Astaloy A case hardened
| Chemical designation | Astaloy A |
|---|---|
| State | case hardened |
| Etching | 3% Nital |
The sample made of Astaloy A (0.23% C; 0.2% Mn; 0.55% Mo, 1.9% Ni) was presumably HIPed (hot isostatic pressing) and then case hardened.
The core only achieves a hardness of 230 HV 0.5.
The core structure consists of upper bainite in the transition between acicular and granular.
The light-coloured grains are not ferrite, but only weakly etched, as can be seen after a longer etching time.
In the case-hardened edge zone, in addition to martensite and residual austenite (white in the background), there is also a considerable proportion of very fine-grained pearlite (formerly: troostite). The latter forms due to too slow cooling.
In the sintered component in question, the selected quenching speed was not sufficient for every grain due to the uneven distribution of the alloying elements.
