J.X.Dong
,
M.C.Zhang
,
Y.P.Zeng
,
X.S.Xie
金属学报(英文版)
Alloy 718 is a precipitation strengthened nickel-hased superalloy based on the precipitation of γ’’-Ni3Vb(DO22 structure) and γ'-Ni3(Al, Ti) (Ll2 structure) phases. Creep crack growth rate (CCGR) was investigated after high temperature exposure at 593, 650 and 677℃ for 2000h in Alloy 718. In addition to the coalescence of γ'/γ'' and the amount increasing of 6 phase, the existence of a bcc chromium enriched α-Cr phase was observed by SEM, and the weight fraction of α-Cr and other phases were determined by chemical phase analysis methods. The CCGR behavior and regulation have been analyzed by means of strength and structure analysis approaches. The experimental results show higher the exposure temperature and longer the exposure time, lower the CCGR. This is probably attributed to the interaction of material softening and brittling due to complex structure changes during high temperature exposure. Therefore,despite α-Cr phase formation and amount enhancement were run in this test range. It seems to us a small amount of α-Cr will be not harmful for creep crack propagation resistance, which is critical for disk application in aircraft and land-based gas turbine.
关键词:
alloy 718
,
null
,
null
J.X.Dong
,
M.C.Zhang
,
Y.P.Zeng
,
X.S.Xie
金属学报(英文版)
The freckle formation and their phase characterizatics in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in an lnconel 625 alloy. These results show that in freckle areas a large number of M6C, MC, Laves and 8 phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and Nb during solidification, which results in almost of these freckle areas covered by these complex precipitated phases and induces small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give a reasonable interpretation of the freckle feature for this alloy.
关键词:
freckle
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null
,
null
J.X.Dong
,
M.C.Zhang
,
Y.P.Zeng
,
X.S.Xie
金属学报(英文版)
The freckle formation and their phase characterization in freckle areas were investigated by means of microstructure analysis approaches and a thermodynamic equilibrium phase calculation method in a Ni-Cr-Mo-Fe-W alloy. These results show that in freckle areas a large number of M6 C, u and P phases precipitate in grain boundaries even within grain due to the enrichment and segregation of Mo and C during solidification, which results in small grains in freckle areas. Equilibrium phase and liquid segregation calculation can give an reasonable interpretation of the freckle feature for this alloy.
关键词:
freckle
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null
,
null
J.X.Dong
,
M.C.Zhang
,
S.K.Mannan
金属学报(英文版)
INCONEL725 is a highly corrosion resistant nickel based alloy capable of being age-hardened to high strength levels.The microstructure observations and the phase iden-tification after a standard heat treatment were investiguted.The results show that the precipitation phases include the strengthening phases γ′，γ″and δ phase,pri-mary carbide phase TiC,as well as M6C corbide and a little extent MC(mainly TiC) precipitates which nucleate mainly at grain boundaries.An isothermal aging study was carried out on this alloy for up to 10000 hours at 599℃.This additional aging did not affect the tensile strength.However,microstructures show that the thermal exposure has a little additional effect.With increasing the exposure time,the size of γ″ phase slightly increases,almost no change for γ′ phase,while M6C carbides pre-cipitated at grain boundaries have an increased and complex tendency on a few grain boundaries.The experimental results illustuate the excellent structure stability of the age-hardenable IN725 at 599℃.
关键词:
superalloy
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null
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null
