SiC ceramics have excellent physical and chemical properties, and have been extensively researched and used in electronics, optics, semiconductor and other fields. However, due to its high strength, high hardness and other characteristics, the conventional processing of SiC ceramics faces a series of challenges. Laser processing has become an effective processing technology due to its unique advantages. In this paper, the single pulse ablation tests of SiC ceramic with different powers were performed by using infrared femtosecond laser. The single pulse ablation threshold of SiC ceramic was calculated by using equivalent diameter method and equivalent area method, and the influence of laser power on the depth of the ablation hole was discussed. The results show that when the repetition frequency is 25kHz and the wavelength is 1035nm, the laser ablation values calculated by the equivalent diameter method and the equivalent area method are 0.3454 J/cm2 and 0.3268 J/cm2, respectively. Within a certain laser power range or reaching a certain ablation hole depth, the ablation hole depth augments with the increment of laser power. Beyond a specified laser power range, the hole depth decreases with the increment of laser power due to the effect of plasma shielding and recasting layer.
Silicon carbide fiber reinforced silicon carbide ceramic matrix composites (CMC-SiCf/SiC) have been widely used in aerospace and other fields due to their excellent properties such as high hardness, oxidation resistance and high temperature resistance. Different from the traditional machining methods, laser processing technology has great application prospects in CMC-SiCf/SiC. In this paper, the single-pulse ablation test and multi-pulse cumulative ablation test of CMC-SiCf/SiC were carried out by femtosecond laser at different powers with a wavelength of 1035 nm. A series of experiments were designed to process the ablation pits on the material surface. The diameter of the ablation pits was observed by laser confocal microscope. The variations of the ablation threshold of CMC-SiCf/SiC surface under different pulse energies and pulse numbers were studied. The results show that the multi-pulse ablation threshold of CMC-SiCf/SiC decreases with the increase of pulse number, and there is a significant cumulative effect. The multi-pulse ablation threshold of CMC-SiCf/SiC is mainly related to the number of pulses, which is determined by two parameters: accumulation factor and single-pulse ablation threshold. The single-pulse ablation threshold of CMC-SiCf/SiC is 1.1914 J/cm2, and the accumulation factor is 0.6245. In femtosecond laser processing, the pulse accumulation effect has a significant influence on the ablation of hard and brittle material CMC-SiCf/SiC. This study can provide technical guidance for process optimization.
With the rapid development of advanced manufacturing technology, the market demand for high-precision functional curved surface parts is increasing. The traditional processing technology has shortcomings in the precision forming of curved parts, especially in the processing of functional and fine structures. Laser processing has the characteristics of non-contact, high precision, and controllable energy, which makes it have special advantages in machining highperformance surfaces. This paper analyzed the application requirements of high-precision complex surface processing and the differences between traditional surface processing methods and curved surface laser processing. A five-axis CNC laser processing technology for curved surfaces was proposed. At the same time, the digital modeling and laser machining simulation verification of a typical curved surface part were carried out by using this processing technology. The result proves the effectiveness of the digital processing flow of curved surface laser machining and provides a digital solution for laser machining of high-precision and complex curved surfaces.
Nickel-based superalloy (DZ411) is widely used in the manufacture of high-temperature components in the aerospace field due to its excellent physical and mechanical properties, such as high-temperature resistance, oxidation resistance, and corrosion resistance. Laser polishing can improve the surface quality and service performance of nickel-based superalloy materials. In this paper, a new type of multi-beam coupling laser based conventional laser is used to process the nickelbased superalloy materials. The processing experiments of nickel-based superalloy were carried out by changing laser power, scanning speed, and scanning pitch. Then the polished surfaces were observed and detected by laser confocal microscope. The results show that the surface of nickel-based superalloy materials has certain regularity with the variations of process parameters. Under these experimental parameters, surface roughness (Ra) decreases first and then increases with the increase of laser power, scanning speed, and scanning pitch. The minimum Ra of the polished surface is 1.06 μm under the process parameter combinations of laser power of 1W, scanning speed of 400 mm/s, and scanning pitch of 20 μm. The maximum valley depth (Rv) and the maximum height (Rz) of profile first decrease and then increase with the increase of laser power or scanning speed. However, Rv and Rz had a little rate of fluctuation with the increase of scanning pitch. The laser polishing process involves the dynamic time-varying absorption mechanism of the coupled laser energy by polymorphic materials, and it is accompanied by complex physical processes such as material melting, gasification, and re-condensation. When Ra is relatively low, a clear corrugated structure appears on the machined surface. This research work can provide process data support for optimizing the polishing process parameters of nickel-based superalloys and expand the laser processing types.
Due to the characteristics of high hardness, wear resistance, corrosion resistance, excellent thermal shock resistance, and low thermal expansion coefficient, Si3N4 ceramics are widely used in aerospace, national defense, electronic and electrical, mechanical, chemical, and other fields. In this paper, the grooving experiments of Si3N4 ceramics were carried out by using a novel dual-beam coupled nanosecond pulse laser, and the influence of laser power and scanning speed on the surface morphology and geometric size of grooves were studied. The results show that the laser power has a significant effect on the surface morphology and geometric size of grooves. With the increase of laser power, the laser power density augments, and the width and depth of grooves increase. The groove width and groove depth first increase and then decrease with the increase of scanning speed, and both the groove width and depth reach the maximum value at scanning speed of 800 mm/min.
