Process And Mechanical Properties Of GH4169,K418 And GH4169/K418 Gradient Component Fabricated By Laser Melting Deposition

Turbine disks and blades are important parts of aero-engines.Unfortunately,there are many problems of connecting between turbine disks and blades by using mechanical methods,such as fretting wear,cracks,overflow losses.The blisk has been designed to simplify the structure and improve the performance of thrust-to-weight ratio and reliability,thus,there are broad application prospects in the field of aero-engines.However,the blisk is a kind of complicated graded structure in the transition zone,thus,there are major challenges in manufacturing technology.Laser Melting Deposition(LMD)is a manufacturing technology that uses bottom-up approaches to depositing powder layer by layer.Functionally Gradient Materials(FGM)were prepared by varying the composition ratio of the two kinds of materials.In this investigation,GH4169 and K418 superalloy powders for turbine disk and and blade,respectively,were used as raw materials.Effects of laser deposition processing parameters on the height of deposition layer,width and depth of molten pool of GH4169 superalloy samples were investigated,and the optimal forming parameters were obtained.Focusing on the effects of laser powers,microstructure and mechanical properties of GH4169 formed samples were investigated.The optimum processing parameters of GH4169 and K418 superalloy samples were obtained based on the effects of porosity and crack density.The gradient materials of GH4169 and K418 superalloys were fabricated by LMD technic and the microstructure and mechanical properties of the deposited and heat-treated FGM materials were investigated systematically.Experimental results of GH4169 superalloy single track deposited layer vs single wall and bulk samples indicate that the optimum processing parameters are 600 W for laser power,10 mm/s for scanning speed,and 24 g/min for powder feeding rate.Porosity of the GH4169 bulk samples remarkably decreases and slightly increases subsequently with increasing of laser power.In particular,the porosity of the as-fabricated GH4169 achieves a minimum value of 0.284 vol%at the power of 600W.This sample exhibits excellent mechanical properties with yield strength of 587MPa,ultimate tensile strength of 903MPa and elongation at fracture of 13.6%,and the fatigue limit at room temperature is 227.1 MPa.In addition,the crack density of K418 bulk samples achieves a minimum value of 0.151 when the laser power is 700 W.GH4169 and K418 superalloy FGMs manufactured by LMD show that there is no obvious interface between the gradient layers.It is found that the FGM samples with y matrix,Laves phases,? phase,?' phase,carbides,the transition zone of the Laves phase and matrix is composed of dendrites.The phase composition of the different gradient regions is similar.As the content of K418 alloy increases in the gradient layer,the hardness of the FGM samples increases.After homogenization,solution and aging treatment,the dendritic structure of the FGM samples disappears,most of the Laves phase dissolved,and some needle-like ? phases are observed at the grain boundary in the 100%GH4169 region.With the increase of contents of K418 superalloy,the grain boundary disappears,the ? phases are reduced,and only carbides can be observed.As the time of homogenization treatment increases,the recrystallized grains increase and the ? phases distributed more uniformly.The hardness testing indicates that the hardness of the heat treated samples enable to reach the maximum value of the deposited FGM samples.The yield strength,ultimate tensile strength and elongation at fracture of the FGM sample treated by heat treatment is 726 MPa,1044 MPa and 13.2%,respectively,which has been reached the level of as-cast GH4169 and K418 alloy.