Research On Forming Behavior And High Temperature Properties Of GH3536 Superalloy By Selective Laser Melting Technology

GH3536 superalloy is a typical solid solution strengthen nickel-based superalloy.Since it has excellent oxidation resistance and high temperature strength,GH3536 superalloy finds widely use in the hot combustor zone sections of aviation and aerospace and other parts serving at high temperature.To reduce the weight of the components,the geometry of advanced aeroengine components are becoming more and more complex bringing great difficulty to traditional processing technology.As one of the typical 3D printing technology,Selective laser melting(SLM)has great advantages in the manufacture of geometrically complex and hardworking parts.Considering above advantages,SLM has been welcomed by a wide range of industries such as aerospace and aviation industry.During SLM process,powder layer of local areas experience rapid heating/cooling phenomenon.Compared with traditional processed parts,SLM forming parts have larger internal temperature gradient and thermal stress,and are prone to develop defects such as holes and microcracks,which restrict the forming effect and service performance of materials.Therefore,it is necessary to study the control of internal pores,microcracks and microstructure and properties of SLM forming parts.To study Selective Laser Melting(SLM)process of GH3536 superalloy,optimize manufacturing parameters,reduce interior holes and microcracks of SLM samples and evaluate the service performance of SLM GH3536 superalloy,the effect of vary SLM mnaufacturing parameters on density,porosity and microcracks was investigated based on volumetric energy density.Microstructure,microcracks and Vickers hardness of thin wall tube were anslysed.Room temperature mechanical property and high temperature mechanical propety were tested.The mechanism of creep behavior and rupture were studed.All the properties and mechanism were made a comparisoin with GH3536 superalloy bars;A three dimension finite element model(FEM)was also introduced in this work to simulate temperature field,melt pool size and solidfication microstructure.The results showed that with the increase of the volumetric energy density,the porosity of specimens gradually decreased and disappeared,while intergranular microcracks emerged and increased;The overall microcracks growth directions are perpendicular to the scanning line directions and parallel to the building direction,spanning adjacent scanning lines and multiple deposited layers;Microstructures of SLM specimens are composed of molten pools,looking like fish scales morphology;Columnar grains spanning multiple deposited layers were observed and the distance of grains are about 0.6~1.5?m;SLM specimens have higher hardness and strength than GH3535 bar specimens,plasticity to the contrary.The creep resistance of SLM specimens is higher than bar specimens.For SLM specimens,creep cracks developed along the melt and columnar boundaries rather than the direction perpendicular to the stress.Melt tracks can be easily observed on the creep fracture surface for SLM specimens.The stress exponents of steady creep rate for both SLM and GH3536 bar specimens are similar in the range of 6.4~7.4;the results of the FEM for the melt pool size and solidfication microstructure are validated with the experiments results.