CN116145133B - A method for laser epitaxial growth of nickel-based single crystal high-temperature alloy - Google Patents

Abstract

The invention belongs to the technical field of structural repair, and relates to a method for laser epitaxial growth of a nickel-based single crystal superalloy, which obtains temperature gradient distribution in a molten pool by numerical simulation of a laser cladding nickel-based single crystal alloy molten pool, accurately predicts the growth direction and the growth speed of dendrites by utilizing a theoretical model, and determining optimal laser process parameters by judging whether dendrite epitaxial growth is realized, and then carrying out laser cladding on the nickel-based single crystal superalloy by a laser cladding technology, so that the epitaxial directional growth of dendrite is realized, and the technical problem of epitaxial growth repair of the nickel-based single crystal superalloy blade is solved.

Description

A method for laser epitaxial growth of nickel-based single crystal high-temperature alloy

Technical Field

The invention belongs to the technical field of nickel-based single crystal material structure repair, and relates to a laser epitaxial growth method of a nickel-based single crystal high-temperature alloy.

Background Art

Nickel-based single crystal high-temperature alloy turbine blades have no grain boundaries, so the creep and thermal fatigue resistance of the material is greatly improved. The maximum operating temperature can reach 1100°C, and they have been widely used in aero engines and other fields.

Despite this, due to the harsh working environment, single crystal blades will still have surface defects such as cracks after working for a period of time, causing engine failure. At present, the general situation is that once cracks and other defects are found, they must be replaced, but nickel-based single crystal high-temperature alloy blades are expensive and the replacement cost is very high. Therefore, repairing nickel-based single crystal high-temperature alloy blades has become a research hotspot in various countries.

The ideal nickel-based single-crystal high-temperature alloy blade repair technology should be to make the crystal structure of the repaired material equivalent to the single crystal structure of the crystal, thereby ensuring the service life and reliability of the repaired blade.

Laser cladding has precise energy input, higher temperature gradient and better controllability, and is suitable for achieving grain epitaxial growth of turbine blades with complex structures.

In recent years, researchers have studied the application of laser cladding technology in the field of nickel-based single crystal high-temperature alloy repair. By controlling the laser process, laser repair of nickel-based single crystal alloys has been achieved. However, there are still many problems in accurately repairing single crystal alloys by laser.

The present invention proposes a method for accurately repairing single crystal high-temperature alloys by accurately controlling the epitaxial growth of dendrites through a theoretical model and performing calculations and simulations using MATLAB and simulation software, which can fill the theoretical gap in repairing single crystal alloys using laser cladding technology.

Summary of the invention

The purpose of the present invention is to provide a method for laser epitaxial growth of nickel-based single crystal high-temperature alloys using laser cladding technology. By using MATLAB and simulation software for calculation and simulation, suitable laser process parameters are screened to control the laser directional cladding of nickel-based single crystals to grow epitaxially along a suitable direction, thereby solving the technical problems in laser precision repair of nickel-based single crystal high-temperature alloys.

To achieve the above-mentioned purpose of the invention, the laser epitaxial growth method of nickel-based single crystal high-temperature alloy provided by the present invention comprises:

1) Establish a laser cladding model, load the Gaussian moving heat source model, and calculate the size of the laser cladding molten pool and the temperature gradient distribution, including:

a) Input the material composition of the nickel-based single crystal high-temperature alloy to be repaired into the JMatPro material performance simulation software, calculate the material characteristic parameters of the nickel-based single crystal high-temperature alloy, the melting temperature T, thermal conductivity k, specific heat capacity Cp, density ρ and melting latent heat L, and export the material characteristic parameters and define them in the Ansys simulation software;

b) According to the calculation formula of Gauss moving heat source model Input laser process parameters to establish Gaussian moving heat source, load the Gaussian moving heat source into Ansys simulation software by writing ANSYS APDL command stream, and use Gaussian moving heat source to realize laser processing simulation.

in:

R is reflectivity, %;

P is the laser output power, W;

ω is the incident laser spot radius, mm;

r is the transverse cylindrical coordinate;

c) Use Design Modeler software to establish a laser cladding model, set the laser to scan along the X-axis, and the positive direction of the Z-axis is the [001] direction of the nickel-based single crystal high-temperature alloy;

d) assigning the material characteristic parameters of the nickel-based single crystal high-temperature alloy derived from the JMatPro software to the substrate material and the cladding layer material in the established laser cladding model;

e) Setting boundary conditions for laser cladding molten pool simulation, including initial temperature T ₀ , convection heat transfer conditions, and surface thermal radiation conditions;

f) Solve the model to obtain the size of the laser cladding molten pool, and derive the temperature gradient distribution and its components G _x , G _y , and G _z in the X, Y, and Z axis directions.

