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

Abstract

The invention discloses high-temperature-oxidation-resistant heat-resistant steel and a preparation method and application thereof.The high-temperature-oxidation-resistant heat-resistant steel comprises a heat-resistant steel base material and a protective coating located on the surface of the heat-resistant steel base material, and the protective coating is composed of intermetallic compounds and sequentially comprises a (Fe, Ni) Al phase layer, a FeAl3 (Fe4Al13) phase layer and a Fe2Al5 (FeAl2.8) phase layer from inside to outside. The high-temperature-oxidation-resistant heat-resistant steel is obtained by coating the surface of a heat-resistant steel base material with a pure aluminum layer and then carrying out heat treatment. The preparation process of the protective coating is high in efficiency, high in positioning capability of the protective unit and environment-friendly. The prepared coating can effectively protect the basic heat-resistant steel, the service life of the heat-resistant steel in a hot corrosion environment is greatly prolonged, and the comprehensive cost of the material is remarkably reduced.

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 facing 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 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 may also be frequently replaced during long-term service, thus affecting the continuity and efficiency of industrial production.

[0003] The main components of heat-resistant steel usually include elements such as chromium, nickel, and iron to form an alloy structure with high-temperature stability. Although these basic materials have certain high-temperature resistance, in the context of the growing demand of modern industry, existing heat-resistant steel materials are facing the problem of not being able to fully meet higher performance requirements. Especially in high-temperature oxidizing environments, the oxidation resistance and thermal corrosion resistance of steel have become key factors restricting its application, resulting in potential risks in the production process and adding additional cost burdens.

[0004] In the face of the above technical problems, traditional solutions often focus on improving the chemical composition of steel to improve its performance. However, this approach is limited in an era of increasingly stringent cost control and environmental protection requirements. Therefore, seeking more efficient and environmentally friendly protection measures has become the focus of the industry.

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

[0006] The object 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 technical problems.

[0007] The present invention is achieved in that:

[0008] In a 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 layer.

[0009] In an optional embodiment, the protective coating has a thickness of 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 percentage: Cr 15.0%~30.0%, Ni 4.0%~10.0%, Mn 1.0%~1.1%, Si 1.4%~1.5%, C0.3%~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 percentage: Cr 15.0%~30.0%, Ni10.0%~25.0%, Mn 0.5%~1.0%, Si 0.9%~1.0%, C 0.3%~0.4%, N0.16%~0.17%, and the balance 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 of the first preheating treatment is 30 minutes to 60 minutes, the time of the second preheating treatment is 30 minutes to 60 minutes, and the time of 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 the heat-resistant steel substrate, multiple protective effects on the heat-resistant steel substrate can be achieved, which greatly improves the high-temperature thermal corrosion and oxidation resistance of the heat-resistant steel, and the intermetallic compound formed by the coating and the heat-resistant substrate makes the two have better bonding performance, and after multiple high-temperature cyclic oxidation, the morphology is complete and has good protective ability. Therefore, the heat-resistant steel has a better application prospect in industrial production sites with a large demand for heat-resistant steel, such as cement plants, garbage treatment plants, and internal combustion units. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0022] Figure 1 The 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 low-Ni sample protective coating 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 The SEM images of the protective coating of the heat-resistant steel samples of Example 1 and Example 10; wherein (a) and (b) are the protective coating of the heat-resistant steel of Example 1, and (c) and (d) are the protective coating of the heat-resistant steel of Example 1;

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

[0026] Figure 5 The microscopic morphology 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] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used 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 and 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 includes, 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.

[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. The service life of heat-resistant steel is extended while reducing costs. Based on the idea of ​​protective coatings, the inventor 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-layer structure composed of the phase layer can achieve multiple protection effects for heat-resistant steel, and the protective coating and the heat-resistant steel substrate also have better bonding performance. Specifically, the multi-layer protective layer formed by various aluminum intermetallic compounds has a relatively dense microstructure, thereby reducing the direct erosion of the material by external media (such as oxygen), and through the combination with Fe and Ni elements, it not only enhances its antioxidant ability, but also makes it have better thermal stability.

[0031] In some embodiments, in order to achieve a better protective effect, the protective coating needs to have a certain thickness. The protective coating also needs to avoid being too thick to avoid the failure to form complete intermetallic compounds through heat treatment and affecting the protective 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 percentage: 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%, V0.12%~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 percentage: 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 the heat-resistant steel substrate includes: first sandblasting the surface of the heat-resistant steel substrate, and then coating the pure aluminum layer. The sandblasting can remove impurities, oxide layers, stains, etc. on the surface of the material, thereby improving the bonding strength between the coating and the substrate, and is also conducive to the subsequent heat treatment process of the pure aluminum layer 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 provide effective protection for 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] Exemplarily, the chemical composition of the pure aluminum layer in the embodiment of the present invention is 99.9% Al by weight, and the remainder is inevitable trace elements.

