阅读说明：本技术 脉冲激光3d打印单晶高温合金工艺参数的优选方法 (Optimization method for technological parameters of pulse laser 3D printing of single crystal superalloy ) 是由 梁静静 慈世伟 李金国 周亦胄 孙晓峰 *** 郑璇 于 2020-07-30 设计创作，主要内容包括：本发明提供一种脉冲激光3D打印单晶高温合金工艺参数的优选方法,包括如下步骤：准备金属基板及金属粉末；依据工艺范围设计正交试验；将所述金属粉末打印至所述金属基板上形成单道合金熔覆层,试验工艺参数在打印过程中被调整；获取所述单道合金熔覆层尺寸；根据所述单道合金熔覆层尺寸获取外延单晶生长指标；以所述试验工艺参数为自变量、以所述外延单晶生长指标为因变量形成映射函数,并通过线性拟合获得所述自变量与所述因变量的相关性参数；通过所述相关性参数获取所述自变量对所述因变量的影响趋势。本发明通过建立工艺参数与外延单晶生长指标之间的关系,能够缩短高温合金的制备工艺流程周期、降低制造低成本、提高作业效。(The invention provides a preferable method for pulse laser 3D printing of single crystal superalloy process parameters, which comprises the following steps: preparing a metal substrate and metal powder; designing an orthogonal test according to the process range; printing the metal powder on the metal substrate to form a single-channel alloy cladding layer, wherein test process parameters are adjusted in the printing process; obtaining the size of the single-channel alloy cladding layer; obtaining an epitaxial single crystal growth index according to the size of the single-channel alloy cladding layer; forming a mapping function by taking the test process parameters as independent variables and the epitaxial single crystal growth indexes as dependent variables, and obtaining correlation parameters of the independent variables and the dependent variables through linear fitting; and acquiring the influence trend of the independent variable on the dependent variable through the correlation parameter. By establishing the relationship between the process parameters and the epitaxial single crystal growth indexes, the invention can shorten the preparation process flow period of the high-temperature alloy, reduce the manufacturing cost and improve the operation efficiency.)

1. A preferable method for 3D printing of single crystal superalloy process parameters by pulse laser is characterized by comprising the following steps:

preparing a metal substrate and metal powder;

designing an orthogonal test according to the process range;

printing the metal powder on the metal substrate to form a single-channel alloy cladding layer, wherein test process parameters are adjusted in the printing process;

obtaining the size of the single-channel alloy cladding layer;

obtaining an epitaxial single crystal growth index according to the size of the single-channel alloy cladding layer;

forming a mapping function by taking the test process parameters as independent variables and the epitaxial single crystal growth indexes as dependent variables, and obtaining correlation parameters of the independent variables and the dependent variables through linear fitting;

and acquiring the influence trend of the independent variable on the dependent variable through the correlation parameter.

2. The preferred method of claim 1, wherein the experimental process parameters include at least one of laser output power P, pulse width t, powder feed rate m; the sizes of the single-channel alloy cladding layer comprise a cladding layer height H and a deposition height H_DEpitaxial growth height H_ELength L of single pass, area S of cladding area, and alloy density rhoAt least one; the epitaxial single crystal growth index comprises a difference value (R) between an epitaxial growth ratio and a cladding ratio_E-R_D) Deposition height H_DAt least one of the width W of the cladding layer and the utilization rate eta of the powder, wherein R_E＝H_E/H，R_D＝H_D/H，η＝S×L×ρ÷m÷T÷6×10^-13X 100%, wherein T is the cladding time.

3. The preferred method of claim 1, wherein obtaining the trend of the independent variable's influence on the dependent variable through the correlation parameter comprises:

taking an absolute value of the correlation parameter and normalizing to form a normalized correlation parameter;

and drawing a radar chart by using the normalized correlation parameters.

4. The preferred method of claim 1, wherein the surface of the metal substrate is subjected to a grinding and/or cleaning bake process prior to metal powder printing.

