scholarly journals Ultra-High Temperature Creep of Ni-Based SX Superalloys at 1250 °C

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1610
Author(s):  
Satoshi Utada ◽  
Lucille Després ◽  
Jonathan Cormier
Keyword(s):  
High Temperature ◽  
Creep Strength ◽  
Volume Fraction ◽  
Lattice Parameter ◽  
High Temperature Creep ◽  
Parameter Mismatch ◽  
Dislocation Glide ◽  
Temperature Creep ◽  
Rate Limiting ◽  
Applied Stresses

Very high temperature creep properties of twelve different Ni-based single crystal superalloys have been investigated at 1250 °C and under different initial applied stresses. The creep strength at this temperature is mainly controlled by the remaining γ′ volume fraction. Other parameters such as the γ′ precipitate after microstructure evolution and the γ/γ′ lattice parameter mismatch seem to affect the creep strength to a lesser degree in these conditions. The Norton Law creep exponent lies in the range 6–9 for most of the alloys studied, suggesting that dislocation glide and climb are the rate limiting deformation mechanisms. Damage mechanisms in these extreme conditions comprise creep strain accumulation leading to pronounced necking and to recrystallization in the most severely deformed sections of the specimens.

MTEK 25-35MA

Alloy Digest ◽  
2016 ◽  
Vol 65 (9) ◽  
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Creep Strength ◽  
Heat Treating ◽  
Casting Alloy ◽  
High Temperature Creep ◽  
Temperature Creep ◽  
Temperature Performance

Abstract MTEK 25-35MA is a solid solution microalloyed Fe-Ni-Cr-Nb casting alloy with good high-temperature creep strength. It is intended for use in pyrolysis cracker furnaces. This datasheet provides information on composition, physical properties, and tensile properties as well as creep. It also includes information on high temperature performance as well as casting, heat treating, machining, and joining. Filing Code: SS-1249. Producer or source: MetalTek International. Originally published July 2016, revised September 2016.

A Micromechanical Theory of High Temperature Creep

1987 ◽  
Vol 54 (4) ◽  
pp. 822-827 ◽  
Author(s):  
G. J. Weng
Keyword(s):  
High Temperature ◽  
Normal Stress ◽  
Creep Property ◽  
Dislocation Climb ◽  
High Temperature Creep ◽  
Dislocation Glide ◽  
Temperature Creep ◽  
Effective Normal Stress ◽  
Third Invariant ◽  
Transient And Steady State

Based on the mechanism of dislocation climb-plus-glide, a micromechanical theory is developed for the high-temperature creep of polycrystals. This model assumes that dislocation climb is responsible for the release of dislocations and whose subsequent glide provides the only significant contribution to the overall creep strain. Taking into consideration the forces acting on both dislocation climb and dislocation glide, a microconstitutive equation is introduced to describe the transient and steady-state creep of slip systems. Together with the self-consistent relation, the creep property of a polycrystal is determined by an averaging process over the behavior of its constituent grains. The developed micromechanical theory is then applied to model the creep behavior of lead at 0.56 Tm, under both tension and shear. Based on these micromechanical analyses, a macroscopic multiaxial theory—involving an effective normal stress to reflect the climb force on the microscale as well as the usual effective shear stress—is also developed. It is found that the effective normal stress, which is independent of the hydrostatic pressure, depends primarily on the second invariant of the deviatoric stress, and only weakly so on the third invariant. Thus despite the distinct presence of two types of microstress, the constitutive equations on the macroscale can still be reasonably described by the second invariant alone even at high temperature.

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