Effects of Ti-6Al-4 V Surface Condition on the Performance of DFL Lifetimes

In this study, the impact of different substrate surface conditions on the performance of an epoxy-bonded dry film lubricant (DFL) and their fretting lifetimes are evaluated. Ti-6Al-4 V fretting samples with various surface preparation methods; ground (as received), grit blasted (at a range of severity levels) and shot peened samples were coated with a MoS₂ loaded epoxy based DFL and implemented in fretting tests against like on like cylindrical specimen with a radii of 15 mm which were also coated. Distinct damage behaviours and coating lifetimes are observed for each of the surface preparation methods tested. Results indicate the various damage mechanisms are associated with initial substrate surface conditions which influence the stability and longevity of the system. Having established a correlation between DFL lifetime and substrate surface conditions, the next step in this work is to identify the specific surface features which promote the longevity of DFL. It must be noted that the substrate surface considered in the study is the DFL/substrate interface, i.e. the surface of the specimen prior to DFL coating, as opposed to the outer surface of the coated specimen.