CN117092006A - Method for measuring porosity of irregular columnar structure of thermal barrier coating - Google Patents
Method for measuring porosity of irregular columnar structure of thermal barrier coating Download PDFInfo
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- CN117092006A CN117092006A CN202310970875.3A CN202310970875A CN117092006A CN 117092006 A CN117092006 A CN 117092006A CN 202310970875 A CN202310970875 A CN 202310970875A CN 117092006 A CN117092006 A CN 117092006A
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- 239000012720 thermal barrier coating Substances 0.000 title claims abstract description 85
- 238000000034 method Methods 0.000 title claims abstract description 60
- 230000001788 irregular Effects 0.000 title claims abstract description 52
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 162
- 239000011780 sodium chloride Substances 0.000 claims abstract description 80
- 239000011148 porous material Substances 0.000 claims abstract description 18
- 238000002411 thermogravimetry Methods 0.000 claims abstract description 4
- 239000011248 coating agent Substances 0.000 claims description 53
- 238000000576 coating method Methods 0.000 claims description 53
- 238000010438 heat treatment Methods 0.000 claims description 29
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 11
- 239000012466 permeate Substances 0.000 claims description 5
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- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 4
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- AZUYLZMQTIKGSC-UHFFFAOYSA-N 1-[6-[4-(5-chloro-6-methyl-1H-indazol-4-yl)-5-methyl-3-(1-methylindazol-5-yl)pyrazol-1-yl]-2-azaspiro[3.3]heptan-2-yl]prop-2-en-1-one Chemical compound ClC=1C(=C2C=NNC2=CC=1C)C=1C(=NN(C=1C)C1CC2(CN(C2)C(C=C)=O)C1)C=1C=C2C=NN(C2=CC=1)C AZUYLZMQTIKGSC-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume, or surface-area of porous materials
- G01N15/08—Investigating permeability, pore-volume, or surface area of porous materials
- G01N15/088—Investigating volume, surface area, size or distribution of pores; Porosimetry
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T50/00—Aeronautics or air transport
- Y02T50/60—Efficient propulsion technologies, e.g. for aircraft
Abstract
The invention discloses a method for measuring the porosity of an irregular columnar structure of a thermal barrier coating. The method mainly comprises the steps of sodium chloride fusion infiltration, thermogravimetric analysis, porosity calculation and the like, and the measuring method is simple and easy to implement, is insensitive to a sample treatment process, and has relatively universal applicability, relatively good repeatability and accuracy. The method is suitable for nondestructively and quantitatively characterizing the porosity of the thermal barrier coating with the irregular columnar structure with the complex pore structure, and has important significance for evaluating and predicting the thermal insulation and corrosion resistance of the thermal barrier coating with the irregular columnar structure.
Description
Technical Field
The invention belongs to the technical field of characterization and test of microstructure of a thermal barrier coating, and particularly relates to a method for measuring porosity of an irregular columnar structure of the thermal barrier coating.
Background
The thermal barrier coating is widely applied to advanced energy power equipment such as aeroengines, heavy-duty gas turbines and the like, and is one of key high-temperature protection technologies of hot end components. The thermal barrier coating mainly comprises a ceramic surface layer, a metal bonding layer and a high-temperature alloy substrate. Wherein, the ceramic surface layer has lower heat conductivity (-1-1.5W/(m.K)) due to the porous structure, and plays a main role in heat insulation in the thermal barrier coating system.
The traditional ceramic layer preparation process comprises Atmospheric Plasma Spraying (APS) and electron beam physical vapor deposition (EB-PVD), and the corresponding thermal barrier coating has a lamellar structure and a regular columnar structure respectively. The two coating pore structures are simpler, wherein the thermal barrier coating pore of the lamellar structure consists of lamellar microcracks and spherical holes, and has better heat insulation performance; the pore of the thermal barrier coating with the regular columnar structure consists of a vertical equal-width micron main crystal gap and a nano dendrite gap with the same orientation, and has higher strain tolerance (thermal barrier coating strength theory and detection technology, wang Tiejun and the like, and the national transportation university press, 2016, 12 months). In combination with the advantages of the two, a plasma spraying physical vapor deposition (PS-PVD) technology is rapidly developed in recent years, a corresponding thermal barrier coating has a feather-like irregular columnar structure, is composed of micron primary crystals with upper thicknesses and lower thicknesses and various oriented nano dendrites, and a coating pore is composed of primary crystal gaps with nonlinear changes in width and various oriented nano dendrite gaps and has a complex pore structure. The main crystal gap can provide a rapid channel for heat diffusion and corrosion medium invasion, so quantitative characterization of the dendrite gap of the irregular columnar structure has important significance for evaluating and predicting the heat insulation and corrosion resistance of the thermal barrier coating of the irregular columnar structure.
