Low temperature study of phase equilibria in the Co–Ni–W ternary system: Evidence of a new intermetallic phase Co3W-D0a

•A critical evaluation of the ternary Co–Ni–W thermodynamic description is conducted.•Experimental characterizations indicate that a new Co3W-D0a intermetallic phase is stable in the Co–Ni–W system.•A new description of phase equilibria at 800 °C and 1000 °C in the ternary Co–Ni–W system is proposed.•Intermetallic phases formation enthalpies are assessed with DFT and SQS calculations.