Eutectic structures in the Ni–Co–Cr–Al system obtained by plasma spraying and by Bridgman growth

Formation of a regular fibrous two-phase microstructure was found in low-pressure plasma spray (LPPS) deposited Ni–Co–Cr–Al–Y coatings by transmission electron microscopy and analyzed by energy dispersive spectroscopy. The structure is compared to aligned lamellar three-phase structures of an Ni–Co–Cr–Al alloy obtained on Bridgman growth under slow unidirectional solidification (UDS) conditions. The composition of the Ni–Co–Cr–Al alloy for UDS experiments has been identified by DTA. The conditions for the formation of both the LPPS and the UDS structures are discussed.