Crystal structure and micro hardness studies on RE and

Crystal structure and micro hardness studies on RE and non RE additions in Ni3Al superalloys
Vivek R Rao, Selva Vennila Raju, Surendra K Saxena
CeSMEC, Department Of Mechanical Engg., Florida International University, Miami, FL USA
Abstract: Trace quantities of Rare-Earth additions in Ni based superalloys are known to enhance the
strength of superalloys significantly [Kuang-Di Xu et al., Rare. Met. 2014]. In the search of improved nonRare Earth superalloys, we have studied the following systems 1. Ni3Al with Ce additions 0.05, 0.1, 0.15
and 0.2 at % and 2. Ni-Al-Cr with Zr additions with concentrations 0.05, 0.5, 1, and 1.5 at%. We have
chosen Ni-Al-Cr as our base alloy as it forms well known two phase system with γ’ phase in a γ matrix
and Cr additions improves oxidation resistance and ductility [Raju et al., J. Alloys and Compounds 2015].
Both the alloys were synthesized by arc melting under inert atmosphere followed by heat treatment. In
the present work. In-situ powder x-ray diffraction and micro hardness studies were carried out. Micro
Hardness of Ni3Al with Ce addition increases from 0.05 at% up to 0.15 at% and thereafter hardness is
found to decrease for 0.2 at%. In case of Zr addition from 0.05 to 1.5 at%, No significant changes in
hardness was observed. The data from Vickers hardness test clearly shows addition of Zr in Ni-Al-Cr alloy
has greater hardness when compared to Ni-Al-Ce alloy. Possible reason for the observed hardness
change with chemical composition with respect to phase analysis and microstructure will be discussed.
Acknowledgements: The authors acknowledge support from the Air Force Office of Scientific
Research (Grant No. FA9550-12-1-0456).