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采用毫秒激光和皮秒激光在带热障涂层的镍基单晶合金上加工了气膜孔,对比研究了长脉冲与超短脉冲加工对热障涂层及金属基体孔壁形貌的影响。实验发现,波长1064 nm的毫秒激光在试样表面产生的能量密度直接影响到陶瓷层的加工。以2866 J/cm2的能量密度从陶瓷面加工,陶瓷面的熔化所需要的热积累时间长,热量会传导至高温金属,产生类似熔池的热影响;而从金属面加工则由于陶瓷是最后加工的材料,有足够的热积累时间熔化陶瓷涂层,从而直接打通小孔。当毫秒激光的能量密度提高至6369 J/cm2时,热量在涂层中的积累速度加快,陶瓷材料能够快速熔化,从而避免了金属基体先于陶瓷熔化的现象,同时,加工过程中熔化后的陶瓷会经过孔通道,从而出现附着在孔壁上的现象。采用皮秒激光加工陶瓷涂层仅需要能量密度达到32 J/cm2,皮秒激光旋切制孔是将小孔圆周上的材料全部剥蚀掉,直至孔打通,而孔内的材料会从孔中掉出。皮秒激光加工中产生的等离子体冲击力会引起涂层的开裂,由于热障涂层制备方法不同引起涂层中的裂纹方向有所不同,等离子喷涂制备的涂层为层状结构,裂纹易沿平行于表面方向生长,而EB-PVD制备的涂层为柱状晶结构,裂纹多出现在柱状晶的间隙。
The effects of long pulse and ultrashort pulse processing on the thermal barrier coating and the pore morphology of the metal matrix were studied by using millisecond laser and picosecond laser to process the gas film pores on the thermal barrier coated nickel-based single crystal alloy . The experimental results show that the energy density of millisecond laser with the wavelength of 1064 nm on the sample surface directly affects the processing of the ceramic layer. With 2866 J / cm2 energy density from the ceramic surface processing, ceramic surface melting heat required for long accumulation of heat will be transmitted to the high temperature metal, resulting in a similar pool of heat; and from the metal surface processing is due to the ceramic is the last Processed material, there is enough heat to accumulate time to melt the ceramic coating, which directly open the hole. When the energy density of the millisecond laser is increased to 6369 J / cm2, the heat builds up in the coating faster and the ceramic material melts quickly, avoiding the metal matrix melting prior to the ceramic, while the melted The ceramic passes through the pore channels, causing the phenomenon of adhesion to the walls of the pores. Picosecond laser processing of ceramic coatings requires only an energy density of 32 J / cm2. Picosecond laser trimming of holes is to erode all the material on the circumference of the hole until the hole is open, and the material in the hole is removed from the hole drop. The plasma impact force generated by the picosecond laser processing can cause cracking of the coating. Because the preparation method of the thermal barrier coating causes the crack direction in the coating to be different, the coating prepared by the plasma spraying is a layered structure and the crack is easy to crack The growth was parallel to the surface, while the EB-PVD coating was a columnar crystal structure with cracks mostly appearing in the columnar grains.