Protective coating material for high-temperature heating surface of power station boiler and preparation method of protective coating material

Abstract

The embodiment of the invention provides a protective coating material for a high-temperature heating surface of a power station boiler and a preparation method of the protective coating material. The protective coating material comprises: 0.3 wt% to 0.60 wt% of C; 18.00 wt% to 25.0 wt% of Cr; 1.0 wt% to 3.0 wt% of B; 2.0 wt% to 3.5 wt% of Si; 2.0 wt% to 2.5 wt% of Nb; 0.1 wt% to 0.8 wt% of Ti; and the balance of Ni or Fe. According to the embodiment of the invention, various carbon-fixing and boron-fixing elements are adopted, so that free carbon and boron in the coating are combined prior to Cr, Nb, Ti and the like to form borides or carbides, and the diffusion concentration of the borides or carbides is reduced. According to the self-fluxing alloy, Nb and Ti partially replace high Cr content in traditional self-fluxing alloy, and decomposition of carbides at high temperature can be prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of anti-corrosion and wear-resistant coatings for high-temperature heating surfaces of power station boilers, and in particular relates to a protective coating material for high-temperature heating surfaces of power station boilers and a preparation method thereof. Background Art

[0002] The heating surfaces of power station boilers mainly include water-cooled walls, superheaters, reheaters and economizers. According to statistics, more than 80% of coal-fired power station boilers in my country have different degrees of corrosion problems on the heating surfaces. Corrosion can cause thinning or perforation of the tube wall, which can easily cause accidents such as tube bursts and leaks, resulting in unplanned shutdown of the unit, which will seriously affect the safety and economy of the operation of thermal power units and the safe production and dispatching of the entire power grid. In recent years, in order to promote the consumption of new energy, coal-fired units, as the main power generation, have been widely involved in deep peak regulation. The low-load conditions during the peak regulation process have caused the corrosion of the boiler heating surface to increase and the frequency of tube bursts to increase. On the other hand, in order to adapt to the marketization of coal prices, many coal-fired power plants have implemented coal blending. The blending of high-sulfur, high-chlorine, high-alkali coal or biomass has led to increased corrosiveness of boiler flue gas, frequent tube bursts in the boiler, and endangered the safe operation of the boiler. In this context, due to the high porosity of traditional arc spray coatings, the corrosive medium enters the interface between the coating and the substrate through the pores of the coating during long-term service, thereby causing substrate corrosion. At the same time, arc spray coatings are consumed quickly, so conventional arc spray coatings cannot meet the long-term safe, stable and efficient power generation requirements of power plants.

[0003] Laser cladding coatings have the characteristics of high bonding strength, dense coatings, and excellent wear and corrosion resistance. They have gradually become one of the advanced manufacturing methods for surface coatings of industrial equipment. In recent years, they have been promoted and applied to a certain extent in the fields of thermal power generation or biomass waste power generation. The coating on the surface of the heating surface of the boiler tube in the power station is required to have high corrosion resistance and wear resistance, usually a nickel-based self-fluxing alloy or a composite coating of nickel-based alloy and metal ceramic materials. In order to improve the process performance and corrosion resistance and wear resistance of the coating, it is usually necessary to add a large amount of elements such as C and B to the coating material. Due to the metallurgical bonding formed between the laser cladding coating and the substrate, this metallurgical bonding coating makes it easy for C and B elements with small atomic radius to diffuse through the metallurgical bonding interface during long-term service, and causes the hardness of the substrate near the interface to increase and the high-temperature service strength of the substrate to decrease.

[0004] Therefore, in order to prevent the interdiffusion between the laser cladding coating and the substrate and cause the degradation of the performance of the substrate and the coating, the present invention provides a coating that is not prone to interdiffusion during long-term high-temperature service and a preparation method thereof. Summary of the invention

[0005] The embodiments of the present invention aim to at least solve the technical problem in the prior art that the long-term high-temperature service coating diffuses with the furnace tube body, causing the furnace tube performance to decrease, and propose a protective coating material for the high-temperature heating surface of a power station boiler and a preparation method thereof.

[0006] In a first aspect, an embodiment of the present invention provides a protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0007] 0.3 wt% to 0.60 wt% C;

[0008] 18.00wt%~25.0wt%Cr;

[0009] 1.0 wt% to 3.0 wt% of B;

[0010] 2.0 wt% to 3.5 wt% Si;

[0011] 2.0 wt% to 2.5 wt% Nb;

[0012] 0.1 wt% to 0.8 wt% Ti;

[0013] The balance is Ni or Fe.

