CN111960837B

CN111960837B - Preparation method of rare earth tantalate or niobate thermal barrier coating

Info

Publication number: CN111960837B
Application number: CN202010887388.7A
Authority: CN
Inventors: 冯晶; 郑奇; 杨凯龙; 王一涛; 汪俊; 陈琳; 宋鹏; 葛振华; 李振军; 王峰
Original assignee: Shaanxi Tianxuan Coating Technology Co ltd; Kunming University of Science and Technology
Current assignee: Shaanxi Tianxuan Coating Technology Co ltd; Kunming University of Science and Technology
Priority date: 2020-08-28
Filing date: 2020-08-28
Publication date: 2021-10-26
Anticipated expiration: 2040-08-28
Also published as: CN111960837A

Abstract

The invention relates to the technical field of thermal barrier coatings, and particularly discloses a preparation method of a rare earth tantalate or niobate thermal barrier coating, which comprises the following steps: taking more than two different rare earth tantalates (RETaO)₄) Or niobate (RENbO)₄) Mixing ceramic powder into n parts of mixed ceramic powder, wherein the volume fraction of at least one rare earth tantalate or niobate ceramic component in the n parts of mixed ceramic powder is continuously increased or decreased; and sequentially depositing n parts of mixed ceramic powder on a base material to obtain the multi-gradient rare earth tantalate or niobate thermal barrier coating. The scheme of the patent can ensure that the thermal barrier coating has the original rare earth niobium/tantalate ceramic (RENB/TaO)₄) The ceramic has high expansion coefficient and greatly reduced thermal conductivity, and the experimental detection shows that the thermal conductivity does not exceed 1.20 W.m^‑1·K^‑1And the requirement of the thermal barrier coating on low thermal conductivity is met.

Description

Preparation method of rare earth tantalate or niobate thermal barrier coating

Technical Field

The invention relates to the technical field of thermal barrier coatings, in particular to a preparation method of a rare earth tantalate or niobate thermal barrier coating.

Background

The thermal barrier coating protects the base material by utilizing the heat insulation and corrosion resistance characteristics of the ceramic, and has important application value in the aspects of aviation, aerospace, ships, weapons and the like. At present, the widely used thermal barrier coating materials are mainly 6% -8% of yttria-stabilized zirconia (6-8YSZ) and lanthanum zirconate (La)₂Zr₂O₇) Both of these ceramics have some disadvantages: the use temperature of 6-8YSZ is lower (less than or equal to 1200 ℃), and the thermal conductivity is higher (about 2.5 W.m)^-1·k^-1，900℃)，La₂Zr₂O₇The thermal expansion coefficient is low, and with the future development requirements of high thrust-weight ratio and high outlet temperature of engines and gas turbines, the search for novel thermal barrier coating materials is urgent.

Rare earth niobium/tantalate ceramics (RENb/TaO)₄) With high melting point and low thermal conductivity (1.38-1.94 W.m)^-1·K^-1) High coefficient of thermal expansion (11X 10)^-6K^-11200 ℃ and the iron elastic toughness, and the like, and is considered as a new generation of thermal barrier coating material with the most potential. The ferroelastic toughening mechanism endows the rare earth niobium/tantalate ceramic with excellent high-temperature fracture toughness, which is a unique advantage that other potential thermal barrier coating materials do not have; the use of the material in the field of thermal barrier coatings is also under study, and how to maximize the use of the material is shown in rare earth niobium/tantalate ceramics (RENB/TaO)₄) The protective effect of ceramic coatings on base alloys remains the focus of current research.

Disclosure of Invention

The invention provides a method for preparing a rare earth tantalate or niobate thermal barrier coating,so as to obtain rare earth niobium/tantalate ceramic (RENB/TaO) with lower thermal conductivity and meeting the use requirement of a thermal barrier coating in a high-temperature environment₄) A thermal barrier coating.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a preparation method of a rare earth tantalate or niobate thermal barrier coating comprises the following steps:

step 1: taking more than two different rare earth tantalates (RETaO)₄) Or niobate (RENbO)₄) Mixing ceramic powder into n parts of mixed ceramic powder, wherein the volume fraction of at least one rare earth tantalate or niobate ceramic component in the n parts of mixed ceramic powder is continuously increased or decreased;

step 2: and (3) sequentially depositing the n parts of mixed ceramic powder obtained in the step (1) on a base material to obtain the multi-gradient rare earth tantalate or niobate thermal barrier coating.

The technical principle and the effect of the technical scheme are as follows:

1. in the scheme, a multi-gradient coating is obtained by designing more than two different rare earth tantalate or niobate ceramic powders, namely, the volume fraction of at least one ceramic component in the coating is continuously increased or continuously decreased, so that the thermal barrier coating can be ensured to have the original rare earth niobium/tantalate ceramic (RENB/TaO)₄) The ceramic has high expansion coefficient and greatly reduced thermal conductivity, and the experimental detection shows that the thermal conductivity does not exceed 1.20 W.m^-1·k^-1And the requirement of the thermal barrier coating on low thermal conductivity is met.

