Method for predicting service life of coating by taking temperature as accelerated stress

Abstract

The invention belongs to the technical field of coating life prediction, and particularly relates to a method for predicting coating life by taking temperature as accelerated stress, which comprises the following steps: testing the original coating bonding strength and series attenuation coating bonding strength of a composite coating sample to obtain a strength-time attenuation model; according to the strength-time attenuation model, the time when the bonding strength of the original coating is attenuated to the failure strength of the coating is obtained by taking the bonding strength of the coating in failure as the predicted life in different humid and hot environments; according to the predicted life and the corresponding temperature in different humid and hot environments, the numerical values of E and A in the formula I are solved, and then the predicted life of the coating is obtained according to the formula I of the known numerical values of E and A and the temperature of the actual storage environment. The prediction method provided by the invention can solve the problems of long prediction period and poor accuracy of the service life of the coating in the prior art, can quantitatively predict the service life of the coating in a short time, and can be suitable for any temperature environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of coating life prediction, and in particular relates to a method for predicting coating life by using temperature as an accelerating stress. Background Art

[0002] Hypersonic vehicles, with their advantages of high flight speed and strong penetration capability, are the focus of development by major military powers. However, during service, aircraft are subject to severe aerodynamic heating, and a high-emissivity composite coating is required on the outside of the metal substrate to conduct heat and protect the launch shape of the aircraft. During the storage of coating materials, whether the performance of high-emissivity composite coatings degrades is a key concern in the engineering field. Currently, storage in natural environments is often used to verify the storage life of coatings, but there are problems such as long life prediction cycles, which cannot meet the needs of rapid iteration and short R&D cycles of aircraft. This has become an urgent problem to be solved. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for predicting the coating life. The life prediction method provided by the present invention can solve the problems of long coating life prediction period and poor accuracy in the prior art. It can quantitatively predict the coating life in a relatively short time and is applicable to any temperature environment.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The present invention provides a method for predicting coating life by using temperature as an accelerating stress, comprising the following steps:

[0006] Test the original coating bonding strength of composite coating specimens;

[0007] The composite coating samples were placed in different hot and humid environments for hot and humid tests, and the series of attenuated coating bonding strengths of the composite coating samples at different time points under different hot and humid environments were tested.

[0008] According to the original coating bonding strength, the series of attenuated coating bonding strength and the time of corresponding attenuated coating bonding strength, the strength-time attenuation model under different humid and hot environments was obtained;

[0009] Based on the strength-time decay model under different humid and hot environments and the coating bonding strength at the time of coating failure under different humid and hot environments, the time for the original coating bonding strength to decay to the coating bonding strength at the time of coating failure is obtained as the predicted life under different humid and hot environments;

[0010] Based on the predicted lifespan under different hot and humid environments, the corresponding temperature, and Formula I, the least squares method is used to solve E and A. Then, based on Formula I with known E and A values ​​and the average temperature of the actual storage environment, the predicted lifespan of the coating is obtained.

[0011] lnε=E / kT+lnA Formula I;

[0012] In formula I: ε is the predicted lifespan;

[0013] A is a constant and A>0;

[0014] E is the activation energy, in eV;

[0015] k is 8.167×10 -5 eV / ℃;

[0016] T is the absolute temperature, unit is K.

[0017] Preferably, the composite coating sample includes a substrate, a metal bonding layer located on the surface of the substrate, and a ceramic coating located on the surface of the metal bonding layer.

[0018] Preferably, the ceramic coating is a perovskite coating.

[0019] Preferably, the ceramic coating is La 1-x A x Cr 1-y M y O3; A is one or more of Ca and Sr, M is one or more of Mg, Co and Mn, 0.05≤x≤0.3, 0.05≤y≤0.3, and the thickness of the ceramic coating is 0.04mm~0.3mm.

[0020] Preferably, the substrate is an alloy substrate.

[0021] Preferably, the metal bonding layer is a NiCrCoAlY coating.

[0022] Preferably, the metal bonding layer and the ceramic coating are obtained by atmospheric plasma spraying.

[0023] Preferably, the series of attenuation coating bond strength tests are for coating bond strength of 5 days, 10 days, 15 days, 20 days and 25 days of damp heat tests.

[0024] Preferably, the strength-time decay model is obtained by linear fitting with the decay coating bonding strength as the ordinate and the time of the wet heat test as the abscissa.

[0025] The life prediction method provided by the present invention utilizes Formula I (Arrhenius model) to establish a life prediction model, uses temperature as the accelerating stress, and extrapolates the experimental data to other environments, thereby quantitatively predicting the life cycle of the coating. The environmental tolerance data of the coating that would take several years to obtain using traditional methods can be completed in a few months, reducing the time and economic costs of the assessment. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0027] Figure 1 These are the model curves fitted under three different hot and humid environments in Example 1. DETAILED DESCRIPTION

[0028] The present invention provides a method for predicting coating life by using temperature as an accelerating stress, characterized by comprising the following steps:

[0029] Test the original coating bonding strength of composite coating specimens;

[0030] The composite coating samples were placed in different hot and humid environments for hot and humid tests, and the series of attenuated coating bonding strengths of the composite coating samples at different time points under different hot and humid environments were tested.

