Reduction in Fatigue Life in Cr-Coated Steel Induced by Pulsed Laser Heating

Four-point bend tests were performed on Cr-coated steel specimens that were pulsed laser heated (PLH) with two pulses per area from a millisecond pulse duration laser. Cracks were observed in the PLH specimens extending to the substrate. Specimens subjected to PLH exhibited reduced cycles to failure under all the loadings. This indicates that the PLH process replaces the crack initiation process, and the PLH-formed cracks give the expected crack propagation behavior. This approach provides a method to separately study the effects of crack formation and crack propagation in fatigue life tests. It is especially applicable to situations in which the cracks to be propagated are induced by thermomechanical processes.