A method for tilt polishing silicon carbide ceramics based on high repetition rate femtosecond laser

Abstract

A method for obliquely polishing silicon carbide ceramics based on high repetition rate femtosecond laser comprises the following steps: firstly, the silicon carbide ceramics are cleaned, and then an optical path is constructed; the laser output by the high repetition rate femtosecond laser acts on a processing station of a three-dimensional mobile platform through a 1 / 2 wave plate, a beam splitter, a first reflector, a beam expander, a pinhole optic, a second reflector and a galvanometer; a large laser incident angle is obtained by adjusting a vibrating rotator; the silicon carbide ceramics are fixed on the processing station of the three-dimensional mobile platform; the three-dimensional mobile platform is adjusted to focus the oblique laser beam on the material surface; a computer is used to adjust the laser output to output different laser parameters; the silicon carbide ceramic sample is polished by controlling the scanning speed of the galvanometer and different moving directions of the three-dimensional mobile platform by the computer; the method adopts high repetition rate, high power and low speed and low repetition rate, low power and high speed to polish the silicon carbide ceramic surface for multiple times; and the ceramic surface after polishing has the advantages of high surface smoothness, no cracks and no holes.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon carbide ceramic processing, and in particular relates to a method for oblique polishing of silicon carbide ceramics based on high repetition rate femtosecond laser. Background Art

[0002] Silicon carbide ceramics have the advantages of good high-temperature mechanical strength, oxidation resistance and corrosion resistance, low thermal expansion coefficient, high thermal shock resistance, etc. Therefore, silicon carbide ceramics are widely used in industrial fields such as petroleum, microelectronics, chemical industry, automobile, aviation, aerospace, etc. However, due to the high brittleness and high hardness of silicon carbide ceramic materials, during the mechanical grinding process, the material is mainly removed by brittleness and fracture, and the surface of the material is very easy to cause cracks, pits, sub-surface damage and many other unacceptable defects, and the processed surface is rough, thus affecting the use function and life of silicon carbide ceramic parts. In addition, the tool will wear and break during the polishing process, increasing the manufacturing cost. When using special processing such as electric spark, chemical mechanical polishing, and ultrasonic assistance, there is still the disadvantage of low efficiency.

[0003] Laser has the advantages of good monochromaticity, good coherence, high power density, etc., and is easy to guide and combine with CNC, which is very suitable for precision micro-machining. At present, most of the laser polishing methods used in China are carried out on existing laser processing equipment. The angle between the laser and the surface plane of the processed material is 90°, and it is easy to produce heat-affected zone, recast layer, thermal stress-induced surface cracks and other problems in the air environment. Although the underwater laser polishing method of silicon carbide ceramics can solve the above problems, the laser is very easy to produce cavitation in the aqueous solution, which consumes laser energy, and the presence of cavitation will affect the propagation of the beam and reduce its polishing efficiency. Laser tilting processing technology For the current application of laser tilting processing technology, the method of tilting the workpiece is mainly used to realize the laser tilting processing. The tilting device platform used in this method is complex, and the coordinated movement requirements between the various motion axes are high. It is difficult to ensure the uniformity of the polished surface in the horizontal and vertical directions, and the operation is difficult. In addition, there is no literature on the tilting laser processing technology for the surface polishing of porous silicon carbide ceramic materials. Summary of the invention

[0004] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for tilting and polishing silicon carbide ceramics based on high-repetition-rate femtosecond laser, in which a rotating device is used to rotate the scanning galvanometer to a certain incident angle to achieve a change in the angle between the laser beam and the material plane from 10° to 20°. At the same time, the lateral scanning speed of the tilted scanning galvanometer and the longitudinal feed speed of the motion platform are controlled to work together to ensure the uniformity of processing. The method is simple to operate and has high processing efficiency.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for tilt polishing silicon carbide ceramics based on high repetition rate femtosecond laser comprises the following steps:

[0007] 1) The silicon carbide ceramic is ultrasonically cleaned with acetone, anhydrous ethanol and deionized water respectively, and then blown dry with nitrogen to obtain a clean silicon carbide ceramic sample 9;

