Electro discharge machining (EDM) is an important manufacturing process for hard-to-cut materials like nickel-based alloys, e.g., alloy718. Its high yield strength at high temperature make it a suitable material for vessels for high-pressure/high-temperature applications, in particular for ammonothermal pressure vessels. This report first summarizes the relationship between microstructure and properties of alloy718 for practitioners. Second, it focuses on the metallographic description of alloy718 surfaces proceeded by EDM and its behavior during use as equipment for ammonoacidic systems. Furthermore, the finding of suitable post-processing, namely honing, to achieve high stability of the surface at high-pressure atmosphere is included.