CN106191854A - A kind of preparation method of control pore Ni-based coating - Google Patents

Abstract

The present invention relates to the preparation method of a kind of control pore Ni-based coating, comprise the steps: A: polish, clean, scrubbing；B: laser melting coating: use coaxial powder feeding device that nickel base powder is sent into matrix surface, forms laser melting coating molten bath, successively carries out laser melting coating with laser scanning and make cladding molten bath form bubble；C: Lorentz force body force couples: formed in bubble at cladding bath described in step B, being simultaneously introduced adjustable gradient Lorentz force, the bubble forming step B process carries out pore that profile adjustment forms it in cladding layer by surface to the inside depth direction distribution gradient or be evenly distributed.The magnetic field intensity gradient of DC current size and weld pool surface that the inventive method is applied to substrate surface by adjustment affects the downward gradient of Lorentz force.It is not only does this apply to laser fusion covered nickel base coating, welding, laser melting etc. can be suitable for simultaneously and produce the form processing in molten bath, applied widely.

Description

A kind of preparation method of controllable porosity nickel base coating

technical field

The invention relates to a preparation method of a nickel-based coating, in particular to a preparation method of a nickel-based coating with adjustable porosity.

Background technique

As a new type of manufacturing technology, laser cladding technology has been more and more used in industrial production. During the cladding process, due to the moisture in the environment, the carrier gas or the presence of C, Ti and other elements in the cladding material, the cladding layer often inevitably generates pores randomly. However, with the increasingly harsh conditions of use, the performance requirements of the coating are also getting higher and higher. In some applications, while meeting the requirements of mechanical properties, it is necessary to set requirements for the shock resistance and thermal conductivity of the cladding layer. According to the relevant literature, the number and distribution of pores in the coating have an important impact on the above properties, so the pores in the cladding layer need to be adjusted. However, it is difficult to quantitatively control the content and distribution of pores in the cladding layer simply by changing the parameters of the laser cladding process or the powder process. To solve the above problems, the present invention provides a method for preparing a nickel-based coating with adjustable pores.

Scholars at home and abroad have carried out a series of research on the control technology of laser welding and cladding process by external magnetic field. For example, Bachmann in Germany improved the morphology of aluminum alloy welding pool through static magnetic field, and Gatzen M in Bremen laboratory found that alternating magnetic field affects the distribution of elements, but the Lorentz force used by the above-mentioned scholars is The Lorentz force is induced by itself, not the external Lorentz force and the stomata are not studied. Many domestic scholars have also conducted research on it. For example, the public document (CN102899661) proposed a method of magnetic field-assisted laser cladding. Uniform coating. The published document (CN102703897) proposes a method for preparing Fe60 composite coatings by rotating magnetic field-assisted laser cladding, because the method uses a rotating magnetic field, which also makes the internal Lorentz force change periodically, and the result is often It makes the distribution of cladding layer structure, elements, particles, etc. more uniform, and cannot control the directional movement of pores, particles, etc., and does not involve the combined regulation of cladding process and magnetic field; the open document (CN104195541) proposes an electromagnetic composite field assisted The method and device of laser cladding, the method provided in the document mainly adopts the electromagnetic compound field to control the objects such as tissue, particles, elements, and surface morphology, and does not involve the generation process of laser cladding bubbles and the control of bubble movement. Most of the inventions or researches are based on the structure, performance and molten pool movement of materials, and pores are often regarded as defects to avoid their generation.

Contents of the invention

The invention overcomes the defect that the existing laser cladding technology cannot control the distribution of pores, and provides a method for preparing a nickel-based coating with controllable pores.

The preparation method of a kind of controllable pore nickel-based coating of the present invention comprises the following steps:

A: Polishing, cleaning, and decontamination: Polish the surface of the substrate until the surface is bright and the surface roughness is less than Ra1.6, then wipe and clean with acetone or alcohol to remove the surface oil, and dry in a ventilated place;

B: Laser cladding: Use a coaxial powder feeder to send nickel-based powder into the surface of the substrate to form a laser cladding molten pool, and use laser scanning to perform laser cladding layer by layer to form bubbles in the cladding molten pool. Adjust according to the following parameters Nickel-based powder Ti, C content, powder particle size, powder sphericity, moisture content in the shielding gas and combined with laser process parameters to control the number of pores in the cladding layer;