[0014] In some possible embodiments, when the Cr content is low, the Nb and Ti contents are high.

[0015] When the Cr content is relatively high, there is no requirement for Nb to be within the above range, but the Ti content is relatively low.

[0016] In some possible embodiments, when the coating is used in a severe corrosive environment, Ni is selected as the main element, and when it is used in a wear environment, Fe is selected as the main element.

[0017] In some possible embodiments, the protective coating material is an aerosolized powder material, and the particle size range of the material is 100 μm to 250 μm.

[0018] In a second aspect, an embodiment of the present invention provides a method for preparing a protective coating for a high temperature heating surface of a power station boiler, using the protective coating material described above.

[0019] The law includes:

[0020] Grind and clean the corrosion products and old coatings on the surface of the boiler heating surface, and clean the dirt on the surface of the heating surface;

[0021] The boiler heating surface is heated by flame or induction to make the surface temperature reach the target temperature;

[0022] A laser with a preset light output power is used to prepare a coating of a preset thickness by cladding on the high-temperature heating surface of the boiler.

[0023] In some possible embodiments, the target temperature ranges from 100°C to 300°C.

[0024] In some possible embodiments, the output light power ranges from 800W to 4000W.

[0025] In some possible embodiments, the coating has a thickness ranging from 0.6 mm to 1.6 mm.

[0026] In some possible embodiments, the method includes:

[0027] Use sandblasting to clean the corrosion products and old coatings on the boiler heating surface, and clean the dirt on the heating surface;

[0028] Spraying a coating of a preset thickness on the surface of the boiler heating surface by flame spraying;

[0029] The coating surface is heated by a flame remelting gun or a high-frequency induction heating gun to remelt the coating and form a dense coating.

[0030] In some possible embodiments, the coating has a thickness ranging from 0.8 mm to 1.2 mm.

[0031] The protective coating material for the high temperature heating surface of a power plant boiler and the preparation method thereof according to the embodiment of the present invention have the following advantages compared with the existing conventional self-fluxing alloy coating technology:

[0032] 1. The embodiment of the present invention adopts a variety of carbon-fixing and boron-fixing elements, so that the free carbon and boron in the coating are combined with Cr, Nb, Ti, etc. first to form borides or carbides, thereby reducing their diffusion concentration.

[0033] 2. The embodiment of the present invention partially replaces the high Cr content in the traditional self-fluxing alloy with Nb and Ti, which can prevent the decomposition of carbides at high temperatures. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0035] Unless otherwise specifically stated, the relative arrangement of the components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be understood that the techniques, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the techniques, methods and devices shown should be considered as part of the authorized specification. In all examples shown and discussed herein, any specific other examples may have different values.

[0036] In the description of the embodiments of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In the embodiments of the present invention, the schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in the embodiments of the present invention and the features of the different embodiments or examples, without contradiction.

[0037] An embodiment of the present invention provides a protective coating material for a high-temperature heating surface of a power station boiler, wherein the protective coating material includes: 0.3wt% to 0.60wt% C, 18.00wt% to 25.0wt% Cr, 1.0wt% to 3.0wt% B, 2.0wt% to 3.5wt% Si, 2.0wt% to 2.5wt% Nb, 0.1wt% to 0.8wt% Ti, and the remainder is Ni or Fe.

[0038] Compared with the existing conventional self-fluxing alloy coating technology, the protective coating material for the high-temperature heating surface of a power station boiler according to the embodiment of the present invention has the following advantages:

[0039] 1. The embodiment of the present invention adopts a variety of carbon-fixing and boron-fixing elements, so that the free carbon and boron in the coating are combined with Cr, Nb, Ti, etc. first to form borides or carbides, thereby reducing their diffusion concentration.

[0040] 2. The embodiment of the present invention partially replaces the high Cr content in the traditional self-fluxing alloy with Nb and Ti, which can prevent the decomposition of carbides at high temperatures.

