Modification of sheet metal forming fluids with dispersed nanoparticles for improved lubrication

Sheet metal working fluids are used for reducing wear of forming sheets and dies and lowering friction at the die/workpiece interface. The reduction of friction and wear results in fewer defects and improved geometric and surface finish quality. In this paper, nanoparticles of several materials with known solid lubrication properties such as molybdenum disulfide (MoS2) tungsten disulfide (WS2), and hexagonal boron nitride (hBN) were dispersed in commercial sheet metal forming fluids by sonication and their tribological properties were evaluated using laboratory tribotesting. The sheet metal materials were titanium and carbon steel whereas 440C balls were used as the counterfaces to represent the die material. The experimental results indicated that in 440C ball-titanium sheet pairs sliding in the presence of the modified oil with nanoparticles, the wear volume of titanium sheets was reduced by as much as 25-30% in certain nanoparticle particle concentrations. In the 440C ball-steel sheet sliding pairs, the wear volume of the 440C balls was reduced by as much as 55-65% using the modified fluid. The friction coefficient of ball-titanium systems was reduced by as much as 10% in some cases, but it showed no noticeable improvement in 440C ball-steel pairs using the modified fluid. Mechanisms by which modified oils with dispersed nanoparticles improve tribological behaviour are discussed. (C) 2009 Elsevier B.V. All rights reserved.