Effects of Electrolyte and Ti Layers on Static and Dynamic Friction of Anodized Alumina

Abstract

Static friction is important for many non-lubricated surfaces, especially when friction is intermittent. Coefficients of Friction (COF) were evaluated on industrial aluminum alloys 1050 and 6082, which were freshly anodized in sulfuric/oxalic or phosphoric acid electrolytes to 60 μm coating thickness. Hard anodizing significantly reduced COF. Under 10 N load friction trends were nearly identical despite sliding velocity variation from 0.02 to 0.5 cm/s, while 1 N load led to higher static COF. Magnetron sputtering was used to deposit Ti layers. Static COF went down from over 0.4 to ~0.2 in 16 nm and 75 nm thick layers, while that of 2.3 µm had no positive effect. Dynamic COF was also similarly reduced, suggesting possible industrial applications.

Antifrictional Effects of Group IVB Elements Deposited as Nanolayers on Anodic Coatings

“…Al alloys 1050 of 99.67% purity (0.25% Fe; 0.08% Si) and 6082 of 96.72% (1.10% Si; 1.02% Mg; 0.61% Mn; 0.54% Fe), with a sheet thickness of 2 mm, from FXB-Niemet UAB (Lithuania), were used as substrates for anodization and deposition of group IVB and other metals as nanolayers on anodic coatings. Most of the equipment and procedures, including hard anodizing, microscopy and tribotesting had already been presented previously [9,17,18]. Briefly, their descriptions are provided below.…”

“…The duration of the tribotest was either automatically limited, due to excessive frictional force because of an increase in COF, or stopped after a specified number of friction cycles. Static COF, representing the highest friction force of the first friction cycle required to start sliding motion, was measured as described previously [17].…”

“…In this study, nanolayers of group IVB (Ti, Zr, Hf) elements and several additional metals, including Cr, Cu and Nb, were deposited on anodic coatings of industrially relevant Al alloys 1050 and 6082 in order to combat dry friction losses. While a significant portion of the data was retrieved from previous publications [17,18], new microscopy images, roughness measurements and conceptual interpretations are also provided. A preliminary assessment of the thin Sn layers is also presented.…”