Tungsten coating will be applied to reduced-activation ferritic-martensitic(RAFM)steel first wall of blanket components and to copper alloys of divertor components to protect the surface against particle and heat flux.Various coating/welding technologies,such as diffusion bonding,spark plasma sintering,and vacuum plasma spraying have been examined.However the mechanical properties in the vicinity of the bonding interface as well as of the base metals may deteriorate due to the thermal stress induced by the difference in the coefficients of thermal expansion of tungsten and the substrate materials at high temperatures during processing or operation.Hokamoto has developed underwater explosive welding(UWEW)which enable to obtain dissimilar joining of various materials at room temperature.Our previous study successfully obtained a coating of 0.2 mm thickness W foil on the F82H RAFM steel using UWEW.Although the results imply that the interface has a good bonding strength,further verification is needed especially for the thermal properties.The present study investigates the thermal conductivity and microstructure of the tungsten-coated F82H steel and copper fabricated by the UWEW.