| Résumé | Synergy between wear and corrosion has been widely observed in many tribo-corrosion systems. To help material selections in industrial applications, lab testing are often conducted. Since no lab testing can duplicate all conditions in a particular application, it is important to understand the effect of test parameters on the synergy of a given tribo-system so that lab results can be appropriately correlated/applied to the target application. In this study, an abrasion-corrosion test system based on a modified Miller tester has been used to investigate the effect of sliding speed and test duration on the abrasion-corrosion synergism of a D2 tool steel in a salt slurry. The study is relevant for many industrial applications such as autosamplers (sleeves) for slurry sampling, plunger or positive displacement slurry pumps, and dredging machinery.
The results showed that total corrosion rate increases rapidly with sliding speed and reaches some almost constant value above a sliding speed of 16 rpm (revolutions per minute). The contribution of pure corrosion to total abrasion-corrosion loss is negligible (<<1%) under all the test conditions. The total material loss rate and synergy are considerably higher at the lower sliding speed: At a sliding distance of 7023 m, the abrasion-corrosion loss rate and synergy at 16 rpm were 20% and 68% higher, respectively, than at 48 rpm. Synergy and relative contribution of corrosion to the total material loss also increase with sliding distance; however, this variation is more apparent at the lower sliding speed than at the higher sliding speed. At 16 rpm, the synergy and its relative contribution to total abrasion-corrosion loss rate increased by 68% and 95%, respectively, between sliding distances of 2341 m and 7023 m. However, these increases were only 13% and 49% respectively for sliding at 48 rpm. The percentage contribution of abrasion-enhanced corrosion (ΔKc) to synergy (Ks) decreases with sliding distance and this variation is more significant at the lower sliding speed, with ΔKc/Ks decreasing from 93% at sliding distance of 2341 m to 56% at 7023 m for sliding at 16 rpm as opposed to decreasing from 37% to 33% at 48 rpm sliding.
A conceptual model has been proposed to explain the results based on the relative severity of the two competing processes that cause the total material loss during abrasion-corrosion, i.e., the electrochemical process (corrosion) and the mechanical process (abrasion). |
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