Method and apparatus for inhibiting crack defects in laser additive manufacturing of difficult-to-weld superalloys

Abstract

The present application relates to the technical field of additive manufacturing, and discloses a method and equipment for inhibiting crack defects of laser additive manufacturing of difficult-to-weld high-temperature alloy. When a first molten pool gradient is greater than a preset temperature gradient threshold, a composite laser spot can be used to melt a metal powder scanning area corresponding to each layered slice of a target part, a center spot is used to provide sufficient energy to melt the metal powder and form a stable molten pool, and an annular spot is used to preheat the periphery of the molten pool to adjust the temperature distribution of the molten pool. According to the molten pool center temperature and the molten pool radius generated by the center spot in the scanning area at a preset scanning speed, the second laser power required by the annular spot is determined, so as to meet the accurate control of the molten pool gradient and the cooling rate, so that the molten pool can be cooled more uniformly during the solidification process, and the crack and pore defects caused by the high temperature gradient and the high cooling rate are effectively reduced, and the crack problem of laser additive manufacturing of high-performance difficult-to-weld high-temperature alloy is solved.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and discloses a method and equipment for suppressing crack defects in difficult-to-weld high-temperature alloys manufactured by laser additive manufacturing. Background Technology

[0002] High-temperature alloys generally possess high strength, good resistance to oxidation and hot corrosion, excellent creep and fatigue resistance, and high reliability, making them widely used in the fabrication of hot-end components for advanced propulsion systems in aerospace, petrochemical, and other fields. The fabrication of complex high-temperature alloy components has become a key core technology in aerospace and other fields, but existing high-temperature alloy component fabrication processes such as forging, powder metallurgy, and casting all have certain limitations in the fabrication of complex components.

[0003] Laser Additive Manufacturing (LAM) technology utilizes the "discrete-stacking" principle to directly manufacture parts from digital models to physical objects, greatly improving design freedom and becoming one of the key manufacturing technologies for complex components. However, during the LAM process, metal powder undergoes a series of complex, highly non-equilibrium phase changes, including melting, solidification, vaporization, and solid-state phase transitions. Furthermore, the high temperature gradient, high cooling rate, and cyclic heating-cooling effect easily lead to large residual stresses and cracks within the printed parts, significantly increasing the risk of fatigue failure during service. Currently, only a very few high-temperature alloys with excellent weldability, such as IN718, IN625, and Hastelloy X, can be guaranteed to remain crack-free during LAM manufacturing, while alloys with poor weldability, such as CM247LC, IN939, and IN738LC, are highly prone to cracking during manufacturing.

[0004] Optimizing alloy composition is an effective way to fundamentally solve the cracking problem, but changes in alloy composition are usually accompanied by changes in alloy properties. Comprehensive characterization and evaluation are needed to clarify the overall performance of the optimized alloy, making short-term application in engineering difficult. Ultra-high temperature preheating or applying external fields such as magnetic fields or ultrasonic fields can also effectively suppress cracks, but these place higher and more difficult-to-achieve requirements on equipment, significantly extend the process chain and manufacturing time, and substantially increase production costs. Adjusting process parameters offers greater operability and economy, but process parameters based on conventional Gaussian light sources have very limited control over crack defects and are difficult to effectively suppress crack formation.

[0005] In the additive manufacturing of difficult-to-weld high-temperature alloys, strong non-equilibrium solidification behavior occurs. The high temperature gradient, high cooling rate, and cyclic heating-cooling effect lead to elemental segregation, phase transformation, and residual stress accumulation in the alloy, which can easily cause large residual stress, cracks, pores, and other process defects inside the component. For example, in the SLM forming process of high-temperature alloys, the high content of Al and Ti elements can easily lead to solidification segregation and γ+γ′ low-melting-point eutectic, which can easily cause solidification cracks and liquefaction cracks. At the same time, a large amount of γ′ phase precipitates during cooling, resulting in poor material plasticity and making strain failure cracking very easy. Summary of the Invention

[0006] The purpose of this invention is to provide a method and equipment for suppressing crack defects in laser additive manufacturing of difficult-to-weld high-temperature alloys. This method can achieve precise control of the molten pool gradient and cooling rate, enabling the molten pool to cool more uniformly during solidification. This effectively reduces defects such as cracks and porosity caused by high temperature gradients and high cooling rates, thus solving the problem of cracking in high-performance difficult-to-weld high-temperature alloys in laser additive manufacturing.