[0041] The coating composition of the embodiment of the present invention adopts the following design ideas:

[0042] First, to ensure the wear resistance and corrosion resistance of the coating, a nickel-based alloy is selected, and a high content of Cr is used to promote the formation of a surface oxide film to improve the corrosion resistance of the coating. Secondly, in order to ensure the process performance of the coating and prevent cracking of the coating during the cladding process, the content of C, B, Si, etc. in the coating is strictly controlled. Thirdly, in order to prevent C and B from diffusing into the substrate during high-temperature service and causing degradation of the substrate performance, strong carbide and boride forming elements, as well as Cr, Nb, and Ti, are introduced into the coating. Cr is formed during the coating preparation process and during long-term high-temperature service. 23 C6, Nb2C / NbC, TiC, CrB, TiB and other carborides. At the same time, the addition of Nb and Ti can refine the grains of the cladding process and reduce the Cr 23 The continuity of C6 reduces the risk of cracking during the cladding process.

[0043] The main function of C is to form alloy carbides with a large number of carbide elements Cr, Nb, and Ti to improve the wear resistance of the coating, but in order to prevent the coating from cracking, its content is controlled at 0.3wt~0.60wt%. The role of B is to reduce the melting point of the material and improve the process performance. At the same time, it can form borides with Cr, Nb, etc. to improve the hardness of the coating. The content is controlled at 1.0wt~3.0wt%.

[0044] Si reduces the melting point of the material, improves the process performance, and prevents the oxidation of alloy elements. The content is controlled at 2.0wt~3.5wt%. Cr is the main element for forming the Cr2O3 oxide film with anti-corrosion protection effect. It is also a strong carbide-forming element that makes the material have a higher hardness after rapid laser cooling. The content is controlled at 18.00wt~25.0wt%. Nb is a strong carbide and boride-forming element that can absorb C and B elements and prevent the diffusion of C and B elements during the high-temperature service of the coating. The content is controlled at 2.0wt~2.5wt%.

[0045] In some embodiments, when the Cr content is relatively low, the Nb and Ti contents are relatively large; when the Cr content is relatively high, Nb is not required to be within the above range, but the Ti content is relatively low.

[0046] In some embodiments, when the coating is used in a severely corrosive environment, Ni is selected as the main element, and when it is used in a wear environment, Fe is selected as the main element. By adding elements such as C, Cr, B, Si, Nb, and Ti, the laser cladding process performance of the material is greatly improved. At the same time, Cr, Nb, and Ti have good carboride formation capabilities, which can fix C, B and other easily diffusible elements in the coating, not only improving the hardness of the coating, but also effectively preventing the coating and the base material from interdiffusion during the long-term service of the coating, thereby reducing the high-temperature strength of the furnace tube.

[0047] In some embodiments, the protective coating material is an aerosolized powder material, and the particle size range of the material is 100 μm to 250 μm.

[0048] The coating composition of the present invention is described below in several examples.

[0049] Embodiment 1:

[0050] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0051] 0.3wt% C, 25.0wt% Cr, 3.0wt% B, 3.5wt% Si, 2.5wt% Nb, 0.8wt% Ti, and the balance is Ni or Fe.

[0052] Embodiment 2:

[0053] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0054] 0.6wt% C, 18.0wt% Cr, 3.0wt% B, 3.5wt% Si, 2.5wt% Nb, 0.8wt% Ti, and the balance is Ni or Fe.

[0055] Embodiment 3:

[0056] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0057] 0.6wt% C, 25.0wt% Cr, 1.0wt% B, 3.5wt% Si, 2.5wt% Nb, 0.8wt% Ti, and the balance is Ni or Fe.

[0058] Embodiment 4:

[0059] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0060] 0.6wt% C, 25.0wt% Cr, 3.0wt% B, 2.0wt% Si, 2.5wt% Nb, 0.8wt% Ti, and the balance is Ni or Fe.

[0061] Embodiment 5:

[0062] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0063] 0.6wt% C, 25.0wt% Cr, 3.0wt% B, 3.5wt% Si, 2.0wt% Nb, 0.8wt% Ti, and the balance is Ni or Fe.

[0064] Embodiment 6:

[0065] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0066] 0.6wt% C, 25.0wt% Cr, 3.0wt% B, 3.5wt% Si, 2.5wt% Nb, 0.1wt% Ti, and the balance is Ni or Fe.

[0067] Embodiment 7:

[0068] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0069] 0.6wt% C, 18.0wt% Cr, 3.0wt% B, 3.5wt% Si, 2.5wt% Nb, 0.8wt% Ti, and the balance is Ni or Fe.

[0070] Embodiment 8:

[0071] A protective coating material for a high-temperature heating surface of a power station boiler, the protective coating material comprising:

[0072] 0.6wt% C, 25.0wt% Cr, 3.0wt% B, 3.5wt% Si, 2.0wt% Nb, 0.1wt% Ti, and the balance is Ni or Fe.

