Method for predicting position and speed spatial distribution of cold spraying Ti-Al composite powder particles

Abstract

The invention relates to a cold spraying Ti-Al composite powder particle position and speed space distribution prediction method, which comprises the following steps of: firstly, establishing a three-dimensional geometric model of a Laval nozzle and a matrix for cold spraying, and then simulating in finite element simulation calculation software to obtain data of position distribution and speed space distribution of Ti particles and Al particles on the surface of the matrix; and integrating the data to obtain position distribution and speed space distribution of particle collision on the surface of a matrix in the cold spraying process of the composite powder particles, and giving different acceleration gas pressure and powder feeding gas pressure differences as well as particle sizes, output forms and spraying speeds of Ti and Al particles. And obtaining a plurality of position distribution diagrams and speed space distribution diagrams under different spraying simulation conditions, namely realizing the position and speed space distribution prediction of the Ti-Al composite powder particles. The method disclosed by the invention is simple and low in cost, and has important guiding significance for researching the cold spraying Ti-Al composite coating and other composite coatings.

Description

Technical Field

[0001] The invention relates to the field of surface engineering, and in particular to a method for predicting the distribution position and speed of particles colliding with a substrate surface during a cold spraying process. Background Art

[0002] Cold spray technology is an advanced solid-state deposition technology for powder particles based on the principles of aerodynamics and high-speed collision dynamics. During cold spraying, high-pressure gas is first introduced into a contraction-expansion Laval nozzle. After the gas flows through the nozzle throat, supersonic flow is generated. Then, the powder feeding gas axially delivers the spray powder into the airflow from the upstream of the nozzle. The powder particles are accelerated to a speed of 300~1200m / s through the entire nozzle, forming a high-speed particle flow and impacting the substrate, causing the substrate to undergo strong plastic deformation and form an effective bond with the substrate without melting. The particles remain solid throughout the deposition process, which can effectively avoid defects caused by high temperature and temperature changes. It is suitable for temperature-sensitive materials, oxidation-sensitive materials and phase-change-sensitive materials, such as aluminum, copper, titanium and their alloys. At present, cold spray technology has been successfully used to prepare most pure metals, alloys, metal-based composite materials, nanostructured metal coatings or bulk materials, etc.

[0003] It is precisely because cold spraying can form an effective bond between particles and substrates, and between particles without melting, and the coating has low porosity and high deposition efficiency. When cold spraying Ti and Al composite powders, the density, particle size, material properties and other factors of the two particles often cause the position distribution and velocity spatial distribution of the particles at the substrate to be different, resulting in different particle deposition positions, thicknesses, and densities after spraying, which in turn affects the final structure and performance of the coating. However, due to the high-speed characteristics of cold spray particles, it is impossible to directly obtain the velocity and spatial distribution of particles when they collide with the substrate during the experiment, which will inevitably make the final structure and performance uncontrollable. Summary of the invention

[0004] The purpose of the present invention is to avoid the shortcomings of the prior art and provide a method for predicting the position and velocity spatial distribution of cold-sprayed Ti-Al composite powder particles, which can simulate the cold-spraying process of Ti-Al composite powder, predict the particle position distribution and velocity spatial distribution at the body, effectively control the final structure and performance, and overcome the problem that the velocity and spatial distribution of particles with different characteristics in the cold-spraying composite powder process are difficult to directly obtain.

