CN115351294A - Method for preparing nickel-based high-temperature alloy product by selective laser melting - Google Patents

Abstract

The application relates to the field of laser additive manufacturing, and discloses a method for preparing a nickel-based high-temperature alloy product by selective laser melting. According to the method, a low-power laser beam and a slower scanning speed are adopted for scanning a powder layer for the first time, the powder layer is preheated, the powder particles are pre-connected, and meanwhile, the thermal gradient between the powder layer and a workpiece is obviously reduced; and then fused and formed by a high-power laser beam at a faster scanning speed to obtain a formed layer. The method and the device accurately control the laser to scan energy input twice, avoid the problems of poor combination and unstable molten pool caused by powder splashing under the action of high-energy laser and metal powder, and inhibit the formation of pores; meanwhile, the residual stress is quickly eliminated, the cracking problem caused by pores is avoided, and the relative density and the mechanical property of the finished piece are greatly improved.

Description

Method for preparing nickel-based high-temperature alloy product by selective laser melting

The present application claims priority from the chinese patent application entitled "method for producing nickel-base superalloy articles by selective laser melting" filed by the chinese patent office on 11/08/2022, application No. 202210962400.5, which is incorporated herein by reference in its entirety.

Technical Field

The application relates to the field of laser additive manufacturing, in particular to a method for preparing a nickel-based superalloy product through selective laser melting.

Background

The laser additive manufacturing technology is a research hotspot because metal parts with complex shapes and high precision can be directly prepared. However, due to the complex dynamics between the laser process parameters, powder and melt pool, it is difficult to avoid randomly generated pores in the powder bed and melt pool during each layer scan, which are common defect features of many metallurgical processes. The pores formed by Selective Laser Melting (SLM) shaping of the nickel-based superalloy are closely related to laser process parameters, and no significant difference exists between nickel-based superalloys of different alloy compositions. Research reports show that the complex laser-powder-molten pool dynamic relation exists in the laser additive manufacturing process through high-fidelity simulation and synchrotron experiments, metal powder is easy to splash and the molten pool is easy to be unstable, a lockhole mode is triggered, and a pore defect is formed. In nickel-base superalloys, keyhole-induced porosity is difficult to avoid due to the large melting range formed by the large number of alloying elements.

Exploratory studies have been conducted at home and abroad to address the above problems. It is studied to introduce nano TiC during SLM shaping of Ren 104 ni-based superalloy, the interaction between laser and powder bed is changed from keyhole mode to conduction mode, reducing the porosity by 67.5%. In addition, defects such as pores and cracks generated in the SLM forming process can be eliminated by adopting hot isostatic pressing post-treatment. However, these processes are relatively complicated and require additional introduction of other materials or additional processing steps.

Disclosure of Invention

In view of the above, an object of the present application is to provide a method for preparing a nickel-based superalloy product by selective laser melting, so that the method can simply, conveniently and effectively inhibit formation of pores in the SLM forming process of the nickel-based superalloy product, simultaneously rapidly eliminate residual stress, avoid the cracking problem caused by the pores, and greatly improve the relative density and mechanical properties of the product.

To solve the above technical problem/achieve the above object or at least partially solve the above technical problem/achieve the above object, the present application provides a method for producing a nickel-base superalloy product by selective laser melting, comprising:

step 1, establishing a three-dimensional model according to the shape of a pre-prepared product, slicing and layering the three-dimensional model by using software, and introducing the three-dimensional model into a selective laser melting equipment system;

step 2, laying nickel-based superalloy powder on a forming substrate, and scanning the nickel-based superalloy powder at a first scanning speed by using a selective laser melting device and a laser beam with first power; then, scanning again by adopting the laser beam with the second power and the second scanning speed to obtain a forming layer;

wherein the first power is less than the second power, and the first scanning speed is less than the second scanning speed; the second power is 150-400W; the second scanning speed is 600-1200mm/s;

and 3, repeating the step 2 to stack the obtained forming layers layer by layer until the nickel-based superalloy product with a three-dimensional model structure is formed.

In certain embodiments of the present application, the second power is 225W; the second scanning speed is 900mm/s. In other embodiments of the present application, the three-dimensional model may be created by CAD.

Aiming at the defect that a nickel-based superalloy product prepared by an SLM is easy to generate pores, cracks and the like, the method firstly provides that a powder layer is firstly scanned by adopting a low-power laser and a slower scanning speed, the powder layer is preheated, the powder particles are pre-connected, and meanwhile, the thermal gradient between the powder layer and a workpiece is obviously reduced; and then fused and formed by a high-power laser beam with a higher scanning speed than that of the first scanning to obtain a formed layer.

