A cermet coating resistant to high-temperature sulfur and chlorine corrosion and abrasion and its application

Abstract

The present invention provides a cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear, and a preparation method thereof. The coating includes a matrix bonding phase, a ceramic phase, and an intermetallic compound. This cermet coating contains a matrix bonding phase, a ceramic phase, and an intermetallic compound. The matrix bonding phase is a nickel-based alloy phase, the ceramic phase is mainly TiN, and the intermetallic compound includes TiNi. The present invention uses a self-propagating high-temperature synthesis (SHS) reaction flame spraying technology to spray a cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear on the surface of the tube screen, and then sends it into a trolley furnace for homogenization annealing treatment. The cermet coating on the surface of the tube screen is metallurgically bonded to the base material, with high bonding strength. The nickel-chromium matrix bonding phase, ceramic phase, and intermetallic compound in the cermet coating have extremely high corrosion resistance in a high-temperature environment containing oxygen, sulfur, and chlorine. At the same time, the coating has both high toughness and high hardness and can be used for a long time under conditions of thermal cycling and impact wear.

Description

Technical Field

[0001] The invention belongs to the technical field of metal ceramic coatings, and in particular relates to a metal ceramic coating resistant to high temperature sulfur and chlorine corrosion and wear and application thereof. Background Art

[0002] At present, large-scale power station pulverized coal boilers have serious high-temperature corrosion and slagging on the furnace heating surface due to factors such as high sulfur content in the coal entering the furnace and oxygen-deficient and low-nitrogen combustion in the furnace. The high concentration of reducing H2S gas in the flue gas and the sulfides and sulfates adhering to the surface of the heating surface tubes continuously damage the protective oxide film on the surface of the tubes, and directly react with Fe in a complex chemical reaction, continuously corroding the heating surface tubes, resulting in excessive thinning of the tube wall and frequent tube bursts, which seriously affect the economy and safety of boiler operation.

[0003] As environmental protection requirements become increasingly stringent, the country has begun to build large-scale waste incineration power plants to treat domestic waste by incineration. When domestic waste is incinerated at high temperatures in the incineration boiler, a large amount of corrosive flue gas such as HCl, HF, SO2 and dust containing a large amount of alkali metal chlorides and sulfates will be generated, which will cause serious damage to the protective oxide film on the water-cooled wall and superheater tube surface of the boiler, and continuously erode and wear the tube surface, resulting in serious thinning of the tube wall and tube bursting, which seriously affects the safe and stable operation of the waste power plant.

[0004] At present, the boiler water-cooled wall tube screen protection solution is mainly to conduct online supersonic arc spraying of alloy coatings on the heating surface tubes. The advantage of this process is that it can be constructed on site, the process is relatively simple, and it has a certain high-temperature corrosion resistance effect. However, due to the relatively harsh on-site environment, it is difficult for the sandblasting pretreatment of the heating surface tube surface to reach a level above Sa2.5. The bonding strength between the coating and the tube is not high, the coating porosity is high, and the corrosive medium easily penetrates into the bonding surface between the coating and the substrate to cause interface corrosion, resulting in coating peeling and failure. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a metal ceramic coating resistant to high temperature sulfur and chlorine corrosion and wear and application thereof, wherein the coating is metallurgically bonded to the substrate and has a high bonding strength.

[0006] The invention provides a metal ceramic coating resistant to high temperature sulfur and chlorine corrosion and wear, comprising a substrate bonding phase, a ceramic phase and an intermetallic compound.

[0007] In the present invention, the matrix bonding phase is a nickel-based alloy phase.

[0008] In the present invention, the nickel-based alloy phase is a nickel-chromium alloy phase or a nickel-chromium-aluminum-yttrium alloy phase.

[0009] In the present invention, the ceramic phase is mainly TiN and AlN.

[0010] In the present invention, the intermetallic compounds are mainly TiNi, TiAl and AlNi.

