Study On Microstructure And Properties Of An Fe-Ni Based Wrought Superalloy

GH2107 is an Ni-Fe based wrought superalloy,its main application is in the turbine blades of 700℃ advanced ultra-supercritical boiler.GH2107 is based on the GH21035 by reducing 2% of Al+Ti.In order to further improve the microstructure stability and properities of the alloy at high temperature,We decide to adjust alloy composition.This paper focuses on the Fe,Cr,B and P content on microstructure and properties of GH2107 Alloy.It reveals the mechanism of Fe,Cr,B and P.The results of this paper show that:The major precipitates in the alloy were matrix γ,spherical γ′,MC and M23C6 carbide.The grain size of the alloy is 40μm~80μm after standard heat treatment.The grain is equal axis crystal which has small amount of annealing twins.Reducing the Fe content appropriately can lnhibit the harmful TCP phase(μ phase)precipitation,improve the thermal stability of the alloy GH2107.When Fe content is 41.6wt% in GH2107,after 725℃/3000 h long-term aging.TCP phase began to precipitate.After exposure to 10000 h,a large number of TCP phase precipitates.When Fe content is 35.3wt%,after 725℃/3000 h long-term aging,we find no TCP phase.After exposure to 6000 h,TCP phase began to precipitate a little TCP phase.Enriched Fe can reduce the solubility of the other elements to promote the growing of γ′ phase,it can also be appropriate to improve the hardness of the alloy.The tensile test show that: the character changes from dimple to intergranular.The dislocation motion of alloys are more prone Orowan bypass which is enriched Fe.Cr elements can promote M23C6 type carbide precipitate at the grain boundaries.B element is mainly enriched in grain boundaries which is in the form of M3B2.The P element is in the form of atomic group which is also enriched in grain boundary segregation.Suitable phosphorus content has a drag effect,which hinders the crack propagation and initiation.The B element can produce boride which has the screw pressure effect on the grain boundary of the Ni-Fe based superalloy GH2107.Hindering the grain growth.A small amount of B is favorable to the stress rupture properties of the alloy.The contents of B and P should not be too high,and the suitable content should be in the vicinity of 0.005% and 0.023%.Thermal expansion coefficient is an important index to measure the performance of superalloy.Cr and Fe can increase the thermal expansion coefficient,B and P also have significant effect.