Composite vertical crack and quasi-columnar gradient structure thermal barrier coating and preparation method thereof

Abstract

The invention discloses a composite vertical crack and quasi-columnar gradient structure thermal barrier coating and a preparation method thereof, and relates to the field of material processing. The preparation method is carried out in a low-pressure cabin in a plasma spraying system under low vacuum conditions. The method obtains a plasma jet with a jet length of 1000mm-1800mm and a radial expansion size of 200mm-400mm by controlling relevant parameters; ceramic powder is sprayed by the plasma jet, and quasi-columnar structure ceramic coatings with different distribution densities are obtained by controlling different spraying distances, total gas flow rates, etc.; with the adjustment of the vacuum degree in the low-pressure cabin, the working current of the plasma, the total gas flow rate, and the spraying distance, the quasi-columnar structure ceramic coating is continuously pre-sintered, so that the composite vertical crack and quasi-columnar gradient structure thermal barrier coatings are directly deposited on the surface of a metal hot end component such as a high-temperature alloy, the vertical crack spacing of the composite coating is controllable, the bonding strength between the coatings is improved, and the thermal shock resistance is improved.

Description

Technical Field

[0001] The invention relates to the field of material processing, and in particular to a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure and a preparation method thereof. Background Art

[0002] Thermal barrier coating is a protective coating for hot end components of gas turbine engines, which is composed of a metal intermediate layer and a ceramic surface layer. The thermal barrier coating system on the surface of the hot end components of gas turbine engines can not only delay heat conduction, reduce the surface temperature of the substrate, and extend the service life of the substrate, but also provide good high-temperature oxidation corrosion protection for the high-temperature alloy substrate.

[0003] The lamellar ceramic thermal barrier coating with vertical crack distribution has good thermal insulation effect, high bonding strength and good stress release characteristics. At the same time, it greatly improves the thermal cycle life and thermal shock resistance compared with conventional thermal barrier coatings. The main principle of the vertical crack structure coating is that during multiple spraying processes, when the temperature of the substrate and the thickness of the single-layer spraying reach a critical value, the accumulated plane stress in the coating will be higher than the strength of the coating at this temperature, thereby generating cracks perpendicular to the substrate. In the process of vertical crack preparation, process control and control of crack density are key technologies.

[0004] Increasing the porosity of the coating is an effective way to enhance the thermal insulation performance of the coating. When the porosity is constant, as the diameter of the columnar pores decreases, its thermal insulation performance is enhanced and the structure is more stable; when the porosity is constant, as the columnar pores become elongated, the bonding strength between the layers gradually weakens, which is not conducive to anti-scouring environments. The large number of nanoscale grain boundaries and pores in the quasi-columnar coating significantly increase the scattering of phonons, and the thermal conductivity of the obtained coating is lower than that of the coating prepared by traditional atmospheric plasma spraying equipment. With the increase of cycle time, for the interface of the quasi-columnar structure ceramic coating, vertical cracks originate from the gaps between the porous columns and vertically penetrate the entire surface. This structure leads to the redistribution of radial thermal stress near the top coating / bonding coating interface, the compressive stress level is greatly reduced, and the compressive stress area is correspondingly reduced, and the thermal cycle resistance is higher than that of the layered structure coating.

[0005] The internal and interfacial bonding strength of thermal barrier coatings, as well as their thermal insulation performance, are usually important parameters for evaluating the quality of a coating. However, the internal and interfacial bonding strength and thermal insulation performance of current thermal barrier coatings usually cannot reach a good balance value, that is, if the internal and interfacial bonding strength of the prepared coating is good, its thermal shock resistance is good, but its thermal insulation performance is poor; if the thermal insulation performance of the coating is good, the internal and interfacial bonding strength of the coating is poor, and the thermal shock resistance is poor. Summary of the invention

[0006] The embodiment of the present invention provides a composite vertical crack and quasi-columnar gradient structure thermal barrier coating and a preparation method thereof to overcome the above technical problems.