Wherein, the step b) specifically involves loading a Gaussian moving heat source onto the upper surface of the laser cladding model substrate in the Ansys simulation software.

Furthermore, since the Gaussian moving heat source performs laser scanning along the X-axis, therefore:

r＝[(xv·t) ² +y ² ] ^0.5

in:

v is the laser scanning speed, mm/s;

t is the scanning time, s.

2) The growth direction of the dendrite is calculated by using the Hunt model and the vectorized calculation model, and the growth direction of the dendrite and the temperature gradient vector at any point in the laser cladding molten pool are obtained. Specifically, the following are the results:

a) In the Hunt model, the growth rate of the solidification interface front The laser heat source moving speed Satisfying relationship between:

The dendrite growth rate The growth rate of the solidification interface front Satisfying relationship between:

Combining the above two equations, we can get the relationship between the dendrite growth rate and the laser heat source moving speed:

in:

θ is the normal Angle with the laser moving direction;

Normal Angle with the crystallographic direction [hkl];

b) The components _Gx , _Gy , and _Gz in the X, Y, and Z directions of the molten pool obtained by solving the Ansys model are used to determine the advancement direction of the solidification interface front, that is, the normal direction, through the direction of the temperature gradient parallel to it, and then the angle between the advancement direction of the solidification interface and the dendrite growth direction is obtained.

c) Establish a vectorized calculation model and set the laser to scan along the [h ₁ k ₁ l ₁ ] crystal direction on the substrate surface of (h ₃ k ₃ l ₃ ). Therefore, the X, Y, and Z axes in the crystallographic orientation correspond to [h ₁ k ₁ l ₁ ], [h ₂ k ₂ l ₂ ], and [h ₃ k ₃ l ₃ ], respectively, where [h ₂ k ₂ l ₂ ] can be obtained by the cross product of [h ₁ k ₁ l ₁ ] and [h ₃ k ₃ l ₃ ]:

[h ₂ k ₂ l ₂ ]＝[h ₁ k ₁ l ₁ ]×[h ₃ k ₃ l ₃ ]

Temperature gradient vector of any point in the X, Y, and Z directions for:

The vector calculation is performed using MATLAB software to obtain the temperature gradient vector of any point in the molten pool in the X, Y, and Z directions.

3) Determine whether the temperature gradient and dendrite growth rate in the X, Y, and Z directions at any point in the molten pool can undergo CET transformation, and determine whether the dendrite epitaxial growth of the substrate can be achieved, and determine the optimal laser process parameters based on the range of dendrite growth.

CET transformation is the transformation from columnar crystal to equiaxed crystal. When CET transformation occurs, that is, ^Gn /V＜ _KCET , the columnar crystal will transform into equiaxed crystal, forming a non-directional structure; therefore, CET transformation is not desired, but ^Gn / _Vhkl ＞ _KCET calculated above is desired.

In the above judgment formula:

G is the temperature gradient at the solidification front;

V _hkl is the growth velocity of columnar dendrites along the [hkl] crystal direction;

K _CET is the CET transition critical value, which is a constant related to the material. The K _CET value of the nickel-based single crystal high-temperature alloy of the present invention is 2.7×10 ²⁸ ;

n is a material parameter, and the material parameter of the nickel-based single crystal high-temperature alloy of the present invention is 3.4.

The calculation of the above formula can determine whether the dendrite grows epitaxially into a single crystal.

As long as the ^Gn / _Vhkl ratio of a certain component satisfies the critical value _KCET , single crystal growth can be achieved, that is, dendrite epitaxial growth can be achieved; when the ^Gn / _Vhkl ratios of multiple components all meet the critical value _KCET , columnar dendrites preferentially grow along the direction with the largest temperature gradient.

Furthermore, it is continued to be determined whether the growth direction is substrate-oriented, and all laser process parameters that can achieve substrate-oriented dendrite epitaxial growth are screened out.

