Magnetic field reinforced laser cladding process

Abstract

The invention is applicable to the technical field of laser cladding, and provides a magnetic field reinforced laser cladding process which specifically comprises the following steps: firstly, setting a laser repair path, then applying a 0.2-0.6 T stable magnetic field to the surface of a base material, inducing Joule heat to be generated in an internal defect area of the material, and promoting structure homogenization; then the distance between a laser device and the surface of the base material is set to be 15 mm, then laser cladding parameters are set, the light spot diameter is 0.7 mm, the frequency is 25 HZ, the laser power is 1.2 kw to 1.5 kw, the powder feeding rate is 2 g / min to 3.5 g / min, the scanning speed is 120 mm / min to 210 mm / min, and then electromagnetic field auxiliary cladding is carried out. When the magnetic field intensity is increased to 0.6 T, the porosity is reduced from 0.31% to 0.07%, the reduction amplitude reaches 87%, the average pore size is increased by 1.78 times, an electromagnetic field is applied in the laser cladding process, the mass and heat transfer process is changed through the stirring effect of electromagnetic force on a molten pool, and the purposes of improving the cladding layer quality, refining the microstructure and improving the performance can be achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser cladding, and in particular to a magnetic field enhanced laser cladding process. Background Art

[0002] Laser cladding is an advanced surface modification technology with advantages such as fast cladding speed, high coating quality, and low dilution rate. Laser cladding technology is widely used in aerospace, equipment manufacturing, petrochemical and other fields.

[0003] However, during the ultra-high-speed laser cladding process, cracks, pores, inclusions and uneven distribution of solute elements are easily generated in the cladding layer, which affects the quality of the cladding layer.

[0004] Therefore, in view of the above situation, there is an urgent need to develop a magnetic field enhanced laser cladding process to overcome the shortcomings in current practical applications. Summary of the Invention

[0005] The purpose of the embodiments of the present invention is to provide a magnetic field enhanced laser cladding process, aiming to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A magnetic field enhanced laser cladding process specifically comprises the following steps:

[0008] S1: Setting the laser repair path;

[0009] S2: magnetic field pretreatment;

[0010] S3: Set the distance between the laser and the substrate surface;

[0011] S4: Laser cladding parameter setting;

[0012] S5: Electromagnetic field assisted cladding.

[0013] As a further technical solution, in S2, a stable magnetic field of 0.2-0.6T is applied to the surface of the substrate to induce Joule heat in the defective areas inside the material and promote tissue homogenization.

[0014] In a further technical solution, the distance between the laser and the substrate surface in S3 is set to 15 mm.

[0015] Further technical solutions, the spot diameter of S4 is 0.7mm, the frequency is 25HZ, the laser power is 1.2kw-1.5kw, the powder feeding rate is 2g / min-3.5g / min, and the scanning speed is 120mm / min-210mm / min.

[0016] According to a further technical solution, when the magnetic field intensity is 0.6 T, the porosity of the cladding layer is 0.07%.

[0017] According to a further technical solution, the powder selected in the cladding process is spherical powder of TC17 titanium alloy with a particle size ranging from 60 μm to 145 μm.

[0018] In summary, the embodiments of the present invention have the following beneficial effects compared with the prior art:

[0019] Under the action of DC regulated current, a magnetic field is added for disturbance. Under the combined action of the self-induced magnetic field and the self-induced current caused by the magnetic field, a magnetostriction effect is generated inside the molten pool, causing the molten metal liquid to move toward the center of the molten pool, which helps to reduce cracks caused by uneven flow of the molten pool. At the same time, the gas and inclusions inside the molten pool will be moved to the outside of the molten pool due to the effect of electromagnetic repulsion, achieving the purpose of reducing porosity and purifying inclusions; by stabilizing the magnetic field on the component, inducing the material to undergo recovery and recrystallization and other structural evolution behaviors, it helps to achieve the transformation of uneven structure to homogenization, thereby improving material properties. When the magnetic field intensity is increased to 0.6T, the porosity is reduced from 0.31% to 0.07%, a decrease of 87%, the average pore size increases by 1.78 times, and the porosity is significantly reduced.

[0020] In order to more clearly illustrate the structural features and effects of the present invention, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a flow chart of the present invention;

[0022] Figure 2 This is a schematic diagram of the laser repair path in the magnetic field of the present invention;

[0023] Figure 3 This is a comparison diagram of the cross-sectional pore distribution of the repair area under different magnetic field intensities of the present invention.

[0024] Figure 4 is a bar chart showing the particle size and content percentage of the TC17 titanium alloy powder of the present invention;

[0025] Figure 5 Schematic diagram of the microscopic morphology of TC17 titanium alloy powder of the present invention;

[0026] Figure 6 For the present invention Figure 2 A magnified schematic diagram of a part in the figure. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] The specific implementation of the present invention is described in detail below with reference to specific embodiments.

[0029] like Figure 1 As shown, the embodiment of the present invention provides a magnetic field enhanced laser cladding process, which specifically includes the following steps:

[0030] S1: Setting the laser repair path;

[0031] like Figure 2 As shown, a program is written in the computer control system to complete the setting of the laser repair path.

[0032] S2: Magnetic field pretreatment: applying a stable magnetic field on the substrate surface to induce Joule heating in the defective areas inside the material and promote tissue homogenization;

[0033] It can be understood that magnetic field preheating is a special material heat treatment method that improves material properties by applying a stable magnetic field to the component, inducing the material to undergo structural evolution behaviors such as recovery and recrystallization. Unlike conventional heat treatment technologies, stable magnetic field preheating uses the magnetic field as an energy source to stimulate heat generation within the material, causing areas with more material defects (dislocations, grain boundaries, etc.) (high resistance) to generate higher heat, exhibiting a local Joule heating effect. For large deformation areas of non-uniform components, this local Joule heating effect can cause structural evolution to occur primarily in deformation areas with higher defect content. This "targeted" characteristic in material structural regulation helps achieve the transformation of non-uniform structures to homogenization.