[0005] To achieve the above object, the technical solution adopted by the present invention is: a method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles, comprising the following steps: Step 1: Establishing a three-dimensional geometric model of a Laval nozzle and a substrate for cold spraying according to given Laval nozzle and substrate parameters; The parameters of the Laval nozzle include the diameter of the throat, the diameter of the accelerating gas inlet and the powder feeding gas inlet, the length of the upstream contraction section, the length of the downstream expansion section, and the diameter of the powder feeding pipe; the matrix parameters are the matrix thickness; Step 2: In the finite element simulation calculation software, the symmetry axis, the accelerating gas inlet and the powder feeding gas inlet, the outlet, the outflow boundary, the inner wall surface, the throat of the Laval nozzle and the surface of the substrate are set as the calculation area; At the same time, the boundary and boundary conditions of the calculation area and the gas properties of the accelerating gas and the powder feeding gas are set, and then the airflow field trajectory, velocity and temperature of the Laval nozzle are obtained through finite element simulation calculation; Step 3: Set the position where the spray particles are injected into the Laval nozzle as the powder feeding gas inlet, the spray particle injection method is perpendicular to the surface, the particle size distribution is Rosin-Rammler distribution, and the particles are randomly released at the powder feeding gas inlet; Next, the spraying particles are set to be Ti particles and Al particles, as well as the average particle size, output form and spraying speed of the Ti particles and Al particles, respectively, and the position distribution and velocity spatial distribution data of the Ti particles and Al particles on the substrate surface are obtained by finite element simulation calculation; The data of the position distribution and velocity spatial distribution of the Ti particles and Al particles on the substrate surface are integrated, that is, the position distribution and velocity spatial distribution of the particles colliding on the substrate surface during the cold spraying process of the Ti and Al composite powder particles are obtained; Step 4. Given different accelerating gas pressures and powder feeding gas pressure differences as well as the particle sizes, output forms and spraying speeds of Ti and Al particles, the position distribution diagram and velocity space distribution diagram under a variety of different spraying simulation conditions are obtained, thus realizing the prediction of the position and velocity space distribution of Ti-Al composite powder particles.

[0006] Furthermore, the airflow field, velocity slice cloud map, pressure slice cloud map, and streamline trajectory in the Laval nozzle are obtained by step 2, which are used to observe the influence of different working gas pressures and powder feeding gas pressure differences, as well as the particle size of Ti and Al particles and the spraying speed on the spraying particle position distribution and velocity spatial distribution.

[0007] Furthermore, in step 2, the inner wall surface and substrate surface of the Laval nozzle are both set to no-slip boundary and adiabatic boundary conditions, and the boundary condition type of the inner wall surface of the Laval nozzle is escape, and the boundary condition type of the substrate is trap.

[0008] Furthermore, the step 2 also includes meshing the three-dimensional geometric model of the cold-sprayed Laval nozzle and the substrate. During meshing, a boundary layer is added to the near-wall surface and throat area of ​​the cold-sprayed Laval nozzle. The mesh type of the meshing calculation domain is a hexahedral mesh, and the number of meshes is greater than six million.

[0009] Furthermore, the boundary and boundary conditions of the calculation area and the gas properties of the accelerating gas and the powder feeding gas are set in step 2, and then the airflow field trajectory, velocity and temperature of the Laval nozzle are obtained by finite element simulation calculation, which specifically includes the following steps: Step 21, with the acceleration gas inlet and the powder feeding gas inlet corresponding area of ​​the Laval nozzle as the gas inflow boundary, and the external jet area corresponding to the outlet as the outflow boundary, the inner wall surface of the Laval nozzle and the surface of the substrate are set as boundary conditions, and the inlet pressure of the acceleration gas inlet and the powder feeding gas inlet of the Laval nozzle, and the outlet pressure of the outlet and the external jet area are set as boundary conditions; Step 22, selecting an inert gas as an accelerating gas and a powder feeding gas, taking the inert gas as an ideal gas, and setting the properties of the inert gas to include: density is compressible, specific heat capacity is described by a piecewise polynomial, thermal conductivity is set to a constant, and at the same time, limiting the change process of the viscosity of the inert gas with temperature based on Sutherland's law; Step 23, solving the airflow field on the calculation area using a density-based coupled implicit solver; Step 24. In the finite element simulation software, the basic control equations to be solved for the fluid are the three basic conservation equations of mass, momentum and energy. At the same time, a standard k-ε turbulence model is established to obtain the airflow field trajectory, velocity and temperature of the Laval nozzle.

