Abstract: A series of nickel based superalloy samples with different P contents were prepared by vacuum induction melting and atmosphere protection electro slag remelting. The effect of P element on the microstructure and mechanical properties of the alloy was systematically analyzed using advanced characterization techniques such as optical microscopy, scanning electron microscopy, electron probe microanalysis, Vickers hardness tester, and tensile testing machine. The results show that the grain structure and γ' phase of the as cast alloy with different P contents have no significant change. With the increase of P content, the density of carbides at the grain boundaries increases, and the morphology of carbides changes from point like to short rod-shaped. The segregation of P element at grain boundaries reduces grain boundary energy, decreases the critical nucleus size for carbide, thus promoting the precipitation of carbides. In addition, as the P content increasing, the hardness, impact toughness, and tensile strength of the alloy increase, while the elongation decreases. Carbides at grain boundaries can effectively hinder the propagation of cracks, causing them to deflect and shift from the grain boundaries to the interior of the crystal, thereby significantly improving the comprehensive mechanical properties of the alloy.

Key words: nickel based superalloy, P element, vacuum induction melting, cast microstructure, mechanical property