5. The preferable method according to claim 4, wherein the metal substrate after the cleaning and drying treatment is placed on a constant temperature water-cooled copper substrate workbench in an inert gas-protected glove box through a transition bin.

6. The preferred method of claim 1, wherein the metal powder is dried and cooled in a vacuum oven prior to printing the metal powder.

7. The preferred method according to claim 1, wherein the distance between the laser head of the numerically controlled machine tool and the metal substrate is adjusted to 14mm to 16mm before the metal powder printing is performed.

8. A preferred method according to claim 1, wherein the trial process parameters are adjusted during printing by means of a pre-set program.

9. The preferred method of claim 8, wherein the pre-set program is a pulsed laser 3D printed G-code.

10. The preferred method of claim 9, wherein the pulsed laser 3D printed G-code is generated using Python programming.

Technical Field

The invention belongs to the technical field of laser 3D printing, and particularly relates to an optimal selection method for technological parameters of pulse laser 3D printing of single crystal superalloy.

Background

The single crystal high temperature alloy is the first choice material of the turbine blade of the current cash aeroengine. The service environment of the single crystal blade is severe, the preparation cost is high, if the damaged blade can be repaired by adopting a proper method, the blade replacement is reduced, and the method has great economic significance and engineering significance. Laser melt molding (LMF) is a 3D printing method that uses a coaxial powder feed mode, which is widely used to produce and repair formed parts due to low heat input and high cooling rate. When LMF is applied to repair or manufacture of Single Crystal (SC) superalloy components, particularly SC turbine blades, it is necessary to ensure epitaxial growth of dendrites and control the formation of stray grains in front of the solid-liquid interface, i.e., to avoid the occurrence of single crystal to equiaxed crystal transformation (CET), because when CET occurs, stray crystals are formed, which affect the performance of the repair zone.

In addition, the production efficiency and powder utilization of the LMF process are also critical to the manufacture or repair of the actual single crystal. Although single crystal superalloy can be prepared by pulsed laser, the processing microstructure relation between the pulsed laser parameters and the CET, the production efficiency and the powder use efficiency is not systematically researched, so that a preferred method for 3D printing of the single crystal superalloy process parameters by the pulsed laser is needed.

Disclosure of Invention

Therefore, the technical problem to be solved by the invention is to provide a preferred method for pulse laser 3D printing of single crystal superalloy process parameters, which can shorten the preparation process flow period of the superalloy, reduce the manufacturing cost and improve the operation efficiency by establishing the relationship between the process parameters and the epitaxial single crystal growth indexes.

In order to solve the above problems, the present invention provides a preferred method for 3D printing of single crystal superalloy process parameters by using pulsed laser, comprising the following steps:

preparing a metal substrate and metal powder;

designing an orthogonal test according to the process range;

printing the metal powder on the metal substrate to form a single-channel alloy cladding layer, wherein test process parameters are adjusted in the printing process;

obtaining the size of the single-channel alloy cladding layer;

obtaining an epitaxial single crystal growth index according to the size of the single-channel alloy cladding layer;

forming a mapping function by taking the test process parameters as independent variables and the epitaxial single crystal growth indexes as dependent variables, and obtaining correlation parameters of the independent variables and the dependent variables through linear fitting;

and acquiring the influence trend of the independent variable on the dependent variable through the correlation parameter.

Preferably, the test process parameters comprise at least one of laser output power P, pulse width t and powder feeding rate m; the sizes of the single-channel alloy cladding layer comprise a cladding layer height H and a deposition height H_DEpitaxial growth height H_EAt least one of the area S of the cladding area with the single-channel length L and the alloy density rho; the epitaxial single crystal growthThe index includes the difference (R) between the epitaxial growth ratio and the cladding ratio_E-R_D) Deposition height H_DAt least one of the width W of the cladding layer and the utilization rate eta of the powder, wherein R_E＝H_E/H，R_D＝H_D/H，η＝S×L×ρ÷m÷T÷6×10^-13X 100%, wherein T is cladding time, H, HR, HD, HE, L, HS are all in mum, and S is in mum²P is in the unit of W, T and T are in the unit of s, m is in the unit of g/min, rho is in the unit of g/cm³。

Preferably, the obtaining of the influence trend of the independent variable on the dependent variable through the correlation parameter comprises:

taking an absolute value of the correlation parameter and normalizing to form a normalized correlation parameter;

and drawing a radar chart by using the normalized correlation parameters.

