A forming method for a brittle alloy vane type part and application thereof

Abstract

The application provides a forming method of an easy-cracking alloy blade part and application, and relates to the technical field of metal material processing. Specifically, a three-dimensional model of a blade part to be formed is constructed, and a plurality of Chinese character support structures are preset in the inner cavity of the three-dimensional model of the blade part; a substrate for selective laser melting forming and an outer blade support structure are arranged, and then selective laser melting forming is performed to obtain a to-be-processed piece; stress relief heat treatment is performed on the to-be-processed piece, and then the substrate and the outer blade support structure are removed to obtain a blade precursor; and the blade precursor is subjected to forming post-heat treatment to obtain a blade part. Based on the structural characteristics of the blade part and the characteristics of the easy-cracking alloy material, the defects that the blade is prone to cracking or deformation during selective laser melting forming of the easy-cracking alloy are effectively solved, and the application has a good application prospect.

Description

Technical Field

[0001] This invention relates to the field of metal material processing technology, and more specifically, to a forming method and application of easily cracked alloy blade-like parts. Background Technology

[0002] K447 alloy is a crack-prone material. During laser forming and subsequent heat treatment, due to material and thermal stress, this alloy carries a significant risk of cracking. Furthermore, blade-like parts have complex airfoil structures and often have numerous film cooling pores on their surfaces, resulting in high structural stress. Therefore, using the crack-prone K447 alloy and selective laser melting to prepare blade-like parts with high structural stress exacerbates the cracking tendency and increases the difficulty of shape control.

[0003] Conventional solutions for controlling the deformation of blade-like parts typically involve adding several strong and weak supports to the outside of the part to resist deformation during selective laser melting (SLM) forming and subsequent heat treatment. The drawbacks of this method are: while deformation during SLM forming can be well controlled, deformation during subsequent heat treatment cannot be completely controlled. On the one hand, if the outer supports are too strong, the part's deformation tendency may be inhibited by the strong support forces during heat treatment, leading to stress release through cracking in weaker areas. On the other hand, if the outer supports are too weak, the concave deformation of the part cannot be well controlled during heat treatment, and this concave deformation may even worsen after polishing. Furthermore, when blade-like parts have internal cavities, external supports alone cannot control the concave deformation during heat treatment. Therefore, a comprehensive design and improvement of the shape control support scheme for easily cracked alloy blade parts is needed, taking into account the structural characteristics of the blade-like parts and the phase transformation stress of the material during heat treatment.

[0004] Furthermore, the challenges in shape control for double-layer blade-type parts also include deformation control of the double-walled cavity structure. Previous methods using only external support for shape control could not completely prevent localized cracking during heat treatment. Therefore, given this situation, it is necessary to adjust the heat treatment process to control the slow release and complete elimination of stress, thereby achieving a balance between internal and external stresses during heat treatment and preventing localized cracking.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a forming method for parts of alloy blades prone to cracking. Aiming at the technical problem that alloy materials prone to cracking are extremely prone to deformation or cracking during the process of selective laser melting to prepare complex blade parts, the present invention designs a suitable new forming process plan.

[0007] The second object of the present invention is to provide a kind of blade parts.

[0008] The third object of the present invention is to provide a preparation method for blades.

[0009] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted: A forming method for parts of alloy blades prone to cracking, comprising the following steps: S1. Construct a three-dimensional model of the blade parts to be formed, and preset a number of cross-shaped support structures in the inner cavity of the three-dimensional model of the blade parts; S2. Set a substrate and an outer support structure for the blade for selective laser melting forming, and then perform selective laser melting forming to obtain a workpiece to be processed; S3. Perform stress relief heat treatment on the workpiece to be processed, and then remove the substrate and the outer support structure of the blade to obtain a blade precursor; S4. Perform post-forming heat treatment on the blade precursor to obtain blade parts.

[0010] In one embodiment, the monomer of the cross-shaped support structure is a hollow cube structure with a cross-shaped cross-section; and a number of the cross-shaped support structures are distributed in an array.

[0011] In one embodiment, for the monomer of the cross-shaped support structure, the length and width of the cross-shaped cross-section are independently 10 mm to 50 mm.

[0012] In one embodiment, for the monomer of the cross-shaped support structure, the width of any entity on the cross-shaped cross-section is 0.8 mm to 2 mm.

[0013] In one embodiment, the inner cavity chamfer of the blade parts is 0.8.

[0014] In one embodiment, the material of the blade parts includes at least one of IN718C, DZ411, K447, Ti-48Al-2Cr-2Nb, AlSi10Mg, and preferably K447.

[0015] In one embodiment, the stress relief heat treatment is carried out in a protective gas environment, the temperature is 900 °C to 1050 °C, and the duration is 1 h to 4 h.