[0034] Preferably, the powder used in the magnetic field preheating laser additive repair experiment is spherical powder of TC17 titanium alloy, such as Figure 4 As shown, the particle size range is between 60μm and 145μm, and the powder morphology and particle size distribution are as shown in Figure 4-Figure 6 shown.

[0035] In specific applications, a stable magnetic field with an intensity of 0.2T-0.6T is applied to the surface of the substrate.

[0036] S3: Set the distance between the laser and the substrate surface;

[0037] In specific applications, the distance between the laser and the substrate surface is set to 15 mm to ensure that the focus of the laser beam is near the powder aggregation point to fully melt the powder and ensure that the repaired sample has excellent performance while reducing the risk of laser damage due to laser reflection.

[0038] S4: Laser cladding parameter setting;

[0039] In specific applications, the spot diameter is 0.7mm, the frequency is 25HZ, and the laser power is adjusted within the range of 1.2kW-1.5kW, the powder feeding rate is adjusted within the range of 2g / min-3.5g / min, and the scanning speed is adjusted within the range of 120mm / min-210mm / min according to experimental requirements.

[0040] S5: Electromagnetic field assisted cladding generates a magnetic field through a DC regulated current, and uses electromagnetic repulsion to drive the gas and inclusions in the molten pool to escape to the surface. At the same time, the magnetostriction effect causes the molten metal to gather towards the center of the molten pool, reducing porosity.

[0041] In specific applications, during the laser additive repair process, a magnetic field is added to the substrate and the cladding sample area under the action of a DC stabilized current to cause disturbances. Under the combined action of the self-induced magnetic field and the self-induced current caused by the stable magnetic field, a magnetostriction effect is generated inside the molten pool, causing the molten metal to move toward the center of the molten pool. At the same time, the gas and inclusions inside the molten pool will be moved to the outside of the molten pool by the effect of electromagnetic repulsion, thereby achieving the purpose of reducing porosity and purifying inclusions. In addition, during this process, the protective gas is started, the powder feeder and the laser are remotely controlled, and cladding is performed along the scanning path.

[0042] In the embodiment of the present invention, the relationship between the magnetic field intensity and the porosity of the repair area was explored by changing the magnetic field intensity. Figure 3The pore distribution comparison diagram of the repair area section under different magnetic field intensities, where (a), (b), (c) and (d) represent the pore distribution diagrams under no magnetic field, 0.2T, 0.4T and 0.6T magnetic field intensities, respectively. It can be seen that the number of pores is large and the distribution is relatively dispersed without stable magnetic field preheating. With the increase of magnetic field intensity, the number of pores decreases significantly, especially the number of small pores is greatly reduced. The pore number and pore size of the repair area are measured and counted using relevant software. The pore number of samples (a), (b), (c) and (d) are 281, 220, 69 and 36, respectively. Compared with sample (a), the pore number in sample (d) is reduced by 87%. Porosity refers to the ratio of the total pore area to the area of the repair area. In the absence of an external magnetic field, the porosity of the sample is 0.31%. With the assistance of the magnetic field preheating device, it can be seen that the porosity decreases significantly with the increase of magnetic field intensity, and the porosity reaches the lowest value of 0.07% when the magnetic field is 0.6 T. Compared with the porosity of sample (a), the porosity of sample (d) is reduced by 87%. The average pore size is determined based on the correlation between the number of pores and the porosity, which is expressed as the relative size of a single pore in the laser repair area. It can be seen that its value increases with the increase of magnetic field intensity, which means that the increase in magnetic field intensity increases the average size of pores in the sample. The fusion of pores induced by magnetic field intensity leads to this result. With the increase of magnetic field intensity, the trend of pore fusion becomes more obvious. Compared with sample (a), the average pore size in samples (b), (c) and (d) increases by 1.14 times, 1.71 times and 1.78 times, respectively.

[0043] The circuits, electronic components and modules involved are all existing technologies and can be fully implemented by those skilled in the art. Needless to say, the content protected by the present invention does not involve improvements to software and methods.

[0044] The above description is only a preferred embodiment of the present invention and is 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 in the scope of protection of the present invention.

Claims

1. A magnetic field enhanced laser cladding process, characterized in that: The specific steps include: S1: Setting the laser repair path; S2: magnetic field pretreatment; S3: Set the distance between the laser and the substrate surface; S4: Laser cladding parameter setting; S5: Electromagnetic field assisted cladding.

2. The magnetic field enhanced laser cladding process according to claim 1, characterized in that: In S2, a stable magnetic field of 0.2-0.6T is applied to the surface of the substrate to induce Joule heat in the defective areas inside the material and promote tissue homogenization.

3. The magnetic field enhanced laser cladding process according to claim 1, characterized in that: The distance between the laser and the substrate surface in S3 was set to 15 mm.

4. The magnetic field enhanced laser cladding process according to claim 1, characterized in that: The spot diameter of S4 is 0.7mm, the frequency is 25HZ, the laser power is 1.2kw-1.5kw, the powder feeding rate is 2g / min-3.5g / min, and the scanning speed is 120mm / min-210mm / min.

5. The magnetic field enhanced laser cladding process according to claim 2, characterized in that When the magnetic field intensity in S2 is 0.6 T, the porosity of the cladding layer is 0.07%.

6. The magnetic field enhanced laser cladding process according to claim 5, characterized in that: The powder used in the cladding process is spherical powder of TC17 titanium alloy with a particle size range of 60μm to 145μm.

Images