Method for predicting hardness of multi-principal element alloy bond coat for thermal barrier coating

Abstract

The application discloses a hardness prediction method for a multi-principal element alloy bonding layer of a thermal barrier coating, and aims to solve the problem of low efficiency of an experimental method in screening a multi-principal element alloy system suitable for a thermal barrier metal bonding layer. min and the maximum solid angle max , and then the distortion degree parameter γ is calculated; three, the distortion degree parameter δ caused by the radius difference of each atom in the alloy system to the crystal lattice is calculated; four, the dimensionless parameter ε reflecting the order of magnitude of the lattice distortion of the alloy system is calculated according to the parameters γ and δ; five, the ε∝HV real relation curve is drawn, and the hardness of the multi-principal element alloy bonding layer is predicted through the relation curve. The application realizes accurate prediction of the hardness of the multi-principal element alloy by establishing an intrinsic relation among the size effect of multiple atoms, the accumulation effect of multiple size atoms and the hardness of the alloy in the microcrystalline lattice of the alloy system.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of predicting the performance of metal materials, and in particular relates to a method for predicting the hardness of a multi-principal element alloy bond layer for a thermal barrier coating. BACKGROUND

[0002] Currently, alloy materials such as high-temperature alloys and heat-resistant materials are widely used in high-temperature service components such as cylinder covers, pistons, and turbine blades of internal combustion engines. During engine operation, metal materials are subjected to changes in temperature load and internal stress load. Generally, to improve the service life of hot end components and reduce maintenance costs, a thermal protection coating is prepared on the surface of the components, which is a common industrial technical approach.

[0003] Generally, the thermal protection coating of high-temperature components is mostly composed of a double-layer or even more-layer coating system of a metal transition layer and a high-temperature resistant ceramic top layer. The metal transition layer, also known as the metal bond layer, plays a crucial role in bonding the substrate and the ceramic top layer and adjusting the thermal and mechanical matching behavior between the metal and the ceramic dissimilar materials. According to failure behavior analysis, the main failure modes of this structure mainly occur in the thermal-mechanical behavior mismatch and thermal-mechanical fatigue caused by the metal bond layer. If the mechanical properties of the metal bond layer are not reasonably designed in advance, it will greatly increase the service cost of the components, reduce the service life of the components, and cause high cost and complexity problems in later maintenance, and even the safety of the entire equipment.

[0004] In recent years, as a new design concept, multi-principal element alloys, also known as multi-component alloys or complex concentrated alloys, or high-entropy alloys when the number of principal elements exceeds 4, have high degree of freedom in composition design, and thus exhibit many excellent properties in physical, chemical, and mechanical behaviors. For example, good oxidation resistance, high-temperature softening resistance, corrosion resistance, friction and wear resistance, high catalytic performance, magnetic guide performance, and so on. Therefore, this high degree of freedom in composition design has broad application prospects in many fields.

[0005] Currently, the hardness of multi-principal element alloy coating (bond layer) materials applicable to thermal barrier coatings is mostly obtained based on experimental methods. However, for alloys with high degree of freedom in composition design, the experimental method for screening multi-principal element alloy systems suitable for thermal barrier metal bond layers is undoubtedly a huge amount of work, which is not suitable for the updating and industrialization of thermal protection coatings for rapidly developing gas turbines and other hot end components. Therefore, there is an urgent need for a relatively simple, accurate, and engineering application value hardness prediction method for the early design of the mechanical hardness of new multi-principal element alloy coatings for thermal barrier coatings, which can provide scientific and theoretical support and engineering technical guidance for the rapid development of thermal protection coatings for hot end components of gas turbines. Summary of the Invention

[0006] The purpose of this invention is to address the problem of low efficiency in experimental screening of multi-principal alloy systems suitable for thermal barrier metal bonding layers, and to provide a method for predicting the hardness of multi-principal alloy bonding layers for thermal barrier coatings.

