] Figure 6 is a schematic diagram of austenitic stainless steel and chromizing powder after heat treatment in Comparative Example 3 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] Figure 1 is a schematic structural diagram of the anti-bonding chromizing powder of the present invention. It can be seen from Figure 1 that the spherical shape is chromium particles, and the outer part of the chromium particles is semi-coated with strip-shaped alumina particles, and the alumina particles form a semi-coated effect outside the chromium particles.

[0041] Example 1

[0042] This example includes the following steps:

[0043] Step 1. Prepare an aluminum-chromium precursor: Mix alumina powder with a particle size of 200 mesh and a mass purity of not less than 99.99% and chromium powder with a particle size of 80 mesh and a mass purity of not less than 99.99% in a mass ratio of 25:75, compact them, and then put them into a vacuum furnace filled with Ar gas with a mass purity of not less than 99.999% for calcination to obtain an aluminum-chromium precursor; the flow rate of the Ar gas is 30 sccm, the pressure in the vacuum furnace is 200 Pa; the calcination temperature is 1100 °C, and the time is 7 h;

[0044] Step 2: Prepare alumina semi-coated chromium powder: Crush and sieve the aluminum-chromium precursor obtained in Step 1 to obtain alumina semi-coated chromium powder; the particle size of the alumina semi-coated chromium powder is 100 mesh;

[0045] Step 3: Prepare anti-bonding chromium powder for aluminizing: Place alumina semi-coated chromium powder, alumina powder, and halide catalyst with a mass ratio of 74:25:1 in a mixer for mixing to obtain anti-bonding chromium powder for aluminizing; the halide catalyst is ammonium chloride and ammonium iodide with a mass ratio of 1:1, and the mixing time is 80 min; the particle size of the anti-bonding chromium powder for aluminizing is 100 mesh;

[0046] Step 4: Place a clean 316 austenitic stainless steel substrate in an aluminizing container, then bury it with anti-bonding chromium powder for aluminizing, seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare an aluminized layer on the surface of the austenitic stainless steel; the temperature of the heat treatment is 1080 °C and the time is 20 h.

[0047] After testing, the average thickness of the aluminized layer prepared in this example is 113 μm.

[0048] Figure 2 is an optical microscope image of the cross-section of the aluminized layer prepared in this example. From Figure 2 it can be seen that the aluminized layer prepared in this example is well-layered, the interface is continuous, and the average thickness reaches 113 μm.

[0049] Figure 3 is a schematic diagram of the element analysis position on the surface of the aluminized layer prepared in this example. Figure 4 is the element analysis result image of the surface of the aluminized layer prepared in this example. Figure 3 is the element analysis position. Figure 4 is the analysis result. From Figure 3 and Figure 4 it can be seen that the chromium element content in the aluminized layer prepared in this example is about 86 wt%.

[0050] Figure 5 is a schematic diagram of the austenitic stainless steel and anti-bonding chromium powder for aluminizing after heat treatment in this example. From Figure 5 it can be seen that the anti-bonding chromium powder for aluminizing after heat treatment in this example is relatively loose, without caking, the bonding situation of the chromium powder for aluminizing is significantly improved, the surface of the austenitic stainless steel part is smooth, and the chromium powder for aluminizing is easy to remove.

[0051] Comparative Example 1

[0052] This comparative example includes the following steps:

[0053] Step 1. Preparation of aluminum-chromium precursor: Mix alumina powder with a particle size of 200 mesh and a mass purity of not less than 99.99% and chromium powder with a particle size of 80 mesh and a mass purity of not less than 99.99% at a mass ratio of 10:90, then compact the mixture, and then place it in a vacuum furnace filled with Ar gas with a mass purity of not less than 99.999% for calcination to obtain the aluminum-chromium precursor; the flow rate of the Ar gas is 30 sccm, and the pressure in the vacuum furnace is 200 Pa; the calcination temperature is 1100 °C and the time is 7 h;

[0054] Step 2. Preparation of alumina-coated chromium powder: Crush and screen the aluminum-chromium precursor obtained in Step 1 to obtain alumina-coated chromium powder; the particle size of the alumina-coated chromium powder is 100 mesh;

[0055] Step 3. Preparation of chromizing powder: Place alumina-coated chromium powder, alumina powder, and halide catalyst at a mass ratio of 74:25:1 in a mixer for mixing to obtain chromizing powder; the halide catalyst is ammonium chloride and ammonium iodide at a mass ratio of 1:1, and the mixing time is 80 min; the particle size of the chromizing powder is 100 mesh;

[0056] Step 4. Place a clean 316 austenitic stainless steel substrate in a chromizing container, then bury it with chromizing powder, seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare a chromized layer on the surface of the austenitic stainless steel; the heat treatment temperature is 1080 °C and the time is 20 h.

