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Turbine Housing Material: Introducing 6 Variety Housing Alloy

The turbine housing material should resist high- temperature: the working temperature of the diesel engine supercharger is generally around 600℃, the operating temperature of the gasoline engine turbocharger is as high as 800-900℃, and the working temperature of the particular vehicle engine supercharger is as high as 900-950℃. °C. With the improvement of engine performance requirements, the operating temperature of the turbocharger has to be further increased.

Turbocharger Schematic

The turbocharger is mainly composed of a turbine part and a wheel part. The turbine wheels at high temperature and requires outstanding high-temperature performance, so it is made of high-temperature alloy. The shape of the turbocharger turbine is complex, and the material is needed to have good casting and high-temperature performance.

The turbocharger turbine housing material must have the following properties:

1. Good high-temperature oxidation resistance: the supercharger works in a high-temperature environment for a long time, and the oxidation resistance of the material at high temperature directly affects the service life of the supercharger. To provide the high-temperature oxidation resistance of the material, alloying elements are generally added to the material, such as Ni, Cr, and Mo.

2. Stable microstructure: The material does not undergo phase transition as much as possible in the range from room temperature to working temperature or minimizes phase transition. Because the phase change will cause the volume of the product to change, causing it to generate internal stress or deformation, affecting the performance and life of the product. Therefore, the collective material is preferably a stable ferrite or austenite structure.

3. Small thermal expansion coefficient: Small thermal expansion coefficient is beneficial for reducing the supercharger product’s thermal stress and thermal deformation and improves the product’s performance and service life.

4. High-temperature strength: turbine housing material must meet the necessary strength requirements of the product at high temperatures.

5. Good process performance: Many heat-resistant and high-temperature resistant materials exist. However, due to the complex shape, highly high dimensional accuracy and surface quality requirements of the turbocharger volute, the materials used to manufacture the turbocharger casing must have good manufacturability.

With the continuous strengthening of the engine, the waste discharge temperature gradually increases, and the high-temperature resistance performance requirements of the turbocharger housing material are also getting higher and higher. Currently, the turbocharger Turbine housing material is mainly cast iron and steel, primarily the following six materials, period types and characteristics as shown in the following.

Turbocharger Turbine Housing
Turbocharger Turbine Housing

Six turbine housing material

Gray Iron
Alloying elements such as Cr, Ni, and Si can improve high-temperature fatigue performance and performance
Oxidation resistance at operating temperatures below 500 °C.

Ductile Iron
Ferritic ductile iron, which controls the pearlite content, can reduce the turbocharger housing
The resulting internal stresses extend the service life. Ductile iron is used at operating temperatures.
Operating environment below 650 °C.

Metallographic Structure Of Ductile Iron
Metallographic Structure Of Ductile Iron

Chlorine-resistant Silicon Iron
Contains alloying elements such as Si and Mo, which are conducive to increasing the high temperature and antioxidant resistance of cast iron
Chemical properties, the maximum operating temperature at 760 °C.

High Nickel Ductile Iron
Contains Ni, Cr and other alloying elements with high strength, hardness and oxidation resistance,
The maximum operating temperature is 880 °C.

Austenitic Stainless Steel
With a high content of valuable elements such as Ni, W, etc., the maximum operating temperature is at 1150 °C.

Ferritic stainless steel
Cr content of 8% to 30%, with a small amount of Ni or no Ni, the tissue is iron
Primitive, maximum operating temperature at 950°C.

Gray iron
Gray iron - Turbine housing material

In general, the higher the degree of alloy in the cast iron materials, the worse the casting performance, the lower the processing yield, and the higher the manufacturing cost. The lower the carbon content in stainless steel, the lower the casting performance.

Among the automotive turbocharger metal materials currently on the market, the highest temperature that can adapt to the working process is nickel-containing austenitic stainless steel, which is widely used in the market. Because it contains precious metals, manufacturing costs are higher. The choice of turbocharger turbine housing material requires a combination of factors.

With the development of turbocharging technology, its emission temperature has risen from about 500°C to more than 900°C. The wide application of gasoline turbocharging and direct injection technology in cylinders, with emission temperatures of up to 1050 °C, puts higher requirements for turbocharger turbine housing materials: First, it has good high-temperature oxidation resistance, a slight change in thermal expansion, and high strength. Second, the material has good forging and processing properties.