[0038] For reference, the pure aluminum layer is formed by arc spraying, wherein the raw material can be pure aluminum wire. This spraying method is highly efficient and simple in process, and the spraying process is highly efficient, pollution-free, and has a good coating bonding effect. Of course, in other implementations, chemical vapor deposition, physical vapor deposition, magnetron sputtering, electroplating, etc. can also be used to coat the pure aluminum layer.

[0039] Furthermore, in order to completely react the pure aluminum layer, a phase layer having (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, ensuring that the aluminum industry has good fluidity; the temperature of the diffusion treatment is 700 ℃ ~ 900 ℃. If the temperature is directly raised to the temperature of the diffusion treatment, 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 effective interface uniform diffusion cannot be achieved. Therefore, it is necessary to perform a preheating treatment between the diffusion treatments, and if the temperature is directly raised to the melting temperature of the pure aluminum layer, there is a difference in the heating rate between the heat-resistant steel substrate and the pure aluminum layer, which affects the bonding performance of the pure aluminum layer and the heat-resistant steel substrate, and then affects the interface reaction effect of thermal diffusion. Therefore, the first preheating treatment is performed to make the substrate and the pure aluminum layer 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, for example, 30min, 35min, 40min, 45min or 50min, etc., the time for the second preheat treatment is 30min to 60min, for example, 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. By way of example, the high-temperature workpiece may be an internal lining plate of a steam turbine unit, a discharging grate plate of a cement plant, or a hanging plate of a supercritical generator unit.

[0042] The features and performance of the present invention are further described in detail below in conjunction with 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 by using aluminum wire through arc spraying.

[0045] After spraying, the alloy sample was heated to 500℃ and kept for 30 minutes in the furnace to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 660℃, the pure aluminum layer melted at this temperature, and kept for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was continued to rise to 900℃ and kept for 10 hours. After the insulation, it 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 subjected to 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace was heated. An alloy sample was taken out every 20h for isothermal oxidation and weighed using a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed using a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 61.3mg, and the weight loss after 200h of cyclic oxidation was 59.0mg.

[0047] Example 2

[0048] This embodiment uses ZG 40 Cr 27 Ni4 is 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 heat preservation is completed, the steel is cooled with the furnace to obtain a high-temperature oxidation-resistant heat-resistant steel.

[0050] After cooling, the alloy sample of 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 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 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 1 hour. After the heat preservation is completed, the furnace is cooled to obtain a 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 after isothermal oxidation for 200 h, and lost 68.5 mg after cyclic oxidation for 200 h.

[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 by using aluminum wire through arc spraying.

[0058] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 660℃, the pure aluminum layer melted at this temperature, and kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was continued to rise to 800℃ and kept warm for 1 hour. After the insulation, it was cooled in the furnace to obtain high temperature oxidation resistant heat-resistant steel.

[0059] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace was heated. An alloy sample was taken out every 20h for isothermal oxidation and weighed with a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed with a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 73.6mg, and the weight loss after 200h of cyclic oxidation was 69.7mg.

[0060] Example 5

[0061] This embodiment uses ZG 40 Cr 27 Ni4 is 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 the spraying is completed, the temperature is raised to 800°C in the same manner as in Example 4 and kept at this temperature for 5 hours. After the heat preservation is completed, the furnace is cooled to obtain a 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 weight loss of the alloy after 200 h of isothermal oxidation was 68.2 mg, and the weight loss after 200 h of cyclic oxidation was 66.3 mg.

[0064] Example 6

[0065] This embodiment uses ZG 40 Cr 27 Ni4 is 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 the spraying is completed, the temperature is raised to 800° C. in the same manner as in Example 4 and kept at this temperature for 9 hours. After the heat preservation is completed, the furnace is cooled to obtain a 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 weight loss of the alloy after 200 h of isothermal oxidation was 66.2 mg, and the weight loss after 200 h of cyclic oxidation was 64.8 mg.

[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 by using aluminum wire through arc spraying.

[0070] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 660℃, the pure aluminum layer melted at this temperature, and kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was continued to rise to 700℃ and kept warm for 1 hour. After the insulation, it was cooled in the furnace to obtain high temperature oxidation resistant heat-resistant steel.

