阅读说明：本技术 一种消除裂纹的增材制造方法 (Additive manufacturing method for eliminating cracks ) 是由 阚文斌 王玉庆 刘利 郭超 马旭龙 于 2021-08-12 设计创作，主要内容包括：本发明属于增材制造技术领域,公开了一种消除裂纹的增材制造方法,包括以下步骤：S1、铺设合金粉末以形成粉床；S2、对粉床表面进行初次扫描预热,并根据增材制造所用的合金粉末调整初次扫描预热的第一粉床参数,使得初次扫描预热后的粉床温度为940-1100℃；S3、对粉床进行扫描熔化,扫描熔化时电子束扫描速度为0.9-10m/s；S4、对扫描熔化后的粉床进行再次扫描预热,并根据增材制造所用的合金粉末调整再次扫描预热的第二粉床参数,使得再次扫描预热后的粉床温度为940-1100℃；S5、重复步骤S1-S4,直至所需的零件增材制造完成。通过上述方法,能够有效消除裂纹并减小对材料性能的制约。(The invention belongs to the technical field of additive manufacturing, and discloses an additive manufacturing method for eliminating cracks, which comprises the following steps: s1, laying alloy powder to form a powder bed; s2, carrying out primary scanning preheating on the surface of the powder bed, and adjusting the first powder bed parameter of the primary scanning preheating according to the alloy powder used for additive manufacturing, so that the powder bed temperature after the primary scanning preheating is 940-; s3, scanning and melting the powder bed, wherein the scanning speed of the electron beam is 0.9-10m/S during scanning and melting; s4, scanning and preheating the powder bed after scanning and melting again, and adjusting the parameters of the second powder bed after scanning and preheating again according to the alloy powder used for additive manufacturing, so that the temperature of the powder bed after scanning and preheating again is 940-; and S5, repeating the steps S1-S4 until the additive manufacturing of the required part is completed. By the method, the cracks can be effectively eliminated, and the restriction on the material performance is reduced.)

1. An additive manufacturing method for eliminating cracks is characterized by comprising the following steps:

s1, laying alloy powder to form a powder bed;

s2, carrying out primary scanning preheating on the surface of the powder bed, and adjusting the first powder bed parameter of the primary scanning preheating according to alloy powder used for additive manufacturing, so that the powder bed temperature after the primary scanning preheating is 940-1100 ℃;

s3, scanning and melting the powder bed, wherein the scanning speed of the electron beam is 0.9-10m/S during scanning and melting;

s4, carrying out secondary scanning preheating on the powder bed after scanning and melting, and adjusting the secondary scanning and preheating second powder bed parameters according to alloy powder used for additive manufacturing, so that the temperature of the powder bed after secondary scanning and preheating is 940-1100 ℃, wherein the second powder bed parameters and the first powder bed parameters respectively comprise the partition width, the electron beam rotation angle, the focusing bias current, the electron beam scanning speed, the beam size of the electron beam and the distance between two adjacent scanning lines during scanning and preheating;

and S5, repeating the steps S1-S4 until the additive manufacturing of the required part is completed.

2. The method according to claim 1, wherein a scanning direction of the electron beam is set to an X direction, and the part is disposed at an acute angle to the X direction.

3. The method of crack mitigating additive manufacturing of claim 2, wherein the part is positioned at a 45 ° angle to the X-direction.

4. The additive manufacturing method for eliminating cracks according to claim 1, wherein the width of the partition in the first powder bed parameter is 5-20mm, the rotation angle of the electron beam is 90 °, the focus bias current is 50-150mA, the scanning speed of the electron beam is 22-25m/s, the beam size of the electron beam is 20-38mA, and the distance between two adjacent scanning lines is 1-2 mm.

5. The additive manufacturing method for eliminating cracks according to claim 1, wherein the temperature fluctuation amplitude of the powder bed is between-20 ℃ and 20 ℃ by adjusting the second powder bed parameter when the second powder bed is subjected to the scanning preheating.

