Effect Of Ru On Microstructure And Creep Properties Of Ni Based Single Crystal Superalloy Containing 4.5%Re

In this dissertation,two kinds of 4.5%Re and 4.5%Re/3%Ru nickel-based single crystal superalloys were designed and prepared.By means of heat treatment and creep properties measurin? of the alloys combined to microstructure observation and XRD diffraction analysis,the effects of the element Ru on composition segregation,lattice misfit and creep properties of superalloys are investigated.The deformation and damage mechanism of alloy durin? creep at medium and high temperatures are discussed.The results show that addin? element Ru may reduce the segregation degree of the elements Cr,Mo,Ta,W,Re in the dendrite arm and inter-dendrite regions of as-cast Re-containin? superalloys,to restrain the precipitation of TCP phase in alloy.After the Ru-containin? alloy is fully heat treated,the content of the elements Mo,W,and Re in ? and ?' phases can be obviously reduced and increased,respectively to decrease the distribution ratio of elements in the ?'/? phases,which may obvious improve the alloyin? degree of ?',? phases and creep resistance of alloy.Therefore,after the Re-containin? alloy adds 3%Ru,the creep life of the alloy at 1040?/160 MPa increases from 302 h to 724 h,respectively,and the creep life of the alloy at 1100?/137 MPa increases from 164 h to 321 h,respectively.After the element Ru adds to the Re-containin? alloy,the lattice parameters and misfits of ?' and ? phases at room temperature are increased.Durin? creep of alloy at high temperature,the bigger misfits result in the increment of lattice strain of the rafted ?'/? phases to diminish the spacin? of interface dislocation network,which is thought to be one of reasons for the alloy havin? an improve creep resistance at high temperature.The creep lives of the 3%Ru alloy at 800?/750 MPa and 780?/770 MPa are measured to be 706 h and 630 h,respectively.After crept up to fracture,the ?' phase in the alloy still maintains the cubical configuration.Wherein,the initiation and propagation of the cracks alon? the ?' and ? phases interfaces perpendicular to the stress axis occurs up to fracture,which is thought to be the damage and fracture mechanism of alloy durin? creep at medium temperature.The deformation mechanism of Ru-with/free single crystal alloy durin? steady state creep at high temperature is dislocations slippin? in ? matrix and climbin? over the rafted ?' phase.The deformation mechanism of alloy in the later stage of creep is the dislocation shearin? into the rafted ?' phase.As the creep goes on,the alternatin? slippin? of dislocations in the rafted ?'/? phases causes the initiation and propagation of cracks alon? the interfaces of ?'/? phases.And then the size of the fine cracks gradually increase until the creep rupture of alloy occurs,which is thought to be the damage and fracture mechanism of alloy durin? creep at high temperature.