CN112570895A

CN112570895A - Processing method for aqueous medium assisted laser polishing of SiC ceramic

Info

Publication number: CN112570895A
Application number: CN202011554057.8A
Authority: CN
Inventors: 李�浩; 袁根福; 杨富理
Original assignee: Jiangnan University
Current assignee: Jiangnan University
Priority date: 2020-12-24
Filing date: 2020-12-24
Publication date: 2021-03-30

Abstract

The invention relates to the application field of special processing, in particular to a processing method for polishing SiC ceramics by using aqueous medium assisted laser, which can reduce or eliminate the defects of a heat affected zone, thermal cracks and the like, can weaken oxidation reaction by isolating air by using an aqueous medium, and ensures the processing quality, and comprises the following steps: (1) determining the size and the processing position of the SiC ceramic; (2) determining laser system process parameters of laser polishing SiC ceramic and covering layer parameters of an aqueous medium; (3) determining a laser scanning speed and a scanning path; (4) the water medium is used as an auxiliary layer to uniformly cover the surface of the SiC ceramic, and the laser is polished according to a set scanning path.

Description

Processing method for aqueous medium assisted laser polishing of SiC ceramic

Technical Field

The invention relates to the application field of special processing, in particular to a processing method for polishing SiC ceramics by using aqueous medium assisted laser.

Background

Silicon carbide (SiC) ceramic belongs to one of structural ceramics, and has excellent performances of high temperature resistance, thermal shock resistance, high hardness, corrosion resistance, oxidation resistance, wear resistance, creep resistance, thermal stability, high thermal conductivity, high electric conductivity and the like. However, as a hard and brittle material difficult to machine, it is difficult to machine SiC ceramics into desired ceramic parts having high surface smoothness and dimensional accuracy by conventional machining techniques, for example, conventional machining has the defects of severe tool wear and rough machining surface, while special machining using electric spark, ultrasonic waves, etc. still has the disadvantage of low efficiency.

Laser processing refers to a process of irradiating laser on a workpiece, converting highly concentrated light energy into heat energy, melting and evaporating a processed part, and removing a material, and is known as a universal processing tool. The laser polishing technology is one of laser processing technologies, which makes laser polishing of materials which are difficult to process, such as SiC ceramics, become practical, but because laser processing mainly utilizes high-density energy to process materials through melting, evaporation and spraying, a serious heat affected zone and inevitable residual thermal stress and microcracks exist on the surface of the materials, and the SiC ceramics can also generate oxidation reaction with oxygen in the air under the action of high temperature to generate an oxidation layer, so that the processing quality of the SiC surface is influenced.

Disclosure of Invention

Based on the problem that the processing quality of the SiC surface is influenced in the process of directly polishing SiC ceramic by laser, the processing method of the SiC ceramic by the aid of the aqueous medium and the laser can reduce or eliminate the defects of a heat affected zone, thermal cracks and the like, and the oxidation reaction can be weakened by isolating air from the aqueous medium, so that the processing quality is ensured.

The technical scheme is as follows: a processing method for polishing SiC ceramic by using aqueous medium to assist laser is characterized by comprising the following steps:

(1) determining the size and the processing position of the SiC ceramic;

(2) determining laser system process parameters of laser polishing SiC ceramic and covering layer parameters of an aqueous medium;

(3) determining a laser scanning speed and a scanning path;

(4) the water medium is used as an auxiliary layer to uniformly cover the surface of the SiC ceramic, and the laser is polished according to a set scanning path.

It is further characterized in that the laser scanning path is in a shape of a "bow" or concentric circles.

No auxiliary gas is applied during polishing.

After the method is adopted, only laser and water are involved in the processing process, the cooling buffer effect of the aqueous medium can effectively reduce or eliminate the laser processing defects such as a heat affected zone, thermal cracks and the like, the oxidation reaction can be weakened by isolating air from the aqueous medium, the SiC ceramic is polished by using the technology of assisting laser polishing by the aqueous medium, a polished surface with good surface quality is processed on the SiC surface, and the processing quality is ensured.

Drawings

FIG. 1 is a diagram showing the structure of an apparatus required for the processing method of the present invention, wherein: 1. A machining workbench; 2. SiC ceramic plate 3, laser head; 4. A laser beam; 5. a reflective mirror; 6. a water tank; 7. an aqueous medium;

FIG. 2 is a flow chart of a processing method for aqueous medium assisted laser polishing of SiC ceramics according to the present invention;

FIG. 3 is a "bow" shaped path of laser scan path as embodied by the invention, wherein: 1. a scan path starting point; 2. a scan path end point;

FIG. 4 illustrates a laser scanning path implemented in the present invention as a concentric path, wherein: 1. a scan path starting point; 2. end point of scan path.