6. The additive manufacturing method for eliminating cracks according to claim 5, wherein the width of the partition in the second powder bed parameter is 5-20mm, the rotation angle of the electron beam is 90 °, the focus bias current is 50-150mA, the scanning speed of the electron beam is 22-25m/s, the beam current of the electron beam is 32-38mA, and the distance between two adjacent scanning lines is 1-2 mm.

Technical Field

The invention relates to the technical field of additive manufacturing, in particular to an additive manufacturing method for eliminating cracks.

Background

The unweldable or difficult-to-weld superalloy materials have crack problems in the traditional additive manufacturing process, and the types and causes of cracks are generally as follows: 1. through type cracking: cracks grow from the substrate and penetrate through the whole part, and the cracks of the type are caused mainly due to the residual stress existing in the additive manufacturing process; 2. healing type cracks: cracks grow from the substrate and then gradually heal along with the rise of the forming height, stress is increased rapidly mainly due to overlarge temperature gradient, and the temperature is stable along with the rise of the forming height, so that the cracks of the type occur; 3. random type cracking: cracks grow randomly and heal randomly, and element precipitation cracking is caused mainly because the temperature interval is higher than the crystal precipitation temperature during molding, so that the cracks of the type appear; 4. surface type cracking: the scanning length is too long due to the model structure, the temperature field difference is large, and the filling scanning speed parameters are not matched, so that cracks can be eliminated due to the interaction between layers in the electron beam additive manufacturing process, but when the electron beam additive manufacturing process reaches the tail end forming layer of the part, the influence of layer-by-layer scanning is reduced, and the cracks are generated within 1mm of the depth of the upper surface.

The generation of the cracks has great influence on the performance of the parts, the dislocation is basically started from the cracks, the generated cracks can be usually inhibited or eliminated only through a heat treatment process, and the cracks can be inhibited only through the alternative overlapping and forming of the hard-to-weld alloy and the weldable alloy in part of laser additive manufacturing, but the mode has great restriction on the performance of the materials. Therefore, there is a need for an additive manufacturing method that can effectively eliminate cracks and has little restriction on material properties.

Disclosure of Invention

The invention aims to provide an additive manufacturing method for eliminating cracks, which can effectively eliminate the cracks and reduce the restriction on material performance.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method of additive manufacturing that eliminates cracks, comprising the steps of:

s1, laying alloy powder to form a powder bed;

s2, carrying out primary scanning preheating on the surface of the powder bed, and adjusting the first powder bed parameter of the primary scanning preheating according to alloy powder used for additive manufacturing, so that the powder bed temperature after the primary scanning preheating is 940-1100 ℃;

s3, scanning and melting the powder bed, wherein the scanning speed of the electron beam is 0.9-10m/S during scanning and melting;

s4, carrying out secondary scanning preheating on the powder bed after scanning and melting, and adjusting the secondary scanning and preheating second powder bed parameters according to alloy powder used for additive manufacturing, so that the temperature of the powder bed after secondary scanning and preheating is 940-1100 ℃, wherein the second powder bed parameters and the first powder bed parameters respectively comprise the partition width, the electron beam rotation angle, the focusing bias current, the electron beam scanning speed, the beam size of the electron beam and the distance between two adjacent scanning lines during scanning and preheating;

and S5, repeating the steps S1-S4 until the additive manufacturing of the required part is completed.

Preferably, the scanning direction of the electron beam is set to an X direction, and the component is disposed at an acute angle to the X direction.

Preferably, the part and the X direction are arranged at an included angle of 45 degrees.

Preferably, the width of the partition in the first powder bed parameter is 5-20mm, the rotation angle of the electron beam is 90 degrees, the focusing bias current is 50-150mA, the scanning speed of the electron beam is 22-25m/s, the beam current of the electron beam is 20-38mA, and the distance between two adjacent scanning lines is 1-2 mm.

