CN113118631B - A Method Based on Laser Shock for Thick Coating Removal and Substrate Surface Modification - Google Patents

Abstract

The invention provides a method based on laser shock to realize the removal of thick coating and the modification and modification of the surface of the substrate, comprising the following steps: using laser etching to etch the coating into partitions; using short pulse laser shock to etch the partitions After the coating, the shock wave generated by the interaction between the short-pulse shock laser and the coating surface is transmitted from the coating to the substrate, and the impedance at the interface is mismatched due to the difference in impedance between the coating and the substrate, and the intensity of the reflected stretching wave at the interface exceeds that of the interface. The bonding strength makes the coating peel off; at the same time, the shock wave generated passes through the interface and acts on the surface of the substrate to strengthen the surface of the substrate. The invention achieves the purpose of peeling off the thick coating by impacting the area to be removed; at the same time, the laser impact will induce the plastic deformation of the substrate, realize the strengthening of the substrate surface and form the surface texture morphology, and roughen the substrate surface, which is beneficial to improve The strength of the bond between the new coating and the substrate.

Description

A Laser Shock-Based Removal of Thick Coatings and Surface Modification of Substrates method

technical field

The invention relates to the field of advanced laser manufacturing or the field of laser shock technology, in particular to a method for realizing thick coating removal and substrate surface modification based on laser shock.

Background technique

In engineering applications, especially the surface of many important equipment needs to be coated with thick coating. For example, aircraft skins are composed of primers, anti-corrosion paint layers, top coats, etc.; various types of equipment working in high-temperature thermal cycle conditions usually have thermal barrier coatings on the surface. Whether it is aircraft skin surface paint or thermal barrier coating, the common feature of this type of coating is thick. The total thickness of the aircraft skin surface paint layer can reach several millimeters, and the thermal barrier coating can also reach hundreds of microns. In addition, due to the harsh conditions of equipment and high safety factor requirements for such thick coatings, the bonding strength between the coating and the substrate is generally very high. After aircraft skins, tank shells, etc. have been in service for a period of time, the surface paint will have obvious or invisible damage such as peeling, cracking, and aging due to external forces, radiation, and airflow erosion. It is necessary to remove the entire or partial old paint layer , in order to apply a new coating. The thermal barrier coating on the surface of the aero-engine needs to be partially or completely removed after a period of service in order to apply a new coating. At present, chemical cleaning, sandblasting or manual grinding are used to remove thick coatings, which have problems such as environmental protection, low efficiency and substrate damage. As a new cleaning method developed rapidly in recent years, laser cleaning uses laser to interact with the object to be removed to remove the object to be removed. This method has been widely used to remove thin-layer pollutants such as rust, oxide scale, and oil stains. The mechanism of laser removal of objects to be removed is: using the extremely high peak power density beam of short pulse or ultrashort pulse laser to act on the fog to be removed , so that it reaches the vaporization point, and finally vaporizes to remove the mist to be removed. The advantage of this type of method is that the object to be removed can be removed precisely. The disadvantage of this type of method is that the removal efficiency is low, and there is a risk of directly acting on the matrix and damaging the matrix. This limits the application of laser cleaning methods based on gasification ablation mechanism in large-area engineering applications and major engineering equipment.

For the laser cleaning technology of aircraft skin, people have also tried hard to explore some methods and devices for using laser cleaning to simulate the aluminum alloy paint material of aircraft skin in the laboratory. A laser method for removing the surface coating of aircraft skin proposed in the prior art can quickly and effectively remove the paint coating on the surface of aluminum skin. By adjusting the laser process parameters, including laser output average power P, laser spot size D, laser repetition The parameters such as frequency f, laser scanning line width, scanning speed v and scanning longitudinal lap spacing l are used to achieve the purpose of removing the paint layer. However, the field that this prior art involves is still mainly relying on the thermal ablation effect of laser to remove the paint layer, and the efficiency is still low.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a method based on laser shock to realize the removal of thick coating and the modification and modification of the surface of the substrate. By adopting the method of laser shock to shock the area to be removed, the coating and the substrate are matched. The impedance mismatch characteristics at the interface can achieve the purpose of peeling off the thick coating; at the same time, the laser shock will induce the plastic deformation of the substrate, realize the strengthening of the substrate surface and form the surface texture morphology, and roughen the substrate surface, which is beneficial to Improves the bond strength between the new coating and the substrate.

The present invention achieves the above-mentioned technical purpose through the following technical means.

A method for removing thick coatings and modifying substrate surfaces based on laser shock, comprising the following steps:

The coating is etched and partitioned by laser etching; the partitioned coating is etched by short-pulse laser shock, so that the shock wave generated by the interaction between the short-pulse shock laser and the coating surface is transmitted from the coating to the substrate. The difference in impedance between the layer and the substrate leads to an impedance mismatch at the interface, and the intensity of the reflected tensile wave at the interface exceeds the bonding strength of the interface, causing the coating to peel off; at the same time, the shock wave generated passes through the interface and acts on the surface of the substrate to strengthen the surface of the substrate.

Further, by increasing the magnitude of the shock wave generated by the interaction between the short-pulse shock laser and the coating surface, the shock wave passes through the interface to generate micro-pits on the surface of the substrate, which is used to increase the surface roughness of the substrate.

Further, the short pulse laser is a nanosecond laser.

Furthermore, the power density of the shock wave generated by the interaction between the short-pulse shock laser and the coating surface is on the order of 10 ⁸ W/cm ² -10 ¹¹ W/cm ² .

