CN116555757A - Method for Reducing Reflectivity in Laser Cladding of Copper Alloy Substrate - Google Patents

Abstract

The invention discloses a method for reducing reflectivity during laser cladding of a copper alloy matrix, which comprises the following steps: 1) Roughening a target surface of a given copper alloy workpiece; 2) After cleaning the target surface, coating volatile glue on the target surface; 3) Spreading nickel-base alloy powder on the target surface to completely cover the target surface; 4) Shaking off nickel-base alloy powder which is not adhered and drying to form a transition layer; 5) And preparing a target coating on the transition layer. The method according to the invention is relatively low in power consumption and relatively high in efficiency.

Description

Method for Reducing Reflectivity in Laser Cladding of Copper Alloy Substrate

technical field

The invention relates to a method for reducing reflectivity during laser cladding of a copper alloy substrate.

Background technique

Pure copper and its alloys are metal materials with high reflectivity. In specific industrial applications, the application range of copper alloys is much higher than that of pure copper, such as brass, bronze, etc., which are essentially copper alloys. However, whether it is pure copper or copper alloy, if it has a clean surface and the surface precision is higher than IT7, its surface reflectance is usually greater than or equal to 40%. It is well known that the laser cladding process requires that under the thermal effect of the laser, for example, a molten state is generated between the coating and the copper alloy substrate. In other words, the part absorbed by the coating should be enough to melt the surface of the copper alloy, and the reflected part It can almost cause the surface of the copper alloy to melt, and the light intensity of the reflected part is also large enough to easily cause damage to the objects and equipment irradiated by the reflected light.

In view of this, as the Chinese patent document CN107868955A proposes a method for preparing a laser-enhanced coating on the surface of a copper crystallizer (hereinafter referred to as a workpiece), in order to reduce the laser reflection intensity on the workpiece surface during coating preparation, before preparing the coating, first A middle transition layer is prepared on the surface of the workpiece. The specific method is to use electroplating to electroplate or brush-plate a pure nickel layer or a nickel-based alloy layer on the surface of the workpiece after the surface of the workpiece is cleaned, and then use laser cladding to remelt the electroplating layer to ensure that the electroplating layer is penetrated and thus Make the laser remelted layer form a reliable metallurgical connection with the copper base of the mold.

The bonding strength of the electroplating layer is relatively low, so the Chinese patent document CN107868955A proposes to use laser remelting technology to make a metallurgical connection between the electroplating layer and the surface of the workpiece. It should be noted that the electroplating solution required for the preparation of the electroplating layer is not simply an electroplating solution containing metal ions in the electroplating layer, but also contains many other types of metal ions or additives, many of which are environmental pollutants, and The working hours of electroplating are generally longer. In addition, for workpieces, not all surfaces need to be electroplated, such as copper shells, usually only the outer surface needs to be coated, and electroplating needs to immerse the workpiece in the electroplating solution, which will inevitably result in waste of plating and workpieces. Dimensional (other surfaces that do not require coating) control issues.

In addition, the power consumption and cost of electroplating itself are relatively high. Generally, additional cleaning and drying are required after electroplating, and the overall working hours are relatively long.

Contents of the invention

The purpose of the present invention is to provide a relatively low power consumption and relatively high efficiency method for reducing reflectivity during laser cladding of a copper alloy substrate.

In an embodiment of the present invention, a method for reducing reflectivity during laser cladding of a copper alloy substrate is provided, the method comprising the following steps:

1) roughen the target surface of a given copper alloy workpiece;

2) After cleaning the target surface, apply volatile glue on the target surface;

3) Sprinkle nickel-based alloy powder on the target surface to completely cover the target surface;

4) Shake off the unadhered nickel-based alloy powder and dry to form a transition layer;

5) Prepare the target coating on the transition layer.

Optionally, the nickel-based alloy is Ni25 or self-fluxing nickel-based alloy powder.

Optionally, the self-fluxing nickel-based alloy powder is Ni-B-Si alloy powder.

Optionally, the Ni25 powder is a spherical alloy powder with a particle size of 150-300 mesh.

Optionally, the composition of Ni25 in terms of mass percentage is: C0.5%, Cr15%, Si2.5%, B1.8, Al0.5%, Fe7%, and the balance is Ni.