[0010] Furthermore, the inert gas is nitrogen, helium or argon.

[0011] Furthermore, the finite element simulation calculation used in step 3 is specifically as follows: The spray particle characteristics are set to use a discrete phase model to solve the acceleration and heating process of the particles and the spray particle shape; based on the calculation area and the boundary and boundary conditions of the calculation area, the temperature and pressure difference of the accelerating gas and the powder feeding gas of the Laval nozzle, the position distribution of Ti particles and Al particles on the substrate surface and the speed space distribution data are obtained.

[0012] Furthermore, in the finite element simulation calculation, the interaction between the sprayed particles and the gas flow and the mutual influence between the particles are set to be negligible, and the shape of the sprayed particles is spherical.

[0013] Furthermore, in step 4, the initial value ΔP of the pressure difference between the accelerating gas and the powder feeding gas is 0.1-0.7 MPa.

[0014] Furthermore, the Laval nozzle parameters include a throat diameter of 2-2.7 mm, an accelerating gas inlet diameter of 10-20 mm, an upstream contraction section length of 20-30 mm, a downstream expansion section length of 100-220 mm, and a powder feeder diameter of 1.5 mm; and the substrate parameters include a substrate thickness of 10-20 mm.

[0015] The beneficial effects of the present invention are: The present invention discloses a method for particle position distribution and velocity spatial distribution at a substrate after cold spraying of Ti-Al composite powder, specifically, using SolidWorks software to establish a three-dimensional geometric model of a Laval nozzle; using finite element simulation calculation software to divide the three-dimensional geometric model of the Laval nozzle into a grid, and after setting the calculation area, solution method and calculation conditions, the particle flow field trajectory and the information of the particles on the substrate surface are solved; and then using MATLAB software to simulate the process when the two particles collide with the substrate and perform post-processing, finally obtaining the position distribution and velocity spatial distribution of the particles colliding on the substrate surface during the cold spraying of Ti and Al composite powder particles.

[0016] Through the above simulation calculation method, the problem that the velocity and spatial distribution of particles with different characteristics in the cold spraying composite powder process are difficult to directly obtain is solved, which lays the foundation for the subsequent study of the deposition behavior of the two particles and the performance of the coating, and has the advantages of simple operation process, wide application range and low cost. In addition, the technical analysis method of the present invention is applicable to the position distribution and velocity spatial distribution analysis of composite powder particles of any two materials on the substrate surface during the cold spraying process, which provides a new method for studying the deposition behavior of composite powder particles and the position distribution and velocity spatial distribution on the substrate surface during the cold spraying process. It has important guiding significance for the study of cold sprayed Ti-Al composite coatings and other composite coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the three-dimensional model of the contraction-expansion type Laval nozzle structure of the present invention; Figure 2 Schematic diagram of the position distribution and velocity distribution of particles colliding on the substrate surface during cold spraying of spray particles under the same conditions. Among them, (a) is a schematic diagram of the position distribution and velocity distribution of Al particles; (b) is a schematic diagram of the position distribution and velocity distribution of Ti particles; and (c) is a schematic diagram of the position distribution and velocity distribution of Ti-Al composite powder particles. DETAILED DESCRIPTION

