| As a key hot end component of aero-engine,the stress under turbine disc increases rapidly from rim to hub,while the temperature under turbine disc decreases rapidly.Dual-performance turbine disk with gradient structure can better meet the requirements of actual working conditions and give full play to the material potential.At present,the traditional method for preparing dual-performance turbine disks still has some difficulties,such as complex process,low yield and high cost.However,selective laser melting technology is expected to realize the integrated forming of gradient structure turbine disks due to its advantages of high flexibility,short processing period and high forming accuracy.In this paper,selective laser melting(SLM)technique was used to study the microstructure and properties of GH4169 alloy formed by SLM.The main research contents and conclusions are as follows:1)The microstructure and mechanical properties of GH4169 alloy formed by SLM were studied.GH4169 alloy formed by SLM has fine grain,which is mainly composed of columnarγ matrix phase and Laves phase with chain distribution between dendrites.γ matrix phase columnar crystals grow along the(200)crystal plane in the same direction as SLM construction,resulting in anisotropy of mechanical properties and higher tensile strength along the SLM construction direction.When the scanning speed is 800mm/s and the laser power is 180 W,the sample density is 99.12%,and the microstructure is columnar with a few equiaxed crystals.When the scanning speed is 1000mm/s and the laser power is 210 W,the sample density is98.96%.The tensile strength is higher than that of GH4169 alloy standard castings,but lower than that of standard forgings.2)The regulation law of "homogenization treatment + double aging treatment" on the microstructure and mechanical properties of GH4169 alloy formed by SLM was studied.After homogenization at 1030℃,the Laves phase dissolved and recrystallized,and the columnar crystals transformed to equiaxed crystals.When the homogenization temperature was increased to 1080℃,the Laves phase was completely dissolved.When the homogenization temperature was further increased to 1130℃,the columnar crystals were all transformed into equiaxed crystals,with few twins inside the grains and large size NbC particles distributed among the grains.After the double aging treatment,γ ’and γ "phases precipitate in the matrix,resulting in the tensile strength and microhardness of GH4169 alloy after heat treatment,and the tensile strength of some samples exceeds that of standard forgings.3)The integrated SLM forming of GH4169 alloy with gradient structure was studied.GH4169 alloy with longitudinal gradient structure and transverse gradient structure was successfully prepared by double SLM forming process composite design.GH4169 alloy formed by SLM has columnar crystal structure,but the grain size varies with different process segments.The area of process transition has good metallurgical bonding and fine equiaxed crystal structure.After heat treatment,relatively fine equiaxed crystals are formed at the scanning speed of 800mm/s and laser power of 180 W,while coarse equiaxed crystals are formed at the scanning speed of 1000mm/s and laser power of 210 W.After heat treatment,the tensile fracture locations of the gradient samples prepared along the construction direction were distributed in the scanning speed of 800mm/s,laser power of 180 W,the tensile strength reached1273.6±32.5MPa,the elongation of 12.4±0.8%.The tensile fracture position of the gradient sample prepared perpendicular to the construction direction is distributed at the junction transition of the gradient structure. |