[0071] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace was heated. An alloy sample was taken out every 20h for isothermal oxidation and weighed with a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed with a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 76.8mg, and the weight loss after 200h of cyclic oxidation was 72.3mg.

[0072] Example 8

[0073] This embodiment uses ZG 40 Cr 27Ni4 is 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 the spraying is completed, the temperature is raised to 700°C in the same manner as in Example 7 and kept at this temperature for 5 hours. After the heat preservation is completed, the steel is cooled with the furnace to obtain a high temperature oxidation resistant heat-resistant steel.

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

[0076] Example 9

[0077] This embodiment uses ZG 40 Cr 27 Ni4 is 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 the spraying is completed, the temperature is raised to 700°C in the same manner as in Example 7 and kept at this temperature for 8 hours. After the heat preservation is completed, the furnace is cooled to obtain a high temperature oxidation resistant heat-resistant steel.

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

[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 to 500℃ and kept for 30 minutes in the furnace to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 660℃, the pure aluminum layer melted at this temperature, and kept for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was continued to rise to 900℃ and kept for 10 hours. After the insulation, it was cooled in the furnace to obtain high temperature oxidation resistant heat-resistant steel.

[0083] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace was heated. An alloy sample was taken out every 20h for isothermal oxidation and weighed with a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed with a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 58.0mg, and the weight loss after 200h of cyclic oxidation was 57.6mg.

[0084] Embodiment 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 heat preservation, the steel was cooled with the furnace to resist high temperature oxidation.

[0087] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 10. The weight loss of the alloy after 200 h of isothermal oxidation was 60.1 mg, and the weight loss 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 the spraying is completed, the temperature is raised to 900°C in the same manner as in Example 10 and kept at this temperature for 1 hour. After the heat preservation is completed, the furnace is cooled to obtain a high temperature oxidation resistant heat-resistant steel.

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

[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 to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 660℃, the pure aluminum layer melted at this temperature, and kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was continued to rise to 800℃ and kept warm for 1 hour. After the insulation, it was cooled in the furnace to obtain high temperature oxidation resistant heat-resistant steel.

[0095] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace was heated. An alloy sample was taken out every 20h for isothermal oxidation and weighed with a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed with a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 65.8mg, and the weight loss after 200h of cyclic oxidation was 64.6mg.

[0096] Embodiment 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 the spraying is completed, the temperature is raised to 800°C in the same manner as in Example 13 and kept at this temperature for 5 hours. After the heat preservation is completed, the furnace is cooled to obtain a high temperature oxidation resistant heat-resistant steel.

[0099] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 13. The weight loss of the alloy 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] Embodiment 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 the spraying is completed, the temperature is raised to 800°C in the same manner as in Example 13 and kept at this temperature for 9 hours. After the heat preservation is completed, the furnace is cooled to obtain a high temperature oxidation resistant heat-resistant steel.

[0103] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to isothermal oxidation and cyclic oxidation in the same manner as in Example 13. The weight loss of the alloy 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 to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer undergo solid-solid diffusion reaction. Then the temperature was raised to 650℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 700℃ and kept warm for 1 hour. After the insulation, the sample was cooled in the furnace to obtain high temperature oxidation resistant heat-resistant steel.

[0107] After cooling, the alloy sample of high temperature oxidation resistant heat-resistant steel was subjected to 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace was heated. An alloy sample was taken out every 20h for isothermal oxidation and weighed with a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed with a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 67.2mg, and the weight loss after 200h of cyclic oxidation was 65.8mg.

[0108] Embodiment 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 the spraying is completed, the temperature is raised to 700°C in the same manner as in Example 16 and kept at this temperature for 5 hours. After the heat preservation is completed, the furnace is cooled to obtain a high temperature oxidation resistant heat-resistant steel.

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

[0112] Embodiment 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 the spraying is completed, the temperature is raised to 700°C in the same manner as in Example 16 and kept at this temperature for 8 hours. After the heat preservation is completed, the steel is cooled with the furnace to obtain a heat-resistant steel resistant to high temperature oxidation.

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

[0116] Comparative Example 1

[0117] This comparative example provides a heat-resistant steel which 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 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace temperature increased. An alloy sample was taken out every 20h for isothermal oxidation and weighed using a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed using a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The weight loss of the alloy after 200h of isothermal oxidation was 307.8mg, and the weight loss after 200h of cyclic oxidation was 303.6mg.

[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, a pure aluminum layer with a thickness of 800μm is sprayed on the heat-resistant steel substrate by using aluminum wire through arc spraying.

[0123] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 900℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed that the unreacted aluminum layer on the top fell off. After the falling off, the surface of the diffusion layer was uneven and the volume of the diffusion layer was reduced.

