| Inconel 718(IN718)is a Ni-Cr-Fe based superalloy mainly used for manufacturing of gas turbine blades in aerospace and aerospace engines.At present,this alloy is mainly prepared by casting,forging and powder metallurgy methods.These methods require a high preparation temperature and therefore coarsenning the crystal grains.Compared with casting and forging,the superalloy prepared by powder metallurgy obtains better mechanical properties.However,the IN718 alloy prepared by powder metallurgy has a long sintering time and needs to be solution treated before aging treatment.In order to solve the problem of long preparation period of traditional sintering methods,this paper proposed the preparation of IN718 alloy by spark plasma sintering(SPS)method,and the effects of solution and aging treatment on the microstructure and properties of IN718 alloy were studied.Also,the densification mechanism during sintering was analyzed.The results show that the highly-compact IN718 alloy was successfully prepared by SPS using IN718 alloy powder produced by plasma rotating electrode process(PREP).After SPS,sample microstructure reveals the dendrite segregation,in which Al,Ti,Nb elements are easily segregated at the dendrite arms,while Cr,Fe,Ni elements tend to segregate between the branches.These microsegregations were eliminated after solution treatment and aging.Compared with the hot isostatic pressing(HIP)method,these SPS-fabricated alloys have a simpler preparation process and a higher preparation efficiency.The SPS-fabricated IN718 alloy was treated by solid solution + aging treatment and direct aging treatment,and the microstructure and properties of the samples were characterized and tested.The results show that the mechanical properties of the alloy were significantly improved after solution treatment and aging,the mechanical properties are also improved.At the same time,the density of the sample is also improved after heat treatment.After direct aging treatment,the mechanical properties of the sample are better than those of the solid solution + aging standard heat treatment.The technique of transmission electron microscopy(TEM)was used to characterize the precipitation of ?”/?' phases in different samples.The results show that the amount of ?”/?' phases in 1000AC+aging samples is larger than that in the samples after standard heat treatment process for as-cast IN718 alloy(950 °C solution + aging).In the directly aged samples,the strengthening phases are denser and the size does not grow significantly.The research results provide an efficient preparation method and heat treatment process for IN718 alloy,which significantly improves the preparation efficiency of the alloy and reduces the production cost. |
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