[0007] The method for predicting the hardness of the multi-principal element alloy adhesive layer for thermal barrier coatings of the present invention is implemented according to the following steps:

[0008] I. Establishing an intrinsic relationship model: The multi-element metallic elements in the multi-principal element alloy binder layer constitute the alloy system, and the intrinsic relationship model includes the following formulas:

[0009] ε×100∝HV real (a)

[0010] ε=δ / γ (b)

[0011]

[0012]

[0013] γ=θ min / θ max (e)

[0014]

[0015]

[0016] Where δ represents the distortion parameter caused by the radius difference of each atom in the alloy system to the lattice, γ represents the distortion parameter caused by the mismatch of atomic stacking in the alloy system, and HV real The hardness value of an alloy, r ave r represents the average atomic radius in the alloy system. i Represents the radius of element i, c i θ represents the atomic percentage of element i in the alloy system. min θ represents the smallest solid angle formed between atoms within the microcrystalline lattice of an alloy system. max r represents the maximum solid angle formed between atoms within the microcrystalline lattice of an alloy system. max The maximum atomic radius in the alloy system is represented by r. min Represents the smallest atomic radius in an alloy system;

[0017] II. The radius r of each element in the alloy system i Substituting into formula (d), the average atomic radius r in the alloy system is calculated. ave Then, the minimum solid angle θ formed between atoms in the microlattice of the alloy system is calculated using formula (f). minThe maximum solid angle θ formed between atoms in the microlattice of the alloy system is calculated using formula (g). max Then through θ max and θ min The distortion parameter γ caused by the mismatch of atomic stacking in the alloy system was calculated.

[0018] III. The average atomic radius r in the alloy system ave Substituting into formula (c), we obtain the parameter δ, which reflects the degree of lattice distortion caused by the difference in the radii of each atom in the alloy system.

[0019] IV. The dimensionless parameter ε, which reflects the order of lattice distortion of the entire alloy system, is calculated using the parameters γ and δ through formula (b).

[0020] 5. Substitute the dimensionless parameter ε obtained in step 4 into formula (a), using the value of ε×100 as the x-axis and HV as the y-axis. real Using this as the ordinate, we can plot ε∝HV. real The relationship curve is used to predict the hardness of the multi-principal element alloy bond layer.

[0021] This invention provides a method for predicting the hardness of thermal barrier coating metal bonding layers. This method establishes an intrinsic relationship between the multi-atom size effect, multi-size atom packing effect, and alloy hardness in the microcrystalline lattice of the alloy system. Accurate prediction of the hardness of multi-principal element alloys can be achieved through simple formula calculations. This prediction method combines the high accuracy of statistical regression calculations based on extensive experimental data with a significant reduction in the amount of experimentation required for material processing optimization. The derivation process is clear, and the basic physical parameters of the alloy system can be directly substituted into the formula for calculation.

[0022] The method for predicting the hardness of the multi-principal element alloy adhesive layer for thermal barrier coatings of the present invention has the following beneficial effects:

[0023] (1) The main principle of this invention for predicting the hardness of multi-principal element alloy adhesive layers for thermal barrier coatings is that the lattice distortion level parameter ε reflects the distortion strengthening effect caused by the multi-atom size effect in the microscopic lattice of disordered solid solution alloy materials. The higher the lattice distortion level, the stronger the solid solution strengthening effect of the material, and the higher the macroscopic mechanical properties of the alloy, i.e., the hardness. Through the intrinsic relation model ε=δ / γ, the theoretical design hardness value range of the alloy system can be predicted.

[0024] (2) This invention establishes the relationship between the solid solution strengthening effect caused by the microscopic matrix distortion of the alloy and the macroscopic mechanical strength, i.e., hardness. It predicts the theoretical hardness of the alloy system by superimposing the basic physical parameters of the metal material, which has scientific significance and engineering application value. Attached Figure Description

[0025] Figure 1 is a process flow chart of the method for predicting the hardness of the multi-principal element alloy bond coat for thermal barrier coatings in the embodiment;

[0026] Figure 2 is a schematic diagram of the lattice distortion effect caused by the multi-atom size effect in the lattice point array of the multi-principal element alloy system, wherein (a) is a schematic diagram of the stacking arrangement of atoms constituting the lattice, (b) is a schematic diagram of the largest solid angle formed by the largest atom in the lattice and the surrounding atoms, and (c) is a schematic diagram of the largest solid angle formed by the smallest atom in the lattice and the surrounding atoms;

[0027] Figure 3 is a parameter δ~γ corresponding relationship diagram, in which Bcc represents a body-centered cubic phase structure, Fcc represents a face-centered cubic phase structure, and IM represents an intermetallic compound;

[0028] Figure 4 is a corresponding relationship diagram of the predicted dimensionless parameter ε and the actual hardness value, i.e. ε∝HV real relationship diagram, in which ♦ represents a Main Fcc phase, i.e. the alloy system has a face-centered cubic phase structure as the main phase structure; and represents a Main Bcc phase, i.e. the alloy coating has a body-centered cubic phase structure as the main phase structure; and “1-0.3 error band for main Bcc phase” represents the upper limit band of the negative deviation of the alloy coating having a body-centered cubic phase structure as the main phase structure;