Optionally, in step 4), before shaking off the unadhered nickel-based alloy powder, the target surface needs to be completely covered with the nickel-based alloy powder for no less than 2 minutes.

Optionally, the method for roughening the target surface is to roughen the target surface with 200-grit sandpaper.

Optionally, the volatile glue is prepared by mixing vinyl alcohol and water in a ratio of 10g:20ml, and the water content is deionized water.

Optionally, the drying method in step 4) is to place the copper alloy workpiece after shaking off the unattached nickel-based alloy powder into a drying oven at a drying temperature of 200°C and a drying time of 120 minutes.

Optionally, after step 4) is dried, the copper alloy workpiece is taken out and naturally cooled to room temperature.

In the embodiment of the present invention, firstly, the target surface of the copper alloy workpiece is roughened. At this time, the reflectivity of the target surface itself will decrease, and it will also help the adhesion of other materials. Then brush the volatile glue on the target surface, spread the nickel-based alloy powder on the volatile glue, shake off the excess nickel-based alloy powder, and dry to obtain a relatively stable transition layer, so that the thickness of the obtained transition layer is relatively uniform . The target coating is then prepared on the transition layer. In this process, the efficiency is relatively high, and when the target coating is prepared by cladding, the transition layer is also clad, and a metallurgical connection is formed at the same time, the efficiency is relatively high, and the overall energy consumption is reduced. At the same time, the metallurgical connection has better bonding firmness than the electroplating layer.

Description of drawings

FIG. 1 is a flowchart of a method for preparing a transition layer in an embodiment.

Fig. 2 is a schematic diagram of the transition layer cladding structure in an embodiment.

Fig. 3 is an electron microscope image of a coating prepared on a copper alloy substrate in a test example.

Figure 4 is a comparative view of the morphology of wear scars on the substrate and the coating in a test example, where a is the electron microscope photo of the substrate wear scars, and b is the coating wear scar electron microscope photo.

In the figure: 1. Copper alloy matrix, 2. Ni25 alloy powder, 3. Transition layer.

Implementation

Compared with other alloys, nickel-based alloys are darker in color, in other words, their reflectivity is relatively low under the same precision state. At the same time, the layer formed by the nickel-based alloy powder distribution does not have a smooth surface, but the reflection of light is a diffuse reflection characteristic. In the embodiment of the present invention, it is equivalent to the preparation of a coating with the nickel-based alloy powder as the substrate. .

It can be seen that after the coating is prepared, the excess nickel-based alloy powder is easy to remove because it is only adhered by the volatile glue.

The embodiments of the present invention focus on reducing the reflectivity of laser cladding when preparing the copper alloy substrate coating. The mechanism can be found in Chinese patent document CN107868955A, which will not be repeated here. But it should be noted that, in the embodiments of the present invention, focus on how to prepare the intermediate transition layer, such as the transition layer 3 shown in Figure 2, and how to prepare the coating, then only a brief description, those skilled in the art should have a clear understanding.

For the transition layer 3, it only needs to be able to effectively reduce the reflectivity of the copper-based alloy surface. Therefore, the transition layer 3 can be very thin, in other words, it only needs to be able to cover the target surface of the copper-based alloy substrate.

Correspondingly, under the condition of adding a relatively thin transition layer 3 , the laser cladding has a relatively low impact on the laser cladding, and the coating and the transition layer 3 can achieve integral laser cladding.

The following describes the basic steps of the method for reducing reflectivity during laser cladding of copper alloy substrates. The basic steps include four basic steps: roughening, gluing, powder distribution, and drying. Each step can assist other steps, such as roughening , often need simple cleaning after beating, and this cleaning can be to brush off the particulate matter formed by beating, or clean up in other ways, if washing with water, you need to clean up the water stains, and in a preferred embodiment Air dry, for this, the following basic steps are explained one by one.

First of all, it should be known that the surface of the prepared coating is not necessarily the entire surface of the copper alloy workpiece, but usually a part of the outer surface of the copper alloy workpiece. Note that the layer that needs to be prepared for the coating is the coating surface. For the surface formed by the transition layer, it is recorded as the target surface, which can be slightly larger than the coating surface, for example, each side is wider than 3D~10D, where D is the spot diameter during laser cladding. For example, if the spot diameter is 1mm, the target surface is 3~10mm wider than the coating surface on each side.