[0007] To achieve the above-mentioned technical effects, the technical solution adopted by the present invention is as follows:

[0008] Methods for suppressing crack defects in laser additive manufacturing of difficult-to-weld high-temperature alloys include:

[0009] Based on the arrangement and position of the target part in the forming chamber of the laser scanning forming equipment, the three-dimensional solid geometric model of the target part is sliced ​​in the vertical direction; the laser scanning forming equipment is used to form a composite laser spot for melting the metal powder scanning area corresponding to each slice of the target part, the composite laser spot including a central spot and an annular spot located on the outer periphery of the central spot;

[0010] Based on the performance parameters of the metal powder of the target part, the central spot parameters of the laser scanning forming equipment are determined, including the central spot radius and the first laser power of the central spot;

[0011] Based on the determined central spot parameters, the molten pool center temperature and molten pool radius of the scanning area of ​​the central spot at the preset scanning speed are obtained through experiments or simulation analysis, and the first molten pool gradient of the scanning area of ​​the central spot at the preset scanning speed is obtained based on the molten pool center temperature and molten pool radius analysis.

[0012] When the first molten pool gradient is greater than the preset temperature gradient threshold, the second laser power required for the annular spot is obtained by analyzing the molten pool center temperature of the laser scanning area of ​​a single layered slice under the central spot parameters, the designed outer diameter of the annular spot, and the layer thickness of the metal powder.

[0013] Following a bottom-up layered slicing structure, powder is sequentially laid layer by layer in the forming chamber. If the first molten pool gradient is greater than the preset temperature gradient threshold, the laser scanning forming equipment is controlled to generate a central spot with a first laser power and a corresponding annular spot with a second laser power, scanning and melting the metal powder at each layer processing position to complete the processing of the target part; otherwise, the central spot is generated solely with the first laser power to complete the processing of the target part.

[0014] Furthermore, the first molten pool gradient of the scanning region at the preset scanning speed of the central spot. ,in To obtain the center temperature of the molten pool in the scanning region of the central spot at a preset scanning speed, experimental or simulation analysis is conducted under the condition of the central spot parameters. The radius of the molten pool in the scanning area of ​​the center spot at a preset scanning speed is obtained through experimental or simulation analysis under the condition of the center spot parameters.

[0015] Furthermore, the second laser power of the annular spot is based on ,in The second laser power of the annular spot. The absorption rate of the metal powder material to the laser. The outer diameter of the annular light spot is designed as follows. Specific heat capacity of metal powder materials. The density of the metal powder material, The thickness of a single layer of metal powder. The scanning speed of the composite laser spot over the layup processing position. This is an empirical coefficient. The value range is 0.2 to 0.8. The temperature at the center of the molten pool in the laser scanning region of a single layered slice under the aforementioned center spot parameters. Room temperature.

[0016] Further, the metal powder is MarM247 alloy powder, wherein the MarM247 alloy powder contains 0.07-0.1 wt.% C, ≤0.06 wt.% Si, 8.0-8.7 wt.% Cr, 9-10 wt.% Co, 0.4-0.8 wt.% Mo, 0.005-0.02 wt.% Zr, 5.25-5.75 wt.% Al, ≤0.2 wt.% Fe, 9.5-10.5 wt.% W, ≤2.8-3.3 wt.% Ta, 1.3-1.6 wt.% Hf, 0.6-0.9 wt.% Ti, with the balance being Ni, and the MarM247 alloy powder has a particle size of 15-53 μm.