Preferably, when the second scanning preheating is carried out, the second powder bed parameter is adjusted, so that the temperature fluctuation amplitude of the powder bed is between-20 ℃ and 20 ℃.

Preferably, the width of the partition in the second powder bed parameter is 5-20mm, the rotation angle of the electron beam is 90 degrees, the focusing bias current is 50-150mA, the scanning speed of the electron beam is 22-25m/s, the beam current of the electron beam is 32-38mA, and the distance between two adjacent scanning lines is 1-2 mm.

The invention has the beneficial effects that: through scan preheating to the powder bed for the first time, can make alloy powder can not take place the overburning phenomenon, and reach the false sintering powder bed of a "box" state, stabilize and can not grow the blowing powder phenomenon, through scan preheating once more to the powder bed, can effectively maintain the powder bed temperature, reduce the fluctuation range of powder bed temperature, and then make the vibration material disk manufacturing process be in a stable state, reduce the probability of the part fracture of vibration material disk manufacturing.

Drawings

FIG. 1 is a flow chart of a crack mitigating additive manufacturing method provided by the present invention;

FIG. 2 is a schematic view of the placement of an additively manufactured part provided by the present invention;

FIG. 3 is a metallographic graph showing cracks in a part when the temperature of a powder bed is lower than 940 ℃ during scanning preheating according to the invention;

FIG. 4 is a metallographic graph showing the cracking behavior of a part when the powder bed temperature approaches 940 ℃ during preheating according to the invention;

FIG. 5 is a gold phase diagram of the crack condition of the part when the powder bed temperature is 940-1100 ℃ during scanning preheating according to the invention;

FIG. 6 is a metallographic image showing the cracking of a part when the scanning speed is less than 0.9m/s in the scanning melting process according to the present invention;

FIG. 7 is a gold phase diagram showing the cracking of the part at a scanning speed of 3m/s in the scanning pre-melting of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting of the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.

In the description of the present invention, unless expressly stated or limited otherwise, the terms "connected," "connected," and "fixed" are to be construed broadly, e.g., as meaning permanently connected, removably connected, or integral to one another; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.

In the description of the present embodiment, the terms "upper", "lower", "right", etc. are used in an orientation or positional relationship based on that shown in the drawings only for convenience of description and simplicity of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used only for descriptive purposes and are not intended to have a special meaning.

The invention provides an additive manufacturing method for eliminating cracks, which can reduce or even eliminate the cracks on parts when alloy parts are manufactured, so that the manufactured parts meet the requirements. But also is preferably applicable to the condition that the alloy material is a non-weldable or difficult-to-weld high-temperature alloy material, and the cracks in the additive manufacturing process can be effectively eliminated.

Specifically, as shown in fig. 1, the additive manufacturing method for eliminating cracks includes the following steps:

and S1, laying alloy powder to form a powder bed.

Namely, alloy powder is paved on a forming cylinder through a powder paving device to form a powder bed. The powder spreading device and the forming cylinder are both the structures of the additive manufacturing device in the prior art, and the description is omitted. In the present embodiment, the alloy powder is preferably a non-weldable or difficult-to-weld superalloy material, and the mass percentages of the element components contained in the alloy powder can be seen in the following table, and the sum of the mass percentages of other elements and Ni elements is 100%.

C	Cr	AL	Co	W	Mo
						≤0.1	3.8～16.8	3.4～6.2	7～9.5	5.5～9.5	1.4～2.5
Ti	Fe	Nb	Ta	B	Zr
						＜4.7	＜0.5	0.35～1.2	3.1～8.5	≤0.2	≤0.2
Mn	Si	S	P	Pb	As
						≤0.2	≤0.2	≤0.01	≤0.018	≤0.001	≤0.005
Sb	Bi	Mg	Ag	Sn	Cu
						≤0.002	≤0.0005	≤0.003	≤0.0005	≤0.002	≤0.1
o	N	H	Re	Hf	Ni
						≤0.0098	≤0.0015	≤0.001	1.6～2.93	0.05～0.17	BAL

S2, performing primary scanning preheating on the surface of the powder bed, and adjusting the first powder bed parameter of the primary scanning preheating according to the alloy powder used for additive manufacturing, so that the powder bed temperature after the primary scanning preheating is 940-1100 ℃.

