Calculation method for evaluating cemented carbide interface properties based on first principles

Abstract

A cemented carbide interface performance evaluation and calculation method based on first principles includes the following steps: S1, constructing multiple cemented carbide interface models to provide a basis for cemented carbide interface performance evaluation and calculation; S2, setting calculation parameters related to the cemented carbide interface model to optimize the cemented carbide interface model structure and determine the influence of different atoms and electrons on the cemented carbide interface bonding performance; S3, performing performance evaluation calculations on multiple cemented carbide interface models based on the calculation parameters to evaluate and determine which cemented carbide has the best interface bonding performance.

Description

Technical field:

[0001] The invention relates to a calculation method for evaluating the interface performance of cemented carbide based on first principles. Background technology:

[0002] WC / Co is one of the commonly used cemented carbides. Thanks to the good wettability between WC and Co, this type of cemented carbide has good mechanical properties. However, WC / Co currently faces many problems. First, Co is a scarce resource, and the raw material supply is difficult and the cost is high. Second, the performance of WC / Co decreases significantly in high temperature and strong corrosive environments, and Co has great harm to human health. In addition, Fe and Ni are also often used as binder phases in cemented carbides. Although they both have the advantages of abundant resources and low cost, the addition of Fe makes it difficult to achieve carbon balance in the cemented carbide, which will cause certain structural defects. After the addition of Ni, the mechanical properties of WC / Ni are far inferior to those of WC / Co and WC / Fe. Therefore, it is currently necessary to find a new material that can replace the traditional binder phase.

[0003] As one of the hot topics in the materials research field in recent decades, high entropy alloys have great potential to replace the traditional cemented carbide bonding phase. High entropy alloys are composed of five or more metal elements. Thanks to the high entropy effect, lattice distortion effect, hysteresis diffusion effect and cocktail effect of high entropy alloys, they not only have good mechanical properties at room temperature, but also do not degrade much in mechanical properties under high temperature, strong corrosion and multi-radiation environments. Although they have a high mixing entropy, the alloy system only contains a simple solid solution structure. Furthermore, the performance of cemented carbide is closely related to the interfacial bonding performance between the hard phase and the bonding phase. However, since pure WC itself is a brittle material, it is difficult to verify the interfacial bonding performance through wettability experiments. In addition, the existing conventional evaluation and verification methods have cumbersome operation steps and low verification efficiency, making it impossible to quickly and effectively evaluate the interface performance of cemented carbide. Summary of the invention:

[0004] The embodiment of the present invention provides a calculation method for evaluating the interface performance of cemented carbide based on first principles. The method is rationally designed, applies quantum mechanics theory, and approximately solves the Schrödinger equation through multiple basic constants of matter to obtain the ground state performance of the material, thereby building an interface model of cemented carbide. Based on the first principles as the theoretical basis, the wettability between different high entropy alloys and WC is analyzed through calculation and evaluation, that is, the interface bonding performance of different types of WC / HEA cemented carbides is determined, thereby finding the high entropy alloy with the best interface bonding performance with WC, completing a convenient and effective evaluation and calculation analysis of the cemented carbide interface performance, and solving the problems existing in the prior art.

[0005] The technical solution adopted by the present invention to solve the above technical problems is:

[0006] A method for evaluating and calculating the interface performance of cemented carbide based on first principles, the method comprising the following steps:

[0007] S1, construct various cemented carbide interface models to provide a basis for cemented carbide interface performance evaluation and calculation;

[0008] S2, setting calculation parameters related to the cemented carbide interface model to optimize the structure of the cemented carbide interface model and determine the effects of different atoms and electrons on the bonding performance of the cemented carbide interface;

[0009] S3, based on the calculation parameters, a performance evaluation calculation is performed on a plurality of cemented carbide interface models to evaluate and determine which cemented carbide has the best interface bonding performance.