The existing thermal barrier coating microstructure characterization test method mainly comprises a mercury pressing method, a metallographic method and a wave signal method. The mercury porosimetry is characterized in that mercury is pressed into pores of a coating by applying pressure, and pore size distribution can be given by utilizing the corresponding relation between the pressure and the pore size, but mercury remained in the coating is difficult to take out, and a coating sample after testing cannot be used continuously (Bakan et al, J.Am. Ceram. Soc.98 (2015) 2647-2654); the metallographic method comprises the steps of cutting, grinding and polishing a damaged section of a coating, counting the porosity of a specific section by utilizing an image analysis technology, wherein key parameters such as a threshold value in the image processing process can be selected manually, the counting result is influenced by a plurality of factors such as the selected section, the image quality, the amplification factor and the like, and the cutting, grinding and polishing can cause irreversible damage to the coating (Cernusch et al, surf. Coat. Techn.272 (2015) 387-394); the wave signal method represented by ultrasonic wave, infrared thermal wave, microwave, terahertz pulse and the like is used for nondestructively detecting the amplitude or phase of reflected, transmitted or refracted signals by transmitting signals with specific frequencies to the coating, calculating the porosity of the coating by using an empirical function, and the testing and analyzing process relates to complex calculation methods such as Fourier transformation and inversion theory, and the like, and is only suitable for qualitative or semi-quantitative characterization (CN 113109294A, CN114199811A and CN 102564914A) of the porosity of a lamellar structure or a regular columnar structure with a simple pore structure and the porosity of an unmelted particle, and the irregular columnar structure thermal barrier coating with the complex pore structure is difficult to quantitatively characterize by adopting the method because the complex pore structure can cause larger fluctuation and influence on reflection, transmission and refraction behaviors of the wave signals.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: and carrying out nondestructive quantitative measurement on the porosity of the thermal barrier coating with the irregular columnar structure with the complex pore structure. Therefore, the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating is provided.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the method utilizes different volatilization characteristics of sodium chloride on the surface of the coating and in the pores, and quantitatively characterizes the internal porosity of the irregular columnar structure through thermogravimetric experiments. The method comprises the following steps:
step 1: heating the thermal barrier coating sample with the irregular columnar structure coated with sodium chloride in a crucible until the sodium chloride melts, so that molten sodium chloride permeates the thermal barrier coating sample under the action of gravity;
step 2: placing the thermal barrier coating sample with the irregular columnar structure permeated by sodium chloride into a thermogravimetric analyzer, heating to a temperature above the melting point of sodium chloride, and preserving heat until the quality of the sample is not changed;
step 3: and (3) taking a steady descending section of the thermal weight curve, and calculating the corresponding volatilization mass and volume of sodium chloride, wherein the ratio of the volume of the volatilized sodium chloride to the volume of the coating is the porosity of the irregular columnar structure of the thermal barrier coating.
Preferably, the coating amount of sodium chloride of the thermal barrier coating sample with the irregular columnar structure in the step 1 is not less than 60mg/cm 2 。
Preferably, the heating temperature in the step 1 is 850-900 ℃, the heating rate is 5-15 ℃/min, and the heat preservation time is 1-10min. In the experiment, the heating temperature is preferably 850-900 ℃, the heat preservation time is 1-10min, and the sodium chloride can thoroughly penetrate into the coating in the time range.
Preferably, the crucible in step 1 is an alumina ceramic crucible.
Preferably, the thermogravimetric analyzer in step 2 employs an alumina ceramic crucible.
Preferably, the heating temperature in the step 2 is 850-900 ℃, the heating rate is 10-20 ℃/min, and the heat preservation time is 5h. Experiments have shown that the time required for complete gasification of sodium chloride is substantially reduced when the heating temperature is 800 c and not reaching the theoretical melting point of sodium chloride (801 c) and 900 c, and if the temperature continues to be increased, it is disadvantageous to distinguish the thermal weight curve of the coating surface (corresponding to the rapid drop) versus the interior (corresponding to the steady drop) when the sodium chloride on the coating surface is less, and therefore the heating temperature is preferably 850-900 c.
