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采用脉冲宽度为100ns和2.1ps激光对厚度为0.8mm DD6镍基单晶合金进行了表面烧蚀、加工小孔等实验。观察不同脉冲能量下材料的烧蚀形貌和直径,得到了DD6镍基单晶合金等效脉冲数为670时纳秒和皮秒激光的烧蚀阈值。对纳秒和皮秒激光烧蚀凹槽剖面进行金相观察,以确定两种激光烧蚀材料的区别。在相同能量密度条件下,纳秒和皮秒激光制孔,观察孔表面和孔壁质量。实验结果表明,纳秒激光和皮秒激光对DD6镍基单晶合金的烧蚀阈值分别为1.63、0.11J/cm2;纳秒激光烧蚀凹槽内充满再铸层和微裂纹等热缺陷,而皮秒激光烧蚀凹槽内无再铸层且边缘材料的显微组织无任何变化;纳秒激光制孔表面存在飞溅物,孔口堆积冠状熔化物,孔壁存在微裂纹和20μm厚的连续再铸层,皮秒激光制孔,孔表面基本无飞溅物,孔壁上存在微裂纹和间断的再铸层,孔口较圆整。
The experiments of surface ablation, hole processing and so on were performed on DD6 nickel base single crystal alloy with a pulse width of 100ns and 2.1ps laser. The ablation morphology and diameter of the material under different pulse energies were observed. The ablation thresholds of nanosecond and picosecond lasers at the 670 equivalent pulse number of DD6 nickel base single crystal alloy were obtained. Metallographic observations of nanosecond and picosecond laser ablated groove sections were made to determine the difference between the two laser ablative materials. Under the same energy density conditions, nanosecond and picosecond laser holes were made to observe the pore surface and pore wall quality. The experimental results show that the ablation thresholds of the DD6 nickel-based single crystal alloys by the nanosecond laser and the picosecond laser are 1.63 and 0.11 J / cm2, respectively. The nanosecond laser ablation grooves are filled with thermal defects such as the recast layer and micro-cracks, However, there was no recast layer in the picosecond laser ablation groove and the microstructure of the edge material did not change. There was a spatter on the surface of the nanosecond laser hole, a crown melt was formed in the orifice, microcracks existed in the pore wall and 20 μm thick Continuous casting layer, picosecond laser hole, basically no splatter hole surface, there are micro-cracks in the hole wall and the intermittent recast layer, the orifice is more rounded.