[0016] In one embodiment, the post-forming heat treatment includes: First, raise the temperature to 550℃~600℃ and hold for 8h~10h. Then, raise the temperature to 1070℃~1100℃ at a rate of 15℃ / min~25℃ / min and hold for 4h~8h. Next, lower the temperature to 850℃~880℃ at a rate of 20℃ / min~30℃ / min and hold for 20h~24h. Finally, cool the temperature to 20℃~30℃ at a rate of 150℃ / min~200℃ / min.

[0017] A blade-like part is prepared using the forming method described above.

[0018] A method for preparing a blade, comprising the aforementioned forming method.

[0019] This invention, based on the structural characteristics of blade-like parts and the properties of easily cracked alloy materials, designs a suitable forming support scheme, forming process route, and heat treatment regime, thus proposing a forming process scheme suitable for additive manufacturing of easily cracked alloy blade-like parts to control deformation and cracking. Compared with the prior art, the beneficial effects of this invention are: (1) Based on the conventional forming support scheme, this invention adds a cross-shaped support structure of appropriate height and type to the inner cavity of the blade-type part according to the stress distribution of the blade-type part structure, so as to resist and balance the stress of the external support and avoid deformation and cracking of the part during the subsequent heat treatment process.

[0020] (2) Based on the conventional heat treatment system, this invention adjusts the heat treatment system and adds multiple steps based on the structural characteristics of double-layer blade-type parts and the stress of alloy materials. This is used to control the slow release of stress and achieve the complete elimination of residual stress, thereby avoiding the risk of local cracking of parts during the heat treatment process.

[0021] (3) Based on the conventional forming process route, this invention adjusts the support state of blade-type parts in different heat treatment stages based on the phase transformation stress of K447 easily cracked alloy in different heat treatment stages, so as to avoid cracking and deformation caused by uneven stress in the inner cavity and surface of blade-type parts during heat treatment. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0023] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0024] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0025] This invention combines the structure of blade-like parts with the characteristics of easily cracked alloy materials, and designs a suitable type of internal cavity support, a suitable process route, and a heat treatment regime to balance the internal and external stresses of easily cracked alloy blade-like parts during selective laser melting forming and subsequent heat treatment stages. It controls the deformation and cracking of easily cracked alloy blade-like parts during selective laser melting forming and subsequent heat treatment stages, and provides a forming process scheme suitable for additive manufacturing of easily cracked alloy blade-like parts to control deformation or cracking.

[0026] The method for forming easily cracked alloy blade-like parts provided in the first aspect of the present invention specifically includes the following steps: S1. Construct a three-dimensional model of the blade-like part to be formed, and pre-set several cross-shaped support structures in the inner cavity of the three-dimensional model of the blade-like part. S2. Set up a substrate and blade external support structure for selective laser melting forming, and then perform selective laser melting forming to obtain the part to be processed; S3. Perform stress-relieving heat treatment on the workpiece to be processed, and then remove the substrate and the outer support structure of the blade to obtain the blade precursor; S4. The blade precursor is formed and then heat-treated to obtain a blade-type part.

[0027] It can be understood that in steps S1 - S2 of the present invention, based on the conventional external support design, considering the stress distribution of the blade - like part structure and the characteristics of the crack - prone alloy material, specific features such as the type, distribution position, height, width, and chamfer of the cross - shaped supports in the blade inner cavity are designed to avoid cracking of the cross - shaped supports in the inner cavity during the laser forming process.

[0028] It can be understood that in steps S1 - S2 of the present invention, on the one hand, based on the stress distribution of the blade - like part structure, a cross - shaped support structure with an appropriate height should be added to the inner cavity of the blade - like part to resist and balance the stress of the external support; on the other hand, based on the stress condition of the crack - prone alloy material, the distribution position and strength of the external solid support structure are reasonably designed to disperse and conduct the stress on the part body. After comprehensively considering the above two aspects, a forming support scheme for the blade - like parts made of crack - prone alloy materials is designed synergistically, and then selective laser melting forming is carried out.

[0029] As a preferred implementation manner, the monomer of the cross - shaped support structure is a cubic structure with a cross - shaped cross - section, and a number of the cross - shaped support structures are distributed in an array. It can be understood that in the monomer of the cross - shaped support structure, there are entities presenting a cross and the entity of the outer frame of the cross, and the non - cross part inside the monomer is designed as a hollow.

[0030] As a more preferred implementation manner, for the monomer of the cross - shaped support structure, the length and width of the cross - shaped cross - section are independently 10 mm - 50 mm, including but not limited to any one or any numerical range composed of any two of 10, 15, 20, 25, 30, 35, 40, 45, 50 (mm); and in some implementation manners, the cross - shaped cross - section is a square, that is, the length and width are equal.

