ABSTRACT

NON-TECHNICAL DESCRIPTION: Tribocorrosion is a material degradation process caused by the combined effects of wear and corrosion. It is a research area that emerged recently, driven by increased demand for wear- and corrosion-resistant materials from biomedical implants, nuclear power generation, marine and offshore industries, etc. The complexity of tribocorrosion lies in the fact that the chemical and mechanical attacks act synergistically to cause accelerated failure. The synergetic effect is most prominent for passive metals, such as stainless steels, titanium and aluminum alloys, which rely on the presence of a thin surface oxide film (passive film) as a protective barrier against corrosion. When mechanical wear takes place during corrosion, the passive film can be locally destroyed, with the ensuing depassivation leading to rapid corrosion and early component failure. This research seeks to offer insight concerning the degradation mechanisms during tribocorrosion of passive metals using experiments and modeling. The obtained results can lead to the development of new tribocorrosion resistant alloys and coatings with enhanced durability. Research opportunities and a mentorship program are created for undergraduate students and under-represented minorities. Relevant core undergraduate courses are updated to include tribocorrosion-related topics. The outreach program features hands-on demonstrations for girls in elementary and middle schools from Pinellas County, Florida, to stimulate their interest in STEM fields. Published and promoted videos demonstrating the physical concepts related to this research are on popular social media platforms to educate a broad and diverse audience about tribocorrosion.


TECHNICAL DETAILS: Al exhibits excellent corrosion resistance but poor scratch resistance, which greatly limits its potential usage in industrial applications where mechanical contact and corrosive environment coexist. Recent studies from our group demonstrates that alloying Al with a transition metal (TM) in supersaturated solid solution has the potential of simultaneously increasing the wear resistance of Al alloys as well as the protectiveness of the passive layer, thus improving the overall tribocorrosion resistance. This research project is directed towards identifying how alloy concentration affects deformation and degradation during tribocorrosion and is centered on a comprehensive study that integrates material processing, characterization, tribocorrosion testing, and theoretical modeling. The proposed processing technique produces materials with various alloy concentrations while minimizing crystallographic texture and residual stress effects. Materials are characterized site-specifically to evaluate the microstructural modifications induced by different degradation mechanisms during tribocorrosion, including wear and corrosion and their synergistic and stochastic aspects. The specific technical objectives include (1) establishment of the alloy concentration/tribocorrosion resistance relationship for Al-TMs, (2) determination of whether an optimum alloy concentration exists for the best tribocorrosion resistance, and (3) investigation of whether (and how) in-service conditions (e.g., applied load, sliding speed) and corrosion conditions influence the tribocorrosion resistance. The obtained results help establish better guidelines for the application of metals in harsh environments and service conditions. The findings also serve to improve design principles for new tribocorrosion-resistant Al alloys, the use of which presents great potential for increasing the sustainability of global energy consumption.

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