High-temperature-resistant composite heat-absorbing coating taking spinel pigment as light absorbing agent and preparation process of high-temperature-resistant composite heat-absorbing coating

Abstract

The invention relates to a solar photo-thermal power generation technology, in particular to a high-temperature-resistant composite heat absorption coating with spinel pigment as a light absorption agent and a preparation process of the high-temperature-resistant composite heat absorption coating, and belongs to the field of solar heat utilization. The preparation method comprises the following steps: firstly, depositing a NiCrAlY coating on a Ni-based high-temperature alloy matrix as a bonding layer through a plasma spraying technology; then, the NiCrAlY coating is coated with a CuCrMnO4 heat absorption coating through a spraying process; and finally, performing heat treatment to form the composite heat absorption coating with good binding force on the substrate. Compared with an existing conventional heat absorption coating, the heat absorption coating has the advantages of being good in process repeatability, controllable in component, easy to industrially produce and the like, and the prepared coating is compact in structure, high in stability and high in absorptivity. The bonding layer is added into a heat absorption coating system, the peeling or falling phenomenon caused by the difference of thermal expansion coefficients between the ceramic coating and the alloy can be effectively reduced, and the heat absorption coating has the long-term service performance at the high temperature.

Description

Technical Field

[0001] The invention relates to solar thermal power generation technology, and in particular to a high-temperature resistant composite heat-absorbing coating with spinel pigment as a light absorber and a preparation process thereof, and belongs to the field of solar thermal utilization. Background Art

[0002] Solar thermal power generation systems are expected to play an important role in my country's carbon peak and carbon neutrality process. Currently, most of the molten salt solar thermal power generation devices in service use nitrates as heat transfer and storage media. Their operating temperatures are relatively low, and the power generation efficiency and costs need to be improved urgently. The next generation of solar thermal collection technology (such as chloride molten salts, high-temperature molten salt corrosion-resistant alloys, supercritical carbon dioxide power generation, etc.) will increase the system temperature to 800°C, and is expected to achieve low-cost and efficient solar thermal power generation. However, the heat-absorbing coatings currently used have the disadvantages of easy shedding and low optical performance at this operating temperature. It is imperative to develop long-life, high-efficiency, and temperature-resistant solar heat-absorbing coatings.

[0003] The spinel structure formed by transition metals (such as Cu, Cr, Ni, Co, etc.) at high temperature has an appropriate energy gap and can effectively absorb energy in the 0.3-2.5μm band, and can be used as an absorber for solar selective coatings; at the same time, the spinel coating has good stability and meets the requirements of long-term service at high temperatures. However, spinel is a ceramic material, and the difference in thermal expansion coefficient between it and the base alloy will cause the coating to peel or fall off. MCrAlY (M=Ni, Co or Ni+Co) with high temperature oxidation corrosion resistance can be introduced as a bonding layer to improve the high temperature stability of the coating system.

[0004] Plasma spraying technology has the advantages of fast deposition speed and good coating adhesion, and can be used to prepare MCrAlY coatings. The coating method has the advantages of simple operation and simple equipment. It is a common method for preparing heat-absorbing coatings and is widely used in production practice and laboratory fields. Therefore, the preparation of heat-absorbing coatings by combining plasma spraying and spraying processes can improve the high-temperature stability of the coating while ensuring efficient light absorption capacity, which will provide a new path for improving the optical properties and thermal stability of heat-absorbing coatings. Summary of the invention

[0005] The purpose of the present invention is to provide a high-temperature resistant composite heat-absorbing coating with spinel pigment as a light absorber and a preparation process thereof. The high-temperature resistant composite heat-absorbing coating is prepared by a method combining plasma spraying and spraying processes. The preparation process has good repeatability and is easy to realize industrial production.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A preparation process for a high-temperature resistant composite heat-absorbing coating using spinel pigment as a light absorber comprises the following steps: firstly, a NiCrAlY coating is deposited on a Ni-based high-temperature alloy substrate as a bonding layer by plasma spraying technology; then, a coating containing the spinel pigment is evenly applied to the NiCrAlY coating by a spraying process to obtain a CuCrMnO4 heat-absorbing coating; finally, a heat treatment is performed to form a composite heat-absorbing coating with good bonding strength on the Ni-based high-temperature alloy substrate.