The mass fraction of the nickel-based powder is: Ni 50.0-55.0%, Cr 12.0-17.10%, C 0.08-0.2%, Si 0-0.35%, Mn0-0.35%, S 0-0.018%, P0-0.015%, Al 0.30～0.70%, Ti1.10～2%, Mo 2.8～3.30%, Nb 4.75～5.50%, the balance is Fe;

The particle size of the powder d=50-150 μm;

The powder sphericity is 0.6～0.9;

The moisture content mass fraction in the protective gas is 0.05-2%;

The laser process parameters are controlled at a laser power of 800-1800W; a scanning speed of 6-15mm/s; a shielding gas flow rate of 10-80HF/min; a powder feeding volume of 8-20g/min;

Usually under the above conditions, the shape of the pores in the cladding layer is spherical, the diameter ranges from 5 μm to 100 μm, and the total volume of the pores in the cladding layer is 0.1 to 5% of the total volume of the cladding layer;

C: Coupling of Lorentz force and body force: In step B, on the basis of forming bubbles inside the cladding pool (also known as "bubbling"), an adjustable gradient Lorentz force is introduced at the same time, for the step The distribution of the bubbles formed in the B process is adjusted so that the pores formed by the bubbles are distributed in a gradient or evenly distributed in the depth direction from the surface to the inside in the cladding layer. Here, the bubbles in the liquid fluid are initially solidified during the laser scanning process. Trapped and retained in the cladding layer to form pores; the Lorentz force adjustment method is as follows: a direct current parallel to the surface of the substrate is passed through the substrate until the end of the scan, and the current density is 0-10 ⁶ A/m ^2. At the same time, place the substrate in the gradient steady-state magnetic field until the end of scanning, so that the magnetic field strength on the surface of the molten pool is 0-2T, and the magnetic field strength decreases uniformly with the increase of the depth of the molten pool, and the gradient of the magnetic field strength decline is 0.01 ~0.06T/mm. Usually the protective gas is an inert gas, such as argon.

Further, the substrate is connected to an external power supply that can provide direct current before laser cladding to be connected.

Usually, the DC current is a steady state DC current provided by a low-voltage high-rated current battery, that is, the external power supply is a low-voltage high-rated current battery, the voltage of the low-voltage high-rated current battery is 2-6V, and the discharge capacity is 300-600Ah.

In the present invention, the mass fraction of the nickel-based powder is preferably: Ni 52.5%, Cr 15%, C 0.1%, Si 0.3%, Mn 0.3%, S 0.01%, P 0.01%, Al 0.4%, Ti 1.5%, Mo 3 %, Nb 5%, Fe 21.88%.

Still further, the magnetic field is provided by an electromagnet, and the direction of the magnetic field is parallel to the surface of the cladding pool and perpendicular to the scanning direction of the laser. The adjustment of the magnetic field gradient is realized by changing the length and/or width of the rectangular magnetic poles in contact with both sides. The width of the rectangular magnetic poles is 10mm-40mm, and the length is 80-120mm.

Furthermore, the direction of the Lorentz force is adjusted by changing the direction of the current or the direction of the magnetic field.

Specifically, for the preparation method of the controllable pore nickel-based coating, the recommended laser power is 1600W, the scanning speed is 10mm/s, the powder feeding rate is 10g/min, and the shielding gas flow rate is 20HF/min. The cladding layer forms spherical pores. According to the above operation, the diameter range of the spherical pores of the cladding layer is 5 μm to 100 μm, and the total volume of the generated pores accounts for 0.1 to 0.2% of the volume of the cladding layer, and the pores are distributed randomly. The layer morphology is good without cracks. In this solution, under the process of step B and powder conditions, the cladding layer refers to a coating layer that is melted by laser to cover the material on the surface of the substrate and forms a metallurgical bond with it.

Different from other laser coating preparation methods, this method targets pores, and the main powder and shielding gas optimization content also includes: by adjusting the Ti and C contents of the nickel-based powder to 1.5% and 0.1%, respectively, to control the The moisture content is 2%, providing raw materials for foaming to generate CO, CO ₂ and other gases, controlling the particle size (50-75μm) and sphericity (0.8-0.9) of nickel-based powder, and improving the combination of powder and moisture in the protective gas The ability to "bubble" the cladding layer, and apply Lorentz force during the nucleation and growth of the bubbles to accelerate or suppress the movement of the bubbles, thereby adjusting the number and distribution of the bubbles in the cladding layer.

