High temperature oxidation resistant heat-resistant steel and its preparation method and application

Abstract

The present invention discloses a high-temperature oxidation resistant heat-resistant steel and its preparation method and application. The high-temperature oxidation resistant heat-resistant steel comprises a heat-resistant steel substrate and a protective coating located on the surface of the heat-resistant steel substrate. The protective coating is composed of intermetallic compounds, which sequentially include (Fe, Ni) Al phase layer, FeAl3 (Fe4Al 13 ) phase layer and Fe2Al5(FeAl 2.8 ) phase layer. This high-temperature oxidation-resistant heat-resistant steel is obtained by coating a pure aluminum layer on the surface of a heat-resistant steel substrate and then heat-treating it. The preparation process of this protective coating is highly efficient, has strong positioning capabilities for the protection unit, and is environmentally friendly. The prepared coating can effectively protect the base heat-resistant steel, greatly improving the service life of the heat-resistant steel in hot corrosive environments and significantly reducing the overall material cost.

Description

Technical Field

[0001] The present invention relates to the field of metal material protection, and in particular to a high-temperature oxidation-resistant heat-resistant steel and a preparation method and application thereof. Background Art

[0002] As an indispensable material in high-temperature working environments, the development and application of heat-resistant steel plays a vital role in key areas such as energy and power machinery. When faced with different temperatures, environmental stresses, and oxidizing atmospheres, the selection of heat-resistant steel needs to be highly targeted. This type of steel not only needs to withstand the test of high temperature and high pressure, but also needs to resist long-term high-temperature steam corrosion. Its core performance requirements include stable mechanical properties and long-lasting resistance to high-temperature oxidation. However, the heat-resistant steel currently on the market has deficiencies in corrosion resistance and wear resistance, which not only shortens its service life and increases the production costs of enterprises, but also may require frequent replacement during long-term service, thus affecting the continuity and efficiency of industrial production.

[0003] Heat-resistant steel typically consists of elements such as chromium, nickel, and iron, forming an alloy structure that offers high-temperature stability. While these base materials possess a certain degree of high-temperature resistance, existing heat-resistant steels face the challenge of not fully meeting the higher performance requirements of modern industry, driven by the ever-increasing demands of modern industry. In particular, the steel's oxidation resistance and thermal corrosion resistance are key factors limiting its application in high-temperature oxidizing environments, leading to potential risks in the production process and adding additional costs.

[0004] Traditional solutions to these technical challenges often focus on improving steel's chemical composition to enhance its performance. However, this approach is limited in an era of increasingly stringent cost controls and environmental requirements. Therefore, the search for more efficient and environmentally friendly protection measures has become a key focus of the industry.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a high-temperature oxidation-resistant heat-resistant steel and a preparation method and application thereof, so as to improve the above-mentioned technical problems.

[0007] The present invention is achieved in that:

[0008] In the first aspect, the present invention provides a high temperature oxidation resistant heat-resistant steel, which comprises a heat-resistant steel substrate and a protective coating located on the surface of the heat-resistant steel substrate, wherein the protective coating is composed of an intermetallic compound, which comprises, from the inside to the outside, a (Fe, Ni) Al phase layer, a FeAl3 (Fe4Al 13 ) phase layer and Fe2Al5(FeAl 2.8 )Physical phase layer.

[0009] In an optional embodiment, the thickness of the protective coating is 0.2 mm to 1 mm.

[0010] In an optional embodiment, the heat-resistant steel substrate is chromium-nickel heat-resistant steel.

[0011] In an optional embodiment, the chromium-nickel heat-resistant steel is high-Cr low-Ni heat-resistant steel or high-Cr high-Ni heat-resistant steel, and the chemical composition of the high-Cr low-Ni heat-resistant steel is as follows by weight: Cr 15.0%~30.0%, Ni 4.0%~10.0%, Mn 1.0%~1.1%, Si 1.4%~1.5%, C 0.3%~0.4%, V 0.12%~0.13%, and the remainder is iron and inevitable trace elements; the chemical composition of the high-Cr high-Ni heat-resistant steel is as follows by weight: Cr 15.0%~30.0%, Ni 10.0%~25.0%, Mn 0.5%~1.0%, Si 0.9%~1.0%, C 0.3%~0.4%, N0.16%~0.17%, and the remainder is iron and inevitable trace elements.

[0012] In a second aspect, the present invention provides a method for preparing high-temperature oxidation-resistant heat-resistant steel as described in any one of the aforementioned embodiments, comprising: coating a pure aluminum layer on the surface of the heat-resistant steel substrate, and then performing heat treatment.

[0013] In an optional embodiment, the thickness of the coated pure aluminum layer is 100 μm to 500 μm;

[0014] In an optional embodiment, the pure aluminum layer is formed by arc spraying;

[0015] In an optional embodiment, the surface of the heat-resistant steel substrate is sandblasted before coating.

[0016] In an optional embodiment, the heat treatment includes a first preheat treatment, a second preheat treatment and a diffusion treatment, the temperature of the first preheat treatment is 450°C to 550°C, the temperature of the second preheat treatment is 650°C to 670°C, and the temperature of the diffusion treatment is 700°C to 900°C.

[0017] In an optional embodiment, the time for the first preheating treatment is 30 minutes to 60 minutes, the time for the second preheating treatment is 30 minutes to 60 minutes, and the time for the diffusion treatment is 1 hour to 10 hours.