[0010] The construction of various carbide interface models includes the following steps:

[0011] S1.1, calculate the stable atomic interface, select and insert the HCP-WC and FCC-Ni atomic models in the Materials Studio database, and select Ni atoms as the initial model of HEA;

[0012] S1.2, after calculating all possible interfaces between WC and Ni, the most stable interfaces can be determined by the energy of the interfaces, which are recorded as HCP-WC(0001) and FCC-Ni(111);

[0013] S1.3, expand the HCP-WC (0001) and FCC-Ni (111) interfaces to build a WC / HEA cemented carbide interface model, and use the mismatch formula to evaluate whether the cemented carbide interface model is reasonable and stable;

[0014] S1.4, replace the Ni atom in the initial model with Co, Cr, Fe, Al, Mo and Mn atoms, respectively, to obtain four WC / HEA cemented carbide interface models: WC / CoCrFeNi, WC / AlCoCrFeNi, WC / CoCrFeNiMo and WC / CoCrFeNiMn.

[0015] The mismatch formula is:

[0016]

[0017] where A1 is the surface area of ​​HCP-WC(0001), A2 is the surface area of ​​FCC-Ni(111), and Ω is the area of ​​the HCP-WC(0001) / FCC-Ni(111) interface.

[0018] When atoms are randomly replaced, it is necessary to ensure that adjacent atoms are not of the same type and that the atoms are randomly arranged to simulate the fully mixed state of actual powders.

[0019] Setting the calculation parameters related to the carbide interface model includes the following steps:

[0020] S2.1, the upper and lower layers of the HEA layer and the WC layer are fixed, and only the relaxation process of the WC and HEA contact layer is calculated;

[0021] S2.2, using CASTEP to calculate the total energy of the four WC / HEA cemented carbide overall models, the energy of the four HEA layers, and the energy of the WC layer, and then using the interface binding energy calculation formula to calculate the interface binding energy of the four WC / HEA cemented carbides;

[0022] S2.3, calculate the Electron density difference in CASTEP Calculation, and then analyze the Electron density and Electron density difference in CASTEP Analysis;

[0023] S2.4. Calculate the state density in CASTEP Calculation, including local state density and partial state density, and analyze the state density. By observing the state density diagram, the influence of different atoms and electrons on the bonding performance of the WC / HEA cemented carbide interface can be determined.

[0024] The performance evaluation calculation of various cemented carbide interface models based on calculation parameters includes the following steps:

[0025] S3.1, rank the interfacial binding energy of WC / HEA cemented carbide using the interfacial binding energy calculation formula;

[0026] S3.2, calculate the electronic structures of four WC / HEA cemented carbide interface models;

[0027] S3.3, calculate the local state density and partial state density of four WC / HEA cemented carbide interface models to explore the nature of atomic bonding from the perspective of atomic orbital hybridization, further analyze the relationship between electronic structure and interface bonding strength, and accurately evaluate the cemented carbide interface bonding performance.

[0028] The calculation formula of the interface binding energy is:

[0029]

[0030] Among them, E interface represents the total energy of the interface model, E WC and E HEAare the energies of the hard phase WC layer and the bonding phase HEA layer, respectively, and A is the cross-sectional area of ​​the cemented carbide interface model.

[0031] The present invention adopts the above structure, and provides a basis for cemented carbide interface performance evaluation calculation by constructing multiple cemented carbide interface models; by setting calculation parameters related to the cemented carbide interface model, the cemented carbide interface model structure is optimized, and the influence of different atoms and electrons on the cemented carbide interface bonding performance is determined; the performance evaluation calculation is performed on the multiple cemented carbide interface models through the calculation parameters to evaluate and determine which cemented carbide has the best interface bonding performance; and by atomic replacement, four WC / HEA cemented carbide interface models, namely WC / CoCrFeNi, WC / AlCoCrFeNi, WC / CoCrFeNiMo and WC / CoCrFeNiMn, are obtained, which has the advantages of simplicity, efficiency, accuracy and practicality. Description of the drawings:

[0032] Figure 1 It is a schematic diagram of the steps of the present invention.

[0033] Figure 2 This is the cemented carbide interface model construction and calculation flow chart of the present invention.