[0031] As a more preferred implementation manner, for the monomer of the cross - shaped support structure, the width of any entity on the cross - shaped cross - section is 0.8 mm - 2 mm, including but not limited to any one or any numerical range composed of any two of 0.8, 0.9, 1, 1.1, 1.2, 1.4, 1.5, 1.6, 1.8, 1.9, 2 (mm), that is, it can be understood that the width of any line in the cross or the outer frame of the cross is limited to the above parameter range.

[0032] As a preferred implementation manner, for the overall configuration of a number of the cross - shaped support structures, features such as the total length, total width, total height, and distribution position are designed according to the part assembly application situation, and are not strictly limited in the present invention.

[0033] It is worth noting that, since the cross-shaped support structure is not removed in steps S3 to S4 of this invention, and the cross-shaped support structure is designed directly as part of the body of the blade-like part, on the one hand, the setting of the cross-shaped support structure cannot interfere with the original assembly and use of the blade-like part; on the other hand, the cross-shaped support structure is designed to be distributed near the assembly center shaft to enhance the rigidity of the body, resist shrinkage deformation, and ensure assembly and use.

[0034] In a preferred embodiment, the inner cavity chamfer of the blade-like part is 0.8. The chamfer is designed primarily to prevent cracking during the laser melting and forming process in the selected area and subsequent heat treatment, and to cooperate with the star-shaped support structure.

[0035] In one preferred embodiment, the material of the blade-like parts includes "crack-prone alloys," meaning that the concept of this invention is mainly applied to crack-prone alloy materials, but it can also be applied to conventional non-crack-prone alloy materials. In some embodiments, the material of the blade-like parts includes, but is not limited to, casting high-temperature alloys (such as IN718C, DZ411, K447), titanium-aluminum alloys (such as Ti-48Al-2Cr-2Nb), high-strength aluminum alloys (such as AlSi10Mg), etc.

[0036] It is understood that in step S3 of the present invention, the stress distribution of the blade-like part body changes after being freed from the substrate. At this time, based on the characteristics of the easily cracked alloy material and the structural stress distribution of the blade-like part, some of the external solid supports of the part body are removed, while the cross-shaped supports of the inner cavity of the blade-like part are retained to balance the forces inside and outside the blade-like part body. After the support is removed and polished, the subsequent heat treatment process S4 is carried out.

[0037] As a preferred embodiment, the selective laser melting forming includes the following steps: a) The substrate is preheated and placed into the forming cavity. After the cavity is evacuated, it is filled with an inert gas (such as high-purity argon) to maintain a low-oxygen environment. b) The selective laser melting equipment is operated, and the powder spreading device uniformly spreads a thin layer of metal powder (e.g., 20μm~60μm) on the substrate. A high-power laser beam selectively scans and melts the powder according to the slicing path to form the current layer cross section. c) The substrate is lowered by one layer thickness, and the powder spreading, scanning, and melting processes are repeated until the blade-like parts are accumulated layer by layer. d) The entire process is monitored in real time through molten pool monitoring and infrared thermal imaging. After forming, the blade-like parts need to be slowly cooled to room temperature in the forming cavity.

[0038] In a preferred embodiment, the thickness of the substrate is 3mm to 10mm.

[0039] In one preferred embodiment, the external support structure for the blade includes at least one of tree-like support, lattice support, and fractured contact points; in one embodiment, the tree-like support is used on the large overhanging surface of the blade, and the trunk diameter of the tree-like support is 0.5mm~1mm, and the branch diameter is 0.2mm~0.5mm; in one embodiment, the lattice support is used on the curved surface of the leaf base / leaf back, and the point spacing of the lattice support is 2mm~3mm, and the point diameter is 0.3mm~0.4mm; in one embodiment, the fractured contact points are used on the near-vertical surface, and the point diameter of the fractured contact points is 0.1mm~0.3mm.

[0040] In one preferred embodiment, the blade external support structure includes a clamping assembly; for ultra-large blades or extremely thin-walled blades, a detachable frame of the blade external support structure is designed and fixed by bolt connection or snap-fit.

[0041] In one preferred embodiment, the stress-relieving heat treatment is carried out in a protective gas environment at a temperature of 900℃~1050℃ for a duration of 1h~4h. In some embodiments, the temperature includes, but is not limited to, any one or any two of the following values: 900, 910, 920, 940, 950, 960, 980, 990, 1000, 1010, 1020, 1030, 1040, 1050 (℃), and the duration includes, but is not limited to, any one or any two of the following values: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 (h).

[0042] It is understood that the stress-relief heat treatment eliminates the macroscopic residual stress generated by the rapid solidification of SLM, preventing cracking or uncontrollable deformation of the parts during substrate cutting and support removal; at the same time, it preliminarily adjusts the microstructure to prepare for the subsequent final S4 heat treatment, but should not cause significant grain growth or large precipitation of harmful phases.

