Mechanisms of Nickel-Based Coatings for Fretting Wear Mitigation of Ti6Al4V Interfaces

Fretting wear is an accumulation of damage that occurs at component interfaces that are subjected to high contact stresses coupled with low amplitude oscillation. The key to fretting wear reduction in metallic contacts is the mitigation of galling at the interface, followed by the control of debris production and the rheology of active wear debris. Once the thin surface species of the metallic interfaces is dispersed, adhesion between the contacting nascent surfaces causes the inception of severe surface deformation and material transfer or removal. This is extremely apparent in the fretting wear of aerospace materials such as titanium alloy and nickel alloy contacts. However, the literature suggests that nickel alloy contacts perform very well in sliding and reciprocating wear contacts at elevated temperatures due to the formation of what is often called a Glaze oxide layer. The current state of literature describes the composition of the glaze layer as NiO. The focus of this dissertation was to provide experimentation and analysis of temperature effects on the lubricious tribofilm formation that occurs in nickel contacts. This was accomplished by testing commercially pure nickel coatings and thick nickel oxide surfaces. The enhanced understanding of the fretting performance of nickel oxides aided in the development of nickel graphite based self-lubricating coatings. These coatings were then proved to reduce fretting wear damage within Ti6Al4V mated surfaces over a wide temperature range