一种提高表面完整性的气膜孔成形方法

为了解决目前航空发动机涡轮叶片气膜孔成形工艺存在热影响严重等问题,提出了采用超快激光环切与螺旋扫描的加工方法,设计了一种可实现高效、无热效应气膜孔加工的双激光光源微加工系统,并从作用机理和实际加工过程两方面分析了热效应的产生原因,指出了其中的主要影响因素,然后针对这些因素选用DD6材料进行了工艺参数优化和实验验证.实验结果表明:采用500fs激光与微秒长脉冲激光复合加工的方式可以使精细钻孔的效率提升约10倍,并得到基本无重铸层和微裂纹的涡轮叶片气膜孔;其工艺参数包括扫描速度为2400r/min,重叠率为12%,进给量为5μm,重复频率为20kHz以及0.6Pa同轴吹气.表明超快激光配合合理的工艺参数和加工方式可以实现无热效应气膜孔加工,是一种有效提高气膜孔成形表面完整性的工艺方法. 

A forming method for improving surface integrity of film cooling holes

In order to solve the problems of forming process of turbine blade of aero-engine film cooling holes, such as severe heat effect, a helix drilling and spiral drilling processing method for microholes by ultrafast laser was proposed, and a double power laser system was designed for machining of film cooling holes efficiently and without heat effect; the reason of heat effects was analyzed from two aspects of action mechanism and actual machining process; the main influential factors were pointed out and the optimization of process parameters and experimental verification targeting at these factors were processed using DD6 material. The experimental results show that the composite processing method using 500fs laser and microseconds laser can increase fine drilling efficiency about 10 times, and can also process the film cooling holes on turbine blades without recast layer and micro-cracks; the process parameters include beam scanning speed of 2400r/min, overlap rate of 12%, feeding amount of 5μm, repetition frequency of 20kHz and coaxial blow with the air pressure of 0.6Pa. They also show that ultrafast laser with reasonable process parameters and processing methods can process film cooling holes without heat effects, so it is an effective technological method to improve the surface integrity of film cooling holes.