The influence of U-Nb substrate roughness on the service performance of Ti/TiN multilayer coatings

Surface roughness is a vital issue when evaluating the coating performance. In this work, Ti/TiN multilayer coatings were deposited on UNb substrates with varied roughness of Ra 0.8/1.6/3.2/6.3 μm, and then the effect of substrate roughness on the service performance of Ti/TiN multilayer coating was studied. The interface structure, adhesion and corrosion behavior have been investigated by scanning electron microscopy (SEM), scratch tests and electrochemical measurements, respectively. The results showed that coating adhesion increased with a decrease of substrate roughness, along with the improvement of its corrosion rate. Both adhesion and corrosion properties degraded dramatically as Ra exceeding 3.2 μm, which may be explained by the residual stress and interfacial defects. And the coating failure occurred by spallation and cracking, typically along the peaks of the coating profile. This study offered guidance to optimize the substrate roughness for the deposition of hard protective coatings, especially for nuclear industries.