Effect of substituting Mo for W on γ/γ′ partitioning behaviors of alloying elements in heat-treated second generation Ni based single crystal superalloys: An atom probe tomography study

The effect of substituting Mo for W on γ/γ′ partitioning behaviors of alloying elements in heat-treated second generation Ni based single crystal superalloys was investigated via atom probe tomography technique. Re, Cr, Co and Mo elements tended to distribute in γ phase, while Al, Ta and W elements tended to distribute in γ′ phase, and significant interfacial segregation was not found in experimental alloys. Moreover, substituting Mo for W obviously increased Re content in γ phase. Meanwhile, Re content in γ phase increased with increasing Mo + Cr content in single crystal superalloy, while Re content in γ′ phase decreased with increasing W + Ta content in single crystal superalloy. In addition, partitioning ratios of both W and Mo elements were positively correlated with Ta content in single crystal superalloy, and partitioning ratio of Ta element was inversely correlated with Ta/Al ratio in single crystal superalloy. Furthermore, substituting Mo for W increased the solid solution strength of γ phase but decreased the solid solution strength of γ′ phase.