Concomitant Precipitation of Intermetallic β-NiAl and Carbides in a Precipitation Hardened Steel

The investigated steel is hardened by precipitation of both intermetallic β-NiAl particles and carbides. Around peak hardness, here reached after aging at 520 °C for 6 h, the number density of β-NiAl particles is 2.4 × 10 24 and 4.4 × 10 23 for carbides, respectively. The carbides and β-NiAl often form co-precipitates with presumably the carbides nucleating on the β-NiAl precipitates. The secondary carbides are mainly of the Cr-rich M 23 C 6 type in the investigated states. The steel has a good resistance against over-aging, whereby the β-NiAl coarsen considerably slower than the carbides.