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

Traditional fretting tests rely on the high Hertzian stress contacts betwee n a cylinder or sphere and a flat surface to generate oxide particles and a n eventual wear scar: However this configuration does not always match the stresses and wear mechanism associated with parallel surfaces where frettin g may only initiate in limited regions of contacting asperities. To simulat e these conditions at 175 degrees F fretting wear tests were used to evalua te the performance of High Velocity Oxy-Fuel (HVOF) and Plasma-sprayed Cu N i In coatings for the reduction of gross-slip fretting (relative displaceme nts of 100 mu m) experienced between mating beta-e titanium bosses and 4340 steel lugs. Scanning electron microscopy was then used to compare the freq uency 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.