[0018] In a third aspect, the present invention provides use of the high-temperature oxidation-resistant heat-resistant steel as described in any one of the aforementioned embodiments in the preparation of high-temperature workpieces.

[0019] In an optional embodiment, the high-temperature workpiece is an internal lining plate of a steam turbine unit, a discharge grate plate of a cement plant, or a hanging plate of a supercritical generator unit.

[0020] The present invention has the following beneficial effects: by forming a protective coating with multiple phase layers on the surface of a heat-resistant steel substrate, it can achieve multiple protective effects on the heat-resistant steel substrate, greatly improving the heat-resistant steel's high-temperature thermal corrosion and oxidation resistance. The intermetallic compound formed between the coating and the heat-resistant substrate provides excellent bonding between the two. After multiple high-temperature cyclic oxidation cycles, the morphology is intact and has excellent protective capabilities. As a result, this heat-resistant steel has excellent application prospects in industrial production sites with high demand for heat-resistant steel, such as cement plants, waste treatment plants, and internal combustion engine units. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 Electron microscope images of the protective coating of the heat-resistant steel samples of Example 1 and Example 10 under EBSD;

[0023] Figure 2 The gradient hardness of the protective coating of the heat-resistant steel samples of Example 1 and Example 10, wherein (a) is the hardness gradient of the protective coating of the low-Ni sample of the heat-resistant steel of Example 1; (b) is the hardness gradient of the alloy layer of the high-Ni sample of the heat-resistant steel of Example 2;

[0024] Figure 3 SEM images of the protective coatings of the heat-resistant steel samples of Examples 1 and 10; wherein (a) and (b) are the protective coatings of the heat-resistant steel of Example 1, and (c) and (d) are the protective coatings of the heat-resistant steel of Example 1;

[0025] Figure 4 The graphs show the results of 200h cyclic oxidation of the heat-resistant steel of Example 1 and the heat-resistant steel of Comparative Example 1; wherein (a) is the result of Example 1, and (b) is the result of Comparative Example 1;

[0026] Figure 5 These are microscopic morphologies of the heat-resistant steel of Example 1 and the heat-resistant steel of Comparative Example 1 after 200 hours of cyclic oxidation, wherein (a) is the result of Example 1 and (b) is the result of Comparative Example 1. DETAILED DESCRIPTION

[0027] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0028] The following is a detailed description of a high-temperature oxidation-resistant heat-resistant steel disclosed in the present invention, as well as its preparation method and application.

[0029] Some embodiments of the present invention provide a high temperature oxidation resistant heat-resistant steel, which includes a heat-resistant steel substrate and a protective coating located on the surface of the heat-resistant steel substrate, wherein the protective coating is composed of intermetallic compounds, which sequentially include, from the inside to the outside, a (Fe, Ni) Al phase layer, a FeAl3 (Fe4Al 13 ) phase layer and Fe2Al5(FeAl 2.8 )Physical phase layer.

[0030] The use of protective coatings to improve the oxidation resistance and thermal corrosion resistance of heat-resistant steel not only has a high efficiency and is environmentally friendly, but also has a strong positioning capability for the protected unit. This extends the service life of heat-resistant steel while reducing costs. Based on the idea of ​​protective coatings, the inventors creatively proposed a protective coating composed of multiple intermetallic compounds formed by heat treatment to protect heat-resistant steel, including (Fe, Ni) Al phase layer, FeAl3 (Fe4Al 13 ) phase layer and Fe2Al5(FeAl 2.8 The multi-layered structure, composed of various phase layers, provides multiple protective effects for heat-resistant steel, and also exhibits excellent bonding between the protective coating and the heat-resistant steel substrate. Specifically, the multi-layered protective layer, formed by various aluminum intermetallic compounds, has a denser microstructure, thereby reducing direct corrosion from external media (such as oxygen). Furthermore, the combination with Fe and Ni not only enhances its antioxidant capacity but also improves its thermal stability.

[0031] In some embodiments, in order to achieve better protection effect, the protective coating needs to have a certain thickness. The protective coating also needs to avoid being too thick to avoid the inability to form complete intermetallic compounds through heat treatment and affecting the protection effect. Therefore, in some embodiments, the thickness of the protective coating can be selected to be 0.2mm~1mm, for example, 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm or 1mm, etc., or between any two of the above thicknesses.

[0032] Furthermore, in order to meet the basic requirements of heat resistance and mechanical properties and to be able to form the protective coating in the above embodiments by diffusion through heat treatment, in some embodiments, the heat-resistant steel substrate is chromium-nickel heat-resistant steel.

[0033] For reference, chromium-nickel heat-resistant steel is high Cr low Ni heat-resistant steel or high Cr high Ni heat-resistant steel. The chemical composition of high Cr low Ni heat-resistant steel is as follows by weight: Cr 15.0%~30.0%, Ni 4.0%~10.0%, Mn 1.0%~1.1%, Si 1.4%~1.5%, C 0.3%~0.4%, V 0.12%~0.13%, and the balance is iron and inevitable trace elements; the chemical composition of high Cr high Ni heat-resistant steel is as follows by weight: Cr 15.0%~30.0%, Ni 10.0%~25.0%, Mn 0.5%~1.0%, Si 0.9%~1.0%, C 0.3%~0.4%, N 0.16%~0.17%, and the balance is iron and inevitable trace elements.

