Enhanced Laser Shock by an Active Liquid Confinement—Hydrogen Peroxide

Abstract

This letter investigates a unique process to generate enhanced laser shock by applying an active liquid confinement-hydrogen peroxide (H2O2). The mechanism of fast chemical etching-assisted laser ablation is proposed. As a result, comparing with utilizing water as confinement, the efficiency of laser shock peening (LSP) of aluminum alloy 6061 with an active liquid confinement is improved by 150%, and the ablation rate of pulse laser ablation (PLA) of zinc is enhanced by 300%. This method breaks the major limitation of underwater pulsed laser processing caused by the breakdown plasma, with additional mechanisms to generate higher ablation rate and shock pressure under the same laser intensities.The laser shock induced by pulse laser ablation under a confinement has been widely investigated because of its great potential for industrial applications, such as LSP [1-6], laser dynamic forming [7,8], and laser-assisted micromachining [9,10]. The capability, efficiency, and application range of these laser-based techniques are strongly governed by the intensity of laser shock. Thus, enhancing the laser shock draws a great attention in this research field. The laser shock is ruled over by not only the laser power condition but also the confining media. Currently, the selection of confining media brings a major limitation to enhance the laser shock. For example, the solid confinements like glass are inconvenient for processing 3D surfaces, and they are also too brittle to stand the high power laser pulse. On the other hand, even if the liquid confinements like water are relatively more fiexible and practical, and have been widely used in industrial applications, they still suffer from the major drawback: When the laser intensity is above a threshold, the breakdown of liquid confinements screens the incident laser power and results in a saturation of laser shock and peak pressure [1,4,11,12]. Thus, it is worthwhile exploring other approaches to enhance the laser shock.In this letter, we study a unique process to enhance the laser shock by applying active liquid confinements like H2O2. The concept originates from that the laser shock is mostly dependent on the high density of laser-induced plasma, which is determined by the ablation rate of target materials through laser-material interactions [2,9,13,14]. Thus, we could effectively enhance the laser shock by using active liquid confinements because of the more effective ablation caused by the fast chemical etching reaction taking place simultaneously during laser ablation process. This idea is demonstrated by experimental results that the surface hardness and plastic deformation depth of aluminum alloy 6061 (AA6061) after LSP are effectively increased by using H2O2 as the confinement instead of H2O. LSP efficiency is improved by 150% with the application of H2O2. Our proposed mechanism suggests that the enhanced laser shock by H2O2 is majorly due to the higher ablation rate caused by the mutual promotion between the laser ablation and chemical etching. In addition, this mec...

Enhancement of pulsed laser ablation in environmentally friendly liquid

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“…When a laser beam at a high intensity is focused on the sample surface, the electrons are heated and excited to high-excited states due to inverse-bremsstrahlung process [20]. Followed by electron-neutral or electron-ion collisions and energy transfer, a dense cloud of ions and atoms in excited state, such as Cu 2+ , Cu + , O 2and Cu*, are ignited [21]. The plasma plume then develops to a mixture vapour containing these ions, atoms and electrons, as shown in Fig.…”

Magnetic Field Effects on Laser Drilling

“…The effects of magnetic field in pulsed laser deposition [10] and microelectrical discharge machining [11] have also been studied. Enhanced laser ablation rate by an active liquid confinement media has been reported by Liao et al [12]. Magnetic field has also been widely used in various manufacturing processes [11,13,14].…”

Laser shock peening: a promising tool for enhancing the aeroengine materials’ surface properties

“…The LSP process uses various confinement mediums and sacrificial or absorbent coating to enhance the shock wave properties. The confinement, such as solids (quartz and BK 7 glass) and liquids (such as water, motor oil, glycerol, and high-density organic liquids), have been reported in earlier literature [88,89]. Sacrificial layers such as aluminium foil, aluminium tape, black paint and black tape are widely used in the literature [19,20,23,36].…”