阅读说明：本技术 一种降低激光增材制造镍基高温合金热裂敏感性的方法 (Method for reducing hot cracking sensitivity of laser additive manufacturing nickel-based high-temperature alloy ) 是由 肖辉 宋立军 谢盼 肖文甲 成满平 于 2020-12-23 设计创作，主要内容包括：本发明公开了一种降低激光增材制造镍基高温合金热裂敏感性的方法。将基材预热至320℃；采用热成像仪对激光增材制造过程中熔池进行监测,获得熔池形貌及温度信息,计算出熔池长轴平均值a与短轴平均值b,并计算出熔池边界的平均冷却速率ξ；1.55≤a/b≤2.35,且4.2×10～4℃/s≤ξ≤1.5×10～5℃/s原则对工艺参数进行优化,获得优化工艺窗口：激光功率为1400-1800W,扫描速度为13～16mm/s,光斑直径为4～5mm,送粉量为20-25g/min,搭接量50%,高度方向增量Z为0.25～0.35毫米/层；获得高质量的镍基高温合金成形件。本发明能有效提高激光增材制造镍基高温合金的内部质量。(The invention discloses a method for reducing the hot cracking sensitivity of a laser additive manufacturing nickel-based high-temperature alloy. Preheating the substrate to 320 ℃; monitoring a molten pool in a laser additive manufacturing process by adopting a thermal imager to obtain the appearance and temperature information of the molten pool, calculating a long axis average value a and a short axis average value b of the molten pool, and calculating an average cooling rate xi of a molten pool boundary; a/b is not less than 1.55 and not more than 2.35, and 4.2 x 10 4 ℃/s≤ξ≤1.5×10 5 Optimizing the process parameters according to the principle of DEG C/s to obtain an optimized process window: the laser power is 1400-1800W, the scanning speed is 13-16 mm/s, the spot diameter is 4-5 mm, the powder feeding amount is 20-25g/min, the lapping amount is 50%, and the increment Z in the height direction is 0.25-0.35 mmA layer; obtaining the high-quality nickel-based superalloy formed piece. The invention can effectively improve the internal quality of the nickel-based high-temperature alloy manufactured by the laser additive.)

1. A method for reducing the heat cracking sensitivity of a laser additive manufacturing nickel-based superalloy is characterized by comprising the following steps:

the method comprises the following steps: firstly, polishing, ultrasonically cleaning and drying the surface of a base material, and preheating the base material to 320 ℃ by adopting electromagnetic induction heating equipment;

step two: monitoring a molten pool in a laser additive manufacturing process by adopting a thermal imager to obtain the shape and temperature change information of the molten pool, calculating a long axis average value a and a short axis average value b of the molten pool, and calculating an average cooling rate xi of a molten pool boundary;

step three: according to 1.55. ltoreq. a/b. ltoreq.2.35, and 4.2X 10⁴℃/s≤ξ≤1.5×10⁵Optimizing process parameters according to the principle of DEG C/s;

step four: the optimized process window obtained is as follows: the laser power is 1400-1800W, the scanning speed is 13-16 mm/s, the spot diameter is 4-5 mm, the powder feeding amount is 20-25g/min, the lap joint amount is 50%, and the increment Z in the height direction is 0.25-0.35 mm/layer;

step five: and finally, performing laser additive manufacturing on the nickel-based superalloy according to the process parameters and the method to obtain a high-quality nickel-based superalloy forming part.

2. The method of claim 1, wherein the method comprises the steps of: in the second step, the emissivity of the thermal imager is set to be 1.05, and the single data acquisition time is 2 ms.

3. The method of claim 1, wherein the method comprises the steps of: in the fifth step, 1.5% pure zirconium powder and 0.5% pure aluminum powder by mass percent are added into the nickel-based superalloy powder.

4. The method of claim 1, wherein the method comprises the steps of: in step five, the scanning path is a cross scanning path or a bidirectional scanning path.

Technical Field

The invention relates to the field of laser metal material processing, in particular to a method for reducing the hot cracking sensitivity of a nickel-based high-temperature alloy manufactured by laser additive manufacturing.