[0008] The preparation process of the high temperature resistant composite heat absorbing coating using spinel pigment as light absorber specifically comprises the following steps:

[0009] (1) Pretreatment of the substrate;

[0010] (2) NiCrAlY coating was deposited by plasma spraying technology;

[0011] (3) Pretreatment of NiCrAlY coating;

[0012] (4) Depositing the CuCrMnO4 heat absorbing coating by spraying process;

[0013] (5) Curing heat treatment.

[0014] The preparation process of the high-temperature resistant composite heat-absorbing coating with spinel pigment as light absorber, in step (1), the pretreatment process is: first, the substrate SiC sandpaper is polished until the fresh substrate is exposed, then 60-220 mesh alumina is used for sandblasting to a roughness Ra>4μm, and finally deionized water and alcohol ultrasonic cleaning are performed for 15-30min, and then rinsed with alcohol and dried.

[0015] The preparation process of the high-temperature resistant composite heat-absorbing coating with spinel pigment as a light absorber, in step (2), the process parameters for depositing the NiCrAlY coating using plasma spraying technology are: distance of 100-110 mm, voltage of 60-80 V, current of 500-600 A, hydrogen flow rate of 30-55 L / min, argon flow rate of 5-10 L / min, powder feeding amount of 10-20 rad / min, and the thickness of the obtained NiCrAlY coating is 50 μm±5 μm.

[0016] In the preparation process of the high-temperature resistant composite heat-absorbing coating with spinel pigment as light absorber, in step (3), the pretreatment process is: first, use 60-220 mesh alumina for sandblasting to a roughness Ra>4μm, then use deionized water and alcohol ultrasonic cleaning for 15-30min, and finally rinse with alcohol and dry.

[0017] In the preparation process of the high-temperature resistant composite heat-absorbing coating with spinel pigment as light absorber, in step (4), the coating composition and mass fraction used for depositing the CuCrMnO4 heat-absorbing coating are as follows: spinel pigment 5-20%, resin 60%-95%, curing agent 0-10%, solvent 0-10%.

[0018] The preparation process of the high temperature resistant composite heat absorbing coating using spinel pigment as light absorber, the general chemical formula of the spinel pigment is CuO·(Cr,Mn)2O3.

[0019] In the preparation process of the high-temperature resistant composite heat-absorbing coating with spinel pigment as light absorber, in step (5), the curing temperature is 250-500°C, the insulation time is 10min-1h, the heating rate is ≤10°C / min, and after the insulation is completed, it is cooled to room temperature with the furnace.

[0020] A high temperature resistant composite heat absorbing coating with spinel pigment as light absorber prepared by the method, wherein the thickness of the composite heat absorbing coating is 10 μm±2 μm.

[0021] The design idea of ​​the present invention is:

[0022] The present invention first deposits a NiCrAlY coating on a high-temperature alloy substrate by plasma spraying technology; then performs sandblasting pretreatment to give the NiCrAlY coating a certain degree of roughness; then uses a coating method to prepare a heat-absorbing coating; and finally performs heat treatment to form a composite heat-absorbing coating with good bonding force on the substrate. The present invention deposits a temperature-resistant heat-absorbing coating on a Ni-based high-temperature alloy substrate by combining plasma spraying technology with a spraying process. Compared with existing conventional heat-absorbing coatings, the heat-absorbing coating involved in the present invention has the advantages of good process repeatability, controllable composition, and easy industrial production. The prepared coating has a dense structure and exhibits high stability and high absorption rate performance.

[0023] Mn is used to modify CuCr2O4 spinel to further reduce the band gap, increase the cutoff wavelength and improve the absorptivity. Adding a bonding layer to the heat-absorbing coating system can effectively reduce the peeling or shedding phenomenon caused by the difference in thermal expansion coefficient between the ceramic coating and the alloy, and has long-term service performance under high temperature.

[0024] The present invention has the following advantages and beneficial effects:

[0025] 1. In the high temperature resistant composite heat absorbing coating of the present invention, the NiCrAlY coating is used as a bonding layer to improve the problem of mismatch of thermal expansion coefficients, as well as the problem of peeling or falling off of the heat absorbing coating when used at high temperatures.