[0073] It should be understood that the embodiments of the present invention are not limited to the above-mentioned embodiments 1 to 8. Those skilled in the art can make any combination according to the components included in the protective coating and their content ranges, and this embodiment does not limit this.

[0074] In a second aspect, an embodiment of the present invention provides a method for preparing a protective coating for a high-temperature heating surface of a power station boiler, using the protective coating material described above. For details, please refer to the relevant records above and will not be described in detail here. The method comprises:

[0075] Grind and clean the corrosion products and old coatings on the surface of the boiler heating surface, and clean the dirt on the heating surface. Use flame heating or induction heating to heat the boiler heating surface to make the surface temperature reach the target temperature. Use a laser with a preset light output power to prepare a coating of a preset thickness on the high-temperature heating surface of the boiler.

[0076] In some embodiments, the target temperature ranges from 100° C. to 300° C. The light output power ranges from 800 W to 4000 W. The thickness of the coating ranges from 0.6 mm to 1.6 mm.

[0077] In addition to the above method for preparing the protective coating, the coating can also be prepared by the following method:

[0078] Use sandblasting to clean the corrosion products and old coatings on the surface of the boiler heating surface, and clean the dirt on the heating surface. Use flame spraying to spray a coating of preset thickness on the surface of the boiler heating surface. Use a flame remelting gun or a high-frequency induction heating gun to heat the coating surface, remelt the coating, and form a dense coating.

[0079] In some embodiments, the coating has a thickness ranging from 0.8 mm to 1.2 mm.

[0080] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A protective coating material for high temperature heating surface of a power station boiler, characterized in that: The protective coating material comprises: 0.3 wt% to 0.60 wt% C; 18.00wt%~25.0wt%Cr; 1.0 wt% to 3.0 wt% of B; 2.0 wt% to 3.5 wt% Si; 2.0 wt% to 2.5 wt% Nb; 0.1 wt% to 0.8 wt% Ti; The balance is Ni or Fe.

2. The protective coating material for high temperature heating surface of power station boiler according to claim 1, characterized in that: When the Cr content is low, the Nb and Ti contents take larger values; When the Cr content is relatively high, there is no requirement for Nb to be within the above range, but the Ti content is relatively low.

3. The protective coating material for high temperature heating surface of power station boiler according to claim 1, characterized in that: When the coating is used in a severely corrosive environment, Ni is selected as the main element. When it is used in a wear environment, Fe is selected as the main element.

4. The protective coating material for high temperature heating surface of a power station boiler according to any one of claims 1 to 3, characterized in that: The protective coating material is an aerosolized powder material, and the particle size range of the material is 100 μm to 250 μm.

5. A method for preparing a protective coating for a high-temperature heating surface of a power station boiler, characterized in that: Using the protective coating material according to any one of claims 1 to 4, the method comprises: Grind and clean the corrosion products and old coatings on the surface of the boiler heating surface, and clean the dirt on the surface of the heating surface; The boiler heating surface is heated by flame or induction to make the surface temperature reach the target temperature; A laser with a preset light output power is used to prepare a coating of a preset thickness by cladding on the high-temperature heating surface of the boiler.

6. The method for preparing a protective coating for a high temperature heating surface of a power station boiler according to claim 5, characterized in that: The target temperature range is 100°C to 300°C.

7. The method for preparing a protective coating for a high temperature heating surface of a power station boiler according to claim 5, characterized in that: The light output power ranges from 800W to 4000W.

8. The method for preparing a protective coating for a high temperature heating surface of a power station boiler according to claim 5, characterized in that: The thickness of the coating ranges from 0.6 mm to 1.6 mm.

9. A method for preparing a protective coating for a high-temperature heating surface of a power station boiler, characterized in that: Using the protective coating material according to any one of claims 1 to 4, the method comprises: Use sandblasting to clean the corrosion products and old coatings on the boiler heating surface, and clean the dirt on the heating surface; Spraying a coating of a preset thickness on the surface of the boiler heating surface by flame spraying; The coating surface is heated by a flame remelting gun or a high-frequency induction heating gun to remelt the coating and form a dense coating.

10. The method for preparing a protective coating for a high temperature heating surface of a power station boiler according to claim 9, characterized in that: The thickness of the coating ranges from 0.8 mm to 1.2 mm.