The present investigation has been conducted to study the fatigue behavior of a SAE 1045 steel both uncoated and coated with a Colmonoy 88 alloy (NiCrBSiW) of approximately 410 μm thick, deposited by HVOF thermal spraying. Previously to deposition the samples were grit-blasted with alumina particles of approximately 1 mm in equivalent diameter. Tensile and fatigue tests were carried out with the uncoated and coated specimens. Fatigue tests were conducted under rotating bending conditions (R = − 1) at a frequency of 50 Hz. The samples tested were in three different surface conditions, including polished, grit-blasted and coated. The fatigue limit was determined by means of the staircase method employing a stress step of 5 MPa. The results indicate that the presence of the coating gives rise to a reduction in the fatigue life of the coated samples tested in air in comparison with the uncoated specimens. On the contrary, when the coated samples were tested in a NaCl solution at alternating stresses less than 350 MPa, these showed an increase in fatigue life in comparison with the polished uncoated samples. The analysis of the fracture surfaces of the specimens tested in air revealed that alumina particles present on the surface of the grit-blasted samples acted as stress concentrators, inducing the nucleation of fatigue cracks at the substrate–coating interface, which explains the reduction in fatigue life. However, under corrosive conditions and low alternating stresses, the presence of the coating provides an effective protection against corrosion-fatigue failures, giving rise to an improvement of the corrosion-fatigue performance of the coated system. On the contrary, at elevated alternating stresses, the coating was observed to delaminate from the substrate, leading to an impairment of the corrosion-fatigue behavior of the coated samples.
