Deformation and Damage Mechanism of a 4.5% Re-containing Nickel-based Single Crystal Superalloy During Creep at 980℃

Abstract

By means of creep property measurements and microstructure observations,an investigation has been made into creep behaviors,deformation and damage mechanism of a 4.5%(mass fraction,the same below) Re-containing,nickel-based single crystal superalloy at 980℃.Results show that,under the condition of 980℃/300MPa,the creep life of 4.5% Re alloy is 169h.In the initial stage of creep,the cubical γ'phase in alloy is transformed into the N-type rafted structure perpendicular to the stress axis.During the steady stage creep,the deformation mechanism of the alloy is dislocations slipping in γ matrix and climbing over the rafted γ'phase.In the last stage of creep,the deformation mechanism of alloy is dislocations slipping in γ matrix and shearing into the rafted γ'phase.On the one hand,the γ matrix channels with narrower feature increases the resistance of dislocations slipping;on the other hand,the super-dislocations shearing into the rafted γ'phase may cross-slip from{111}plane to{100}plane to form the dislocation configuration of K-W locks,which may restrain the slipping and cross-slipping of dislocations to improve the creep resistance of alloy.Moreover,the alternate activation of the primary/secondary slipping dislocations results in the twisting of the rafted γ'phase to promote the initiation of the cracks on the γ'/γ interfaces,and as the creep goes on,the cracks propagate along the direction perpendicular to the direction of stress axis,up to creep fracture,which is thought to be the fracture mechanism of the alloy during creep.

Keywords

• nickel-based single crystal superalloy
• rhenium
• creep
• deformation mechanism
• K-W lock