[0017] Furthermore, the laser power of the central spot is 200-220W, and the scanning speed is 900-950mm / s; the laser power of the annular spot is 100-150W, and the scanning speed is synchronized with that of the central spot.

[0018] To achieve the above-mentioned technical effects, the present invention provides equipment for suppressing crack defects in laser additive manufacturing of refractory high-temperature alloys, and for implementing the method for suppressing crack defects in laser additive manufacturing of refractory high-temperature alloys, characterized in that it includes:

[0019] The powder spreading system is used to spread high-temperature alloy powder layer by layer in a bottom-up, layered slicing structure;

[0020] The laser scanning system is used to generate a central spot with a first laser power and a corresponding annular spot with a second laser power, and to scan and melt the metal powder at each layup processing location layer by layer.

[0021] An atmosphere protection system is used to control the gas flow within the forming chamber and remove splashes.

[0022] Furthermore, the laser scanning system achieves continuous adjustment of the central spot diameter (50-160 μm) and the annular spot diameter (150-400 μm) through an electric beam expander, and the energy attenuation of the optical path system is ≤5%.

[0023] Furthermore, the atmosphere protection system adopts an airflow scheme with air intake on one side and air outlet on multiple sides, and the uniformity of air velocity on the printing surface is ≤±0.2m / s.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention determines the second laser power required for the annular spot based on the molten pool center temperature and molten pool radius generated by the central spot in the scanning area at a preset scanning speed, ensuring reasonable setting of the laser power of the central spot and the annular spot, thereby satisfying the precise control of the molten pool gradient and cooling rate, so that the molten pool can cool more uniformly during solidification, effectively reducing defects such as cracks and pores caused by high temperature gradient and high cooling rate, and solving the problem of cracking in high-performance difficult-to-weld high-temperature alloy laser additive manufacturing. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the method for suppressing crack defects in laser additive manufacturing of difficult-to-weld high-temperature alloys in the embodiments.

[0026] Figure 2 This is a schematic diagram of the composite laser spot structure in the embodiment;

[0027] Among them, 1. central light spot; 2. ring-shaped light spot. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings. However, this should not be construed as limiting the scope of the above-described subject matter of the present invention to the following embodiments; all technologies implemented based on the content of the present invention fall within the scope of the present invention.

[0029] Example

[0030] See Figure 1 , Figure 2 Methods for suppressing crack defects in laser additive manufacturing of difficult-to-weld high-temperature alloys include:

[0031] Based on the arrangement and position of the target part in the forming chamber of the laser scanning forming equipment, the three-dimensional solid geometric model of the target part is sliced ​​in the vertical direction; the laser scanning forming equipment is used to form a composite laser spot for melting the metal powder scanning area corresponding to each slice of the target part, the composite laser spot includes a central spot 1 and an annular spot 2 located on the outer periphery of the central spot 1;

[0032] Based on the performance parameters of the metal powder of the target part, the parameters of the center spot 1 of the laser scanning forming equipment are determined. The parameters of the center spot 1 include the radius of the center spot 1 and the first laser power of the center spot 1.

[0033] Based on the determined parameters of the central spot 1, the center temperature and radius of the molten pool in the scanning area of ​​the central spot 1 at the preset scanning speed are obtained by experiment or simulation analysis, and the first molten pool gradient in the scanning area of ​​the central spot 1 at the preset scanning speed is obtained by analyzing the center temperature and radius of the molten pool.

[0034] When the first molten pool gradient is greater than the preset temperature gradient threshold, the second laser power required for the annular spot 2 is obtained by analyzing the molten pool center temperature of the laser scanning area of ​​a single layered slice under the parameters of the central spot 1, the designed outer diameter of the annular spot 2, and the layer thickness of the metal powder.

