Martensite

Martensite is a metallurgical phase in steels characterised by a tetragonal lattice structure. This phase typically forms when steel is rapidly cooled (quenched) from the austenite phase.

Properties of martensite

• High hardness: Martensite is known for its exceptional hardness, making it an important phase for wear-resistant applications.
• Low ductility: Unlike austenite, martensite is less malleable and tends to be brittle.
• Magnetic properties: Martensitic steel is usually ferromagnetic.

Difference from other phases

Martensite differs from austenite (face-centred cubic) and ferrite (body-centred cubic) in its tetragonal crystal structure. This unique structure gives martensite its characteristic properties.

Applications

Martensitic steels are used in areas that require high hardness and wear resistance, such as:

• Cutting tools
• Gears
• Ball bearings
• Surgical instruments

Formation of martensite

Martensite is formed through a diffusionless transformation process in which the carbon atom is ‘trapped’ and causes a distortion of the crystal lattice. This typically occurs through rapid cooling of austenite, similar to the stabilisation of austenite, but with different results.