[0034] Furthermore, some embodiments of the present invention also provide a method for preparing high-temperature oxidation-resistant heat-resistant steel in any of the aforementioned embodiments, which comprises: coating a pure aluminum layer on the surface of a heat-resistant steel substrate, and then performing heat treatment.

[0035] Specifically, coating the pure aluminum layer on the surface of a heat-resistant steel substrate involves sandblasting the surface of the heat-resistant steel substrate before applying the pure aluminum layer. Sandblasting removes impurities, oxide layers, and stains on the surface of the material, thereby improving the bonding strength between the coating and the substrate. It also facilitates thermal diffusion of the pure aluminum layer during subsequent heat treatment to form a diffusion layer of intermetallic compounds.

[0036] Among them, in some embodiments, the thickness of the coated pure aluminum layer is 100μm to 500μm, for example; if the thickness of the coated pure aluminum layer is too small, it cannot effectively protect the heat-resistant steel, and may be completely consumed during the heating stage, resulting in poor diffusion effect; and if the coated pure aluminum layer is too thick, the heat diffusion cannot proceed smoothly, resulting in the falling off of the aluminum layer, which in turn reduces the anti-oxidation and thermal corrosion resistance.

[0037] Illustratively, the chemical composition of the pure aluminum layer in the embodiment of the present invention is 99.9% by weight of Al, with the remainder being unavoidable trace elements.

[0038] For reference, the pure aluminum layer is formed by arc spraying, where pure aluminum wire can be used as the raw material. This spraying method is highly efficient and simple to process, achieving high efficiency, pollution-free coating, and good coating bonding. Of course, other embodiments can also use chemical vapor deposition, physical vapor deposition, magnetron sputtering, electroplating, and other methods to apply the pure aluminum layer.

[0039] Furthermore, in order to fully react the pure aluminum layer, a phase layer with (Fe, Ni)Al, FeAl3(Fe4Al 13 ) phase layer and Fe2Al5(FeAl 2.8 ) The multi-layer diffusion layer structure of the physical layer, in some embodiments, the heat treatment includes a first preheating treatment, a second preheating treatment and a diffusion treatment. The temperature of the first preheating treatment is 450℃~550℃, so that the coating and the base heat-resistant steel are evenly heated; the temperature of the second preheating treatment is 650℃~670℃, reaching the melting point of the pure aluminum layer to ensure that the aluminum has good fluidity; the temperature of the diffusion treatment is 700℃~900℃. If the temperature is directly raised to the diffusion treatment temperature, it may cause uneven melting and diffusion in different areas of the aluminum layer, and the rapid temperature change and local transition melting may cause pores, shrinkage holes or cracks, etc., and it is impossible to achieve effective interface uniform diffusion. Therefore, it is necessary to perform a preheating treatment between the diffusion treatments. If the temperature is directly raised to the melting temperature of the pure aluminum layer, there will be a difference in the heating rate between the heat-resistant steel substrate and the pure aluminum layer, which will affect the bonding performance of the pure aluminum layer and the heat-resistant steel substrate, and thus affect the interface reaction effect of thermal diffusion. Therefore, the first preheating treatment is performed to allow the substrate and the pure aluminum layer to reach a certain temperature and then the second preheating treatment is performed to melt the pure aluminum layer to increase the fluidity of the aluminum liquid, and then the temperature is continued to be raised to the diffusion temperature for diffusion treatment.

[0040] For reference, the time for the first preheat treatment is 30min to 60min, such as 30min, 35min, 40min, 45min or 50min, etc., the time for the second preheat treatment is 30min to 60min, such as 30min, 35min, 40min, 45min or 50min, etc., and the time for the diffusion treatment is 1h to 10h. It can be understood that the higher the temperature of the diffusion treatment, the shorter the corresponding diffusion treatment time, and the thicker the pure aluminum layer, the longer the diffusion treatment time. That is, the purpose of the diffusion treatment is to completely transform the pure aluminum layer into a protective coating having a multi-layer intermetallic compound phase layer.

[0041] Furthermore, some embodiments of the present invention also provide the application of the above-mentioned high-temperature oxidation-resistant heat-resistant steel in the preparation of high-temperature workpieces, which mainly include applications in industrial production sites with a large demand for heat-resistant steel, such as cement plants, waste treatment plants, and internal combustion engine units. For example, the high-temperature workpiece can be the internal lining of a steam turbine unit, the discharge grate plate of a cement plant, or the hanging plate of a supercritical generator set.

[0042] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0043] Example 1

[0044] This embodiment provides a method for preparing high temperature oxidation resistant heat resistant steel. In this embodiment, ZG 40 Cr 27 Ni4 is the basic heat-resistant steel, and a pure aluminum layer with a thickness of 500μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0045] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 900°C and held for 10 hours. After the holding period, the sample was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0046] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was heated in the furnace and subjected to 200 hours of cyclic oxidation and 200 hours of isothermal oxidation at 1000°C. An alloy sample was taken out every 20 hours of isothermal oxidation and weighed using a balance with an accuracy of 0.1 mg. An alloy sample was taken out every 20 hours of cyclic oxidation and weighed using a balance with an accuracy of 0.1 mg. After weighing, it was placed back in an oxidizing atmosphere at 1000°C and continued cyclic oxidation. After 200 hours of isothermal oxidation, the alloy lost 61.3 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 59.0 mg.

[0047] Example 2

[0048] This embodiment uses ZG 40 Cr 27 Ni4 is used as the basic heat-resistant steel. A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate in the same manner as in Example 1.

