Effects of temperature on friction and degradation of dry film lubricants during sliding against aluminum alloy sheets

Influence of elevated surface temperature on the formability in cold forming of aluminum alloy sheets

“…As the reduction of Dmax was just about 21 % for EN AW-6016-T4 compared to about 28 % for EN AW-5182, the hotmelt deposited on the EN AW-6016-T4 sheet was thermally more stable than the hotmelt deposited on the EN AW-5182 sheet. This basically agrees with the results of a previous study on the temperature-induced degradation behaviour of hotmelts [19]. The degradation of the lubricant increases both the COF and the adhesive wear and, thus, it decreases the formability even in deep drawing at RT.…”

“…Beyond 60 °C the increase of the COF was only moderate. This unfavorable behavior is mainly attributed to the partial degradation of the hotmelt lubricants at elevated temperatures and contact pressures [19]. This illustrates that the build-up of a sufficient layer of lubricant on the tool surfaces was generally crucial, as it directly affected the formability of both alloys investigated.…”

“…Three tests were performed at each contact condition, and the mean COF was calculated based on the results of these three tests. Details about the methodologies of friction testing and lubricant analysis are provided in [19].…”

“…Even in deep drawing at room temperature (RT) heat generated by friction and by plastic deformation may notably increase the local surface temperature of the tool. The temperature-induced degradation of the lubricant was identified to increase the frictional forces at the contact surface between the sheet and the tool [16][17][18][19]. This effect on the tribological system may cause deviations and defects, especially in the serial production of deep-drawn aluminum alloy components.…”

Development of a Laboratory-Scale Test Methodology for Performance Evaluation of Lubricants for Hot Stamping of an Aluminium Alloy

“…This type of test enables the relatively easy ranking of the lubricants, but has the clear disadvantage of not being representative of actual friction values or distance before lubricant failure. In a study by Shafiee Sabet et al [15], a relatively simple contact configuration was used to replicate the contact conditions experienced in the forming of aluminium and evaluate lubricant behaviour at temperatures up to 100 • C. This tribometer has the advantage of using small samples and not being resource demanding, but it is not as widely spread and common in most testing facilities and it is unclear what the maximum temperature attainable is. There is a need to develop test methodologies using easily or readily available test equipment with simple configurations, which offers significant value when developing new lubricants for hot stamping of aluminium, because demand and interest is significant.…”