Calculation method of Al-Ni mutual diffusion coefficient in aluminized coating

Abstract

The invention provides a method for calculating an Al-Ni mutual diffusion coefficient in an aluminizing coating, and relates to the technical field of protective coatings, and the method comprises the following steps: S1, selecting an aluminizing agent proportion to carry out aluminizing treatment on a nickel-based high-temperature alloy; s2, the sample obtained after aluminizing treatment is ground and polished, the structure morphology of the sample is observed through SEM, and Al element distribution is analyzed through EDS line scanning and point scanning; s3, scanning is conducted in the thickness direction of the aluminizing layer, ten data points are taken at equal intervals, the Al concentration is measured, the average value of data of three points on the two sides of each point is taken as the data of each point, and fitting constants of the formula of the aluminizing agent selected in S1 are obtained after fitting; s4, substituting the fitting constant obtained in the step S3 into a Ni / Al mutual diffusion coefficient expression to obtain a diffusion coefficient; s5, for different aluminizing agent proportions, the diffusion coefficient of each proportion is calculated according to the steps S3-S4; and S6, determining that the phase composition of the aluminide infiltrated layer depends on the mutual diffusion speed of aluminum and nickel atoms.

Description

Technical Field

[0001] The present invention relates to the technical field of protective coatings, and specifically relates to a method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating. Background Art

[0002] After aluminizing the surface of DD5 nickel-based superalloy, when aluminum diffuses into the nickel-based superalloy matrix, due to the compositional change, phase reactions occur simultaneously in the diffusion zone, that is, reaction diffusion occurs. While aluminum atoms diffuse into the nickel-based superalloy matrix, iron atoms also diffuse into the aluminum layer, jointly forming interdiffusion, and finally Ni-Al intermetallic compounds will be formed in the aluminized layer. The Ni-Al compound is an intermetallic compound with good oxidation resistance and is often used as the matrix of aluminide coatings. Due to the diffusion process, the concentrations of Al and Ni elements in the aluminide layer change with time, and this diffusion process conforms to Fick's second law. Research shows that the interdiffusion coefficient of elements in the Ni-Al phase can be solved by using the distribution curve of Al atom concentration. Although the finite difference method is widely used, it is difficult to obtain the continuity of Al atom concentration over time and the error of the experiment itself when obtaining experimental data, making the calculation results related to the experimental process. Usually, the information obtained in the experiment is mainly the distribution curve of Al atom concentration under certain experimental conditions, and it is very difficult to randomly obtain the distribution information of Al atoms during the formation of the aluminized coating. Summary of the Invention

[0003] Technical Problem to be Solved

[0004] In view of the deficiencies of the prior art, the present invention provides a method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating, which solves the technical problems existing in the prior art.

[0005] Technical Solution

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating, comprising the following steps:

[0007] S1, select the aluminizing agent ratio to perform aluminizing treatment on the nickel-based superalloy;

[0008] S2, polish the aluminized sample, observe its microstructure by SEM, and analyze the Al element distribution by EDS line scanning and point scanning;

[0009] S3, scan along the thickness direction of the aluminized layer, equally spacedly take ten data points, measure the Al concentration, and take the average value of a total of 3 points on both sides of each point's data. After fitting, obtain the fitting constant of the aluminizing agent formula selected in S1;

[0010] S4. Substitute the fitting constants obtained in S3 into the expression of the interdiffusion coefficient between Ni and Al to obtain the diffusion coefficient.

[0011] S5. For different aluminizing agent ratios, calculate the diffusion coefficient of each ratio respectively according to the above steps S3 - S4.

[0012] S6. The phase composition of the aluminide layer depends on the interdiffusion rate of Al and Ni atoms.

[0013] Preferably, in step S2, the error of the Al concentration measurement value at 3 points is less than 0.25%, and a set of Al concentration data points is obtained. Plot these points in origin and fit them through the Boltzmann function to obtain a fitting graph, where the fitting formula is:

[0014]

[0015] In the formula, C is the Al concentration value, with the unit of wt.%; x is the distance of each data point from the surface, with the unit of: μm, and A, B, E, F are fitting constants, and the fitting constants of the aluminizing agent ratio are obtained through fitting.