[0026] 2. The high temperature resistant composite heat absorbing coating prepared by the present invention has a higher operating temperature. With the addition of NiCrAlY coating, the 800°C / 24h coating has a higher absorption rate, and the absorption rate remains stable and slightly improved without attenuation.

[0027] 3. The present invention adopts plasma spraying technology plus coating method to obtain high temperature resistant composite heat absorbing coating, which has the advantages of simple process, high production efficiency, controllable composition and thickness of coating, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The absorption spectrum of the composite heat-absorbing coating is shown in FIG. 1 , where the horizontal axis Wavelength is the wavelength, and the vertical axis Reflectance is the reflectivity (%). The reflectivity of the as-deposited coating is 96.35%, and the reflectivity after annealing at 800° C. for 24 hours is 96.97%.

[0029] Figure 2 Surface (a) and cross-section (b) SEM morphologies of the deposited composite heat-absorbing coating.

[0030] Figure 3 Surface (a) and cross-section (b) SEM morphologies of the composite heat-absorbing coating after annealing.

[0031] Figure 4 The XRD graphs of the composite heat-absorbing coating before annealing (as-deposited) and after annealing at 800℃ for 24 hours are shown in Figure 1. In the figure, the horizontal axis 2θ is the diffraction angle (deg.), and the vertical axis Intensity is the relative intensity (au). DETAILED DESCRIPTION

[0032] Below, the present invention is further described in detail by examples.

[0033] Example 1

[0034] In this embodiment, a high-temperature resistant composite heat-absorbing coating is prepared on a Ni-based high-temperature alloy. The nominal composition of the Ni-based high-temperature alloy substrate used is (mass percentage): Cr 5.5%, W 26%, Mo 1%, Ti 0.7%, C 0.03%, Ni balance, and the sample size is 25mm×25mm×2mm.

[0035] Before deposition, the substrate sample was pretreated by grinding, sandblasting and cleaning, wherein: during grinding, SiC sandpaper was used to grind the substrate sample until the fresh substrate was exposed; during sandblasting, 150 mesh alumina (corundum sand) was used for sandblasting to a roughness of Ra6.3μm; during cleaning, deionized water and alcohol were ultrasonically cleaned for 15 minutes respectively, and finally rinsed with alcohol and dried for use; APS-2000 plasma spraying equipment was used to deposit the NiCrAlY coating. During the deposition process: the distance was 100mm, the voltage was 70V, the current was 540A, the hydrogen flow rate was 40L / min, the argon flow rate was 8L / min, the powder feeding amount was 15rad / min, and the thickness of the NiCrAlY coating was 50μm.

[0036] Before preparing the heat-absorbing coating by the coating method, the sample was sandblasted and cleaned for pretreatment. During sandblasting, 150 mesh alumina (corundum sand) was used for sandblasting to a roughness of Ra 6.3μm. During cleaning, deionized water and alcohol were used for ultrasonic cleaning for 20 minutes respectively, and finally rinsed with alcohol and dried for use. After pretreatment, the coating was evenly applied to the NiCrAlY coating by spraying to form a CuCrMnO4 heat-absorbing coating.

[0037] In this embodiment, the composition and mass fraction of the coating are as follows: 12% CuCrMn4 spinel pigment, 78% inorganic silicone resin, and 10% water.

[0038] The obtained composite heat-absorbing coating sample was heated to 250°C in a muffle furnace and cured for 20 minutes at a heating rate of 5°C / min. After the insulation, it was cooled to room temperature in the furnace to obtain a composite heat-absorbing coating with a coating thickness of about 17 μm.

[0039] In this embodiment, a composite heat-absorbing coating is deposited on the alloy substrate. The absorption rate of the coating is as follows: Figure 1 As shown. Figure 1 It can be seen that the absorption rate of the deposited coating is further improved after annealing.

[0040] like Figure 2 As shown, the surface and cross-sectional SEM morphology of the composite heat-absorbing coating before annealing. Figure 2 It can be seen that the coating surface and cross section are relatively dense before annealing, and the coating thickness is about 17 μm.

