Processing method of C / SiC fiber reinforced ultra-high-temperature ceramic micron-sized interface

Abstract

The invention relates to a processing method of a C / SiC fiber reinforced ultra-high-temperature ceramic ultra-micron interface. In order to solve the problem that existing C / SiC fiber-reinforced ultra-high-temperature ceramics cannot realize micron-order interface preparation, double-laser-beam time sequence ultra-pulse laser polishing is adopted, the surface roughness of the fiber-reinforced ultra-high-temperature ceramics is controlled by controlling double-pulse delay time, and in the laser processing process of the C / SiC fiber-reinforced ultra-high-temperature ceramics, the surface roughness of the C / SiC fiber-reinforced ultra-high-temperature ceramics is controlled. A reasonable water medium is selected as a cooling medium, laser repetition frequency is selected, control over the surface roughness of the fiber-reinforced ultra-high-temperature ceramic is achieved, finally, the C / SiC fiber-reinforced ultra-high-temperature ceramic is achieved, and the surface roughness reaches the micron level.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical processing, and in particular to a processing method for a C / SiC fiber reinforced ultra-high temperature ceramic micron-level interface. Background Art

[0002] Studies have shown that the roughness of the structural surface has a great influence on the interface resistance and aerodynamic heat. As a surface structural thermal material, C / SiC fiber reinforced ultra-high temperature ceramics have a large number of applications. Therefore, the research on micron-level processing technology of C / SiC fiber reinforced ultra-high temperature ceramics has important application value.

[0003] At present, the public literature mainly focuses on the research of micron-level interfaces of metal materials. When the metal surface is polished by laser, the surface metal volatilizes and a good finish can be obtained. The present invention is aimed at the processing of C / SiC fiber reinforced ultra-high temperature ceramic interface. When conventional polishing means are used, micron-level holes will still exist on the surface. The processing technology of micron-level interface is still blank. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for processing the micron-level interface of C / SiC fiber reinforced ultra-high temperature ceramics, specifically a laser removal processing method for the micron-level interface of C / SiC fiber reinforced ultra-high temperature ceramics, which realizes micron-level processing of the surface of C / SiC fiber reinforced ultra-high temperature ceramics.

[0005] The purpose of the present invention can be achieved by the following scheme:

[0006] The present invention provides a surface laser processing method for fiber-reinforced ultra-high temperature ceramics, the processing method comprising the following steps:

[0007] Double laser beam sequential ultra-pulse laser polishing is used for fiber-reinforced ultra-high temperature ceramics. The surface roughness of the fiber-reinforced ultra-high temperature ceramics can be controlled by controlling the double-pulse laser frequency and delay time.

[0008] As an embodiment of the present invention, the fiber-reinforced ultra-high temperature ceramic is a C / SiC fiber-reinforced ultra-high temperature ceramic. The C / SiC fiber-reinforced ultra-high temperature ceramic of the present invention has a relatively high hardness, and large-scale ceramic material removal requires laser processing. The processing of micron-level interfaces cannot be achieved through the commonly used surface subtractive technology. However, conventional laser polishing can only remove but not repair holes. The C / SiC fiber-reinforced ultra-high temperature ceramic of the present invention is achieved using dual laser beam sequential ultra-pulse laser polishing technology.

[0009] As an embodiment of the present invention, in dual laser beam sequential ultra-pulse laser polishing, the repetition rate of the laser frequency is 20%-80%, preferably 55%-65%, and more preferably 60%. When the C / SiC fiber reinforced ultra-high temperature ceramics are ultra-precision processed, the laser frequency, when the repetition rate is 60%, the micron-level processing effect of the surface of the C / SiC fiber reinforced ultra-high temperature ceramics is better, and the surface roughness of the fiber reinforced ultra-high temperature ceramics can be controlled by frequency selection. Dual lasers can achieve removal and repair effects. If the repetition rate is too low, it can only play a removal role, and cannot play a polishing and repair effect.