[0007] In order to solve the above problems, an embodiment of the present invention discloses a method for preparing a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure. The method is carried out in a low-pressure cabin in a plasma spraying system under low vacuum conditions, and the method comprises:

[0008] Adjusting the vacuum degree in the low-pressure chamber, the working current of the plasma, and the total gas flow rate of the working gas to obtain a plasma jet with a jet length between 1000 mm and 1800 mm and a radial expansion size between 200 mm and 400 mm;

[0009] The ceramic powder is fed into the plasma jet, and the plasma jet is sprayed reciprocatingly at a preset scanning speed and spraying interval perpendicular to the substrate surface, and a quasi-columnar structure ceramic coating with different distribution densities is obtained according to different spraying distances, the total gas flow rate, the powder feeding rate and the control of the substrate temperature; wherein the quasi-columnar structure ceramic coating includes pores inside the column and gaps between the columns;

[0010] After the quasi-columnar structure ceramic coating reaches a preset spraying thickness, the vacuum degree in the low-pressure cabin, the working current of the plasma, the total gas flow rate and the spraying distance are adjusted, and the quasi-columnar structure ceramic coating is continued to be pre-sintered using the plasma jet, so that the quasi-columnar structure ceramic coating is in a state where the gaps between the columns are partially fused or completely fused while the pores inside the columns are not fused, thereby obtaining a composite vertical crack and quasi-columnar gradient structure thermal barrier coating.

[0011] In one embodiment of the present invention, the adjustment range of the plasma working current is 2000-2600A.

[0012] In one embodiment of the present invention, the adjustment range of the total air flow rate is 90L / min-120L / min.

[0013] In one embodiment of the present invention, the working gas is a mixture of argon and helium.

[0014] In one embodiment of the present invention, the control range of the spraying distance is 1200-1500 mm.

[0015] In one embodiment of the present invention, the outlet temperature of the plasma jet is greater than 12000K, and the jet speed is greater than 6000m / s.

[0016] In one embodiment of the present invention, the particle size of the ceramic powder is 1-30 μm or 37-69 μm.

[0017] In one embodiment of the present invention, the preset spraying thickness is greater than 150 μm.

[0018] In one embodiment of the present invention, the plasma spraying system under low vacuum conditions comprises: a substrate clamping control unit, a plasma generating unit located directly above the substrate, and a jet stabilization control unit and a powder feeding control unit respectively connected to the plasma generating unit;

[0019] Wherein, the substrate clamping control unit is used to clamp the substrate, control the substrate to remain perpendicular to the plasma jet, and control the temperature of the substrate during spraying and the temperature during pre-sintering;

[0020] The plasma generating unit is used to spray the plasma jet toward the substrate;

[0021] The jet stabilization control unit is used to control the plasma jet to reciprocate on the surface of the substrate at the scanning speed and the spraying interval;

[0022] The powder feeding control unit is used to feed ceramic powder into the plasma jet in the low-pressure cabin.

[0023] In order to solve the above problems, an embodiment of the present invention further discloses a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure. The thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure is prepared by the method described in the embodiment of the present invention.

[0024] The embodiments of the present invention include the following advantages:

[0025] The embodiment of the present invention discloses a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure and a preparation method thereof. The preparation method is carried out in a low-pressure cabin in a plasma spraying system under low vacuum conditions, and the steps include: adjusting the vacuum degree in the low-pressure cabin, the working current of the plasma, and the total gas flow rate of the working gas to obtain a plasma jet with a jet length between 1000mm and 1800mm and a radial expansion size between 200mm and 400mm; feeding ceramic powder into the plasma jet, and reciprocatingly spraying the plasma jet perpendicular to the surface of the substrate at a preset scanning speed and spraying interval; and adjusting the spraying distance, total spraying interval, and the like according to different spraying distances, total spraying intervals, and the like. The air flow rate, powder feeding rate and substrate temperature are controlled to obtain quasi-columnar structure ceramic coatings with different distribution densities; wherein, the quasi-columnar structure ceramic coating includes pores inside the column and gaps between the columns; after the quasi-columnar structure ceramic coating reaches the preset spraying thickness, the vacuum degree in the low-pressure cabin, the working current of the plasma, the total air flow rate and the spraying distance are adjusted, and the quasi-columnar structure ceramic coating is continued to be pre-sintered by the plasma jet, so that the quasi-columnar structure ceramic coating is in a state where the gaps between the columns are partially fused or completely fused and the pores inside the columns are not fused, thereby obtaining a composite vertical crack and quasi-columnar gradient structure thermal barrier coating. In this way, the embodiment of the present invention realizes the direct deposition of composite vertical cracks and quasi-columnar gradient structure thermal barrier coatings on the surface of metal hot end components such as high-temperature alloys, and the vertical crack spacing of the coating is controllable, which not only reduces the length of the gaps between the columns, thereby improving the bonding strength between the coatings and improving their thermal shock resistance, but also retains a part of the pores, which can maintain the good thermal insulation performance of the coating, and the process is simple, easy to operate, and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a flow chart of the steps of a method for preparing a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure according to an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of vertical cracks of composite vertical cracks and quasi-columnar gradient structure thermal barrier coatings according to an embodiment of the present invention;

[0029] Figure 3a This is a schematic diagram of the microscopic morphology of a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure according to an embodiment of the present invention;

[0030] Figure 3bIt is another microscopic morphology schematic diagram of the thermal barrier coating with composite vertical cracks and quasi-columnar gradient structure according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] In view of the technical problem of this application, this application proposes a method for preparing a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure, which is carried out in a low-pressure cabin in a plasma spraying system under low vacuum conditions. In this application, in addition to the low-pressure cabin, the plasma spraying system under low vacuum conditions may also include: a substrate clamping control unit, a plasma generating unit located directly above the substrate, and a jet stabilization control unit and a powder feeding control unit respectively connected to the plasma generating unit, wherein:

[0033] The substrate clamping control unit is used to clamp the substrate, control the substrate to remain perpendicular to the plasma jet, and control the temperature of the substrate during the spraying process and the temperature during pre-sintering. In the present application, the substrate is a carrier that needs to deposit a ceramic coating or a metal ceramic coating. The substrate can be made of austenitic stainless steel, nickel-based high-temperature alloy or cobalt-based precipitation hardening type directional solidification columnar crystal high-temperature alloy, etc., which is generally used in aircraft engines and large gas turbine hot end components. After the substrate clamping control unit clamps the substrate, the inclination angle of the substrate can be controlled to control the substrate surface to remain perpendicular to the plasma jet during the preparation of the coating; the inclination direction of the above-mentioned inclination angle includes but is not limited to positive upward inclination, positive downward inclination, positive left inclination and positive right inclination. The substrate clamping control unit also has a temperature control function, which can control the temperature of the substrate during the spraying process and the temperature during pre-sintering, so that the compressive stress and tensile stress generated by the ceramic coating during cyclic operation have a better balance.

[0034] The plasma generating unit is used to spray a plasma jet toward the substrate. In the present application, the plasma jet generated by the plasma generating unit has the characteristics of being significantly long, stable and concentrated, with a rated power of 120 kW, and can adjust the total gas flow rate of the working gas, the working current of the plasma, etc.

[0035] The jet stabilization control unit is used to control the plasma jet to reciprocate on the substrate surface at a scanning speed and a spraying interval. In the present application, the jet stabilization control unit can control the length and spatial distribution of the plasma jet in the process of controlling the scanning speed and the spraying interval of the plasma jet, and effectively prevent the disturbance of the plasma jet by the external airflow, so as to maintain the ultra-long heating and acceleration process of the particles in the plasma jet.

[0036] The powder feeding control unit is used to feed ceramic powder into the plasma jet in the low-pressure cabin. The powder feeding control unit can feed ceramic powder into the plasma jet in a concentrated manner by controlling a certain powder feeding rate without affecting the normal operation of the plasma jet, and the powder utilization rate can reach more than 90%.