[0057] After testing, the microstructural detection of the chromizing powder prepared in this comparative example was carried out by an electron microscope. The results showed that the prepared chromizing powder failed to form alumina semi-coated metal chromium particles, and after the chromized layer was prepared, the chromizing powder adhered seriously, a large amount of it adhered to the surface of the parts, it was difficult to clean, and the particles had high hardness and high labor intensity for powder discharging.

[0058] Comparative Example 2

[0059] This comparative example includes the following steps:

[0060] Step 1. Preparation of aluminum-chromium precursor: Mix alumina powder with a particle size of 200 mesh and a mass purity of not less than 99.99% and chromium powder with a particle size of 80 mesh and a mass purity of not less than 99.99% at a mass ratio of 30:70, then compact the mixture, and then place it in a vacuum furnace filled with Ar gas with a mass purity of not less than 99.999% for calcination to obtain the aluminum-chromium precursor; the flow rate of the Ar gas is 30 sccm, and the pressure in the vacuum furnace is 200 Pa; the calcination temperature is 1100 °C and the time is 7 h;

[0061] Step 2: Prepare alumina-coated chromium powder: Crush and sieve the aluminum-chromium precursor obtained in Step 1 to obtain alumina-coated chromium powder; the particle size of the alumina-coated chromium powder is 100 mesh;

[0062] Step 3: Prepare chromium-permeated powder: Place alumina-coated chromium powder, alumina powder, and halide catalyst with a mass ratio of 74:25:1 in a mixer for mixing to obtain chromium-permeated powder; the halide catalyst is ammonium chloride and ammonium iodide with a mass ratio of 1:1, and the mixing time is 80 min; the particle size of the chromium-permeated powder is 100 mesh;

[0063] Step 4: Place a clean 316 austenitic stainless steel substrate in a chromium-permeation container, then bury it with chromium-permeated powder, seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare a chromium-permeated layer on the surface of the austenitic stainless steel; the temperature of the heat treatment is 1080 °C and the time is 20 h.

[0064] After testing, the microstructure of the chromium-permeated powder prepared in this comparative example was detected by an electron microscope. The results showed that the prepared chromium-permeated powder failed to form particles with alumina semi-coated metal chromium, and after preparing the chromium-permeated layer, the chromium-permeated powder adhered seriously, a large amount of it adhered to the surface of the parts, it was difficult to clean, and the particles had high hardness and high labor intensity for powder discharging.

[0065] Comparative Example 3

[0066] This comparative example includes the following steps:

[0067] Step 1: Place a clean 316 austenitic stainless steel substrate in a chromium-permeation container, then bury it with chromium-permeated powder, seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare a chromium-permeated layer on the surface of the austenitic stainless steel; the temperature of the heat treatment is 1080 °C and the time is 20 h; the chromium-permeated powder is the chromium-permeating agent disclosed in Application No. 201610876998.0.

[0068] Figure 6 is a schematic diagram of the austenitic stainless steel and chromium-permeated powder after heat treatment in this comparative example. From Figure 6 it can be seen that the anti-adhesive chromium-permeated powder after heat treatment in this comparative example adhered seriously, a large amount of it adhered to the surface of the parts, it was difficult to clean, and the particles had high hardness and high labor intensity for powder discharging.

[0069] Example 2

[0070] This example includes the following steps:

[0071] Step 1. Preparation of aluminum-chromium precursor: Mix alumina powder with a particle size of 200 mesh and a mass purity of not less than 99.99% and chromium powder with a particle size of 30 mesh and a mass purity of not less than 99.99% at a mass ratio of 20:80, then compact the mixture, and then place it in a vacuum furnace filled with Ar gas with a mass purity of not less than 99.999% for calcination to obtain the aluminum-chromium precursor; the flow rate of the Ar gas is 10 sccm, and the pressure in the vacuum furnace is 500 Pa; the calcination temperature is 1000 °C and the time is 5 h;

[0072] Step 2. Preparation of alumina semi-coated chromium powder: Crush and screen the aluminum-chromium precursor obtained in Step 1 to obtain alumina semi-coated chromium powder; the particle size of the alumina semi-coated chromium powder is 200 mesh;

[0073] Step 3. Preparation of anti-bonding chromizing powder: Mix alumina semi-coated chromium powder, alumina powder and halide catalyst at a mass ratio of 63:35:2 in a mixer to obtain anti-bonding chromizing powder; the halide catalyst is ammonium chloride and ammonium iodide at a mass ratio of 1:1, and the mixing time is 120 min; the particle size of the anti-bonding chromizing powder is 200 mesh.

[0074] Step 4. Place a clean 321 austenitic stainless steel substrate in a chromizing container, then bury it with anti-bonding chromizing powder and seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare a chromized layer on the surface of the austenitic stainless steel; the heat treatment temperature is 900 °C and the time is 50 h.