[0031] According to the original coating bonding strength, the series of attenuated coating bonding strength and the time of corresponding attenuated coating bonding strength, the strength-time attenuation model under different humid and hot environments was obtained;

[0032] Based on the strength-time decay model under different humid and hot environments and the coating bonding strength at the time of coating failure under different humid and hot environments, the time for the original coating bonding strength to decay to the coating bonding strength at the time of coating failure is obtained as the predicted life under different humid and hot environments;

[0033] Based on the predicted lifespan under different hot and humid environments, the corresponding temperature, and Formula I, the least squares method is used to solve E and A. Then, based on Formula I with known E and A values ​​and the average temperature of the actual storage environment, the predicted lifespan of the coating is obtained.

[0034] lnε=E / kT+lnA Formula I;

[0035] In formula I: ε is the predicted lifespan;

[0036] A is a constant and A>0;

[0037] E is the activation energy, in eV;

[0038] k is 8.167×10 -5 eV / ℃;

[0039] T is the absolute temperature, unit is K.

[0040] The composite coating specimens were tested for their original coating bonding strength.

[0041] As an embodiment of the present invention, the composite coating sample preferably includes a substrate, a metal bonding layer located on the surface of the substrate, and a ceramic coating located on the surface of the metal bonding layer.

[0042] As an embodiment of the present invention, the substrate is preferably an alloy substrate; the alloy substrate is preferably a titanium alloy substrate. As an embodiment of the present invention, the metal bonding layer is preferably a NiCrCoAlY coating. As an embodiment of the present invention, the ceramic coating is preferably a perovskite coating; the ceramic coating can be specifically La 1- x A x Cr 1-y M y O3; A is one or more of Ca and Sr, M is one or more of Mg, Co and Mn, 0.05≤x≤0.3, 0.05≤y≤0.3, and the thickness of the ceramic coating is preferably 0.04mm~0.3mm.

[0043] As an embodiment of the present invention, the metal bonding layer and the ceramic coating are obtained by atmospheric plasma spraying. As an embodiment of the present invention, the preparation of the composite coating sample can be specifically prepared by referring to CN111876719 A.

[0044] The present invention places the composite coating samples in different wet and hot environments for wet and hot tests, and tests the series of attenuated coating bonding strengths of the composite coating samples at different time points under different warm and hot environments; based on the original coating bonding strength, the series of attenuated coating bonding strengths and the time of the corresponding attenuated coating bonding strength, the strength-time attenuation model under different wet and hot environments is obtained.

[0045] As an embodiment of the present invention, the series of attenuating coating bond strengths preferably tests the coating bond strengths of 5-day, 10-day, 15-day, 20-day, and 25-day damp heat tests. As an embodiment of the present invention, the test results are preferably averaged after removing outliers to obtain the series of attenuating coating bond strengths.

[0046] As an embodiment of the present invention, the strength-time decay model is preferably obtained by linear fitting with the decay coating bonding strength as the ordinate and the time of the wet heat test as the abscissa.

[0047] The present invention obtains the strength-time decay model under different humid and hot environments and the coating bonding strength when the coating is effective under different humid and hot environments, and obtains the time when the original coating bonding strength decays to the coating bonding strength when the coating fails, as the predicted life under different humid and hot environments; according to the predicted life under different humid and hot environments, the corresponding temperature and Formula I, E and A are solved according to the least squares method, and then the predicted life of the coating is obtained according to Formula I with known E and A values ​​and the average temperature of the actual storage environment.

[0048] lnε=B / kT+lnA-ClnRH Formula I;

[0049] In formula I: ε is the predicted lifespan;

[0050] A, B, C are constants and A, B, C>0;

[0051] k is 8.167×10 -5 eV / ℃;

[0052] T is absolute temperature, unit K;

[0053] RH is relative humidity, unit is %.

[0054] In the present invention, the coating bonding strength when the coating fails can be specified according to different coatings or different usage scenarios as required. In the embodiment of the present invention, 5 MPa is specifically used as an example for illustration.

[0055] In order to further illustrate the present invention, the scheme of the present invention is described in detail below with reference to the accompanying drawings and embodiments, but they should not be understood as limiting the scope of protection of the present invention.

[0056] Example 1

[0057] La2O3, CaO, Cr2O3, and MnO2 powders are mixed with a binder and water, and ball milled to obtain a ball mill slurry; the ball mill slurry is spray dried to obtain agglomerated powder; the agglomerated powder is subjected to induction plasma spheroidization treatment to obtain La 0.7 Mg 0.3 Cr 0.7 Mn 0.3 O3 composite powder.