[0018] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0019] In order to achieve the above object, the present invention provides the following specific implementation methods: Embodiment 1: A method for predicting the spatial distribution of position and velocity of cold-sprayed Ti-Al composite powder particles, comprising the following steps: Step 1: Establish a three-dimensional geometric model of the Laval nozzle and substrate for cold spraying according to the given Laval nozzle and substrate parameters; The parameters of the Laval nozzle include the diameter of the throat 7, the diameters of the accelerating gas inlet 1 and the powder feeding gas inlet 2, the length of the upstream contraction section 8, the length of the downstream expansion section 9, and the diameter of the powder feeding pipe; the matrix parameter is the matrix thickness; The parameters of the Laval nozzle include the diameter of the throat 7 of 2-2.7 mm, the diameter of the accelerating gas inlet 1 of 10-20 mm, the length of the upstream contraction section 8 of 20-30 mm, the length of the downstream expansion section 9 of 100-220 mm, and the diameter of the powder feeder 5 of 1.5 mm; the matrix parameters include the matrix thickness of 10-20 mm; Step 2: In the finite element simulation calculation software, the symmetry axis of the Laval nozzle, the accelerating gas inlet 1 and the powder feeding gas inlet 2, the outlet 3, the outflow boundary 4, the inner wall surface 5, the throat 7 and the surface 6 of the substrate are set as the calculation area; wherein the inner wall surface and the substrate surface of the Laval nozzle are both set as no-slip boundary and adiabatic boundary conditions, and the boundary condition type of the inner wall surface of the Laval nozzle is escape, and the boundary condition type of the substrate is trap; Step 3: Mesh the three-dimensional geometric model of the cold sprayed Laval nozzle and the substrate. When meshing, add a boundary layer near the wall and throat area of ​​the cold sprayed Laval nozzle. The mesh type of the meshing calculation domain is hexahedral mesh, and the number of meshes is greater than six million.

[0020] Step 4: With the area corresponding to the accelerating gas inlet 1 and the powder feeding gas inlet 2 of the Laval nozzle as the gas inflow boundary, and the external jet area corresponding to the outlet 3 as the outflow boundary 4, the inner wall surface 5 of the Laval nozzle and the surface 6 of the substrate are set as boundary conditions, and the inlet pressure of the accelerating gas inlet 1 and the powder feeding gas inlet 2 of the Laval nozzle, and the outlet pressure and the outlet pressure of the external jet area are set as boundary conditions; Step 5: Select inert gas as the accelerating gas and powder feeding gas. The inert gas is nitrogen, helium or argon. The inert gas is taken as an ideal gas, and the properties of the inert gas are set as follows: the density is compressible, the specific heat capacity is described by a piecewise polynomial, and the thermal conductivity is set to a constant. At the same time, the change process of the viscosity of the inert gas with temperature is limited based on Sutherland's law; Step 6: Solve the airflow field on the calculation area using a density-based coupled implicit solver; Step 7: In the finite element simulation software, the basic control equations solved by the fluid are the three basic conservation equations of mass, momentum and energy. At the same time, a standard k-ε turbulence model is established to obtain the airflow field trajectory, velocity and temperature of the Laval nozzle, as well as the airflow field, velocity slice cloud map, pressure slice cloud map and streamline trajectory in the Laval nozzle, which are used to observe the influence of different working gas pressures and powder feeding gas pressure differences, as well as the particle size of Ti and Al particles and the spraying speed on the spraying particle position distribution and velocity spatial distribution.

[0021] Step 8: Set the position where the spray particles are injected into the Laval nozzle as the powder feeding gas inlet, the spray particle injection method is perpendicular to the surface, the particle size distribution is Rosin-Rammler distribution, and the particles are randomly released at the powder feeding gas inlet; and set the spray particles to Ti particles and Al particles, as well as the average particle size, output form and spray speed of Ti particles and Al particles respectively; Step 9: Set the spray particle characteristics to use a discrete phase model to solve the acceleration and heating process of the particles and the shape of the spray particles; according to the calculation area and the boundary and boundary conditions of the calculation area, the temperature and pressure difference of the accelerating gas and the powder feeding gas of the Laval nozzle, the position distribution and velocity spatial distribution data of the Ti particles and the Al particles on the substrate surface are obtained; and set the interaction between the spray particles and the gas flow and the mutual influence between the particles to be negligible, and the shape of the spray particles is spherical.