[0043] In a preferred embodiment, the "removal of the substrate and the outer support structure of the blade" includes the following steps performed in sequence: A) integral separation: wire cutting or band saw cutting; B) rough separation: using a fitter or angle grinder to remove the outer frame and solid support to avoid impacting the part body; C) fine separation: micro milling cutter or vibratory polishing to obtain a smooth blade surface.

[0044] In a preferred embodiment, the post-forming heat treatment includes the following steps: First, raise the temperature to 550℃~600℃ and hold for 8h~10h. Then, raise the temperature to 1070℃~1100℃ at a rate of 15℃ / min~25℃ / min and hold for 4h~8h. Next, lower the temperature to 850℃~880℃ at a rate of 20℃ / min~30℃ / min and hold for 20h~24h. Finally, cool the temperature to 20℃~30℃ (room temperature) at a rate of 150℃ / min~200℃ / min.

[0045] It is understood that the present invention strictly limits the use of the above-mentioned temperature control process. Compared with the conventional aging heat treatment process, the present invention adds two additional temperature steps to release and eliminate residual stress generated by the previous wire cutting, support removal, polishing and other actions, and to fully homogenize the structure.

[0046] In summary, under conventional forming support schemes, the internal cavity of blade-type parts lacks support, leading to the cracking of the solid support sheet on the part surface during laser selective melting forming, resulting in printing failure. After reinforcing the solid support sheet on the part surface, laser selective melting forming successfully completed, but after heat treatment, the blade profile of the part suffered severe deformation, approximately 2.0 mm, and localized cracking and deformation of the film cooling pores within the part's cavity. In contrast, with the technical solution of this invention, after laser selective melting forming, no cracks were observed in the cross-shaped support structure within the blade-type parts or on the part surface. After removing part of the support and applying a controlled aging heat treatment, no cracks were observed in the part's internal cavity or surface, the blade profile deformation was controlled to <0.25 mm, and no cracks were found in the film cooling pores after non-destructive testing.

[0047] A second aspect of the present invention is to provide a blade-like part, which is prepared by a forming method as described in the first aspect.

[0048] A third aspect of the present invention is to provide a method for preparing a blade, comprising the forming method as described in the first aspect.

[0049] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A forming method for easily cracked alloy blade-like parts, characterized in that, It includes the following steps: S1. Construct a three-dimensional model of the blade-like part to be formed, and preset several cross-shaped support structures in the inner cavity of the three-dimensional model of the blade-like part; S2. Set a substrate and an outer blade support structure for selective laser melting forming, and then perform selective laser melting forming to obtain a workpiece to be processed; S3. Perform stress relief heat treatment on the workpiece to be processed, and then remove the substrate and the outer blade support structure to obtain a blade precursor; S4. Perform post-forming heat treatment on the blade precursor to obtain a blade-like part.

2. The forming method according to claim 1, characterized in that, The monomer of the cross-shaped support structure is a hollow cube structure with a cross-shaped cross-section; and several of the cross-shaped support structures are distributed in an array.

3. The forming method according to claim 2, characterized in that, For the monomer of the cross-shaped support structure, the length and width of the cross-shaped cross-section are independently 10 mm to 50 mm.

4. The forming method according to claim 2, characterized in that, For the monomer of the cross-shaped support structure, the width of any entity on the cross-shaped cross-section is 0.8 mm to 2 mm.

5. The forming method according to claim 1, characterized in that, The inner cavity chamfer of the blade-like part is 0.

8.

6. The forming method according to claim 1, characterized in that, The material of the blade-like part includes at least one of IN718C, DZ411, K447, Ti-48Al-2Cr-2Nb, AlSi10Mg, and preferably K447.

7. The forming method according to claim 1, characterized in that, The stress relief heat treatment is carried out in a protective gas environment, the temperature is 900 °C to 1050 °C, and the duration is 1 h to 4 h.

8. The forming method according to claim 1, characterized in that, The post-forming heat treatment includes: First, heat up to 550 °C to 600 °C, hold for 8 h to 10 h, then heat up to 1070 °C to 1100 °C at a rate of 15 °C / min to 25 °C / min, hold for 4 h to 8 h, then cool down to 850 °C to 880 °C at a rate of 20 °C / min to 30 °C / min, hold for 20 h to 24 h, and finally cool down to 20 °C to 30 °C at a rate of 150 °C / min to 200 °C / min.

9. A blade-like part, characterized in that, It is prepared by using the forming method described in any one of claims 1 to 8.

10. A method for preparing a leaf, characterized in that, It includes the forming method described in any one of claims 1 to 8.