氮化硅陶瓷水射流辅助激光精密加工

Water-jet assisted laser precision processing of Si_3N_4 ceramics

为解决工程陶瓷在激光加工中的表面质量问题提出了溶液辅助激光加工方法,首先在综合国内外有关研究的基础上,分析了激光穿越水层的能量传输、激光作用水下固体物质的热传导和静水及水射流辅助激光加工的作用机理;搭建了旁轴射流与超声振动辅助激光复合加工系统,开展了不同加工条件下氮化硅陶瓷刻槽对比试验。借助扫描电子显微镜检测分析激光刻蚀槽体形貌,运用激光共聚焦显微镜观测了槽体截面轮廓。研究表明,水射流辅助激光加工氮化硅陶瓷,因激光穿越水层、水的对流冷却等作用减少了激光烧蚀材料的有效能量,刻蚀深度有所降低;同时由于水层的存在改变了加工区域能量分布,使得槽口变宽。当激光电流200A、频率50Hz、脉宽0.6ms时刻槽深度相对减小30%,宽度增大21%。水与氮化硅在激光作用下的会发生水解等效应,且水蒸汽、材料蒸汽、熔融粒子、气泡等沿水流动方向被带走,有利于表面质量的提高,综合效果良好。

Solution-assisted laser processing was proposed to solve the problem of surface quality in engineering ceramics during laser processing.First,the energy transfer of the laser through a water layer,heat transfer of the laser acting on an underwater solid matter,and action mechanism of the auxiliary laser processing of the hydrostatic water and water jet were analyzed after referring to relevant research at home and abroad.A complex beam-processing system of the parabola jet and ultrasonic-vibration-assisted laser was constructed,and silicon nitride ceramics were tested under different processing conditions.Scanning electron microscopy was used to detect the morphology of the grooves,and the contour of the cut section was observed using a laser-scanning confocal microscope.Our research shows that the absorption and convection of water reduce the effective energy of the laser ablation materials and the etching rate during the water-jet-assisted laser processing of silicon nitride ceramic materials.Simultaneously,owing to the existence of a water layer,the energy distribution in the processing area changes,which results in widening of the notch.The groove depth decreases by30%and the width increases by21%when the laser current is200A,frequency is50Hz,and pulse width is0.6ms.Because the water and silicon nitride are hydrolyzed by the laser action,water vapor,material steam,molten particles,bubbles,and others are washed away in the water-flow direction,which is beneficial for the improvement in the processing efficiency and surface quality.