Preparation method of CMAS corrosion resistant thermal barrier coating and thermal barrier coating obtained by preparation method
Technical Field
The invention relates to corrosion and protection of a thermal barrier coating, in particular to a preparation method of a CMAS corrosion resistant thermal barrier coating and the thermal barrier coating obtained by the preparation method.
Background
Advanced gas turbine engines are the core power devices of various aerospace vehicles and large ocean vessels, and are also the main conversion devices of power plants and energy industries. The turbine front inlet temperature of the primary aeroengine with the thrust weight ratio of 10 is 1850-1988K at present, and the turbine front design inlet temperature of the primary aeroengine with the thrust weight ratio of 12-15 reaches 2100-2200K, which is far higher than the limit temperature which can be born by the high-temperature alloy materials used for the turbine blades at present. In order to solve the problem, a coating with a thermal barrier function, namely a thermal barrier coating (Thermal Barrier Coatings, TBCs), can be sprayed on the surface of the high-temperature alloy to reduce the surface temperature of the high-temperature alloy and provide guarantee for the normal operation of the engine at a higher service temperature.
The TBCs are prepared by various methods, and the coatings prepared by different preparation processes also have different structures and performances. Common fabrication processes are atmospheric Plasma spray process (Atmospheric Plasma Spraying, APS), electron beam physical vapor deposition process (Electron Beam Physical Vapor Deposition, EB-PVD), plasma spray-physical vapor deposition process (PS-PVD), and the like. The coating prepared by the APS process has a layered structure, has more pores and microcracks and is parallel to the substrate; the coating prepared by the EB-PVD process has a typical columnar crystal structure, and gaps between columnar crystals are vertical to substrates; the coating prepared by the PS-PVD process has a dish-shaped columnar crystal. In addition, solution precursor plasma spraying (Solution Precursor Plasma Spray, SPPS) uses a solution precursor instead of a powder material in conventional plasma spraying, and can produce a coating layer having a nanostructure composed of a large number of fine particles, which has attracted attention in recent years.
With increasing engine operating temperature, a major component is CaO, mgO, al 2 O 3 And SiO 2 Will melt and adhere to the TBC surface and pose a serious hazard to the TBC. On one hand, CMAS is adsorbed and deposited on the surface of the coating, so that air film cooling holes on the surface of the coating are easily blocked, the cooling effect is reduced, and the temperature field and the stress field of the coating are further changed; on the other hand, the molten CMAS at high temperature permeates into the thermal barrier coating, accelerates the sintering and phase change instability of the coating, and greatly reduces the service life and the heat insulation capacity of the coating. The most commonly used ceramic materials of the current thermal barrier coating systems, 6-8wt% yttria partially stabilized zirconia (6-8 YSZ), are not resistant to CMAS corrosion.
CMAS protection methods can be classified into three types, namely, sacrificial type, dense impermeable type and non-wetting type, depending on the corrosion protection mechanism. Certain components within the sacrificial protective coating will react with environmental deposits to produce more difficult to penetrate materials. The impermeable coating is characterized by a continuous, dense, crack-free, direct barrier to melt penetration by physical features. The non-wetting protection method is to obtain a non-wetting surface to the molten CMAS by adopting a coating material which is non-wetting to the interface of the molten CMAS or changing the microstructure of the surface layer of TBCs, so that the contact between the coating and the melt is minimized.
At present, the sacrificial type and compact impermeable type protection methods are more, and corresponding patents are available at home and abroad. However, there is a thermal mismatch problem between the material of the sacrificial protection method and the YSZ material, and the structure of the dense impermeable protection method results in a low strain tolerance of the coating, and the thermal cycle performance of the coating is poor, which limits the large-scale application of the coating. The non-wetting type protection method is less common, and the published patent (patent number: CN 201610590053.2) adopts a PS-PVD process to prepare the CMAS corrosion resistant coating, so that the surface of the CMAS corrosion resistant coating has a nano structure, and has good CMAS adhesion resistance and wetting property. However, the PS-PVD coating has vertical pores, provides a channel for molten CMAS penetration, and is relatively expensive to manufacture.