Optionally, the first power is 30-100W and the first scanning speed is 100-500mm/s. In certain embodiments of the present application, the first power is 60W and the first scanning speed is 300mm/s.

Optionally, the nickel-based superalloy powder is spherical powder with a particle size of 15-53 μm.

Optionally, the nickel-base superalloy powder is Ren 104 nickel-base superalloy powder or IN718 nickel-base superalloy powder. In some embodiments of the present application, the composition of the Ren 104 nickel-base superalloy is as follows: 20.6% of Co,13% of Al, 3.4% of Al,3.9% of Ti,3.8% of Mo,2.1% of W,2.4% of Ta,0.9% of Nb,0.05% of Zr,0.03% of B,0.04% of C, the balance of Ni; IN certain embodiments of the present application, the IN718 nickel-base superalloy has a composition: 18.9% of Fe,18.9% of Cr,5.06% of Nb,3.07% of Mo,0.97% of Ti,0.58% of Al,0.09% of Co,0.03% of Ta,0.03% of V,0.12% of Si,0.03% of C, and the balance of Ni.

To partly select laser melting equipment at present and can only formulate a set of parameter to a three-dimensional model, cause the problem that can't realize this application to realizing secondary laser scanning to same powder bed, in some embodiments of this application, step 1 includes: establishing two identical three-dimensional models according to the shape of a pre-prepared product, slicing and layering the two identical three-dimensional models by using software, and positioning the two identical three-dimensional models at the same position on a forming substrate after the two identical three-dimensional models are introduced into a selective laser melting equipment system to ensure that the laser melting areas of the two identical three-dimensional models are completely overlapped; the two identical three-dimensional models are respectively provided with two sets of different scanning parameters of a first power and a first scanning speed, and a second power and a second scanning speed.

According to the method, two workpiece three-dimensional models with the same size are overlapped in the system, so that the melting areas of the workpiece three-dimensional models on a forming substrate are completely overlapped, different laser scanning parameters are set for the two three-dimensional models respectively, and after laser scanning is completed for one three-dimensional model, laser scanning is started for the other three-dimensional model immediately, so that the purpose of performing secondary laser scanning on the powder layer of the three-dimensional model with the shape is achieved, the problem that secondary scanning cannot be achieved by single-beam laser of the existing equipment is solved, the existing equipment does not need to be changed, any equipment does not need to be added, and the method is simple, convenient and effective.

Additionally, in certain embodiments of the present application, drying the nickel-base superalloy powder and preheating the forming substrate prior to laying the nickel-base superalloy powder on the forming substrate is also included.

In certain embodiments of the present application, preheating the shaped substrate is heating the shaped substrate to 100-300 ℃. In some other embodiments of the present application, the preheating the shaped substrate is heating the shaped substrate to 200 deg.C

In some embodiments of the present application, the drying the nickel-based superalloy powder is drying the nickel-based superalloy powder in a vacuum drying oven at 90-120 ℃ for 12-48 hours; in some other embodiments of the present application, the drying the nickel-based superalloy powder is drying the nickel-based superalloy powder in a vacuum oven at 105 ℃ for 24 hours.

In some embodiments of the present application, the powder layer of the nickel-base superalloy powder laid on the forming substrate has a thickness of 30-50 μm; in some further embodiments of the present application, the thickness of the powder layer is 30 μm, 40 μm or 50 μm.

In certain embodiments of the present application, the laser melting process requires an inert gas atmosphere, which may be selected from inert gases having an oxygen content of less than 0.0001wt%, such as argon.

According to the technical scheme, the method for preparing the nickel-based high-temperature alloy product through selective laser melting is provided, the nickel-based high-temperature alloy powder can be subjected to preheating treatment in the SLM preparation process, splashing of metal powder and instability of a molten pool are avoided, thermal stress is reduced, generation of pores and cracks is inhibited, and relative density and mechanical properties of a workpiece are greatly improved.

Drawings

FIG. 1 is a schematic flow diagram of a method described herein;

FIG. 2 shows an OM structure image of a Ren 104 nickel-base superalloy product prepared according to the present application;

FIG. 3 shows an SEM image of the microstructure of a product of Ren 104 nickel-base superalloy prepared according to the present application;

FIG. 4 is a microstructure OM image of a Ren 104 alloy prepared by the laser additive manufacturing technology of the existing 'difficult-to-weld' nickel-based superalloy modified by the method of the application;

FIG. 5 shows an OM texture image of a Ren 104 nickel-base superalloy article prepared in comparative example 1;

FIG. 6 shows the OM texture image of the Ren 104 nickel-base superalloy article prepared in comparative example 2.