[0058] The surface of the clean substrate (made of TA15) to be sprayed is roughened to a roughness of 5 μm; the substrate to be sprayed is preheated to a temperature of 100°C;

[0059] The bonding layer material NiCrCoAlY powder is loaded into the powder feeder, and the bonding layer is sprayed on the surface of the substrate to be sprayed by atmospheric plasma spraying method; the prepared La 0.7Mg 0.3 Cr 0.7 Mn 0.3 The composite powder of O3 ceramic layer material is loaded into the powder feeder and sprayed on the substrate on which the bonding layer has been sprayed by atmospheric plasma spraying method to obtain a perovskite type high emissivity coating (i.e. La 0.7 Mg 0.3 Cr 0.7 Mn 0.3 O3 / metal bonding layer / TA15 substrate composite coating sample). Specific parameters are: main gas argon flow rate of 90SCFH, auxiliary gas helium flow rate of 8SCFH, carrier gas argon flow rate of 8SCFH, current of 600A, spraying distance of 85mm, and powder feeding rate of 2RPM.

[0060] The coating bonding strength data of the five original samples were measured as follows: 40.46MPa, 43.95MPa, 39.51MPa, 45.90MPa, and 38.08MPa, with an average of 41.58MPa.

[0061] In addition, 15 samples were divided into three groups, with 5 samples in each group, and placed in three different temperature and humidity environments, namely (1) 85℃, 85% RH; (2) 70℃, 85% RH; and (3) 55℃, 85% RH in a heat and humidity test chamber.

[0062] Three samples were taken from each experimental group for bonding strength test at 5 days, 10 days, 15 days, 20 days, and 25 days. After removing outliers, the average bonding strength was calculated, as shown in Table 1:

[0063] Table 1 Test results of binding strength of each group of experiments at 5 days, 10 days, 15 days, 20 days and 25 days

[0064]

[0065] Fitting the data under different environments, the fitting functions are:

[0066] (1) 85°C, 85% RH: y = 40.36 × exp(-x / 22.44) (y is in MPa, x is in days)

[0067] (2) 70°C, 85% RH: y = 41.42 × exp(-x / 56.79) (y is in MPa, x is in days)

[0068] (3) 55°C, 85% RH: y = 41.67 × exp(-x / 83.70) (y is in MPa, x is in days)

[0069] The predicted lifespan under different humid and hot environments is calculated based on the fitting function. When the bonding strength drops to 5 MPa:

[0070] 85°C, 85% RH: predicted lifespan is 46.9 days;

[0071] 70°C, 85% RH: predicted lifespan is 120.1 days;

[0072] 55°C, 85% RH: predicted lifespan is 177.5 days;

[0073] According to lnε=E / kT+lnA, the lifespans and corresponding temperatures of the three groups of samples were substituted into the formula for fitting, and lnε=4231.86 / T-7.81 was obtained.

[0074] The composite coating is stored in an environment with a temperature of 20°C (T = 293.15K) and a humidity of 85% RH, and has a lifespan of approximately 754 days. Because 85% RH is higher than the humidity of conventional storage, the actual lifespan should be longer than 754 days.

[0075] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A method for predicting coating life using temperature as an accelerating stress, characterized in that: The following steps are involved: Test the original coating bonding strength of composite coating specimens; The composite coating samples were placed in different hot and humid environments for hot and humid tests, and the series of attenuated coating bonding strengths of the composite coating samples at different time points under different hot and humid environments were tested. According to the original coating bonding strength, the series of attenuated coating bonding strength and the time of corresponding attenuated coating bonding strength, the strength-time attenuation model under different humid and hot environments was obtained; Based on the strength-time decay model under different humid and hot environments and the coating bonding strength at the time of coating failure under different humid and hot environments, the time for the original coating bonding strength to decay to the coating bonding strength at the time of coating failure is obtained as the predicted life under different humid and hot environments; Based on the predicted lifespan under different hot and humid environments, the corresponding temperature, and Formula I, the least squares method is used to solve E and A. Then, based on Formula I with known E and A values ​​and the average temperature of the actual storage environment, the predicted lifespan of the coating is obtained. lnε=E / kT+lnA Formula I; In formula I: ε is the predicted lifespan; A is a constant and A>0; E is the activation energy, in eV; k is 8.167×10 -5 eV / ℃; T is the absolute temperature, unit is K.

2. The method according to claim 1, wherein The composite coating sample comprises a substrate, a metal bonding layer located on the surface of the substrate, and a ceramic coating located on the surface of the metal bonding layer.

3. The method according to claim 2, wherein The ceramic coating is a perovskite coating.

4. The method according to claim 3, wherein The ceramic coating is La 1-x A x Cr 1-y M y O3; A is one or more of Ca and Sr, M is one or more of Mg, Co and Mn, 0.05≤x≤0.3, 0.05≤y≤0.3, and the thickness of the ceramic coating is 0.04mm~0.3mm.

5. The prediction method according to claim 2, wherein: The matrix is ​​an alloy matrix.

6. The method according to claim 2, wherein The metal bonding layer is a NiCrCoAlY coating.

7. The method according to claim 1, wherein The metal bonding layer and the ceramic coating are obtained by atmospheric plasma spraying.

8. The method according to claim 1, wherein The series of attenuated coating bond strength tests measured the coating bond strength of 5-day, 10-day, 15-day, 20-day, and 25-day damp heat tests.

9. The method according to claim 1, wherein The strength-time decay model is obtained by linear fitting with the decay coating bonding strength as the ordinate and the time of the wet heat test as the abscissa.

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