The titanium stabilized 15Cr-15Ni austenitic stainless steel is used as clad and wrapper material for fast breeder reactors. It is currently the primary choice for the MYRRHA reactor fuel assembly and a nuclear-grade batch of cladding tubes and bars has recently been produced by Sandvik for SCK•CEN [1].
Description
It is therefore proposed to study the precipitation of fine secondary Ti(C,N) precipitates after thermal ageing of the 15Cr-15Ni clad and bar material at temperatures relevant for service operation and during storage. Besides the control of the heat treatment parameters, it includes the characterization by Transmission Electron Microscopy (TEM) of the amount and density of secondary Ti(C,N) precipitates. Aged specimens reinforced by the dispersion of nanoscale precipitates will then be tested mechanically to investigate the influence of ageing temperature on mechanical properties.
Standard tensile test specimens machined from the bars can be directly tested in the existing facility at SCK•CEN up to 600°C. Within this work, it is also planned to retrofit the tensile test machine with new heads specifically designed to perform tensile test on tubes. By looking at the evolution of stress versus strain for different ageing/test temperatures and by correlating these results with the microstructure analyzed by TEM on tensile test specimens, new knowledge will be gained on deformation mechanisms taking place and the role played by the fine dispersion of Ti(C,N) precipitates. Results shall eventually be used to derive a model describing the work hardening behavior valid in a certain temperature range by fitting the data with empirical relations (e.g. Ludwigson [15] equation). Softening behavior caused by dynamic recovery or recrystallization which may occur during accidents shall also be investigated by performing test at higher temperatures under stress.
Nr of positions available : 1
Research Fields
Engineering
Career Stage
Early stage researcher or 0-4 yrs (Post graduate)
Research Profiles
First Stage Researcher (R1)
Comment/web site for additional job details