激光类型对SiC/SiC复合材料孔加工的影响

Effect of laser type on hole machining of SiC/SiC composites

SiC/SiC复合材料具有硬度高、脆性大等特点,属于典型的难加工材料,制备冷却孔主要采用激光加工的方法。毫秒激光与纳秒激光主要是利用光热作用迅速加热目标材料,使之熔融、气化,并借助高速气流来移除材料,由于纳秒激光的脉冲持续时间短、能量密度高,因此更容易实现材料的气化,并且引起的热效应较少。本工作分别采用毫秒激光与纳秒激光对SiC/SiC复合材料进行制孔,结果表明,对于直径0.6 mm、倾斜角度为25°的冷却孔,纳秒激光加工时长是毫秒激光的8.7倍;两种激光加工的孔均存在一定的锥度,其中纳秒激光加工的孔锥角为2.12°,毫秒激光加工的孔锥角为1.49°。毫秒激光加工的孔内部、孔出口端与入口端均存在残留物,并且孔周边存在明显的重熔-氧化区与热影响区;而纳秒激光加工的孔内部无明显残留物,激光入口端出现变色现象,出口端无变色现象,无明显重熔-氧化区与热影响区。元素分析结果表明,两种激光加工过程中均能够引起材料的氧化。

SiC/SiC composites have the characteristics of high hardness and brittleness,and they are typical difficult materials to process.Laser processing is mainly used to prepare cooling holes.Millisecond and nanosecond lasers mainly use photothermal action to rapidly heat the target material,melt and gasify it,and remove the material with the help of high-speed gas flow.Due to the short pulse duration and high peak power of nanosecond laser,it is easier to realize the gasification of materials,and the thermal effect caused is less.In this paper,millisecond and nanosecond lasers are used to make holes in SiC/SiC composites respectively.The results show that for cooling holes with a diameter of 0.6 mm and an inclination angle of 25 °,the processing time of nanosecond laser is 8.7 times longer than that of millisecond laser.The two kinds of laser processed holes have certain taper,in which the hole cone angle of nanosecond laser processing is 2.12 ° and that of millisecond laser processing is 1.49 °.There are residues in the inner,outlet end and inlet end of the hole processed by millisecond laser,and there are obvious remelting oxidation zone and heat affected zone around the hole.However,there is no obvious residue inside the hole processed by nanosecond laser,there is discoloration at the inlet end of the laser,there is no discoloration at the outlet end,and there is no obvious remelting oxidation zone and heat affected zone.The results of elemental analysis show that both kinds of laser processing can cause the oxidation of materials.