Influence of the Nb/Ti Ratio on the Tribocorrosion Behavior of Fe–Cr–Mo–Nb–Ti Multicomponent Alloys Produced by Vacuum Melting

Abstract

Tribocorrosion is one of the main degradation mechanisms affecting metallic components exposed simultaneously to mechanical wear and electrochemical corrosion. In this work, the influence of the Nb/Ti ratio on the tribocorrosion behavior of Fe–Cr–Mo–Nb–Ti multicomponent alloys produced by vacuum arc melting was investigated. The alloys were designed through systematic variations in the relative contents of niobium and titanium to assess their effect on electrochemical stability, wear resistance, and surface degradation. Electrochemical behavior was evaluated by potentiodynamic polarization in a 3.5 wt.% NaCl solution, while tribological and tribocorrosion tests were conducted using a ball-on-disk configuration under controlled conditions. Post-test surface analysis was performed using stereomicroscopy combined with digital image processing, enabling three-dimensional topographical reconstruction of the wear tracks and extraction of quantitative parameters including groove depth, pile-up height, wear track width, and surface roughness. The results demonstrate that the Nb/Ti ratio significantly influences both electrochemical and tribological responses. The alloy with the highest Nb/Ti ratio exhibited the best overall performance, showing the lowest corrosion current density (5.37 × 10−8 A/cm2) under static conditions and the lowest wear rate (1.32 mm3/mm2·year), together with the least severe surface degradation, characterized by a groove depth of approximately 7.8 µm and minimal pile-up formation. A progressive deterioration in performance was observed as the Nb/Ti ratio decreased, with the lowest-ratio compositions presenting higher wear severity and surface instability. The AISI 316L reference material exhibited intermediate performance across all evaluated parameters. Overall, increasing the Nb/Ti ratio enhances passive film stability, reduces plastic deformation, and mitigates material removal under tribocorrosion conditions. The incorporation of three-dimensional surface analysis provides a more robust evaluation of wear mechanisms, supporting the design of multicomponent alloys with improved resistance to combined mechanical and electrochemical degradation in aggressive environments.