[0034] Figure 3 This is a model diagram of the cemented carbide interface of the present invention.

[0035] Figure 4 This is a table of calculation parameters for the cemented carbide interface bonding energy of the present invention.

[0036] Figure 5 These are the charge density diagram and charge density difference diagram of the cemented carbide interface model of the present invention.

[0037] Figure 6 It is the state density diagram of the cemented carbide model of the present invention. Specific implementation method:

[0038] In order to clearly illustrate the technical features of this solution, the present invention is described in detail below through specific implementation methods and in conjunction with the accompanying drawings.

[0039] like Figure 1-6 As shown in , a cemented carbide interface performance evaluation calculation method based on first principles includes the following steps:

[0040] S1, construct various cemented carbide interface models to provide a basis for cemented carbide interface performance evaluation and calculation;

[0041] S2, setting calculation parameters related to the cemented carbide interface model to optimize the structure of the cemented carbide interface model and determine the effects of different atoms and electrons on the bonding performance of the cemented carbide interface;

[0042] S3, based on the calculation parameters, a performance evaluation calculation is performed on a plurality of cemented carbide interface models to evaluate and determine which cemented carbide has the best interface bonding performance.

[0043] The construction of various cemented carbide interface models includes the following steps:

[0044] S1.1, calculate the stable atomic interface, select and insert the HCP-WC and FCC-Ni atomic models in the Materials Studio database, and select Ni atoms as the initial model of HEA;

[0045] S1.2, after calculating all possible interfaces between WC and Ni, the most stable interfaces can be determined by the energy of the interfaces, which are recorded as HCP-WC(0001) and FCC-Ni(111);

[0046] S1.3, expand the HCP-WC (0001) and FCC-Ni (111) interfaces to build a WC / HEA cemented carbide interface model, and use the mismatch formula to evaluate whether the cemented carbide interface model is reasonable and stable;

[0047] S1.4, replace the Ni atom in the initial model with Co, Cr, Fe, Al, Mo and Mn atoms, respectively, to obtain four WC / HEA cemented carbide interface models: WC / CoCrFeNi, WC / AlCoCrFeNi, WC / CoCrFeNiMo and WC / CoCrFeNiMn.

[0048] The mismatch formula is:

[0049]

[0050] where A1 is the surface area of ​​HCP-WC(0001), A2 is the surface area of ​​FCC-Ni(111), and Ω is the area of ​​the HCP-WC(0001) / FCC-Ni(111) interface.

[0051] When atoms are randomly replaced, it is necessary to ensure that adjacent atoms are not of the same type and that the atoms are randomly arranged to simulate the fully mixed state of actual powders.

[0052] Setting the calculation parameters related to the carbide interface model includes the following steps:

[0053] S2.1, the upper and lower layers of the HEA layer and the WC layer are fixed, and only the relaxation process of the WC and HEA contact layer is calculated;

[0054] S2.2, using CASTEP to calculate the total energy of the four WC / HEA cemented carbide overall models, the energy of the four HEA layers, and the energy of the WC layer, and then using the interface binding energy calculation formula to calculate the interface binding energy of the four WC / HEA cemented carbides;

[0055] S2.3, calculate the Electron density difference in CASTEP Calculation, and then analyze the Electron density and Electron density difference in CASTEP Analysis;

[0056] S2.4. Calculate the state density in CASTEP Calculation, including local state density and partial state density, and analyze the state density. By observing the state density diagram, the influence of different atoms and electrons on the bonding performance of the WC / HEA cemented carbide interface can be determined.

[0057] The performance evaluation calculation of various cemented carbide interface models based on calculation parameters includes the following steps:

[0058] S3.1, rank the interfacial binding energy of WC / HEA cemented carbide using the interfacial binding energy calculation formula;

[0059] S3.2, calculate the electronic structures of four WC / HEA cemented carbide interface models;

[0060] S3.3, calculate the local state density and partial state density of four WC / HEA cemented carbide interface models to explore the nature of atomic bonding from the perspective of atomic orbital hybridization, further analyze the relationship between electronic structure and interface bonding strength, and accurately evaluate the cemented carbide interface bonding performance.

