Microstructure Evolution in Inconel 718 Produced by Powder Bed Fusion Additive Manufacturing

Journal of Manufacturing and Materials Processing

Grzegorz Cios¹  Tomasz Tokarski¹  Gert Nolze²  Stefan Reinsch²  Judy Schneider³  Laura Farris³  Sean Thompson⁴ 

[1] Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, aleja Mickiewicza 30 Krakow, 30-059 Malopolskie, Poland;BAM Federal Institute for Materials and Research and Testing, 12205 Berlin, Germany;Department of Mechanical Engineering, University of Alabama in Huntsville, Huntsville, AL 35805, USA;Materials Science and Engineering Division, Propulsion and Structures Technology, Development Directorate FCDD-AMT-MPS, Huntsville, AL 35808, USA;

关键词: metal additive manufacturing;    Inconel 718;    heat treatment;    grain boundary precipitates;    Laves phase;    mechanical properties;   

DOI  :  10.3390/jmmp6010020

来源: DOAJ

【 摘 要 】

Inconel 718 is a precipitation strengthened, nickel-based super alloy of interest for the Additive Manufacturing (AM) of low volume, complex parts to reduce production time and cost compared to conventional subtractive processes. The AM process involves repeated rapid melting, solidification and reheating, which exposes the material to non-equilibrium conditions that affect elemental segregation and the subsequent formation of solidification phases, either beneficial or detrimental. These variations are difficult to characterize due to the small length scale within the micron sized melt pool. To understand how the non-equilibrium conditions affect the initial solidification phases and their critical temperatures, a multi-length scale, multi modal approach has been taken to evaluate various methods for identifying the initial phases formed in the as-built Inconel 718 produced by laser-powder bed fusion (L-PBF) additive manufacturing (AM). Using a range of characterization tools from the bulk differential thermal analysis (DTA) and x-ray diffraction (XRD) to spatially resolved images using a variety of electron microscopy tools, a better understanding is obtained of how these minor phases can be properly identified regarding the amount and size, morphology and distribution. Using the most promising characterization techniques for investigation of the as-built specimens, those techniques were used to evaluate the specimens after various heat treatments. During the sequence of heat treatments, the initial as-built dendritic structures recrystallized into well-defined grains whose size was dependent on the temperature. Although the resulting strength was similar in all heat treated specimens, the elongation increased as the grain size was refined due to differences in the precipitated phase distribution and morphology.

【 授权许可】

Unknown