[0029] Figure 5 is an ε∝HV real relationship diagram, in which ■ represents the 4-1 sample, represents the 4-2 sample, and represents the 4-3 sample, Table 5-1 sample, the hexagon represents the 5-2 sample, the star represents the 5-3 sample, the downward triangle represents the 6-1 sample, and the diamond represents the 6-2 sample, Table 6-3 sample, in which the English represents the meaning, respectively: “1+0.3 error band” represents the upper limit band of the positive deviation of the actual hardness of the alloy coating from the predicted hardness; “1-0.3 error band” represents the upper limit band of the negative deviation of the actual hardness of the alloy coating from the predicted hardness; and “the ideal ratio equal to 1” represents that the ideal value of the ratio of the actual hardness of the alloy coating to the predicted hardness is equal to 1, i.e. no deviation. DETAILED DESCRIPTION

[0030] Specific embodiment one: the method for predicting the hardness of the multi-principal element alloy bond coat for thermal barrier coatings in the embodiment is implemented according to the following steps:

[0031] I. Establishing intrinsic relationship model, multi-principal element alloy bonding layer of multi-metallic elements constitutes an alloy system, intrinsic relationship model includes the following formula:

[0032] ε×100∝HV real (a)

[0033] ε=δ / γ (b)

[0034]

[0035]

[0036] γ=θ min / θ max (e)

[0037]

[0038]

[0039] Wherein δ represents the distortion degree parameter caused by the radius difference of each atom in the alloy system to the lattice, γ represents the distortion degree parameter caused by the stacking fault of each atom in the alloy system, HV real represents the hardness value of the alloy experiment, r ave represents the average atomic radius in the alloy system, r i represents the radius of i element, c i represents the atomic percentage of i element in the alloy system, θ min represents the minimum solid angle formed between atoms in the micro-lattice of the alloy system, θ max represents the maximum solid angle formed between atoms in the micro-lattice of the alloy system, r max represents the maximum atomic radius in the alloy system, r min represents the minimum atomic radius in the alloy system;

[0040] II. The radius r i of each element in the alloy system is brought into formula (d), and the average atomic radius r ave in the alloy system is calculated, and then formula (f) is used to calculate the minimum solid angle θ min formed between atoms in the micro-lattice of the alloy system, formula (g) is used to calculate the maximum solid angle θ max formed between atoms in the micro-lattice of the alloy system, and then θ max and θ min are used to calculate the distortion degree parameter γ caused by the stacking fault of each atom in the alloy system;

[0041] III. The average atomic radius r aveSubstitute the formula (c) into the formula (b), and the non-dimensional parameter ε reflecting the degree of lattice distortion in the whole alloy system is calculated.

[0042] Four, the non-dimensional parameter ε reflecting the degree of lattice distortion in the whole alloy system is calculated by the formula (b) with the parameters γ and δ;

[0043] Five, the non-dimensional parameter ε obtained in step four is substituted into the formula (a), and the value of ε x 100 is taken as the abscissa, and the HV real value is taken as the ordinate to draw the ε ∝ HV real curve, and the hardness of the multi-component alloy bonding layer is predicted through the curve.

[0044] In step one of the embodiment, δ represents the influence of the radius difference of each atom in the alloy system on the degree of lattice distortion, and γ represents the influence of the different solid angles formed by the coordination of different size atoms in the stacking arrangement of the alloy system on the degree of lattice distortion.

[0045] The multi-component alloy in the embodiment is a disordered solid solution alloy mainly composed of face-centered cubic lattice, body-centered cubic lattice and close-packed hexagonal lattice. The alloy phase composition can be a single phase structure mainly composed of any one of the three lattice structures, or a multi-phase structure composed of any number of phases.

[0046] The prediction method of the hardness of the multi-component alloy bonding layer of the thermal barrier coating can be applied to metal materials including multi-component alloy materials with equal or near equal atomic ratio (the atomic percentage of each element is 5-35%), and the number of components in the alloy system is greater than or equal to 3. The applicable processes include laser preparation process, plasma preparation process, spraying process and other high energy density preparation methods to obtain thermal barrier coatings. Based on the prediction method, the traditional experimental method of trial and error can be replaced, which is of great significance for the preliminary prediction of the hardness of the multi-component alloy and the auxiliary design of the material system.