Furthermore, for laser process parameters that can achieve epitaxial growth of dendrites, the present invention determines the range of epitaxial growth of dendrites and sets the process parameters corresponding to the maximum range as the optimal laser process parameters.

4) Using the selected laser process parameters, a cladding layer is laser clad on the surface of a nickel-based single crystal high-temperature alloy substrate to achieve directional epitaxial growth of dendrites on the substrate surface.

Specifically, the optimal laser process parameters are set and the printing plan is determined based on the MATLAB prediction results. The laser output power, laser scanning speed, powder feeding rate, and incident laser spot diameter used in laser cladding are adjusted according to the printing plan. The coaxial powder feeding method is adopted, and argon gas is used to protect the substrate surface for laser cladding.

More specifically, during the laser cladding process, the substrate is heated every time the laser scans, so the laser output power should be adjusted appropriately during the cladding process to ensure a stable temperature gradient during the laser cladding process and ensure the conditions for epitaxial growth of dendrites.

The nickel-based single crystal high-temperature alloy laser epitaxial growth method provided by the present invention can accurately predict the direction and range of dendrite epitaxial growth through a theoretical model before laser cladding, thereby controlling and optimizing the laser process parameters to influence the directional epitaxial growth of grains, thereby achieving precise control of dendrite epitaxial growth, so that the microstructure of the cladding layer can form a continuously epitaxially grown nickel-based single crystal structure, and provide theoretical guidance for the repair of nickel-based single crystal high-temperature alloy blades.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of laser cladding in the present invention.

FIG2 is a three-dimensional schematic diagram of the molten pool in the present invention, wherein α, β, and γ are the angles between the optimal growth directions [100], [010], and [001] of dendrites in a nickel-based single crystal high-temperature alloy and the normal direction of any point in the molten pool.

FIG. 3 is a metallographic structure image of Example 1.

FIG. 4 is a metallographic structure image of Example 2.

FIG. 5 is a metallographic structure image of Comparative Example 1.

Implementation

The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of the present invention so that those skilled in the art can well understand and utilize the present invention, rather than limiting the scope of protection of the present invention.

The production processes, experimental methods or detection methods involved in the embodiments and comparative examples of the present invention are all conventional methods in the prior art unless otherwise specified, and their names and/or abbreviations are all conventional names in the field and are very clear and unambiguous in the relevant application fields. Technicians in the field can understand the conventional process steps based on the names and apply the corresponding equipment to implement them according to conventional conditions or the conditions recommended by the manufacturer.

The various instruments, equipment, raw materials or reagents used in the embodiments of the present invention are not particularly limited in terms of their sources, and are all conventional products that can be purchased through regular commercial channels, or can be prepared according to conventional methods well known to those skilled in the art. Other matters not covered in the present invention are known technologies.

The following embodiments of the present invention use DD6 nickel-based single crystal high-temperature alloy as the substrate material to be repaired and GH738 nickel-based high-temperature alloy as the cladding layer material, and repair the substrate according to the laser cladding method shown in FIG. 1 .

During the laser cladding process, the optimal growth directions of dendrites [100], [010] and [001] in nickel-based single crystal superalloys are aligned with the normal vector of any point in the molten pool. The angles are defined as α, β and γ respectively, and the molten pool simulation diagram is shown in Figure 2.

Since the compositions of DD6 and GH738 are similar, in order to make the simulation results more easily convergent, the thermophysical property parameters of the same material are used for simulation in the following embodiments.

Example

Example 1

1) Establish a laser cladding model in the Design Modeler software, set the laser to scan along the X-axis, and set the positive direction of the Z-axis to the [001] direction of the nickel-based single crystal high-temperature alloy. The substrate size of the established laser cladding model is 20×10×5mm, and the cladding layer size is 20×1×0.5mm.

2) The structural unit is divided by uniform hexahedral grid, and the following thermophysical parameters of DD6 nickel-based single crystal high-temperature alloy are obtained by solving with JmatPro software: characteristic melting temperature 1615K, thermal conductivity 0.0332kj/(m·s·K), specific heat capacity 0.773kj/(kg·K), density 8780kg/m ³ , melting latent heat 99kj/kg, and they are assigned to the base material and the cladding layer material respectively.

3) Set the initial surface temperature of the laser cladding model to 22°C, conduct convective heat exchange with the air, and load the heat exchange on the model surface through software. Set the laser loading surface to have thermal radiation, and the radiation coefficient is 0.8.