Disclosure of Invention
In order to solve the problems that the thermal barrier coating in the prior art cannot effectively resist CMAS corrosion and the like, the invention provides a preparation method of the CMAS corrosion resistant thermal barrier coating and the thermal barrier coating obtained by the preparation method.
According to one aspect of the invention, there is provided a method of preparing a CMAS corrosion resistant thermal barrier coating comprising the steps of: s1, preparing a metal bonding layer on a substrate; s2, preparing a ceramic main body layer on the metal bonding layer; s3, preparing an anti-corrosion ceramic top layer by adopting solution precursor plasma spraying (Solution Precursor Plasma Spray, SPPS) on the ceramic main body layer, wherein micro-nano particles with the diameter of 0.2-1.5 mu m are stacked on the surface of the ceramic main body layer to form hemispherical protrusions with the diameter of 10-50 mu m or clustered protrusions with the diameter of 1-10 mu m, and the hemispherical protrusions or clustered protrusions and small particles on the surface of the hemispherical protrusions or clustered protrusions form a micro-nano double-scale structure.
Preferably, the step S1 further comprises sand blasting pretreatment and ultrasonic cleaning of the substrate before preparing the metal bonding layer.
Preferably, the material of the matrix is a high temperature nickel-based alloy IN738.
Preferably, the step S1 prepares the metal bonding layer using Atmospheric Plasma Spraying (APS).
Preferably, the material of the metal bonding layer is NiCrAlY.
Preferably, the step S2 prepares the ceramic body layer using Atmospheric Plasma Spraying (APS).
Preferably, the material of the ceramic body layer is YSZ.
Preferably, the step S3 comprises the following sub-steps: s31, dissolving a precursor raw material in a mixed solution of deionized water and absolute ethyl alcohol to prepare a solution precursor; and S32, spraying the solution precursor on the surface of the ceramic main body layer to form the corrosion-resistant ceramic top layer.
Preferably, the substep S31 is preceded by sanding and ultrasonic cleaning of the ceramic body layer. In a preferred embodiment, the ceramic body layer is sanded on 1000# sandpaper and 2000# sandpaper in sequence.
Preferably, the ceramic body layer is polished to a roughness of 1.0 to 4.5 μm. In a preferred embodiment, the surface roughness is controlled to be about 1.8 to 2.5 μm.
Preferably, the material of the corrosion resistant ceramic top layer is yttria partially stabilized zirconia (YSZ) or ytterbia yttria partially stabilized zirconia (YbYSZ). When the material of the top layer of the anti-corrosion ceramic is YSZ, the yttrium source of the precursor raw material is yttrium nitrate, and the zirconium source is zirconyl nitrate or zirconium acetate. When the material of the anti-corrosion ceramic top layer is YbYSZ, the yttrium source of the precursor raw material is yttrium nitrate, the zirconium source is zirconyl nitrate, and the ytterbium source is ytterbium nitrate.
Preferably, the volume ratio of deionized water to absolute ethyl alcohol of the mixed solution is 3:7-7:3. In a preferred embodiment, the volume ratio of deionized water to absolute ethanol of the mixed solution is 1:1.
Preferably, the concentration of Zr element in the solution precursor is 0.75mol/L to 1.5mol/L. In a preferred embodiment, the Zr element concentration of the solution precursor is 0.75mol/L.
Preferably, the micro-nano particles of the corrosion resistant ceramic top layer are stacked as hemispherical protrusions on the surface of the ceramic body layer by shadow effect. In a preferred embodiment, the hemispherical protrusions have a diameter of 17 to 30 μm. In a preferred embodiment, the hemispherical shape has a diameter of 19 to 35 μm.
It should be appreciated that the micro-nano particles of the corrosion resistant ceramic top layer are deposited in clusters on the surface of the ceramic body layer by shadow effect to form protrusions. In a preferred embodiment, the cluster-shaped projections have a diameter of less than 10 μm.
