Precipitation behaviors of the rapidly-solidified Allvac 718Plus superalloy during aging treatment

Allvac 718Plus alloy is a newly-developed Ni-based superalloy with excellent thermal stability and mechanical performance at elevated temperatures up to 704 degrees C. The precipitation behavior of the rapidly-solidified Allvac 718Plus superalloy during aging is systematically investigated in this work. The microstructure evolutions of the strengthening gamma' phase and the gamma'/gamma'' co-precipitates during aging are examined. During aging, the duplet gamma'/gamma'' and triplet gamma''/gamma'/gamma'' occur and then disappear due to the dissolution of gamma'' phase, which is promoted by the delta precipitation. On the contrary, the triplet gamma'/gamma''/gamma' forms and remains after aging, resulting from the low diffusion rate of solute atoms through the spheroidal.' precipitates. The lamellar delta-Ni3Nb phase occurs at grain boundaries. Its size and content increase with the prolongation of aging time. After long-term thermal exposure, the hexagonal eta phase forms at the delta-gamma interface due to the variations of local chemical composition, and then the tetragonal Cr-rich sigma phase nucleates adjacent to the delta and eta particles because of the segregation of Cr atoms rejected from the delta and eta particles.

Automated summary

In this work, the precipitation behavior of Allvac 718Plus superalloy during aging is investigated. The evolution of the strengthening gamma' phase and the gamma'/gamma'' co-precipitates during aging is examined, and the formation of delta-Ni3Nb phase, eta phase, and sigma phase is also studied. The research findings provide insights into the microstructural changes that occur in Allvac 718Plus alloy at elevated temperatures.