The Effect Of Electromagnetic Stirring On Solidification Structure For Superalloy Inconel625

Inconel625superalloy demonstrates not only good tensile, yield strength, ruptur strength and plasticity but also excellent resistance to oxidation and corrosion in severely aggressive environments in high temperature environments. Hence, it has been used extensively in the aerospace, chemical industries, oil production, marine, and nuclear power industries. However, the high content of Nb in alloy compositions results in complex solidification process and severe elements segregation, which makes the subsequent thermal processing and heat treatment considerably difficult. On the other hand, Electromagnetic stirring (EMS) is an effective method to reduce or eliminate the segregation and porosity, accelerate the center overheating dissipation, increase the rate of equiaxial crystal, and reduce macrosegregation in alloy, etc. Thus we associate that EMS can be used in the solidification process of Inconel625superalloy, which will be very useful to study the solidification micro structure and the degree of elements segregation with EMS.In current study, Inconel625alloy bar was remelted by high-frequency electromagnetic heating in corundum crucible, and then EMS was used on the solidification process of the melt. Through taking samples from the specimen for analysis, the solidified microstructure and the degree of elements segregation were studied. Finally, the research acquired the influence law of EMS on microstructure and segregation.On this experimental condition, the following conclusions were obtained:(1) The primary dendrite were long and. slim with no EMS, but it changed into chick short type when EMS was used in the solidification process. The length of primary dendrite decreases with increasing the eletromagnetic stirring force. However, when the eletromagnetic stirring force got big enough, the length of primary dendrite would not change.(2) The second dendritic arm spacing has two values with EMS, one kind was bigger than the second dendrite arm spacing with no EMS, while another kind was smaller than the second dendrite arm spacing with no EMS. The value of the former increased from54.7μum without EMS to60μm with EMS. The value of the latter decreased from54.7μm without EMS to44μm with EMS.(3) The course carbides appeared around eutectic structure (y+Laves) with EMS, but the MC carbides of other regions were not changed with EMS. The size and the area of eutectic structure (y+Laves) increased first and then decreased with increasing of EMS frequency. When EMS current was100A, the peak value was2Hz; When EMS current was200A and300A, the peak value was5Hz.(4) There was no influence for the dendritic segregation of Ni and Cr elements with EMS. The degree of dendritic segregation Fe element decreased of increasing of EMS frequency. The degree of Nb and Mo dendritic segregation increased first and then decreased with increasing of EMS frequency. When EMS current was200A, the peak value was5Hz.(5) The dendritic segregation of Si, Cr and Fe elements in Laves phase were not changed with EMS. The content of Ni element has a minimum value at a frequency of2Hz. The Nb and Mo content increase first and then decreased with increasing of EMS frequency. When EMS current was200A, the peak value was5Hz.