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Microchannel fabrication and metallurgical characterization on titanium by nanosecond fiber laser micromilling
摘要： Laser micromilling technique is used to manufacture microchannel on metals and nonmetals. Microfeatures ≤100 μm are still challenging for fabrication by common methods. Nanosecond fiber laser micromachining has become more popular owing to its prospective implementation in laser micromilling. Microchannel application relies on its geometric dimension, profile, and surface quality. In this study, an attempt was made to explore the impact of process parameters scanning times, scanning velocity, pulse repetition rate, and assist gas pressure on top kerf width, taper, surface roughness, and metal removal rate in laser micromilling experimentally. Microchannel width varied between 45.5 and 70.9 μm. A regression model has been developed for each response. ANOVA (analysis of variance) has been carried out to remove insignificant parameters. Thermal stress analyzed by surface cracks inside microchannel by Scanning Electrone Microscopy (SEM) images. Higher PRR, lower no. of scans, higher scanning speed and high air pressure found suitable for lesser surface cracks. Redeposition observed at slower scanning velocity and minimum scanning times. Oxidation zone from boundary of channel varies between 37 and 58 μm. Oxide formed on Ti surface which increases oxygen content toward center of channel from 51.08 to 76.22% compared to outside surroundings.
关键词： oxidized zone,MRR,kerf width,LMM,surface cracks,taper,surface roughness,recast layer
更新于2025-09-19 17:13:59
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[Laser Institute of America ICALEO? 2016: 35th International Congress on Applications of Lasers & Electro-Optics - San Diego, California, USA (October 16–20, 2016)] International Congress on Applications of Lasers & Electro-Optics - Fibre laser trepanning drilling of metals and alloys
摘要： Laser drilling of metals and alloys is extensively used in modern manufacturing industries to produce holes of various sizes and shapes. Currently, most aerospace laser drilling is performed using Nd:YAG laser and over the years many attempts have been made to increase the productivity of Nd:YAG lasers drilling process, but with little success. This paper investigates the use of recently developed millisecond-pulsed-Quasi-CW-fibre-laser for trepanning drilling of aerospace grade nickel super-alloy. The main investigation concentrates on understanding the effects of Quasi-CW-fibre-laser parameters on trepanning laser drilled hole quality. The principal findings are based on reducing the recast and oxide layer. Results show that the high average power of the Quasi-CW-fibre-lasers can be effectively used to achieve increased trepanning drilling speed without undermining the drilling quality, which is not feasible with a free-space Nd:YAG laser. Low peak power and high average power can be effectively used to produce better laser drilled hole than the high peak power and low frequency, which is observed with the traditional millisecond Nd:YAG drilling process.
关键词： alloys,Fibre laser,nickel super-alloy,trepanning drilling,oxide layer,aerospace,recast layer,metals
更新于2025-09-16 10:30:52
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Modelling the influence of laser drilled recast layer thickness on the fatigue performance of CMSX-4
摘要： This paper introduces a novel approach to fatigue life prediction modelling considering the laser drilling effect on film cooling holes of turbine vanes. The methodology proposed is based on a stress-life model such as the Basquin law and the introduction of manufacturing damage effect. The proposed empirical model gives a unique versatility compared to other stress-life models by considering surface damage such as the recast layer produced by the laser drilling process. The proposed empirical model has been thoroughly tested and validated using existing fatigue data. The statistical analysis shows that the proposed model is adequate for estimating the fatigue life of laser drilled specimens considering the recast layer thicknesses effect. The proposed model also can estimate the life of untested specimens even when only a small sample of fatigue data is available, thereby reducing the required testing data.
关键词： Fatigue life,recast layer,laser drilling,surface defects
更新于2025-09-12 10:27:22
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Adaptive neuro-fuzzy inference system based modeling of recast layer thickness during laser trepanning of Inconel-718 sheet
摘要： Re-solidification of molten material during the laser trepanning of Inconel-718 is a major hindrance in achieving good quality drill with high precision and accuracy. Re-solidification affects the performance of the drilled hole. Many researchers have tried for the optimization of laser trepan drilling in order to improve the drilled hole quality characteristics. But till now, limited work has been reported in concern with recast layer formation in laser trepan drilling of Inconel-718. This paper experimentally investigated the recast layer formation during laser trepan drilling followed by the prediction of the recast layer formation using the adaptive neuro-fuzzy inference system (ANFIS). Experiments are performed on 1.4-mm-thick Inconel-718 sheet using pulsed Nd: YAG laser. Recast layer thickness has been measured for each experiment followed by the ANFIS-based prediction of recast layer. Moreover, the effect of different input parameters on the recast layer has also been discussed.
关键词： Recast layer,Laser trepan drilling,Adaptive neuro-fuzzy inference system,Inconel-718
更新于2025-09-11 14:15:04
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An investigation of recast behavior in laser ablation of 4H-silicon carbide wafer
摘要： 4H-silicon carbide (SiC) is a suitable semiconductor material for high-speed power devices but also a typical difficult-to-process and hard-brittle material. Laser ablation is an efficient approach to process SiC. However, recast layer is an inevitable thermal damage during laser ablation. The present study experimentally and numerically investigated the recast behavior in laser ablation of 4H–SiC. The recast humps are with height of 1.4–3.3 μm and width of 12–22 μm, consist of SiC, Si, and SiO2, where 15.08 wt% of oxygen is detected. Microcracks and pore clusters are observed on the recast humps under SEM. Recoil pressure and surface tension in the molten pool dominate the process of recast hump formation. The recoil pressure of Si vapor is 2.27 MPa at 5000 K, as high as 22 times of atmospheric pressure. The simulation results show that the fluid in the middle flows around while the surrounding fluid flows upwards. The upward flow is almost laminar while the flow at the bottom of the molten pool is turbulent entertaining air and forming bubbles. The vaporization-induced keyhole in the molten pool becomes deeper and the sidewall becomes more inclined over time, accompanying with the “growing” of the recast hump. There are mainly three reasons causing the increase of recast height and recast width with the increased average laser power: (a) increase of recoil pressure; (b) increase of temperature gradient in the molten pool, enhancing the Marangoni convection; and (c) enlarging the molten pool and leading to more materials melting. With the decrease of the laser scanning speed, more liquid molten material is evaporated in the molten pool instead of being ejected outward to form recast humps. The increase of the laser pulse frequency decreases the peak laser intensity and hence results in the decrease of the recoil pressure. Besides, it also leads to the weakening of the heating ability of laser and lessening of the liquid molten material that could be ejected.
关键词： Marangoni convection,Recoil pressure,4H-silicon carbide,Recast layer,Laser ablation
更新于2025-09-11 14:15:04