4) Establish an orthogonal experiment, using laser powers of 200W, 400W, and 800W, scanning speeds of 5mm/s, 10mm/s, and 20mm/s, a powder feeding rate of 10g/min, a spot diameter of 4mm, and a laser reflectivity of 50%. Use ANSYS APDL to load the Gaussian moving heat source command flow and perform ANSYS simulation to obtain the influence of laser process parameters on the molten pool and the temperature gradient distribution inside the molten pool.

5) The different temperature gradient distribution results obtained by simulation are brought into the dendrite vectorization calculation model through MATLAB software to predict the preferred growth direction and speed of the dendrite.

Finally, it can be obtained that when the laser process parameters are laser power 800W and scanning speed 10mm/s, the ^Gn / _Vhkl ratio on the Z axis at the bottom of the molten pool is 3.08× ¹⁰²⁸ , which is greater than the critical value _KCET , and the growth area accounts for 70.5% of the molten pool area, the largest area, and the cladding layer can achieve dendrite epitaxial growth with the largest growth area.

6) Take the nickel-based single crystal high-temperature alloy with the substrate material of DD6, use the non-destructive testing method to find the repair part, determine the substrate orientation and cut the repair part, and perform pretreatment before laser cladding repair. After grinding and polishing the part to be repaired, use acetone and alcohol to clean the surface of the alloy to be repaired.

7) Determine the printing plan according to the dendrite prediction range obtained from the above prediction results, adjust the laser process parameters, ensure a stable temperature gradient during the laser processing, keep the laser heat flow direction vertical, and use GH738 powder to repair the DD6 nickel-based single crystal.

The process parameters set for the first layer of laser cladding scanning are as follows: laser power 800W, scanning speed 10mm/s, powder feeding amount 10g/min, spot diameter 4mm, protective gas argon gas output 15ml/min, and coaxial powder feeding method is used for laser cladding.

Because the substrate is heated every time the laser scans, the laser power should be appropriately reduced in the subsequent scanning process to reduce the heat input and ensure the epitaxial growth of the dendrite.

8) After the laser cladding repair is completed, the substrate material is treated to remove residual thermal stress and defect and damage detection is performed.

The metallographic structure of the blade after repair is shown in Figure 3, where the left picture is the metallographic picture of the substrate to be repaired, and the right picture is the metallographic picture of the repair layer. It can be seen that epitaxial growth of dendrites has been achieved after repair, forming a dendrite structure that is finer than the substrate.

Example 2

In the actual laser cladding repair process, in order to reduce the residual stress generated by the laser cladding process and avoid cracking, an in-situ preheating process is generally used during the laser cladding process. Therefore, unlike Example 1, this embodiment sets the low temperature zone preheating temperature of the nickel-based single crystal high temperature blade DD6 substrate during the laser cladding process to be about 950°C.

1) Set the initial surface temperature of the laser cladding model to 950°C, conduct convection heat exchange with the air, and load the heat exchange on the model surface through software. Set the laser loading surface to have thermal radiation, and the radiation coefficient is 0.8.

2) Establish an orthogonal experiment, using laser powers of 500W, 1000W, and 1500W, scanning speeds of 5mm/s, 10mm/s, and 20mm/s, powder feeding rate of 10g/min, spot diameter of 4mm, and laser reflectivity of 50%. Use ANSYS APDL to load the Gaussian moving heat source command flow and perform Ansys simulation to obtain the influence of laser process parameters on the molten pool and the temperature gradient distribution inside the molten pool.

3) Similarly, the different temperature gradient results obtained by simulation are brought into the dendrite vectorization calculation model through MATLAB software to predict the preferred growth direction and speed of the dendrite.

Finally, when the laser process parameters are laser power 1500W and scanning speed 10mm/s, the ^Gn / _Vhkl ratio on the Z axis at the bottom of the molten pool is 2.91× ¹⁰²⁸ , which is greater than the critical value _KCET , and the growth area accounts for 58.2% of the molten pool area, the largest area. The cladding layer can achieve dendrite epitaxial growth and the growth area is the largest.

4) Preheat the substrate to 950°C, determine the printing plan according to the predicted range of dendrites, adjust the laser process parameters, ensure a stable temperature gradient during the laser processing, keep the laser heat flow direction vertical, and use GH738 powder to repair the DD6 nickel-based single crystal.