[0075] After testing, the average thickness of the chromized layer prepared in this example is 70 μm, the chromized layer is well-defined and the interface is continuous, the chromium element content in the coating is more than 80 wt%, the anti-bonding chromizing powder after heat treatment in this example is relatively loose and there is no caking, the bonding situation of the chromizing powder is significantly improved, the surface of the austenitic stainless steel part is smooth, and the chromizing powder is easy to remove.

[0076] Example 3

[0077] This example includes the following steps:

[0078] Step 1. Preparation of aluminum-chromium precursor: Mix alumina powder with a particle size of 200 mesh and a mass purity of not less than 99.99% and chromium powder with a particle size of 200 mesh and a mass purity of not less than 99.99% at a mass ratio of 15:85, then compact the mixture, and then place it in a vacuum furnace filled with Ar gas with a mass purity of not less than 99.999% for calcination to obtain the aluminum-chromium precursor; the flow rate of the Ar gas is 50 sccm, and the pressure in the vacuum furnace is 1000 Pa; the calcination temperature is 1200 °C and the time is 10 h;

[0079] Step 2: Prepare alumina semi-coated chromium powder: Crush and sieve the aluminum-chromium precursor obtained in Step 1 to obtain alumina semi-coated chromium powder; the particle size of the alumina semi-coated chromium powder is 80 mesh.

[0080] Step 3: Prepare anti-bonding chromium powder for aluminizing: Mix alumina semi-coated chromium powder, alumina powder, and halide catalyst with a mass ratio of 70:27:3 in a mixer to obtain anti-bonding chromium powder for aluminizing; the halide catalyst is ammonium chloride, and the mixing time is 30 min; the particle size of the anti-bonding chromium powder for aluminizing is 80 mesh.

[0081] Step 4: Place a clean 304 austenitic stainless steel substrate in an aluminizing container, then bury it with anti-bonding chromium powder for aluminizing, seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare an aluminized layer on the surface of the austenitic stainless steel; the temperature of the heat treatment is 1100 °C, and the time is 10 h.

[0082] After testing, the average thickness of the aluminized layer prepared in this example is 150 μm, the layers of the aluminized layer are distinct and the interface is continuous, the chromium element content in the coating is more than 80 wt%, the anti-bonding chromium powder for aluminizing after heat treatment in this example is relatively loose and does not agglomerate, the bonding situation of the chromium powder for aluminizing is significantly improved, the surface of the austenitic stainless steel part is smooth, and the chromium powder for aluminizing is easy to remove.

[0083] The above is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of anti - adhesion chromium - penetrated powder, characterized in that, the method comprises the following steps: Step 1: Prepare an aluminum - chromium precursor: Mix alumina powder and chromium powder with a mass ratio of 15 - 25:75 - 85, compact them, and then put them into a vacuum furnace filled with Ar gas for calcination to obtain the aluminum - chromium precursor; the particle size of the alumina powder is 150 mesh - 250 mesh, the mass purity of the alumina powder is not less than 99.99%, the particle size of the chromium powder is 30 mesh - 200 mesh, the mass purity of the chromium powder is not less than 99.99%; the mass purity of the Ar gas is not less than 99.999%, the flow rate of the Ar gas is 10 sccm - 50 sccm, the pressure in the vacuum furnace is 200 Pa - 1000 Pa, the calcination temperature is 1000 °C - 1200 °C, and the time is 5 h - 10 h; Step 2: Prepare alumina semi - coated chromium powder: Crush and screen the aluminum - chromium precursor obtained in Step 1 to obtain alumina semi - coated chromium powder; the particle size of the alumina semi - coated chromium powder is 80 mesh - 200 mesh; Step 3: Prepare anti - adhesion chromium - penetrated powder: Place the alumina semi - coated chromium powder, alumina powder and halide catalyst obtained in Step 2 in a mixer for mixing to obtain anti - adhesion chromium - penetrated powder; the mass ratio of the alumina semi - coated chromium powder, alumina powder and halide catalyst in the anti - adhesion chromium - penetrated powder is 63 - 74:25 - 35:1 - 3; the halide catalyst is ammonium chloride and / or ammonium iodide, the mixing time is 30 min - 120 min; the particle size of the anti - adhesion chromium - penetrated powder is 80 mesh - 200 mesh.

2. The application of the anti - adhesion chromium - penetrated powder prepared as claimed in claim 1, characterized in that, it comprises the following steps: Place a clean austenitic stainless - steel substrate in a chromium - penetration container, then fill it with anti - adhesion chromium - penetrated powder, seal it with water glass, and then place it in a heat treatment furnace for heat treatment to prepare a chromium - penetrated layer on the surface of the austenitic stainless steel.

3. According to the application described in claim 2, characterized in that, the temperature of the heat treatment is 900 °C - 1100 °C, and the time is 10 h - 50 h.

4. According to the application described in claim 2, characterized in that, the austenitic stainless - steel substrate is 316 stainless steel, 304 stainless steel or 321 stainless steel.

5. According to the application described in claim 2, characterized in that, the thickness of the chromium - penetrated layer is 70 μm - 150 μm.

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