Study On The Microstructure And High Temperature Mechanical Properties Of Selective Laser Melting Formed IN738LC

In the process of design and manufacture of advanced aero-engines,the requirements for weight reduction are getting higher and higher.By reducing splicing and assembly,it can not only better meet the weight reduction requirements of aero-engines,but also significantly improve the stability of aero-engines.At the same time,it can reduce the cost of various parts design and mold opening.However,the reduction of splicing and assembly will bring about the difficulty of manufacturing with traditional machining methods because the shape of the parts is too complicated.Selective Laser Melting(SLM)rapid prototyping technology is widely used in the formation of various key components with complex shapes in the aerospace field due to its unique advantages of directly forming precision and complex parts without molds.manufacture.In this paper,the laser selective melting rapid prototyping technology was used to form the IN738LC nickel-based superalloy.The influence of SLM process parameters and subsequent heat treatment on the microstructure and high temperature mechanical properties of the SLM formed IN738LC alloy was systematically studied.By comparing and analyzing the microhardness of deposited and heat-treated IN738LC alloy under different laser power and different laser beam scanning speed test conditions,the best process parameters of IN738LC alloy SLM forming are explored;by designing appropriate solution treatment+intermediate treatment+The compound heat treatment system of aging treatment reduces the difference in mechanical properties of IN738LC alloy formed by SLM in different directions.The SLM forming process parameters were designed with a scanning speed range of 700?1500 mm/s,a laser power range of 140?260W,a scanning distance of 100?m,a powder layer thickness of 30?m,a substrate preheating temperature of 180?,and a spot diameter of 60?m.Comparative analysis The microstructure of IN738LC alloy formed by SLM under different process parameters was found.It is found that under the test conditions of high laser power and high scanning speed,the grains of SLM formed IN738LC alloy are smaller and the grain orientation is weaker.The as-deposited IN738LC alloy was subjected to solution treatment at different temperatures and different holding times.It was found that under the test conditions of high laser power and high scanning speed,the microhardness of the IN738LC alloy formed by SLM was significantly higher than that formed under the conditions of low laser power and low scanning speed.With the increase of solution treatment temperature and holding time,the microhardness of IN738LC alloy decreased from 407.33HV to 365.83HV.Taken together,the SLM process parameters with a laser power of 260W,a scanning speed of1300mm/s,a scanning distance of 100?m,a powder layer thickness of 30?m,a substrate preheating temperature of 180°C,and a spot diameter of 60?m are the best.The effect of different heat treatment regimes on the microstructure and high temperature tensile mechanical properties of SLM formed IN738LC alloy was systematically studied.After the SLM formed IN738LC alloy was solution treated at1230?for 2h and then cooled with the furnace,the crystal grains were close to equiaxed morphology,with an average grain size of 151?m,and the grain orientation was weak.On the basis of the above solution treatment,the IN738LC alloy formed by SLM was subjected to an intermediate heat treatment at 1120°C for 2 hours and then cooled with the furnace.It was found that the microstructure of the IN738LC alloy has a high degree of coherence with the?-Ni matrix.Ni₃(Al,Ti)phase.On the basis of the above solid solution+intermediate heat treatment,the SLM formed IN738LC alloy was subjected to an aging heat treatment at 900°C for 24 hours followed by air cooling,and it was found that the tensile strength and reduction of area of the longitudinal samples at1000°C and 1100°C reached 385MPa,153MPa and 13%,15%.Comprehensive comparison shows that the best heat treatment system for SLM forming IN738LC alloy is:1230?×2h(furnace cooling)+1120?×2h(furnace cooling)+900?×24h(air cooling).