[0016] Preferably, the expression of the interdiffusion coefficient between Ni and Al in S4 is as follows:

[0017]

[0018] The diffusion coefficient is obtained through auxiliary calculation by Matlab, where D(C) is the diffusion coefficient, A, B, E, F are fitting constants, C is the Al concentration value, and t is the diffusion time.

[0019] Preferably, in step S6, when the diffusion coefficient is higher than 9×10 - 13·m2·s - 1, the compound formed in the Ni - Al alloy layer is mainly the β - NiAl rich - Al phase.

[0020] Preferably, in step S6, when the diffusion coefficient is between 4×10 - 13·m2·s - 1 and 9×10 - 13·m2·s - 1, the compounds formed in the Ni - Al alloy layer are mainly the δ - Ni2Al3 and β - NiAl phases.

[0021] Preferably, in step S6, when the diffusion coefficient is lower than 4×10 - 13·m2·s - 1, the compound formed in the Ni - Al alloy layer is mainly the Al3Ni phase.

[0022] Beneficial effects

[0023] The present invention provides a calculation method for the Al - Ni interdiffusion coefficient in an aluminized coating. It has the following

[0024] Beneficial effects:

[0025] By establishing the relationship between the diffusion coefficient and the Ni-Al phase, the present invention can accurately predict the phases formed under different aluminizing agent ratios. This enables pre-judgment before experiments, effectively reducing unnecessary experimental processes, saving time and costs. Through the analysis of the diffusion coefficient, a theoretical basis can be provided for the optimization of the aluminizing process. According to different diffusion coefficient values, the ratio of the aluminizing agent and the aluminizing time can be adjusted to control the formed Ni-Al phase, thereby improving the performance of the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the cross-sectional morphology diagram of the holding time of 10Al5.

[0027] Figure 2 It is the XRD spectrum diagram of the holding time of 10Al5.

[0028] Figure 3 It is the cross-sectional morphology diagram of the holding time of 10Al2.5.

[0029] Figure 4 It is the XRD spectrum diagram of the holding time of 10Al2.5.

[0030] Figure 5 It is the cross-sectional morphology diagram of the holding time of 5Al5.

[0031] Figure 6 It is the XRD spectrum diagram of the holding time of 5Al5.

[0032] Figure 7 It is the Al element concentration distribution of aluminizing agents with different ratios.

[0033] Figure 8 It is the Al / Ni interdiffusion coefficient of aluminizing agents with different ratios. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] The substrate composition in the embodiment satisfies the following conditions: Four different aluminizing agent ratios are selected to perform aluminizing treatment on the DD5 nickel-based superalloy.

[0036] Aluminizing agent ratio table:

[0037]

[0038] Sample preparation: The experiment used a nickel-based single crystal high-temperature alloy sample with a size of 7mm×7mm×1mm. The sample surface was polished with 240-mesh and 400-mesh sandpaper, and then the sample was placed in a solution of 1:1 alcohol and acetone for ultrasonic cleaning for 10 minutes, and then its surface was cleaned with pure water, and then the sample was placed in a hydrochloric acid solution with a mass concentration of 10% and immersed for 1 minute, and its surface was also cleaned with pure water for standby use as a matrix. The sample was then placed in a crucible containing different ratios of Al, catalyst NH4Cl, and inert filler Al2O3 (the specific ratio is shown in the aluminizing agent ratio table), and the aluminizing process was carried out in a muffle furnace at 1050°C for 0.5, 1, and 1.5 hours. Specific embodiment one:

[0040] like Figure 1 , 2 As shown, a method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating comprises the following steps:

[0041] S1, selecting an aluminizing agent ratio to perform aluminizing treatment on the nickel-based high-temperature alloy;

[0042] S2, the samples after aluminizing treatment were polished, the microstructure was observed by SEM, and the Al element distribution was analyzed by EDS line scanning and point scanning;

[0043] S3, scan along the thickness direction of the diffusion layer, and take ten data points at equal intervals to measure the Al concentration, and take the average value of the data of the three points on both sides of each point, and obtain the fitting constant of the aluminizing agent formula selected in S1 after fitting;

[0044] S4, substituting the fitting constant obtained in S3 into the expression of the interdiffusion coefficient between Ni and Al to obtain the diffusion coefficient;

[0045] S5, for different aluminizing agent ratios, respectively calculate the diffusion coefficient of each ratio according to the above steps S3 to S4;

[0046] S6, the phase composition of the aluminide layer depends on the interdiffusion rate of aluminum and nickel atoms.

