Investigation on phase formations in nano oxide particles dispersion strengthened iron base alloys for nuclear reactor applications

Abstract

Oxide dispersion strengthened (ODS) alloy powders containing 0.33 wt% Y2O3, Ni, Al, Cr and Mn in Fe were consolidated through powder metallurgy route to study their metallurgical characteristics and mechanical properties. Twelve samples of 12 mm diameter × 5 mm thick were prepared by varying the compaction pressure from 50 to 150 bar and dwell time from 3 to 5 min. The green density of the compacts was calculated and found in the range of 4.7 to 5.9 g/cc for lower to higher compaction pressures respectively. Sintering of these compacts were done from 0.5 Tm to 0.7 Tm for 1 h. The sintered part density was observed in the range of 6.9 to 7.7 g/cc. Few sintered samples showed density nearer to the theoretical density of the alloy powders. Then the sintered samples were analyzed using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) equipped with Energy Dispersive Spectroscopy (EDS) to determine the phase formations during sintering process. SEM images confirmed the homogeneous distribution of nano yttria particles in the matrix of austenite and ferrite along with segregations of some precipitates. EDS reports also confirmed the in-situ formation of Ni-Al intermetallic. Sintered samples showed the hardness values ranging from 240 to 500 VHN. This confirms that the developed ODS parts may be a candidate material for nuclear reactor structural parts.