Microstructure And Mechanical Properties Of GH4169 Superalloy Fabricated By Electron Beam Direct Manufacturing

The GH4169 alloy was prepared by Electron Beam Freeform Fabrication or Electron Beam Direct Manufacturing technology in this paper.And matching relationship between process parameters of the technology was investigated,the microstructures characteristics of the deposited GH4169 superalloy were researched by metallographic microscope(OM),scanning electron microscope(SEM),energy specturm(EDS).The mechanical properties of the Electron Beam Direct Manufactured alloy were gained,and Effect of Heat Treatment on Microstructure and Mechanical Properties of the deposited Alloy were revealed.The main research results are as follows:Electron beam Current,wire feed speed and travel speed are the key parameters that affect the forming,the three process parameters match each other can ensure stability of wire feed and well forming.Single-road multilayer forming,with the layers increasing,the increase extent of the height is decline.The back and forth wire feed way will exacerbate the heat accumulation effect during the forming process,so single-rode multilayer forming should adopt on one-way wire feeding.Layer height and the interval width between two tracks have an important effect on multi-rode multi-layer forming.The intermittent forming way of multipass multi-layer is helpful to reduce the heat accumulation effect and improve structural homogeneity.The forming of GH4169 superalloy fabricated by Electron Beam Direct Manufacturing technology has good forming without obvious defects.Macroscopically present coarse columnar crystal,who grows along the direction of the deposition.The microstructure is elongated dendritic crystal,which show a strong orientation.The dendritic spacing is small,meanwhile coarse Laves band and a small amount of MC carbide are distributed in the dendritic.The occurrence of layer band structure decreased the structural homogeneity.In the Multi-layer and multi-passes samples appears the horizontal growth,s dendrites,near which has a few Laves phase and equiaxed crystal appears.Formed alloy,s macro-segregation is weak,but dendritic segregation was found between dendrites and branches.The microhardness of the single-pass multilayer deposited alloy form the substrate to the top show a rising trend.Multi-layer and multi-passes deposited alloy along the height direction the microhardness first rise and then within a long distance within a small range of fluctuations,and finally dropping rapidly,while both single-rode multilayer deposited Alloy and Multi-layer and multi-passes forming alloy the horizontal direction of microhardness shows a small fluctuation.The tensile strength of the deposited alloy at room temperature is low,but show good plasticity,and its the fracture mode is transgranular fracture.Layer band structure in the alloy after the solution treatment tends to disappear,dendrites are gradually weakened,too.Laves band between the dendrites weakened into a granular or even disappear.With prolongation of the holding time or increasing of the solution temperature the recrystallization appear in the alloy,and grains grow significantly.After solution annealed at 1100? for 1 hour,Layer band structure is basically eliminated,Laves phase between the dendrites and other regions is basically dissolved,thence alloy elements and the microstructure become homogenization.Grain grows obvious and some twins appear in that grains.Deposited GH4169 alloy,s preferred solution treatment process is 1100°C for 1 hour.Under homogenizing treatment at 1100°C for 1.5 hour and homogenizing treatments at 1100°C for 1.5 h plus ? aging treatment at 980? for 1h the dendritic structure greatly weakened,grain grows significantly,the latter heat treatment grain become finer but uneven distribution.Under Homogenization plus ? aging plus double aging treatment microstructure transform into a relatively fine equiaxed crystal,but uneven distribution.With prolongation the holding time or increasing the solution temperature the microhardness of the deposited alloy along the height direction gradually reduced,the original microhardness,s increasing law has disappeared.After solution treatment at 1100? for 1 hour microhardness along the height direction show a significant reduction and its curve is very smooth,microhardness of the same layer also significantly reduced.While after solution treatment at 1160? for 1 hour and 1100? homogenization for 1.5 hours the hardness is basically unchanged.After homogenization plus ? aging plus two-stage aging treatment the microhardness along the height direction and the same layer both greatly increased.After 1100? solution for 1 hour plus two-stage aging treatment or 1100? homogenization for 1.5 hour plus ? aging at 980? for 1 hour plus double-stage aging treatment alloy,s strength was significantly improved near the level of forging,but the latter elongation is higher.After heat treatment,tensile fracture still exhibits obvious ductile fracture characteristics,and the fracture mode is transgranular fracture.