The process parameters for the first layer are as follows: laser power 1500W, spot diameter 4mm, scanning speed 10mm/s, powder feeding rate 10g/min, protective gas argon gas output 15ml/min, and coaxial powder feeding for cladding. After each scan, the laser power is appropriately reduced to reduce heat input and ensure epitaxial growth of dendrites.

5) In order to ensure service stability, the repaired single crystal alloy is subjected to standard solution treatment (1300°C, 4h).

The metallographic structure of the blade repair layer after repair is shown in Figure 4 (a), and Figure 4 (b) is the metallographic picture after solution treatment. It can be seen that the epitaxial growth of dendrites has been achieved in this embodiment, and no recrystallization has occurred after standard solution treatment. Therefore, a higher preheating temperature is an effective means to reduce residual stress in laser formed high-temperature alloy samples.

Comparative Example 1

The low temperature zone preheating temperature of the nickel-based single crystal high temperature alloy DD6 substrate is set to 700°C, and the other laser process parameters are the same as in Example 2, with the laser power of 1500W, the spot diameter of 4mm, the scanning speed of 10mm/s, the powder feeding rate of 10g/min, the protective gas argon gas output of 15ml/min, and the coaxial powder feeding method is used for laser cladding.

The repaired single crystal alloy was subjected to standard solution treatment (1300°C, 4h).

The metallographic structure of the blade repair layer after repair is shown in Figure 5 (a), and Figure 5 (b) is the metallographic picture after solution treatment. It can be seen that although the epitaxial growth of dendrites is also achieved in this comparative example, severe recrystallization occurs after the standard solution treatment, destroying the consistency of single crystal orientation. Therefore, in order to reduce the generation of residual stress during laser processing, the nickel-based single crystal alloy substrate needs to be preheated, and the preheating temperature exceeds 700°C.

The above embodiments of the present invention do not describe all the details in detail, nor limit the present invention to the above embodiments. Various changes, modifications, substitutions and variations made by ordinary technicians in this field without departing from the principles and purpose of the present invention should be included in the protection scope of the present invention.

Claims (5)

1. A laser epitaxial growth method of a nickel-based single crystal superalloy, comprising:

1) Establishing a laser cladding model, loading a Gaussian moving heat source model, and calculating to obtain the size and the temperature gradient distribution of a laser cladding molten pool, wherein the method specifically comprises the following steps of:

a) Inputting the material components of the nickel-base single crystal superalloy to be repaired into JMatPro material performance simulation software, calculating to obtain the material characteristic parameter characteristic melting temperature T, the heat conductivity coefficient k, the specific heat capacity Cp, the density rho and the latent heat of melting L of the nickel-base single crystal superalloy, deriving the material characteristic parameter, and defining the material characteristic parameter in Ansys simulation software;

b) According to a Gaussian moving heat source model calculation formula Inputting laser process parameters to establish a Gaussian moving heat source, loading the Gaussian moving heat source into Ansys simulation software by writing ANSYS APDL command stream, realizing simulation of laser processing by using the Gaussian moving heat source,

Wherein:

r is reflectivity,%;

P is the laser output power, W;

omega is the radius of an incident laser spot and mm;

r is a transverse cylindrical coordinate;

c) Establishing a laser cladding model by using Design model software, and setting laser to sweep along an X axis, wherein the positive direction of the Z axis is the [001] direction of the nickel-based single crystal superalloy;

d) Respectively endowing the material characteristic parameters of the nickel-based single crystal superalloy derived by JMatPro software to a substrate material and a cladding layer material in the established laser cladding model;

e) Setting boundary conditions of laser cladding molten pool simulation, including an initial temperature T ₀, a convection heat exchange condition and a surface heat radiation condition;

f) Carrying out model solving to obtain the size of a laser cladding molten pool, and deriving temperature gradient distribution and a component G _x、G_y、G_z of the temperature gradient distribution in the X, Y, Z axial direction;

2) Calculating the dendrite growth direction through a Hunt model and a vectorization calculation model, and solving to obtain the dendrite growth direction and a temperature gradient vector of any point in a laser cladding molten pool, wherein the method specifically comprises the following steps:

a) According to the growth speed of the front edge of the solidification interface in the Hunt model And the moving speed of the laser heat sourceThe following relation is satisfied:

Dendrite growth rate Growth rate at front edge of solidification interfaceThe following relation is satisfied:

the two methods are combined to obtain the relation between the dendrite growth speed and the moving speed of the laser heat source:

Wherein:

theta is the normal line An included angle with the moving direction of the laser;

Is normal line Included angle with crystallographic direction [ hkl ];

b) The component G _x、G_y、G_z in the X, Y, Z axis direction in the molten pool obtained by the Ansys model solution, the advancing direction of the front edge of the solidification interface, namely the normal direction, is determined by the direction of the temperature gradient parallel to the component G _x、G_y、G_z, so that the included angle between the advancing direction of the solidification interface and the dendrite growth direction is obtained

C) Establishing a vectorization calculation model, and setting laser to sweep along the [ h ₁k₁l₁ ] crystal direction on the surface of the substrate of (h ₃k₃l₃), wherein the X, Y, Z axes in the crystal orientation correspond to [ h ₁k₁l₁],[h₂k₂l₂],[h₃k₃l₃ ], and [ h ₂k₂l₂ ] can be obtained by the cross multiplication of [ h ₁k₁l₁ ] and [ h ₃k₃l₃ ]:

[h₂k₂l₂]＝[h₁k₁l₁]×[h₃k₃l₃]

Temperature gradient vector of any point in X, Y, Z three directions The method comprises the following steps:

The vectorization calculation is carried out by utilizing MATLAB software, and the temperature gradient vector of any point in the molten pool in three directions X, Y, Z is obtained by solving

3) Judging whether CET conversion can occur to any point in the molten pool in the X, Y, Z directions and the dendrite growth speed, judging whether dendrite epitaxial growth of the substrate can be realized, and determining optimal laser process parameters through the dendrite growth range, wherein the optimal laser process parameters specifically are as follows:

according to a judgment formula: g ⁿ/V_hkl＞K_CET judging that dendrite grows into single crystal through epitaxial growth;

Wherein:

G is the temperature gradient of the solidification front;

V _hkl is the growth rate of columnar dendrites along the [ hkl ] crystal direction;

K _CET is a CET transition critical value, and the value is 2.7X10 ²⁸;

n is a material parameter, and the value is 3.4;

When the G ⁿ/V_hkl ratio of a certain component is more than a critical value K _CET, single crystal growth, namely dendrite epitaxial growth can be realized; when the G ⁿ/V_hkl ratio of the components is more than the critical value K _CET, the columnar dendrite grows preferentially along the direction with the maximum temperature gradient;

continuously judging whether the growth direction is the substrate orientation or not, and screening out all laser process parameters of dendrite epitaxial growth capable of realizing the substrate orientation;

Judging the range of the dendrite epitaxial growth of the laser process parameters capable of realizing dendrite epitaxial growth, and setting the process parameters corresponding to the maximum range as optimal laser process parameters;

4) And performing laser cladding on the surface of the nickel-base single crystal superalloy substrate by using the screened laser process parameters, and realizing dendritic crystal epitaxial directional growth on the surface of the substrate.

2. The laser epitaxial growth method of nickel-base single crystal superalloy according to claim 1, wherein a gaussian moving heat source is loaded on the upper surface of a laser cladding model substrate in Ansys simulation software.

3. The laser epitaxial growth method of the nickel-base single crystal superalloy according to claim 1, wherein the Gaussian moving heat source performs laser scanning along the X axis, and the transverse cylindrical coordinates r of the Gaussian moving heat source satisfy the following conditions:

r＝[(x-v·t)²+y²]^0.5

Wherein:

v is the laser scanning speed, mm/s;

t is the scan time, s.

4. The method for laser epitaxial growth of a nickel-base single crystal superalloy according to claim 1, wherein the step 4) includes: setting optimal laser process parameters according to MATLAB prediction results, and determining a printing scheme; according to the printing scheme, the laser output power, the laser scanning speed, the powder feeding speed and the incident laser spot diameter adopted by laser cladding are adjusted, a coaxial powder feeding mode is adopted, and the surface of the substrate is protected by utilizing argon gas to carry out laser cladding.

5. The method for laser epitaxial growth of nickel-base single crystal superalloy according to claim 4, wherein the laser output power is adjusted during laser cladding to ensure a stable temperature gradient during laser cladding and to ensure conditions for dendrite epitaxial growth.