Shot Peening as an Alternative to Fatigue Life Improvemen

The effect of an electroless Ni-Cu-P coating on the fatigue behavior of quenched and tempered CK45 steel has been investigated. The fatigue tests under rotating bending conditions have been conducted in three different conditions of uncoated, as-deposited and shot peened prior to the coating deposition. The results indicate that plating of the base steel leads to a fatigue life reduction. The decrease in the fatigue strength was observed to be less marked for the shot peened specimens. The microscopic observations indicate that in the as-deposited condition, the reduction in fatigue life is associated with the nucleation of fatigue cracks on the lateral side of coating. On the contrary, when the samples were shot peened prior to the coating deposition, the crack initiation sites were displaced to the coating-substrate interface which led to an improvement of fatigue behaviour.