Stainless steel has the characteristics of high temperature resistance, corrosion resistance, oxidation resistance and good welding performance. This work was studied the static ablation experiment of a new type of beam-coupled nanosecond laser to explore the changes of the main parameters of the laser, such as frequency and power, on the ablation aperture, hole depth, ablation area roughness and ablation morphology of stainless steel. The low-frequency 1 kHz and highfrequency 10 kHz were used to irradiate stainless steel to conduct a comparative analysis of the same frequency and different single pulse energy, and a comparative analysis of the same power and different frequencies. The influence of laser energy density and repetition frequency on the morphology of the processed microstructures was investigated. The ablation morphology of stainless steel becomes more severe with the increase of single pulse energy, and the ablation pore depth and pore size increase with the increase of single pulse energy.
The laser polishing process of metal materials has been extensively studied. This paper proposes a new type of beam-coupled laser polishing method to study the surface quality of polished stainless steel when the power and frequency change, and the changes of the surface roughness and topography with the laser power and frequency were analyzed. Under the condition of power 0.5W and frequency 10Khz, as the feed speed changes from 200mm/min to 1200mm/min, the surface roughness first decreases, then slightly increases. The single pulse energy decreases, and the surface roughness first increases and then decreases with increasing of the frequency from 10kHz to 20kHz. With low repetition frequency and single pulse energy, the surface roughness is significantly reduced to 0.19μm at the process parameters of 2.0W, 10Khz, and 600mm/min. Under the specific process parameters, the processed surface has a color change similar to that caused by surface quenching treatment. The surface material absorbs more laser light, and the processed surface microstructure changes. By adjusting the process parameters, the polishing quality can be improved. It is proved that the beam-coupled laser polishing of stainless steel is an effective polishing method.
The coupled nanosecond laser processing system was used for processing 6061 aluminum alloy in this paper. At first, we explored the relationship between laser processing parameters, such as laser power, laser repetition frequency, as well as scanning speed, and the processed surface quality for 6061 aluminum alloy plate sample. The optimal laser parameters were determined by the experiment of the flat plate sample processing, and then the paths of laser processing were designed and planned on the aluminum alloy with curved surface to explore the influence of curvature on the surface quality. The results show that the new processing technology of coupled nanosecond laser polishing could obtain good surface quality. The optimal laser processing parameters are average laser power of 5W, scanning speed of 500mm/min, and repetition frequency of 10kHz, which could reduce the surface roughness by 43%. In addition, the surface quality of the aluminum alloy is closer to the original surface as the curvature increased. And the convex surface has a lower surface roughness than the concave surface because the spot shape is different at different curvature positions. The coupled laser polishing process provides theoretical and technological support for the high-quality machining of 6061 aluminum alloy in this study.
Due to excellent properties such as high hardness, high temperature resistance, corrosion resistance and low thermal conductivity, siliconnitrideceramicsare widely used in aerospace, moldand semiconductor fields. This paper studied the material removal characteristics of fixedpoint laser ablation and microgrooving of silicon nitride ceramics in the cross-coupling energy domain after laser beam splitting and combining. When using nanosecond laser for fixed point ablation, the effect of defocus on the surface characteristics of laser ablation was analyzed. When processing surface microgrooves in different directions, the influence of the directional effect of the spatial characteristics of the coupled energy domain on the processing quality was studied. By test and analysis of the surface morphology characteristics of silicon nitride ceramics, the results show thatthe change of the defocus affects the processing depthwhen a fixed point is ablatedin the cross-coupling energy domain. Thedirection effect of microgroove processing has a more significant effect on the surface characteristics.
Aluminum alloy has the advantages of high strength, corrosion resistance and good toughness, so it is widely used in aerospace, automotive manufacturing, and other fields. Laser processing has the advantages of controllable energy, high energy density, wide range of material adaptation, no contact, almost no cutting force, clean and environmentally friendly, etc. Moreover, the complex features and micro structure functionalization of components can be solved by laser processing. The oblique incidence of the laser will reduce the processing depth of beam waist from the geometric level. And the resulting space vector effect can introduce new processing mechanisms. The processing result could be improved by adjusting the vector effect with important value and novelty. In this paper, the mechanism and forming surface of 7075 be processed by nanosecond laser with different positive inclination angles under the same basic process parameters. It is shown that laser milling can effectively reduce the surface roughness of 7075. The result shows that the when the laser inclination angle (θ) is in the range of 0°~40°, the surface roughness of the machined surface decreases with the increase of θ, and the roughness can be as small as 0.15 μm. When 40° < θ ≤ 60°, the machined surface roughness increases with the increase of θ, but it is still significantly lower than the original surface roughness. The main reason for this phenomenon is that the projected area, shape, and energy distribution of the laser beam waist in the processing area are affected by the laser beam lead angle. The energy distribution affects the material removal mechanism: cladding, vaporization, or sublimation. And under the positive inclination angle, the processed surface is first irradiated and then processed for the second time by the laser beam. The relative posture of laser beam and workpiece is conducive to the discharge of slag, thus improving the processing quality. And pointed out that within the range of experimental conditions, θ = 40° is the optimal inclination angle, because the processed surface has the least undulation and the highest flatness. Moreover, this research has guiding significance for improving the surface quality of laser processing.
In order to realize the laser precision machining of ceramics, the influence of some basic machining parameters (power, scanning speed, scan path spacing, and incidence angle) on the machining effect was studied. The experimental results show that the selection of reasonable processing parameters can obtain better processing quality and processing efficiency. The material removal rate firstly increases, and then decreases with the increment of the incident angle, which indicates that the incident angle has a great influence on the utilization of laser energy. In addition, the machined surface roughness is better after machining at high scanning speed and low power.
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