Elevated temperature fretting evaluations using a flat-on-flat configuration

Traditional fretting tests rely on the high Hertzian stress contacts between a cylinder or sphere and a flat surface to generate oxide particles and an eventual wear scar. However, this configuration does not always match the stresses and wear mechanism associated with parallel surfaces where fretting may only initiate in limited regions of contacting asperities. To simulate these conditions at 175°F, fretting wear tests were used to evaluate the performance of High Velocity Oxy-Fuel (HVOF) and Plasma-sprayed Cu Ni In coatings for the reduction of gross-slip fretting (relative displacements of 100 μm) experienced between mating beta-c titanium bosses and 4340 steel lugs. Scanning electron microscopy was then used to compare the frequency and severity of fretting wear on the titanium blocks. Results of the analysis indicated the viability of the lubricious coatings for eliminating the instances of fretting. Furthermore, the tests indicated the usefulness of the flat-on-flat testing configuration for illuminating the potentially random occurrences of fretting damage between parallel surfaces.