Usually, the present invention adjusts the magnetic field intensity to 1-2T through step C, and the current density is 10 ⁵ -10 ⁶ A/m ² , and at the same time makes the direction of the Lorentz force perpendicular to the surface of the cladding pool, which will make The number of bubbles overflowing increases, so that the volume percentage of residual pores in the cladding layer is 0-0.1% and distributed on the upper part of the cladding layer; in this way, a nickel-based coating with no pores or very little pores can be obtained.

If we adjust the magnetic field strength in step C to 1-2T, the current density is 10 ⁵ ～10 ⁶ A/m ² , and at the same time make the direction of the Lorentz force perpendicular to the surface of the cladding pool, the number of bubbles will overflow The volume percentage of residual pores in the cladding layer is 5-20%, and they are distributed at the bottom of the cladding layer. The nickel-based coating that can be obtained in this way has more residual pores, and most of them are distributed in the lower layer of the coating.

If we adjust the magnetic field strength to 0.1-0.5T, the current density to 0-10 ⁵ A/m ² , and at the same time make the direction of the Lorentz force perpendicular to the surface of the cladding pool inward, this will reduce the energy of bubble nucleation , the number of bubbles in the cladding pool increases. At this time, the Lorentz force is small, and the drag force of the fluid dominates. The bubbles are stirred by the fluid to make the pores of the cladding layer uniform.

Specifically, the preparation method of the controllable pore nickel-based coating is as follows: the Lorentz force is generated by the mutual coupling of the magnetic field and the electric field in the cladding pool area, and the direction is perpendicular to the surface of the cladding pool and inward. Or vertically outward, by adjusting the current density value of 0-10 ⁶ A/m ² and the magnetic field value of 0-2T, the Lorentz force value ranges from 0 to 2×10 ⁶ N/m ³ , and the magnetic field gradient is adjusted from 0.01 to 0.06T/mm, so that the Lorentz force is distributed in a negative gradient from the surface to the depth direction, and the gradient of the Lorentz force decrease is 10 ² -10 ⁵ N/mm.

The inventive method has the following advantages:

1. The present invention adjusts the nickel-based powder material content (C and/or Ti content), powder characteristics and protective gas water content with the Lorentz force, and the directional Lorentz force acts indirectly on the air bubbles to adjust in physical form Pore distribution, the mechanical properties and organizational characteristics of the original coating are retained as much as possible, and coatings with different pores can be obtained.

2. The present invention adopts the gradient Lorentz force body force, which can not only increase the control ability of the key interface area of the bubble overflow on the surface of the molten pool, so as to significantly improve the control effect, but also reduce the Lorentz force on the bubble precipitation at the bottom of the molten pool process impact.

3. The present invention can affect the descending gradient of the Lorentz force by adjusting the magnitude of the direct current applied to the surface of the substrate and the strength of the magnetic field on the surface of the molten pool, thereby adjusting the pores in the nickel-based coating to meet different processing requirements. This is not only applicable to laser cladding nickel-based coatings, but also applicable to welding, laser melting and other processing forms that generate molten pools, and has a wide range of applications.

Description of drawings

Fig. 1 The working state structure diagram of the preparation device of a kind of controllable pore nickel-based coating

Fig. 2 Pore distribution in the longitudinal section of the cladding layer under the conditions of Example 1

Fig. 3 distribution diagram of pores in longitudinal section of cladding layer under the conditions of Example 2

Fig. 4 The distribution diagram of pores in the longitudinal section of the cladding layer under the conditions of Example 3

Fig. 5 distribution of pores in longitudinal section of the cladding layer under the conditions of Example 4

Fig. 6 The pore distribution diagram of the longitudinal section of the cladding layer under the condition of upward Lorentz force in Example 5 (magnetic field gradient 0.01T/mm)

Fig. 7 Distribution of air holes in the longitudinal section of the cladding layer under the condition of downward Lorentz force in Example 6 (magnetic field gradient 0.06T/mm)

Fig. 8 The pore distribution diagram of the longitudinal section of the cladding layer under the condition of upward Lorentz force in Example 7

Figure 9 Example 8 Lorentz force condition cladding layer longitudinal section uniform distribution of pores

detailed description

The present invention will be further elaborated below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the content described.