[0037] Based on the plasma spraying system under the above low vacuum conditions, refer to Figure 1 The method for preparing a composite vertical crack and quasi-columnar gradient structure thermal barrier coating proposed in the present application may specifically include the following steps:

[0038] Step S101: adjusting the vacuum degree in the low-pressure chamber, the working current of the plasma and the total gas flow rate of the working gas to obtain a plasma jet with a jet length between 1000mm and 1800mm and a radial expansion size between 200mm and 400mm.

[0039] In the present application, the vacuum degree in the low-pressure chamber is pumped to a certain vacuum degree by a vacuum pump, that is, the vacuum degree in the low-pressure chamber is adjusted, and the pressure in the low-pressure chamber is reduced, which can further expand and widen the plasma jet, thereby realizing large-area rapid deposition of the coating. Optionally, the vacuum degree in the low-pressure chamber can be adjusted in the range of 50 to 1000 Pa.

[0040] In the present application, the working current of the plasma and the total gas flow rate of the working gas are factors that affect the morphology and characteristics of the plasma jet. The plasma jet output power can be increased by controlling the working current of the plasma using the plasma generating unit; the total gas flow rate of the working gas is controlled by the plasma generating unit. The working gas is heated by the arc in the electrode gun and dissociated into high-energy and high-pressure plasma, which expands rapidly after entering the low-pressure cabin through the nozzle to form a supersonic plasma jet. Among them, the working gas can be a mixed gas of argon and helium, and plasma can be generated by discharging the mixed gas of argon and helium.

[0041] However, in reality, the working current and the total gas flow rate of the working gas are not the higher the higher. Too high a working current will sharply increase the coating deposition cost, and too high a total gas flow rate will dilute the ionization degree of the plasma, causing the enthalpy value of the plasma jet to decrease. Therefore, preferably, the adjustment range of the working current of the plasma of the present application is 2000-2600A. The adjustment range of the total gas flow rate of the working gas is 90L / min-120L / min. Within this adjustment range, combined with the adjustment of the vacuum degree in the low-pressure cabin, the present application can obtain a plasma jet with a jet length between 1000mm-1800mm and a radial expansion size between 200mm-400mm. This jet length and radial expansion size can significantly increase the synchronous deposition temperature during the spraying process, while heating and accelerating the powder, it also heats the substrate and pre-sinters the coating.

[0042] The jet length of the plasma jet generated by the present application is highly controllable from 1000-1800mm, and varies to a certain extent according to the vacuum degree, gas flow and output power of the equipment. The outlet temperature of the plasma jet is greater than 12000K, the jet speed is greater than 6000m / s, and an ultra-long high temperature area is maintained, which can effectively heat the powder and the substrate.

[0043] Step S102: feeding ceramic powder into the plasma jet, and reciprocatingly spraying the plasma jet perpendicular to the substrate surface at a preset scanning speed and spraying interval, and obtaining a quasi-columnar structure ceramic coating with different distribution densities according to different spraying distances, the total gas flow rate, the powder feeding rate and the control of the substrate temperature; wherein the quasi-columnar structure ceramic coating includes pores inside the column and gaps between the columns.

[0044] In the present application, the ceramic powder may be ZrO2-7% Y2O3 (7YSZ) powder, and the ceramic powder may be fed into the plasma jet by a powder feeding control unit. The powder feeding rate is controlled by the powder feeding control unit, and optionally, the powder feeding rate is 3 to 4 g / min, and the particle size of the ceramic powder is 1 to 30 μm or 37 to 69 μm.

[0045] The scanning speed and spraying interval of the plasma jet on the substrate are controlled by a jet stabilization control unit. The scanning speed and spraying interval can be determined according to the crack density of the required quasi-columnar structure ceramic coating, which is more humane.

[0046] The spraying distance is the distance between the outlet of the plasma generating unit spraying the plasma jet and the substrate. Preferably, the control range of the spraying distance of the present application is 1200-1500mm. The plasma jet can heat the substrate. The ceramic powder is fed into the plasma jet to deposit a quasi-columnar structure ceramic coating on the substrate. The present application can effectively obtain quasi-columnar structure ceramic coatings with different distribution densities by controlling the spraying distance, the total gas flow rate, the powder feeding rate and the substrate temperature; wherein the obtained quasi-columnar structure ceramic coating includes a plurality of columnar structures, gaps are formed between the columns, and pores are formed inside the columns.