Preferably, in the step 3, a linear fitting method is adopted to determine initial values and final values of a steady descending segment of the thermogravimetric curve.
Preferably, the coating volume in step 3 is calculated by multiplying the projected area of the coating by the thickness.
Compared with the prior art, the invention has the following beneficial effects:
according to the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating, disclosed by the invention, the porosity of the coating is characterized by utilizing the high-temperature volatilization characteristic of sodium chloride, sodium chloride is completely volatilized after an experiment, and sodium chloride residues are not existed in the coating; according to the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating, only the thermogravimetric curve is needed to be measured, the internal porosity of the irregular columnar structure of the thermal barrier coating can be calculated according to the mass loss of the stable descending section and the volume of the coating sample, the testing and calculating method is simple and convenient, compared with nondestructive testing technologies such as a wave signal method, complex calculating methods such as Fourier transformation and inversion theory are not involved, the complex pore structure has no negative influence on experimental results, and the method is suitable for quantitatively representing the porosity of the irregular columnar structure of the thermal barrier coating with the complex pore structure.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a thermogravimetric curve of example 1 of the present invention reflecting the relationship between the volatilization mass of sodium chloride and the heat treatment time. Wherein 1-1 and 1-2 respectively represent a fast falling section of a thermal weight curve of fast volatilization of sodium chloride due to the surface of a coating sample and a main crystal gap of a columnar structure and a stable falling section of the thermal weight curve of slow volatilization of sodium chloride due to the inside of the columnar structure.
FIG. 2 is a thermogravimetric curve of example 2 of the present invention reflecting the relationship between the volatilization mass of sodium chloride and the heat treatment time. Wherein, 2-1 and 2-2 respectively represent the fast falling section of the thermal weight curve of the fast volatilization of sodium chloride due to the surface of the coating sample and the main crystal gap of the columnar structure and the steady falling section of the thermal weight curve of the slow volatilization of sodium chloride due to the inside of the columnar structure.
FIG. 3 is a thermogravimetric curve of example 3 of the present invention reflecting the relationship between the volatilization mass of sodium chloride and the heat treatment time. Wherein 3-1 and 3-2 respectively represent a fast falling section of a thermal weight curve of fast volatilization of sodium chloride due to the surface of the coating sample and the main crystal gap of the columnar structure and a steady falling section of the thermal weight curve of slow volatilization of sodium chloride due to the inside of the columnar structure.
FIG. 4 shows a cross-sectional scanning electron micrograph of a sample of the permeate coating of example 1 of the present invention after high temperature thawing of the sodium chloride in step 1. Wherein 4-1 is a thermal barrier coating sample, and 4-2 is a sodium chloride layer condensed and accumulated at the bottom of the sample.
FIG. 5 shows a cross-sectional scanning electron micrograph of a sample of the permeate coating of example 2 of the present invention after high temperature thawing of the sodium chloride in step 1. Wherein 5-1 is the residual sodium chloride layer on the upper surface of the sample, and 5-2 is the thermal barrier coating sample.
FIG. 6 shows the cross-sectional scanning electron microscopic morphology and element distribution of a sodium chloride-containing coating sample of comparative example 1 after heat preservation at high temperature for 3 hours.
FIG. 7 is a cross-sectional electron micrograph of a sodium chloride coated thermal barrier coating sample of example 1 of the present invention after heat treatment.
FIG. 8 is a cross-sectional electron micrograph of a sodium chloride-free thermal barrier coating sample of comparative example 2 of the present invention after heat treatment.
Detailed Description
The invention is further described below with reference to the drawings and detailed description. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
All thermal barrier coating samples of examples 1-3 and comparative examples 1-3 were samples prepared in the same batch under the same process (multiple samples could be prepared by one spray coating), the differences between samples were very small, and theoretically the same porosity was found.