That is, after the powder alloy is laid to form the powder bed at step S1, the surface of the powder bed is subjected to primary scanning preheating by the electron beam. Because the compositions of the alloy powders used are different, different scanning parameters, namely the first powder bed parameter of the step, need to be selected for different alloy powders. Through adjusting the parameters of the first powder bed according to different alloy powders, the alloy powders can not be over-sintered, so that a false sintering powder bed in a box state is achieved, and the phenomenon of powder blowing is stable and avoided.

In this step, the temperature of the powder bed after the primary scanning preheating is 940-. The non-weldable or difficult-to-weld high-temperature alloy aiming at different series can not crack and generate cracks only in the temperature range corresponding to the alloy correctly. Therefore, the occurrence of cracks can be effectively avoided through the setting of the temperature of the powder bed.

Furthermore, the first powder bed parameter of the step is preferably that the width of the partition is 5-20mm, the rotation angle of the electron beam is 90 degrees, the focusing bias current is 50-150mA, the scanning speed of the electron beam is 22-25m/s, the beam current of the electron beam is 20-38mA, and the distance between two adjacent scanning lines is 1-2 mm. Wherein: the partition width specifically refers to the distance of electron beams in the snakelike scanning direction of the powder bed preheating scanning line, and the partition width is 5-20mm, so that the heating balance in the whole preheating range can be kept. The electron beam rotation angle specifically refers to an angle of rotation of the electron beam after the electron beam is scanned to the end point along a preset scanning line, and the setting of the rotation angle can ensure that the scanning and the heating are uniform and stable. The focus bias current is a bias treatment for the electron beam in a focused state to prevent the alloy powder of the powder bed from melting due to energy concentration. The electron beam scanning speed is a speed at which the electron beam is moved for scanning.

Through the range setting of the first powder bed parameters, the temperature of the powder bed can be effectively ensured to be 940-1100 ℃, so that the purposes of avoiding powder blowing and reducing and eliminating cracks are achieved.

And S3, scanning and melting the powder bed, wherein the scanning speed of the electron beam is 0.9-10m/S during scanning and melting.

After the primary scanning preheating is completed in step S2, the additive manufacturing of the current part layer is started. Specifically, the electron beam is scanned and melted in a set area of the powder bed to form a required part layer. Preferably, the scanning speed of the electron beam during scanning melting is 0.9-10 m/s. Through the scanning speed setting, compared with the scanning speed in the prior art, the scanning speed is improved, the scanning time is reduced, the temperature difference from the scanning starting position to the scanning ending position is reduced, the stress is reduced, and the occurrence of cracks is reduced.

Taking the example of the powder material as IN738 nickel-based superalloy material, IN this step, when the scanning speed of the electron beam is less than 0.9m/s, as shown IN FIG. 6, it is obvious that fine cracks are generated on the surface of the part. When the scanning speed of the electron beam was increased to 3m/s, the surface of the part was dense and crack-free as shown in FIG. 7. Therefore, when the scanning speed of the electron beam is between 0.9 and 10m/s at the time of scanning melting, it is possible to effectively reduce the occurrence of cracks.