Preferably, said substep S32 comprises: the ceramic main body layer is preheated to 380-420 ℃ by a spray gun and then sprayed, the spraying voltage is 38-42V, the spraying current is 770-830A, the main air pressure is 0.4-0.5 MPa, the hydrogen pressure is 0.2-0.3 MPa, the moving speed of the spray gun is 200-600 mm/s, the spraying distance is 30-50 mm, and the liquid feeding flow is 25-35 ml/min. In a preferred embodiment, the ceramic body layer is preheated to 400 ℃ by a spray gun, then sprayed, the spraying voltage is 40V, the spraying current is 800A, the main air pressure is 0.47MPa, the hydrogen pressure is 0.25MPa, the moving speed of the spray gun is 400-600 mm/s, the spraying distance is 30-40 mm, and the liquid feeding flow is 30ml/min.
According to another aspect of the invention, there is provided a CMAS corrosion resistant thermal barrier coating comprising a metallic bond coat, a ceramic body layer, and a corrosion resistant ceramic top layer. Particularly, according to the CMAS corrosion resistant thermal barrier coating provided by the invention, the spreading and wetting of molten CMAS can be effectively prevented, the wetting diameter can be reduced to 50% of that of a conventional APS thermal barrier coating, and the CMAS corrosion resistant performance of the thermal barrier coating is improved.
Preferably, the ceramic body layer has a thickness of 250 to 350 μm.
Preferably, the thickness of the corrosion resistant ceramic top layer is 20 to 80 μm. In a preferred embodiment, the thickness of the corrosion resistant ceramic top layer is controlled to be around 50 μm.
According to the preparation method of the CMAS corrosion resistant thermal barrier coating, the solution precursor plasma spraying is adopted to prepare the corrosion resistant ceramic top layer, the solution precursor is adopted to replace the powder material in the traditional plasma spraying, and the prepared corrosion resistant ceramic top layer is formed by stacking a large number of tiny micro-nano particles. The anti-CMAS corrosion resistant thermal barrier coating corrosion resistant ceramic top layer has a non-wetting corrosion resistant mechanism, is non-wetting to molten CMAS, and prevents the molten CMAS from wetting and adhering to the surface of the thermal barrier coating, so that the contact area between the thermal barrier coating and CMAS melt is minimized. That is, the micro-nano particles of the anti-corrosion ceramic top layer enable the coating to have good hydrophobic property and CMAS wetting property, the contact angle of water and the anti-corrosion ceramic top layer can reach 150 degrees at normal temperature, compared with the conventional APS coating at 1300 ℃, the steady-state contact angle of the anti-corrosion ceramic top layer surface melting CMAS is increased by about 3 times, and the wetting diameter is reduced to 50%. In addition, according to the CMAS corrosion resistant thermal barrier coating, the corrosion resistant ceramic top layer prepared by solution precursor plasma spraying has loose structure, fine pores, uniform distribution and larger strain tolerance, and can effectively relieve thermal stress during thermal cycle and prolong the service life of the coating. Moreover, the preparation method of the CMAS corrosion resistant thermal barrier coating has the advantages of simple and accurate process operation and lower cost.
Drawings
FIG. 1 is a schematic structural view of a CMAS corrosion resistant thermal barrier coating made in accordance with the present invention;
FIG. 2A is a graph (500 times magnification) of the topography of the top layer of the corrosion resistant ceramic prepared in example 1;
FIG. 2B is a graph (at 2500 Xmagnification) of the topography of the top layer of the corrosion resistant ceramic prepared in example 1;
FIG. 2C is a cross-sectional profile (500 x magnification) of the corrosion resistant ceramic top layer prepared in example 1;
FIG. 3A is a macroscopic top view of the coating prepared in example 1 after 5 minutes CMAS wetting test;
FIG. 3B is a macroscopic top view of the coating prepared in example 1 after 10 minutes CMAS wetting test;
FIG. 3C is a macroscopic top view of the coating prepared in example 1 after 20 minutes CMAS wetting test;
FIG. 4A is a macroscopic top view of a conventional APS coating after 5 minutes CMAS wetting test;
FIG. 4B is a macroscopic top view of a conventional APS coating after 10 minutes CMAS wetting test;
FIG. 4C is a macroscopic top view of a conventional APS coating after 20 minutes CMAS wetting test;
FIG. 5 is a schematic view showing the contact angle of the surface of the top layer of the corrosion-resistant ceramic prepared in example 1 with water;
FIG. 6A is a graph (500 times magnification) of the topography of the top layer of the corrosion resistant ceramic prepared in example 2;
FIG. 6B is a graph (1700 times magnification) of the topography of the top layer of the corrosion resistant ceramic prepared in example 2;
FIG. 7A is a graph (1000 times magnified) of the topography of the top layer of the corrosion resistant ceramic prepared in example 3;
FIG. 7B is a graph (magnification 5000 times) of the topography of the top layer of the corrosion resistant ceramic prepared in example 3;
FIG. 8 is a CMAS contact angle comparison of a conventional APS coating with a corrosion resistant ceramic top layer;
fig. 9 is a CMAS wet-out diameter comparison of a conventional APS coating with a corrosion resistant ceramic top layer.
