The influence of diffusion coatings on the fatigue strength of copper

Abstract

It has been found possible to increase the fatigue strength of copper by selectively alloying a thin layer at the surface. The three alloy systems copper-nickel, copper-silver and copper-zinc were investigated, and the fatigue strength was shown to be independent of the degree of solute penetration and of its mode of distribution, when tested at room temperature in the normal laboratory environment. The greatest increase in fatigue strength was obtained with the copper-zinc surface alloy, for which an increase of 15% was recorded.The increased fatigue strength is thought to be dependent both on the new value of τIII, the threshold stress for stage III hardening in single crystals, and on the relatively greater thermal diffusivity of the foreign atoms introduced; the improvement in fatigue resistance was limited to alloy systems in which the solutes possessed a higher diffusion rate than the copper.