[0049] After the spraying is completed, the temperature is raised to 900° C. in the same manner as in Example 1 and kept at this temperature for 6 hours. After the holding is completed, the steel is cooled with the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0050] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 1. The weight loss of the alloy after 200 h of isothermal oxidation was 62.0 mg, and the weight loss after 200 h of cyclic oxidation was 60.0 mg.

[0051] Example 3

[0052] This embodiment uses ZG 40 Cr 27 Ni4 is used as the basic heat-resistant steel. A pure aluminum layer with a thickness of 100 μm is sprayed on the heat-resistant steel substrate in the same manner as in Example 1.

[0053] After spraying, the temperature was raised to 900° C. and kept at this temperature for 1 hour in the same manner as in Example 1. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0054] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 1.

[0055] The alloy lost 71.1 mg of weight after 200 h of isothermal oxidation and 68.5 mg of weight after 200 h of cyclic oxidation.

[0056] Example 4

[0057] This embodiment uses ZG 40 Cr 27 Ni4 is the basic heat-resistant steel, and a pure aluminum layer with a thickness of 100μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0058] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 800°C and held for 1 hour. After the holding period, the sample was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0059] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was heated in the furnace and subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation. During the isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. During the cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and the cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 73.6 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 69.7 mg.

[0060] Example 5

[0061] This embodiment uses ZG 40 Cr 27 Ni4 is used as the basic heat-resistant steel. A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate in the same manner as in Example 4.

[0062] After spraying, the temperature was raised to 800° C. and kept at this temperature for 5 hours in the same manner as in Example 4. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0063] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 4. The alloy lost 68.2 mg of weight after 200 h of isothermal oxidation and 66.3 mg of weight after 200 h of cyclic oxidation.

[0064] Example 6

[0065] This embodiment uses ZG 40 Cr 27 Ni4 is used as the basic heat-resistant steel. A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate in the same manner as in Example 4.

[0066] After spraying, the temperature was raised to 800° C. and kept at this temperature for 9 hours in the same manner as in Example 4. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0067] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 4. The alloy lost 66.2 mg of weight after 200 h of isothermal oxidation and 64.8 mg of weight after 200 h of cyclic oxidation.

[0068] Example 7

[0069] This embodiment uses ZG 40 Cr 27 Ni4 is the basic heat-resistant steel, and a pure aluminum layer with a thickness of 100μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0070] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 700°C and held for 1 hour. After the holding period, the sample was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0071] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was heated in the furnace and subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation. During the isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. During the cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and the cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 76.8 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 72.3 mg.

[0072] Example 8

[0073] This embodiment uses ZG 40 Cr 27Ni4 is used as the basic heat-resistant steel. A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate in the same manner as in Example 7.

[0074] After spraying, the temperature was raised to 700°C and kept at this temperature for 5 hours in the same manner as in Example 7. After the temperature was kept at this temperature, the steel was cooled in the furnace to obtain high temperature oxidation resistant heat resistant steel.

[0075] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 7. The alloy weight loss after 200 h of isothermal oxidation was 72.3 mg, and the weight loss after 200 h of cyclic oxidation was 70.5 mg.

[0076] Example 9

[0077] This embodiment uses ZG 40 Cr 27 Ni4 is used as the basic heat-resistant steel. A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate in the same manner as in Example 7.

[0078] After spraying, the temperature was raised to 700°C in the same manner as in Example 7 and kept at that temperature for 8 hours. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0079] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 7. The alloy weight loss after 200 h of isothermal oxidation was 69.7 mg, and the weight loss after 200 h of cyclic oxidation was 68.2 mg.

[0080] Example 10

[0081] This embodiment provides a method for preparing high temperature oxidation resistant heat resistant steel. In this embodiment, ZG 40 Cr 25 Ni 20 A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0082] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 900°C and held for 10 hours. After the holding period, the sample was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0083] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was heated in the furnace and subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation. During the isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. During the cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and the cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 58.0 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 57.6 mg.

[0084] Example 11

[0085] This embodiment uses ZG 40 Cr 25 Ni 20 For the basic heat-resistant steel, a pure aluminum layer with a thickness of 500 μm was sprayed on the heat-resistant steel substrate in the same manner as in Example 10.

[0086] After spraying, the temperature was raised to 900°C in the same manner as in Example 10 and kept at this temperature for 6 hours. After the holding period, the steel was cooled with the furnace to resist high temperature oxidation.

[0087] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 10. The alloy weight loss after 200 h of isothermal oxidation was 60.1 mg, and after 200 h of cyclic oxidation was 59.8 mg.

[0088] Example 12

[0089] This embodiment uses ZG 40 Cr 25 Ni 20 For the basic heat-resistant steel, a pure aluminum layer with a thickness of 100 μm was sprayed on the heat-resistant steel substrate in the same manner as in Example 10.

[0090] After spraying, the temperature was raised to 900° C. in the same manner as in Example 10 and kept at that temperature for 1 hour. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0091] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 10. The alloy lost 64.2 mg of weight after 200 h of isothermal oxidation and 63.7 mg of weight after 200 h of cyclic oxidation.

[0092] Example 13

[0093] This embodiment provides a method for preparing high temperature oxidation resistant heat resistant steel. In this embodiment, ZG 40 Cr 25 Ni 20A pure aluminum layer with a thickness of 100 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0094] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 800°C and held for 1 hour. After the holding period, the sample was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0095] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was heated in the furnace and subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation. During the isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. During the cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and the cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 65.8 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 64.6 mg.