The beneficial effects of the present invention are:

The method for removing thick coatings and modifying the substrate surface based on laser shock in the present invention innovatively utilizes the mechanical effect of laser-induced shock waves and combines the impedance mismatch characteristics between the coating and the substrate to achieve While removing thick coatings, the substrate is strengthened and the surface of the substrate is roughened. Before the laser shock, the large-area coating is etched and partitioned by laser etching to ensure the controllable spalling area and coating removal process. Compared with conventional gasification ablation removal, the method of exfoliation to remove thick coating has unique advantages of high removal efficiency and good removal effect. Coupled with the use of laser etching partitions, the coating peeling process is controllable, and it is easy to combine with intelligent control. In addition, the method can simultaneously strengthen the surface of the substrate and form micro pits, thereby increasing the surface strength of the substrate and the bonding force between the sprayed new coating and the surface of the substrate. Therefore, this method is especially suitable for the removal of thick coatings, and it also has the effect of modifying the surface of the substrate.

Description of drawings

Fig. 1 is a schematic diagram of the method for realizing thick coating removal and substrate surface modification based on laser shock according to the present invention.

Figure 2 is the results of the experimental removal of the coating in the embodiment, Figure 2a is the peeled coating and the exposed substrate, Figure 2b is a cross-sectional view of the coating, and Figure 2c is the effect of coating peeling.

1-coating; 2-substrate; 3-short pulse laser; 4-etching trench; 5-laser shock spot; 6-scanning path; 7-exfoliating coating.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

In describing the present invention, it is to be understood that the terms "central", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "axial", The orientation or positional relationship indicated by "radial", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description , rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and thus should not be construed as limiting the invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be interpreted as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrally connected; it may be mechanically connected or electrically connected; it may be directly connected or indirectly connected through an intermediary, and it may be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

As shown in Figure 1, the method for realizing thick coating removal and substrate surface modification modification based on laser shock according to the present invention comprises the following steps:

Etching and partitioning the coating 1 by laser etching;

Use the short pulse laser 3 to impact the etched partitioned coating, so that the shock wave generated by the interaction between the short pulse laser 3 and the surface of the coating 1 is transmitted from the coating 1 to the substrate, and the interface is caused by the difference in impedance between the coating 1 and the substrate 2. The impedance at the interface does not match, and the intensity of the reflected tensile wave at the interface exceeds the bonding strength of the interface, causing the coating 1 to peel off; at the same time, the shock wave generated passes through the interface and acts on the surface of the substrate 2 to strengthen the surface of the substrate. By increasing the size of the shock wave generated by the interaction between the short-pulse laser 3 and the surface of the coating 1, the shock wave passes through the interface to generate micro pits on the surface of the substrate 2, which is used to increase the surface roughness of the substrate. The roughened substrate surface is conducive to improving the bonding strength between the new coating and the substrate during the subsequent spray coating process. The short pulse laser is a nanosecond laser. The power density of the shock wave generated by the short-pulse shock laser interacting with the coating surface is on the order of 10 ⁸ W/cm ² -10 ¹¹ W/cm ² .

Example

Coating removal is performed on a workpiece with a thickness of 300 μm ceramic coating 1 and a substrate 2 of stainless steel plate structure.

A Nd ³⁺ : YAG laser with a wavelength of 1064nm, a pulse width of 15ps, a power of 10W, a repetition rate of 500KHz, and a scanning speed of 3000mm/s was used to etch an etching groove with a depth of about 300μm on the coating 1 4. Etching the groove 4 to divide the area to be removed, and each area ranges from 0.01 mm ² to 0.09 mm ² .

Using Nd ³⁺ : YAG laser under the conditions of output power 100W, repetition frequency 1Hz, laser shock spot 5 diameter 4mm, overlap rate 50%, adopt zigzag scanning path 6 for laser shock in partitioned area. The coating in the partition is peeled off from the substrate 2 under the action of laser shock to form a peeled coating 7 . The peeling area is shown in the dotted line area in Figure 2a, and the coating in the solid line area has been separated from the substrate, but has not fallen off. The workpiece is tilted at 45° to shoot, as shown in Figure 2b, the section of the coating can be clearly seen. Figure 2c shows the exfoliated coating.

It should be understood that although this description is described according to various embodiments, not each embodiment only includes an independent technical solution, and this description of the description is only for clarity, and those skilled in the art should take the description as a whole , the technical solutions in the various embodiments can also be properly combined to form other implementations that can be understood by those skilled in the art.

The series of detailed descriptions listed above are only specific descriptions for feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiment or All changes should be included within the protection scope of the present invention.

Claims (2)

1. A method based on laser shock to realize thick coating removal and substrate surface modification modification, is characterized in that, comprises the steps: The coating is etched and partitioned by laser etching; the partitioned coating is etched by short-pulse laser shock, so that the shock wave generated by the interaction between the short-pulse shock laser and the coating surface is transmitted from the coating to the substrate. The difference in impedance between the layer and the substrate leads to an impedance mismatch at the interface, and the intensity of the reflected tensile wave at the interface exceeds the bonding strength of the interface, causing the coating to peel off; at the same time, the shock wave generated through the interface acts on the surface of the substrate to strengthen the surface of the substrate; By increasing the size of the shock wave generated by the interaction between the short-pulse laser and the coating surface, the shock wave passes through the interface to produce micro-pits on the substrate surface, which is used to improve the surface roughness of the substrate; the short-pulse shock laser interacts with the coating surface. The power density of the shock wave is on the order of 10 ⁸ W/cm ² -10 ¹¹ W/cm ² . 2. The method for realizing thick coating removal and substrate surface modification based on laser shock according to claim 1, characterized in that, the short-pulse laser is a nanosecond laser.

Images