Development of The γ-γ'-Cr3C2 In-Situ Composite

ABSTRACTThe effects of various alloy additions to the microstructures and properties of the γ-γ'-Cr3C2 in-situ composite have been investigated. Combinations of platinum and Yttrium prevent the formation of an additional phase that occurs when Yttrium alone is added; the phase morphology is unaffected by rhenium and ruthenium dopants.Combined quenching studies and differential thermal analysis show that phase alignment at high growth rates in this alloy is not due to plane front solidification but to highly branched carbide growth ahead of the melt/ matrix interface. This mechanism allows good phase alignment to be achieved over a wide composition range. Tests on six alloy casts to commercial specifications indicate retention of, and often improvement to, the microstructures and properties obtained with laboratory control.