[0011] In the present invention, the raw materials used for preparing the cermet coating include alloy powder and metal elemental powder;

[0012] The alloy powder is nickel-chromium alloy or nickel-chromium-aluminum-yttrium alloy;

[0013] The metal elemental powder is selected from titanium powder.

[0014] In the present invention, the mass ratio of nickel to chromium in the nickel-chromium alloy is 80:20;

[0015] The mass ratio of nickel, chromium, aluminum and yttrium in the nickel-chromium-aluminum-yttrium alloy is 66:22:11:1.

[0016] In the present invention, the mass ratio of the alloy powder to the total mass of the aluminum powder and titanium powder is (60:40) to (70:30).

[0017] In the present invention, in a high-temperature sulfur corrosion environment, the alloy powder is nickel-chromium alloy, and the mass ratio of the nickel-chromium alloy powder to the titanium powder is (85:15) to (75:25);

[0018] In a high-temperature sulfur and chlorine corrosion environment, the metal elemental powder further includes aluminum powder, the alloy powder is nickel-chromium-aluminum-yttrium alloy, the mass ratio of the nickel-chromium-aluminum-yttrium alloy to the metal elemental powder is 80:20 to 70:30, and the mass ratio of the aluminum powder to the titanium powder is 3:7 to 6:4.

[0019] In the present invention, the raw materials are prepared by a self-propagating high-temperature synthesis reaction flame spraying process;

[0020] The conditions of the self-propagating high-temperature synthesis reaction flame spraying process include:

[0021] The powder-carrying carrier gas uses N2 with a purity of more than 99%, the oxygen pressure is 0.4 to 0.6 MPa, the acetylene pressure is 0.07 to 0.11 MPa, and a carbide flame is maintained, and the spraying distance is 140 to 200 mm.

[0022] The present invention provides a boiler tube panel, and the surface of the boiler tube panel is coated with the cermet coating with high temperature sulfur and chlorine corrosion resistance and wear resistance described in the above technical solution.

[0023] The present invention provides a cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear, which comprises a matrix bonding phase, a ceramic phase and an intermetallic compound. This cermet coating contains a matrix bonding phase, a ceramic phase and an intermetallic compound. The matrix bonding phase is a nickel-based alloy phase, the ceramic phase is mainly TiN, and the intermetallic compound includes TiNi. The present invention adopts the self-propagating high-temperature synthesis (SHS) reaction flame spraying technology to spray a cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear on the surface of the tube screen, and then sends it into a trolley furnace for homogenization annealing treatment. The cermet coating on the surface of the tube screen is metallurgically bonded to the substrate, with high bonding strength. The nickel-chromium matrix bonding phase, ceramic phase and intermetallic compound in the cermet coating have extremely high corrosion resistance in a high-temperature environment containing oxygen, sulfur and chlorine. At the same time, the coating has both high toughness and high hardness and can be used for a long time under working conditions of thermal cycling and impact wear. Description of the Drawings

[0024] Figure 1 It is a scanning electron microscope picture of the longitudinal section of the cermet coating prepared in Example 1 of the present invention and the substrate. Detailed Embodiments

[0025] The present invention provides a cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear, which comprises a matrix bonding phase, a ceramic phase and an intermetallic compound.

[0026] In the present invention, the matrix bonding phase is a nickel-based alloy phase, and the nickel-based alloy phase is a nickel-chromium alloy phase or a nickel-chromium-aluminum-yttrium alloy phase.

[0027] In the present invention, the ceramic phase is mainly TiN, and preferably further includes AlN.

[0028] In the present invention, the intermetallic compound is mainly TiNi, and preferably further includes TiAl and AlNi.

[0029] In the present invention, the raw materials used for preparing the cermet coating include alloy powder and metal elemental powder;

[0030] The alloy powder is a nickel-chromium alloy or a nickel-chromium-aluminum-yttrium alloy;

[0031] The metal elemental powder is selected from titanium powder.