Example 1
Analytically pure sodium chloride was added at 60mg/cm 2 Coating the surface of an irregular-structure thermal barrier coating sample prepared by a plasma spraying physical vapor deposition process, placing the thermal barrier coating sample coated with sodium chloride in an alumina ceramic crucible andand (3) placing the sample into a muffle furnace, heating to 850 ℃ at a heating rate of 10 ℃/min, and preserving the heat for 1min to enable sodium chloride to melt and permeate the thermal barrier coating sample under the action of gravity.
And (3) placing the thermal barrier coating sample with the irregular columnar structure permeated by sodium chloride in an alumina ceramic crucible, placing the thermal barrier coating sample in a thermogravimetric analyzer, heating to 850 ℃ at a heating rate of 20 ℃/min, preserving heat for 5 hours, and recording a thermogravimetric curve until the quality of the sample is not changed.
Taking the steady descending section (section 1-2 of the thermal weight curve in fig. 1) of the thermal weight curve, and determining the initial value m of the steady descending section by adopting a linear fitting method i And the final value m e The two are subtracted to obtain the corresponding volatile mass delta m of sodium chloride, and then divided by the density rho of sodium chloride NaCl Obtain the corresponding volatilization volume V of sodium chloride NaCl The method comprises the steps of carrying out a first treatment on the surface of the Adopts the projected area S of the thermal barrier coating sample TBC And thickness h TBC The product of (2) is calculated to obtain the coating volume V TBC Volume of volatile sodium chloride V NaCl Volume of coating V TBC The ratio is the porosity P of the irregular columnar structure of the thermal barrier coating column The specific calculation process is as follows:
V TBC ＝S TBC ·h TBC (equation 2)
Substituting specific numerical values of experimental results into formulas (1) to (3) to obtain the following components:
V TBC ＝8.891mm 2 ×0.4mm＝3.557mm 3
experimental results show that the thermal barrier coating of the embodiment has irregular columnar structure porosity P column 19.483%.
Example 2
This example differs from example 1 in that sodium chloride is added at 60mg/cm in step 1 2 After being coated on the surface of an irregular structure thermal barrier coating sample prepared by a plasma spraying physical vapor deposition process, the thermal barrier coating sample coated with sodium chloride is placed on an alumina crucible with a bracket and placed in a muffle furnace. Other procedures were consistent with example 1.
The steady drop of the thermogravimetric curve of this embodiment is shown as the 2-2 segment of the thermogravimetric curve of fig. 2. Substituting specific numerical values of experimental results into formulas (1) to (3) to obtain the following components:
V TBC ＝7.596mm 2 ×0.4mm＝3.038mm 3
experimental results show that the thermal barrier coating of the embodiment has irregular columnar structure porosity P column 19.322%.
Example 1a thermal barrier coating sample coated with sodium chloride was directly placed in a crucible, and after the sodium chloride melted the penetrating coating sample at high temperature, the coating sample was condensed and deposited at the bottom to form a thicker sodium chloride layer on the lower surface of the coating, as shown in fig. 4; compared with example 1, this example avoids direct contact of the thermal barrier coating sample with the bottom of the crucible by using an alumina crucible support, thereby avoiding sodium chloride condensation accumulation at the bottom of the coating sample, as shown in fig. 5. Because the volatilization rate of sodium chloride in the upper and lower surfaces of the coating sample and the main crystal gaps of the columnar structure is obviously higher than that of sodium chloride in the columnar structure containing multi-orientation dendrite gaps, the residual sodium chloride on the surface of the coating sample of the embodiment is obviously less than that of the coating sampleExample 1, therefore, the fast falling segment of the thermogravimetric curve of this example (segment 2-1 of the thermogravimetric curve of fig. 2) is significantly shorter than example 1 (segment 1-1 of the thermogravimetric curve of fig. 1). In addition, the steady falling section of the thermal weight curve (section 2-2 of the thermal weight curve in FIG. 2) of the embodiment is basically consistent with that of the embodiment 1 (section 1-2 of the thermal weight curve in FIG. 1), and the porosity P of the irregular columnar structure of the thermal barrier coating is calculated in the embodiment column (19.322%) and example 1 calculation result P column The difference (19.483%) is less than 1%, which shows that the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating is insensitive to the sample treatment process, has relatively universal applicability under different sodium chloride coating conditions, and has relatively good repeatability of the porosity measurement result.