It should be noted that, in this embodiment, in order to better avoid the generation of cracks, the scanning direction of the electron beam is set to the X direction, and further, the part is set to form an acute angle with the X direction. That is, as shown in fig. 2, in the prior art, the direction of the molded part is parallel to the X direction (a in fig. 2 indicates the part), and at this time, the distance of electron beam scanning and melting is long, which further causes a large temperature difference between the front and the rear, uneven heating of the powder bed, which further causes a large residual stress and cracks. In this embodiment, through being the acute angle setting (B in fig. 2 shows the part) between part and the X direction, the fused distance of electron beam in a scanning can obviously diminish this moment, and the fused distance of scanning many times is close, has guaranteed that the scanning length of each scanning direction is close, though scanning area does not change, its heat affected zone is more concentrated, also does benefit to and reduces the difference in temperature, has just also avoided because of the longer big difference in temperature that produces of distance for it is more even to be heated, better suppression crackle. Meanwhile, the scanning width of the electron beam can be improved due to the change of the direction of the part, and the heating is more uniform. Preferably, the part and the X direction are arranged at an included angle of 45 degrees.

S4, scanning and preheating the powder bed after scanning and melting, and adjusting the parameters of the second powder bed after scanning and preheating according to the alloy powder used for additive manufacturing, so that the temperature of the powder bed after scanning and preheating is 940-1100 ℃.

After scanning and melting are finished, the electron beam is used for scanning and preheating again, and specifically, different second powder bed parameters are selected for scanning and preheating again according to different adjustment of alloy powder. Through the second powder bed parameter, the temperature of the powder bed can be effectively maintained, the fluctuation range of the temperature of the powder bed is reduced, the additive manufacturing process is further in a stable state, and the cracking probability of the additive manufactured part is reduced.

In this step, the preheated powder bed temperature is again scanned at 940-. The non-weldable or difficult-to-weld high-temperature alloy aiming at different series can not crack and generate cracks only in the temperature range corresponding to the alloy correctly. Therefore, the occurrence of cracks can be effectively avoided through the setting of the temperature of the powder bed. And the temperature of the powder bed is set, so that the fluctuation range of the temperature of the powder bed can be ensured to be between-20 ℃ and 20 ℃. In addition, through the mutual cooperation of the secondary scanning preheating in the step and the primary scanning preheating in the step S2, the temperature in the forming chamber is always in a balanced state in the whole additive manufacturing process, and the additive manufacturing is ensured to be smoothly carried out.

In the step, the parameters of the second powder bed are preferably that the width of the partition is 5-20mm, the rotation angle of the electron beam is 90 degrees, the focusing bias current is 50-150mA, the scanning speed of the electron beam is 22-25m/s, the beam current of the electron beam is 32-38mA, and the distance between two adjacent scanning lines is 1-2 mm.

It should be noted that, in this embodiment, the temperature of the powder bed after the preheating by the initial scanning and the temperature of the powder bed after the preheating by the secondary scanning are both set to 940-. Taking the example of the powder material as IN738 nickel-base superalloy, as shown IN FIG. 3, when the powder bed temperature during the scanning preheating is lower than 940 ℃, the part surface is seen to have obvious cracks, and when the powder bed temperature during the scanning preheating is increased to be close to 940 ℃, as shown IN FIG. 4, the part surface cracks are obviously reduced although existing. When the temperature of the powder bed is 940-1100 ℃ during scanning preheating, as shown in FIG. 5, cracks are not formed on the surface of the part. Therefore, when the temperature of the powder bed after primary scanning preheating and the temperature of the powder bed after secondary scanning preheating are between 940-1100 ℃, cracks can not appear, and the forming quality and the yield of parts are effectively improved.

And S5, repeating the steps S1-S4 until the additive manufacturing of the required part is completed.

In this embodiment, it should be noted that, among the adjustment of the powder bed parameters in steps S2 and S4, the adjustment of the electron beam scanning melting speed in step S3, and the angle setting of the part, only one of them may be changed, or all the changes may be changed as needed, specifically, the corresponding scheme is selected according to the different components of the alloy powder.

It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Numerous obvious variations, adaptations and substitutions will occur to those skilled in the art without departing from the scope of the invention. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.