Effects of Normal Load, Sliding Speed, and Surface Roughness on Tribological Properties of Niobium under Dry and Wet Conditions

Abstract

The effects of normal load, sliding speed, and surface roughness on the friction and wear of high-purity niobium (Nb) during sliding without and with an introduction of water were systematically investigated. Increasing the normal load or sliding speed decreased the friction of the Nb under the both dry and wet conditions because the increased wear of the Nb decreased the interfacial shear strength between the steel ball and Nb by promoting the surface roughening and the production of wear debris. However, the Nb tested at the lowest sliding speed under the lowest normal load with water exhibited the lowest friction and wear due to the formation of oxide layer on the wear track. The friction and wear of the Nb tested under the dry condition decreased with increased surface roughness because the higher interfacial shear strength between the steel ball and smoother Nb resulted in the earlier breakdown of the native oxide layer and direct contact between the steel ball and Nb. However, increasing the surface roughness of the Nb increased its friction and wear under wet conditions, probably due to the easier breakdown of the oxide layer that formed on the rougher surface during sliding. The tribological results clearly showed that the introduction of water during sliding had a significant influence on the tribological properties of the Nb.

Higher in-flight particle velocities enhance in vitro tribological behavior of plasma sprayed hydroxyapatite coatings

“…The steel ball rubbed on the HA4 coating had a significantly larger wear width of 658 ± 86 µm than the one of the HA1 coating (wear width of 236 ± 54 µm). Such result further supported the idea that the HA4 coating deposited at the higher in-flight particle velocity possessed a higher wear resistance, giving rise to the higher wear of its counter steel ball during the prolonged sliding [26].…”

“…The HA coatings deposited at the higher in-flight particle velocities exhibited lower friction during the entire sliding without and with Hanks' solution as a result of a lower wear of the coatings. Under the wet conditions, the HA coatings generally showed lower friction coefficients with respect to laps due to the lubricating effect of the solution [26].…”

“…In addition, all the HA coatings tested with Hanks' solution exhibited lower friction coefficients as opposed to their counterparts tested under dry conditions. The reason is that the Hanks' solution lubricated the rubbing surfaces and prevented a direct solid-solid contact between them during the sliding [26][27][28]. Fig.…”

Considerations on the Influence of the Tool/Sheet Contact Conditions for Incremental Forming of Niobium Sheets

“…The above justifies the recent increasing research interest in the understanding of Nb properties and the deformation mechanisms [21][22][23][24]. Moreover, other studies investigated the surface damages of Nb sheets during forming processes, like grinding marks, inclusions, galling phenomenon, orange peeling, tearing, scratches and wrinkling [25,26]. Precisely in order to better understand the friction behavior of Nb sheets during forming processes, the authors presented the results of an experimental campaign based on wear tests, carried out under different loads and in both dry and lubricated conditions [27].…”

Experimental and numerical investigation on shot peening of low alloy steel

“…Therefore, the highest friction coefficients in cases of Re-SSP come from the effect of this ultrafine grain layer.Figure 4-4b shows the friction coefficients of the shot peened steels against the steel ball under the load of 5N as a function of the number of laps. The friction coefficient increases gradually in the first 10,000 laps (also called running-in period) due to the increased wear of asperities rubbing surfaces[76,[84][85][86][87].From 10,000 laps onwards, the tested samples exhibit a steady friction coefficient during the entire sliding test[76,[84][85][86][87].…”