Detailed Description
Preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.
Example 1
The matrix of the high temperature nickel-base alloy IN738 (see fig. 1) was grit blasted and ultrasonically cleaned.
An NiCrAlY metallic bond coat was prepared on the substrate using Atmospheric Plasma Spray (APS) (see fig. 1). Specifically, after preheating a substrate to 400 ℃ by using a spray gun, niCrAlY powder is sprayed to prepare a metal bonding layer. The spraying voltage and current are respectively 60V and 500A, the main air pressure is 0.47MPa, and the hydrogen pressure is 0.25MPa. The moving speed of the spray gun is set to be 500mm/s, the spraying distance is 100mm, the powder feeding rotating speed is controlled to be 1.2r/min, and the thickness of the metal bonding layer is controlled to be about 100 mu m.
YSZ ceramic bulk layers were prepared on the metallic bond coat using Atmospheric Plasma Spray (APS) (see fig. 1). Specifically, a ceramic body layer was prepared by spraying YSZ powder after preheating the metal bond coat to 500 ℃ using a spray gun. The spraying voltage and current were 62V and 650A, respectively, the main gas pressure was 0.47MPa, and the hydrogen pressure was 0.25MPa. The moving speed of the spray gun is set to 150mm/s, the spraying distance is 80mm, the powder feeding rotating speed is controlled to 1.5r/min, and the thickness of the ceramic main body layer is controlled to about 300 mu m.
The method for preparing the corrosion-resistant ceramic top layer with the micro-nano double-scale structure by adopting Solution Precursor Plasma Spraying (SPPS) on the ceramic main body layer comprises the following specific steps:
sequentially polishing the ceramic main body layer on 1000# sand paper and 2000# sand paper, controlling the surface roughness to be about 2.5 mu m, and ultrasonically cleaning;
dissolving raw materials into a mixed solution of deionized water and absolute ethyl alcohol to prepare a solution precursor, wherein a yttrium source of a YSZ solution precursor raw material is yttrium nitrate, a zirconium source is zirconyl nitrate, wherein the concentration of Zr element in the precursor is 0.75mol/L, and the volume ratio of the deionized water to the absolute ethyl alcohol is 1:1;
and spraying the solution precursor on the surface of the ceramic main body layer to form the corrosion-resistant ceramic top layer. Specifically, the ceramic main body layer is preheated to 400 ℃ by using a spray gun, then is sprayed, the spraying voltage is 40V, the spraying current is 800A, the main air pressure is 0.47MPa, the hydrogen pressure is 0.25MPa, the moving speed of the spray gun is 400mm/s, the spraying distance is 30mm, the liquid feeding flow is 30ml/min, and the thickness of the anti-corrosion ceramic top layer is controlled to be about 50 mu m.
Fig. 2A and 2B are surface topography diagrams of the prepared anti-corrosion ceramic top layer, and fig. 2C is a cross-sectional topography diagram of the prepared anti-corrosion ceramic top layer, which can be seen from the figure, the anti-corrosion ceramic top layer is formed by stacking micro-nano particles with the diameter of 0.2-1.5 μm, the thickness is about 50 μm, and due to the shadow effect, the micro-nano particles are stacked into hemispheres on the surface of the ceramic main body layer, and the diameter is 19-35 μm.
