Study on Creep Properties and Microstructural Relation in Directionally Solidified Nickel Base Superalloy

摘要

Creep tests at temperatures ranging from 870 to975 deg C and stresses ranging from 70 to 350MPa areconducted on directionally solidified(DS) nickel base superalloyused for land base gas turbine blades in order to investigatebasic mechanical properties at high temperature. Creep rupturestrength of the material was about 20 deg C higher intemperature than that of conventionally cast (CC) superalloyThconel738LC. Ductility was a few times larger than that ofInconel738LC showing rupture elongation between 15 and 25percent depending on the creep test condition. Microstructureobservation performed on ruptured specimen showed so calledrafted #gamma#' precipitates specimens and aspect ratios of theprecipitates varied depending on the Larson-Miller parameter.Rafting of the DS superalloy leads enlargement of particlespacing and seems to cause the acceleration of the creep rate.