[0047] Step S103: After the quasi-columnar structure ceramic coating reaches a preset spraying thickness, the vacuum degree in the low-pressure cabin, the working current of the plasma, the total gas flow rate of the working gas and the spraying distance are adjusted, and the quasi-columnar structure ceramic coating is continued to be pre-sintered using the plasma jet, so that the quasi-columnar structure ceramic coating is in a state where the gaps between the columns are partially fused or completely fused while the pores inside the columns are not fused, thereby obtaining a composite vertical crack and quasi-columnar gradient structure thermal barrier coating.

[0048] Pre-sintering refers to pre-sintering the quasi-columnar structure ceramic coating at different temperatures and for different times at a temperature lower than the melting point of the quasi-columnar structure ceramic coating. The present application pre-sinters the quasi-columnar structure ceramic coating to fuse the elongated columnar pores (i.e., the gaps between the columns) in the coating, reduce the length of the gaps between the columns, thereby improving the bonding strength between the coatings and improving their thermal shock resistance, while retaining a portion of the pores to maintain the coating's good thermal insulation performance.

[0049] The embodiment of the present application can increase the pre-sintering temperature by using a substrate clamping control unit. As the pre-sintering temperature increases, the bonding strength of the quasi-columnar structure ceramic coating is enhanced and the uniformity of the organization is significantly improved.

[0050] The spraying thickness of the quasi-columnar structure ceramic coating, the vacuum degree in the low-pressure chamber, the working current of the plasma, the total gas flow rate of the working gas and the spraying distance all affect the final composite vertical cracks and quasi-columnar gradient structure thermal barrier coating. Among them, the spraying thickness of the quasi-columnar structure ceramic coating is preferably greater than 150μm, and the vacuum degree in the low-pressure chamber, the working current of the plasma, the total gas flow rate of the working gas and the spraying distance can be adjusted with reference to the aforementioned range values, that is, the vacuum degree in the low-pressure chamber is adjusted in the range of 50 to 1000Pa, the working current of the plasma is adjusted in the range of 2000-2600A, the total gas flow rate of the working gas is adjusted in the range of 90L / min-120L / min, and the spraying distance is adjusted in the range of 1200-1500mm.

[0051] Based on the same inventive concept, the embodiment of the present invention also discloses a composite vertical crack and quasi-columnar gradient structure thermal barrier coating, which is prepared by the method described in the embodiment of the present invention. The vertical crack schematic diagram of the composite vertical crack and quasi-columnar gradient structure thermal barrier coating can be referred to Figure 2 Its microscopic morphology can be referred to Figure 3a and Figure 3b .

[0052] Below, several specific examples are used to further illustrate the preparation method and preparation effect of a composite vertical crack and quasi-columnar gradient structure thermal barrier coating.

[0053] Example 1:

[0054] The base is made of austenitic chromium-nickel stainless steel (commonly known as heat-resistant stainless steel 310S). Austenitic chromium-nickel stainless steel has good oxidation resistance and corrosion resistance, a higher percentage of chromium and nickel, good creep strength, can continue to operate at high temperatures, and has good high temperature resistance.

[0055] The preparation method is as follows:

[0056] 1) preparing a rectangular or circular substrate material, and fixing the substrate and the substrate clamping control unit by a fixing clamping device;

[0057] 2) The substrate surface is sandblasted, and then a bonding layer of NiCrAlY is sprayed using a supersonic flame with a spraying thickness of 100-150 μm;

[0058] 3) Turn on the plasma generating unit, adjust the working gas to a mixture of argon and helium, the working current to 2000A, turn on the jet stabilization control unit, and spray a plasma jet with a length of 1500 mm toward the substrate;

[0059] 4) preparing 7YSZ powder with a particle size of 1 to 30 μm and a powder feeding rate of 3 to 4 g / min, and feeding the 7YSZ powder into the plasma jet in the low-pressure cabin at the powder feeding rate;

