Abstract: The shell structure consisting of copper alloy surfacing layer and steel substrate was produced by a cool-body tungsten inert gas surfacing method, and microstructure of the shell was mainly investigated.Characteristics of microstructure and morphology of interface, copper alloy layer and steel substrate were observed by using optical microscope, scanning electron microscope.Effects of welding process on the content of Fe within the copper alloy were also analyzed.Energy dispersive X-ray analysis on the composition change of coppr alloy layer and interface shows that solution of some elements from the steel substrate to the copper alloy layer and diffusion of some elements of copper alloy layer to the steel substrate happened during the welding process.There is Fe₂Si distributing in the copper alloy layer dispersely when CuSi3 is used as surfacing layer and there is dendritic crystal in the copper alloy layer when surfacing layer is made of B30.Moreover, penetration cracks caused by eutectoid at the interface occurred when the inappropriate welding parameters were used.