Environmental awareness and especially the legislation that requires the reduction of polluting emissions are strong driving forces toward more sustainable engineering and greener solutions in the design, use and overall life span of machinery. However, providing novel concepts that will exclude non-environmentally adapted, but over many years developed and optimized solutions, is not an easy task. It clearly requires time if the same level of technical performance is to be maintained. Green tribology is one of the fields that has been closely involved in these actives in the past two decades. The research and use of tribology science and technology toward green and sustainable engineering include natural material usage, lower energy consumption, reducing natural oil resources, reducing pollution and emissions, fewer maintenance requirements and thus reduced machinery-investment cycles. This report is not an attempt to cover all the existing concepts, attempts or literature available in the field, but mainly those efforts that our group has been working on over the past 20 years, which mainly includes novel green-lubrication concepts that come from exploring and exploiting surface engineering through the use of diamond-like-carbon (DLC) coatings.
COBISS.SI-ID: 16945179
In this study several lubricants with different surface tensions and polarity were used for self-mated lubricated contacts of steel and different DLC coatings at different temperatures. DLC coatings types were selected in order to provide different surface energies as well as different thicknesses. It was found that high temperature favour lower EHD friction due to lower pressure-viscosity coefficient and lower friction reduction when using DLC coatings due to lower limiting shear stress in case of prevailing slip (F-DLC coating) and due to lower temperature increase in case of prevailing thermal effect (a-C:H6 coating). For F-DLC coating with prevailing slip effect the higher reduction will be obtained for oils with higher surface tension and polarity that are more likely to slip. The a-C:H6 coating will reduce friction more for oils that for steel/steel contact provides higher friction due to more heat generation. Iw was also found that the effect of coating thickness in terms of emphasized thermal effect loss its role when these three conditions are met: high test temperature, high oil surface tension and high oil polarity. In this case the slip effect will prevail over thermal one.
COBISS.SI-ID: 16682779