激光选区熔化/热等静压复合成形Inconel 718组织与性能研究

热等静压(Hot isostatic pressing, HIP)技术能整体成形高性能复杂零件,但该技术存在复杂零件包套制作难、异质包套与粉末制件的界面扩散会降低性能等问题,为此展开了激光选区熔化(Selective laser melting, SLM)/HIP复合成形工艺研究。利用XRD、SEM、EBSD和拉伸试验表征了复合成形工艺基体/界面显微组织和拉伸性能。结果表明,利用SLM直接成形Inconel 718合金基体中存在明显孔洞和微观裂纹,致密度为98.3%。合金粉末经HIP成形后,基体不存在明显的孔洞和裂纹,但存在明显的原始粉末颗粒边界(Prior particle boundary, PPB)。复合工艺条件下,SLM成形的Inconel 718端基体孔洞和裂纹减少,X–Y表面熔化道特征消失,各向异性程度降低。同时,合金粉末与SLM成形Inconel 718之间不存在明显的扩散层,界面由细小晶粒组成,厚度约为16.7μm。界面的高温强度为626MPa,拉伸断口表面平直,样品沿着SLM态和HIP态结合界面处断裂。经固溶+时效热处理后,界面结合强度提高到了990MPa,断口分布在SLM成形件一侧。通过分析组织和性能变化规律,验证了利用复合成形工艺制备复杂零件的可行性。

Study on Microstructure and Properties of Inconel 718 Fabricated by Selective Laser Melting/Hot Isostatic Pressing Hybrid Forming Process

Hot isostatic pressing(HIP)technology can be used to fabricate complex parts with high-performance,however,there are some problems with this technology,such as the difficulty of manufacturing capsule for complex parts and the interface diffusion between heterogeneous capsule and powder,which will harm the performance.For this reason,a study on the selective laser melting(SLM)/HIP hybrid forming process was investigated.XRD,SEM,EBSD and tensile test were used to characterize the matrix/interface microstructure and tensile properties of the hybrid forming process.The results show that there are obvious pores and micro cracks in the matrix of Inconel 718 alloy directly formed by SLM,and the density is 98.3%.After HIP process,the Inconel 718 alloy matrix does not have obvious pores and cracks,but there is obvious prior particle boundary(PPB).Under the hybrid process conditions,the pores and cracks of the Inconel 718 formed by SLM are reduced,the characteristics of the melting track on the X–Y surface disappear,and the degree of anisotropy is reduced.After HIP,there is no obvious diffusion layer between the powder particle and the SLM-formed Inconel 718,and the interface is composed of fine grains with a thickness of about 16.7μm.The 650℃high temperature strength of the interface is 626MPa.The tensile fracture surface is flat along the SLM and HIP state bonding interface.After solid solution+aging heat treatment,the interface bonding strength is increased to 990MPa,and the fracture is distributed in the SLM forming part.By analyzing the evolution of microstructure and properties,the feasibility of using the hybrid forming process to prepare complex parts is verified.