[0061] The calculation formula of the interface binding energy is:

[0062]

[0063] Among them, E interface represents the total energy of the interface model, E WC and E HEA are the energies of the hard phase WC layer and the bonding phase HEA layer, respectively, and A is the cross-sectional area of ​​the cemented carbide interface model.

[0064] The working principle of the cemented carbide interface performance evaluation calculation method based on first principles in the embodiment of the present invention is: using quantum mechanics theory, the Schrödinger equation is approximately solved through multiple basic constants of matter to obtain the ground state properties of the material, and then the interface model of the cemented carbide is constructed. Based on the first principles as the theoretical basis, the wettability between different high entropy alloys and WC is analyzed through calculation and evaluation, that is, the interface bonding performance of different types of WC / HEA cemented carbides is determined, so as to find the high entropy alloy with the best interface bonding performance with WC, complete the convenient and effective evaluation and calculation analysis of the cemented carbide interface performance, and can quantitatively and qualitatively analyze the interface bonding performance of WC / HEA cemented carbide.

[0065] The main innovations of the present invention are: (1) constructing a WC / HEA cemented carbide interface model, mainly including WC / CoCrFeNi, WC / AlCoCrFeNi, WC / CoCrFeNiMo and WC / CoCrFeNiMn interface models based on HCP-WC and FCC-HEA; (2) calculating the interface binding energy, charge density and state density of WC / HEA. This is used to determine the interface binding performance between different HEAs and WC, and to analyze the relationship between the interface binding performance and interatomic bonding; (3) providing theoretical guidance for specific experiments, greatly reducing material waste and effectively improving experimental efficiency.

[0066] The overall solution mainly includes the following steps: constructing multiple cemented carbide interface models to provide a basis for cemented carbide interface performance evaluation calculations; setting calculation parameters related to the cemented carbide interface model to optimize the cemented carbide interface model structure and determine the influence of different atoms and electrons on the cemented carbide interface bonding performance; performing performance evaluation calculations on multiple cemented carbide interface models based on the calculation parameters to evaluate and determine which cemented carbide has the best interface bonding performance.

[0067] For the modeling process of the cemented carbide interface model, it is necessary to first calculate the stable interface of the atoms, select and insert the HCP-WC and FCC-Ni atomic models in the MaterialsStudio database, and select Ni atoms as the initial model of HEA; after calculating all possible interfaces between WC and Ni, the most stable interface can be determined by the energy level of the interface. This is also the interface where HEA is most likely to contact WC in the WC / HEA cemented carbide, namely HCP-WC (0001) and FCC-Ni (111).

[0068] Then, the HCP-WC (0001) and FCC-Ni (111) interfaces were expanded to construct the WC / HEA cemented carbide interface model. In order to ensure that the interface model is reasonable and stable, the mismatch degree ζ must not exceed 5% after the interface is super-celled.

[0069] The WC(0001) and Ni(111) interfaces were supercelled to 4×4 and 5×5, respectively, to construct the HCP-WC(0001) / FCC-Ni(111) interface model. The upper and lower three-layer model was used for modeling. On the one hand, the calculation difficulty was reduced as much as possible while ensuring the calculation accuracy. On the other hand, the interface bonding strength mostly depends on the first layer of contact surface. Although the number of layers is small, it can fully reflect the interface bonding performance.

[0070] Preferably, the mismatch formula is

[0071]

[0072] where A1 is the surface area of ​​HCP-WC(0001), A2 is the surface area of ​​FCC-Ni(111), and Ω is the area of ​​the HCP-WC(0001) / FCC-Ni(111) interface.

[0073] Regarding the calculation parameter settings, all calculations were completed using the density functional theory-based CASTEP software package in Materials Studio. Before the performance calculation, the WC / HEA cemented carbide interface model needed to be pre-structurally optimized. To appropriately reduce the amount of calculation during the structural optimization, the upper and lower layers of the HEA and WC layers were fixed, and only the relaxation process of the WC and HEA contact layers was calculated.