Example 3
This example differs from example 1 in that in step 1, the sample of the irregular columnar structure thermal barrier coating coated with sodium chloride is placed in a crucible and heated to 900 ℃ for 1min until the sodium chloride melts. And 2, placing the thermal barrier coating sample with the irregular columnar structure permeated by sodium chloride in an alumina ceramic crucible and placing the alumina ceramic crucible in a thermogravimetric analyzer, heating to 900 ℃ at a heating rate of 20 ℃/min, and preserving heat for 5 hours.
The steady drop of the thermogravimetric curve of this embodiment is as shown in the 3-2 segments of the thermogravimetric curve of fig. 3. Substituting specific numerical values of experimental results into formulas (1) to (3) to obtain the following components:
V TBC ＝13.761mm 2 ×0.4mm＝5.504mm 3
experimental results show that the thermal barrier coating of the embodiment has irregular columnar structure porosity P column 19.295%.
In comparison with example 1, the present example increased the melting temperature of sodium chloride and the thermogravimetric analyzer test temperature from 850 ℃ to 900 ℃. At the temperature of the water at which the water is at a higher temperature,the molten sodium chloride penetrated better and a sample of the coating deposited by condensation of sodium chloride on the bottom was obtained similarly to example 1. However, the gasification rate of sodium chloride is greatly affected by temperature, the temperature rise of the thermogravimetric analysis test is only 50 ℃, the rapid drop section (3-1 section of the thermogravimetric curve in fig. 3) and the steady drop section (3-2 section of the thermogravimetric curve in fig. 3) of the embodiment are both significantly shorter than those of the embodiment 1, the time required for complete gasification is only about 1h, and if the test temperature is continuously increased, too much sodium chloride is gasified in the heating process, resulting in insufficient sodium chloride content in the coating sample and affecting the experimental result. The thermal barrier coating obtained by calculation in the embodiment has irregular columnar structure porosity P column (19.295%) and example 1 calculation result P column The difference (19.483%) is also less than 1%, which shows that the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating provided by the invention has more general applicability in a certain test temperature range of a thermogravimetric analyzer, and the porosity measurement result is proved to have better repeatability.
Comparative example 1
The comparative example differs from example 1 in that in step 2, a sample of the irregular columnar structure thermal barrier coating infiltrated with sodium chloride was placed in an alumina ceramic crucible and placed in a thermogravimetric analyzer, heated to 850 ℃ at a heating rate of 20 ℃/min and incubated for 2 hours.
Compared with example 1, the comparative example shortens the heat preservation time from 5h to 2h, and the thermal weight curve of FIG. 1 shows that the sample is in the middle of the smooth descending section (1-2 sections) at this time, and sodium chloride in the sample is not completely volatilized yet. The section morphology and element distribution of the coating sample are obtained by adopting a scanning electron microscope and an energy spectrum analyzer (figure 6), and the fact that sodium chloride does not exist on the upper surface and the lower surface of the coating can be clearly seen, so that the fact that the sodium chloride on the upper surface and the lower surface of the coating sample volatilizes in a rapid descending section (1-1 section) of a thermogravimetric curve is shown; the sodium chloride (NaCl) still exists in the columnar structure, which shows that the steady descending section (1-2 sections) of the thermogravimetric curve truly reflects the volatilization process of the sodium chloride in the columnar structure.
Comparative example 2
The comparative example differs from example 1 in that the surface of the irregular structure thermal barrier coating sample prepared by the plasma spray physical vapor deposition process is not coated with sodium chloride. Other procedures were consistent with example 1.
As shown in fig. 7, after the porosity of the thermal barrier coating sample coated with sodium chloride in example 1 is measured according to the method of the present invention, although the thermal barrier coating sample is subjected to heat treatment at 850 ℃ for 5 hours, the thermal barrier coating sample still maintains a feather-like irregular columnar structure due to the fact that the thermal barrier coating sample is far lower than the sintering and phase transition temperature of the zirconia ceramic material, and structural characteristics such as micron primary crystals, nano dendrites, primary crystal gaps, nano dendrite gaps and the like are not changed, and sodium chloride residues do not exist in the section; as shown in FIG. 8, after the thermal barrier coating sample without sodium chloride coating in the comparative example is subjected to heat treatment according to the method disclosed by the invention, the feather-like irregular columnar structure is complete, and the structural characteristics of micron primary crystals, nano dendrites, primary crystal gaps, nano dendrite gaps and the like are consistent with those of the embodiment 1, so that the thermal barrier coating irregular columnar structure porosity measurement method disclosed by the invention does not damage or destroy the thermal barrier coating sample, and is a nondestructive detection method.