[0047] The error of the Al concentration measurement values ​​at the three points in step S2 is less than 0.25%, and a set of Al concentration data points are obtained. These points are plotted in origin and fitted by the Boltzmann function to obtain a fitting graph, where the fitting formula is:

[0048]

[0049] Where C is the Al concentration value in wt.%, x is the distance of each data point from the surface in μm, and A, B, E, and F are fitting constants obtained by fitting the aluminizing agent ratio. The expression for the Ni / Al interdiffusion coefficient in S4 is as follows:

[0050]

[0051] The diffusion coefficient is obtained through auxiliary calculation by Matlab. Here, D(C) is the diffusion coefficient, A, B, E, and F are fitting constants, C is the Al concentration value, and t is the diffusion time.

[0052] In step S6, when the diffusion coefficient is higher than 9×10-13·m2·s-1, the compound formed in the Ni-Al alloy layer is mainly the β-NiAl aluminum-rich phase.

[0053] In step S6, when the diffusion coefficient is between 4×10-13·m2·s-1 and 9×10-13·m2·s-1, the compounds formed in the Ni-Al alloy layer are mainly δ-Ni2Al3 and β-NiAl phases.

[0054] In step S6, when the diffusion coefficient is lower than 4×10-13·m2·s-1, the compound formed in the Ni-Al alloy layer is mainly the Al3Ni phase.

[0055] After heat treatment, the aluminizing agent with a composition of 10wt.% Al 5wt.% NH4Cl (hereinafter referred to as 10Al5) can be identified by XRD to have two different layers. The outer layer is the β-NiAl layer, which contains strip-shaped precipitates rich in matrix elements such as Cr, Ta, and Co. The middle layer is the β-NiAl layer without precipitates. After heat treatment, the aluminizing agent with a composition of 10wt.% Al 2.5wt.% NH4Cl (hereinafter referred to as 10Al2.5) can be identified by XRD to have two different layers. The outer layer is the Al3Ni layer, which contains strip-shaped precipitates rich in matrix elements such as Cr, Ta, and Co. The middle layer is the δ-Ni2Al3 layer without precipitates. After heat treatment, the aluminizing agent with a composition of 5wt.% Al 5wt.% NH4Cl (hereinafter referred to as 5Al5) can be identified by XRD to have three different layers. The outer layer is the δ-Ni2Al3 layer, with pores and precipitates throughout the outer layer. Below it is the β-NiAl layer without precipitates, and finally, there is a thin IDZ layer rich in refractory elements such as Cr, W, and Co. After heat treatment, the aluminizing agent with a composition of 5wt.% Al 2.5wt.% NH4Cl (hereinafter referred to as 5Al2.5) can be identified by XRD and EDS to have two different layers. The outermost layer is a thin layer of Al, and below it are precipitates of various refractory elements.

[0056] Keep 10Al5 at a constant temperature for 0.5 h, 1 h, and 1.5 h:

[0057] Embed samples with different holding times (10 wt.% Al, 5 wt.% NH4Cl, 85 wt.% Al2O3) using embedding materials. Characterize the microstructure morphology of the specimen surface using a scanning electron microscope (SEM), and determine the infiltration layer thickness by observing its cross-section (as Figure 1 shown), and analyze the phase composition of the samples using an X-ray diffractometer (XRD) and an energy dispersive spectrometer (EDS) (as Figure 2 shown).

