Air film cooling technology is representative of important structure improvements of turbine blades. Its main structure characteristics is the design of a large amount of air-film holes in the turbine blade’s front edge and blade surface etc. The hole diameter is normally 0.2~0.8mm and the spacial angles are complicated. Therefore ,the machining technology if air film holes has become one of key technologies for turbine blade manufacture.
At present, the machining of air film cooling holes in the blade mainly uses the method of laser drilling, EDM drilling or electro-stream drilling. Each method has its own characteristics. The laser drilling is highly efficient but produces thick remelt layer; the EDM drilling generates relatively thinner remelt layer;the electro-stream drilling has no remelt layer and produces good quality but with low efficiency.
We have made the feasibility test of key processes and designed the key mechanism modules through the design and demonstration of the overall scheme of the EDM process and equipment for machining of air film cooling holes in the turbine blade and developed the EDM machining tools for the machining of straight round air film cooling holes. The main characteristics include: