Alloying Elements On Strengthening Phase Coarsening Behavior Of Co-8.8Al-9.8W Superalloy

With the development of aerospace enterprise,the requirement of aerospace engine performance is more and more high,And the stand or fall of engine relies on the overall performance of high temperature alloy.For a long time,nickel-based superalloy of ?/?? two phase coherent strengthen is widely used,but the limitation of their ability of bearing temperature,restricting the development of the alloy.In 2006,found that ?/?? two phase microstructure of Co-Al-W alloy is similar to nickel base superalloy.it is different from the conventional cobalt-based superalloy by carbide dispersion strengthening and solid solution strengthening of alloy elements,and thus received extensive attention of scholars both at home and abroad.Through researching alloying elements on strengthening phase coarsening behavior of Co-8.8Al-9.8W alloy,the influence of the main research results are as follows:At 1000?,different Ni content of Co-8.8Al-9.8W based superalloy heat treatment in high temperature and short time found 5Ni,10 Ni alloy in 10 h ?? phase dissolve;In 25 Ni and 35 Ni alloy,?? phase grow with aging time,?? phase morphology change from cubic shape to the irregular shape,finally gradually become globular,and volume fraction of ?? phase decrease;at 25 h volume fraction of ?? phase decreased significantly,extending the time,volume fraction ?? phase in alloy will continue to decrease until it reaches a certain balance or could disappear completely.?? phase coarsening behavior conforms to the theory of LSW coarsening,The coarsening rate of 25 Ni and 35 Ni alloy are 4.05667×10-25m3s-1 and 2.78492×10-25m3s-1 respectively,?? phase coarsening of 25 Ni is faster.During the process of aging treatment,along with the aging time alloy microhardness is reduced,microhardness of 15 Ni alloy is significantly higher than the other three alloys.1000?/5h~25h,microhardness of 15 Ni,25Ni and 35 Ni alloy change flatten out,drop smaller;microhardness of 5Ni alloy decreased significantly.Order of microhardness value: 15Ni>25Ni>35Ni>5Ni.The influence of temperature on the hardness of alloy is more significant.Adding different alloy elements in Co-8.8Al-9.8W based superalloy age treatment after 50 h,100h,200 h,300h at 870?,900? and 930?,?? phase size of five alloy increases with the increase of aging temperature and time,the number decreased significantly.?? phase of 2Ta,2Nb and 2Ti alloy keep high degree of cubic,margin of ?? phase don't observed balling phenomenon;And ?? phase of 2Mo and 2Ni alloy is cubic shape and nearly cubic shape,?? phase edge occur spheroidizing,and ? matrix channel widen obviously.Coarsening rate of 2Mo allo y is the biggest at 870? and 900?,Coarsening rate of 2Ni alloy is the lowest under three different temperature.K value of 2Ti alloy is lower than that of 2Ta and 2Nb alloys,but ?? phase size of the alloy is the biggest in all alloys.Under different temperature,increased from 870? to 900?,coarsening rate of five alloy showed a trend of decrease,at 930?,coarsening rate is much higher than 870?.The size of ?? phase meet the LSW coarsening theory under long-term ageing at 870?,900? and 930?.And microstructure of the alloys have different levels of harmful secondary phase under 870?,900? and 930?.With the extension of aging time,secondary phase of alloys increase.At 300 h,found secondary precipitated phase in four kinds of alloy microstructure except 2Ni alloy under 870?.In 2Mo alloy,there is massive D019(Co3W)phase at the grain boundary,and there appear a lot of long needle D 019 phase from grain boundary towards the intracrystalline extension.secondary phase of 2Nb and 2Ta alloy is the same as 2Mo alloy,but there is lump Co Al phase on the border of grain boundary in 2Ti alloy.There is no evidence of secondary phase in 2Ni alloy.It is found Co content as high as 80% above near the region of secondary phase,the formation of secondary phase consumes elements of the alloy possibly.