Supersaturated body-centered tetragonal structure produced by a diffusionless shear transformation when austenite cools faster than the critical cooling rate. Its hardness depends mostly on carbon: about 50 HRC at 0.3 percent carbon and roughly 64 to 66 HRC at 0.6 percent and above. As-quenched martensite is strong but brittle and highly stressed, so it is tempered almost immediately. Under the microscope it looks like fine needles or laths.
Surface is 61 HRC and the mount shows clean tempered martensite with no ferrite, release the lot.
Martensite hardness is set by carbon, not alloy. Adding chromium or molybdenum makes steel harden deeper, not harder.
Also heard as
- mart
Related terms
Austenite
The face-centered cubic form of iron that dissolves carbon and must form before steel can be hardened.
Ms temperature
The temperature at which martensite starts to form as austenite cools during a quench.
Tempering
Reheating hardened steel below its lower critical temperature to trade some hardness for toughness.
Glass hard
Fully hardened and untempered, so hard and brittle that a file skates off and a drop could shatter it.
Retained austenite
Austenite that fails to transform during the quench and survives at room temperature inside hardened steel.