Comparative example 3
The comparative example differs from examples 1 and 2 in that the porosity of the thermal barrier coating with the irregular columnar structure is characterized by adopting a metallographic method. Taking a denser area of a columnar structure of the coating at the lower part of the cross section, avoiding a main crystal gap of the columnar structure with a wider upper part, and counting by using an image method to obtain the porosity of the coating, wherein the porosity is shown in a table 1.
The comparative example calculates the porosity of a denser area of a columnar structure of a coating at the lower part in a section, comprises dendrite gaps of the columnar structure and a small amount of main crystal gaps, avoids the main crystal gaps of the columnar structure with wider upper part, and can reflect the internal porosity level of the columnar structure to a certain extent. The porosity level (21%) obtained by metallographic statistics is similar to the measurement results (19%) of the embodiments 1 and 2 of the invention, which shows that the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating provided by the invention has correctness and feasibility; because the metallographic method is difficult to completely avoid the main crystal gap, the metallographic method statistical result is slightly higher than the results of the examples 1 and 2, which shows that the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating can accurately measure the internal porosity of the irregular columnar structure.
Table 1 thermal barrier coating porosity of irregular columnar structure characterized by metallographic method
In conclusion, the method for measuring the porosity of the irregular columnar structure of the thermal barrier coating is simple, convenient and feasible, insensitive to sample treatment process, relatively universal in applicability and relatively good in repeatability, capable of measuring the internal porosity of the irregular columnar structure relatively accurately, free of damage or destruction to a coating sample, suitable for quantitatively representing the porosity of the irregular columnar structure thermal barrier coating with a complex pore structure, and significant in evaluating and predicting the thermal insulation and corrosion resistance of the irregular columnar structure thermal barrier coating represented by the plasma spraying physical vapor deposition feather-like columnar structure.
The above examples are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above examples, and any other changes, modifications, substitutions, combinations, and simplifications that do not depart from the spirit and principle of the present invention should be made in the equivalent manner, and the embodiments are included in the protection scope of the present invention.
Claims (9)
1. The method is characterized in that the method utilizes different volatilization characteristics of sodium chloride on the surface of the coating and in the pores, and quantitatively characterizes the internal porosity of the irregular columnar structure through thermogravimetric experiments.
2. The method according to claim 1, characterized in that it comprises the steps of:
step 1: coating sodium chloride on the surface of the thermal barrier coating sample with the irregular columnar structure, and placing the sample in a crucible to heat until the sodium chloride melts, so that molten sodium chloride permeates the thermal barrier coating sample;
step 2: placing the thermal barrier coating sample with the irregular columnar structure permeated by sodium chloride into a thermogravimetric analyzer, heating to a temperature above the melting point of sodium chloride, and preserving heat until the quality of the sample is not changed;
step 3: and (3) taking a steady descending section of the thermal weight curve, and calculating the corresponding volatilization mass and volume of sodium chloride, wherein the ratio of the volume of the volatilized sodium chloride to the volume of the coating is the porosity of the irregular columnar structure of the thermal barrier coating.
3. The method according to claim 2, wherein the coating amount of sodium chloride of the thermal barrier coating sample with the irregular columnar structure in the step 1 is more than or equal to 60mg/cm 2 。
4. The method according to claim 2, wherein the heating temperature in step 1 is 850-900 ℃, the heating rate is 5-15 ℃/min, and the holding time is 1-10min.
5. The method of claim 2, wherein the crucible in step 1 is an alumina ceramic crucible.
6. The method of claim 2, wherein the thermogravimetric analyzer in step 2 employs an alumina ceramic crucible.
7. The method according to claim 2, wherein the heating temperature in step 2 is 850-900 ℃, the heating rate is 10-20 ℃/min, and the holding time is 5h.
8. The method of claim 2, wherein the initial and final values of the steady-down segment of the thermogravimetric curve are determined in step 3 using a linear fitting method.
9. The method of claim 2, wherein the coating volume in step 3 is calculated using the product of projected area and thickness of the coating.
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| CN117723594A (en) * | 2024-02-09 | 2024-03-19 | 深圳大学 | Detection method of heat-preserving building component based on MIV-BP model |
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