Yong Bao

High Quality Fiber Laser Cutting of Electronic Alumina Ceramics

In this paper, high quality cutting of 1 mm dense Al2O3 electronic ceramic processed by a fiber laser with spot diameter of 15 μm was reported. The narrow kerf with 30μm width was obtained with laser power of 100 W. 300 W is the laser power threshold of the kerf enlargement. Under higher laser power, the ceramics can be damage-free cut with higher cutting speed. Striation-free cutting could be achieved at 1000 W laser power with a cutting speed of 350 mm/s. The ratio of cutting speed to laser power for striation-free cutting was determined as 0.35. The black cutting surface was due to the mass tetragonal alumina induced by N2 as assist gas.

Laser crack-free cutting technique for thick and dense ceramics

A new laser crack-free cutting technique for dense ceramics with thickness of ≥ 10 mm based on beam continuous piercing full through the workpieces is presented. The techology can be concluded as a feasible tool for cutting of thick and dense ceramics in complex path, even for 3D cutting.

Parallel-axis positioning device for laser processing: Design and applications

A parallel-axis positioning device with “twice positioning” method is presented to exectly locate the laser spot at a special position on workpiece for laser macro-processing. Position accuracy of the laser spot on workpiece reaches 0.01mm.

Research on improving of cut surface quality of laser-cut fine ceramics

The influence of laser cutting process on the microstructure of recast layer and the information of striation on the cut surface of laser-cut fine ceramics was researched. On the basis of analysis on the processing mechanism and numerical simulation, the optimal cutting parameters for obtaining high quality specimens are: laser power of 200 W and 6 bar assist gas pressure for CO2 laser, while ≥750 W laser power, 1500 cm/min laser scanning speed and 8 bar assist gas pressure for fibre laser. There are two main research results were achieved: 1) High cutting quality ceramic specimen with thin and uniform recast layer and striation-free cut surface was obtained in free cutting path. 2) Fibre laser is more suitable for striation-free laser precision cutting of ceramics. The problem of low absorption rate with ceramics to fibre laser with the wavelength around 1.07 µm, i.e. alumina, can be overcome by phase change of the materials due to laser rapid heating. The black cutting surface was due to the mass tetragonal alumina induced by N2 as assist gas.The influence of laser cutting process on the microstructure of recast layer and the information of striation on the cut surface of laser-cut fine ceramics was researched. On the basis of analysis on the processing mechanism and numerical simulation, the optimal cutting parameters for obtaining high quality specimens are: laser power of 200 W and 6 bar assist gas pressure for CO2 laser, while ≥750 W laser power, 1500 cm/min laser scanning speed and 8 bar assist gas pressure for fibre laser. There are two main research results were achieved: 1) High cutting quality ceramic specimen with thin and uniform recast layer and striation-free cut surface was obtained in free cutting path. 2) Fibre laser is more suitable for striation-free laser precision cutting of ceramics. The problem of low absorption rate with ceramics to fibre laser with the wavelength around 1.07 µm, i.e. alumina, can be overcome by phase change of the materials due to laser rapid heating. The black cutting surface was due to the mass tetrag...

Nanocrystallization of Fe-Based Amorphous Alloys Fe73.5Cu1Nb3Si13.5B9 by Yb-Doped Fiber Laser Overlapping Irradiation

The paper presents a laser irradiation method for rapidly fabricating Fe-based nanocrystalline alloys using Yb-doped fiber laser with a wavelength of 1070nm by overlapping irradiation of the heated areas. The samples are annular cores rolled with 20μm-thick and 3.2mm-wide belts of amorphous alloy Fe73.5Cu1Nb3Si13.5B9 , which have internal diameter of 14 mm and external diameter of 20 mm. Every side of the samples is irradiated for 15 min by fiber laser. X-ray diffraction and transmission electron microscopy (TEM) are used for microstructure analysis and observation. The samples irradiated by a defocus beam with a diameter of 7.1mm through a lens have better soft magnetic properties than directly by an original collimating beam with a diameter of 6.7mm. The dimension of homogeneous ultrafine grains is about 10nm with a bcc α-Fe (Si), which is the foundation of the excellent soft magnetic property. Uniform laser irradiation and the appropriate laser power are necessary for optimum microstructure and soft magnetic properties.

Nanocrystallization of Fe-Based Amorphous Alloys Fe73.5Cu1Nb3Si13.5B9 by Continuous CO2 Laser Overlapping Irradiation

Continuous CO2 laser irradiation is exploited to realize nanocrystallization of Fe based amorphous alloys Fe73.5Cu1Nb3Si13.5B9 by overlapping of the heated areas, and to get homogeneous ultrafine grains of about 10nm with a bcc α-Fe(Si) structure, which is the foundation of the excellent soft magnetic property. X-ray diffraction and transmission electron microscopy(TEM) are used for microstructure analysis and observation, and the results show that irradiation power of 71w~99w gives the heat shock to the transformation from the metastable amorphous state to crystallized state, and proper time of about 20~30 seconds is necessary for optimum microstructure and soft magnetic properties.

