Comparison of microstructure features and mechanical properties for additive manufactured and wrought nickel alloys 625

The microstructure characteristics as well as the mechanical properties of an Inconel 625 alloy obtained by three processes: forging, SLM and LMD, are investigated. For the last two processes, known as "additive manufacturing", the influence of printing parameters is considered as well as the role of possible heat treatments. First, microstructural analyses (SEM and EBSD) underline the presence of columnar dendrites with a very heterogeneous grain size for additive manufactured as-built materials. The microstructures appear highly textured, particularly for SLM ones which are also often finer than the ones obtained by LMD. Heat treatments and particularly a 1h-1100 degrees C annealing is proven to improve the printed parts microstructure and to avoid a drastic decrease in terms of ductility, particularly for LMD parts. The LMD process with controlled laser power, coupled with appropriate heat treatment, finally produces materials with both microstructures and tensile mechanical properties close to or better than those of the wrought alloy.