The embodiment of this case is realized by the following devices, as shown in Figure 1, the device includes: 1-laser, 2-laser transmission channel, 3-powder feeding head, 4-workpiece holder, 5-wire, 6—low voltage and high rated current power supply, 7—coil winding, 8—rectangular magnetic pole head, 9—substrate, 10—coil winding power supply.

Specific connection method: the laser 1 and the laser transmission channel 2 can be connected through a flexible optical fiber or a flying optical path, the powder feeding head 3 is coaxially combined with the laser transmission channel 2, the powder feeding head 3 is located directly above the substrate 9, and the low-voltage high-rated current power supply 6 passes through The wire 5 and the workpiece holder 4 are connected to the base body 9 , the rectangular magnetic pole head 8 is located on both sides of the base body and combined with the coil winding 7 , and the coil winding is connected to the coil winding power supply 10 .

Specific implementation method: at first base body is connected with workpiece holder, makes base body be in horizontal position, selects suitable rectangular magnetic pole head (choose shape size according to different magnetic field gradients), adjusts the relative position of double magnetic head until each pole head and base body side distance about 0.5mm. Turn on the DC power switch, adjust the current, pass the required current value into the matrix, turn on the coil winding power supply and adjust the current value, so that the pole head can generate the required magnetic field value. After the preparation is completed, laser cladding starts, and the powder feeding head cladding on the surface of the substrate according to the set trajectory, energizes and magnetizes until the cladding is completed, and the processed substrate is taken out.

Example 1

The base material of laser cladding is 316 austenitic stainless steel, which is machined into a metal sample of 100×10×10mm. Grease removal. The cladding powder is nickel-based alloy powder, and the powder is placed in a drying oven with a set temperature of 100° C. and a drying time of 60 minutes. After the powder is cooled, put it into the powder feeder, place the sample to be clad horizontally on the workbench, turn on the laser generator (the power is 1600W), the gas protection device (the protection gas is argon, the flow rate is 20HF/min, moisture content 0.05%) and powder feeder (powder feeding amount 10g/min), 10mm/s scan speed to carry out cladding according to the preset cladding trajectory. The particle size of the powder is 50-75 μm, and the sphericity is 0.8-0.9, wherein the mass fraction of the nickel-based powder is: Ni 52.5%, Cr 15%, C 0.1%, Si 0.3%, Mn0.3%, S 0.01%, P 0.01%, Al 0.4%, Ti 1.5%, Mo 3%, Nb 5%, Fe 21.88%. Fig. 2 is a distribution diagram of pores in the cladding layer under the above process conditions, the diameter ranges from 60 μm to 100 μm, and the total volume of the pores in the cladding layer is about 0.2% of the total volume of the cladding layer.

The pore distribution diagram of the longitudinal section of the cladding layer in Example 1 is shown in Figure 2.

Example 2

This example is a comparative example, and the water content in the shielding gas in Example 1 is reduced to 0.04%, and the powder chemical composition (mass fraction, %) is consistent with Example 1: Ni 52.5%, Cr 15%, C 0.1%, Si 0.3%, Mn 0.3%, S 0.01%, P 0.01%, Al 0.4%, Ti 1.5%, Mo 3%, Nb 5%, Fe 21.88%. Ensure that other process parameters are consistent with Example 1, obtain the cladding layer vertical section pore distribution diagram (shown in Figure 3), wherein the cladding layer pore shape is spherical, the diameter range is 5 ~ 10 μm, the total number of cladding layer pores The volume is about 0.05% of the total volume of the cladding layer; comparing Figure 2, it can be found that the number of pores and the diameter of the pores in the cladding layer are significantly reduced, indicating that the moisture content in the shielding gas is reduced, which reduces the oxygen content in the cladding layer and the pore content is obvious. reduce.

