A thermal barrier coating heat insulation performance testing device and heat insulation performance evaluation method

Abstract

The application provides a heat insulation performance testing device for thermal barrier coating, which comprises a hollow cavity with a through mold loading groove, a cylindrical graphite mold placed in the mold loading groove, and a temperature rising device and a first temperature measuring device which are opposite to each other and face one end surface of the cylindrical graphite mold; wherein one end surface of the cylindrical graphite mold is sprayed with a thermal barrier coating to be measured, and the side surface of the cylindrical graphite mold is sprayed with a heat insulation coating. The heat insulation condition of the heat insulation performance testing device for thermal barrier coating is set by spraying the heat insulation coating on the side surface of the graphite mold, and the heat insulation condition is set ingeniously so that the device can meet the Fourier heat transfer law under one-dimensional condition as much as possible, unnecessary heat escape is avoided, the heat flow on the coating surface completely realizes conduction to the back of the substrate, and thus, the measurement error caused by neglecting is avoided, and the result is accurate and reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for evaluating thermal barrier coatings, in particular to a device for testing the thermal insulation performance of thermal barrier coatings and a method for evaluating the thermal insulation performance of thermal barrier coatings, to jointly evaluate the high-temperature thermal insulation effect of thermal barrier coatings. BACKGROUND

[0002] With the development of the aviation industry, the high thrust-to-weight ratio (the ratio of the thrust generated by the engine to its own weight) of the aero-engine is continuously improved, and the engine turbine inlet temperature is continuously rising, and the requirement for its thermal efficiency is also continuously improved. The existing high-temperature alloy and cooling technology cannot meet this growing demand.

[0003] Thermal barrier coatings (TBCs) are one of the key core technologies of aero-engines, and are widely used on high-temperature alloy blades of aero-engines, having the functions of high-temperature thermal insulation, oxidation resistance, corrosion resistance, and wear resistance. Under the premise that high-temperature alloy research and cooling technology research cannot meet the above requirements, it is particularly important to improve the thermal insulation performance of thermal barrier coatings so that high-temperature alloy blades can work at higher temperatures without strength degradation. Therefore, how to scientifically and accurately characterize the thermal insulation performance of thermal barrier coatings is an important scientific proposition.

[0004] Currently, there is no more scientific and effective means for testing the thermal insulation performance of thermal barrier coatings. A commonly used method for testing the thermal insulation temperature difference (temperature difference between the two surfaces of the thermal barrier coating material) of thermal barrier coatings is to measure the temperature of the surface and the back of the coating sample at the same time during the high-temperature high-heat flux density cycle thermal test (Burner Rig Test, BRT) of the thermal barrier coating, and then measure the thermal insulation performance of the coating. However, this method is an auxiliary method, and the thermal insulation temperature difference data is obtained during the BRT process. If it is only used to test the thermal insulation effect of the coating, the cost is too high. In addition, during the BRT test process, the side of the coating sample will contact other materials with high thermal conductivity, and part of the heat will escape from the side, so the heat flow on the surface of the coating cannot be completely conducted to the back of the substrate, resulting in a certain deviation in the measurement result.

[0005] That is, the current thermal barrier coating thermal insulation performance test technology has the following two shortcomings: (1) the current widely used thermal barrier coating thermal insulation performance test technology BRT, the essence is the high temperature strong heat flux density cycle thermal test of the thermal barrier coating, the thermal barrier coating sample is heated and cooled multiple times, the purpose is to test the thermal cycle performance of the thermal barrier coating, only incidental thermal insulation performance test results of the thermal barrier coating are obtained, if the thermal insulation performance of the coating is tested specially, the cost is too high; (2) in the BRT test process, the side of the coating sample inevitably contacts with other materials with high thermal conductivity, so that part of the heat escapes from the side, the heat flow on the surface of the coating cannot be completely conducted to the back of the substrate, so that the measurement result has certain deviation. SUMMARY

[0006] The purpose of the present application is to provide a thermal barrier coating thermal insulation performance test device and a thermal insulation performance evaluation method to jointly evaluate the high temperature thermal insulation effect of the thermal barrier coating.

