Nickel-based superalloys, and more specifically Alloy 718, is widely used in the manufacture of hot-section components of gas turbines, thanks to their high mechanical performance at high temperatures. Nowadays, they are efforts to produce these parts using additive manufacturing (Laser Powder Bed Fusion), as it enables the production of complex geometry with excellent properties and reduces waste. However, despite these advantages, the parts produced generally have microstructural defects near the surface, which can affect mechanical properties. Nevertheless, these can be reduced or even eliminated by optimizing certain production parameters and using various post-treatment processes.

The primary scope of this work was to study the influence of the LPBF process laser orientation, as well as the impact of post-treatment processes (nickel plating, Hot Isostatic Pressing, Heat Treatment) on the surface properties of Alloy 718 builds, with the ambition of determining the combination of treatments that gives the best results. In fact, to date, very little research has been conducted on the nickel plating of alloy 718 parts produced by LPBF.

In this study, samples were manufactured using LPBF and then treated using nickel plat-ing, hot isostatic pressing, and heat treatment. These combinations were characterized using standard techniques, including microstructural analysis, elemental analysis, and evaluation of surface properties (surface roughness, valley depth, and peak height), as well as 4-point bending.

The outcomes of this study revealed the importance of laser orientation on sample surface properties, including roughness and the depth of valleys. But also, the importance of post-treatments to improve nickel plating, notably through the diffusion of alloying elements. Finally, the lifetime of the samples was assessed using 4-point bending tests. It is clear that the addition of nickel plating, combined with similar heat treatments, improves the mechan-ical strength of the samples, notably by reducing the depth of surface valleys.