[0096] Example 14

[0097] This embodiment uses ZG 40 Cr 25 Ni 20 For the basic heat-resistant steel, a pure aluminum layer with a thickness of 500 μm was sprayed on the heat-resistant steel substrate in the same manner as in Example 13.

[0098] After spraying, the temperature was raised to 800°C and kept at this temperature for 5 hours in the same manner as in Example 13. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0099] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 13. The alloy weight loss after 200 h of isothermal oxidation was 64.2 mg, and the weight loss after 200 h of cyclic oxidation was 63.2 mg.

[0100] Example 15

[0101] This embodiment uses ZG 40 Cr 25 Ni 20 For the basic heat-resistant steel, a pure aluminum layer with a thickness of 500 μm was sprayed on the heat-resistant steel substrate in the same manner as in Example 13.

[0102] After spraying, the temperature was raised to 800°C and kept at this temperature for 9 hours in the same manner as in Example 13. After the holding period, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0103] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 13. The alloy weight loss after 200 h of isothermal oxidation was 63.6 mg, and the weight loss after 200 h of cyclic oxidation was 62.1 mg.

[0104] Example 16

[0105] This embodiment provides a method for preparing high temperature oxidation resistant heat resistant steel. In this embodiment, ZG 40 Cr 25 Ni 20 A pure aluminum layer with a thickness of 100 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0106] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to allow a solid-solid diffusion reaction between the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 650°C, where the pure aluminum layer melted. The sample was held at this temperature for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 700°C and held for 1 hour. After the holding period, the sample was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0107] After cooling, the alloy sample of the high-temperature oxidation-resistant heat-resistant steel was heated in the furnace and subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation. During isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1mg. During cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 67.2mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 65.8mg.

[0108] Example 17

[0109] This embodiment uses ZG 40 Cr 25 Ni 20 For the basic heat-resistant steel, a pure aluminum layer with a thickness of 500 μm was sprayed on the heat-resistant steel substrate in the same manner as in Example 16.

[0110] After spraying, the temperature was raised to 700°C and kept at this temperature for 5 hours in the same manner as in Example 16. After the temperature was kept at this temperature, the steel was cooled in the furnace to obtain high-temperature oxidation-resistant heat-resistant steel.

[0111] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 16. The alloy weight loss after 200 h of isothermal oxidation was 65.2 mg, and after 200 h of cyclic oxidation was 64.0 mg.

[0112] Example 18

[0113] This embodiment uses ZG 40 Cr 25 Ni 20 For the basic heat-resistant steel, a pure aluminum layer with a thickness of 500 μm was sprayed on the heat-resistant steel substrate in the same manner as in Example 16.

[0114] After spraying, the temperature was raised to 700°C and kept at this temperature for 8 hours in the same manner as in Example 16. After the temperature was kept at this temperature, the steel was cooled in the furnace to obtain high temperature oxidation resistant heat resistant steel.

[0115] After cooling, the high-temperature oxidation-resistant heat-resistant steel alloy sample was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 16. The alloy weight loss after 200 h of isothermal oxidation was 63.8 mg, and after 200 h of cyclic oxidation was 62.9 mg.

[0116] Comparative Example 1

[0117] This comparative example provides a heat-resistant steel that is not sprayed with a pure aluminum layer, and is subjected to cyclic oxidation for 200 hours and isothermal oxidation for 200 hours at 1000°C.

[0118] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel.

[0119] The alloy samples were subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation as the furnace temperature increased. During the isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. During the cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and the cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 307.8 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 303.6 mg.

[0120] Comparative Example 2

[0121] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness greater than 500 μm.

[0122] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel, using aluminum wire to spray a layer of pure aluminum with a thickness of 800μm on the heat-resistant steel substrate by arc spraying.

[0123] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The sample was then heated to 900°C and held for 10 hours. After cooling, the sample was removed and observed to have fallen off the unreacted aluminum layer. This resulted in an uneven surface and reduced volume of the diffusion layer.

[0124] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1. The weight loss of the alloy after 200 h of isothermal oxidation was 203.7 mg, and the weight loss after 200 h of cyclic oxidation was 195.8 mg.

[0125] The comparative examples show that if the aluminum layer is sprayed too thick, the diffusion reaction cannot be fully carried out, causing the aluminum layer to fall off, which in turn reduces the overall anti-oxidation and anti-corrosion performance. If the time is extended to allow the aluminum layer to be completely consumed, the time cost will increase.

[0126] Comparative Example 3

[0127] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of less than 100 μm.

[0128] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel, a pure aluminum layer with a thickness of 30μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0129] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The temperature was then held for 30 minutes to increase the fluidity of the aluminum liquid. The sample was then heated to 900°C and held for 10 hours. After cooling, the sample was removed and observed to reveal a decrease in volume at the diffusion layer surface, as well as cracking and shedding at the edges of the diffusion layer.

[0130] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1. The weight loss of the alloy after 200 h of isothermal oxidation was 285.7 mg, and the weight loss after 200 h of cyclic oxidation was 269.3 mg.

[0131] The comparative example shows that if the aluminum layer is sprayed too thin, it will be completely consumed during the temperature rise stage, resulting in poor diffusion effect and the diffusion layer cannot effectively protect the base heat-resistant steel.

[0132] Comparative Example 4

[0133] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 1000° C.

