In this study the Plasma spray coating method was used to melt the coating powder material and spray it on to the surface of the steel substrate. The coated specimens of different pure and composite materials were tested under the standard fatigue testing conditions. The best results were observed for the specimens coated with pure molybdenum followed by those coated with copper-bronze, while the worst behavior was that of the specimens coated with 100% ceramic materials. SEM test was conducted to understand the reasons behind this behavior. It was found that this behavior is due to the initiation of the crack along the boundary of the smooth area for the coated specimens, which takes time to propagate, while for the uncoated specimen the crack initiated at the boundary between the smooth regions and propagates radial inside it. The mathematical model of the behavior ï³a=K(2Nf ) b is found to suit the results of the fatigue test for all coated and uncoated specimens regardless if there is an improvement or not in the fatigue behavior.