The Effect of Nickel Plating on Fatigue Strength of Steel

Abstract

It is well known that the fatigue strength of machine parts is generally reduced by electroplating. This paper describes the summary of the data of fatigue strength for nickel plated steels obtained recently. The main results are as follows:(1) When carbon steel is nickel plated, the fatigue strength decreases as the current density or the thickness of plating increases.(2) The baking treatment at 200∼550°C after plating causes the reduction in the hardness of plating, but does not affect the fatigue strength.(3) The corrosion fatigue strength in 3% NaCl solution is slightly smaller than in air. Nickel plating gives only a little protective effect under the repeated stress condition, but prolongs the fatigue life of plated steel as compared with that of bare steel.(4) The fatigue strength of notched steel is also reduced by nickel plating, and the degree of loss can be estimated from the product of the individual reduction effects caused by plating and by notch.(5) The loss of fatigue strength of plated steel can be decreased by diffusion treatment at 700∼850°C.(6) Shotpeening, either before or after nickel plating, increases the fatigue strength considerably.These results suggest that the main cause for fatigue strength loss by nickel plating is not the internal stress nor absorbed hydrogen in the plated layer, but the low fatigue strength of the plated layer itself. The fatigue crack tends to form easily in plated layer, and acts as the source of stress concentration for crack propagation into steel similar to the double notch effect.