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Effects of Various Scan Strategies on Laser Micromilling of SiAlON Ceramic
A.K. Sahu, J. Malhotra and S. Jha

Micromachining of ceramics is a challenging task for industries due to high hardness property but has many applications in the modern engineering world. Laser micromilling is a popular technique to enhance machining efficiency and surface quality attributes of ceramics. In current work, laser micromilling is investigated in different gas medium(s) (dry air, Ar, N2) with a nanosecond laser to improve the machining characteristics of SiAlON ceramic. Laser micromilling is investigated along five factors: axial feed; scanning velocity; pulse repetition rate (PRR); assist gas medium; and laser path scanning strategy with ablation depth; and material removal rate (MRR) as responses. A Taguchi L27 orthogonal experiment design was used for experimentation. The factor contribution based on analysis of variance (ANOVA) shows assist gas to be most significant for ablation depth with contribution of 34.57%; whereas, for MRR, it is 9.91%. The scanning strategy contributed most for MRR with 60.53%. The optimum conditions for maximum ablation depth are axial feed of 10 μm, PRR of 50 kHz and scanning velocity of 15 mm/s; and for MRR are axial feed of 20 μm, PRR of 50 kHz and scanning velocity of 40 mm/s. Dry air and triangular scan strategy are found to be optimum for both responses. Lastly, a surface morphology study shows redeposition and recasts with minor cracks on surface due to thermal stress in Ar and N2 medium.

Keywords: Fibre laser, nanosecond laser, SiAlON ceramic, laser micromilling, ablation depth, material removal rate (MRR), scan strategy, gas-assisted machining

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