Abstract:The effect of the micro-alloying elements (C, B, Zr), casting system and aging treatment on microstructure and mechanical properties of Ni based superalloy GMR235 was studied. The equilibrium phase diagram of the alloy was calculated by Thermo-Calc software. The results show that equilibrium phases contain γ, γ’, M6C, MC, M23C6 carbides and M3B2. Proper carbon addition can improve the rupture life of the alloy, keep its plasticity and increase the high temperature tensile properties. The addition of micro-alloying elements B and Zr can improve the high temperature stress rupture properties and plastic properties of the alloy, restraining the precipitation of the carbide and refining carbide particles. The optimum properties can be obtained when the mould temperature is 800 oC and tapping temperature is 1420 oC. Rupture life is significantly increased after 5 h aging with good plastic properties like as-cast alloys. g￠ coarsens as the aging time gets longer, decreasing the strength of the alloy at high temperature