2. The multi-element gradient ceramic coating with low thermal conductivity can be obtained in the scheme, the reason is that the components among the gradient coatings are in a gradual change form, so that the interfaces formed among the gradient coatings are few, the interface effect is weak, and the most important point is that the components of each layer can be continuously diffused in the deposition process of each gradient coating, so that the interface effect is continuously weakened, and the thermal conductivity is reduced.

Further, the thickness of the rare earth tantalate or niobate thermal barrier coating is 150-300 mu m.

Has the advantages that: experiments prove that the thickness of the multi-element gradient coating is set to be 150-300 mu m, and the thermal conductivity of the obtained thermal barrier coating is low.

Further, n in the step 1 is 6-21.

Has the advantages that: experiments prove that the number n of the gradient layers is set to be 6-21, so that the diffusion effect of components among the gradient layers is met, and the actual deposition process difficulty is met.

Further, a metal bonding layer with the thickness of 100-150 mu M is deposited on the surface of the base material in advance in the step 2, the component of the metal bonding layer is MCrAlY, and M is Ni or Co.

Has the advantages that: the arrangement of the metal bonding layer can improve the bonding property between the rare earth tantalate and the base material.

Further, the step 2 adopts APS, HVOF, EB-PVD or supersonic electric arc spraying method to carry out coating deposition treatment.

Has the advantages that: the preparation processes of the coatings are all existing mature processes and can be selected according to specific production environments.

Further, the preparation method of the rare earth tantalate or niobate powder comprises the following steps:

step 1: according to the structural formula RETaO₄Or RENbO₄Get RE₂O₃Dissolving the powder in concentrated nitric acid to a pH below 1.5, adding TaOCl₃Or NbOCl₃Dropwise adding the solution, continuously stirring, simultaneously adding ammonia water to stabilize the pH value of the system to 9-10, continuously stirring in a water bath environment, sequentially washing and precipitating with absolute ethyl alcohol or deionized water until the pH value is 7, placing the obtained filter cake in an oven for drying, then sieving and sintering in a medium-temperature environment, and sieving the sintered powder again for later use;

step 2: mixing the powder prepared in the step 1 with water with the mass not less than 30wt.% to obtain slurry A, mixing the slurry A with a binder, polyethylene glycol, n-octanol, a tackifier and a pore-increasing agent to obtain slurry B, and then sending the slurry B into a centrifugal spray dryer to carry out centrifugal spray granulation on the slurry B to obtain spherical rare earth tantalate or niobate powder with the powder particle size of 30-70 mu m.

Has the advantages that: the rare earth tantalum/niobate ceramic powder prepared by the method not only consumes less time and has high purity, but also has complete phase formation, uniform components and small powder loss.

Further, TaOCl in the step 1₃The dropping speed of the solution is 200-400 mL/min, the temperature of the water bath is 50-100 ℃, the stirring time is 30-120 min, the drying temperature is 80-120 ℃, and the drying time is 5-10 h; the medium-temperature sintering temperature is 900-1100 ℃, the time is 3-5h, and the used sieve is 300-500 meshes.

Has the advantages that: the parameter setting can meet the requirement of preparing ceramic powder by a coprecipitation method.

Further, in the step 2, the content of the binder is 0.5-3 wt.%, the content of the additive is 0.1-1 wt.%, the feeding speed of the slurry B is controlled at 300-500 mL/h, and the spraying and centrifuging speed is 8000-10000 r/min.

Has the advantages that: such parameters ensure a homogeneous composition of the powder obtained.

Detailed Description

The following is further detailed by way of specific embodiments:

example 1:

preparation method of rare earth tantalate or niobate powder to prepare YNbO₄For example, the method comprises the following steps:

step 1: according to YNbO₄Structural formula (II) is₂O₃Dissolving in concentrated nitric acid for reaction, adjusting pH to about 1, and preparing NbOCl₃Dropwise adding the solution (the dropping speed is 200mL/min), continuously stirring, simultaneously adding ammonia water to stabilize the pH value of the system at 9-10, stirring for 1 hour, continuously stirring for 120min in a water bath environment at 60 ℃, then continuously washing and precipitating with deionized water until the pH value is 7, placing the obtained filter cake in a drying oven at 120 ℃ for drying for 5 hours, then sieving with a 500-mesh sieve, sintering at 900 ℃ for 5 hours, and sieving the sintered powder with the 500-mesh sieve again for later use.

