It has been known for some years that ion bombardment of a material will bring about a redistribution of its constituents. This can take place by a direct recoil process or as a result of collisional relocation within the collision cascade, known as cascade mixing. Alternatively, there are several mechanisms of radiation enhanced diffusion which may occur if the temperature is sufficiently high. The time scales for these processes are very different. Recent developments have led to the exploration and use of these effects in order to introduce atoms from a coating layer into the substrate below by ion bombardment as an alternative to their direct implantation. This review attempts to clarify the physical processes that occur, and to describe some recent applications to contacts on silicon devices, wear resistant surfaces in titanium alloys, and to achieve corrosion resistance in iron and nickel.