Surface effects on the growth, adhesion and properties of reactively deposited hard coatings

Atomistic deposition processes such as physical vapor deposition (PVD) and chemical vapor deposition provide a means of providing hard coatings with a high fracture resistance. The growth, properties and functionality of PVD hard coatings depend strongly on the physical, mechanical and chemical properties of the substrate surface. Initially the substrate surface strongly influences the adatom nucleation mode, nucleation density and interface formation. Surface roughness causes the film to grow in a less than fully dense manner due to geometrical effects. The surface chemistry affects nucleation, diffusion and reaction at the substrate surface. In service, the substrate will often have to aid in supporting the applied loads, aid in corrosion protection and resist mechanical or thermal fatigue. Techniques for determining surface roughness and modifying the morphological, mechanical and chemical properties of substrate surfaces to aid in the functionality of hard coatings are discussed.