Key Techniques For EDM Of Shrouded Blisk’s Surface Quality

Turbine blisk is regarded as the core component of aero engine androcket engine. The improvement of the aircraft’s performance and flightability relies heavily on the development of the blisk parts. Aircraft androcket engines consist of a series of parts with complex surface. In addition,most of them are made of difficult cutting material, such as Ti alloy,Ni-based alloy. Traditional machine approaches usually cannot obtainsatisfying processing effects. The development tendency of the blisk is theusing of the shrouded and integrated technology. Multi-axis NC EDM is apreferable technology to machine shrouded blisks. Statistical data revealedthat most of the aero engine and rocket engine part failures ware resultedfrom its surface defect, which gradually extends to the inner zone. Poorsurface quality of the aero engine and rocket engine parts will acceleratetheir fatigue failure, and will inevitably reduce the engine’s service life andreliability. It is of importance to study the EDM technologies to improvethe surface quality of shrouded blisks.Based on the introduction of the EDM technology of shrolded bliskesand the surface quality machined by EDM, an empirical formula ofInconel718surface roughness machined by EDM was established throughseries of experiments. Orbiting EDM technology, as well as the optimalcombination of EDM machining parameters and processes, was studied.The content of the thesis is listed as follows.By using Minitab experimental design analysis software, the effectof EDM machining parameters on the surface quality of Inconel718wasinvestigated. It was found that Ipand Tonare the most important parameters to material removal rate, and they are also inverse proportion to the surfaceroughness. The proper combination of Ipand Toncan get the desiredmaterial removal rate and surface roughness.Under the assistant of the CAD/CAM software for EDM of integralshrouded blisk, the3D freeform electrode was designed and the feedingpath of the electrode was determined. An integral shrouded superalloyblisk was successfully machined by using the optimal machiningparameters mentioned above.Orbiting EDM was explored to improve the surface quality of integralshrouded blisk. Efficiency comparison, roughness analysis, scanningelectron microscopy and EDS analysis, as well as metallographic analysis,were conducted under different machining processes and parameters. Theexperimental results showed that orbiting EDM can improve materialremoved rate, and at the same time, can decrease the surface roughness andthe thickness of the recast layer.After a series of EDM experiments, a practical EDM machiningprocess for integral shrouded turbine blisk was achieved.