Fatigue behaviour of notched galvanized Strenx700E high-strength steel specimens

Abstract

High-strength steels (HSS), such as STRENX700E, are increasingly used in weight-sensitive structural applications due to their high specific strength. Typical uses include bridges, road infrastructure, offshore platforms and earth-moving machinery. Their superior mechanical properties result from thermomechanical processing, which involves hot rolling followed by quenching and tempering, improving strength while reducing residual stresses. However, like most steels, HSS are very sensitive to aggressive environments, particularly in proximity to salt water, coastal areas or marine environments. To preserve their mechanical integrity in such conditions, surface treatments such as galvanising are commonly applied to improve corrosion resistance. Despite its protective advantages, the influence of galvanising on the fatigue behaviour of HSS remains a critical issue, especially in components subjected to cyclic loads or with notches. To study the actual service conditions, constant amplitude fatigue tests were performed on specimens notched with a clean circular notch to evaluate the combined effects of geometry and galvanising. Given the high silicon content typical of STRENX700E, particular attention was paid to the interaction between the zinc coating and the steel substrate, especially regarding microcrack propagation and potential embrittlement due to the galvanising process. Surface finish was also considered, as surface deterioration can act as a crack initiation point and significantly reduce fatigue strength. These results provide valuable information for the design and maintenance of HSS structures exposed to cyclic loads in corrosive environments, supporting the development of more durable engineering solutions.