[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, resulting in the aluminum layer falling 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 layer of pure aluminum with a thickness of 30μm is sprayed on the heat-resistant steel substrate by using aluminum wire through arc spraying.

[0129] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 900℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed to find that the volume of the diffusion layer surface decreased, and the edge area of ​​the diffusion layer cracked and fell off.

[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 heating 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 layer of pure aluminum with a thickness of 500μm is sprayed on the heat-resistant steel substrate by using aluminum wire through arc spraying.

[0135] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the heat-resistant steel and pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 1000℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed to find cracks in the diffusion layer. After cracking, the diffusion layer fell off and lost its protective function, causing the substrate to deteriorate.

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

[0137] The alloy lost weight of 265.2 mg after isothermal oxidation for 200 h, and lost weight of 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 cracks in the diffusion layer and 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 layer of pure aluminum with a thickness of 500μm is sprayed on the heat-resistant steel substrate by using aluminum wire through arc spraying.

[0142] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the substrate heat-resistant steel and pure aluminum layer evenly heated, and then heated to 660℃, the pure aluminum layer melted at this temperature, and kept warm for 30 minutes to increase the fluidity of Al liquid. Then the temperature was adjusted to 600℃ and kept warm for 10 hours. After the insulation, it was cooled in the furnace. After cooling, the alloy sample was taken out and observed that the diffusion layer was not formed at 600℃, and the substrate was severely oxidized and detached.

[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 isothermal oxidation for 200 h, and lost weight to 302.3 mg after cyclic oxidation for 200 h.

[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 effect of protecting the base heat-resistant steel cannot be achieved.

[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 layer of pure aluminum with a thickness of 500μm is sprayed on the heat-resistant steel substrate by using aluminum wire through arc spraying.

[0149] After spraying, the alloy sample was heated to 900℃ in the furnace and kept at this temperature for 10 hours. After the heat preservation, the alloy sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed. It was found that although the diffusion layer was formed at 900℃, the diffusion layer was severely oxidized and fell off.

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

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

[0152] The comparative example shows that if the temperature is directly raised to the diffusion temperature, the melting and diffusion of different areas of the aluminum layer will be uneven, and the rapid temperature change and local transitional melting may lead to pores, shrinkage holes or cracks, etc., and effective interface uniform diffusion cannot be achieved, which will not have the effect of protecting the base heat-resistant steel.

[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 layer of pure aluminum with a thickness of 500μm is sprayed on the heat-resistant steel substrate by using aluminum wire through arc spraying.

[0156] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 900℃ and kept warm for 10 hours. After the insulation, it was cooled in the furnace. After cooling, the alloy sample was taken out and observed to form a good diffusion layer at 900℃.

[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 isothermal oxidation for 200 h, and lost weight of 168.3 mg after cyclic oxidation for 200 h.

[0159] The comparative example shows 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 occur at the interface, achieving effective interface diffusion, but the diffusion is uneven, which plays a relative protective role on the matrix heat-resistant steel.

[0160] Comparative Example 8

[0161] This comparative example provides a heat-resistant steel which 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 200h cyclic oxidation and 200h isothermal oxidation at 1000℃ as the furnace temperature increased. An alloy sample was taken out every 20h for isothermal oxidation and weighed using a balance with an accuracy of 0.1mg. An alloy sample was taken out every 20h for cyclic oxidation and weighed using a balance with an accuracy of 0.1mg. After weighing, it was placed back in an oxidizing atmosphere at 1000℃ for continued cyclic oxidation. The alloy lost 295.3mg after 200h of isothermal oxidation and 292.7mg after 200h of cyclic oxidation.

[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 by using aluminum wire in an arc spraying manner.

[0167] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 900℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed that the unreacted aluminum layer on the top fell off. After the falling off, the surface of the diffusion layer was uneven and the volume of the diffusion layer was reduced.

[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, resulting in the aluminum layer falling 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 by using aluminum wire in an arc spraying manner.

[0173] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 900℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed to find that the volume of the diffusion layer surface decreased, and the edge area of ​​the diffusion layer cracked and fell off.

[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 heating 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 by using aluminum wire in an arc spraying manner.

[0179] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the heat-resistant steel and pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 1000℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed to find cracks in the diffusion layer. After cracking, the diffusion layer fell off and lost its protective function, causing the substrate to deteriorate.

[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 cracks in the diffusion layer and 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 by using aluminum wire in an arc spraying manner.