[0060] 5) Controlling the spraying distance to be 1500 mm, controlling the plasma jet to reciprocate on the surface of the substrate according to the spraying distance, the predetermined scanning speed and the spraying interval, and controlling the robotic arm to obtain a quasi-columnar structure ceramic coating with a thickness of more than 150 μm;

[0061] 6) First, the powder feeding control unit is turned off, and the total gas flow rate of the plasma jet is adjusted to pre-sinter the deposited quasi-columnar structure ceramic coating and form a vertical crack structure at the column spacing;

[0062] 7) Wait for the substrate clamping control unit to lower the sample temperature to room temperature, remove the sample, and obtain a composite vertical crack with a vertical crack spacing of 2 to 3 per cm and a quasi-columnar gradient structure thermal barrier coating.

[0063] Example 2:

[0064] The matrix is ​​made of nickel-based high-temperature alloy K465, which has high creep and fatigue resistance and high temperature bearing capacity, and is usually used as the static blades of the propeller.

[0065] The preparation method is as follows:

[0066] 1) preparing a substrate, and fixing the substrate and the substrate clamping control unit by a fixing clamping device;

[0067] 2) The substrate surface is sandblasted, and then a bonding layer of NiCrAlY is sprayed using a supersonic flame with a spraying thickness of 100-150 μm;

[0068] 3) Turn on the plasma generating unit, adjust the working gas to a mixture of argon and helium, the working current to 2000A, turn on the jet stabilization control unit, and spray a plasma jet with a length of 1500 mm toward the substrate;

[0069] 4) preparing 7YSZ powder with a particle size of 1 to 30 μm and a powder feeding rate of 3 to 4 g / min, and feeding the 7YSZ powder into the plasma jet in the low-pressure cabin at the powder feeding rate;

[0070] 5) Controlling the spraying distance to be 1500 mm, controlling the plasma jet to reciprocate on the surface of the substrate according to the spraying distance, the predetermined scanning speed and the spraying interval, and controlling the robotic arm to obtain a quasi-columnar structure ceramic coating with a thickness of more than 200 μm;

[0071] 6) First, the powder feeding control unit is turned off, and the total gas flow rate of the plasma jet is adjusted to pre-sinter the deposited quasi-columnar structure ceramic coating and form a vertical crack structure at the column spacing;

[0072] 7) Wait for the substrate clamping control unit to lower the sample temperature to room temperature, remove the sample, and obtain a thermal barrier coating with a composite vertical crack and a quasi-columnar gradient structure.

[0073] Example 3:

[0074] The matrix is ​​made of cobalt-based precipitation hardening directionally solidified columnar crystal superalloy DZ640M (DZ40M). The use temperature of cobalt-based precipitation hardening directionally solidified columnar crystal superalloy is below 1040℃, the structure is stable, and it has excellent resistance to cold and hot fatigue, oxidation and heat corrosion. At the same time, the alloy has good comprehensive properties such as creep resistance, durability and fatigue resistance. The main products are directional solidification castings such as turbine guide blades.

[0075] The preparation method is as follows:

[0076] 1) preparing a substrate, and fixing the substrate and the substrate control unit by a fixing clamping device;

[0077] 2) The substrate surface is sandblasted, and then a bonding layer NiCrAlY is prepared using a multi-arc ion plating device;

[0078] 3) Turn on the plasma generating unit, adjust the working gas to a mixture of argon and helium, the working current to 2000A, and turn on the jet stabilization control unit to spray a plasma jet with a length of 1500mm toward the substrate;

[0079] 4) preparing 7YSZ powder with a particle size of 37 to 69 μm and a powder feeding rate of 3 to 4 g / min, and feeding the 7YSZ powder into the plasma jet in the low-pressure cabin at the powder feeding rate;

[0080] 5) Controlling the spraying distance to be 1200 mm, controlling the plasma jet to reciprocate on the surface of the substrate according to the spraying distance, the predetermined scanning speed and the spraying interval, and controlling the robotic arm to obtain a quasi-columnar structure ceramic coating with a thickness of more than 200 μm;

[0081] 6) First, the powder feeding control unit is turned off, and the total gas flow rate of the plasma jet is adjusted to pre-sinter the deposited quasi-columnar structure ceramic coating and form a vertical crack structure at the column spacing;

[0082] 7) Wait for the substrate clamping control unit to lower the sample temperature to room temperature, remove the sample, and obtain a thermal barrier coating with a composite vertical crack and a quasi-columnar gradient structure.

