Oxidation behavior of dense Yttrium doped B2-NiAl bulk material fabricated by ball milling self-propagating high-temperature synthesis and densified by spark plasma sintering

The effect of Y additions on the oxidation behavior in furnace cyclic tests and its correlation with thermogravimetric analysis of sintered NiAl alloys is here reported. Part of the samples got an EB-PVD 7YSZ coating on top. Highly ordered B2-NiAl intermetallic powder was obtained by self-propagating high-temperature synthesis (SHS) during ball milling of elemental precursors with Y additions in amounts between 0 and 1.5 at.%. The SHS process was optimized to identify the combination of milling parameters that leads to a sharp increase in the reaction temperature for intermetallic synthesis. The tested samples consisted of NiAl-Y buttons densified by spark plasma sintering (SPS). Furnace cyclic testing of the SPS- buttons at 1100 degrees C showed high resistance to spallation of the 7YSZ top-coat and a significant decrease in its oxide growth kinetics attributed to Y-additions. Contents below 0.5 at.% Y reduce the oxidation kinetics of NiAl exposed to thermal cycles at 1100 degrees C, while higher Y contents are favorable for a longer TBC life.