[0022] Step 10: Integrate the data of the position distribution and velocity spatial distribution of the Ti particles and Al particles on the substrate surface, that is, obtain the position distribution and velocity spatial distribution of particles colliding on the substrate surface during the cold spraying process of Ti and Al composite powder particles; Step 11: Given different accelerating gas pressures and powder feeding gas pressure differences as well as the particle sizes, output forms and spraying speeds of Ti and Al particles, the position distribution diagram and velocity space distribution diagram under a variety of different spraying simulation conditions are obtained, that is, the prediction of the position and velocity space distribution of Ti-Al composite powder particles is realized; wherein, the initial value ΔP of the pressure difference generated by the accelerating gas and the powder feeding gas is 0.1 to 0.7 MPa.

[0023] In order to further illustrate the scheme and effect of the present invention, the following specific test examples are provided: SolidWorks software was used to establish the three-dimensional geometric model of the Laval nozzle. Computational fluid dynamics software FLUENT was used to divide the three-dimensional geometric model of the Laval nozzle into grids, and the calculation area, calculation conditions and solution methods were set. Then, the particle flow field trajectory and the information of the particles on the substrate surface were obtained by solving the calculations. MATLAB software was used to post-process the results of the collision between the two particles and the substrate.

[0024] The specific steps of this specific test example are: S1. Set the actual dimensions of the convergent-divergent Laval nozzle and substrate, including throat diameter of 2.7 mm, inlet diameter of 20 mm, upstream contraction section length of 30 mm, downstream expansion section length of 220 mm, powder feeder diameter of 1.5 mm, substrate thickness of 10 mm, and use SolidWorks software to establish a three-dimensional geometric model; S2. Mesh the nozzle geometry model in the finite element simulation software. In order to make the result more accurate, mesh the boundary of the nozzle geometry model. Add a boundary layer near the wall and throat area of ​​the cold spray Laval nozzle. The mesh type of the mesh division calculation domain is hexahedral mesh, and the number of meshes is six million.

[0025] S3, with the area corresponding to the gas inlet of the Laval nozzle as the gas inflow boundary, and the external jet area corresponding to the outlet (3) as the outflow boundary, the inner wall surface and the substrate surface of the Laval nozzle are set as boundary conditions, and the inlet pressure of the powder feeding gas and the accelerating gas of the Laval nozzle, and the outlet pressure of the external jet area are set as boundary conditions; wherein the inner wall surface and the substrate surface of the Laval nozzle are both set as no-slip boundary and adiabatic boundary conditions, and the boundary condition type of the inner wall surface of the Laval nozzle is escape, and the boundary condition type of the substrate is trap; S4. Set the shape of the sprayed particles to be spherical, select nitrogen as the inert gas as the accelerating gas and powder feeding gas, take nitrogen as an ideal gas, and set the properties of nitrogen including: density is compressible, specific heat capacity is described by a piecewise polynomial, thermal conductivity is set to a constant, and at the same time, based on Sutherland's law, the change process of nitrogen viscosity with temperature is limited, and the interaction of particles on gas flow and the mutual influence between particles can be ignored.