[0008] 2) Building a femtosecond laser polishing optical path system, the optical path system includes a high repetition rate femtosecond laser 1, the laser output from the high repetition rate femtosecond laser 1 passes through a 1 / 2 wave plate 2, a beam splitter 4, and a first reflector 5 in sequence, the first reflector 5 rotates the optical path by 90°, and then the laser beam passes through a beam expander 6 and a pinhole diaphragm 7, and then enters a galvanometer 10 via a second reflector 12 to be obliquely irradiated on a processing station of a three-dimensional mobile platform 8, wherein a rotator 11 connected to the galvanometer 10 is used to adjust the inclination angle of the galvanometer 10, the high repetition rate femtosecond laser 1, the galvanometer 10, the three-dimensional mobile platform 8, the vibration rotator 11 and a computer 13 are connected, and the laser power is detected by a combination of a 1 / 2 wave plate 2, a beam splitter 4 and a power meter 3, and at the same time, the computer 13 controls the galvanometer 10 and further controls the movement speed and trajectory of the laser; the size of the light aperture is adjusted by the pinhole diaphragm 7 to obtain the radius of the ablation spot passing through the galvanometer 10;

[0009] 3) rotating the vibration rotator 11 to rotate the galvanometer 10 to a corresponding angle, that is, controlling the laser beam to have an inclined angle θ with the horizontal plane of the silicon carbide ceramic sample 9;

[0010] 4) Fix the silicon carbide ceramic sample 9 onto the three-dimensional moving platform 8, which is composed of a three-dimensional motion mechanism arranged in the X-axis direction, the Y-axis direction and the Z-axis direction. The starting position of the polishing area of ​​the silicon carbide ceramic sample 9 is provided by adjusting the X-axis and the Y-axis. The X-axis, the Y-axis and the Z-axis cooperate to adjust the laser focus on the surface of the sample silicon carbide ceramic 9;

[0011] 5) Using computer 13, adjust the output laser wavelength of high repetition rate femtosecond laser 1 to 1030nm, pulse width to 240fs, repetition rate to 25-100kHz, and laser power to 1-8W;

[0012] 6) The scanning path is planned by using the galvanometer 10 and the Y-axis of the three-dimensional mobile platform 8 to cooperate with each other, wherein the galvanometer 10 controls the width of the polishing area, the scanning path is a straight line, and the scanning in the width direction reciprocates along the X-axis direction. The processing speed and the jump speed are set to be the same, and the number of repetitions is determined by the processing area; the Y-axis of the three-dimensional mobile platform 8 controls the length of the polishing area, and the feeding speed in the length direction is determined by the track interval in the length direction, the length in the width direction, and the scanning speed;

[0013] 7) The computer 13 is used to control the parameters of the high repetition rate femtosecond laser 1. The computer 13 is also used to control the galvanometer 10 and the three-dimensional mobile platform 8 respectively, thereby controlling the movement speed and trajectory of the laser on the surface of the silicon carbide ceramic. The high repetition rate femtosecond laser with a wavelength of 1030nm is irradiated on the silicon carbide ceramic sample 9. The galvanometer 10 controls the laser to move in the X-axis direction to polish the silicon carbide ceramic.

[0014] In the step 2), the rotation angle range of the vibration rotator 11 is 0°-90° to ensure that the laser beam is incident on the processing station surface of the three-dimensional mobile platform 8 at an angle.

[0015] The tilting angle θ of step 3) is between 10° and 20°.

[0016] In the step 6), the scanning speed in the width direction is 100-800 mm / s, and the feeding speed in the length direction is 50-400 μm / s.

[0017] In the step 7), the three-dimensional mobile platform 8 is fed in the Y-axis direction, and the galvanometer 10 controls the laser to move repeatedly in the X-axis direction. The three-dimensional platform 8 and the galvanometer 10 cooperate to control the speed and trajectory of the laser on the surface of the silicon carbide ceramic to achieve polishing processing.