CMAS powder was pressed into a cylinder of depth and diameter 1mm to form small cylindrical blocks, which were placed on the surface of the coating. The samples were placed in a 1300 ℃ ceramic fiber oven, and removed after heat treatment for various times (5 min, 10min, and 20 min), the results are shown in fig. 3A-3C. As can be seen from comparison of the conventional APS coating test results in FIGS. 4A-4C, the wetting diameter of the molten CMAS on the surface of the top layer of the corrosion-resistant ceramic is obviously reduced, the contact angle is increased, the wetting state is stabilized earlier, and the CMAS wetting resistance of the coating is obviously improved.
The water contact angle measurements were carried out on the corrosion resistant ceramic top layer, and the results were all between 152 and 159 degrees, as shown in fig. 5.
Example 2
The high-temperature nickel-based alloy IN738 matrix is subjected to sand blasting pretreatment and ultrasonic cleaning.
And preparing the NiCrAlY metal bonding layer on the substrate by adopting atmospheric plasma spraying. Specifically, after preheating a substrate to 400 ℃ by using a spray gun, niCrAlY powder is sprayed to prepare a metal bonding layer. The spraying voltage and current are respectively 60V and 500A, the main air pressure is 0.47MPa, and the hydrogen pressure is 0.25MPa. The moving speed of the spray gun is set to be 500mm/s, the spraying distance is 100mm, the powder feeding rotating speed is controlled to be 1.2r/min, and the thickness of the metal bonding layer is controlled to be about 100 mu m.
And preparing the YSZ ceramic main body layer on the metal bonding layer by adopting atmospheric plasma spraying. Specifically, a ceramic body layer was prepared by spraying YSZ powder after preheating the metal bond coat to 500 ℃ using a spray gun. The spraying voltage and current were 62V and 650A, respectively, the main gas pressure was 0.47MPa, and the hydrogen pressure was 0.25MPa. The moving speed of the spray gun is set to 150mm/s, the spraying distance is 80mm, the powder feeding rotating speed is controlled to 1.5r/min, and the thickness of the ceramic main body layer is controlled to about 250 mu m.
The method for preparing the corrosion-resistant ceramic top layer with the micro-nano double-scale structure by adopting solution precursor plasma spraying on the ceramic main body layer comprises the following specific steps:
sequentially polishing the ceramic main body layer on 1000# sand paper and 2000# sand paper, controlling the surface roughness to be about 1.8 mu m, and ultrasonically cleaning;
dissolving raw materials into a mixed solution of deionized water and absolute ethyl alcohol to prepare a solution precursor, wherein a yttrium source of a YSZ solution precursor raw material is yttrium nitrate, a zirconium source is zirconyl nitrate, wherein the concentration of Zr element in the precursor is 1mol/L, and the volume ratio of the deionized water to the absolute ethyl alcohol is 7:3;
and spraying the solution precursor on the surface of the ceramic main body layer to form the corrosion-resistant ceramic top layer. Specifically, the ceramic main body layer is preheated to 380 ℃ by using a spray gun, then is sprayed, the spraying voltage is 38V, the spraying current is 830A, the main air pressure is 0.5MPa, the hydrogen pressure is 0.2MPa, the moving speed of the spray gun is 200mm/s, the spraying distance is 40mm, the liquid feeding flow is 25ml/min, and the thickness of the anti-corrosion ceramic top layer is controlled to be about 80 mu m.
FIGS. 6A and 6B are surface topography diagrams of the prepared corrosion-resistant ceramic top layer, and it can be seen that the corrosion-resistant ceramic top layer is also formed by stacking micro-nano particles with diameters of 0.2-1.5 μm and is stacked into a hemispherical shape with diameters of 17-30 μm.
The resulting coating was subjected to CMAS wetting test, again with a smaller wetting diameter and a larger contact angle. The contact angles with water were measured to be between 150 and 156 degrees.
Example 3
The high-temperature nickel-based alloy IN738 matrix is subjected to sand blasting pretreatment and ultrasonic cleaning.