[0134] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel, a pure aluminum layer with a thickness of 500μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0135] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The temperature was then held for 30 minutes to increase the fluidity of the aluminum liquid. The sample was then heated to 1000°C and held for 10 hours. After cooling, the sample was removed and observed to have cracked in the diffusion layer. This cracking caused the diffusion layer to detach and lose its protective function, deteriorating the substrate.

[0136] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1.

[0137] The alloy lost 265.2 mg after isothermal oxidation for 200 h, and 257.3 mg after cyclic oxidation for 200 h.

[0138] The comparative example shows that if the diffusion heat treatment temperature is too high, the diffusion reaction of the diffusion layer will be intense during its formation, causing the diffusion layer to crack, thereby greatly reducing the protection effect.

[0139] Comparative Example 5

[0140] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 600°C.

[0141] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel, a pure aluminum layer with a thickness of 500μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0142] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The temperature was then held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 600°C and held for 10 hours. After cooling, the sample was removed and observed, revealing no diffusion layer formed at 600°C and severe oxidation and delamination of the substrate.

[0143] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1.

[0144] The alloy lost weight to 305.6 mg after 200 h of isothermal oxidation and to 302.3 mg after 200 h of cyclic oxidation.

[0145] The comparative example shows that if the diffusion heat treatment temperature is too low, the aluminum liquid is not completely melted, the diffusion layer cannot be formed, and the base heat-resistant steel cannot be protected.

[0146] Comparative Example 6

[0147] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 900°C.

[0148] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel, a pure aluminum layer with a thickness of 500μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0149] After spraying, the alloy sample was heated to 900°C in a furnace and kept at that temperature for 10 hours. After cooling, the alloy sample was removed and observed. It was found that although a diffusion layer was formed at 900°C, the diffusion layer was severely oxidized and detached.

[0150] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1.

[0151] The alloy lost 286.6 mg after isothermal oxidation for 200 h, and 293.3 mg after cyclic oxidation for 200 h.

[0152] The comparative examples show that if the temperature is raised directly to the diffusion temperature, the melting and diffusion of different areas of the aluminum layer will be uneven. Rapid temperature changes and localized transitional melting may lead to pores, shrinkage cavities, or cracks, preventing effective uniform diffusion at the interface. Consequently, the base heat-resistant steel will not be protected.

[0153] Comparative Example 7

[0154] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 900°C.

[0155] This comparative example uses ZG 40 Cr 27 Ni4 heat-resistant steel, a pure aluminum layer with a thickness of 500μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0156] After spraying, the alloy sample was heated to 500°C in a furnace and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 900°C and held for 10 hours. The sample was then cooled in the furnace. After cooling, the alloy sample was removed and observed to have formed a good diffusion layer at 900°C.

[0157] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1.

[0158] The alloy lost weight of 157.8 mg after 200 h of isothermal oxidation and 168.3 mg after 200 h of cyclic oxidation.

[0159] The comparative example concludes that if the temperature is raised to the diffusion temperature in two stages, different areas of the aluminum layer will melt and diffuse, but slight defects will be generated at the interface, achieving effective interface diffusion, but the diffusion is uneven, which plays a relative protective role on the base heat-resistant steel.

[0160] Comparative Example 8

[0161] This comparative example provides a heat-resistant steel that is not sprayed with a pure aluminum layer, and is subjected to cyclic oxidation for 200 hours and isothermal oxidation for 200 hours at 1000°C.

[0162] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel.

[0163] The alloy samples were subjected to 200 hours of cyclic oxidation at 1000°C and 200 hours of isothermal oxidation as the furnace temperature increased. During the isothermal oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. During the cyclic oxidation, an alloy sample was removed every 20 hours and weighed using a balance with an accuracy of 0.1 mg. After weighing, the sample was placed back in the oxidizing atmosphere at 1000°C and the cyclic oxidation continued. After 200 hours of isothermal oxidation, the alloy lost 295.3 mg of weight, and after 200 hours of cyclic oxidation, the weight loss was 292.7 mg.

[0164] Comparative Example 9

[0165] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness greater than 500 μm.

[0166] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel: A pure aluminum layer with a thickness of 1000 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0167] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The sample was then heated to 900°C and held for 10 hours. After cooling, the sample was removed and observed to have fallen off the unreacted aluminum layer. This resulted in an uneven surface and reduced volume of the diffusion layer.

[0168] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 6. The weight loss of the alloy after 200 h of isothermal oxidation was 198.6 mg, and the weight loss after 200 h of cyclic oxidation was 187.3 mg.

[0169] The comparative examples show that if the aluminum layer is sprayed too thick, the diffusion reaction cannot be fully carried out, causing the aluminum layer to fall off, which in turn reduces the overall anti-oxidation and anti-corrosion performance. If the time is extended to allow the aluminum layer to be completely consumed, the time cost will increase.

[0170] Comparative Example 10

[0171] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of less than 100 μm.

[0172] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel: A pure aluminum layer with a thickness of 50 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0173] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The temperature was then held for 30 minutes to increase the fluidity of the aluminum liquid. The sample was then heated to 900°C and held for 10 hours. After cooling, the sample was removed and observed to reveal a decrease in volume at the diffusion layer surface, as well as cracking and shedding at the edges of the diffusion layer.

[0174] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 6. The weight loss of the alloy after 200 h of isothermal oxidation was 235.2 mg, and the weight loss after 200 h of cyclic oxidation was 250.4 mg.