Detailed Description

The application discloses a method for preparing a nickel-based superalloy product by selective laser melting, and a person skilled in the art can appropriately improve process parameters by referring to the content. It is expressly intended that all such similar substitutes and modifications which are obvious to those skilled in the art are deemed to be incorporated herein by reference. While the methods described herein have been described in terms of preferred embodiments, it will be apparent to those of ordinary skill in the art that variations or modifications in the methods described herein, as well as suitable variations and combinations, may be made to implement and use the techniques of the present application without departing from the content, spirit and scope of the application. It should be apparent that the described embodiments are only some of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It is noted that, in this document, relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element. Meanwhile, the embodiments and features in the embodiments may be combined with each other in the present application without conflict.

The application particularly provides a method for preparing a nickel-based superalloy product by selective laser melting, which comprises the following steps:

establishing a three-dimensional CAD model on a computer according to the shape of the nickel-based superalloy product; layering the model slices by using software, and guiding the layered model slices into a system of selective laser melting equipment; firstly, drying nickel-based high-temperature alloy powder in a vacuum drying oven at 105 ℃ for 24 hours, simultaneously heating a formed substrate to 100-300 ℃, then filling the nickel-based high-temperature alloy powder into a powder supply cylinder, spreading the powder with the thickness of 30-50 mu m, and introducing inert gas into a working cavity until the oxygen content is lower than 100ppm; the forming substrate material may be selected from stainless steel or nickel-based alloys.

The inert gas should be argon with a purity of 99.99wt%, wherein the oxygen content is less than 0.0001wt%.

Firstly, scanning the paved nickel-based superalloy powder at a scanning speed of V1 by adopting a laser beam with P1 power through a numerical control system, and preheating a powder layer to pre-connect powder particles; then, fusing and forming the powder layer by adopting a laser with P2 power and a scanning speed of V2 to obtain a first formed layer; and then, scanning and preheating the powder layer for the first time by adopting P1 power and V1 speed, scanning and forming for the second time by adopting laser of P2 power and V2 scanning speed, and overlapping layer by layer until a three-dimensional part is formed.

When each layer is required to be scanned, the first scanning speed V1 is less than the second scanning speed V2, and the first scanning power P1 is less than the second scanning power P2; the value range of the P1 is 30-100W; the value range of V1 is 100-500mm/s; the value range of the P2 is 150-400W; the value range of V2 is 600-1200mm/s.

The advantages and positive effects of the present application include at least the following aspects:

(1) The powder layer is scanned for the first time by adopting a low-power laser and a slower scanning speed, and is preheated, so that the powder particles are pre-connected, the splashing of metal powder and the instability of a molten pool are avoided, and the formation of pores is inhibited;

(2) The powder layer is preheated by adopting low-power laser, so that the thermal stress generated in the SLM forming process is reduced, and the cracking problem caused by pores is inhibited;

(3) The defect formation is inhibited in real time in the SLM forming process of the nickel-based superalloy, the relative density and the mechanical property of a printed piece are improved, and the hot isostatic pressing post-treatment is not needed;

(4) The method is also effective to the laser additive manufacturing technology of the nickel-based high-temperature alloy which is difficult to weld, reduces the cracking sensitivity, widens the process parameter window and inhibits the formation of pores and cracks;

(5) Aiming at the equipment which can not set different laser scanning parameters for the same three-dimensional model, two product models with the same size can be overlapped and placed, and different scanning parameters are set for the two models respectively, so that secondary laser scanning is realized, the problem that the secondary scanning can not be realized by single laser beam of the existing equipment is solved, the equipment does not need to be changed, any equipment does not need to be added, and the adopted equipment and the method are simple.

In the comparative experiments provided in the present application, unless otherwise specified, the experimental conditions, materials, etc. were kept consistent for comparability, except for the differences indicated in the groups.

The selective laser melting method for producing nickel-base superalloy provided by the present application is further described below.