Example 3

This example is a comparative example. Only according to the conditions in Example 1, when the particle size of the nickel-based powder is increased to 150 μm to 180 μm, the sphericity is 0.8 to 0.9, and the laser process and powder chemical composition are kept consistent with Example 1, and the cladding layer is obtained. Pore distribution diagram in longitudinal section (shown in Figure 4). It can be seen from the figure that when the particle size increases to more than 150 μm, there are micropores on the surface of the cladding layer, and the total volume of the pores in the cladding layer is about 0.05% of the total volume of the cladding layer, indicating that the increase in particle size makes the particle surface The gas-carrying capacity is reduced, resulting in a lower porosity.

Example 4

Refer to Figure 5. This example is a comparative example. According to the conditions in Example 1, the sphericity of the nickel-based powder particles is increased to about 0.98, and the chemical composition and particle size of the powder are kept consistent with Example 1, that is, the powder particle size is 50-75 μm, and the sphericity 0.8～0.9, wherein the cladding powder chemical composition (mass fraction, %) is: Ni 52.5%, Cr 15%, C 0.1%, Si 0.3%, Mn0.3%, S 0.01%, P 0.01%, Al 0.4% , Ti 1.5%, Mo 3%, Nb 5%, Fe 21.88%. Put the powder in a drying oven, set the temperature at 100°C, and dry for 60 minutes. Ensure that other process parameters are consistent with those in Example 1, and obtain the pore distribution diagram of the longitudinal section of the cladding layer (as shown in FIG. 5 ). It can be seen from the figure that when the sphericity increases, although there are micropores, the number of pores is significantly reduced compared with Example 1. The reason is that the powder sphericity increases and the binding ability of the carrier gas decreases, which leads to changes in the content of external gas entering the molten pool. , so that the size and number of pores are reduced. Combining Examples 3 and 4, it can be obtained that when the particle size exceeds 150 μm and the sphericity is greater than 0.9, it is not conducive to "bubbling" of the cladding layer.

Example 5

Refer to Figure 6. By comparing Example 1 and Example 2, Example 1 and Example 3, and Example 1 and Example 4, it can be seen that adjusting the water content of the shielding gas and powder composition, powder sphericity and powder particle size will have a significant impact on the number and size of pores. influence, but only relying on the process, it is often difficult to control its distribution. Therefore, on the basis of the successful bubbles in Example 1, the present invention simultaneously adds Lorentz force and body force to change the equivalent buoyancy of the bubbles, so as to achieve the purpose of quantitatively regulating the distribution. . In this embodiment, the laser cladding base material is 316 austenitic stainless steel, which is machined into a metal sample of 100×10×10 mm, and the surface is cleaned with acetone after degreasing, derusting and grinding. Before laser cladding, the substrate is connected to an external power supply that can provide direct current. The direct current is a steady-state direct current, and the external power supply is a low-voltage high-rated current battery (battery specification: 6V, 600Ah).

Put the nickel-based alloy powder in a drying oven, set the temperature at 100°C, and dry for 60 minutes. After the powder is cooled, put it into the powder feeder. The chemical composition (mass fraction, %) of the alloy powder is: Ni 52.5%, Cr 15%, C 0.1%, Si0.3%, Mn 0.3%, S 0.01% , P 0.01%, Al 0.4%, Ti 1.5%, Mo 3%, Nb 5%, Fe 21.88%. The particle size of the powder is 50-75 μm, and the sphericity is 0.8-0.9. Turn on the laser generator (power is 1400W), gas protection device (argon gas flow rate is 10L/h, moisture content is 2%) and powder feeder (powder feed rate is 10g/min), and the scan speed is 7mm/s according to the preset Set the cladding trajectory for cladding. At the same time, a current density of 10 ⁶ A/m ² is passed into the substrate, the magnetic field strength on both sides of the substrate is 2T, and the gradient of the magnetic field strength drop is 0.01T/mm, and a vertical cladding molten pool surface is formed in the cladding molten pool area. The external gradient Lorentz force has a descending gradient value of 10 ⁵ N/m ⁴ from the molten pool surface to the bottom. Due to the influence of the Lorentz force, the bubbles are subjected to an additional downward force, which inhibits the upward discharge of the bubbles, and finally most of the pores are concentrated and distributed at the bottom of the cladding coating, as shown in Figure 6. The pore size range in the figure is 10-120 μm , the total volume of pores in the cladding layer is about 8% of the total volume of the cladding layer.

