Experimental determination of the phase equilibria in the Co–Cr–Ta ternary system

• Three isothermal sections at 800, 1000, and 1100 °C were established.
• A large solubility of Cr is identified in the Co6Ta7 phase.
• The high–temperature phase (Co,Cr)2Ta(HT) was found to be stabilized at low temperatures.

The phase equilibria in the Co–Cr–Ta ternary system were experimentally investigated by using backscattered electron (BSE), wavelength dispersive X-ray analyzer (WDX) and X-ray diffraction (XRD). Three isothermal sections of the Co–Cr–Ta ternary system at 800 °C, 900 °C and 1100 °C were experimentally determined. The experimental results show that: (1) No ternary compound is found in this system; (2) A large solubility of Cr is identified in the Co6Ta7 phase; (3) The (Co, Cr)2Ta(HT) phase is stabilized at temperatures below it stability limits in Co–Ta and Cr–Ta binary systems in the range of Cr concentrations from 4 to 61 at.% and from 24 to 41 at.% Ta.