The influence of hydrogenated amorphous carbon coatings (a-C:H) on the fatigue life of coated steel specimens

The influence of a hydrogenated amorphous carbon coating on the fatigue life of an austenitic steel was evaluated in this work. The fatigue damage mechanisms have been compared for both coated and uncoated specimens. A strong increase in fatigue life of more than 300% for low total strain amplitudes was found for the coated specimens. The influence of the coating on the fatigue life increases with decreasing total strain amplitude. The damage mechanisms were analyzed using atomic force microscopy and focus ion beam cross sectioning. The coated specimens show a significantly reduced surface roughening. Slip bands in the steel sample could not penetrate the coating and thus slip step formation on the surface was avoided, leading to the enhanced fatigue life. The compressive residual stress in the coating is discussed being the main reason for the enhanced fatigue life of the specimens.