And preparing the NiCrAlY metal bonding layer on the substrate by adopting atmospheric plasma spraying. Specifically, after preheating a substrate to 400 ℃ by using a spray gun, niCrAlY powder is sprayed to prepare a metal bonding layer. The spraying voltage and current are respectively 60V and 500A, the main air pressure is 0.47MPa, and the hydrogen pressure is 0.25MPa. The moving speed of the spray gun is set to be 500mm/s, the spraying distance is 100mm, the powder feeding rotating speed is controlled to be 1.2r/min, and the thickness of the metal bonding layer is controlled to be about 100 mu m.
And preparing the YSZ ceramic main body layer on the metal bonding layer by adopting atmospheric plasma spraying. Specifically, a ceramic body layer was prepared by spraying YSZ powder after preheating the metal bond coat to 500 ℃ using a spray gun. The spraying voltage and current were 62V and 650A, respectively, the main gas pressure was 0.47MPa, and the hydrogen pressure was 0.25MPa. The moving speed of the spray gun is set to 150mm/s, the spraying distance is 80mm, the powder feeding rotating speed is controlled to be 1.5r/min, and the thickness of the ceramic main body layer is controlled to be about 350 mu m.
The method for preparing the corrosion-resistant ceramic top layer with the micro-nano double-scale structure by adopting solution precursor plasma spraying on the ceramic main body layer comprises the following specific steps:
the ceramic main body layer is polished on 1000# sand paper and 2000# sand paper in sequence, the surface roughness is controlled to be about 4.5 mu m, and ultrasonic cleaning is carried out.
And dissolving the raw materials in a mixed solution of deionized water and absolute ethyl alcohol to prepare a solution precursor. The source of yttrium serving as a precursor raw material of the YSZ solution is yttrium nitrate, and the source of zirconium is zirconium acetate. The concentration of Zr element in the precursor is 1.5mol/L; the volume ratio of deionized water to absolute ethyl alcohol is 3:7.
And spraying the solution precursor on the surface of the ceramic main body layer to form the corrosion-resistant ceramic top layer.
The ceramic main body layer is preheated to 420 ℃ by a spray gun, then is sprayed, the spraying voltage is 42V, the spraying current is 770A, the main air pressure is 0.4MPa, the hydrogen pressure is 0.3MPa, the moving speed of the spray gun is 600mm/s, the spraying distance is 50mm, the liquid feeding flow is 35ml/min, and the thickness of the corrosion-resistant ceramic top layer is controlled to be about 20 mu m.
Fig. 7A and 7B are surface topography diagrams of the prepared corrosion-resistant ceramic top layer, and it can be seen that the corrosion-resistant ceramic top layer is also formed by stacking micro-nano particles with diameters of 0.2-1.5 μm, however, no obvious hemispherical protrusions are formed, and the small particles are stacked in a cluster form, and the diameter is less than 10 μm. The reason is that the precursor with zirconium acetate as a zirconium source has larger viscosity, so that liquid drops are larger in the spraying process, a strong shadow effect cannot be generated, and small particles cannot form hemispherical bulges due to the smaller thickness. The resulting coatings were subjected to CMAS wetting tests and water contact angle tests, resulting in contact angles between 145 and 153 degrees, similar to examples 1 and 2.
Fig. 8 is a CMAS contact angle comparison of a conventional APS coating with a corrosion resistant ceramic top layer prepared in examples 1-3, and fig. 9 is a CMAS wetting diameter comparison of a conventional APS coating with a corrosion resistant ceramic top layer prepared in examples 1-3, it being observed that the anti-CMAS wetting performance of all examples is significantly improved over conventional APS coatings.
Compared with the conventional APS coating, the CMAS corrosion-resistant micro-nano double-scale structure thermal barrier coating provided by the invention has better CMAS wetting resistance, and can prevent the adhesion of molten CMAS on the surface of the coating, so that the corrosion resistance of the coating is improved, and the preparation cost is low, the preparation method is simple, and the industrial production and application are easy to realize.
The foregoing description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and various modifications can be made to the above-described embodiment of the present invention. All simple, equivalent changes and modifications made in accordance with the claims and the specification of this application fall within the scope of the patent claims. The present invention is not described in detail in the conventional art.