Preferably, before the metal powder printing is carried out, the surface of the metal substrate is subjected to grinding and/or cleaning and drying treatment.

Preferably, the metal substrate after being cleaned and dried is placed on a constant-temperature water-cooling copper substrate workbench in a glove box under the protection of inert gas through a transition bin.

Preferably, the metal powder is dried and cooled in a vacuum oven before the metal powder printing is performed.

Preferably, before the metal powder printing is performed, the distance between the laser head of the numerical control machine and the metal substrate is adjusted to 14mm-16 mm.

Preferably, the adjustment of the test process parameters during the printing process is achieved by means of a preset program.

Preferably, the preset program is a pulsed laser 3D printing G code.

Preferably, the pulsed laser 3D printing G code is generated using Python programming.

According to the optimal selection method for the pulse laser 3D printing of the single crystal superalloy process parameters, the corresponding test process parameters are adjusted in a larger range, the adjusted test process parameters are further adopted for laser 3D printing to form the alloy cladding layer, the corresponding epitaxial single crystal growth indexes can be further known through obtaining the size of the single channel alloy cladding layer, the influence trends of the test process parameters and the epitaxial single crystal growth indexes are further clarified through the correlation parameters between the test process parameters and the epitaxial single crystal growth indexes, and an operator can clarify the selection of the relevant process parameters in the specific pulse laser 3D printing of the single crystal superalloy according to the trend, so that the preparation process flow period of the superalloy can be obviously shortened, the manufacturing cost is reduced, and the like, The technical scheme of the invention can provide the adjustment trend of the associated parameters of the large-size metal single crystal structural member with uniform longitudinal gradient performance, and provides technical support for the field of rapid manufacturing.

Drawings

FIG. 1 is a schematic step diagram of a preferred method for 3D printing parameters of a single crystal superalloy process by using a pulsed laser in a pipe forming apparatus according to an embodiment of the present invention;

FIG. 2 is a schematic size diagram of a single-pass alloy cladding layer printed according to an embodiment of the present invention;

FIG. 3 is a radar chart plotted with normalized correlation parameters in an embodiment of the present invention;

FIG. 4 is a physical diagram of a single-pass alloy cladding layer printed by using the preferred process parameters of the preferred method of the present invention;

FIG. 5 is an EBSD photograph under an electron microscope at A in FIG. 4.

Detailed Description

Referring to fig. 1 to 5 in combination, according to an embodiment of the present invention, there is provided a preferred method for 3D printing single crystal superalloy process parameters by using a pulsed laser, including the following steps:

preparing a metal substrate and metal powder;

designing an orthogonal test according to a process range, wherein the process range specifically refers to a rough range of test process parameters adopted when laser 3D printing is adopted for an alloy material of a certain material;

printing the metal powder on the metal substrate to form a single-channel alloy cladding layer, wherein test process parameters are adjusted in the printing process;

obtaining the size of the single-channel alloy cladding layer;

obtaining an epitaxial single crystal growth index according to the size of the single-channel alloy cladding layer;

forming a mapping function by taking the test process parameters as independent variables and the epitaxial single crystal growth indexes as dependent variables, and obtaining correlation parameters of the independent variables and the dependent variables through linear fitting;

and acquiring the influence trend of the independent variable on the dependent variable through the correlation parameter.