Example 1: exemplary preparation of Ren 104 Nickel-base superalloy articles

The matrix material is Ren 104 nickel-based superalloy spherical powder with the grain diameter of 15-53 mu m, and the Ren 104 nickel-based superalloy comprises the following components: 20.6% of Co,13% of Al, 3.4% of Al,3.9% of Ti,3.8% of Mo,2.1% of W,2.4% of Ta,0.9% of Nb,0.05% of Zr,0.03% of B,0.04% of C, the balance of Ni;

(1) Laser additive manufacturing pre-preparation

Establishing a three-dimensional CAD model on a computer according to the shape of the nickel-based superalloy product; slicing and layering the model by using software, and guiding the sliced and layered model into a system of selective laser melting equipment; firstly, drying nickel-based high-temperature alloy powder in a vacuum drying oven at 105 ℃ for 24 hours, simultaneously heating a formed substrate to 200 ℃, then filling the nickel-based high-temperature alloy powder into a powder supply cylinder and spreading the powder, wherein the thickness of the powder spreading layer is 30 mu m, and introducing inert gas into a working cavity until the oxygen content is lower than 100ppm; the substrate material is selected from stainless steel or nickel-based alloy.

The inert gas should be argon with a purity of 99.99wt%, wherein the oxygen content is less than 0.0001wt%.

(2) Laser additive manufacturing forming

Firstly, scanning the alloy powder in the step (1) by adopting a laser beam with 60W power at a scanning speed of 300mm/s through a numerical control system, and preheating a powder layer to pre-connect powder particles; then, fusing and forming the powder layer by adopting a 225W laser and a scanning speed of 900mm/s to obtain a first forming layer; and then, scanning and preheating the powder layer for the first time by adopting 60W power and 300mm/s speed, scanning and forming for the second time by adopting 225W power laser and 900mm/s scanning speed, and overlapping layer by layer until a three-dimensional part is formed.

Fig. 1 is a schematic diagram of laser double scanning in a selective laser melting forming process.

Fig. 2 is a structural image of a Ren 104 nickel-based superalloy OM prepared in this embodiment, which shows that the shape of a molten pool of the Ren 104 nickel-based superalloy is observed, the structure is compact, and defects such as pores and cracks are not found.

Fig. 3 is an SEM image of the microstructure of Ren 104 ni-based superalloy prepared in this example, and it was found that preheating the powder layer with a single scan of a lower energy laser did not change the microstructure of the printed article.

The Ren 104 nickel-base superalloy sample prepared in the embodiment has the advantages of 99.4% of relative density, 1052MPa of yield strength and 1375MPa of tensile strength and 13.8% of elongation.

In addition, on the basis of the process, ren 104 nickel-based superalloy sample preparation is carried out according to the parameters set in the table 1, and the results are the same;

TABLE 1

Example 2: exemplary preparation of IN718 Nickel-base superalloy articles

Method referring to example 1 (non table 1 parameters), the IN718 nickel-base superalloy composition was: 18.9% of Fe,18.9% of Cr,5.06% of Nb,3.07% of Mo,0.97% of Ti,0.58% of Al,0.09% of Co,0.03% of Ta,0.03% of V,0.12% of Si,0.03% of C, and the balance of Ni.

The prepared IN718 nickel-based high-temperature alloy product has a compact structure and is free of defects. The IN718 alloy sample prepared IN this example was tested to have a relative density of 99.8%, a yield strength and tensile strength of 1033MPa and 1357MPa, respectively, and an elongation of 25.3%.

Example 3: improvement of laser additive manufacturing technology of existing 'difficult-to-weld' nickel-based superalloy

In the Chinese patent CN108941560A comparative example 1, a subarea scanning melting strategy is not carried out according to the patent, other parameters are kept consistent, and the result shows that cracks with various sizes exist in the formed part, and the cracks still exist after post-treatment; the relative densities before and after post-treatment (stress relief annealing + SPS) are respectively 98.12% and 99.02%, and the room-temperature mechanical properties are respectively 751MPa and 916MPa.

In this regard, with reference to the embodiment of example 1 (not parameters in table 1), the process parameters are changed from one scan to two scans, except that the parameters of the second laser scan are the specific parameters of the SLM process in comparative example 1 as described above: the laser power is 225W, the spot diameter is 0.12mm, the scanning speed is 600mm/s, the spot diameter is 0.12mm, and a partition strategy is not adopted.

Fig. 4 is a microstructure OM image of the prepared Ren 104 alloy, and the prepared sample has a compact structure, and only a small amount of micropores can be observed. Through detection, the prepared Ren 104 alloy has the relative density of 99.3 percent, the room-temperature yield strength of 981MPa, the tensile strength of 1271MPa and the elongation of 12.5 percent.

Compared with the relative density and the mechanical property of CN108941560A in comparative example 1, the 3D printing process parameters of CN108941560A in comparative example 1, which have the most serious cracking and the worst product performance, are adopted for secondary scanning forming, so that a product with high quality, no obvious defect and excellent mechanical property can be prepared, and the fact that the low-energy-density laser is adopted for primary scanning preheating treatment on a powder layer in the application can widen the window of a laser additive manufacturing process is shown.

