不同脉冲激光在带热障涂层高温合金上制孔及热循环后孔组织形貌的变化

Processing Holes on Superalloy with Thermal Barrier Coatings by Different Pulsed Lasers and Changes of Hole Morphology After Thermal Cycling

采用毫秒激光和超快激光在带热障涂层高温合金上加工气膜孔,然后对制孔试样进行热循环试验,对比研究了两种脉冲激光对热障涂层及金属基体孔壁形貌的影响,分析了小孔热循环后组织形貌的变化。初步试验结果表明:采用毫秒激光在带热障涂层的高温合金试样上制孔,孔边缘陶瓷涂层易出现掉块现象,且黏结层和金属基体会产生再铸层;而皮秒激光制孔边缘组织与远离孔边缘组织无明显变化,陶瓷涂层、黏结层以及金属基体均无再铸层和微裂纹形成。制孔试样经450次热循环后,孔周围陶瓷涂层组织均未见明显变化,孔边缘黏结层与远离孔边缘处的组织发生明显改变。毫秒激光制孔孔边缘金属基体再铸层组织区域厚度增加,而皮秒激光制孔孔边缘金属基体层也出现了与远离孔边缘组织不同的扩散区域。毫秒激光制孔试样热循环后,孔边缘黏结层与陶瓷涂层之间的TGO层出现微裂纹;而皮秒激光制孔边缘热循环后,黏结层与陶瓷涂层之间未出现微裂纹。

The millisecond laser and ultrafast laser were used to process gas film holes on the superalloy with thermal barrier coatings(TBC).The thermal cycle test was carried out on the hole-making sample.The effects of two pulsed lasers on the morphology of the thermal barrier coating and the hole wall of the metal matrix were compared and studied.The changes of the micro-hole morphology before and after thermal cycling were analyzed.The results showed that:When millisecond laser was used to make holes on the superalloy sample with thermal barrier coating,the ceramic coating at the edge of the holes would lose lumps,the bonding layer and metal matrix would produce recast layer.When using picosecond laser to make holes,there was no obvious change of the structure either near or away from the hole edge,and there was no recast layer or microcrack formation in the ceramic coating,bonding layer and metal matrix.After the hole-making sample was thermally cycled 450 times,there was no obvious change in the structure of the ceramic coating around the hole.The bonding layer at the edge of the hole and the organization far away from the edge of the hole changed significantly.The thickness of the recast layer of metal matrix at the edge of the hole produced by millisecond laser increased,and the metal matrix layer at the edge of the hole produced by picosecond laser also had a diffusion area which was different from the structure away from the edge of the hole.After millisecond laser hole-making sample was thermal cycled,the TGO layer between the hole edge bonding layer and the ceramic coating appeared micro-cracks.However,there was no micro-crack between the bonding layer and the ceramic coating at the edge of the hole produced by picosecond laser after thermal cycling.