[0175] The comparative example shows that if the aluminum layer is sprayed too thin, it will be completely consumed during the temperature rise stage, resulting in poor diffusion effect and the diffusion layer cannot effectively protect the base heat-resistant steel.

[0176] Comparative Example 11

[0177] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 1000° C.

[0178] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel: A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0179] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The temperature was then held for 30 minutes to increase the fluidity of the aluminum liquid. The sample was then heated to 1000°C and held for 10 hours. After cooling, the sample was removed and observed to have cracked in the diffusion layer. This cracking caused the diffusion layer to detach and lose its protective function, deteriorating the substrate.

[0180] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 6. The weight loss of the alloy after 200 h of isothermal oxidation was 230.8 mg, and the weight loss after 200 h of cyclic oxidation was 227.6 mg.

[0181] The comparative example shows that if the diffusion heat treatment temperature is too high, the diffusion reaction of the diffusion layer will be intense during its formation, causing the diffusion layer to crack, thereby greatly reducing the protection effect.

[0182] Comparative Example 12

[0183] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 600°C.

[0184] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel: A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0185] After spraying, the alloy sample was heated in a furnace to 500°C and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 660°C, where the pure aluminum layer melted. The sample was then held for 30 minutes to increase the fluidity of the aluminum liquid. The temperature was then raised to 600°C and held for 10 hours. After cooling, the sample was removed and observed, revealing no diffusion layer formed at 600°C and severe oxidation and delamination of the substrate.

[0186] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1. The weight loss of the alloy after 200 h of isothermal oxidation was 292.9 mg, and the weight loss after 200 h of cyclic oxidation was 286.3 mg.

[0187] The comparative example shows that if the diffusion heat treatment temperature is too low, the aluminum liquid is not completely melted, the diffusion layer cannot be formed, and the base heat-resistant steel cannot be protected.

[0188] Comparative Example 13

[0189] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 900°C.

[0190] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel: A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0191] After spraying, the alloy sample was heated to 900°C in a furnace and kept at that temperature for 10 hours. After cooling, the alloy sample was removed and observed. It was found that although a diffusion layer was formed at 900°C, the diffusion layer was severely oxidized and detached.

[0192] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1.

[0193] The alloy lost 256.6 mg after isothermal oxidation for 200 h, and 271.3 mg after cyclic oxidation for 200 h.

[0194] The comparative examples show that if the temperature is raised directly to the diffusion temperature, the melting and diffusion of different areas of the aluminum layer will be uneven. Rapid temperature changes and localized transitional melting may lead to pores, shrinkage cavities, or cracks, preventing effective uniform diffusion at the interface. Consequently, the base heat-resistant steel will not be protected.

[0195] Comparative Example 14

[0196] This comparative example provides a heat-resistant steel with a sprayed pure aluminum layer having a thickness of 500 μm and a diffusion heat treatment temperature of 900°C.

[0197] This comparative example uses ZG 40 Cr 25 Ni 20 Heat-resistant steel: A pure aluminum layer with a thickness of 500 μm is sprayed on the heat-resistant steel substrate using aluminum wire by arc spraying.

[0198] After spraying, the alloy sample was heated to 500°C in a furnace and held for 30 minutes to ensure uniform heating of the heat-resistant steel substrate and the pure aluminum layer. The temperature was then raised to 900°C and held for 10 hours. The sample was then cooled in the furnace. After cooling, the alloy sample was removed and observed to have formed a good diffusion layer at 900°C.

[0199] Isothermal oxidation and cyclic oxidation were carried out in the same manner as in Comparative Example 1.

[0200] The alloy lost weight of 118.7 mg after 200 h of isothermal oxidation and 136.5 mg after 200 h of cyclic oxidation.

[0201] The comparative example concludes that if the temperature is raised to the diffusion temperature in two stages, different areas of the aluminum layer will melt and diffuse, but slight defects will be generated at the interface, achieving effective interface diffusion, but the diffusion is uneven, which plays a relative protective role on the base heat-resistant steel.

[0202] The performance comparison of the high Cr and low Ni heat-resistant steels of Examples 1-9 and Comparative Examples 1-7 is shown in Table 1, and the performance comparison of the high Cr and high Ni heat-resistant steels of Examples 10-18 and Comparative Examples 8-14 is shown in Table 2.

[0203] Table 1 Weight loss of high Cr and low Ni heat-resistant steel after isothermal oxidation and cyclic oxidation for 200 h

[0204]

[0205]

[0206] Table 2 Weight loss of high Cr and high Ni heat-resistant steel after isothermal oxidation and cyclic oxidation for 200 h

[0207]

[0208] The high temperature oxidation resistant heat resistant steel and protective coating obtained in Example 1 and Example 10 were divided into three phases under scanning electron microscope backscatter diffraction (EBSD). The scanning results are as follows: Figure 1 shown.

[0209] The hardness of the protective coating of the high temperature oxidation resistant heat resistant steel of Example 1 and Example 10 was tested by microhardness measurement method. The results are as follows: Figure 2 The structures of the protective coatings of the high temperature oxidation resistant heat resistant steels of Example 1 and Example 10 were observed by scanning electron microscopy. The results are shown in FIG. Figure 3 As shown by Figure 3 It can be seen that the protective coatings of the high-Cr low-Ni heat-resistant steel and the high-Cr high-Ni heat-resistant steel both have a layer structure of three phases, and the difference between them is that the thickness of the layer structure is different.

[0210] Furthermore, the macroscopic appearance of the high temperature oxidation resistant heat-resistant steels of Example 1 and Example 10 after cyclic oxidation at 1000°C for 200h was observed. Figure 4 As shown. Figure 4 (a) in Example 10, Figure 4 (b) is Example 1. The coatings prepared in the two examples have the best protective effect and the oxidation peeling phenomenon is not serious. (a) in the figure is the high Cr and high Ni sample of Example 10, which has high antioxidant properties. After the oxidation is completed under the protection of the coating, the metallic luster can still be seen.

[0211] Furthermore, the microstructures of the high temperature oxidation resistant heat resistant steels of Example 1 and Comparative Example 1 after cyclic oxidation at 1000°C for 200h were observed. Figure 5 As shown. Figure 5 (a) is Example 1, Figure 5 (b) is Comparative Example 1. Figure 5 From (a) in the figure, we can see that under the condition of coating protection, after long-term high-temperature oxidation, a dense Al2O3 oxide film is formed on the surface, and the oxidation depth is shallow, which has a good protective effect on the substrate. Figure 5 As shown in (b), in the absence of coating protection, a traditional Cr2O3 oxide film is generated on the metal surface, which is deeply oxidized and accompanied by severe internal oxidation.

[0212] In summary, the embodiments of the present invention have the following advantages over the prior art:

[0213] 1. The raw materials used in the metal protective material formula are simple and are all common substances on the market. The purchase channels are wide, and the prepared protective coating has a wide range of applications and broad market prospects.

[0214] 2. The aluminum coating is applied using arc spraying, a highly efficient and simple thermal spraying process. The spraying process is highly efficient, pollution-free, and provides excellent coating adhesion. Furthermore, the coating material does not need to be too thick to achieve excellent protection. Even with a 100μm coating, after 200 hours of cyclic oxidation, the coating exhibits excellent protection, significantly reducing time and costs.

[0215] 3. The protective effect is due to the diffusion layer produced by the interface reaction during the diffusion heat treatment stage. In the temperature range of 700℃-900℃, the interface reaction forms three diffusion layers to protect the metal and achieve the beneficial effect of multiple protection.

[0216] 4. While reducing costs, the coating significantly improves the metal's high-temperature thermal corrosion and oxidation resistance. After cyclic oxidation at 1000°C for 200 hours, the coating maintains a strong bond with the heat-resistant steel. The surface morphology remains unchanged and cracks remain unchanged, demonstrating excellent protective properties. Therefore, this metal protective coating offers excellent protection for heat-resistant steel and is worthy of widespread application.

[0217] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A high temperature oxidation resistant heat-resistant steel, characterized in that: The invention comprises a heat-resistant steel substrate and a protective coating on the surface of the heat-resistant steel substrate, wherein the protective coating is composed of an intermetallic compound, which comprises, from the inside to the outside, a (Fe, Ni) Al phase layer, a FeAl3 (Fe4Al 13 ) phase layer and Fe2Al5(FeAl 2.8 ) physical layer; The preparation of the high-temperature oxidation-resistant heat-resistant steel includes the following steps: coating a pure aluminum layer on the surface of the heat-resistant steel substrate and then performing heat treatment, wherein the thickness of the coated pure aluminum layer is 100 μm to 500 μm; the heat treatment includes a first preheating treatment, a second preheating treatment, and a diffusion treatment, wherein the temperature of the first preheating treatment is 450°C to 550°C, the temperature of the second preheating treatment is 650°C to 670°C, and the temperature of the diffusion treatment is 700°C to 900°C. The time of the first preheating treatment is 30 min to 60 min, the time of the second preheating treatment is 30 min to 60 min, and the time of the diffusion treatment is 1 h to 10 h.

2. The high temperature oxidation resistant heat-resistant steel according to claim 1, characterized in that: The thickness of the protective coating is 0.2 mm to 1 mm.

3. The high temperature oxidation resistant heat-resistant steel according to claim 1 or 2, characterized in that: The heat-resistant steel substrate is chromium-nickel heat-resistant steel.

4. The high temperature oxidation resistant heat-resistant steel according to claim 3, characterized in that: The chromium-nickel heat-resistant steel is a high-Cr, low-Ni heat-resistant steel or a high-Cr, high-Ni heat-resistant steel. The chemical composition of the high-Cr, low-Ni heat-resistant steel is as follows by weight: Cr 15.0%-30.0%, Ni 4.0%-10.0%, Mn 1.0%-1.1%, Si 1.4%-1.5%, C 0.3%-0.4%, V 0.12%-0.13%, and the balance is iron and inevitable trace elements; the chemical composition of the high-Cr, high-Ni heat-resistant steel is as follows by weight: Cr 15.0%-30.0%, Ni 10.0%-25.0%, Mn 0.5%-1.0%, Si 0.9%-1.0%, C 0.3%-0.4%, N 0.16%-0.17%, and the balance is iron and inevitable trace elements.

5. The high temperature oxidation resistant heat-resistant steel according to claim 1, characterized in that: The pure aluminum layer is formed by arc spraying; Before coating, the surface of the heat-resistant steel substrate is sandblasted.

6. Use of the high-temperature oxidation-resistant heat-resistant steel according to any one of claims 1 to 5 in the preparation of high-temperature workpieces.

7. The use according to claim 6, characterized in that The high-temperature workpiece is an internal lining plate of a steam turbine unit, a discharge grate plate of a cement plant, or a hanging plate of a supercritical generator unit.

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