Regarding the roughening step, mechanical roughening is preferably used, and chemical etching may also be used, wherein chemical etching is not the preferred method because the environmental friendliness of chemical etching is relatively poor.

Mechanical roughening includes machine roughening and manual roughening, such as sanding with a belt machine or manual roughening with sandpaper. Those skilled in the art can choose according to the batch size. For example, when the batch is relatively small or when the sample is produced, you can It is preferred to use manual roughening, and if the batch is relatively large, it is preferable to use mechanical roughening.

Whether using a belt machine or sandpaper, the corresponding sand particle size can be the same, for example, 200 mesh. Since it is sanding, the particle size of the sand should not be too small, so it should not be lower than 150 mesh, but it should not be too large, otherwise It will damage the target surface, so the particle size of the sand should not be larger than 300 mesh.

The main purpose of roughening is to make the target surface rough, so as to improve the adhesion of nickel-based alloy powder on the target surface.

After that is cleaning, which mainly removes the particles attached to the target surface, as mentioned above. In order to ensure that it is clean, mechanical cleaning can be done first, such as wiping with a towel, and then cleaning with absolute ethanol. Absolute alcohol can effectively remove organic matter on the target surface, and avoid such as grease from affecting the coating. Binding force.

For example, absolute ethanol is relatively volatile and can be evaporated in a short period of time. If deionized water is used, it is preferable to further dry it by, for example, air drying, so as to improve the efficiency of the process.

After cleaning the target surface, apply volatile glue on the target surface; for example, the glue formed by mixing polyvinyl alcohol powder with water, the ratio is 10g: 20ml, the water chooses deionized water, and the polyvinyl alcohol powder is added into the water. Just mix well.

Then apply the volatile glue on the target surface by brushing, and the thickness of the formed glue layer is very thin. From the point of view of suitability, the transition layer 3 does not need to be too thick, and only needs to have a certain degree of shielding. , that is, it is sufficient to cover the surface of the copper alloy.

Then carry out the powder distribution. The powder distribution is carried out by dusting. The powder is naturally attached by the volatile glue. The amount of adhesion is affected by the thickness of the glue layer, and it will not be too much. Generally, it will form a layer with a thickness of 0.5~1mm. The powder layer, obviously the powder layer is a nickel-based alloy powder layer.

Based on the uniform brushing of volatile glue, the spread of nickel-based alloy powder can completely cover the target surface; in view of the fact that in order to ensure complete coverage of the target surface, the amount of spread should be excessive. Finally, shake off the excess nickel-based alloy powder to reduce the amount of free nickel-based alloy powder, so that the transition layer 3 before cladding is relatively stable, thereby facilitating the formation of the coating.

Regarding nickel-based alloy powder, eutectic nickel-based alloy is preferably used. Eutectic nickel-based alloy is a standard term used to define nickel-based alloy powder formed by adding an appropriate amount of B and Si to nickel alloy powder. There are relatively many types , such as Ni-B-Si alloy powder, Ni-Cr-B-Si alloy powder, Ni-Cr-B-Si-Mo, Ni-Cr-B-Si-Mo-Cu, high-molybdenum nickel-based self-fluxing alloy Powder, high chromium-molybdenum nickel-based self-fluxing alloy powder, Ni-Cr-W-C-based self-fluxing alloy powder, high-copper self-fluxing alloy powder, tungsten carbide dispersed nickel-based self-fluxing alloy powder, etc.

More preferably, Ni-B-Si alloy powder is selected as the nickel-based alloy powder.

Correspondingly, the eutectic nickel-based alloy has a low melting point, which is conducive to forming a metallurgical bond between the transition layer 3 and the copper alloy substrate 1 and the coating.

In some embodiments, nickel-based alloy powder is preferably nickel-25 alloy powder. The composition of Ni25 in terms of mass percentage is: C0.5%, Cr15%, Si2.5%, B1.8, Al0.5%, Fe7%, and the balance is Ni.

In order to make such as Ni25 alloy powder 2 combine relatively closely, before shaking off the free nickel-based alloy powder, it is necessary to completely cover the target surface with the nickel-based alloy powder and let it rest for no less than 2 minutes, so that for example Ni25 alloy powder 2 and Volatile glue binds relatively tightly.