[0007] In order to achieve the above purpose, the present application provides a thermal barrier coating thermal insulation performance test device, which comprises a hollow cavity with a through mold loading groove, a cylindrical graphite mold placed in the mold loading groove, and a temperature raising device and a first temperature measuring device opposite to each other at one end face of the cylindrical graphite mold; wherein one end face of the cylindrical graphite mold is sprayed with a thermal barrier coating to be measured, and the side of the cylindrical graphite mold is sprayed with a thermal insulation coating.

[0008] The cylindrical graphite mold is provided with a measuring inner groove penetrating to the center of the cylindrical graphite mold at the center of the side wall thereof; the hollow cavity is provided with a measuring opening on the side wall thereof, which is aligned with the position of the measuring inner groove; the thermal insulation performance test device further comprises a second temperature measuring device, the probe of which is installed to the center of the cylindrical graphite mold through the measuring inner groove and the measuring opening.

[0009] The measuring light spot of the first temperature measuring device is aligned with the center position of the thermal barrier coating to measure the temperature T1 of the center position of the thermal barrier coating.

[0010] The temperature raising device is an oxyacetylene flame spraying device.

[0011] The first temperature measuring device is an infrared temperature measuring instrument, and the second temperature measuring device is a thermocouple.

[0012] The thermal conductivity of the material of the thermal insulation coating is less than 2.5 W / m·K.

[0013] The heat insulation performance testing device of the thermal barrier coating further comprises a mold support frame, a high-temperature-resistant iron clamp installed on the mold support frame for clamping the hollow cavity, a stopwatch for recording the heating time of the heating device, and a tripod for installing the heating device.

[0014] In another aspect, the present application provides a method for evaluating the heat insulation performance of a thermal barrier coating, comprising:

[0015] S1: building a heat insulation performance testing device of a thermal barrier coating according to the above;

[0016] S2: turning on the heating device to heat the surface of the thermal barrier coating, while using a stopwatch, a first temperature measuring device and a second temperature measuring device to record the temperature T1 of the center position of the thermal barrier coating and the center temperature T3 of the cylindrical graphite mold at different times;

[0017] S3: performing inversion calculation to obtain the back temperature T2 of the thermal barrier coating, and obtaining the heat insulation temperature difference ΔT = T1-T2 of the thermal barrier coating according to the back temperature T2 of the thermal barrier coating and the temperature T1 of the center position of the thermal barrier coating;

[0018] S4: calculating the effective thermal conductivity k of the thermal barrier coating according to the heat transfer formula and the thick coating test piece method eff ;

[0019] S5: jointly evaluating the heat insulation performance of the thermal barrier coating based on the heat insulation temperature difference ΔT and the effective thermal conductivity k eff .

[0020] The step S1 comprises:

[0021] S11: installing the cylindrical graphite mold into a through mold installation slot of the hollow cavity; wherein one end face of the cylindrical graphite mold is sprayed with the thermal barrier coating to be measured, the side face of the cylindrical graphite mold is sprayed with a thermal insulation coating, and the cylindrical graphite mold is provided with a measurement inner slot penetrating to the center of the cylindrical graphite mold at the center of the side wall thereof; the hollow cavity is provided with a measurement opening on the side wall thereof;

[0022] S12: adjusting the hollow cavity and the cylindrical graphite mold so that the measurement inner slot is aligned with the measurement opening, and installing the probe of the second temperature measuring device through the measurement inner slot and the measurement opening to the center of the cylindrical graphite mold to measure the center temperature T3 of the cylindrical graphite mold;

[0023] S13: adjusting the measurement spot of the first temperature measuring device to align with the center position of the thermal barrier coating to measure the temperature T1 of the center position of the thermal barrier coating;

[0024] S14: The temperature raising device and one of the end faces of the cylindrical graphite mold are made to face each other, and the position of the temperature raising device is adjusted so that the spot diameter of the heating flame of the temperature raising device matches the diameter of the thermal barrier coating.

[0025] The back temperature T2 of the thermal barrier coating is:

[0026]

[0027] wherein h2 is the heat exchange coefficient between the environment and the thermal barrier coating, T a represents the environment temperature, δ s is the distance from the center of the thermal cylindrical graphite mold to the base surface of the cylindrical graphite mold, T3 is the temperature measured by the second temperature measuring device, λ s is the effective thermal conductivity of the base of the cylindrical graphite mold.