[0032] In a specific embodiment of the present invention, the mass ratio of nickel to chromium in the nickel-chromium alloy is 80:20;

[0033] The mass ratio of nickel, chromium, aluminum and yttrium in the nickel-chromium-aluminum-yttrium alloy is 66:22:11:1.

[0034] In the present invention, the mass ratio of the alloy powder to the total mass of the aluminum powder and titanium powder is (60:40)~(70:30).

[0035] In a high-temperature sulfur corrosion environment, the alloy powder is a nickel-chromium alloy, and the mass ratio of the nickel-chromium alloy powder to the titanium powder is (85:15) - (75:25);

[0036] In a high-temperature sulfur and chlorine corrosion environment, the metal elemental powder further includes aluminum powder, the alloy powder is a nickel-chromium-aluminum-yttrium alloy, the mass ratio of the nickel-chromium-aluminum-yttrium alloy to the metal elemental powder is 80:20 - 70:30, and the mass ratio of the aluminum powder to the titanium powder is 3:7 - 6:4.

[0037] In the present invention, the raw materials are prepared by a self-propagating high-temperature synthesis reaction flame spraying process;

[0038] The conditions of the self-propagating high-temperature synthesis reaction flame spraying process include:

[0039] The powder-carrying carrier gas is N2 with a purity of more than 99%, the oxygen pressure is 0.4 - 0.6 MPa, the acetylene pressure is 0.07 - 0.11 MPa, and it remains a carburizing flame, and the spraying distance is 140 - 200 mm.

[0040] In the present invention, by improving the traditional supersonic flame spraying equipment and effectively combining it with the self-propagating high-temperature synthesis (SHS) technology, using a nitrogen powder feeding system and a reactive mixed powder system, during the spraying process, the raw material system undergoes a strong exothermic reaction, which can not only in-situ synthesize high-melting-point ceramic phases (including TiN, AlN) and intermetallic compounds (including TiNi, TiAl, AlNi) that are difficult to prepare by conventional techniques, but also greatly increase the temperature of the flame, making the flame turn incandescent, and significantly widen and lengthen the high-temperature zone. The nickel-chromium-based alloy powder is completely melted, and the reaction products are in a molten or semi-molten state. After the molten droplets collide with the substrate, they deform and spread into a lamellar coating. Some reactions still continue after the molten droplets reach the substrate, thereby obtaining a dense metal-ceramic composite coating and improving the bonding strength between the coating and the substrate.

[0041] The present invention provides a boiler tube panel, and the surface of the boiler tube panel is coated with the high-temperature sulfur and chlorine corrosion-resistant and wear-resistant metal-ceramic coating described in the above technical solution.

[0042] During coating, the preheating temperature of the boiler tube panel is 200 - 300 °C, and the preheating time is 20 - 30 min; after spraying, the tube panel is sent into a trolley furnace for annealing treatment, the annealing temperature is 500 - 600 °C, and the holding time is 2 - 4 h.

[0043] In the present invention, the boiler tube panel is preferably prepared according to the following steps:

[0044] The alloy powder is wet-mixed with the metal elemental powder and absolute ethanol, dried and sieved to obtain a mixed powder;

[0045] After preheating the boiler tube panel with surface sandblasting pretreatment, the mixture is sprayed on the surface and then annealed to obtain the boiler tube panel.

[0046] In the present invention, the alloy powder is nickel-chromium alloy or nickel-chromium-aluminum-yttrium alloy; in a specific embodiment, the alloy powder is a commercially available Ni-Cr alloy with a particle size of 325 mesh and a mass ratio of 80:20; or a Ni-Cr-Al-Y alloy with a mass ratio of 66:22:11:1.

[0047] In the present invention, the dried raw materials are preferably sieved through a 325-mesh sieve. After surface sandblasting pretreatment of the boiler tube panel, the surface reaches a level above Sa2.5.