[0010] Laser pulse energy in water will cause laser-induced cavitation. The cavitation expands and contracts near the surface of the material and then bursts, generating a huge shock wave pressure. Due to the different thermal expansion coefficients between the ceramic matrix and the coating, the impact of the cavitation will cause interface delamination, coating peeling, cracks and other phenomena on the surface of the material (conventional metal interfaces and non-layered structure surfaces do not have this problem). Increasing the repetition rate will increase the rate of cavitation generation and increase the chance of small cavitations aggregating into large cavitations. However, underwater laser-induced cavitation, when the material collapses near the wall, generates shock waves that can drive the flow of water, carry the particles generated during the processing away from the processing area, reduce the deposition of melt particles, residues and fragments, and improve the polishing effect. The present invention controls the laser repetition frequency appropriately (repetition frequency 55%-65%) so that the generated cavitation can carry the particles away from the processing area without damaging the material surface.

[0011] In addition, the presence of too many cavitations causes the light beam to deflect, seriously affecting the stable propagation of the light beam, causing the material to absorb the laser energy unevenly and holes to appear on the surface of the material.

[0012] As an embodiment of the present invention, in the dual laser beam sequential ultra-pulse laser polishing, the delay time is 90-110ps, preferably 100ps. Under this delay time, the plasma concentration decreases, the second pulse heats the plasma, and then melts the material surface again, thereby achieving the effect of flattening, and the surface quality of the large delay time is better than that of the single pulse. In the selection of lasers, dual-pulse lasers and reasonable laser delay time selection are beneficial to the surface finish quality of C / SiC fiber reinforced ultra-high temperature ceramics.

[0013] As an embodiment of the present invention, the cooling medium in the dual laser beam sequential ultra-pulse laser polishing is water. In the laser processing process, it is necessary to select a reasonable cooling medium. The present invention, through a large number of experimental effect comparisons, shows that the cooling medium water has a better cooling effect in the ultra-precision processing of C / SiC fiber-reinforced ultra-high temperature ceramics.

[0014] As an embodiment of the present invention, the roughness of the polished fiber-reinforced ultrahigh temperature ceramic is 0.5-1.5 μm, preferably 1 μm.

[0015] The present invention has the following beneficial effects:

[0016] (1) The C / SiC fiber-reinforced ultra-high temperature ceramic ultra-precision processing technology adopts dual laser beam timing ultra-pulse laser polishing to control the surface roughness of the fiber-reinforced ultra-high temperature ceramic by controlling the double pulse delay time;

[0017] (2) The C / SiC fiber reinforced ultra-high temperature ceramic ultra-precision processing technology selects reasonable cooling medium, laser frequency and other parameters during laser processing to control the surface roughness of the fiber reinforced ultra-high temperature ceramic, and finally realizes C / SiC fiber reinforced ultra-high temperature ceramic with a surface roughness of micron level. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0019] Figure 1 Schematic diagram of the structure of C / SiC fiber reinforced ultra-high temperature ceramics;

[0020] Figure 2 Schematic diagram of the surface structure of C / SiC fiber reinforced ultra-high temperature ceramics with different laser delays;

[0021] Figure 3 Vertical underwater laser polishing of C / SiC fiber reinforced ultra-high temperature ceramic composites at different repetition rates, where a is 60% repetition rate, b is 80% repetition rate, c is 88% repetition rate, and d is 96% repetition rate. DETAILED DESCRIPTION

[0022] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0023] Example 1

[0024] This embodiment provides a method for processing a fiber-reinforced ultra-high temperature ceramic micron-level interface, the processing method comprising the following steps:

[0025] Double-pulse laser is used to polish C / SiC fiber-reinforced ultra-high temperature ceramics using double laser beam timing ultra-pulse laser. The laser frequency repetition rate is 60%. By controlling the double-pulse delay time, the surface roughness of the fiber-reinforced ultra-high temperature ceramics can be controlled.

[0026] Table 1

[0027] Laser Mode Delay time / ps Cooling medium Attached photos Single laser / water Figure 2 Dual Laser 1 water Figure 2 Dual Laser 20 water Figure 2 Dual Laser 100 water Figure 2

[0028] from Figure 2 It can be found that when the delay time is 100ps, the surface smoothness of C / SiC fiber reinforced ultra-high temperature ceramics is optimal.

[0029] Example 2

[0030] This embodiment provides a method for processing a C / SiC fiber reinforced ultra-high temperature ceramic micron-level interface, the processing method comprising the following steps:

[0031] Basically the same as Example 1, the delay time is 100 ps, ​​the difference is in Table 2, the cooling medium is water, and the effect of repetition frequency on the surface processing of C / SiC fiber reinforced ultrahigh temperature ceramics is studied.