[0074] Calculate the Electron density difference in CASTEP Calculation, and then analyze the Electron density and Electron density difference in CASTEP Analysis. In the resulting charge density map and charge density difference map, you need to adjust the appearance of the model to observe the bonding between the interface atoms. In Atom, set Display style to None and Coloring to Color by Element; in Lattice, select Style as In-Cell, set Lattice to None and select Label; in Field, select Visible, Volume and Color by field values; in Isosurface, select Viaible and Dots. Use the Create slices tool to capture the required cross-section, and adjust the image color by changing the Color Mapping to obtain the charge density map and charge density difference map, respectively.

[0075] The density of states is calculated in CASTEP Calculation, including local density of states and partial density of states. When analyzing the density of states, it is necessary to select Density of states in CASTEP Analysis. When Full DOS is checked, LDOS is obtained, and when Partial is checked, PDOS is obtained. By observing the density of states diagram, the influence of different atoms and electrons on the bonding performance of the WC / HEA cemented carbide interface can be determined.

[0076] For calculation results and performance analysis, see the attached Figure 3 As shown in the figure, the order of interface bonding energy of cemented carbide is: WC / CoCrFeNiMn>WC / CoCrFeNi>WC / CoCrFeNiMo>WC / AlCoCrFeNi. It can be seen that the interface bonding energy performance of cemented carbide with CoCrFeNiMn added is the best.

[0077] In order to further analyze and gain a deeper understanding of the interface adhesion mechanism of cemented carbide, it is necessary to calculate the electronic structure of each cemented carbide interface model. The following quantitative calculation can be obtained:

[0078] Δρ=ρ interface -ρ WC -ρ HEA

[0079] Among them, ρ interface is the total charge density at the WC / HEA cemented carbide interface, ρ WC and ρ HEA are the charge densities of the WC layer and HEA layer respectively.

[0080] After analysis and calculation, as shown in the attached Figure 5 As shown in the figure, Mn, Fe and Co atoms all form strong bonds with W atoms, so CoCrFeNiMn is the material with the best bonding performance with WC among the four high entropy alloys. This also shows that the stronger the atomic bonding between the interfaces, the more conducive it is to maintaining the interface stability of WC / HEA cemented carbide, which is consistent with the calculation results of the interface binding energy.

[0081] Finally, the local density of states (LDOS) and partial density of states (PDOS) of four WC / HEA cemented carbide interface models are calculated, as shown in the attached figure. Figure 6 As shown in the figure, the nature of atomic bonding can be explored from the perspective of atomic orbital hybridization, and the relationship between electronic structure and interface bonding strength can be further analyzed. The atomic d orbital plays a major role in the interfacial atomic bonding in cemented carbide.

[0082] It should be noted that since the total number of electrons is equal to the integral of the curve in the DOS diagram, the DOS diagram can be used to study the energy state of all electrons in the system, and the peak and trend of the curve near the Fermi level are closely related to the properties of the substance.

[0083] In summary, the first-principles-based cemented carbide interface performance evaluation calculation method in the embodiment of the present invention uses quantum mechanics theory to approximately solve the Schrödinger equation through multiple basic constants of matter to obtain the ground state properties of the material, and then build an interface model of cemented carbide. Based on the first principles as the theoretical basis, the wettability between different high entropy alloys and WC is analyzed through calculation and evaluation, that is, the interface bonding performance of different types of WC / HEA cemented carbides is determined, so as to find the high entropy alloy with the best interface bonding performance with WC, complete the convenient and effective evaluation and calculation analysis of the cemented carbide interface performance, and can quantitatively and qualitatively analyze the interface bonding performance of WC / HEA cemented carbide.

[0084] The above specific implementation manner cannot be used as a limitation on the protection scope of the present invention. For those skilled in the art, any replacement, improvement or transformation made to the implementation manner of the present invention falls within the protection scope of the present invention.

