Precipitation of γ’ during cooling of nickel-base superalloy Haynes 282
Ceena Joseph, Mattias Thuvander, Christer Persson, Magnus Hörnqvist Colliander
Abstract
Cooling-induced precipitation of the strengthening γ’ phase is commonly investigated in Ni-base superalloys with a high γ’ volume fraction, where it is used to control the final microstructure and properties. Less is known about the phase separation in low-volume-fraction alloys during cooling, although the microstructural state after cooling from solution treatment is known to affect subsequent heat-treatment steps. We use atomic-scale characterisation of Ni-base superalloy Haynes 282 (equilibrium γ’ volume fraction around 20%) to show that air cooling after solution or carbide stabilisation results in precipitation of nm-sized γ’ particles, whereas precipitation was suppressed during water quenching. The solution treatment has a significant effect on the hardness and γ’ precipitation during air cooling from the subsequent carbide stabilisation temperature. Also, the carbide-stabilisation treatment itself affects the γ’ precipitation during subsequent air cooling.