[0028] The adiabatic condition of the thermal barrier coating heat insulation performance testing device of the present application is set by spraying the adiabatic coating on the side of the graphite mold, and the adiabatic condition is set ingeniously so that the device meets the Fourier heat conduction law under the one-dimensional condition as much as possible, unnecessary heat is avoided, the heat flow on the coating surface is completely conducted to the back of the base, thereby avoiding causing a non-negligible measurement error, and the result is accurate and reliable.

[0029] Compared with the BRT technology, the thermal barrier coating heat insulation performance testing device of the present application uses less coating material, greatly reducing the cost; in addition, compared with the BRT technology which repeatedly heats and cools the thermal barrier coating, the thermal barrier coating heat insulation performance evaluation method of the present application directly obtains the target result after one heating, and is simple, convenient, practical, and high in precision.

[0030] The thermal barrier coating heat insulation performance evaluation method of the present application introduces the thermal barrier coating heat insulation temperature difference ΔT and the effective thermal conductivity k eff Double standard, combined evaluation of the high-temperature heat insulation effect of the thermal barrier coating, compared with the current single standard evaluation system, the characterization of the thermal barrier coating heat insulation performance is more persuasive and complete. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a structural schematic diagram of a thermal barrier coating heat insulation performance testing device according to an embodiment of the present application;

[0032] Figure 2 is a structural framework diagram of a thermal barrier coating heat insulation performance testing device according to an embodiment of the present application;

[0033] Figure 3 is a structural schematic diagram of a cylindrical graphite mold;

[0034] Figure 4A schematic diagram of a thermal conductivity model of a thermal barrier coating of a multi-layer structure;

[0035] Figure 5 A flow chart of a method for evaluating the thermal insulation performance of a thermal barrier coating according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present application will be described below in detail with reference to the accompanying drawings.

[0037] As shown in Figure 1 and Figure 2 A thermal insulation performance testing device for a thermal barrier coating according to an embodiment of the present application is shown in Figure 1 and Figure 2 The thermal insulation performance testing device for a thermal barrier coating includes a hollow cavity 1 having a through-type mold loading slot 11, a cylindrical graphite mold 2 placed in the mold loading slot 11, and a temperature raising device 3 and a first temperature measuring device (not shown in the figure) which are opposite to each other at one end face of the cylindrical graphite mold 2. The end face of the cylindrical graphite mold 2 facing the temperature raising device 3 is sprayed with a thermal barrier coating 21 to be measured.

[0038] Thus, the hollow cavity 1 has a certain thickness and is open at both sides to achieve through-type, one of the openings is the position of the thermal barrier coating spraying surface of the cylindrical graphite mold, and the other opening forms air convection heat exchange with the outside.

[0039] In the present embodiment, the mold loading slot 11 is a square slot, and the material of the hollow cavity 1 is graphite. The temperature raising device 3 is an oxyacetylene flame spraying device, which is arranged such that the center of the sprayed oxyacetylene flame is aligned with the center position of the thermal barrier coating 21 to ensure that the coating sample surface is uniformly heated. The oxyacetylene flame spraying device has a gas path pipe, the inner part of which is separated into two paths and is in communication with two paths of gas, respectively, and the two paths of gas are oxygen and acetylene, respectively, so that oxygen and acetylene gas can be introduced into the two paths of gas path pipe in a certain proportion, and when the two paths of gas reach the pipe opening of the gas path pipe, ignition reaction occurs, and oxyacetylene flame is generated. The first temperature measuring device is an infrared temperature measuring instrument, and the measurement spot of the first temperature measuring device is aligned with the center position of the thermal barrier coating 21 to measure the temperature T1 of the center position of the thermal barrier coating 21.

[0040] The side surface of the cylindrical graphite mold 2 is sprayed with a thermal insulation coating 22, so that the side surface of the cylindrical graphite mold 2 is considered as a thermal insulation condition, and the heat flow only propagates along one dimension direction (the coating thickness direction of the thermal barrier coating 21) from the surface of the sprayed thermal barrier coating 21 to the back of the base of the cylindrical graphite mold 2, so that the experimental device satisfies the Fourier heat conduction law under one-dimensional condition, and subsequent data processing is facilitated. The coating is realized by using plasma spraying process.

