Effect of Inherently Porous Structure Produced by Metal Fused Filament Fabrication on the Tribological Behavior of Lubricated Steel-Steel Contact

By introducing local depressions, as small reservoirs for lubricants and wear debris, on a flat surface, the surface texture has been proven to positively affect the friction and wear behavior of lubricated sliding surfaces. However, the effectiveness of the surface texture diminishes and disappears eventually as wear develops at the contact interface. In order to achieve a longer-lasting beneficial effect on the sliding surface, this work develops an approach to print an inherently porous structure up to a certain depth beneath the contact surface to retain the benefits associated with surface texture. A test structure was created from 17-4 PH stainless steel using a metal fused filament fabrication system. The performance of the printed porous structure was evaluated using a steel ball in a ball-on-flat reciprocating tribometer under lubricated conditions with mineral oil. By comparing with the solid sample, it was found that the printed structure with inherent porosity improved the tribological performance by reducing the friction up to 20% and the wear rate up to 90%. The experimental results also indicate that the effectiveness of the printed texture is strongly correlated to the shape and the distribution of the pores on the wear track, which requires further research in the following studies.