Step 2: mixing the powder prepared in step 1 with 30wt.% of water based on the mass of the powderObtaining slurry A, uniformly mixing the slurry A with 0.5% of binder, 0.2% of polyethylene glycol, 0.1% of N-octyl alcohol and 0.1% of pore-forming agent to obtain slurry B, then feeding the slurry B into a centrifugal spray dryer to carry out centrifugal spray granulation, wherein the drying gas is N₂The feeding speed is controlled at 350mL/h, the centrifugal speed is 9000r/min, and the inlet and outlet temperatures of a spray dryer are 350 ℃ and 170 ℃ respectively, so that the rare earth niobate (YNbO) with the powder particle size of 20-80 mu m can be obtained₄) A spherical powder.

step 1: YNbO prepared by the method₄And EuNbO₄The powders were mixed to 6 parts of mixed ceramic powder as shown in Table 1.

Step 2: carrying out surface roughening treatment on a base material (nickel-based superalloy in the embodiment), then depositing a metal bonding layer with the thickness of 100 microns on the surface in advance, wherein the component of the metal bonding layer is NiCrAlY, and sequentially depositing 6 parts of mixed ceramic powder obtained in the step 1 on the metal bonding layer by adopting an APS (advanced photo-deposition system) method to obtain the multi-gradient rare earth niobate thermal barrier coating, wherein the thickness of the coating is 150 microns.

TABLE 1 YNbO in example 1₄And EuNbO₄Volume fraction table of powder

Number n of gradient layers	YNbO₄Volume fraction (%)	EuNbO₄Volume fraction (%)
			1	100	0
2	80	20
			3	60	40
4	40	60
			5	20	80
6	0	100

Example 2:

the difference from example 1 is that, referring to table 2, the number of gradient layers n is 11, the thickness of the rare earth niobate coating is 200 μm, and YNbO in each gradient layer₄And EuNbO₄The volume fractions of the powders are shown in table 2 below.

Table 2 shows YNbO in each gradient layer of example 2₄And EuNbO₄Volume fraction table of powder

Example 3:

and embodiments thereofThe difference in 1 is that, referring to table 3, the number of gradient layers n of the ceramic coating is 21, the thickness of the rare earth niobate coating is 300 μm, and YNbO in each gradient layer₄And EuNbO₄The volume fractions of the powders are shown in table 3 below.

Table 3 shows YNbO in each gradient layer of example 3₄And EuNbO₄Volume fraction table of powder

Example 4:

the difference from example 2 is that this example also includes ErNbO prepared by the method of example 1₄Powder and ScNbO₄Powder, the number of gradient layers n is 11, the thickness of the rare earth niobate coating is 200 mu m, and YNbO in each gradient layer₄、EuNbO₄、 ErNbO₄And ScNbO₄The volume fractions of the powders are shown in Table 4 below.

Table 4 shows the volume fraction (%)

Number n of gradient layers	YNbO₄	EuNbO₄	ErNbO₄	ScNbO₄
					1	50	0	50	0
2	45	5	45	5
					3	40	10	40	10
4	35	15	35	15
					5	30	20	30	20
6	25	25	25	25
					7	20	30	20	30
8	15	35	15	35
					9	10	40	10	40
10	5	45	5	45
					11	0	50	0	50

Example 5:

the difference from the example 2 is that the ceramic powder in the scheme is LaTaO₄And DyTaO₄The ceramic powder was prepared in the same manner as in example 1, with the number of gradient layers n being 11, the thickness of the rare earth tantalate coating layer being 200 μm, and the LaTaO in each gradient layer₄And DyTaO₄The volume fractions of the powders are shown in Table 5 below.

Table 5 shows LaTaO in each gradient layer of example 5₄And DyTaO₄Volume fraction table of powder

Number n of gradient layers	LaTaO₄Volume fraction (%)	DyTaO₄Volume fraction (%)
			1	100	0
2	90	10
			3	80	20
4	70	30
			5	60	40
6	50	50
			7	40	60
8	30	70
			9	20	80
10	10	90
			11	0	100

Example 6:

the difference from example 4 is that the ceramic powder in this case is YTaO₄、ErTaO₄、HoTaO₄And ScTaO₄The ceramic powder was prepared in the same manner as in example 1, with the number of gradient layers n being 11, the thickness of the rare earth tantalate coating layer being 200 μm, and YNbO in each gradient layer₄、EuNbO₄、ErNbO₄And ScNbO₄The volume fractions of the powders are shown in Table 6 below.

Table 6 shows the volume fraction (%)

Comparative example 1:

the difference from the example 1 is that the rare earth niobate ceramic powder in the comparative example 1 is formed by high-temperature sintering after ball milling.

Comparative example 2:

the difference from example 1 is that YNbO is first introduced in step 2₄Depositing the powder onto the metal bonding layer by APS method to obtain coating A, and adding EuNbO₄The powder was deposited on coating A by the APS method to give coating B, the total thickness of coating A and coating B being 150. mu.m.

