Wear and corrosion resistance in steel components used in aeronautic industries are allowed by superficial treatment. Coatings systems to improve mechanical properties, generally, decrease components fatigue life due to microcracks, which propagate through the substrate. Electroplating chromium has as characteristic a high tensile residual stresses originated from the electroplating process. These residual stresses increase in accordance to electroplated layer growing and relaxation occurs due to microcracks formation during electroplating process. Microcracks density is related to high tensile residual stresses, hardness and corrosion resistance. Effective methods to promote high fatigue strength in chromium coated components have been developed. In this work, is intended to evaluate the intermediate electroless nickel layer thickness outcome on chromium electroplated AISI 4340 steel. S-N curves were obtained from rotating bending fatigue tests in two hardness levels and with three thickness of intermediate electroless nickel layer. Fracture analysis was made by using the scanning electron microscopy.
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