[0035] According to the layered slicing structure from bottom to top, powder is laid layer by layer in the forming chamber. If the first molten pool gradient is greater than the preset temperature gradient threshold, the laser scanning forming equipment is controlled to generate a central spot 1 with the first laser power and a corresponding annular spot 2 with the second laser power. The metal powder at each layer processing position is scanned and melted layer by layer to complete the processing of the target part. Otherwise, the central spot is generated by the first laser power alone to complete the processing of the target part.

[0036] This patent addresses the problem of cracking in laser additive manufacturing of high-performance, difficult-to-weld high-temperature alloys by designing a composite laser spot, adjusting the temperature gradient of the molten pool after powder melting, controlling the temperature gradient and cooling rate, suppressing defects such as microcracks and pores in the forming process.

[0037] In this embodiment, the central laser spot 1 is mainly used to provide sufficient energy to melt the metal powder and form a stable molten pool, while the annular laser spot 2 preheats the area around the molten pool, thereby adjusting the temperature distribution of the molten pool and achieving precise control over the molten pool gradient and cooling rate. When the first molten pool gradient is less than or equal to a preset temperature gradient threshold, the central laser spot 1 can be used alone to generate the central laser spot 1 to complete the processing of the target part. When the first molten pool gradient is greater than the preset temperature gradient threshold, the second laser power required for the annular laser spot 2 can be determined based on the molten pool center temperature and molten pool radius generated by the central laser spot 1 in the scanning area at a preset scanning speed. This ensures reasonable setting of the laser power for the central laser spot 1 and the annular laser spot 2, thereby satisfying the precise control of the molten pool gradient and cooling rate. This allows the molten pool to cool more uniformly during solidification, effectively reducing defects such as cracks and porosity caused by high temperature gradients and high cooling rates, and solving the cracking problem in laser additive manufacturing of high-performance, difficult-to-weld high-temperature alloys.

[0038] In this embodiment, the first molten pool gradient of the scanning region at a preset scanning speed for the central spot 1 is... ,in To obtain the center temperature of the molten pool in the scanning region of the center spot 1 at a preset scanning speed, experimental or simulation analysis was conducted under the parameter conditions of the center spot 1. The radius of the molten pool in the scanning area of ​​the center spot 1 at a preset scanning speed is obtained through experimental or simulation analysis under the parameter conditions of the center spot 1.

[0039] In this embodiment, the second laser power of the annular spot 2 is based on ,in The second laser power of the annular spot 2, The absorption rate of the metal powder material to the laser. The design outer diameter of the annular spot 2, Specific heat capacity of metal powder materials. The density of the metal powder material, The thickness of a single layer of metal powder. The scanning speed of the composite laser spot over the layup processing position. This is an empirical coefficient. The value range is 0.2 to 0.8. The temperature of the molten pool center in the laser scanning region of a single layered slice under the specified central spot 1 parameter is [temperature value missing]. The temperature is set to room temperature. By comprehensively considering the material properties of the metal powder, such as laser absorption rate, specific heat capacity, and density, as well as factors such as layup thickness and scanning speed, the second laser power required to form an annular spot 2 with an ideal molten pool gradient and cooling rate can be accurately obtained, ensuring that it matches the laser power of the central spot 1, thereby effectively suppressing the generation of defects such as cracks and pores.

[0040] In this embodiment, the metal powder is MarM247 alloy powder, wherein the MarM247 alloy powder contains 0.07-0.1 wt.% C, ≤0.06 wt.% Si, 8.0-8.7 wt.% Cr, 9-10 wt.% Co, 0.4-0.8 wt.% Mo, 0.005-0.02 wt.% Zr, 5.25-5.75 wt.% Al, ≤0.2 wt.% Fe, 9.5-10.5 wt.% W, ≤2.8-3.3 wt.% Ta, 1.3-1.6 wt.% Hf, 0.6-0.9 wt.% Ti, and the balance is Ni. The particle size of the MarM247 alloy powder is 15-53 μm.

