1977 Volume 63 Issue 14 Pages 2381-2390
High temperature aging structures and age hardening of Ni-20Cr-20W alloys developed as the superalloys for the nuclear energy steelmaking, and effects of C and Zr additions to the alloys and the effect of preheat treatment on these properties were studied.
M6C, α-W and two kinds of M23C6 having different lattice parameters were found as precipitates in the alloys. M23C6 whose lattice parameter was around 10.7A precipitated in the early stage of aging at 700°C-1150°C, and the carbide changed to M6C at higher temperature than 1000°C, but it remained as a stable carbide at lower temperature than 900°C.
α-W precipitated at 800°C-1100°C after precipitation of M23C6 and it disappeared with increase of M6C. M23C6 having the larger lattice parameter (10.9Å) precipitated transitionally in aging stage of 26×103 in Larson Miller parameter at 900°C and 1000°C.
Age hardening corresponded to the precipitation of M23C6 and it was reduced by the double pre-heattreatment.
Zr addition and amount of C influenced on the aging structure and age hardening. Zr seemed to be a favorable element to stabilize the carbide.