[0085] Any matters not described in detail in the present invention are well-known technologies to those skilled in the art.

Claims

1. A calculation method for evaluating the interface performance of cemented carbide based on first principles, characterized in that: The evaluation calculation method comprises the following steps: S1, construct various cemented carbide interface models to provide a basis for cemented carbide interface performance evaluation and calculation; S2, setting calculation parameters related to the cemented carbide interface model to optimize the structure of the cemented carbide interface model and determine the effects of different atoms and electrons on the bonding performance of the cemented carbide interface; S3, based on the calculation parameters, a performance evaluation calculation is performed on a variety of cemented carbide interface models to determine which cemented carbide has the best interface bonding performance; The construction of various carbide interface models includes the following steps: S1.1, calculate the stable atomic interface, select and insert the HCP-WC and FCC-Ni atomic models in the Materials Studio database, and select Ni atoms as the initial model of HEA; S1.2, after calculating all possible interfaces between WC and Ni, the most stable interfaces can be determined by the energy of the interfaces, which are recorded as HCP-WC(0001) and FCC-Ni(111); S1.3, expand the HCP-WC (0001) and FCC-Ni (111) interfaces to build a WC / HEA cemented carbide interface model, and use the mismatch formula to evaluate whether the cemented carbide interface model is reasonable and stable; S1.4, replace the Ni atom in the initial model with Co, Cr, Fe, Al, Mo and Mn atoms respectively to obtain four WC / HEA cemented carbide interface models: WC / CoCrFeNi, WC / AlCoCrFeNi, WC / CoCrFeNiMo and WC / CoCrFeNiMn; The mismatch formula is: Where A1 is the surface area of ​​HCP-WC (0001), A2 is the surface area of ​​FCC-Ni (111), and Ω is the area of ​​the HCP-WC (0001) / FCC-Ni (111) interface; Setting the calculation parameters related to the carbide interface model includes the following steps: S2.1, the upper and lower layers of the HEA layer and the WC layer are fixed, and only the relaxation process of the WC and HEA contact layer is calculated; S2.2, using CASTEP to calculate the total energy of the four WC / HEA cemented carbide overall models, the energy of the four HEA layers, and the energy of the WC layer, and then using the interface binding energy calculation formula to calculate the interface binding energy of the four WC / HEA cemented carbides; S2.3, calculate the Electron density difference in CASTEP Calculation, and then analyze the Electron density and Electron density difference in CASTEP Analysis; S2.

4. Calculate the state density in CASTEP Calculation, including local state density and partial state density, and analyze the state density. By observing the state density diagram, the influence of different atoms and electrons on the bonding performance of the WC / HEA cemented carbide interface can be determined.

2. The first-principles-based cemented carbide interface performance evaluation and calculation method according to claim 1 is characterized in that: When atoms are randomly replaced, it is necessary to ensure that adjacent atoms are not of the same type and that the atoms are randomly arranged to simulate the fully mixed state of actual powders.

3. The method for evaluating the interface performance of cemented carbide based on first principles according to claim 1, characterized in that: The performance evaluation calculation of various cemented carbide interface models based on calculation parameters includes the following steps: S3.1, rank the interfacial binding energy of WC / HEA cemented carbide using the interfacial binding energy calculation formula; S3.2, calculate the electronic structures of four WC / HEA cemented carbide interface models; S3.3, calculate the local state density and partial state density of four WC / HEA cemented carbide interface models to explore the nature of atomic bonding from the perspective of atomic orbital hybridization, further analyze the relationship between electronic structure and interface bonding strength, and accurately evaluate the cemented carbide interface bonding performance.

4. The first-principles-based cemented carbide interface performance evaluation and calculation method according to claim 3 is characterized in that: The calculation formula of the interface binding energy is: Among them, E interface represents the total energy of the interface model, E WC and E HEA are the energies of the hard phase WC layer and the bonding phase HEA layer, respectively, and A is the cross-sectional area of ​​the cemented carbide interface model.

Images