ADI Sprocke Tensile strength of 1400 MPa, elongation of 2%

The austempered ductile iron (ADI) is a type of ductile iron that has been heat-treated to improve its mechanical properties. The process involves two main steps: austenitizing and tempering.

1.Austenitizing: In this step, the ductile iron is heated to a high temperature to transform the ferrite and pearlite in the matrix into austenite. This is typically done at temperatures around 900°C to 950°C (1652°F to 1742°F). During this phase, carbon from the graphite nodules diffuses into the austenite, increasing its carbon content.

2.Tempering: After austenitizing, the material is rapidly cooled to a lower temperature, typically between 230°C to 400°C (446°F to 752°F), where it is held for several hours. This allows for the formation of bainite, which is a mixture of ferrite and high-carbon austenite. The high-carbon austenite is unstable and eventually transforms into a fine mixture of ferrite and carbides.

The unique mechanical properties of ADI are due to its microstructure, which consists of:

1.Graphite nodules: These provide internal lubrication, making ADI self-lubricating and reducing wear.

2.Bainite: This provides high strength and toughness.

3.Retained austenite: This contributes to the ductility and energy absorption capacity of the material.

The combination of these properties makes ADI an attractive material for power train components such as gears and gearbox parts, where high strength, ductility, toughness, wear resistance, and machinability are desired.