[0041] In this embodiment, the laser power of the central spot 1 is 200-220W, and the scanning speed is 900-950mm / s; the laser power of the annular spot 2 is 100-150W, and the scanning speed is synchronized with that of the central spot 1.

[0042] In this embodiment, when the first molten pool gradient is >106K / m, the annular spot 2 is activated; otherwise, it is not activated.

[0043] Based on the same inventive concept, this embodiment also provides equipment for suppressing crack defects in laser additive manufacturing of difficult-to-weld high-temperature alloys, including:

[0044] The powder spreading system is used to spread high-temperature alloy powder layer by layer in a bottom-up, layered slicing structure;

[0045] A laser scanning system is used to generate a central spot 1 with a first laser power and a corresponding annular spot 2 with a second laser power, and to scan and melt the metal powder at each layup processing position layer by layer.

[0046] An atmosphere protection system is used to control the gas flow within the forming chamber and remove splashes.

[0047] The equipment provided in this embodiment for suppressing crack defects in refractory high-temperature alloys manufactured using laser additive manufacturing includes a powder spreading system, a laser scanning system, and an atmosphere protection system. These components work together to achieve precise control of the laser additive manufacturing process. The powder spreading system ensures that the metal powder is uniformly and stably spread within the forming chamber; the laser scanning system precisely controls the parameters and scanning path of the composite laser spot to precisely regulate the molten pool gradient and cooling rate; and the atmosphere protection system provides a stable and clean working environment for the laser additive manufacturing process by controlling the gas flow within the forming chamber and removing spatter.

[0048] In this embodiment, the laser scanning system achieves continuous adjustment of the diameter of the central spot 1 (50-160μm) and the diameter of the annular spot 2 (150-400μm) through an electric beam expander, and the energy attenuation of the optical path system is ≤5%, ensuring precise control of the laser spot and uniformity of energy distribution.

[0049] In this embodiment, the atmosphere protection system adopts an airflow scheme with air intake on one side and air outlet on multiple sides, ensuring that the wind speed uniformity on the printing surface is ≤±0.2m / s. An air curtain is formed below the protective mirror to isolate smoke and dust. The protective mirror refers to the galvanometer protective mirror; if smoke and dust adhere to the protective mirror, it will affect light transmission, thereby affecting laser energy. This embodiment ensures the stability of gas flow within the forming chamber and effectively prevents smoke and dust generated during the printing process from contaminating the laser scanning system and the formed part, providing a cleaner and more stable working environment for laser additive manufacturing of high-temperature alloys.

[0050] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of suppressing crack defects in laser additive manufacturing of a difficult-to-weld superalloy, characterized in that, The method comprises the following steps: According to the placement form and position of the target part in the forming chamber of the laser scanning forming equipment, the three-dimensional solid geometric model of the target part is sliced in the vertical direction; the laser scanning forming equipment is used to form a composite laser spot for melting the metal powder scanning area corresponding to each sliced layer of the target part, and the composite laser spot comprises a center spot and an annular spot located at the periphery of the center spot; According to the performance parameters of the target part metal powder, the center spot parameters of the laser scanning forming equipment are determined, the center spot parameters comprising the center spot radius and the first laser power of the center spot; According to the determined center spot parameters, the molten pool center temperature and the molten pool radius of the scanning area at a preset scanning speed are obtained through test or simulation analysis, and the first molten pool gradient of the scanning area at the preset scanning speed is obtained according to the molten pool center temperature and the molten pool radius; When the first molten pool gradient is greater than the preset temperature gradient threshold, the second laser power required by the annular spot is obtained according to the laser scanning area molten pool center temperature of a single sliced layer under the center spot parameters, the design outer diameter of the annular spot, and the layer thickness of the metal powder; According to the bottom-up layered slice structure, the metal powder is sequentially and layer by layer laid in the forming chamber, and if the first molten pool gradient is greater than the preset temperature gradient threshold, the laser scanning forming equipment is controlled to generate the center spot with the first laser power and the corresponding annular spot with the second laser power, and the metal powder at each layer processing position is sequentially and layer by layer scanned and melted to complete the processing of the target part; otherwise, the center spot is generated with the first laser power alone to complete the processing of the target part.