[0041] like Figure 3 As shown in Figure 2, the surface and cross-sectional SEM morphology of the composite heat-absorbing coating after annealing. Figure 3 It can be seen that after annealing, the coating structure is complete without obvious defects, and the coating thickness is about 17 μm.

[0042] like Figure 4 As shown in Figure 2, the XRD patterns of the composite heat-absorbing coating before and after annealing. Figure 4It can be seen that the back layer remains stable before and after annealing, and is still the CuCrMnO4 spinel phase. Affected by the XRD detection depth, the bonding layer phase is also measured, which is the typical phase Ni3Al of MCrAlY coating.

[0043] The results of the embodiment show that the composite heat-absorbing coating is deposited on the high-temperature alloy substrate by plasma spraying and coating method, the prepared coating has high bonding strength with the substrate material, improves the thermal expansion coefficient of the coating, and thus maintains a high absorption rate at 800°C. The coating and its preparation method can be applied to the preparation of high-temperature resistant solar heat-absorbing coatings.

[0044] The above description is only a preferred embodiment of the invention and is not intended to limit the invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the invention should be included in the protection scope of the invention.

Claims

1. A process for preparing a high temperature resistant composite heat absorbing coating using spinel pigment as a light absorber, characterized in that: Firstly, a NiCrAlY coating is deposited on a Ni-based high-temperature alloy substrate as a bonding layer by plasma spraying technology; then, a coating containing spinel pigment is evenly coated on the NiCrAlY coating by a spraying process to obtain a CuCrMnO4 heat-absorbing coating; finally, heat treatment is performed to form a composite heat-absorbing coating with good bonding strength on the Ni-based high-temperature alloy substrate.

2. The preparation process of the high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 1, characterized in that: The process specifically includes the following steps: (1) Pretreatment of the substrate; (2) NiCrAlY coating was deposited by plasma spraying technology; (3) Pretreatment of NiCrAlY coating; (4) Depositing the CuCrMnO4 heat absorbing coating by spraying process; (5) Curing heat treatment.

3. The preparation process of the high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 2, characterized in that: In step (1), the pretreatment process is as follows: first, the substrate SiC sandpaper is polished until the fresh substrate is exposed, then 60-220 mesh alumina is used for sandblasting to a roughness Ra>4μm, and finally deionized water and alcohol ultrasonic cleaning are performed for 15-30min, and then the substrate is rinsed with alcohol and dried.

4. The preparation process of the high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 2, characterized in that: In step (2), the process parameters for depositing the NiCrAlY coating by plasma spraying technology are: distance of 100-110 mm, voltage of 60-80 V, current of 500-600 A, hydrogen flow rate of 30-55 L / min, argon flow rate of 5-10 L / min, powder feeding amount of 10-20 rad / min, and the thickness of the NiCrAlY coating is 50 μm ± 5 μm.

5. The preparation process of the high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 2, characterized in that: In step (3), the pretreatment process is: first, use 60-220 mesh alumina for sandblasting to a roughness Ra>4μm, then use deionized water and alcohol ultrasonic cleaning for 15-30min, and finally rinse with alcohol and dry.

6. The process for preparing a high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 2, characterized in that: In step (4), the coating composition and mass fraction used for depositing the CuCrMnO4 heat-absorbing coating are as follows: 5-20% spinel pigment, 60%-95% resin, 0-10% curing agent, and 0-10% solvent.

7. The process for preparing a high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 6, characterized in that: The general chemical formula of spinel pigment is CuO·(Cr,Mn)2O3.

8. The process for preparing a high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 2, characterized in that: In step (5), the curing temperature is 250-500°C, the holding time is 10 min-1 h, the heating rate is ≤10°C / min, and after the holding is completed, the furnace is cooled to room temperature.

9. A high temperature resistant composite heat absorbing coating prepared by the method according to any one of claims 1 to 8 and using spinel pigment as a light absorber.

10. The high temperature resistant composite heat absorbing coating with spinel pigment as light absorber according to claim 9, characterized in that: The thickness of the composite heat-absorbing coating is 10 μm±2 μm.

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