Background

The laser additive manufacturing technology is one of the most potential advanced manufacturing technologies at present, takes a high-energy laser beam as a heat source, considers the requirements of precise forming and high-performance forming, has the advantages of high flexibility, short period, no limitation of part structures and materials in forming and the like, and is particularly suitable for directly forming traditional difficult-to-process materials, parts with complex shapes and gradient functional parts. Meanwhile, the damaged parts can be quickly repaired. The nickel-based superalloy has excellent comprehensive properties such as good structural stability, high-temperature strength, high-temperature fatigue, corrosion resistance, oxidation resistance and the like, and is widely applied to the fields of aerospace, energy power, petrochemical industry and the like. At present, the laser additive manufacturing nickel-based high-temperature alloy is widely used for direct forming and rapid repair of parts with complex structures. In general, laser additive manufacturing adopts high-power laser to melt a base material and a powder material, and then realizes the formation of a three-dimensional solid part in a layer-by-layer superposition processing mode. The rapid cooling of the local molten pool during laser additive manufacturing results in high cooling rates, high temperature gradients and non-equilibrium solidification of the molten pool. One of the most significant structural features of laser additive manufacturing nickel-base superalloys is the segregation of interdendritic elements and the formation of brittle eutectic phases. However, the formation of brittle eutectic phases is very detrimental to the final properties of the shaped articles. The long chain brittle eutectic phase provides favorable conditions for micropore aggregation and crack propagation under the action of stress, so that the tensile property, the fracture toughness and the fatigue property of a formed part are obviously reduced. More importantly, the formation of long chain low melting eutectic phases during additive manufacturing increases the hot crack sensitivity of the formed part. Therefore, it is necessary to control the precipitation behavior of the eutectic phase during solidification to reduce the heat cracking sensitivity during forming.

The invention provides a method for reducing the hot cracking sensitivity of a laser additive manufacturing nickel-based high-temperature alloy, which can effectively control the formation of a eutectic phase in a solidification process and improve the internal quality of a formed piece.

Disclosure of Invention

The invention aims to provide a method for reducing the hot cracking sensitivity of a laser additive manufacturing nickel-based superalloy.

A method for reducing the thermal cracking sensitivity of a laser additive manufacturing nickel-based superalloy, comprising the following steps:

the method comprises the following steps: firstly, polishing, ultrasonically cleaning and drying the surface of a base material, and preheating the base material to 320 ℃ by adopting electromagnetic induction heating equipment;

step two: monitoring a molten pool in a laser additive manufacturing process by adopting a thermal imager to obtain the shape and temperature change information of the molten pool, calculating a long axis average value a and a short axis average value b of the molten pool, and calculating an average cooling rate xi of a molten pool boundary;

step three: according to 1.55. ltoreq. a/b. ltoreq.2.35, and 4.2X 10⁴℃/s≤ξ≤1.5×10⁵Optimizing process parameters according to the principle of DEG C/s;

step four: the optimized process window obtained is as follows: the laser power is 1400-1800W, the scanning speed is 13-16 mm/s, the spot diameter is 4-5 mm, the powder feeding amount is 20-25g/min, the lap joint amount is 50%, and the increment Z in the height direction is 0.25-0.35 mm/layer;

step five: and finally, performing laser additive manufacturing on the nickel-based superalloy according to the process parameters and the method to obtain a high-quality nickel-based superalloy forming part.

In the second step, the emissivity of the thermal imager is set to be 1.05, and the single data acquisition time is 2 ms.

In the fifth step, 1.5% pure zirconium powder and 0.5% pure aluminum powder by mass percent are added into the nickel-based superalloy powder.

In step five, the scanning path is a cross scanning path or a bidirectional scanning path.

A large number of experiments prove that a/b is more than or equal to 1.55 and less than or equal to 2.35 and is 4.2 multiplied by 10⁴℃/s≤ξ≤1.5×10⁵Optimizing the technological parameters according to the principle of DEG C/s, wherein the optimized technological parameters are as follows: the laser power is 1400-1800W, the scanning speed is 13-16 mm/s, the spot diameter is 4-5 mm, and the powder feeding amount is20-25g/min, the lapping amount is 50%, and the increment Z in the height direction is 0.25-0.35 mm/layer; the laser additive manufacturing is carried out according to the optimized process parameters and the method, on one hand, the cooling rate of a molten pool is obviously improved, the dendritic crystal structure can be effectively refined, and the generation of a discrete eutectic phase is promoted. In addition, 1.5 percent of pure zirconium powder and 0.5 percent of pure aluminum powder are added into the nickel-based high-temperature alloy powder, in the additive manufacturing process, the pure zirconium powder and the pure aluminum powder generate in-situ reaction with oxygen in a molten pool to generate high-melting-point zirconium oxide and aluminum oxide ceramic particles, and the high-melting-point particles provide heterogeneous nucleation points for nucleation of crystal grains or dendrites in the solidification process of the molten pool, so that the microstructure is refined, the formation of a large number of equiaxial structures is promoted, the generation of thermal cracks is avoided, and further, crack-free additive manufacturing parts are obtained.