[0083] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0084] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. "And / or" means that either one of the two can be selected, or both can be selected. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or terminal device including the elements.

[0085] The above is a detailed introduction to a composite vertical crack and quasi-columnar gradient structure thermal barrier coating and a preparation method thereof provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for a person skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for preparing a thermal barrier coating with a composite vertical crack and quasi-columnar gradient structure, characterized in that: The method is carried out in a low-pressure cabin in a plasma spraying system under low vacuum conditions, and the method comprises: Adjusting the vacuum degree in the low-pressure chamber, the working current of the plasma, and the total gas flow rate of the working gas to obtain a plasma jet with a jet length between 1000 mm and 1800 mm and a radial expansion size between 200 mm and 400 mm; The ceramic powder is fed into the plasma jet, and the plasma jet is sprayed reciprocatingly at a preset scanning speed and spraying interval perpendicular to the substrate surface, and a quasi-columnar structure ceramic coating with different distribution densities is obtained according to different spraying distances, the total gas flow rate, the powder feeding rate and the control of the substrate temperature; wherein the quasi-columnar structure ceramic coating includes pores inside the column and gaps between the columns; After the quasi-columnar structure ceramic coating reaches a preset spraying thickness, the vacuum degree in the low-pressure cabin, the working current of the plasma, the total gas flow rate and the spraying distance are adjusted, and the quasi-columnar structure ceramic coating is continued to be pre-sintered by the plasma jet at a temperature lower than the melting point of the quasi-columnar structure ceramic coating, so that the quasi-columnar structure ceramic coating is in a state where the gaps between the columns are partially fused or completely fused and the pores inside the columns are not fused, thereby obtaining a composite vertical crack and quasi-columnar gradient structure thermal barrier coating; The control range of the spraying distance is 1200-1500mm; Wherein, the temperature during the spraying process and the pre-sintering temperature are controlled by a substrate clamping control unit in the plasma spraying system.

2. The preparation method according to claim 1, characterized in that: The adjustment range of the plasma working current is 2000-2600A.

3. The preparation method according to claim 1, characterized in that: The adjustment range of the total air flow is 90L / min-120L / min.

4. The preparation method according to claim 1 or 3, characterized in that: The working gas is a mixed gas of argon and helium.

5. The preparation method according to claim 1, characterized in that: The outlet temperature of the plasma jet is greater than 12000K, and the jet speed is greater than 6000m / s.

6. The preparation method according to claim 1, characterized in that: The particle size of the ceramic powder is 1 to 30 μm or 37 to 69 μm.

7. The preparation method according to claim 1, characterized in that: The preset spraying thickness is greater than 150 μm.

8. The preparation method according to claim 1, characterized in that: The plasma spraying system under low vacuum conditions comprises: a substrate clamping control unit, a plasma generating unit located directly above the substrate, and a jet stabilization control unit and a powder feeding control unit respectively connected to the plasma generating unit; Wherein, the substrate clamping control unit is used to clamp the substrate, control the substrate to remain perpendicular to the plasma jet, and control the temperature of the substrate during spraying and the temperature during pre-sintering; The plasma generating unit is used to spray the plasma jet toward the substrate; The jet stabilization control unit is used to control the plasma jet to reciprocate on the surface of the substrate at the scanning speed and the spraying interval; The powder feeding control unit is used to feed ceramic powder into the plasma jet in the low-pressure cabin.

9. A composite vertical crack and quasi-columnar gradient structure thermal barrier coating, characterized in that: The composite vertical crack and quasi-columnar gradient structure thermal barrier coating is prepared by any one of the methods described in claims 1 to 8.

Images