Research on single pass laser crack-free cutting of thick and dense ceramics

Laser crack-free cutting of thick and dense ceramics (thickness > 10 mm, relative density ≥ 98%) by single pass which is based on continuous piercing through the work-piece was presented in this paper. With two processing stages matching with appropriate time shot for every piercing, low cycle duty, low gas pressure and other processing parameters, the crack-free internal straight or curve shape cutting of the ceramics could be obtained by CO2 laser at higher cutting speed of about 25 ∼ 30 mm/min. Combining with the analysis of the power flowing intensity and heat accumulation effects around laser spot, it is concluded that the non-equilibrium heat accumulation was inhibited effectively by the single pass laser crack-free cutting technique. For cutting of 10 mm thick Al2O3 ceramic, the total time without power flowing between the fore-piercing and the next-piercing by the technique could be ∼600 ms, which combined with ejecting of melting materials, could supply enough cooling time to inhibit the non-equilibrium heat accumulation resulting in cracks.Laser crack-free cutting of thick and dense ceramics (thickness > 10 mm, relative density ≥ 98%) by single pass which is based on continuous piercing through the work-piece was presented in this paper. With two processing stages matching with appropriate time shot for every piercing, low cycle duty, low gas pressure and other processing parameters, the crack-free internal straight or curve shape cutting of the ceramics could be obtained by CO2 laser at higher cutting speed of about 25 ∼ 30 mm/min. Combining with the analysis of the power flowing intensity and heat accumulation effects around laser spot, it is concluded that the non-equilibrium heat accumulation was inhibited effectively by the single pass laser crack-free cutting technique. For cutting of 10 mm thick Al2O3 ceramic, the total time without power flowing between the fore-piercing and the next-piercing by the technique could be ∼600 ms, which combined with ejecting of melting materials, could supply enough cooling time to inhibit the non-equi...

Characterization and Joining Behavior of Glass-to-KOVAR Alloy Fiber Laser Joint

This study investigates on the characterization and joining behavior between glass and KOVAR alloy with fiber laser. Due to the different chemic bonds and thermal expansion coefficients, the oxide layer plays an essential role in this process. First, surface treatments under different conditions have been discussed. It’s indicated that when the two textures (the square block and the strip phase) appeared on the KOVAR surface, the joinability of KOVAR alloy enhanced. Then, considering about three laser process parameters (beam scan speed, laser power and focus position) by the orthogonal experimentation, the result indicated that the possibility of this joining technology. Finally, the fractures graphs were observed by LEXT OSL 3000. By analyzing the FeO-SiO2-Fe phase diagram and XRD on the fractures, it displayed that a new chemical substances (Fe2SiO4) had formed which was considered as the key-materials for a good glass-to-KOVAR alloy joint.

Study on the characteristics of debris and hole diameter in laser drilling of thick alumina ceramics

Characterizations of debris and hole diameter in CO2 laser percussion drilling of alumina ceramic (4.4 mm thick) under various processing parameters were investigated. The main energetic parameters, including laser peak power, pulse frequency, pulse duty cycle, and piercing time, were selected as independent variables to be studied. The process qualities were evaluated in terms of the characteristics of debris, hole entrance and exit diameter. Based on the experimental results, it was found that laser peak power affected vaporization rate; pulse duty cycle influenced melt rate; pulse frequency affected valid heating efficiency in base material; and piercing time influenced drilled depth before beam break-through. On the process qualities (debris, entrance and exit diameter), laser peak power and duty cycle had significant effects, pulse frequency had a lower effect, while piercing time had the lowest effect. Comparatively, peak power had a higher effect than duty cycle on the formation of debris. Furthermore, higher pulse frequency could induce more symmetrical and smaller debris especially when the laser incidence angle was not zero and hence the melt ejected along a particular direction.Characterizations of debris and hole diameter in CO2 laser percussion drilling of alumina ceramic (4.4 mm thick) under various processing parameters were investigated. The main energetic parameters, including laser peak power, pulse frequency, pulse duty cycle, and piercing time, were selected as independent variables to be studied. The process qualities were evaluated in terms of the characteristics of debris, hole entrance and exit diameter. Based on the experimental results, it was found that laser peak power affected vaporization rate; pulse duty cycle influenced melt rate; pulse frequency affected valid heating efficiency in base material; and piercing time influenced drilled depth before beam break-through. On the process qualities (debris, entrance and exit diameter), laser peak power and duty cycle had significant effects, pulse frequency had a lower effect, while piercing time had the lowest effect. Comparatively, peak power had a higher effect than duty cycle on the formation of debris. Furtherm...

Study on the machining process of a new laser crack-free cutting technique for ceramics

This paper presents initial research results of a new laser crack-free cutting technique, which be capable of cutting ceramics with thickness of ≥10 mm in internal straight or curve trajectory by CO2 laser at higher cutting speed of about 25 ~ 30 mm/min. The technique is originated from the laser continuous piercing full through the workpieces but need appropriate time shot for every piercing and adaptation on processing steps, cycle duty and gas pressure and so on. With low frequency of 30 ~ 50 Hz, low duty cycle of 20 ~ 50%, piercing time of 0.1 ~ 0.5 s and piercing pitch of about 0.03 ~ 0.05 mm in pulse mode operation, crack-free laser cutting of ceramics can be achieved. By the study on Al2O3 and SiC ceramics with different thickness and density, it was concluded that the new laser crack-free cutting technique can be a feasible tool for successful cutting of ceramics in complex path, even for 3D cutting.