[0041] In addition, the outer diameter of the cylindrical graphite mold 2 after spraying the thermal insulation coating 22 meets the tolerance with the width of the inner wall of the hollow cavity 1, facilitating the installation of the cylindrical graphite mold. That is, the outer diameter of the cylindrical graphite mold 2 after spraying the thermal insulation coating 22 meets the width of the inner wall of the hollow cavity 1 at the mold installation groove 11:

[0042] D c / 2+ε=W gi / 2,

[0043] Wherein, D c is the outer diameter of the cylindrical graphite mold 2 after spraying the thermal insulation coating 22, ε is the tolerance, and W gi is the width of the inner wall of the hollow cavity 1 at the mold installation groove 11.

[0044] The thermal insulation coating 22 adopts a material with relatively low thermal conductivity, which can be a rare earth zirconate coating material with relatively low thermal conductivity such as La2Zr2O7, Sm2Zr2O7, Gd2Zr2O7, or a rare earth compound material with lower thermal conductivity such as A2B2O7(A=La, Sm, Gd; B=Zr, Ce) and tantalate, and the lower the thermal conductivity, the better. The purpose is mainly to regard the side of the graphite cylinder as an adiabatic condition, and the heat flow is only in one dimension (coating thickness direction), propagating from the sprayed coating surface to the back of the substrate, so that the experimental device meets the Fourier heat transfer law under one-dimensional condition. In summary, the material of the thermal insulation coating 22 includes rare earth zirconate material, tantalate material, cerate material, selenate material, magnesium aluminate material or phosphate material, etc. The thermal conductivity of the material of the thermal insulation coating 22 is less than 2.5 W / m·K, and the candidate materials of the thermal barrier coating are shown in Table 1 as follows.

[0045] Table 1 can be used as a candidate material for thermal barrier coating

[0046]

[0047]

[0048] In addition, as Figure 3 shown, the cylindrical graphite mold 2 is provided with a measuring inner groove 23 penetrating to the center of the cylindrical graphite mold 2 at the center of the side wall of the cylindrical graphite mold 2.

[0049] Correspondingly, please also refer to Figure 1The hollow cavity 1 is provided with a measuring opening 12 on the side wall thereof, which is aligned with the measuring inner groove 23. In addition, the heat barrier coating thermal insulation performance testing device further comprises a second temperature measuring device (not shown in the figure), which is inserted into the measuring opening 12 and the measuring inner groove 23, and the probe of the second temperature measuring device is located at the center of the cylindrical graphite mold 2 to measure the center temperature T3 of the cylindrical graphite mold 2.

[0050] Preferably, the second temperature measuring device is a thermocouple. The thermocouple can be a K-type thermocouple or an S-type thermocouple, which is used to measure the temperature of the key point. The size of the measuring inner groove 23 is flexibly controllable. First, the depth of the measuring inner groove can ensure that it reaches the internal center of the cylindrical graphite mold 2. Second, the opening size of the inner groove can ensure that the probe of the second temperature measuring device (i.e. the thermocouple probe) can extend into it. The fixing method of the thermocouple can be fixed by embedding or fixed by spot welding at the embedding point.

[0051] In the embodiment, the specific dimensions of the self-made hollow graphite cavity and the cylindrical graphite mold are as follows: the overall external dimensions of the hollow cavity 1 are 40mm×40mm×40mm, the opening shape of the mold loading groove 11 is a square, and the opening size is 30mm×30mm (i.e. the width of the inner wall of the hollow cavity 1 is 30mm, and the tolerance is 0-0.1mm); the opening shape of the measuring inner groove 23 is a square, and the opening size is 5mm×5mm. The outer diameter of the cylindrical graphite mold 2 after coating the heat insulation coating 22 is 30mm, and the tolerance is 0- -0.1mm; the length of the cylindrical graphite mold 2 is 40mm, and the opening shape of the measuring inner groove 23 is a square, and the opening size is 5mm×5mm.

[0052] In addition, the heat barrier coating thermal insulation performance testing device further comprises a mold support frame, a high-temperature-resistant iron clamp installed on the mold support frame, a stopwatch, and a tripod. The high-temperature-resistant iron clamp is used to clamp the hollow cavity 1, and the mold support frame is used to support and fix the high-temperature-resistant iron clamp and the hollow cavity 1 clamped thereon. The stopwatch is used to record the heating time of the heating device 3. The tripod is used to install the heating device 3.

