Nanoscale deposition of Group IVB elements on anodized surfaces to reduce friction

Abstract Reduction of dry friction losses is among top technical priorities. Recently, nanoscale deposition of Ti layers on anodic alumina demonstrated unusually low dry friction, but no clear comparison to other elements had been provided. In this study, magnetron sputtering and Atomic Layer Deposition (ALD) were used to form nanometric layers of Cu, Cr, Hf, Nb, Ti, Zr and their oxides on several types of anodic alumina. Elements of IVB group were more effective than layers of Cu, Cr or Hf, which are widely used in anti-wear coatings. Only layers of 15–75 nm thickness remained effective, while 180 nm or thicker layers did not reduce friction significantly. Properties of materials within nanometric layers appeared to contribute to friction reduction much more compared to insignificant effects of hardness, roughness or substrate interactions. Also, inert substrates might represent a favorable matrix for studying the fundamentals of dry friction on deposited nanoscale structures.