2. The method of suppressing crack defects in laser additive manufacturing of a hard to weld superalloy of claim 1, wherein, a first molten pool gradient of the central spot at a preset scanning speed in a scanning area wherein a molten pool center temperature of the central spot at the preset scanning speed in the scanning area is obtained by an experiment or simulation analysis under the central spot parameter condition, a molten pool radius of the central spot at the preset scanning speed in the scanning area is obtained by an experiment or simulation analysis under the central spot parameter condition.

3. The method of claim 2, wherein the laser additive manufacturing is performed using a laser power of 1.5 kW or less. the second laser power of the annular light spot is determined according to wherein the second laser power of the annular light spot, the absorption rate of the metal powder material to the laser, the designed outer diameter of the annular light spot, the specific heat capacity of the metal powder material, the density of the metal powder material, the single layer thickness of the metal powder, the scanning speed of the composite laser light spot to the layer processing position, the empirical coefficient, the value range of is 0.2-0.8, the laser scanning area molten pool center temperature of a single layering slice under the center light spot parameter, room temperature.

4. The method of suppressing crack defects in laser additive manufacturing of a hard to weld superalloy of claim 1, wherein, The metal powder is MarM247 alloy powder, the content of C in the MarM247 alloy powder is 0.07-0.1wt.%, the content of Si is ≤0.06wt.%, the content of Cr is 8.0-8.7wt.%, the content of Co is 9-10wt.%, the content of Mo is 0.4-0.8wt.%, the content of Zr is 0.005-0.02wt.%, the content of Al is 5.25-5.75wt.%, the content of Fe is ≤0.2wt.%, the content of W is 9.5-10.5wt.%, the content of Ta is ≤2.8-3.3wt.%, the content of Hf is 1.3-1.6wt.%, the content of Ti is 0.6-0.9wt.%, and the balance is Ni, the particle size of the MarM247 alloy powder is 15-53μm.

5. The method of suppressing crack defects in laser additive manufacturing of a hard to weld superalloy of claim 4, wherein, The laser power of the center spot is 200-220W, and the scanning speed is 900-950mm / s; the laser power of the annular spot is 100-150W, and the scanning speed is synchronized with the center spot.

6. Apparatus for inhibiting crack defects in laser additive manufacturing of a difficult-to-weld superalloy for carrying out the method for inhibiting crack defects in laser additive manufacturing of a difficult-to-weld superalloy according to any one of claims 1 to 5, characterized in that The method comprises the following steps: A powder laying system is used to lay the high-temperature alloy powder layer by layer according to the bottom-up layered slice structure; A laser scanning system is used to generate the center spot with the first laser power and the corresponding annular spot with the second laser power, and sequentially and layer by layer scan and melt the metal powder at each layer processing position; An atmosphere protection system is used to control the gas flow in the forming chamber and remove the splashes.

7. The apparatus of claim 6, wherein the apparatus is configured to: The laser scanning system realizes continuous adjustment of the center spot diameter of 50-160 μm and the ring spot diameter of 150-400 μm through a motorized beam expander, and the energy attenuation of the optical system is less than or equal to 5%.

8. The apparatus of claim 6, wherein the apparatus is configured to inhibit crack formation in the laser additive manufacturing of the refractory superalloy. The atmosphere protection system adopts a one-side air inlet and multi-side air outlet air flow scheme, and the printing surface air speed uniformity is less than or equal to ±0.2 m / s.

Images