Technological and economical assessment of alternative process chains for turbocharger impeller manufacture

Abstract

Turbochargers boost the performance of combustion engines enormously: the motors are significantly smaller at the same power, consume less fuel and their exhaust emissions are lower. A further increase in performance requires turbine wheels that can withstand even higher specific loads. Gamma titanium aluminide is the ideal material for this. However, to date there is no process chain which permits an economical manufacturing of the component. Responsible for this are the difficult-to-access, filigree flow geometries and the material properties. Thus, there is a high need for a comprehensive evaluation of alternatives for impeller manufacture. In this paper, different manufacturing chains consisting of pre-finishing and finishing of near-net-shape parts are compared to each other for a given example geometry. Electrochemical as well as Electrical Discharge Machining technologies are taken into account as alternatives for conventional milling and grinding processes for the finishing of cast blanks or samples produced by additive manufacturing. Based on a technological analysis a cost comparison is executed, which allows an economical assessment of the different process chains regarding given boundary conditions and varying production quantities.