Spark plasma sintering of cryomilled CoNiCrAlY powders

The influence of a cryomilling treatment in liquid N2 on the characteristics of Co-32Ni-21Cr-8Al-0.5Y powders is first investigated in this work. The cryogenic process is then followed by a consolidation step performed using Spark Plasma Sintering. Different morphology, particle size increase, crystallite size decrease down to nanometric level and higher sinterability are the most important changes observed in CoNiCrAlY powders after cryomilling. Correspondingly, a relatively finer micro structure is obtained in SPSed samples. Moreover, if samples obtained starting from cryomilled powders are exposed to an oxidizing environment at high temperature, a protective a-Al203 layer is produced on their external surface, while the formation of undesired unstable oxides is hindered. This result seems promising with the final aim of increasing high-temperature oxidation resistance in TBC of gas turbine engines.