Study On Properties Of GH4169 Alloyformed By Selective Laser Melting

As one of the important components of equipment and parts in the aerospace field,nickel-based superalloys are difficult to form parts with complex internal structures through traditional cutting methods.Selective laser melting(SLM)is a kind of additive manufacturing technology,which can form parts by stacking and cooling.However,there are many factors that affect the overall performance of SLM technology formed parts,such as various designed process parameters in the forming process.In this paper,the SLM forming GH4169 alloy,is studied by following three aspects in detail.Firstly,the two significant parameters(scanning speed,scanning power)in the forming process were studied,and then the microstructure and mechanical properties of the three different scanning paths forming samples were investigated respectively.Finally,the mechanism of heat treatment on the microstructure and mechanical properties of GH4169 alloy by SLM was also studied.The main research results are as follows:1.When the scanning power is 140W and the scanning speed is 400mm/s,the formed single-wall wall has no defects such as collapse,cracks,and warpage.The formed single wall of molten pool is superior to that by other parameters.2.Using optical microscopy(OM),scanning electron microscopy(SEM),X-ray diffraction(XRD),transmission electron microscopy(TEM),and electron back scatter diffraction(EBSD),etc.to study the microstructure of the three scanning paths shaped samples.It is concluded that the metallographic structure of the sample is more homogeneous when the formed scanning path of upper and lower two layers at an angle of 45°,and no small cracks are generated.And the precipitated Laves phase are observed by scanning electron microscopy.Through phase analysis and TEM observation,the strengthening phase?"(Ni₃Nb)is generated,and the size of matrix grains are relatively fine by EBSD.3.The mechanical properties of the specimens formed by three different scanning methods show that,the tensile strength of the specimens formed by the 45°angle forming method reaches to 1115MPa.The elongation rate of the sample formed by the67°forming angle reached to 37.8%,which is slightly higher than the sample formed by the 45°forming angle method.By observing the fracture morphology,it was found that the size of the dimples of the sample formed by the 45°forming angle is relatively large.The microhardness of the samples formed by three different scanning methods is also tested.It is found that the microhardness of the samples formed is 320HV by 45°scanning paths,which is higher than that of the other two forming methods while lower than 350HV of the forgings.4.The phase analysis shows that the samples after heat treatment have strengthened phase?phase and?"(Ni₃Nb)phase precipitation.SEM studies indicate that the Laves phase almost disappeared while the?phase is distributed during the crystals.TEM analysis shows that the samples precipitated?"and?'phases.The EBSD results show that the heat treatment changed the orientation of the matrix.5.After heat treatment,the mechanical properties of the samples are excellent,and tensile strength is 1462MPa,which is15%higher than that of forgings.Its average elongation of heat-treated samples is 26%.The hardness of the sample after heat treatment is 513HV,which is 47%higher than that of standard forgings and 60%higher than untreated samples.The density of heat-treated samples(99.87%)is larger than the untreated samples(98.15%),but slightly smaller than the standard forged samples(99.99%).