SLM成形GH3536合金组织与硬度的研究

Study on Microstructure and Hardness of GH3536 Alloy Formed by SLM

本文采用选区激光熔化技术(SLM)制备GH3536镍基高温合金,并研究不同工艺参数下合金孔隙率与硬度的变化,由孔隙率和硬度的变化选取本实验最好的工艺参数,对其进行显微组织的检测与分析。实验表明:激光功率为330 W,扫描速度为950 mm/s时,可计算得出能量密度为128 J/mm^(3),是SLM成形GH3536合金较为合适的工艺参数,合金表面基本无孔洞,而能量密度较低或较高时都会出现不同程度的孔洞与裂纹;随着激光功率与扫描速率的变化,衍射峰发生了偏移,这是由于基体Ni在SLM成形时发生了晶格的畸变。GH3536合金硬度整体上随能量密度的逐渐增大表现出先增大后减小的趋势,维氏硬度最高可达到255.04 HV。SLM成形方向组织呈不规则鱼鳞状熔池,熔池晶粒由等轴晶与柱状晶构成,这些柱状晶垂直于熔池边界呈逆温度梯度方向生长。

The selected laser melting technology(SLM)was used to prepare GH3536 nickel-based superalloy,and the changes of the porosity and hardness of the alloy under different process parameters were studied.The best process parameters were selected from the changes of porosity and hardness,and their microstructure was detected and analyzed.The test shows that:when the laser power is 330w and the scanning speed is 950 mm/s,the energy density can be calculated as 128 J/mm^(3),which a suitable process parameter for SLM forming GH3536 alloy.There are basically no holes on the surface of the alloy,and holes and cracks will appear in different degrees when the energy density is low and high;With the change of laser power and scanning rate,the diffraction peak is shifting,due to the lattice distortion of Ni matrix during SLM forming.As a whole,the hardness of GH3536 alloy increases first and then decreases with the gradual increase of energy density,and the highest Vickers hardness can reach 255.04HV.The microstructure of SLM forming direction is irregular fish-scale molten pool.Molten pool grains are composed of equiaxed crystals and columnar crystals.And the columnar crystals grow in the direction of inverse temperature gradient perpendicular to the molten pool boundary.