The turbine disc is machined either as an integral part of the shaft or is shrunk on to the shaft. The rotor blades may be cast, forged or machined from a high temperature creep-resistant steel such as Nimonic 8OA or 90. Welded joints or ‘fir-tree’ roots are used to fix them to the disc, the latter design being more common on high pressure units since they provide a degree of vibration damping and allow a wider selection of blade and disc materials to be considered. Additional vibration damping can be provided by wire lacing the blades. The turbocharger manufacturer will offer a range of ‘trims’ or flow capacities with each basic design of turbocharger by varying blade (stator and rotor) height and stator blade angle.

A disadvantage of the axial flow turbine is that it complicates the design of the gas inlet and outlet. The gas inflow section is particularly important hence this is usually located on the end, allowing generous curvature in the inlet ducts to the stator blades for minimum flow distortion and loss. The turbine exit duct acts merely as a collector, hence a compact design can be used, minimizing turbocharger length. However, a recent trend is to utilize some exhaust diffusion to increase turbine expansion ratio and power output.