[0185] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the heat-resistant steel and pure aluminum layer evenly heated. Then the temperature was raised to 660℃, and the pure aluminum layer melted at this temperature. The temperature was kept warm for 30 minutes to increase the fluidity of the Al liquid. Then the temperature was raised to 600℃ and kept warm for 10 hours. After the insulation, the sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed to find that the diffusion layer was not formed at 600℃ and the matrix was severely oxidized and detached.

[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 effect of protecting the base heat-resistant steel cannot be achieved.

[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 by using aluminum wire in an arc spraying manner.

[0191] After spraying, the alloy sample was heated to 900℃ in the furnace and kept at this temperature for 10 hours. After the heat preservation, the alloy sample was cooled in the furnace. After cooling, the alloy sample was taken out and observed. It was found that although the diffusion layer was formed at 900℃, the diffusion layer was severely oxidized and fell off.

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

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

[0194] The comparative example shows that if the temperature is directly raised to the diffusion temperature, the melting and diffusion of different areas of the aluminum layer will be uneven, and the rapid temperature change and local transitional melting may lead to pores, shrinkage holes or cracks, etc., and effective interface uniform diffusion cannot be achieved, which will not have the effect of protecting the base heat-resistant steel.

[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 by using aluminum wire in an arc spraying manner.

[0198] After spraying, the alloy sample was heated to 500℃ and kept warm for 30 minutes to make the base heat-resistant steel and the pure aluminum layer evenly heated, and then heated to 900℃ and kept warm for 10 hours. After the insulation, it was cooled in the furnace. After cooling, the alloy sample was taken out and observed to form a good diffusion layer at 900℃.

[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 isothermal oxidation for 200 h, and lost weight of 136.5 mg after cyclic oxidation for 200 h.

[0201] The comparative example shows 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 occur at the interface, achieving effective interface diffusion, but the diffusion is uneven, which plays a relative protective role on the matrix heat-resistant steel.

[0202] The performance comparison results of the high Cr and low Ni heat-resistant steels of Examples 1-9 and Comparative Examples 1-7 are shown in Table 1, and the performance comparison results of the high Cr and high Ni heat-resistant steels of Examples 10-18 and Comparative Examples 8-14 are 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 the microhardness measurement method, and 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, and the results are as follows: Figure 3 As shown by Figure 3 It can be seen that the protective coatings of high-Cr low-Ni heat-resistant steel and 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) is 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, it can be seen 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, with a deep degree of oxidation 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 formula of metal protective materials 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 process is arc spraying in thermal spraying, which is highly efficient and simple. The spraying process is efficient, pollution-free, and has good coating bonding effect. The coating material does not need to be too thick during spraying to achieve a good protective effect. When the coating is 100μm, after 200h of cyclic oxidation, the coating also shows a good protective effect. This greatly reduces the time cost.

[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 protections.

[0216] 4. It not only reduces the cost, but also greatly improves the high-temperature thermal corrosion and oxidation resistance of the metal. After 1000℃-200h cyclic oxidation, the coating still has a strong bonding ability with the heat-resistant steel, and the surface morphology does not change after cyclic oxidation, and there is no cracking, and it still has good protection ability. Therefore, the metal material protective coating has a good protective effect on heat-resistant steel and is worthy of promotion and application.

[0217] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope 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.

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, and the chemical composition of the high-Cr low-Ni heat-resistant steel is calculated by weight percentage: 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 calculated by weight percentage: 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. A method for preparing high temperature oxidation resistant heat resistant steel according to any one of claims 1 to 4, characterized in that: It includes: A pure aluminum layer is coated on the surface of the heat-resistant steel substrate and then heat treated.

6. The method for preparing high temperature oxidation resistant heat resistant steel according to claim 5, characterized in that: The thickness of the coated pure aluminum layer is 100 μm to 500 μm; Preferably, the pure aluminum layer is formed by arc spraying; Preferably, before coating, the surface of the heat-resistant steel substrate is sandblasted.

7. The method for preparing high temperature oxidation resistant heat resistant steel according to claim 5, characterized in that: 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°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.

8. The method for preparing high temperature oxidation resistant heat resistant steel according to claim 7, characterized in that: The time of the first preheating treatment is 30 minutes to 60 minutes, the time of the second preheating treatment is 30 minutes to 60 minutes, and the time of the diffusion treatment is 1 hour to 10 hours.

9. Use of the high temperature oxidation resistant heat resistant steel according to any one of claims 1 to 4 in the preparation of high temperature workpieces.

10. The use according to claim 9, characterized in that: The high-temperature workpiece is an internal lining plate of a steam turbine unit, a discharging grate plate of a cement plant or a hanging plate of a supercritical generator unit.

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