Effects of Cr and Al additions on the $\gamma/\gamma'$ forming Co-Ti-W-based alloys

Abstract

The effects of Cr and Al on the Co-Ti-W alloys with respect to atomic partitioning tendency and high-temperature properties of Co-Ti-W-based alloys containing $\gamma$/$\gamma$' phases were observed. Cr additions to a Co-Ti-W base alloy caused a decrease in $\gamma$' volume fraction, while additions of Al caused substantially increases of $\gamma$' volume fractions. These alloy designs resulted in decreased lattice misfits of $\gamma$/$\gamma$' phases. Ti and W partitioned to the $\gamma$' phase, while Co, Cr, and Al partitioned to $\gamma$ confirmed by APT. Thermal property, mechanical property, and oxidation resistance of the alloys were also measured. The thermal stability of the $\gamma$' phase increased with the addition of Cr and Al and the yield stress changed greatly at high temperatures. However, the added amount of Cr and Al was small and the increased resistance to oxidation was not identified.