[0058] The infiltration layer thicknesses of the 10Al5 formulation are 177 μm, 218 μm, and 269 μm respectively, and the phase composition is always the β-NiAl phase. Analyze the sample with a holding time of 1 h. Perform a line scan along the infiltration layer thickness direction, take ten data points at equal intervals, and take the average of three points of the Al concentration at one depth. The test error is less than 0.25%. Is it that if the test error between the next value and the previously taken value is ≥0.25% after taking one value, the next value is not taken? No, ten points are taken along the coating thickness direction and two more points are taken above and below each point; what if the first value taken is inaccurate? Because each point is the average of three points and the experimental instrument has a high precision, it is relatively accurate. Obtain a set of Al atomic concentration data points. Plot these points in Origin and fit them through the Boltzmann function to obtain a fitting graph (as Figure 7 shown in a), and the fitting constants are as shown in the table:

[0059] Fitting constants for the Al atomic concentration distribution curve of 10Al5:

[0060]

[0061]

[0062] Substitute the fitting constants into Equation 2 and use Matlab for auxiliary calculation to obtain the diffusion coefficient as Figure 8 shown in a). Specific Example 2:

[0064] Based on the technical solution of Specific Example 1, further explanation:

[0065] A calculation method for the Al-Ni interdiffusion coefficient in an aluminized coating. Treat 10Al2.5 at a constant temperature for 0.5 h, 1 h, and 1.5 h. Embed samples with different holding times (10 wt.% Al, 2.5 wt.% NH4Cl, 87.5 wt.% Al2O3) using embedding materials. Characterize the microstructure morphology of the specimen surface using a scanning electron microscope (SEM), and determine the infiltration layer thickness by observing its cross-section (as Figure 3As shown in the figure, the phase composition of the sample was analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS) (such as Figure 4 shown).

[0066] The thicknesses of the aluminized layers with 10Al2.5 ratio were 126μm, 153μm, and 208μm respectively. The phase composition changed from a single Al3Ni phase at the beginning to an Al3Ni phase on the outside and a δ-Ni2Al3 phase on the inside. Line scans were performed along the thickness direction of the aluminized layer, and ten data points were taken at equal intervals. At a certain depth, the average value of the Al concentration at 3 points was taken, and the test error was less than 0.25%. A set of Al atomic concentration data points was obtained. These points were plotted in Origin and fitted through the Boltzmann function to obtain a fitting graph (such as Figure 7 shown in Figure b), and the fitting constants are shown in the table:

[0067] Fitting constants of the Al atomic concentration distribution curve at 1050℃ and 10A2.l5:

[0068]

[0069] Substitute the fitting constants into Equation 2, and use Matlab for auxiliary calculation to obtain the diffusion coefficient as shown in Figure 8 Figure b. Specific Example 3:

[0071] Based on the technical solution of Specific Example 1, further explanation:

[0072] A method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating. For 5Al5, 0.5h, 1h, 1.5h

[0073] Samples with different holding times (5wt.% Al, 5wt.% NH4Cl, 90wt.% Al2O3) were inlaid with inlay materials, and the microstructure morphology of the specimen surface was characterized by scanning electron microscopy (SEM), and the thickness of the aluminized layer was determined by observing its cross-section (such as Figure 5 shown), and the phase composition of the sample was analyzed by X-ray diffractometer (XRD) and energy dispersive spectrometer (EDS) (such as Figure 6 shown).

[0074] The thicknesses of the aluminized layers with 5Al5 ratio were 38μm, 70μm, and 87μm respectively. For 5Al5, the phase composition was always the δ-Ni2Al3 phase. Line scans were performed along the thickness direction of the aluminized layer, and ten data points were taken at equal intervals. At a certain depth, the average value of the Al concentration at 3 points was taken, and the test error was less than 0.25%. A set of Al atomic concentration data points was obtained. These points were plotted in Origin and fitted through the Boltzmann function to obtain a fitting graph (such as Figure 7 shown in Figure c), and the fitting constants are shown in the table:

[0075] Fitting constants of the Al atomic concentration distribution curve at 1050℃, 10A, and 2.15 h

[0076]