[0018] Beneficial effects of the present invention:

[0019] (1) The optical system is easy to build and can achieve laser material removal without any other auxiliary conditions. It can effectively reduce or eliminate cracks and hole defects, eliminate oxide particles deposited on the surface, and obtain a good silicon carbide ceramic surface.

[0020] (2) The method of polishing with an inclined high-repetition-rate femtosecond laser has no tool wear and high processing efficiency. Under the irradiation of an inclined high-repetition-rate femtosecond laser, the laser beam diameter in the Y-axis direction increases, the spot area increases, and the deposition of laser energy inside the holes, cracks and other defects on the original surface of the silicon carbide ceramic material is reduced, and the light filling effect caused by multiple reflections of the laser inside the hole is eliminated. At the same time, the horizontal component of the laser-induced shock wave increases, which is conducive to removing debris and nanoparticles and other deposits generated by the interaction between the femtosecond laser and the material in the polishing area, so that a smooth surface without cracks and holes can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the optical path of the present invention.

[0022] Figure 2 This is a schematic diagram of the principle of polishing silicon carbide ceramics according to the present invention.

[0023] Figure 3 This is the rendering of the unpolished silicon carbide ceramic of Example 1 of the present invention.

[0024] Figure 4 This is a diagram showing the effect of vertically polishing silicon carbide ceramics in Example 1 of the present invention.

[0025] Figure 5 This is a diagram showing the effect of polishing silicon carbide ceramics at an inclination angle of 10° in Example 1 of the present invention.

[0026] Figure 6 This is a diagram showing the effect of polishing silicon carbide ceramics at an inclination angle of 20° in Example 2 of the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0028] Embodiment 1, a method for tilt polishing silicon carbide ceramics based on high repetition rate femtosecond laser, comprising the following steps:

[0029] 1) A 30×30 mm silicon carbide ceramic was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water respectively, and then dried with dry nitrogen to obtain a clean silicon carbide ceramic sample 9;

[0030] 2) Build a femtosecond laser polishing optical system, refer to Figure 1 The optical path system includes a high repetition rate femtosecond laser 1. The laser output from the high repetition rate femtosecond laser 1 passes through a 1 / 2 wave plate 2, a beam splitter prism 4, and a first reflector 5 in sequence. After the first reflector 5 turns the optical path 90°, the laser beam passes through a beam expander 6 and a pinhole optic 7, and then enters a galvanometer 10 through a second reflector 12 to be tilted and irradiated on a processing station of a three-dimensional mobile platform 8. The vibration rotator 11 connected to the galvanometer 10 is mainly used to adjust the tilt angle of the galvanometer 10. The rotation angle of the vibration rotator 11 The range of the angle is 0°-90°, so as to ensure that the laser beam is incident obliquely on the processing station of the three-dimensional mobile platform 8; the high repetition rate femtosecond laser 1, the galvanometer 10, the three-dimensional mobile platform 8, the vibration rotator 11 and the computer 13 are connected, and the laser power is detected by combining the 1 / 2 wave plate 2, the beam splitter 4 and the power meter 3. At the same time, the computer 13 controls the galvanometer 10 and then controls the movement speed and trajectory of the laser. The size of the light hole is adjusted by the small hole diaphragm 7, and the ablation spot radius through the galvanometer 10 is 40μm;

[0031] 3) rotating the vibration rotator 11 to rotate the galvanometer 10 to a corresponding angle, and controlling the laser beam and the horizontal plane of the silicon carbide ceramic sample 9 to have an inclined angle θ of 10° to 20°, and 10° in this embodiment;

[0032] 4) Fix the silicon carbide ceramic sample 9 onto the three-dimensional moving platform 8, which is composed of a three-dimensional motion mechanism arranged in the X-axis direction, the Y-axis direction and the Z-axis direction. The starting position of the polishing area of ​​the silicon carbide ceramic sample 9 is provided by adjusting the X-axis and the Y-axis. The X-axis, the Y-axis and the Z-axis cooperate to adjust the laser focus on the surface of the sample silicon carbide ceramic 9;