Example 6

Refer to Figure 7 for the distribution diagram of pores in the longitudinal section of the cladding layer. In this example, only the gradient of the magnetic field intensity drop in Example 5 is 0.06T/mm, and other laser process parameters, powder parameters, shielding gas, current and magnetic field are kept consistent with Example 5, and the pores shown in Figure 7 are obtained. Distribution. It can be seen from the figure that the pore diameter ranges from 10 to 120 μm, and the number of pores is reduced compared with that in Figure 6, and the total volume accounts for about 6% of the total volume of the cladding layer.

Example 7

Refer to Figure 8. In this example, only the direction of the Lorentz force in Example 5 is changed to be vertical to the surface of the molten pool inward, and other laser process parameters, powder parameters, shielding gas, current and magnetic field are consistent with Example 5, as shown in Figure 8 The pore distribution diagram shown. It can be seen from the figure that the number of pores is significantly reduced compared with Figures 2, 6 and 7, and a dense cladding layer is obtained, and the total volume accounts for about 0% of the total volume of the cladding layer.

Example 8

Refer to Figure 9. In this example, on the basis of Example 5, a current density of 10 ⁵ A/m ² is applied to the substrate, a magnetic field strength is 0.4T, and the gradient of magnetic field strength drop is 0.01T/mm to form a molten pool perpendicular to the direction of Lorentz force The liquid surface is inward, and its descending gradient value is 400N/mm ⁴ from the molten pool surface to the bottom. The laser cladding base material is 316 austenitic stainless steel, which is machined into a metal sample of 100×10×10 mm. The surface is degreased, derusted, and polished to Ra1.6, and then cleaned with ethanol. Put the nickel-based alloy powder in a drying oven, set the temperature at 100°C, and dry for 60 minutes. After the powder is cooled, put it into the powder feeder, the chemical composition (mass fraction, %) of the alloy powder is: Ni 52.5%, Cr 15%, C 0.1%, Si 0.3%, Mn 0.3%, S0.01% , P 0.01%, Al 0.4%, Ti 1.5%, Mo 3%, Nb 5%, Fe 21.88%, consistent with Example 1. Turn on the laser generator (power is 1400W), gas protection device (argon gas flow rate is 10L/h, moisture content is 2%) and powder feeder (powder feed rate is 10g/min), and scan speed is 10mm/s according to the preset Set up the cladding trajectory for cladding, and obtain the uniform distribution of pores as shown in Figure 9. The diameter of the pores is 10-100 μm, and the total volume of the pores accounts for about 6% of the total volume of the cladding layer.

Claims (10)

1. a preparation method for control pore Ni-based coating, comprises the steps:

A: polish, clean, scrubbing: substrate surface is carried out grinding process, until surface-brightening reaches surface roughness and is less than Ra1.6, re-uses acetone or ethanol carries out wiping and cleans surface and oil contaminant removal, and dries in ventilation；

B: laser melting coating: use coaxial powder feeding device that nickel base powder is sent into matrix surface, forms laser melting coating molten bath, successively with swashing Photoscanning carry out laser melting coating makes cladding molten bath formed bubble, by following parameter adjustment nickel base powder Ti, C content, powder diameter, Powder sphericity, protection gas in moisture and combine laser technical parameters control cladding layer pore quantity；

Described nickel base powder mass fraction is: Ni 50.0～55.0%, Cr 12.0～17.10%, C 0.08～0.2%, Si 0～0.35%, Mn0～0.35%, S 0～0.018%, P0～0.015%, Al 0.30～0.70%, Ti 1.10～ 2%, Mo 2.8～3.30%, Nb 4.75～5.50%, surplus is Fe；Described powder diameter d=50～150 μm；

Described powder sphericity is 0.6～0.9；

In described protection gas, moisture mass fraction is 0.05～2%；

It is 800～1800W that described laser technical parameters controls in laser power；Scanning speed is 6～15mm/s；Protection throughput It is 10～80HF/min；Powder sending quantity 8～20g/min；

C: Lorentz force body force couples: is formed in bubble at cladding bath described in step B, is simultaneously introduced adjustable ladder Degree Lorentz force, the bubble forming step B process carries out pore that profile adjustment forms it in cladding layer by surface extremely The inside depth direction distribution gradient or be evenly distributed；Described Lorentz force control method is: be passed through at described matrix Being parallel to the DC current of described matrix surface until the end of scan, electric current density size is 0～10⁶A/m², meanwhile, by described Matrix be placed in gradient steady magnetic field until the end of scan so that the magnetic field intensity of weld pool surface is 0～2T, magnetic field intensity with The degree of depth molten bath increases and uniformly reduces, and the gradient that magnetic field intensity declines is 0.01～0.06T/mm.

