Effect of post-treatments on the tribological and corrosion behavior of 17–4PH stainless steel processed via fused filament fabrication

Abstract

Metal fused filament fabrication (FFF) is a promising, multi-step material extrusion process, with debinding and sintering, that offers a low-cost, efficient, and safe alternative for many companies compared to other metal additive manufacturing methods. However, a quantitative analysis of the tribological properties and corrosion behavior of the metal FFF-ed parts is currently lacking in the literature.Thus, in this study, the tribological and corrosion behavior of 17–4PH stainless steel parts fabricated using the metal FFF process, with and without post-treatments via surface mechanical attrition treatment (SMAT) and magnetron sputtered gum metal (GM) coating, were investigated. Four sample configurations were assessed, including untreated (UT), SMAT-ed, UT+GM and SMAT-ed+GM. Dry wear tests and corrosion experiments in a 0.9 wt% NaCl solution were performed to understand the tribological behavior and corrosion resistance of the metal FFF-ed parts and the effect of post-treatments on their performance.The results showed that SMAT closes porosities down to ∼20–30 μm in depth compared to untreated 17–4PH sample and reduces the number of open circuit potential (OCP) cathodic drops attributed to the unstable oxide layer formation due to micro-crevices in the superficial defects. Furthermore, a relatively stable OCP was observed for GM coated specimens. This may be attributed to the filling of the superficial defects by the coating. Additionally, the superelastic GM coating reduces the superficial elastic modulus of the part from 210 GPa down to 70 GPa. The surface roughness, and the residual stresses of the final part may affect the adhesion of the GM coating.

Keywords

• Material extrusion additive manufacturing
• Post-treatments
• Tribological behavior
• Corrosion properties
• Surface mechanical attrition treatment
• Gum metal