AN INVESTIGATION OF LAMELLAR STRUCTURES AND MINOR PHASES IN ELEVEN COBALT-BASE ALLOYS BEFORE AND AFTER HEAT TREATMENT

摘要

An investigation was conducted to determine the occurrence and nature of lamellar structures and minor phases, by the use of metallographic and X-ray diffraction studies, of the following cobalt-base high-temperature alloys: rolled, cast, and high-carbon Stellite 21, 422-19, X-63, 6059, 61, X-40, S-816, 1-336, and J.nThe microstructures of as-cast alloys were generally found to contain interdendritic minor phases, many of which are low-melting eutectics in addition, cast Stellite 21, 422-19, 61, and X-40 contained pearlitic structures. The only as-rolled alloy studied, Stellite 21, contained large carbide spheroids. Fine microconstituents in such forms as pearlite and feathery structures readily dissolved into the matrix upon solution treatment. In general, alloys with high carbon content (0.36 percent and above) and those with tantalum and niobium, contained appreciable quantities of undissolved large carbides after the solution treatment. Lamellar structures were produced in eight of the eleven alloys by heat treatments.