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This paper reviews the bending fatigue endurance limits reported in the literature for carburized steels. Almost an order of magnitude difference in fatigue limits (210-1950 MPa) is reported. The reasons for this wide range are not clear because of the complexity of interactions between the microstructural, testing and manufacturing systems associated with carburized components. In well characterized specimens, two types of microstructures and fatigue crack mechanisms associated with moderate and high levels of fatigue performance have been identified and are described here. Finally, the effects of selected engineering parameters on the measurement of bending fatigue limits are discussed. The need for more complete experimental characterization of fatigue performance is stressed as a critical step to produce consistent bending fatigue performance at the upper end of that attainable in carburized steels.

This study examined the evolution of the surface topography of imperfections in response to painting. Critically-sized imperfections on industrially produced coated sheet steel surfaces were sampled, and carefully characterized. Changes in the surface topography were measured after painting simulations, and visibility after painting was assessed. Three-dimensional optical profilometry was demonstrated to be a powerful technique for assessing imperfection topographies and their evolution during painting; several imperfections that were completely invisible through human inspection after painting were still measurable by 3-D topography. Two primer surfacer systems were used, to compare a conventional liquid system with a high-build anti-chip powder system.