Materialtester i ammoniak - för motorapplikation

Sammanfattning

Combustion engines today are primarily powered by fossil fuels, resulting in emissions of pollutants that pose significant environmental challenges. Therefore, transitioning to alternative fuels that reduce these emissions is crucial. One promising alternative fuel is ammonia, which, in addition to being carbon-free, benefits from an already developed infrastructure. However, switching to new fuels creates a different chemical environment inside the engine, and the impact on engine materials has not been well studied. Thus, in this master’s thesis, nine different engine materials (copper, brass, aluminum, cast iron, ball bearing steel, stainless steel, titanium, titanium nitride, and diamond-like carbon (DLC)) were studied before and after ammonia exposure, as well as after a tribological test, to increase the knowledge in this field. The materials were analyzed using SEM and EDS before and after exposure, and additional techniques, LOM and XPS, were also used after the exposure. All materials showed some degree of reaction in the ammonia solution. Copper, brass, and aluminum were altered to a depth of many micrometers, and the surface layer broke under tribological contact. Cast iron also reacted, but to a lesser extent, as parts of its surface remained unchanged. Ball bearing steel, stainless steel and titanium reacted mildly, primarily superficial oxidation of the surfaces. Titanium nitride and DLC were almost unaffected by ammonia. This suggests that titanium nitride, DLC, ball bearing steel, stainless steel, and titanium are more suitable for use in an ammonia driven combustion engine than copper, brass, aluminum, and cast iron.