[0033] 5) Using computer 13, adjust the output laser wavelength of high repetition rate femtosecond laser 1 to 1030nm, pulse width to 240fs, repetition rate to 100kHz, and power to 6W;

[0034] 6) The scanning path is planned by using the galvanometer 10 and the Y-axis of the three-dimensional mobile platform 8 to cooperate with each other, wherein the galvanometer 10 controls the width of the polishing area, the scanning path is a straight line with a width of 10 mm, and the scanning speed in the width direction is set to 200 mm / s, which represents the overlap rate of the laser line spot, to achieve reciprocating motion along the X-axis direction, and the processing speed and the jump speed are set to be the same, and the number of repetitions is determined by the processing area; the Y-axis of the three-dimensional mobile platform controls the length of the polishing area, which is 10 mm. To ensure that the track intervals are equal, the feed speed in the length direction is determined by the track interval in the length direction, the length in the width direction and the scanning speed, and the feed speed is 100 μm / s, refer to Figure 2 ;

[0035] 7) Using computer 13 to control the parameters of high repetition rate femtosecond laser 1, and using computer 13 to control the galvanometer 10 and the three-dimensional moving platform 8 respectively, and then controlling the speed and trajectory of the laser on the surface of silicon carbide ceramic, irradiate the high repetition rate femtosecond laser of 1030nm wavelength on the silicon carbide ceramic sample 9, refer to Figure 2 The galvanometer 10 controls the laser to move in the X-axis direction, while the Y-axis of the three-dimensional moving platform 8 moves rightward to polish the silicon carbide ceramic.

[0036] Beneficial effects of this embodiment: Figure 3 , the surface morphology of the unpolished silicon carbide ceramic sample in Example 1, the original surface of the material has defects such as cracks and holes, and the distribution is mixed and intertwined; Figure 4 , Figure 4 The surface morphology of the silicon carbide ceramic sample obtained after vertical polishing is rough, with a large number of holes, particles and debris deposits; Figure 5 , Figure 5 The surface morphology of the silicon carbide ceramic sample obtained after laser polishing in Example 1 at an inclination angle of 10° is shown in FIG. 1 . The surface quality of the material is significantly improved, and defects such as cracks and holes on the original surface of the material disappear, obtaining a smooth material surface.

[0037] Example 2: In step 3) of Example 1, the angle between the laser beam and the horizontal plane of the silicon carbide ceramic sample 9 is changed to 20°; the other steps remain unchanged, and the processing effect is referenced to Figure 6 In this embodiment, the surface of the silicon carbide ceramic material is smoother and free of defects such as holes and cracks. The deposits on the surface of the material are significantly removed, and the roughness is reduced to 0.2 microns.

[0038] In Example 3, the angle between the laser beam and the horizontal plane of the silicon carbide ceramic sample 9 in step 3) of Example 1 is changed to 15°; in step 5), the laser parameters are set to a repetition rate of 50 kHz and a power of 3 W; in step 6), the scanning speed in the width direction is changed to 100 mm / s, and the feed speed in the length direction is changed to 50 μm / s; the other steps remain unchanged, and the polishing effect is similar to that in Example 1.

[0039] In Example 4, the angle between the laser beam and the horizontal plane of the silicon carbide ceramic sample 9 in step 3) of Example 1 is changed to 15°; the laser power in step 5) is 8W; the scanning speed in the width direction in step 6) is changed to 800mm / s, and the feed speed in the length direction is changed to 400μm / s; the other steps remain unchanged, and the polishing effect is similar to that in Example 1.

