Influence Of Ru Element On Microstructure And Creep Property Of A Single Crystal Nickel-based Superalloy

By designing and preparing the Ru-free/with single crystal nickel-based superalloys,by means of heat treatment at various regimes,creep properties measurement and microstructure observation,the influences of heat treatment regimes and element Ru on the microstructure and creep properties of the containing 4%Ru single crystal nickel-based superalloy are investigated.And the effect of temperature on the stacking fault energy and deformation mechanism of the 4%Ru alloy are discussed by thermodynamic method for calculating the stacking fault energies of the alloy at different temperatures.The results show that the needle-like TCP phase precipitated in the Ru-free superalloy during creep is thought to be the main reason of the one having weaker creep resistance,adding the element Ru may restrain the precipitation of TCP phase to improve the creep life of single crystal alloy.After aged at 1050℃?3h A.C and fully heat treated,the 4%Ru alloy may obtain the better microstructure and creep properties.Wherein,the creep properties of the alloy at 760℃/780 MPa,980℃/200 MPa and 1100℃/120 MPa are measured to be 523 h,333h and 232 h,respectively.During creep at temperature being below 850℃,the ?? phase in the alloy keeps still the cubical configuration,and the deformation mechanism of alloy during creep is dislocations slipping in the ? matrix and shearing into the ? ? phase,wherein the dislocations shearing into ?? phase may be decomposed to form the configuration of the partial dislocation plus stacking fault.During creep at temperatures higher than 980℃,the ?? phase in alloy has transformed into the rafted structure along the direction perpendicular to stress axis,and the deformation mechanism of alloy during steady-state creep is dislocations slipping in the ? matrix channel and climbing over the ?? phase.The deformation mechanism in the latter stage of creep is the dislocations slipping in the ? matrix channel and shearing into the rafted ??phase,and the dislocations shearing into the rafted ?? phase can not be decomposed.The effect of temperature on the stacking fault energy is thought to be the main reason of displaying the various deformation mechanism of the alloy at different temperatures.The alloy has lower stacking fault energy when temperature is lower than 850℃,therefore,the dislocations shearing into the ? ? phase may be decomposed to form the dislocation configuration of partial dislocations plus the stacking fault.But the stacking fault energy of the alloy increases with the creep temperature,which is the main reason which the dislocations shearing into ? ? phase can not be decomposed.In the latter stage of creep,the alternated activation of the primary / secondary slipping dislocations in the alloy results in the coarsening and distorting of ?? phase to promote the initiation and propagation of cracks along he ??/?interface perpendicular to the stress axis up to the occurrence of creep fracture,which is thought to be the damage and fracture mechanism of the alloy during creep at high temperature.