What are turbine housings made of?

Turbochargers have two major sections one usually referred to as the hot side and the other as the cold side. Two main parts from the hot side are turbine housing and turbine wheel. In order to stand extreme heat, both of these parts have to be able to withstand high temperature. In this discussion we’ll be focusing on the turbine housing. Arashi turbine housings are made mainly with 5 types of ductile cast irons, they are SCH22, Stainless Steel, D5S, D2, and FCD(HiSiMo).

SCH22 is basically the hardest cast iron steel among these 5, its hardness is 442 HBW and it resists temperature of up to 1300°C. This heat-resistant cast steel alloy is stable at high temperature; therefore, we use it on our Kuro and Lab Z series. However, due to its hardness, machining the material is more costly than the other materials mentioned above since the rate of breaking cutting tools is higher.

Another heat-resistant cast steel alloy we use to produce turbine housings is Stainless Steel, this is probably the only more commonly known material among these 5. The Stainless Steel we use is capable of working under environment of up to 1050°C. Arashi applies this material to Kuro and Lab Z series turbine housing.

Nickel is one of the important elements to making turbine housings, D5S contains 36% Ni which increases its durability and its heat resistant temperature. It resists heat ranging 800 - 1000°C. The material is widely used in turbine housing of Lab Z series.

D2 is used in EVO series turbine housings such as EVO 9 and EVO 10. This high-carbon, high-chromium tool steel is high wear and abrasion resistant. High chromium also causes it to be corrosion resistant.

Finally, we have FCD (HiSiMo), we use this material on Subaru series turbine housings. Compared to other above materials it is not as hard, making it the easiest and the most cost-efficient when machining. FCD is used typically on applications under 800°C.

Before manufacturing each turbo, Arashi team carefully select appropriate material for each application. High end material isn’t suitable for every engine setup as its cost is higher, making the complete turbo more expensive. Arashi strives to provide cost-efficient products for our customers.