[0053] As shown in Figure 5 Based on the heat barrier coating thermal insulation performance testing device described above, the heat barrier coating thermal insulation performance evaluation method realized thereby comprises the following steps:

[0054] Step S1: build the heat barrier coating thermal insulation performance testing device described above, which comprises:

[0055] Step S11: a cylindrical graphite mold 2 is loaded into a through mold loading slot 11 of a hollow cavity 1; wherein an end face of the cylindrical graphite mold 2 is sprayed with a thermal barrier coating 21 to be measured, a side face of the cylindrical graphite mold 2 is sprayed with a thermal insulation coating 22, and a measuring inner slot 23 is provided at the center of the side wall of the cylindrical graphite mold 2 and penetrates to the center of the cylindrical graphite mold 2; and the hollow cavity 1 is provided with a measuring opening 12 on the side wall thereof;

[0056] In the step S11, the hollow cavity 1 and the cylindrical graphite mold 2 are obtained by the following way:

[0057] Step S111: a measuring inner slot 23 with a length and width of 5 mm along the wall and a depth of 20 mm is opened on the side face of the base of the cylindrical graphite mold 2 with a diameter of 30 mm and a length of 40 mm; a square graphite block with a size of 40x40x40 mm 3 is taken as the base of the hollow cavity 1, and a 30x30x40 mm 3 two-end opening mold loading slot 11 is cut out therefrom, and a 5x5x5 mm 3 small square slot communicating with the inside is further opened on the side wall of the base of the hollow cavity 1 as the measuring opening 12.

[0058] Step S112: the thermal barrier coating 21 to be measured is sprayed on an end face of the cylindrical graphite mold 2.

[0059] In this embodiment, the thermal barrier coating 21 is composed of two layers, one layer close to the cylindrical graphite mold 2 is a metal bonding layer CoNiCrAlY, NiCoCrAlY or FeCrAlYHf, etc., and the top layer is an 8wt.% Y2O3 stabilized ZrO2 coating.

[0060] Step S113: a thermal insulation material is sprayed on the side face of the cylindrical graphite mold 2.

[0061] The thermal insulation material is a rare earth zirconate or a rare earth compound material with low thermal conductivity such as tantalate, etc., with a thickness of about 100 μm, so as to ensure that the size of the cylindrical graphite mold 2 is matched with the size of the hollow cavity 1.

[0062] Step S12: the hollow cavity 1 and the cylindrical graphite mold 2 are adjusted so that the measuring inner slot 23 is aligned with the measuring opening 12, and the probe of the second temperature measuring device is installed to the center of the cylindrical graphite mold 2 through the measuring inner slot 23 and the measuring opening 12, so as to measure the center temperature T3 of the cylindrical graphite mold 2.

[0063] Step S13: Adjust the measuring spot of the first temperature measuring device to align with the center position of the thermal barrier coating 21 to measure the temperature T1 of the center position of the thermal barrier coating 21.

[0064] Step S14: Align the temperature raising device 3 with one of the end faces of the cylindrical graphite mold 2, and adjust the position of the temperature raising device 3 to match the spot diameter of the heating flame of the temperature raising device 3 with the diameter of the thermal barrier coating 21. This is to make the temperature gradient dT / dR along the radial direction small, and to ensure that the whole coating surface is heated evenly.

[0065] In this embodiment, the temperature raising device 3 is fixed on a tripod, and the position of the temperature raising device 3 is adjusted to match the spot diameter of the heating flame of the temperature raising device 3 with the diameter of the thermal barrier coating 21 as much as possible.

[0066] Step S2: Turn on the temperature raising device 3 to heat the surface of the thermal barrier coating 21, and use a stopwatch, the first temperature measuring device and the second temperature measuring device to record the temperature T1 of the center position of the thermal barrier coating 21 and the center temperature T3 of the cylindrical graphite mold 2 at different time, to obtain the evolution curve T1=f(t) of T1 with time and the evolution curve T3=g(t) of T3 with time.

[0067] Step S3: Use formula (7) to perform inversion calculation to obtain the back temperature T2 of the thermal barrier coating (correspondingly, the evolution curve T2=h(t) of the back temperature T2 of the thermal barrier coating with time is obtained). The thermal insulation temperature difference ΔT=T1-T2 of the thermal barrier coating is obtained according to the back temperature T2 of the thermal barrier coating and the temperature T1 of the center position of the thermal barrier coating 21.