[0026] S5. In the finite element simulation software, set the calculation area, solution method and calculation conditions, and define the solver type. Use the density-based coupled implicit solver to calculate the airflow field on the calculation domain. The basic control equations for fluid solution are the three basic conservation equations of mass, momentum and energy. Establish a turbulence model and use the standard k-ε turbulence model. S6, setting the temperature and pressure of the powder feeding gas to 300K and 4MPa, respectively, and the temperature and pressure of the accelerating gas to 773K and 3.9MPa, respectively, and the initial pressure difference ΔP generated is 0.1MPa; S7, setting the spraying particle parameters, setting the particle size distribution of the sprayed Ti particles to Rosin-Rammler, the maximum particle size to 0.053 mm, the minimum particle size to 0.015 mm, and the average particle size to 0.032 mm, and performing calculations in the finite element simulation software to obtain the position distribution of the Ti particles on the substrate surface and the velocity spatial distribution data; S8, repeating step S7, setting the corresponding parameters of the sprayed Al particles, the particle size distribution of the Al particles is Rosin-Rammler, the maximum particle size is 0.06 mm, the minimum particle size is 0.03 mm, and the average particle size is 0.045 mm, and calculating in finite element simulation software to obtain the position distribution of the Al particles on the substrate surface and the data of the velocity spatial distribution; S9. Post-process the results based on the finite element simulation software: Analyze the cold spray results of Ti and Al particles, observe the flow field, velocity slice cloud map, pressure slice cloud map, streamline trajectory and particle position distribution on the substrate surface in the Laval nozzle. For the three-dimensional geometric model of the Laval nozzle, integrate the position distribution and velocity space distribution of Ti and Al particles at the substrate, and make position distribution map and velocity space distribution map in MATLAB software; Then, the difference between the accelerating gas pressure and the powder feeding gas pressure, as well as the particle size and spraying speed of the Ti and Al particles were changed, and calculations were performed using finite element simulation software to analyze the changes in the particle position distribution and velocity spatial distribution on the substrate surface caused by the above factors.

[0027] The results of this test example are shown in the attached Figure 2 As shown, since the nozzle model is a three-dimensional axisymmetric structure, the results output here are symmetric about the XY plane. Figure 2 In the figure, the coordinate system represents the position distribution of particles on the substrate surface, the color represents the size of the velocity, the circular scattered points represent Ti particles, the triangular scattered points represent Al particles, and the size of the scattered points represents the particle size of a single particle. That is, the position distribution and velocity spatial distribution of the substrate surface after cold spraying of Ti-Al composite powder particles can be intuitively seen.

[0028] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for predicting the spatial distribution of position and velocity of cold sprayed Ti-Al composite powder particles, characterized in that: The following steps are involved: Step 1: Establishing a three-dimensional geometric model of a Laval nozzle and a substrate for cold spraying according to given Laval nozzle and substrate parameters; The parameters of the Laval nozzle include the diameter of the throat (7), the diameters of the accelerating gas inlet (1) and the powder feeding gas inlet (2), the length of the upstream contraction section (8), the length of the downstream expansion section (9), and the diameter of the powder feeding pipe; the matrix parameter is the matrix thickness; Step 2: In the finite element simulation calculation software, the symmetry axis of the Laval nozzle, the accelerating gas inlet (1) and the powder feeding gas inlet (2), the outlet (3), the outflow boundary (4), the inner wall surface (5), the throat (7) and the surface (6) of the substrate are set as the calculation area; At the same time, the boundary and boundary conditions of the calculation area and the gas properties of the accelerating gas and the powder feeding gas are set, and then the airflow field trajectory, velocity and temperature of the Laval nozzle are obtained through finite element simulation calculation; Step 3: Set the position where the spray particles are injected into the Laval nozzle as the powder feeding gas inlet, the spray particle injection method is perpendicular to the surface, the particle size distribution is Rosin-Rammler distribution, and the particles are randomly released at the powder feeding gas inlet; Next, the spraying particles are set to be Ti particles and Al particles, as well as the average particle size, output form and spraying speed of the Ti particles and Al particles, respectively, and the position distribution and velocity spatial distribution data of the Ti particles and Al particles on the substrate surface are obtained by finite element simulation calculation; The data of the position distribution and velocity spatial distribution of the Ti particles and Al particles on the substrate surface are integrated, that is, the position distribution and velocity spatial distribution of the particles colliding on the substrate surface during the cold spraying process of the Ti and Al composite powder particles are obtained; Step 4. Given different accelerating gas pressures and powder feeding gas pressure differences as well as the particle sizes, output forms and spraying speeds of Ti and Al particles, the position distribution diagram and velocity space distribution diagram under a variety of different spraying simulation conditions are obtained, thus realizing the prediction of the position and velocity space distribution of Ti-Al composite powder particles.

2. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 1, characterized in that: The airflow field, velocity slice cloud map, pressure slice cloud map, and streamline trajectory in the Laval nozzle are also obtained by the step 2, which are used to observe the influence of different working gas pressures and powder feeding gas pressure differences, as well as the particle size of Ti and Al particles and the spraying speed on the spraying particle position distribution and velocity spatial distribution.

3. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 1, characterized in that: In step 2, the inner wall surface and substrate surface of the Laval nozzle are both set to no-slip boundary and adiabatic boundary conditions, and the boundary condition type of the inner wall surface of the Laval nozzle is escape, and the boundary condition type of the substrate is trap.

4. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 1, characterized in that: The step 2 also includes meshing the three-dimensional geometric model of the cold-sprayed Laval nozzle and the substrate. When meshing, a boundary layer is added to the near-wall surface and throat area of ​​the cold-sprayed Laval nozzle. The mesh type of the meshing calculation domain is a hexahedral mesh, and the number of meshes is greater than six million.

5. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 1, characterized in that: The boundary and boundary conditions of the calculation area and the gas properties of the accelerating gas and the powder feeding gas are set in step 2, and then the airflow field trajectory, velocity and temperature of the Laval nozzle are obtained by finite element simulation calculation, which specifically includes the following steps: Step 21, with the area corresponding to the accelerating gas inlet (1) and the powder feeding gas inlet (2) of the Laval nozzle as the gas inflow boundary, and the external jet area corresponding to the outlet (3) as the outflow boundary (4), the inner wall surface (5) of the Laval nozzle and the surface (6) of the substrate are set as boundary conditions, and the inlet pressure of the accelerating gas inlet (1) and the powder feeding gas inlet (2) of the Laval nozzle, and the outlet pressure of the outlet and the external jet area are set as boundary conditions; Step 22, selecting an inert gas as an accelerating gas and a powder feeding gas, taking the inert gas as an ideal gas, and setting the properties of the inert gas to include: density is compressible, specific heat capacity is described by a piecewise polynomial, thermal conductivity is set to a constant, and at the same time, limiting the change process of the viscosity of the inert gas with temperature based on Sutherland's law; Step 23, solving the airflow field on the calculation area using a density-based coupled implicit solver; Step 24. In the finite element simulation software, the basic control equations to be solved for the fluid are the three basic conservation equations of mass, momentum and energy. At the same time, a standard k-ε turbulence model is established to obtain the airflow field trajectory, velocity and temperature of the Laval nozzle.

6. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 5, characterized in that: The inert gas is nitrogen, helium or argon.

7. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 1, characterized in that: The finite element simulation calculation used in step 3 is specifically as follows: The spray particle characteristics are set to use a discrete phase model to solve the acceleration and heating process of the particles and the spray particle shape; based on the calculation area and the boundary and boundary conditions of the calculation area, the temperature and pressure difference of the accelerating gas and the powder feeding gas of the Laval nozzle, the position distribution of Ti particles and Al particles on the substrate surface and the speed space distribution data are obtained.

8. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 7, characterized in that: In the finite element simulation calculation, the interaction between the sprayed particles and the gas flow and the mutual influence between the particles are set to be negligible, and the shape of the sprayed particles is spherical.

9. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to claim 7, characterized in that: The initial value ΔP of the pressure difference between the accelerating gas and the powder feeding gas in step 4 is 0.1-0.7 MPa.

10. The method for predicting the position and velocity spatial distribution of cold sprayed Ti-Al composite powder particles according to any one of claims 1 to 9, characterized in that: The parameters of the Laval nozzle include a throat diameter of 2 to 2.7 mm, an accelerating gas inlet diameter of 10 to 20 mm, an upstream contraction section length of 20 to 30 mm, a downstream expansion section length of 100 to 220 mm, and a powder feeder diameter of 1.5 mm; and a substrate thickness of 10 to 20 mm.

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