Detailed Description

In order to clearly show the technical scheme of the invention, the invention is further described with reference to the accompanying drawings.

Referring to fig. 2, a processing method of aqueous medium assisted laser polishing SiC ceramic includes:

(1) determining the size and the processing position of the SiC ceramic:

the size of the SiC ceramic plate is selected to be 25x25x1mm, and the SiC ceramic plate is fixed on a reasonable position on the workbench, so that the processing position is exactly the right center of the SiC ceramic plate.

(2) Determining laser system process parameters and covering layer parameters of an aqueous medium of the laser polishing SiC ceramic:

and (3) normally starting a laser switch, wherein the laser is an ML-MU-W20H infrared fiber laser with the maximum power of 50W, the pulse width is 100ns, the input power of the laser is adjusted to 40W, and the pulse repetition frequency is adjusted to 40 kHz.

Setting parameters of a covering layer of the aqueous medium, mainly adjusting the thickness of the water layer to repeatedly verify different polishing effects of the SiC ceramic, and finally confirming that the thickness of the water layer is 0.8mm and the water layer uniformly covers the surface of the SiC ceramic.

(3) Determining laser scanning speed and scanning path:

the scan rate of the laser polish is selected such that the scan path is "arcuate" as shown in fig. 3, or the scan path is concentric as shown in fig. 4. The "zigzag" scan path of fig. 3 is specifically: and after the laser longitudinally passes through a straight line, transversely feeding the laser by a line spacing, continuously scanning the laser, and repeating the bow-shaped path until the scanning is finished to form a rectangular polishing surface. The concentric circular path of fig. 4 is specifically: and scanning the laser from outside to inside, transversely feeding the laser by one line spacing after the outermost ring is scanned, and continuously scanning the laser, and repeating the steps until the circular polishing surface is formed after the scanning is finished.

(4) The water medium is used as an auxiliary layer to uniformly cover the surface of the SiC ceramic, and the laser is polished according to a set scanning path

And adding water which is 0.8mm higher than the SiC ceramic chip into the water tank, starting a laser, and polishing the laser according to a set scanning path.

And finishing the processing process.

To further understand the effect of process parameters on the surface quality of polished SiC ceramics, an orthogonal test approach can be used. Through the orthogonal test method, the test times are greatly reduced, and the optimal SiC ceramic quality scheme can be obtained.

The orthogonal test adopts three levels and five factors for testing, wherein the factor 1 is laser power with the sizes of 20W, 16W and 12W, the factor 2 is laser frequency with the sizes of 20KHZ, 30KHZ and 40KHZ, the factor 3 is scanning speed with the sizes of 5mm/s, 10mm/s and 15mm/s, the factor 4 is scanning interval with the sizes of 15 mu m, 20 mu m and 25 mu m, and the factor 5 is scanning times with the times of 1, 2 and 3.

And selecting an orthogonal table, carrying out 18 times of experiments, measuring the roughness of the polished SiC ceramic surface by using a roughness measuring instrument after the experiments are finished, setting the roughness of the polished surface as an experiment result, and optimizing a group of optimal process parameters by visually analyzing and considering the number of defects of the polished surface.

The polishing processing of the SiC ceramic surface can be conveniently finished through the steps, the generation of a heat affected zone and cracks is reduced through the arrangement of the aqueous medium, and the polishing quality of the SiC ceramic surface is improved.

The invention has the following beneficial effects:

(1) the experimental system is simple in construction device and low in cost, only laser and water are involved in the processing process, the environment is not polluted, and the micro-morphology is a smooth groove surface after single laser scanning.

(2) The cooling buffer effect of the aqueous medium can effectively reduce or eliminate laser processing defects such as a heat affected zone, thermal cracks and the like, and the oxidation reaction can be weakened by isolating air from the aqueous medium.

(3) By using the technology of polishing SiC ceramic by using water medium-assisted laser, a polished surface with good surface quality can be processed on the SiC surface.

Claims

1. A processing method for polishing SiC ceramic by using aqueous medium to assist laser is characterized by comprising the following steps:

(1) determining the size and the processing position of the SiC ceramic;

(3) determining a laser scanning speed and a scanning path;

2. The processing method of the aqueous medium assisted laser polishing SiC ceramic according to claim 1, wherein the laser scanning path is a bow-shaped or concentric circle.

3. The processing method of aqueous medium assisted laser polishing of SiC ceramics according to claim 1, wherein no assist gas is applied during polishing.