Claims

1. A method for tilt polishing silicon carbide ceramics based on high repetition rate femtosecond laser, characterized in that: The following steps are involved: 1) The silicon carbide ceramic was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water respectively, and then dried with nitrogen to obtain a clean silicon carbide ceramic sample (9); 2) constructing a femtosecond laser polishing optical path system, the optical path system comprising a high repetition rate femtosecond laser (1), the output laser of the high repetition rate femtosecond laser (1) sequentially passes through a 1 / 2 wave plate (2), a beam splitter prism (4), and a first reflector (5), the first reflector (5) rotates the optical path by 90°, and then the laser beam passes through a beam expander (6) and a pinhole aperture (7), Then, the light enters the galvanometer (10) through the second reflector (12) and is tilted to illuminate the processing station of the three-dimensional mobile platform (8), wherein the rotator (11) connected to the galvanometer (10) is used to adjust the tilt angle of the galvanometer (10), the high repetition rate femtosecond laser (1), the galvanometer (10), the three-dimensional mobile platform (8), the vibration rotator (11) and the computer (13) are connected, and the laser power is detected by combining a 1 / 2 wave plate (2), a beam splitter (4) and a power meter (3), while the computer (13) controls the galvanometer (10) and further controls the movement speed and trajectory of the laser; the size of the light aperture is adjusted by the pinhole diaphragm (7) to obtain the radius of the ablation spot passing through the galvanometer (10); 3) rotating the vibration rotator (11) to rotate the galvanometer (10) by a corresponding angle, that is, controlling the laser beam to have an inclined angle θ with the horizontal plane of the silicon carbide ceramic sample (9); 4) fixing the silicon carbide ceramic sample (9) onto a three-dimensional moving platform (8), wherein the three-dimensional moving platform (8) is composed of a three-dimensional motion mechanism arranged in the X-axis direction, the Y-axis direction and the Z-axis direction, providing a starting position of the polishing area of ​​the silicon carbide ceramic sample (9) by adjusting the X-axis and the Y-axis, and adjusting the laser focus on the surface of the silicon carbide ceramic sample (9) by cooperating with the X-axis, the Y-axis and the Z-axis; 5) using a computer (13) to adjust the high repetition rate femtosecond laser (1) to output a laser wavelength of 1030 nm, a pulse width of 240 fs, a repetition rate of 25-100 kHz, and a laser power of 1-8 W; 6) using the galvanometer (10) and the Y-axis of the three-dimensional mobile platform (8) to coordinately plan the scanning path, wherein the galvanometer (10) controls the width of the polishing area, the scanning path is a straight line, the scanning in the width direction reciprocates along the X-axis direction, the processing speed and the jump speed are set to be the same, and the number of repetitions is determined by the processing area; the Y-axis of the three-dimensional mobile platform (8) controls the length of the polishing area, and the feed speed in the length direction is determined by the track interval in the length direction, the length in the width direction and the scanning speed; 7) The computer (13) is used to control the parameters of the high repetition rate femtosecond laser (1), and the computer (13) is used to control the galvanometer (10) and the three-dimensional moving platform (8) respectively, thereby controlling the movement speed and trajectory of the laser on the surface of the silicon carbide ceramic. The high repetition rate femtosecond laser with a wavelength of 1030 nm is irradiated on the silicon carbide ceramic sample (9), and the galvanometer (10) controls the laser to move in the X-axis direction to polish the silicon carbide ceramic.

2. The method according to claim 1, characterized in that: In the step 2), the rotation angle range of the vibrating rotator (11) is 0°-90°, so as to ensure that the laser beam is incident obliquely on the processing station surface of the three-dimensional mobile platform (8).

3. The method according to claim 1, characterized in that: In step 2), the ablation spot radius is 30-50 μm.

4. The method according to claim 1, characterized in that: The tilting angle θ in step 3) is between 10° and 20°.

5. The method according to claim 1, characterized in that: In the step 6), the scanning speed in the width direction is 100-800 mm / s, and the feeding speed in the length direction is 50-400 μm / s.

6. The method according to claim 1, characterized in that: In the step 7), the three-dimensional moving platform (8) is fed in the Y-axis direction, and the galvanometer (10) controls the laser to move repeatedly in the X-axis direction. The three-dimensional moving platform (8) and the galvanometer (10) cooperate to control the movement speed and trajectory of the laser on the surface of the silicon carbide ceramic, thereby achieving polishing processing.

