| The Inconel 718 nickel-base superalloy has been widely applied in turbine blades,combustion chambers and nuclear reactors due to its high strength,excellent oxidation resistance and hot corrosion.However,the high hardness of Inconel 718 superalloy will speed up wear and tear of machining tools,which causes great difficulties to its machining by means of traditional methods.The Selective Laser Melting based on Additive Manufacturing overcomes limitations of the traditional manufacturing process with a wide prospect in the production of Inconel 718 superalloy parts,which also affords the possibility to realize the complex structure manufacture and design freedom.This thesis studied laser process parameters and relevant structure properties of superalloy based on SLM Metal Additive Manufacturing technology.First of all,this thesis researched the influences of main laser process parameters on relative density and forming quality of samples prepared via SLM,and meanwhile the quadratic function was used to fit the relationship between relative density and laser energy density so as to further optimize the process window.Then,based on this,the tissue distribution and growth rules were explored based on test samples prepared via the optimized laser process parameters.Further,the microhardness,tensile property and high-temperature corrosion property of test samples prepared by SLM were measured accordingly.Study the relationship between additive manufacturing microstructure and alloy mechanics and corrosion resistance.The results show that it has a great influence on the forming quality of Inconel 718superalloy samples by laser process parameters such as laser power,laser moving speed and laser scanning interval.When the laser power ranges from 110 W～150 W,the laser scanning speed ranges from 430 mm s-1 to 630 mm s-1,and the laser hatch distance ranges from 0.05mm～0.08 mm,the sample forming quality is higher.When the laser energy density is around65 W·s·mm-3 within the optimized process parameters,the relative density of the prepared samples can reach above 93%,and the highest can reach 98.99%.There is a functional relationship between relative density and laser energy density:=-0.006762+0.94301+62.6094.The microstructure of the sample is mainly columnar crystals.The growth of microstructure in laser selective melting process is determined by the comprehensive action of temperature gradient G and solidification rate R,and the microstructure shows the characteristic of directional growth with continuous heating.The microhardness of Inconel 718 superalloy produced by SLM can reach about 300 HV on average,which is close to the hardness of Inconel718 superalloy produced by conventional casting and forging.The tensile strength of Inconel718 superalloy at room temperature reaches 1097 MPa,which is greater than that of cast alloy and close to that of forged alloy,and the elongation is greater than 28.5%.At 650℃,the tensile strength still reaches 939 MPa and the elongation exceeds 13%.Inconel 718 superalloy prepared by SLM has excellent high temperature corrosion resistance,and the change of sample mass after 120h is only 0.81‰. |