[0068] Since the thermal conductivity of graphite is very good, the thermal conductivity is 129 W / (m·K), which is much larger than the thermal conductivity of the coating, so it can be considered that the radial temperature gradient dT / dn of the cylindrical graphite mold is 0.

[0069] That is, the temperature difference between the back temperature T2 of the thermal barrier coating and the temperature T1 of the center position of the thermal barrier coating 21 (the height difference of the two key curves T1=f(t) and T2=h(t)) is the thermal insulation temperature difference of the coating.

[0070] According to the Fourier heat transfer law, in three-dimensional space, the heat conduction equation can be written as:

[0071]

[0072] In the formula, T is the transient temperature, t is the time, ρ is the density of the heat source, k is the thermal conductivity, and n is the radial direction. x ,k y ,k z ​effective thermal conductivities in three directions, C is the specific heat capacity, q v is the internal heat source intensity of the corresponding space.

[0073] For the plasma coating (i.e. thermal barrier coating 21), the thickness is thin, and the internal heat source intensity can be considered as 0, i.e. q v = 0. Since the side of the cylindrical graphite mold is considered to be adiabatic, i.e. dT / dn = 0, the heat flow only propagates along the height direction of the cylinder, i.e. only one dimension of Fourier heat conduction needs to be considered, and thus the above formula can be written as:

[0074]

[0075] Therefore, theoretically, the effective thermal conductivity k eff of the thermal barrier coating 21 along the thickness direction (spraying direction) of the coating can be calculated as follows:

[0076]

[0077] where h and W are the average thickness and width of the thermal barrier coating model respectively, ΔT is the temperature difference between the top and bottom surfaces of the thermal barrier coating model, τ bot is the lower boundary of the model, with a normal unit vector k is the intrinsic thermal conductivity of the thermal barrier coating, and ▽T represents the temperature gradient, dτ represents the distance differential along the thickness direction of the thermal barrier coating.

[0078] The effective thermal conductivity k eff is different from the coating thermal conductivity k in that when the coating does not have defects (pores, microcracks), which is an ideal case, k eff = k, and in fact irregular micro-defects usually exist inside the coating, so k eff is generally not equal to k, and is generally smaller than k.

[0079] In the present application, the back temperature T2 of the thermal barrier coating is first calculated to obtain the effective thermal conductivity λ c of the thermal barrier coating, and then the specific calculation process of the heat insulation temperature difference ΔT and the effective thermal conductivity λ c of the thermal barrier coating is as follows:

[0080] q in = -q out (4)

[0081]

[0082]

[0083]

[0084] qin qin refers to the heat flowing into the inside of the thermal barrier coating model from the outside out qout refers to the heat flowing out of the inside of the thermal barrier coating model; λ c , λ s are the effective thermal conductivity of the thermal barrier coating and the effective thermal conductivity of the substrate of the cylindrical graphite mold (unit: W / m·K) respectively, and the effective thermal conductivity of the thermal barrier coating is measured based on the thick coating block. δ c , δ s are the thickness of the thermal barrier coating and the distance from the center of the cylindrical graphite mold to the surface of the substrate of the cylindrical graphite mold (m) respectively. T1, T2, T3 are the surface temperature of the thermal barrier coating, the back temperature of the thermal barrier coating and the temperature measured by the second temperature measuring device (℃) respectively, and h2 is the heat exchange coefficient between the environment and the thermal barrier coating, T a represents the ambient temperature.

[0085] Finally, the insulation temperature difference ΔT = T1-T2 is obtained.

[0086] Step S4: The effective thermal conductivity k eff of the thermal barrier coating 21 is calculated according to the heat transfer formula (i.e., formula (1)) and the thick coating test piece method.

[0087] The measurement of the effective thermal conductivity k eff of the thermal barrier coating is based on the calculation formula of the thermal conductivity according to the Neumann-Kopp rule:

[0088] k eff = α·C P · ρ coating (1-1.33ψ) (8)

[0089] In the formula, α is the thermal diffusivity (m 2 / s); C p is the specific heat capacity of the coating material at constant pressure (J / (kg·℃)); ρ coating is the density of the coating (kg / m 3 ); and ψ is the porosity of the coating, which can be determined by the image method.

