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1.1274 | C100S +QW Superheated hardened

Numeric designation1.1274
Chemical designationC100S
State+QW Superheated hardened
Etching3% Nital

This hypereutectoid steel (sheet material with cross section = 2 x 30 mm) with 0.98% carbon (measured by OES; nominal: 0.95 – 1.05%) was austenitized at 900 °C for 30 min, quenched in water and not tempered.
The austenitizing temperature was above the temperature intended for this material (780 – 810 °C), so it was overheated.
Since the sample was not tempered after hardening, tetragonally distorted martensite is still present. In this state, the material has a very high hardness but at the same time a high brittleness (“glass hardness”).
In the SEM, the fracture surface therefore appears as very brittle, almost completely intergranular.
Microsection reveals a coarse squamous martensite microstructure with quite high residual austenite content.
The core hardness averages 846 ± 7 HV1.

900 °C / 30 min / water