热处理对激光立体成形Inconel718高温合金组织和力学性能的影响

Effect of Heat Treatment on Microstructure and Mechanical Properties of Laser Solid Forming Inconel 718 Superalloy

研究了热处理对激光立体成形(LSF)Inconel 718微观组织和力学性能的影响规律。结果表明,激光立体成形Inconel 718经直接时效(DA)处理后,与沉积态相比,组织特征变化不大,具有较强生长取向性的外延枝晶组织特征,硬度和拉伸强度均明显提高,而经均匀化、固溶和双级时效(960STA)热处理后,枝晶间Laves相颗粒完全固溶,Nb偏析降低,细针状δ相沿晶界析出,合金性能得到进一步改善,室温、高温拉伸强度和塑性都达到了高强锻件的技术标准Q/3B 548-1996(高强)。DA状态下合金断口形貌与沉积态相似,韧窝具有沿列状枝晶取向排布的各向异性特点,而经过960STA热处理后,各向异性现象消失。

The effects of heat treatment on the microstructure and mechanical properties of laser solid forming Inconel 718 superalloy have been investigated. As compared with as-deposited samples,direct aged （DA） microstructure of laser solid formed （LSF） Inconel 718 changed little,and still presents the microstructural characteristic of columnar dendrites which grow epitaxially from the substrate. However,the hardness and tensile strength of DA samples increase obviously. Three technology of homogenization,solution and double aging heat-treatment （960STA） result in complete dissolution of interdendritic Laves phase and the reduction of Nb segregation. Further the solution treatment results in the precipitation of acicular δ phase along grain boundaries,and the tensile strength and plasticity both reach the wrought standard of Q/3B 548-1996 at room and high temperature. The tensile fracture surface of DA samples presents anisotropic feature of dimples along deposition orientation of columnar dendrites array,which is similar to that of the as-deposited samples. It is found that the distribution anisotropy of dimples in LSF samples disappeared through 960STA treatment.