[0047] Specific embodiment two: the difference between this embodiment and the specific embodiment one is that the radius value r i of the i element in step two is obtained by querying the standard database.

[0048] The standard database query in the embodiment can be obtained through the website https: / / www.webelements.com.

[0049] Specific embodiment three: the difference between this embodiment and the specific embodiment one or two is that the number of components in the multi-component alloy bonding layer is greater than or equal to 3.

[0050] The number of components in the embodiment refers to the number of multi-metal elements in the multi-component alloy bonding layer.

[0051] Embodiment four: the difference between this embodiment and one of the embodiments one to three is that the elements in the multi-principal element alloy bonding layer are in equal molar ratio or near equal molar atomic ratio.

[0052] Embodiment five: the difference between this embodiment and the embodiment four is that when the elements are in near equal molar atomic ratio, the molar atomic ratio of one element to other elements is (0.6-1.2):1.

[0053] Embodiment six: the difference between this embodiment and one of the embodiments one to five is that the multi-principal element alloy bonding layer is obtained by laser preparation process, plasma preparation process or thermal spraying preparation process.

[0054] Embodiment seven: the difference between this embodiment and one of the embodiments one to six is that the ratio of εx100 / HV real is 1±0.3.

[0055] When the ratio of εx100 / HV real is 1±0.3, it is considered that the theoretical predicted hardness is within the reasonable error range of the actual hardness.

[0056] Embodiment: the prediction method of the hardness of the multi-principal element alloy bonding layer for thermal barrier coating is implemented according to the following steps:

[0057] I. Obtain the atomic radius of the selected elements from the standard database, and obtain the radii of Ni, Co, Cr, Al, Fe and Si as 0.1246 nm, 0.1251 nm, 0.1249 nm, 0.1432 nm, 0.1241 nm and 0.1153 nm respectively. According to the thermodynamic theory, different component numbers and different contents of the above elements are designed. The multi-element metal elements in the multi-principal element alloy bonding layer form an alloy system, which is specifically a four-element alloy system NiCoCrAl 0.2 (4-1), NiCoCrAl 0.4 (4-2), NiCoCrAl 0.6 (4-3); a five-element alloy system NiCoCrFeSi 0.2 (5-1), NiCoCrFeSi 0.4 (5-2), NiCoCrFeSi 0.6 (5-3); a six-element alloy system NiCoCrFeSi 0.8 Al 0.2 (6-1), NiCoCrFeSi 0.6 Al 0.4 (6-2), NiCoCrFeSi 0.4 Al 0.6 (6-3); a total of nine groups of multi-principal element alloy coating compositions are designed.

[0058] II. For the series of alloys designed in step one, according to the formula where r ave represents the average atomic radius in the alloy system, r i represents the radius of element i, c i represents the atomic percentage of element i in the alloy system; the average atomic radii of each alloy system are calculated to be 0.1260 nm, 0.1270 nm, 0.1279 nm, 0.1242 nm, 0.1238 nm, 0.1235 nm, 0.1239 nm, 0.1250 nm, and 0.1261 nm, respectively. Further, the maximum atomic radius r max and the minimum atomic radius r min in each alloy system are brought into the formula and Then the maximum solid angle θ max and the minimum solid angle θ min formed between atoms in the micro-lattice of each alloy system are calculated, and then brought into the formula γ = θ min / θ max to obtain the distortion degree parameter γ caused by the stacking mismatch of each atom in each alloy system, which are 0.85771608, 0.858135142, 0.85850942, 0.916983103, 0.91687815, 0.916778516, 0.789036346, 0.789714216, 0.790386707, respectively.

[0059] III. The average atomic radius r ave obtained in step two is brought into the formula to calculate the lattice atomic size distortion degree parameter δ value of each alloy system, which are 3.525246287, 4.652917551, 5.342129791, 1.633819847, 2.195553479, 2.572807702, 4.218598049, 4.929424089, 5.385600871, respectively.

[0060] IV. The parameters δ and γ obtained in steps two and three are brought into the formula ε = δ / γ to obtain the dimensionless parameter ε reflecting the order of lattice distortion of the entire alloy system, which are 4.110038707, 5.422126802, 6.222563981, 1.781733864, 2.394596794, 2.806356886, 5.346519294, 6.242035399, 6.813880883, respectively.