[0048] In the present invention, the boiler tube panel with surface sandblasting pretreatment is sent into a trolley furnace for preheating. The preheating temperature is 200-300 °C, and the preheating time is 20-30 min. During spraying, high-purity N2 is used as the powder-carrying gas in the present invention. During supersonic flame spraying, the high-temperature flame ignites the self-propagating synthesis reaction between the metal powder and N2, releasing a large amount of reaction heat; the oxygen pressure during supersonic flame spraying is 0.4-0.6 MPa, the acetylene pressure is 0.07-0.11 MPa, and it remains a carbide flame. The spraying distance is 140-200 mm.

[0049] The sprayed tube panel is sent into a trolley furnace for homogenization annealing treatment and cooled in the furnace. The annealing temperature is 500-600 °C, and the holding time is 2-4 h.

[0050] The present invention combines supersonic flame spraying with self-propagating high-temperature synthesis (SHS) technology. Through the high-temperature reaction of the spraying particles and the carrier gas, a large amount of reaction heat is released, increasing the temperature of the flame. The high-temperature zone of the flame becomes wider and longer, which is more conducive to the melting of the spraying particles. By adding metal particles to the spraying raw material powder, ceramic particles and intermetallic compounds with high hardness, corrosion resistance, and wear resistance are in-situ generated, improving the density, strength, and hardness of the cermet coating. In the high-temperature oxidation environment, the intermetallic compounds combine with oxygen atoms to form dense Al2O3 and TiO2 protective films in the coating. Coupled with the fine TiN and AlN ceramic particles dispersed in the coating, it ensures that the cermet coating has excellent resistance to high-temperature sulfur and chlorine corrosion and wear resistance. Further, the in-situ generated fine TiN particles have self-lubricating properties, which can slow down the coking and slagging on the surface of the boiler tube panel and further improve the molten salt corrosion resistance of the cermet coating.

[0051] After the reaction product droplets reach the substrate of the boiler tube panel, part of the self-propagating reaction still continues to release heat. A solid-liquid reaction occurs between the droplets and the substrate, and the droplets and the substrate maintain good wettability, ultimately improving the bonding strength between the cermet coating and the substrate.

[0052] The present invention can prepare boiler tube screens suitable for specific working conditions by flexibly changing the composition of nickel-chromium alloy powder and the addition amounts of aluminum powder and titanium powder. The process involved in the present invention is simple and suitable for mass customization of boiler tube screens adapted to various application scenarios.

[0053] In order to further illustrate the present invention, the following describes in detail a cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear and its application provided by the present invention in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0054] Example 1

[0055] A cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear and a boiler tube screen coated with this coating. The cermet coating is composed of a nickel-chromium alloy matrix binder phase, a TiN ceramic phase, and a TiNi intermetallic compound. The boiler tube screen coated with this coating is prepared according to the following steps:

[0056] The first step: Weigh nickel-chromium alloy powder and titanium powder according to a weight ratio of 85:15, add absolute ethanol for wet mixing, dry after mixing evenly, and pass through a 325-mesh sieve;

[0057] The second step: Perform surface sandblasting pretreatment on the already welded boiler tube screen in a sandblasting room, and the surface reaches a level of Sa2.5 or above;

[0058] The third step: Send the boiler tube screen after sandblasting pretreatment into a trolley furnace for preheating, with a preheating temperature of 200°C and a holding time of 30 min;

[0059] The fourth step: Use nitrogen as the powder feeding gas to carry out self-propagating high-temperature synthesis reaction flame spraying, with an oxygen pressure of 0.4 MPa and an acetylene pressure of 0.07 MPa;

[0060] The fifth step: Send the already sprayed tube screen into a trolley furnace for homogenization annealing treatment, with an annealing temperature of 500°C, a holding time of 2 h, and furnace cooling.