[0077] Substitute the fitting constants into Equation 2 and use Matlab for auxiliary calculation to obtain the diffusion coefficient as shown in Figure 8 c:

[0078] From Figure 8 it can be seen that when the temperature remains constant, the interdiffusion coefficient increases with the increase of Al atomic concentration and catalyst concentration. The change of the former is more significant than that of the latter. The interdiffusion coefficient of the 10Al5 system is above 9×10-13·m2·s-1, and the formed phase is β-NiAl; the interdiffusion coefficient of the 10Al2.5 system is lower than 3.7×10-13·m2·s-1, and the formed phase is Al3Ni; the interdiffusion coefficient of the 5Al5 system is between 4.37×10-13·m2·s-1 and 4.53×10-13·m2·s-1, and the formed phases are δ-Ni2Al3 and β-NiAl.

[0079]

[0080] h is the thickness of the aluminized coating, k0 is the frequency factor, which represents the rate of the diffusion process under ideal conditions, T is the Kelvin temperature, respectively represent the weight fraction (wt.%) of aluminum (Al) element, the content of aluminum in the aluminizing agent, and the weight fraction (wt.%) of ammonium chloride (NH4Cl), the content of ammonium chloride (NH4Cl) in the aluminizing agent, t is the aluminizing time, E α is the activation energy of the diffusion process, with the unit of joules per mole (J / mol) or kilojoules per mole (kJ / mol), which reflects the energy barrier that needs to be overcome for diffusion, R: the gas constant, approximately 8.314 J / (mol·K). It can be seen from the above formula that when the time is constant, the thickness of the aluminized coating is determined by However, the content of the catalyst is generally lower than that of the Al element. Therefore, the influence of the catalyst on the thickness is higher than that of the Al element content. For the diffusion coefficient, 5Al5 may be more inclined to the surface diffusion or grain boundary diffusion mechanism activated by the catalyst, resulting in a higher diffusion rate; 10Al2.5 may rely more on the volume diffusion mechanism due to the lower catalyst concentration, and the initial diffusion is slower; in addition, the lower concentration of aluminum (5 wt.%) means a larger chemical potential gradient and higher activity of aluminum at the initial stage of diffusion, so the diffusion rate may be faster.

[0081] At the initial stage of high-temperature diffusion, the aluminized coating first forms intermetallic compound Al3Ni on the surface layer of the substrate. The formation of this compound prevents aluminum from directly infiltrating into the substrate. Therefore, the further diffusion of aluminum atoms at high temperature requires crossing this layer of Al3Ni. As time goes by, aluminum atoms will penetrate the Al3Ni layer and diffuse into the substrate, resulting in the further growth of the Ni-Al alloy layer and the formation of intermetallic compounds with lower aluminum content, such as (Al3Ni + δ-Ni2Al3) and δ-Ni2Al3. At the same time, the reverse diffusion of nickel atoms in the substrate will also accelerate the formation of these intermetallic compounds with low aluminum content. In the thickness direction of the diffusion layer, there is a gradient difference in the aluminum concentration, and this concentration difference generates chemical potential energy, which promotes the diffusion of aluminum atoms into the superalloy substrate. The phase composition of the aluminide infiltration layer is closely related to the mutual diffusion rates of aluminum and nickel atoms. When the diffusion rate is high, the main compound formed in the Ni-Al alloy layer is the aluminum-rich phase β-NiAl. With the diffusion between aluminum and nickel atoms, the concentration difference gradually decreases, the chemical potential energy decreases, and the mutual diffusion rate also slows down. The main compounds formed in the Ni-Al alloy layer are δ-Ni2Al3 and β-NiAl phases. This is consistent with the influence of aluminum atom concentration on the mutual diffusion coefficient.

