THE EFFECT OF THERMOMECHANICAL TREATMENTS ON SHORT-RANGE ORDERING AND CARBIDE PRECIPITATION IN A NI-CR BASED SUPERALLOY
The main purpose of this study is to describe the development of short-range order (SRO) in the Ni-Cr based superalloy Nimonic 75. Experiments were carried out and the results can be summarised as follows : - Order and precipitation phenomena in Nimonic 75 are found to be markedly dependent on cooling rate from solutioning temperature. Slow cooling produces copious carbides and a fairly ordered state, while water quenching retains carbon in solid solution and a fairly disordered state. - SRO kinetics are determined by nucleation of ordered zones, and carbon atoms in solid solution appear to delay this process. - Coldwork destroys SRO but produces non-equilibrium lattice defects which enhance diffusion and accelerate SRO formation and carbide precipitation during re-heating. - The formation of SRO in the presence of high dislocation density produces a noticeable increase in hardness, while no such increase is observed during ordering of undeformed material. - The recrystallisation of deformed material, revealed by marked hardness decrease, is delayed when carbide precipitation occurs after coldworking.
Bibliographic Reference: PAPER PRESENTED: EUROMAT 89, NOV. 22-24, 1989 AVAILABLE FROM COMMISSION OF THE EUROPEAN COMMUNITIES, DG XIII-C-3, L-2920 LUXEMBOURG AS PAPER EN 35145 ORA
Availability: Can be ordered online
Record Number: 1989128062300 / Last updated on: 1990-11-09
Available languages: en