[0090] The ceramic coating (i.e., the thermal barrier coating to be measured) is sprayed on a graphite substrate with a diameter of 13 mm, the coating thickness is about 1.1-1.2 mm, and the sprayed shape is circular, and then the ceramic graphite sheet with a size of Ф12.7 mm×2.0 mm is peeled off from the graphite substrate, and the thermal diffusivity α and the specific heat capacity C p of the coating are tested by the LFA 427 type laser thermal conductivity instrument. The density ρ coating of the coating can be determined by the Archimedes drainage method with the aid of an electronic analytical balance and a very thin copper wire, and the calculation formula is:

[0091]

[0092] m1=F / g, m2=F' / g represent the readings of the electronic analytical balance when the sample is suspended in air and in water respectively, and the parameter m Cu represents the mass of the copper wire in air. m1=F / g, m2=F' / g represent the readings of the electronic analytical balance when the sample is suspended in air and in water respectively. Thus, the thick coating sample method is realized.

[0093] And for the thermal barrier coating of the multilayer structure as shown in Figure 4 The total effective thermal conductivity of the multilayer structure is calculated as follows:

[0094]

[0095] The meanings of the parameters k i , t i are the thermal conductivity and thickness of the i-th layer coating respectively. The thermal barrier coating of the application can be a multilayer structure or a single layer structure.

[0096] It should be noted that the formulas (8)-(10) are used to calculate the thermal conductivity of the coating in the application, and the formulas (1)-(3) are only theoretical expressions. Formula (3) is mainly a theoretical expression for the effective thermal conductivity of the overall coating. The effective thermal conductivity k eff of the application is the calculation result of formula (8). Formula (10) is an expression for the overall effective thermal conductivity of the thermal barrier coating when the thermal barrier coating is a multilayer structure. And formula (10) is an expression for the overall effective thermal conductivity of the multilayer structure coating, which is obtained based on the parallel circuit model, i.e. the total current = the sum of the currents of each path.

[0097] Step S5: Based on the heat insulation temperature difference ΔT and the effective thermal conductivity k eff The heat insulation performance of the thermal barrier coating 21 is jointly evaluated.

[0098] The heat insulation temperature difference ΔT=T1-T2 and the effective thermal conductivity k eff of the application are finally obtained. The two standards are combined to evaluate and select the high-temperature heat insulation effect of the thermal barrier coating.

[0099] The heat insulation performance testing device of the thermal barrier coating of the application solves the following three problems by using the basic principle of Fourier heat transfer law and the thick coating sample method:

[0100] (1) Compared with the BRT technology, the amount of coating material used is small, which greatly reduces the cost. And compared with the BRT technology which repeatedly heats and cools the thermal barrier coating, the method of the application directly obtains the target result once heated, which is simple, convenient, practical, high-precision, and easy to operate.

[0101] (2) Compared with the BRT technology, the adiabatic condition of the thermal barrier coating heat insulation performance testing device of the application is set by spraying the adiabatic coating on the side of the graphite mold, and the adiabatic condition is set ingeniously to make the device meet the Fourier heat transfer law as much as possible under the one-dimensional condition, avoid unnecessary heat escape, make the heat flow on the coating surface completely realize conduction to the back of the substrate, thereby avoiding causing a non-negligible measurement error, and making the result accurate and reliable.

[0102] (3) Compared with the currently commonly used single standard evaluation system, the thermal barrier coating heat insulation performance evaluation method of the application introduces the thermal barrier coating heat insulation temperature difference ΔT and the effective thermal conductivity k eff Double standards, combined evaluation of the high-temperature heat insulation effect of the thermal barrier coating, compared with the currently commonly used single standard evaluation system, the characterization of the thermal barrier coating heat insulation performance is more convincing and complete.

[0103] The above is only a preferred embodiment of the application, and is not intended to limit the scope of the application. The above embodiment of the application can be variously changed. Any simple, equivalent changes and modifications made in accordance with the content of the claims and the specification of the application fall within the scope of protection of the patent. The application is not described in detail.

