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1.Compressor cover 2.compressor impeller
3.Thrust Bearing 4.back plate
5.turbine housing 6.rotor and shaft
7.float bearing 8.center housing

Turbine Housing

typically Spheroidal Graphite cast iron (ferritic)

typically green sand mould, sand core profile machining to match the turbine blade shape

normally the primary mounting point and load bearing interface for the whole turbo

may include water cooling jackets in some applications

operation can be up to 760 °C on some applications

requirements

impact resistance (ductility)

oxidation resistance

high temp strength

thermal fatigue resistance

ease of machining

other materials used on turbochargers :-NiResist

Bearing Housing

typically Grey (flake) cast iron (pearlitic)

typically shell moulded cores to provide positional accuracy of bearing location and seals, shell mould or sand cast outer

machined by a combination of milling, turning, drilling, tapping, honing

complex geometries - particularly for water cooled housings and variable geometry turbos

requirements

castability

ease of machining

rigidity

thermal stability

Compressor Housing

typically cast aluminum alloy - various grades

gravity die cast or sand cast

profile machining to match impeller blade shape

operation can be up to 200 °C

requirements

impact resistance (ductility)

ease of machining

Impeller

typically cast aluminum alloy cast by a variant of investment casting process, using rubber formers and plaster moulds

started using this process in 1976 to allow the production of wheels with backsweep on the blades

operation up to more than 200 °C possible

requirements

fatigue strength

elevated temp strength

creep resistance

corrosion resistance

for special high pressure applications temperatures can exceed the creep limits of aluminum. In these applications cast titanium impellers may be used.

very sensitive to balance groove shape and to damage/defects

Shaft and Wheel

high nickel superalloy

investment cast

blade profile machined

operation up to 760 °C on some applications

friction welded to forged steel shaft

very sensitive to balance grooves, and defects or damage

requirements

fatigue strength

elevated temp strength

creep resistance

corrosion resistance

Bearing System

Journal Bearings

fully floating ring bearings - allow higher clearances, so higher oil flows for cooling

oil film thicknesses of 0.008 to 0.015 mm

brass or leaded bronze

Thrust Bearing

taper land bearing

bronze

thrust loads of 100 - 2000 N (22.5 lb.ft to 450 lb.ft) -size dependent

typical oil film thickness 0.008 - 0.015mm

Must withstand high temperatures, hot shut down, soot loading in the oil, contaminants, oil additives, dry starts