[0061] Example 2

[0062] A cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear and a boiler tube screen coated with this coating. The cermet coating is composed of a nickel-chromium-aluminum-yttrium alloy matrix binder phase, TiN and AlN ceramic phases, and TiNi, TiAl, and AlNi intermetallic compounds. The boiler tube screen coated with this coating is prepared according to the following steps:

[0063] The first step: Weigh nickel-chromium-aluminum-yttrium alloy powder, aluminum powder, and titanium powder according to a weight ratio of 70:30, where the mass ratio of aluminum powder to titanium powder is 5:5, add absolute ethanol for wet mixing, dry after mixing evenly, and pass through a 325-mesh sieve;

[0064] Step 2: Perform surface sandblasting pretreatment on the welded boiler tube panel in a sandblasting room until the surface reaches a level of Sa2.5 or above.

[0065] Step 3: Feed the boiler tube panel after sandblasting pretreatment into a trolley furnace for preheating. The preheating temperature is 300°C, and the holding time is 20 min.

[0066] Step 4: Use nitrogen as the powder feeding gas to carry out self-propagating high-temperature synthesis reaction flame spraying. The oxygen pressure is 0.6 MPa, and the acetylene pressure is 0.11 MPa.

[0067] Step 5: Feed the sprayed tube panel into a trolley furnace for homogenization annealing treatment. The annealing temperature is 600°C, the holding time is 2 h, and it is cooled in the furnace.

[0068] Example 3

[0069] A cermet coating resistant to high-temperature sulfur and chlorine corrosion and wear, and a boiler tube panel coated with this coating. The cermet coating consists of a nickel-chromium-aluminum-yttrium alloy matrix bonding phase, TiN and AlN ceramic phases, and TiNi, TiAl, and AlNi intermetallic compounds. The boiler tube panel coated with this coating is prepared according to the following steps:

[0070] Step 1: Weigh nickel-chromium-aluminum-yttrium alloy powder, aluminum powder, and titanium powder according to a weight ratio of 80:20, where the mass ratio of aluminum powder to titanium powder is 3:7. Add absolute ethanol for wet mixing. After mixing evenly, dry and pass through a 325-mesh sieve.

[0071] Step 2: Perform surface sandblasting pretreatment on the welded boiler tube panel in a sandblasting room until the surface reaches a level of Sa2.5 or above.

[0072] Step 3: Feed the boiler tube panel after sandblasting pretreatment into a trolley furnace for preheating. The preheating temperature is 300°C, and the holding time is 30 min.

[0073] Step 4: Use nitrogen as the powder feeding gas to carry out self-propagating high-temperature synthesis reaction flame spraying. The oxygen pressure is 0.5 MPa, and the acetylene pressure is 0.09 MPa.

[0074] Step 5: Feed the sprayed tube panel into a trolley furnace for homogenization annealing treatment. The annealing temperature is 550°C, the holding time is 3 h, and it is cooled in the furnace.

[0075] Comparative Example 1

[0076] Use the supersonic arc process to spray a commonly used high-temperature sulfur corrosion-resistant PS45 alloy coating (Cr: 43%, Ti: 0.3%, Ni balance) on the boiler tube panel, and take samples for performance testing.

[0077] Table 1 Performance test results of boiler tube screens in the examples and comparative examples

[0078] Project Surface microhardness HRC Coating adhesion MPa <![CDATA[Resistant to molten salt corrosion (80wt% Na2SO4 + 20wt% NaCl, 750 °C), sample weight gain in mg / cm after 80 h 2 > Example 1 52.5 62.6 3.1 Example 2 60.5 67.3 2.2 Example 3 56.0 65.1 2.7 Comparative Example 1 39.5 45.3 4.6

