Correlation between tribological measurements and surface characteristics of HVOF coated steel and PTFE materials in sliding contact

In recent years, several improvements have been made concerning the wear of materials in sliding contact, thanks to the employment of Cr+6-free hard coatings, their optimization, and the development of new deposition techniques and technologies. 

When solid lubricants, such as PTFE materials, are involved as sliding surfaces against steel material, roughness and hardness effects on friction and wear have to be taken into consideration, because they play an important role from the tribological stand point. The aim of this work is correlation of tribological measurements with surface characteristics, in particular coating material, roughness and hardness of a landing gear rod sealing system. A cylinder-on-flat specimen configuration was chosen in order to faithfully reproduce working conditions, using a coated steel cylinder sliding against PTFE samples. The PTFE material was homogeneously worn independently of the countermaterial/coating, while when sliding against the softer material, the wear of the rod was observed. A comparison between results previously obtained on NBR is provided. Keywords: friction, wear, PTFE, seals, Cr+6-free, coatings, HVOF.