[0082] Combined with the EDS and XRD results analysis, the holding time has a slight influence on the phase composition obtained with different aluminizing agent ratios, and has a more obvious influence on the aluminized layer thickness. For 10Al5, the phase composition is always the β-NiAl phase; for 10Al2.5, the phase composition changes from the initial single Al3Ni phase to the Al3Ni phase on the outside and the δ-Ni2Al3 phase on the inside; for 5Al5, the phase composition is always the δ-Ni2Al3 phase; for 5Al2.5, there is always a layer of Al on the outermost layer, refractory elements gradually precipitate in the inner layer, and the middle layer with a darker color is Ni precipitated outwards. Generally, the process of aluminized layer formation is γ-Ni→Al3Ni / δ-Ni2Al3→δ-Ni2Al3→β-NiAl. However, under the same holding time, the aluminized layer thickness of the 10Al2.5 ratio is thicker than that of the 5Al5 ratio, but the phase composition is an incomplete δ-Ni2Al3. This is because in the 5Al5 ratio, there is less Al element around the sample and more catalyst content. Therefore, in the initial stage of aluminizing, the surrounding Al elements are enriched on the sample surface to form an Al-rich Al3Ni phase. During the subsequent holding process, since the speed of Al element enrichment on the surface is lower than the speed of Ni element outward diffusion, all the formed phases are Ni2Al3 phases formed by reacting with Ni in the matrix. For the 10Al2.5 ratio, due to sufficient Al elements, although the catalyst content is less, the reaction process of continuous Al element accumulation on the surface until the surrounding Al elements are exhausted is still higher than the speed of Ni element outward diffusion. During this process, Ni elements in the matrix diffuse outward to form Ni2Al3 phases with the Al3Ni phase, resulting in the situation where the outside is an Al-rich Al3Ni phase and the inside is a Ni2Al3 phase.

[0083] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a reference structure" does not exclude the existence of additional identical elements in the process, method, article or device including the element.

[0084] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating, characterized in that: The steps include: S1, selecting an aluminizing agent ratio to perform aluminizing treatment on the nickel-based high-temperature alloy; S2, the samples after aluminizing treatment were polished, the microstructure was observed by SEM, and the Al element distribution was analyzed by EDS line scanning and point scanning; S3, scan along the thickness direction of the diffusion layer, and take ten data points at equal intervals to measure the Al concentration, and take the average value of the data of the three points on both sides of each point, and obtain the fitting constant of the aluminizing agent formula selected in S1 after fitting; S4, substituting the fitting constant obtained in S3 into the expression of the interdiffusion coefficient between Ni and Al to obtain the diffusion coefficient; S5, for different aluminizing agent ratios, respectively calculate the diffusion coefficient of each ratio according to the above steps S3 to S4; S6, the interdiffusion rate of aluminum and nickel atoms determines the phase composition of the aluminide layer.

2. The method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating according to claim 1, characterized in that: The error of the Al concentration measurement values ​​at the three points in step S2 is less than 0.25%, and a set of Al concentration data points is obtained. These points are plotted in origin and fitted by the Boltzmann function to obtain a fitting graph, wherein the fitting formula is: Wherein, C is the Al concentration value, in wt.%; x is the distance of each data point from the surface, in μm; A, B, E, and F are fitting constants, and the fitting constants of the aluminizing agent ratio are obtained by fitting.

3. The method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating according to claim 1, characterized in that: The expression of the Ni / Al interdiffusion coefficient in S4 is as follows: The diffusion coefficient was obtained by auxiliary calculation using Matlab, where D(C) is the diffusion coefficient, A, B, E, and F are fitting constants, C is the Al concentration value, and t is the diffusion time.

4. The method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating according to claim 1, characterized in that: In the step S6, when the diffusion coefficient is higher than 9×10-13·m2·s-1, the compound formed in the Ni-Al alloy layer is mainly a β-NiAl aluminum-rich phase.

5. The method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating according to claim 1, characterized in that: In the step S6, when the diffusion coefficient is between 4×10-13·m2·s-1 and 9×10-13·m2·s-1, the compounds formed in the Ni-Al alloy layer are mainly δ-Ni2Al3 and β-NiAl phases.

6. The method for calculating the Al-Ni interdiffusion coefficient in an aluminized coating according to claim 1, characterized in that: In the step S6, when the diffusion coefficient is lower than 4×10-13·m2·s-1, the compound formed in the Ni-Al alloy layer is mainly Al 3Ni phase.

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