Comparative example 1: preparation of Ren 104 nickel-base superalloy products without first scanning and preheating by laser

The difference from the solution of example 1 (parameters not shown in table 1) is that the laser additive manufacturing process in (2) does not perform laser first scanning preheating on the powder layer, and the other steps are the same as those in example 1.

FIG. 5 is an OM texture image of a Ren 104 nickel-base superalloy article prepared in comparative example 1. It was found that the Ren 104 nickel-base superalloy articles that were not laser twice-scanned in-situ heat treated exhibited more porosity.

The Ren 104 nickel-base superalloy prepared in comparative example 1 was tested to have a relative density of 98.5%, yield and tensile strengths of 779MPa and 928MPa, respectively, and an elongation of 3.8%.

Comparative example 2: preparing Ren 104 nickel-base superalloy products with high power and high speed by first laser scanning

Different from the embodiment 1 (parameters not shown in table 1), in the laser additive manufacturing process in (2), the powder layer is scanned for the first time by using a high-power and high-speed laser, and the process parameters are as follows: laser power 150W and laser scanning rate 700mm/s, the others being the same as in example 1.

FIG. 6 is an OM image of a Ren 104 nickel-base superalloy article prepared in comparative example 2. It has been found that the first scan of the powder bed with a high power, high velocity laser also causes powder splatter and bath instability, creating more porosity and increasing thermal stress build-up and cracking.

According to the test, the Ren 104 nickel-base superalloy prepared in the comparative example 2 has the relative density of 97.3%, the yield strength and the tensile strength of 935MPa and 1104MPa respectively, and the elongation of 2.6%.

Comparative example 3: the second laser scanning is low-power and low-speed preparation of the Ren 104 nickel-based superalloy product

Different from the solution of example 1 (parameters not shown in table 1), in the laser additive manufacturing process of (2), the powder layer is subjected to second scanning forming by using a low-power and low-speed laser, and the process parameters are as follows: laser power 120W and laser scanning rate 500mm/s, the others being the same as in example 1.

It can be found that although the powder layer is scanned twice by the low-energy-density laser, the powder can be prevented from splashing, but the energy of the laser for the second time is obviously insufficient, so that the melting forming cannot be completed, and the printing fails.

The previous description is only an example of the present application, and is provided to enable any person skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (9)

1. A method for preparing a nickel-based superalloy product by selective laser melting is characterized by comprising the following steps:

step 1, establishing a three-dimensional model according to the shape of a pre-prepared product, slicing and layering the three-dimensional model by using software, and introducing the three-dimensional model into a selective laser melting equipment system;

step 2, laying nickel-based superalloy powder on a forming substrate, and scanning the nickel-based superalloy powder at a first scanning speed by using a selective laser melting device and a laser beam with first power; then, scanning again by adopting the laser beam with the second power and the second scanning speed to obtain a forming layer;

wherein the first power is less than the second power, and the first scanning speed is less than the second scanning speed; the second power is 150-400W; the second scanning speed is 600-1200mm/s;

and 3, repeating the step 2 to stack the obtained forming layers layer by layer until the nickel-based superalloy product with a three-dimensional model structure is formed.

2. The method of claim 1, wherein the second power is 225W; the second scanning speed is 900mm/s.

3. The method of claim 1, wherein step 1 comprises: establishing two completely identical three-dimensional models according to the shape of a pre-prepared product, slicing and layering the two completely identical three-dimensional models by using software, and positioning the two completely identical three-dimensional models at the same position on a forming substrate after the two completely identical three-dimensional models are introduced into a selective laser melting equipment system so that laser melting areas of the two completely identical three-dimensional models are completely overlapped;

the two identical three-dimensional models respectively have two different sets of scanning parameters, namely a first power and a first scanning speed, and a second power and a second scanning speed.

4. The method according to claim 1, wherein the first power is 30-100W and the first scanning speed is 100-500mm/s.

5. The method according to claim 4, wherein the first power is 60W and the first scanning speed is 300mm/s.

6. The method of claim 1, wherein the nickel-base superalloy powder is Ren 104 nickel-base superalloy powder or IN718 nickel-base superalloy powder.

7. The method of claim 1, wherein the nickel-base superalloy powder has a particle size of 15-53 μ ι η.

8. The method of any one of claims 1-6, further comprising drying the nickel-base superalloy powder and preheating the forming substrate prior to laying the nickel-base superalloy powder on the forming substrate.

9. The method of claim 8, wherein preheating the shaped substrate is heating the shaped substrate to a temperature of 100 ℃ to 300 ℃.

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