Revealing the fretting corrosion degradation mechanisms of friction stir processed cold spray additively manufactured stainless steel

In an effort to improve the fretting corrosion resistance of cold spray (CS) additively manufactured 316L stainless steel (SS), friction stir processing (FSP) was applied as a post-processing surface modification technique. The change in wear-corrosion synergy and degradation was evaluated by assessing changes in mechanical, chemical, and elemental responses. It was found that the improvement in hardness and reduction in porosity induced by FSP improved the stiffness of the surface, resulting in a nearly full-stick fretting regime. Due to the influence of fretting corrosion, high amounts of Ni were present within the fretting wear track, decreasing the surface’s propensity for accelerated corrosion. The fretting wear mechanism for the CS FSP specimen was abrasion-dominant, whereas the CS specimen mainly consisted of surface fracturing and some abrasion. Other material factors such as surface strengthening, microstructural refinement, and changes in the atomic phase enabled by FSP also contributed to the improvement in fretting corrosion resistance. Collectively, this work shows that FSP post-treatment is a viable technique to improve the fretting corrosion degradation resistance of additively manufactured CS 316L SS components.