[0032] Table 2

[0033]

[0034] like Figure 3 As shown, when the laser repetition rate is 60%, the microstructure is better than that of the laser repetition rate of 96%.

[0035] like Figure 1 As shown, the structural schematic diagram of the conventional C / SiC fiber reinforced ultra-high temperature ceramic used in the embodiment of the present invention is as shown in Figure 1 As shown, the interface roughness of conventional C / SiC fiber reinforced ultra-high temperature ceramics is about 100um, and after processing, the roughness reaches 30-50μm.

[0036] like Figure 2 As shown in the figure, when the double-pulse laser delay time is greater than 10ps and less than 90ps, the absorption of the second pulse energy is suppressed due to the excessive concentration of the plasma, thereby increasing the surface roughness; when the delay time is 90-110ps, the plasma concentration decreases, the second pulse heats the plasma, and then melts the material surface again, thereby achieving the effect of smoothing processing, and the surface quality with a large delay time is better than that of a single pulse. In the selection of lasers, double-pulse lasers and reasonable laser delay time selection are beneficial to the interface smoothness quality of C / SiC fiber reinforced ultra-high temperature ceramics.

[0037] Laser-induced cavitation occurs as the energy of the laser pulse increases. The cavitation expands and contracts near the surface of the material and then bursts, generating a huge shock wave pressure. Due to the different thermal expansion coefficients between the ceramic substrate and the coating, interface delamination, coating peeling, cracks and other phenomena occur on the surface of the material. Increasing the repetition rate will increase the rate of cavitation generation and increase the chance of small cavitations agglomerating into large cavitations. The presence of cavitations causes the light beam to deflect, seriously affecting the stable propagation of the light beam, causing uneven absorption of laser energy by the material and the appearance of holes. However, underwater laser-induced cavitation, the shock wave generated when the material collapses near the wall can drive the flow of water, carry the particles generated during the processing away from the processing area, and reduce the deposition of molten particles, residues and debris. The present invention controls the laser repetition rate appropriately so that the generated cavitation can carry the particles away from the processing area without damaging the surface of the material. Figure 3 As shown in ad (the upper figure is 500 μm in scale, the lower figure is 100 μm in scale), the present invention can obtain a smooth processed surface without delamination, cracks and holes by optimizing laser processing parameters. The laser repetition rate is 60%, and the microscopic morphology is better than the laser repetition rate of 96%.

[0038] The thermal conductivity of water is higher than that of air. Underwater laser processing can effectively eliminate the thermal effect of laser and avoid the formation of recast layer on the surface of the material. In addition, under the action of laser, the aqueous solution and silicon carbide react chemically, further improving the processing quality. Using medium water as the processing medium for C / SiC fiber reinforced ultra-high temperature ceramics is conducive to improving the quality of interface finish. Lasers are prone to self-focusing effect underwater.

[0039] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A surface laser processing method for fiber-reinforced ultra-high temperature ceramics, characterized in that: The surface laser processing method comprises the following steps: Dual laser beam sequential ultra-pulse laser polishing is used for fiber-reinforced ultra-high temperature ceramics. The surface roughness of the fiber-reinforced ultra-high temperature ceramics can be controlled by controlling the dual-pulse laser frequency and delay time.

2. The surface laser processing method according to claim 1, characterized in that: The fiber-reinforced ultra-high temperature ceramic is a C / SiC fiber-reinforced ultra-high temperature ceramic.

3. The surface laser processing method according to claim 1, characterized in that: In dual laser beam sequential ultra-pulse laser polishing, the repetition rate of the laser frequency is 20%-80%.

4. The surface laser processing method according to claim 3, characterized in that: In dual laser beam sequential ultra-pulse laser polishing, the repetition rate of the laser frequency is 55%-65%.

5. The surface laser processing method according to claim 1, characterized in that: In dual laser beam sequential ultra-pulse laser polishing, the delay time is 90ps-110ps.

6. The surface laser processing method according to claim 1, characterized in that: The cooling medium used in dual laser beam sequential ultra-pulse laser polishing is water.

7. The surface laser processing method according to claim 1, characterized in that: The surface roughness of the polished fiber-reinforced ultrahigh temperature ceramics is 0.5-1.5 μm.

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