7. The method according to claim 1, characterized in that The following steps are involved: 1) 30×30 mm silicon carbide ceramics were ultrasonically cleaned with acetone, anhydrous ethanol and deionized water respectively, and then dried with dry nitrogen to obtain a clean silicon carbide ceramic sample (9); 2) constructing a femtosecond laser polishing optical path system, the optical path system comprising a high repetition rate femtosecond laser (1), the output laser of the high repetition rate femtosecond laser (1) sequentially passes through a 1 / 2 wave plate (2), a beam splitter prism (4), and a first reflector (5), the first reflector (5) rotates the optical path by 90°, and then the laser beam passes through a beam expander (6) and a pinhole aperture (7), Then, the laser beam enters the galvanometer (10) through the second reflector (12) and is tiltedly irradiated onto the processing station of the three-dimensional mobile platform 8, wherein the vibration rotator (11) connected to the galvanometer (10) is used to adjust the tilt angle of the galvanometer (10), and the rotation angle range of the vibration rotator (11) is 0°-90°, so as to ensure that the laser beam is tiltedly incident onto the processing station of the three-dimensional mobile platform (8); the high repetition rate femtosecond laser (1), the galvanometer (10), the three-dimensional mobile platform (8), the vibration rotator (11) and the computer (13) are connected, and the laser power is detected by a combination of a 1 / 2 wave plate (2), a beam splitter (4) and a power meter (3), while the computer (13) controls the galvanometer (10) and further controls the movement speed and trajectory of the laser, and adjusts the light aperture size through the pinhole aperture (7), so that the ablation spot radius through the galvanometer (10) is 40 μm; 3) rotating the vibration rotator (11) to rotate the galvanometer (10) by a corresponding angle, and controlling the laser beam to have an inclined angle θ of 20° with the horizontal plane of the silicon carbide ceramic sample (9); 4) fixing the silicon carbide ceramic sample (9) onto a three-dimensional moving platform (8), wherein the three-dimensional moving platform (8) is composed of a three-dimensional motion mechanism arranged in the X-axis direction, the Y-axis direction and the Z-axis direction, providing a starting position of the polishing area of ​​the silicon carbide ceramic sample (9) by adjusting the X-axis and the Y-axis, and adjusting the laser focus on the surface of the silicon carbide ceramic sample (9) by cooperating with the X-axis, the Y-axis and the Z-axis; 5) Using a computer (13), adjust the high repetition rate femtosecond laser (1) to output a laser wavelength of 1030 nm, a pulse width of 240 fs, a repetition rate of 100 kHz, and a power of 6 W; 6) The scanning path is planned by using the galvanometer (10) and the Y-axis of the three-dimensional mobile platform (8) to cooperate with each other, wherein the galvanometer (10) controls the width of the polishing area. The scanning path is a straight line with a width of 10 mm. The scanning speed in the width direction is set to 200 mm / s, which represents the overlap rate of the laser line spot. Reciprocating motion along the X-axis direction is achieved. The processing speed and the jump speed are set to be the same, and the number of repetitions is determined by the processing area. The Y-axis of the three-dimensional mobile platform controls the length of the polishing area, which is 10 mm. To ensure that the track intervals are equal, the feed speed in the length direction is determined by the track interval in the length direction, the length in the width direction and the scanning speed, and the feed speed is 100 μm / s. 7) A computer (13) is used to control the parameters of a high repetition rate femtosecond laser (1), and the computer (13) is used to control the galvanometer (10) and the three-dimensional moving platform (8) respectively, thereby controlling the speed and trajectory of the laser on the surface of the silicon carbide ceramic. A high repetition rate femtosecond laser with a wavelength of 1030 nm is irradiated on the silicon carbide ceramic sample (9), and the galvanometer (10) controls the movement of the laser in the X-axis direction. At the same time, the three-dimensional moving platform (8) is fed and moved in the Y-axis direction to polish the silicon carbide ceramic.

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