[0061] Five, the designed nine kinds of alloy composition of multi-principal element alloy material is weighed according to the composition ratio, ball milling and mixing to obtain the powder for laser cladding, the powder is placed on the high-temperature alloy substrate by pre-coating method, and the multi-principal element alloy coating with metallurgical bonding effect is prepared by laser cladding process.

[0062] In this embodiment, the alloy coating obtained in step five is subjected to metallographic sample preparation to obtain a cross-section sample, HV hardness is collected at multiple points along the top of the sample towards the substrate direction, the average value of the obtained hardness value is taken as the standard value, and the formula ε x 100∝HV real The relationship curve is established, as shown in the attached Figure 5 The alloy composition designed and prepared in the embodiment is verified by establishing the intrinsic relationship between the micro-lattice parameters and the macro-hardness of the material. The ratio of the actual hardness value of the obtained alloy to the theoretically predicted value is within the error range of 1±0.3, accounting for 80%. It better conforms to the design criteria of actual engineering application, and the actual hardness value of each alloy changes in accordance with the law of ε∝HV rea , that is, the order of lattice distortion positively correlates with the trend of the actual hardness value of the alloy.

Claims

1. A method for predicting the hardness of a multi-principal element alloy adhesive layer for thermal barrier coatings, characterized in that... The prediction method is implemented through the following steps: I. Establishing an intrinsic relationship model: the multi-element metallic elements in the multi-principal element alloy binder layer constitute the alloy system. The intrinsic relation model includes the following formulas: ε×100∝HV real (a) ε=δ / γ (b) γ=θ min / i max (e) Where δ represents the distortion parameter caused by the radius difference of each atom in the alloy system to the lattice, γ represents the distortion parameter caused by the mismatch of atomic stacking in the alloy system, and HV real The hardness value of an alloy, r, represents the experimental hardness value. ave r represents the average atomic radius in the alloy system. i c represents the radius of element i. i θ represents the atomic percentage of element i in the alloy system. min θ represents the smallest solid angle formed between atoms within the microcrystalline lattice of an alloy system. max r represents the maximum solid angle formed between atoms within the microcrystalline lattice of an alloy system. max r represents the maximum atomic radius in the alloy system. min Represents the smallest atomic radius in an alloy system; II. The radius r of each element in the alloy system i Substituting into formula (d), the average atomic radius r in the alloy system is calculated. ave Then, the minimum solid angle θ formed between atoms in the microlattice of the alloy system is calculated using formula (f). min The maximum solid angle θ formed between atoms in the microlattice of the alloy system is calculated using formula (g). max Then through θ max and θ min The distortion parameter γ caused by the mismatch of atomic stacking in the alloy system was calculated. III. The average atomic radius r in the alloy system ave Substituting into formula (c), we obtain the parameter δ, which reflects the degree of lattice distortion caused by the difference in the radii of each atom in the alloy system. IV. The dimensionless parameter ε, which reflects the order of lattice distortion of the entire alloy system, is calculated using the parameters γ and δ through formula (b).

5. Substitute the dimensionless parameter ε obtained in step 4 into formula (a), using the value of ε×100 as the x-axis and HV as the y-axis. real Using this as the ordinate, we can plot ε∝HV. real The relationship curve is used to predict the hardness of the multi-principal element alloy bond layer.

2. The method for predicting the hardness of multi-principal element alloy adhesive layer for thermal barrier coatings according to claim 1, characterized in that... The radius value r of element i in step two i Obtained through database query.

3. The method for predicting the hardness of the multi-principal element alloy adhesive layer for thermal barrier coatings according to claim 1, characterized in that... The number of components in a multi-principal-element alloy bonding layer is greater than or equal to 3.

4. The method for predicting the hardness of multi-principal element alloy adhesive layer for thermal barrier coatings according to claim 1, characterized in that... The elements in the multi-principal alloy binder are in equimolar ratio.

5. The method for predicting the hardness of multi-principal element alloy adhesive layers for thermal barrier coatings according to claim 4, characterized in that... When the elements are in a near equimolar atomic ratio, the molar atomic ratio of one element to the other elements is (0.6~1.2):

1.

6. The method for predicting the hardness of multi-principal element alloy adhesive layers for thermal barrier coatings according to claim 1, characterized in that... The multi-principal alloy bonding layer is obtained by laser preparation, plasma preparation, or thermal spraying.

7. The method for predicting the hardness of multi-principal element alloy adhesive layer for thermal barrier coatings according to claim 1, characterized in that... In step five, ε×100 / HV real The ratio is 1 ± 0.3.

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