Role Of Ru And Re In Co-Al-W-based Precipitation Strengthening Superalloys

The high temperature strength of conventional cobalt-based superalloys is lower than that of nickel-based superalloys due to the lack of stable L12 precipitation strengthening phases.The discovery of Co-Al-W based Precipitation-Strengthened superalloys has created new possibilities for the development of new cobalt-based superalloys,and has rapidly become one of the hot spots in the research of superalloys.Compared with nickel-based alloys which have been studied for a long time,the research on Precipitation-Strengthened cobalt-based superalloys is very limited.The known research mainly focuses on the volume fraction of?'-phase,the stable existence temperature of?'-phase and the composition ratio.The effects of alloy composition on precipitation phase,volume fraction of?'-phase,particle size and distribution coefficients of elements in Co-Al-W based Precipitation-Strengthened superalloys and the corresponding relationship between lattice mismatch and strength of?/?'-based Precipitation-Strengthened superalloys have not been systematically studied.In this paper,Ru and Re elements are selected as the research objects,and the effects of Ru and Re addition on the structure and properties of the alloy are analyzed.The mechanism of action of Ru and Re is analyzed in terms of the types,distribution,size and composition of precipitated phases,lattice constants and mismatch,room temperature hardness,high temperature yield strength and tensile strength.The main conclusions are as follows:When Ru and Re are added at 2%?at.%,same below?,the structure of?and?phases can be formed,and the?and?phases are in conformity.The addition of 4%Ru resulted in almost no precipitation of?'phase,while 4%Re resulted in a large amount of?-Co₃W precipitation in the alloy.The addition of Ru and Re has a certain effect on the precipitation phase.The addition of Ru will facilitate the precipitation of?-Co₃W phase.The addition of Re will promote the precipitation of?-Co7W6 phase in 1Ru alloy.In addition,the change of Re and Ru content may also cause a small amount of precipitation of CoAl.The addition of Ru and Re can obviously regulate the lattice mismatch of the alloys.The mismatch of the two phases is 0.528%.With the increase of Ru and Re,the lattice mismatch of the two phases increases first and then decreases.The corresponding compressive yield strength of the alloys corresponds to it.Higher lattice mismatch usually has higher temperature.Yield strength.The addition of 1%Ru and Re alloying elements can effectively improve the mismatch of the two-phase lattice of?/?',which reaches 1.09%and0.69%respectively.The yield strength of the alloy reaches 663 MPa and 489 MPa,respectively,and the maximum strength of the alloy is obtained by adding different amounts of the same element.The addition of 1%Ru and 0.5%Re can effectively improve the room temperature hardness of the alloy,reaching 530 MPa and 429 MPa,respectively.With the addition of 0.5%,2%and 4%Ru,the room temperature hardness of the alloy increases linearly,401.92 HV,432.07 HV and 504.36 HV,respectively.The addition of 1%,2%and4%Re did not increase the hardness of the alloy at room temperature,413.37 HV,394.84HV and 397.47 HV,respectively.The addition of 1%Ru and 0.5%Re is beneficial to the growth of the?'-phase,and the volume fraction of the?'-phase and the size of the?'-phase in the alloy are obviously increased.The volume fraction and particle size of 1%Ru alloy are83.71%and 119.59 nm respectively,while that of 0.5Re alloy are 64.63%and 122.64 nm,respectively.The addition of 4%Re in the phase is spherical with smaller lattice mismatch and smaller volume fraction of the phase.The volume fraction of?'phase in 0.5%and 1%Ru alloys decreases by hot compression at 900 temperature,and the volume fraction of?'phase in 0.5Ru alloys decreases slightly.Hot compression promotes the coarsening and growth of?'phase in 1Ru and 2Ru alloys.After hot compression,the volume fraction of?'phase increases in alloys with 1%and2%Re content.With the increase of Re content,the increase degree is greater,and the change trend of the average particle size of?'phase is also consistent with that of alloys with 1%and 2%Re content.The larger the volume fraction of the conforming phase,the larger the average particle size of the phase.