[0079] As can be seen from the above examples, the present invention provides a cermet coating resistant to high-temperature sulfur, chlorine corrosion and wear, including a matrix bonding phase, a ceramic phase and an intermetallic compound. The cermet coating contains a matrix bonding phase, a ceramic phase and an intermetallic compound. The matrix bonding phase is a nickel-based alloy phase, the ceramic phase is mainly TiN, and the intermetallic compound includes TiNi. The present invention adopts the self-propagating high-temperature synthesis (SHS) reaction flame spraying technology to spray a cermet coating resistant to high-temperature sulfur, chlorine corrosion and wear on the surface of the tube screen, and then sends it into a trolley furnace for homogenization annealing treatment. The cermet coating on the surface of the tube screen is metallurgically bonded to the substrate, with high bonding strength. The experimental results show that: the surface hardness of the coating is 52.5 - 60.5 HRC; the coating bonding strength is 62.6 - 67.3 MPa; it is resistant to molten salt corrosion at 80 wt% Na2SO4 + 20 wt% NaCl and 750 °C for 80 h, and the sample weight gain is 2.2 - 3.1 mg / cm 2 。

[0080] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A cermet coating resistant to high-temperature sulfur corrosion and abrasion, characterized in that, It includes a matrix bonding phase, a ceramic phase and an intermetallic compound; The ceramic phase is TiN, and the intermetallic compound is TiNi; the matrix bonding phase is a nickel-chromium alloy phase; The raw materials used for preparing the cermet coating include alloy powder and metal elemental powder; the mass ratio of the alloy powder to the metal elemental powder is (60:40)~(70:30); The metal elemental powder is selected from titanium powder; the alloy powder is nickel-chromium alloy; the mass ratio of nickel to chromium in the nickel-chromium alloy is 80:20; The corrosion environment is a high-temperature sulfur corrosion environment, and the mass ratio of the nickel-chromium alloy powder to the titanium powder is (85:15)~(75:25); The cermet coating is prepared by a self-propagating high-temperature synthesis reaction flame spraying process; The conditions of the self-propagating high-temperature synthesis reaction flame spraying process include: The powder-carrying carrier gas uses N2 with a purity of more than 99%, the oxygen pressure is 0.4~0.6 MPa, the acetylene pressure is 0.07~0.11 MPa, and it is maintained as a carburizing flame, and the spraying distance is 140~200 mm.

2. A cermet coating resistant to high-temperature sulfur and chlorine corrosion and abrasion, characterized in that, It includes a matrix bonding phase, a ceramic phase and an intermetallic compound; The ceramic phase is TiN and AlN, the intermetallic compounds are TiNi, TiAl and AlNi, and the matrix bonding phase is a nickel-chromium-aluminum-yttrium alloy phase; The raw materials used for preparing the cermet coating include alloy powder and metal elemental powder; the mass ratio of the alloy powder to the metal elemental powder is (60:40)~(70:30); The metal elemental powders are selected from titanium powder and aluminum powder; the alloy powder is nickel-chromium-aluminum-yttrium alloy; the mass ratio of nickel, chromium, aluminum and yttrium in the nickel-chromium-aluminum-yttrium alloy is 66:22:11:1; The corrosion environment is a high-temperature sulfur and chlorine corrosion environment, the mass ratio of the nickel-chromium-aluminum-yttrium alloy to the metal elemental powder is 80:20~70:30, and the mass ratio of the aluminum powder to the titanium powder is 3:7~6:4; The cermet coating is prepared by a self-propagating high-temperature synthesis reaction flame spraying process; The conditions of the self-propagating high-temperature synthesis reaction flame spraying process include: The powder-carrying carrier gas uses N2 with a purity of more than 99%, the oxygen pressure is 0.4~0.6 MPa, the acetylene pressure is 0.07~0.11 MPa, and it is maintained as a carburizing flame, and the spraying distance is 140~200 mm.

3. A boiler tube panel, characterized in that, The surface of the boiler tube panel is coated with a cermet coating with high temperature sulfur corrosion resistance and wear resistance described in Claim 1 or a cermet coating with high temperature sulfur and chlorine corrosion resistance and wear resistance described in Claim 2.

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