2. the preparation method of control pore Ni-based coating as claimed in claim 1, it is characterised in that: described matrix melts at laser Being connected to wait to connect coated with external power supply that is front and that can provide DC current, described DC current is steady-state DC electric current, external Power supply is the big specified electric current accumulators of low pressure.

3. the preparation method of control pore Ni-based coating as claimed in claim 1, it is characterised in that: described magnetic field is by electric magnet Thering is provided, magnetic direction is parallel with cladding weld pool surface, both perpendicular to described laser scanning direction, by changing double sided contacts Rectangular shaped poles length and or width realize magnetic field gradient regulation, the width of described rectangular shaped poles is 10mm～40mm, described square A length of the 80 of shape magnetic pole～120mm.

4. the preparation method of control pore Ni-based coating as claimed in claim 1, it is characterised in that: the side of described Lorentz force To being passed through the sense of current by change or magnetic direction is adjusted.

5. the preparation method of the control pore Ni-based coating as described in one of Claims 1 to 4, it is characterised in that described swashs Luminous power is 1600W, and laser scanning speed is 10mm/s, and powder sending quantity is 10g/min, and protection throughput 20HF/min obtains cladding Layer spherical porosity.

6. the preparation method of the control pore Ni-based coating as described in one of Claims 1 to 4, it is characterised in that: adjust described Nickel base powder in the mass fraction of C be C 0.1% or and adjustment described in nickel base powder in the mass fraction of Ti be Ti 1.5%, the moisture controlled in protection gas is 2%, provides raw material to produce CO, CO for bubbling₂Deng gas, control described powder End particle diameter d=50～75 μm, controlling described sphericity is 0.8～0.9, improves powder and the binding ability of moisture in protection gas.

7. the preparation method of the control pore Ni-based coating as described in one of Claims 1 to 4, is characterised by: step C regulation magnetic Field intensity is 1～2T, and electric current density is 10⁵～10⁶A/m², make Lorentz force direction hang down with cladding weld pool surface simultaneously Straight inwardly bubble overflows quantity to be increased, and obtains in cladding layer remaining pore percent by volume 0～0.1% and be distributed in cladding layer Top；Described cladding layer refers to covered at the material of matrix surface by laser fusion and form the painting of metallurgical binding therewith Layer.

8. the preparation method of the control pore Ni-based coating as described in one of Claims 1 to 4, is characterised by: step C regulation magnetic Field intensity is 1～2T, and electric current density is 10⁵～10⁶A/m², make Lorentz force direction hang down with cladding weld pool surface simultaneously Straight outside, bubble overflows quantity to be reduced, remaining pore percent by volume 5～20% in cladding layer, and is distributed in bottom cladding layer.

9. the preparation method of the control pore Ni-based coating as described in one of Claims 1 to 4, it is characterised in that: step C regulates Magnetic field intensity is 0.1～0.5T, and electric current density size is 0～10⁵A/m², make Lorentz force direction and cladding molten bath table simultaneously Face is perpendicularly inward so that the energy of bubble forming core reduces, and increased air bubble in described cladding molten bath, bubble is by fluid agitation effect And make cladding layer pore become uniform.

10. the preparation method of the control pore Ni-based coating as described in one of Claims 1 to 4, it is characterised in that: described Lip river Lun Zili is to intercouple generations, described Lorentz force direction and cladding weld pool surface by magnetic field and electric field in cladding molten bath zone Perpendicularly inward or vertically outside, by regulation current density value 0～10⁶A/m²With magnetic field value 0～2T so that Lorentz lorentz's force value is big Little scope is 0～2 × 10⁶N/m³, adjusting magnetic gradient 0.01～0.06T/mm so that Lorentz force is from a surface to the inside degree of depth Direction is also distributed in negative gradient, and the gradient that Lorentz force declines is 10²～10⁵N/mm⁴。