Selecting the material test pieces obtained in the examples 1-6 and the comparative examples 1-2 to perform thermal conductivity experiment detection:

the test is carried out by using a laser thermal conductivity meter, and the test results are shown in the following table 7 at the temperature of 800K:

table 7 shows the thermal conductivities (W.m) of examples 1 to 6 and comparative examples 1 to 2^-1·K^-1)

From table 7 above, it follows:

1. the thermal conductivity of the rare earth tantalate or niobate ceramic coating obtained by the technical scheme in the application is not more than 1.20 W.m^-1·K^-1The requirement of the thermal barrier coating on low thermal conductivity is met, and the comparative example shows that the thermal conductivity of the ceramic coating without component design is obviously higher, and the thermal conductivity of the rare earth niobate powder obtained by high-temperature sintering meets the requirement of the thermal barrier coating, but is still higher than that of the ceramic powder prepared by adopting a coprecipitation method in the application.

2. By designing different rare earth tantalate or niobate ceramic powders, a multi-element gradient coating is obtained, namely, the volume fraction of at least one ceramic component in the coating is continuously changed, so that the thermal barrier coating can be ensured to have the original rare earth tantalate or niobate (RENB/TaO)₄) The thermal barrier coating obtained by deposition in such a way that the components between the gradient coatings are in a gradual change form, the interfaces formed between the gradient coatings are few, so that the interface effect is weak, and the most important point is that the thermal barrier coating obtained by deposition in each gradient coating is low in expansion coefficient and thermal conductivity is greatly reduced at the same timeDuring the deposition of the gradient coating, the components of each layer can be continuously diffused, so that the interface effect is continuously weakened, and the thermal conductivity is reduced, while the thermal conductivity of the example 3 in the application is the lowest, which shows that the higher the number of the gradient layers is, the more remarkable the improvement on the thermal conductivity is.

The foregoing is merely an example of the present invention and common general knowledge of the known specific materials and characteristics thereof has not been described herein in any greater extent. It should be noted that, for those skilled in the art, without departing from the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent. The scope of the claims of the present application shall be determined by the contents of the claims, and the description of the embodiments and the like in the specification shall be used to explain the contents of the claims.

Claims

1. A preparation method of a rare earth tantalate or niobate thermal barrier coating comprises the following steps:

step 1: taking more than two different rare earth tantalates RETaO₄Or niobate RENbO₄Mixing ceramic powder into n parts of mixed ceramic powder, wherein the volume fraction of at least one rare earth tantalate or niobate ceramic component in the n parts of mixed ceramic powder is continuously increased or decreased;

step 2: sequentially depositing the n parts of mixed ceramic powder obtained in the step (1) on a base material to obtain a multi-gradient rare earth tantalate or niobate thermal barrier coating;

in the step 1, n is 11-21;

the preparation method of the rare earth tantalate or niobate powder comprises the following steps:

step 1: according to the structural formula RETaO₄Or RENbO₄Get RE₂O₃Dissolving the powder in concentrated nitric acid to a pH below 1.5, adding TaOCl₃Or NbOCl₃Dropwise adding the solution, continuously stirring, simultaneously adding ammonia water to stabilize the pH of the system to 9-10, continuously stirring in a water bath environment, washing the precipitate with absolute ethyl alcohol or deionized water successively until the pH is =7, and obtaining the compoundDrying the filter cake in an oven, sieving and sintering in a medium-temperature environment, and sieving the sintered powder again for later use;

2. The method for preparing a rare earth tantalate or niobate thermal barrier coating of claim 1, wherein: the thickness of the rare earth tantalate or niobate thermal barrier coating is 150-300 mu m.

3. The method for preparing a rare earth tantalate or niobate thermal barrier coating of claim 1, wherein: and in the step 2, a metal bonding layer with the thickness of 100-150 mu M is deposited on the surface of the base material in advance, wherein the metal bonding layer comprises MCrAlY, and M is Ni or Co.

4. The method for preparing a rare earth tantalate or niobate thermal barrier coating of claim 1, wherein: and in the step 2, the coating deposition treatment is carried out by adopting an APS, HVOF, EB-PVD or supersonic speed electric arc spraying method.

5. The method for preparing a rare earth tantalate or niobate thermal barrier coating of claim 1, wherein: in step 1, TaOCl₃The dropping speed of the solution is 200-400 mL/min, the temperature of the water bath is 50-100 ℃, the stirring time is 30-120 min, the drying temperature is 80-120 ℃, and the drying time is 5-10 h; the medium-temperature sintering temperature is 900-1100 ℃, the time is 3-5h, and the used sieve is 300-500 meshes.