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In this work CM247LC, a low weldable Ni-Based alloy, was produced using selective laser melting (SLM). Despite the initial process parameter optimization, the low defect volume fraction was still uncompliant with manufacturing standards. This condition is principally caused by the high γ’ volume fraction which strongly affects the alloy weldability. Nonetheless, a crack free condition was eventually achieved applying a γ’-sub-solvus Hot Isostatic Pressing Cycle (HIP) which lowered the defects fraction down to 0.04%. The HIP cycle also demonstrated to play an important role in the stabilization of the microstructure, considerably limiting the carbides coarsening during the following heat treatment. Apart from the effectiveness of the healing process brought by HIP, the material microstructure still needs an optimization process which will be described along this paper. In fact, the Initial microstructure obtained after the printing process (the as-built condition) as well as the one obtained after HIP (post-HIP) won’t meet the desired requirements. Namely, the dendritic and γ’ free microstructure of the as-built material or the one with coarse and disordered particles obtained right after HIP, still need a tailored homogenization process. This paper will show how the combined effect of the solution and first aging treatment will profoundly alter the γ’ precipitation. More specifically, here, a new heat treatment recipe was developed to promote the precipitation of ordered cuboidal primary γ’ so as to improve creep and high temperature fatigue resistance. Moreover, the use of a γ’ super-solvus temperature allowed to achieve a γ’ volume fraction as high as 73% reducing its average size to 520 nm. At the same time, such heat treatment caused a profound alteration of the crystalline structures of the material promoting a general grain coarsening and the formation of equiaxial grains.

Intermetallic γ‐TiAl based alloys offer outstanding creep properties, high specific strength and sufficient oxidation resistance at application temperature in the range from 600 to 800 °C. These properties make them prosperous candidatesto substitute heavy Ni‐based alloys offering weightsavings up to 50%. Drawbacksinclude their inherent brittleness as well as reactive melts, which complicate processing and drive costs. In this regard, electron beam melting (EBM), a powder bed additive manufacturing technology, offers low impurity pickup due to the vacuum environment and elevated processing temperature, enabling the manufacturing of TiAl components with increased geometrical complexity. Still, microstructures of electron beam melted titanium aluminides often show a banded character and suffer from Al loss due to process related evaporation decreasing room temperature ductility. As the formation mechanism of banded microstructures in electron beam melted Ti‐48Al‐2Cr‐2Nb (in at. % unless stated otherwise) is not yet fully understood, a scientific explanation is presented in this work.

More and more efforts are spent for manufacturing low-weldable nickel-based superalloys in contemporary research applied to additive manufacturing. One of the biggest difficulty with these kinds of alloys is reducing the flaws density obtaining a good final microstructure in the as-built state. Nevertheless, the complete densification of the alloys can be reached only after further heat treatments such as the Hot Isostatic Pressing (HIP). The SLM material microstructure is severely different with respect to that obtainable after traditional manufacturing. This will also impact the final mechanical properties as well as the microstructure stability. Very often, designing specifically tailored heat treatments become the most viable solution for enhancing these materials. In this work the effect of the HIP treatment Is discussed and, after performing DSC and TMA thermal analysis, the effects of two heat treatments on two Ni-based alloys are discussed

In powder bed additive manufacturing technique, the powder characteristics can determine the success or the failure of the job. In the Electron Beam Melting (EBM) process is generally used spherical powder with a particular size distribution of 40-150��m. During the EBM process the powder is spread onto the platform by the rake, therefore is essential to use powders with optimal rheometric properties and powder quality is a key aspect that strongly affects the processability. In this work, different ��-TiAl powders coming from different suppliers as well as different lots of the same suppliers were characterized in terms of flowability by Hall flow, apparent density, tap density, grain size distribution by granulometer, morphology properties of the particles as well as characterization of the internal defects to correlate the result with processability in the EBM A2X machine.