Milling of Fir-Tree Slots in Allvac 718 plus

Abstract

For the machining of profiled grooves in turbine discs made out of nickel based alloys, broaching is still state of the art. However, the broaching process entails some disadvantages like high costs and long delivery times for the machine tools and the broaches in combination with inflexibility with regard to the groove geometry and machining task. An alternative to the broaching process is the integration of the profile slotting on a 5-axis milling center. This paper deals with an approach for machining a fir-tree slot via different milling process chains. The two roughing strategies, ceramic side milling and carbide end milling, are depicted with regard to tool wear and the economy. The finished fir-tree slot will be evaluated in terms of dimensional stability. In addition, the possibility of finish broaching on a five-axis machine tool is shown.