Drawings

FIG. 1 is a metallographic diagram of a sample of a nickel-base superalloy manufactured by laser additive manufacturing according to a conventional method;

FIG. 2 is a gold phase diagram of a sample of the laser additive manufacturing nickel-base superalloy obtained by the invention.

Detailed Description

Example 1

The Inconel 718 alloy is taken as an example.

A method for reducing the thermal cracking sensitivity of a laser additive manufacturing nickel-based superalloy, comprising the following steps:

the method comprises the following steps: firstly, polishing, ultrasonically cleaning and drying the surface of a base material, and preheating the base material to 320 ℃ by adopting electromagnetic induction heating equipment.

Step two: and monitoring a molten pool in the laser additive manufacturing process by using a thermal imager to obtain the shape and temperature change information of the molten pool, calculating a long axis average value a and a short axis average value b of the molten pool, and calculating the average cooling rate xi of the boundary of the molten pool.

Step three: according to 1.55. ltoreq. a/b. ltoreq.2.35, and 4.2X 10⁴℃/s≤ξ≤1.5×10⁵The process parameters are optimized according to the principle of DEG C/s.

Step four: the optimized process window obtained is as follows: the laser power is 1500W, the scanning speed is 14mm/s, the diameter of a light spot is 4.5mm, the powder feeding amount is 23g/min, the lapping amount is 50%, and the increment Z in the height direction is 0.3 mm/layer.

Step five: and finally, performing laser additive manufacturing on the nickel-based high-temperature alloy mixed powder (98 mass percent of Inconel 718 alloy powder, 1.5 mass percent of pure zirconium powder and 0.5 mass percent of pure aluminum powder) according to the process parameters and the method to obtain a high-quality nickel-based high-temperature alloy forming piece.

Fig. 1 is a scanning electron microscope image of an additive manufacturing sample obtained by a conventional method. The internal structure of the formed sample mainly comprises fine columnar dendrites, obvious element segregation and eutectic phase exist among the dendrites, obvious thermal cracks exist in the grain boundary, and the generation of the cracks is related to low-melting-point eutectic crystals generated in the additive manufacturing of the nickel-based high-temperature alloy and a high stress state of the formed sample. The above results show that it is difficult to eliminate thermal cracking outside the process of this patent.

Fig. 2 is a scanning electron micrograph of an additive manufacturing sample obtained in example 1 of the present invention. It can be seen from the figure that the internal structure of the forming sample mainly comprises fine equiaxed dendrites, and fine discrete eutectic phases exist in equiaxed dendrite intercrystalline regions, and the method can obtain high cooling rate and fluctuation of a molten pool, promote supercooling and nucleation rate of the molten pool, and in addition, pure zirconium powder and pure aluminum powder generate high-melting-point zirconium oxide and aluminum oxide ceramic particles through in-situ reaction with oxygen in the molten pool to provide heterogeneous nucleation points for dendrite nucleation, so that the microstructure is refined, the generation of thermal cracks is inhibited, and the mechanical property is improved. The results show that the method can effectively refine the microstructure and reduce the thermal sensitivity of the nickel-based superalloy formed part.

Example 2

Taking single crystal alloy RR3010 as an example

A method for reducing the thermal cracking sensitivity of a laser additive manufacturing nickel-based superalloy, comprising the following steps:

the method comprises the following steps: firstly, polishing, ultrasonically cleaning and drying the surface of a base material, and preheating the base material to 320 ℃ by adopting electromagnetic induction heating equipment.

Step two: and monitoring a molten pool in the laser additive manufacturing process by using a thermal imager to obtain the shape and temperature change information of the molten pool, calculating a long axis average value a and a short axis average value b of the molten pool, and calculating the average cooling rate xi of the boundary of the molten pool.

Step three: according to 1.55. ltoreq. a/b. ltoreq.2.35, and 4.2X 10⁴℃/s≤ξ≤1.5×10⁵The process parameters are optimized according to the principle of DEG C/s.

Step four: the optimized process window obtained is as follows: the laser power is 1750W, the scanning speed is 13.5mm/s, the spot diameter is 4.2mm, the powder feeding amount is 22g/min, the lapping amount is 50%, and the increment Z in the height direction is 0.3 mm/layer.

Step five: and finally, performing laser additive manufacturing on the nickel-based high-temperature alloy mixed powder (the RR3010 powder with the mass fraction of 98% + 1.5% of pure zirconium powder and 0.5% of pure aluminum powder) according to the process parameters and the method to obtain a high-quality nickel-based high-temperature alloy forming piece.