Influence of Nb content on phase precipitation behavior of new Ni–Co-based superalloys by selective laser melting
Jiahao Hu, Bing Zhou, Xiaochun He, Hongyao Yu, Guangbao Sun, Jiali Gao, Zhongnan Bi, Yuqian Du, Shangzhou Zhang
Abstract
In this paper, the evolution of the γ′ and η phases of new Ni–Co-based superalloy with different Nb contents was investigated using a combination of thermodynamic calculations and high-throughput selective laser melting (SLM). Thermodynamic calculations show that the increase of Nb content lowered the solubility temperature of the γ′ phase and caused the precipitation of the η phase. The alloys with the Nb gradient content prepared by SLM during aging at 800 °C for 100h indicated that the maximum volume fraction and size of the γ′ phase reach the maximum at 3.0–3.5% Nb. The elongated η phases enrichment in Ni, Ti, and Nb atoms precipitate for the Nb content higher than 2.2% Nb and prefer to grow longitudinally at the expense of the γ′ precipitates. Combining the influence of the Al/(Nb + Ta + Ti) ratio on the η precipitates, the addition of Nb content in the Ni–Co-based superalloys is less than 2.2%, which increases the high-temperature yield strength and tensile strength.