Effect of Nickel-Niobium Coating on Fatigue Resistance of SAE 1020 Carbon Steel

Abstract

-Effect of nickel-niobium coating by electrodeposition on the fatigue resistance of SAE 1020 carbon steel is studied in this work. The nickel-niobium coating was performed using a nickel Watts bath with added niobium powder. The specimens for fatigue tests were taken from SAE 1020 steel bar with 7.94mm (5/16 '') diameter. The fatigue tests were carried out by rotary bending load control with loading balance. It employed a rotation speed of approximately 1500rpm (25Hz). Vickers microhardness tests were performed on steel and deposited layer of nickel-niobium. Analysis of the electroplated layer connection interface in the steel and fatigue fractures were performed by scanning electron microscopy (SEM). The fatigue tests were performed in order to obtain S-N curves (Wöhler curves). It was observed that nickel-niobium coating gave only a tendency to increase the fatigue strength of the steel, although the coating layer has shown high hardness compared to the steel. The detachment of the deposited nickelniobium layer was regarded as the main cause of noncontribution of the increase in fatigue limit coated steel compared to the same in its original condition.