Claims

1. A method for evaluating the thermal barrier property of a thermal barrier coating, characterized by, include: Step S1: Construct a thermal barrier coating insulation performance testing device, which includes a hollow cavity with a through mold loading groove, a cylindrical graphite mold placed in the mold loading groove, and a heating device and a first temperature measuring device facing one end face of the cylindrical graphite mold; wherein, the thermal barrier coating to be tested is sprayed on one end face of the cylindrical graphite mold, and the side of the cylindrical graphite mold is sprayed with an insulating coating; the cylindrical graphite mold has a measuring inner groove extending through to the center of its side wall; the hollow cavity has a measuring opening on its side wall aligned with the measuring inner groove; the thermal barrier coating insulation performance testing device also includes a second temperature measuring device, the probe of which passes through the measuring inner groove and the measuring opening and is installed at the center of the cylindrical graphite mold; The thermal barrier coating consists of two layers, with the layer in close contact with the cylindrical graphite mold being a metal bonding layer; The cylindrical graphite mold has an outer diameter of 30 mm after being coated with an insulating coating, with a tolerance of 0 to -0.1 mm; the length of the cylindrical graphite mold is 40 mm; and the opening shape of the measuring inner groove is square, with an opening size of 5 mm × 5 mm. Step S2: Turn on the heating device to heat the surface of the thermal barrier coating, and at the same time use a stopwatch, a first temperature measuring device and a second temperature measuring device to record the temperature T1 at the center of the thermal barrier coating and the center temperature T3 of the cylindrical graphite mold at different times. Step S3: Perform inversion calculation to obtain the back temperature of the thermal barrier coating ; and obtain the insulation temperature difference of the thermal barrier coating according to the back temperature T2 of the thermal barrier coating and the temperature T1 of the center position of the thermal barrier coating . Step S4: Calculate the effective thermal conductivity of the thermal barrier coating according to the heat transfer formula and the thick coating test piece method ; Step S5: Based on the temperature difference of insulation and effective thermal conductivity The thermal barrier coating insulation performance is evaluated jointly; Step S1 includes: Step S11: Insert a cylindrical graphite mold into a through-hole mold insertion slot in a hollow cavity; wherein, a thermal barrier coating to be measured is sprayed on one end face of the cylindrical graphite mold, an insulating coating is sprayed on the side surface of the cylindrical graphite mold, and a measuring inner groove penetrating to the center of the cylindrical graphite mold is provided at the center of its side wall; a measuring opening is provided on its side wall of the hollow cavity; Step S12: Adjust the hollow cavity and cylindrical graphite mold so that the measuring inner groove and the measuring opening are aligned, and install the probe of the second temperature measuring device through the measuring inner groove and the measuring opening to the center of the cylindrical graphite mold to measure the center temperature T3 of the cylindrical graphite mold. Step S13: Adjust the measurement spot of the first temperature measuring device to align with the center position of the thermal barrier coating to measure the temperature of the center position of the thermal barrier coating ; Step S14: Make the heating device face one end face of the cylindrical graphite mold, and adjust the position of the heating device so that the diameter of the heating flame of the heating device matches the diameter of the thermal barrier coating, so that the temperature gradient dT / dR along the radial direction is small, and the entire coating surface is heated more uniformly.

2. The method for evaluating thermal barrier coating insulation performance according to claim 1, characterized by, The heating device is an oxyacetylene flame injection device.

3. The method of evaluating the thermal barrier properties of a thermal barrier coating as recited in claim 1, wherein, The first temperature measuring device is an infrared thermometer, and the second temperature measuring device is a thermocouple.

4. The method of evaluating the thermal barrier coating insulation performance according to claim 1, characterized by, The thermal conductivity of the material of the insulating coating is less than 2.5 W / m·K.

5. The method of evaluating the thermal barrier coating insulation performance according to claim 1, characterized by, The mould support frame, the high-temperature-resistant tongs, the stopwatch and the tripod are also included, the high-temperature-resistant tongs are used for clamping the hollow cavity, the stopwatch is used for recording the heating time of the temperature rising device, and the tripod is used for mounting the temperature rising device.

6. The method of evaluating the thermal barrier coating insulation performance according to claim 1, characterized by, The back temperature of the thermal barrier coating is: ， where h2 is the heat transfer coefficient between the environment and the thermal barrier coating, T a representing the ambient temperature, δ s is the distance from the center of the thermal cylindrical graphite mold to the base surface of the cylindrical graphite mold, T3 is the temperature measured by the second temperature measuring device, is the effective thermal conductivity of the base of the cylindrical graphite mold.

7. The method of evaluating the thermal barrier coating insulation performance according to claim 1, characterized by, The material of the thermal barrier coating includes a rare earth zirconate material, a tantalate material, a cerate material, a selenate material, a magnesium aluminate material, or a phosphate material.

Images