The future demands of diesel engines require new options for low-friction and wear-resistant materials in order to increase efficiency and achieve environmentally sound solutions. Efforts are made to improve the performance and reduce the weight of engine blocks by coating the Aluminium cylinder bores with thermal-spray processes. Thus beside other means today nanocrystalline coatings are currently discussed, which should allow for the desired combination of structural, productional, and topographical properties. Beside sufficient tribological properties it is important that the composite (base material and coating) allows for an elongated endurance under cyclic mechanical and thermal stresses. In this work a four-point-bending test was used to examine deleterious failure mechanisms during fatigue such as spalling of the coating or delamination from the substrate. Therefore various thermally sprayed coatings were bent in tension and compression. The results were analysed in relation to the coating microstructure.