In the technical scheme, the corresponding test process parameters are adjusted in a larger range, the adjusted test process parameters are further adopted for laser 3D printing to form the alloy cladding layer, the corresponding epitaxial single crystal growth indexes can be further known through obtaining the size of the single-channel alloy cladding layer, the influence trend of the test process parameters and the epitaxial single crystal growth indexes is further clarified through the correlation parameters between the test process parameters and the epitaxial single crystal growth indexes, and an operator can clearly select the related process parameters in the specific process of 3D single crystal high-temperature alloy printing by using pulse laser according to the trend, so that the preparation process flow period of the high-temperature alloy can be obviously shortened, the manufacturing cost is reduced, the operating efficiency is improved, and further, the technical scheme of the invention can provide the adjustment trend of the correlation parameters of the large-size metal single crystal structural component with uniform longitudinal gradient performance The method provides technical support for the field of rapid manufacturing.

Further, the test process parameters comprise at least one of laser output power P, pulse width t and powder feeding speed m; as shown in FIG. 2, the dimensions of the single-pass alloy cladding layer comprise a cladding layer height H and a remelting height H_RDeposition height H_DEpitaxial growth height H_ELength L of single channel, height H of impurity crystal region_SAt least one of the area S of the cladding area and the alloy density rho; the outer partThe single crystal growth index comprises the difference (R) between the epitaxial growth ratio and the cladding ratio_E-R_D) Deposition height H_DAt least one of the width W of the cladding layer and the utilization rate eta of the powder, wherein R_E＝H_E/H，R_D＝H_D/H，η＝S×L×ρ÷m÷T÷6×10^-13X 100%, wherein T is the cladding time.

The acquiring the influence trend of the independent variable on the dependent variable through the correlation parameter comprises the following steps:

taking an absolute value of the correlation parameter and normalizing to form a normalized correlation parameter;

and drawing a radar chart by using the normalized correlation parameters.

According to the technical scheme, the correlation parameters are processed through normalization, the data processing process is simplified, and the influence of each influence factor (namely the test process parameters) on the epitaxial single crystal growth index can be more visual by drawing a radar chart through the normalized correlation parameters, so that the adjustment of the operator on the correlation process parameters can be more clearly guided.

Before metal powder printing, the surface of the metal substrate is polished and/or cleaned and dried, the surface roughness of the metal substrate is changed, the surface of the metal substrate is kept smooth and clean, and the quality of a single-channel alloy cladding layer formed in a subsequent printing test can be guaranteed. Specifically, for example, before the test, the metal substrate is firstly polished by different types of sand paper, the surface roughness Ra of the metal substrate is controlled to be 2.5-5.0 μm, then the polished metal substrate is washed by absolute ethyl alcohol and dried by a blower, the surface is ensured to be flat and clean, and the metal substrate is sequentially placed into a glove vacuum box comprising a CNC (computer numerical control) machine tool to prevent the oxidation of a cladding layer in the test process. The metal substrate is formed by cutting a metal material to a specification of 50mm multiplied by 10mm multiplied by 5mm, the length of 50mm can ensure enough cladding distance, and the thickness of 5mm ensures that the metal substrate cannot deform greatly in a test.

And putting the cleaned and dried metal substrate on a constant-temperature water-cooling copper substrate workbench in a glove box protected by inert gas through a transition bin, so that the heat of the metal substrate printing the single-channel alloy cladding layer can be dissipated as soon as possible.

Preferably, before printing the metal powder, the metal powder is dried and cooled in a vacuum drying oven, and the moisture in the metal powder is removed to improve the uniformity and the fluidity of the metal powder, wherein the particle size of the metal powder is 53-105 μm.

Preferably, before the metal powder printing is carried out, the distance between a laser head of the numerical control machine tool and the metal substrate is adjusted to be 14-16 mm, preferably 15mm, so as to ensure that the laser beam and the metal powder flow sent out by the coaxial four argon powder feeding pipelines are well converged.

Preferably, the test process parameters are adjusted in the printing process by a preset program, specifically, the preset program is a pulse laser 3D printing G code, and the pulse laser 3D printing G code is generated by Python programming.

To further illustrate the technical solution of the present invention, the following description is given with reference to specific examples.