It is obvious that the volatile glue should be basically evaporated when the coating is prepared. For this reason, before the coating is prepared, most of the volatile glue is volatilized by forced drying, and the remaining volatile glue is mixed with the nickel base. The alloy powders are tightly bonded, and combine with nickel-based alloy powders to form a transition layer 3 .

The main method of forced drying to volatilize the volatile glue is to shake off the unadhered nickel-based alloy powder and place the copper alloy workpiece in a drying oven at a drying temperature of 200°C and a drying time of 120 minutes.

Since the drying temperature is not high, natural cooling is preferably used for cooling after forced drying.

In order to verify the coating quality after the transition layer 3 is added, the Ni60+WC coating is taken as an example to illustrate the following. In the selected Ni60+WC coating, the mass fraction ratio of Ni60 to WC is 4:1.

The working parameters of the selected laser are: laser power 1400W, powder feeding rate 6.5L/min, lap rate 40, spot diameter 1mm, laser scanning speed 300mm/min.

Ni25 is selected as the nickel-based alloy powder for the transition layer, and the volatile glue used is made by mixing polyvinyl alcohol powder and water at a ratio of 10g:20ml.

The thickness of the powder layer was 0.7 mm.

Figure 3 is an electron micrograph of the section of the prepared coating. It can be seen in the figure that although there is a transition layer (the middle layer in the figure, the bottom layer in the figure is the copper alloy base layer, and the top layer is the coating), it can be seen that , Metallurgical bonding has been formed, and there are no obvious pores and cracks.

Figure 4 is the friction and wear test of the coating prepared by taking Ni60+WC coating as an example. Using GCr15 as the abrasive part, the loading force is 50N, the frequency is 5Hz, and the friction and wear time is 1h, to prove the performance of the coating. The morphology after friction and wear is observed under the scanning electron microscope. It can be observed that the friction and wear width of the substrate is much larger than that of the coating, and the substrate has formed a large area of metal extrusion accumulation and peeling. The main friction and wear mechanism is Fatigue wear; while there are only a few peeling and shallow furrows on the surface of the coating, the wear mechanism is fatigue wear and abrasive wear. The comparison between the two shows that the friction and wear performance of the coating is higher than that of the substrate. At the same time, the coating meets the strength of the metallurgical connection and can cause the friction and wear conditions of the substrate to peel off, and does not cause the peeling of the coating. In other words, after adding the transition layer Under certain conditions, the coating and the substrate still have the bonding ability of metallurgical connection.

Claims (10)

1. a method for reducing reflectivity during laser cladding of a copper alloy substrate, characterized in that, the method may further comprise the steps: 1) roughen the target surface of a given copper alloy workpiece; 2) After cleaning the target surface, apply volatile glue on the target surface; 3) Sprinkle nickel-based alloy powder on the target surface to completely cover the target surface; 4) Shake off the unadhered nickel-based alloy powder and dry to form a transition layer; 5) Prepare the target coating on the transition layer. 2. The method according to claim 1, wherein the nickel-based alloy is Ni25 or self-fluxing nickel-based alloy powder. 3. The method according to claim 2, characterized in that the self-fluxing nickel-based alloy powder is Ni-B-Si alloy powder. 4. The method according to claim 2, wherein the Ni25 powder is a spherical alloy powder with a particle size of 150 to 300 mesh. 5. the method according to claim 4 is characterized in that, described Ni25 composition by mass percent is: C0.5%, Cr15%, Si2.5%, B1.8, Al0.5%, Fe7% , and the balance is Ni. 6. The method according to claim 1, 4 or 5, characterized in that, in step 4), before shaking off the unattached nickel-based alloy powder, the target surface needs to be completely covered with the nickel-based alloy powder and left to stand The time is not less than 2 minutes. 7. The method according to claim 1, characterized in that, the method for roughening the target surface is to roughen the target surface by using 200 mesh sandpaper. 8. The method according to claim 1, wherein the volatile glue is formed by mixing vinyl alcohol and water in a ratio of 10g:20ml, wherein the water level is deionized water. 9. The method according to claim 1, characterized in that the drying method in step 4) is to place the copper alloy workpiece after shaking off the unadhered nickel-based alloy powder into a drying oven at a drying temperature of 200°C , The drying time is 120min. 10. The method according to claim 9, characterized in that, after step 4) drying, the copper alloy workpiece is taken out and then cooled naturally to room temperature.