Current Issue : January - March Volume : 2015 Issue Number : 1 Articles : 4 Articles
Abrasive resistant coatings have been widely used to reduce or eliminate wear,\nextending the lifetime of products. Abrasive resistant coatings can also be used in certain\nenvironments unsuitable for lubrications. Moreover, abrasive resistant coatings have been\nemployed to strengthen mechanical properties, such as hardness and toughness. Given\nrecently rapid development in abrasive resistant coatings, this paper provides a review\nof major types of abrasive coatings, their wearing mechanisms, preparation methods,\nand properties....
Nanofluids are nanosize-powder suspensions that are of interest for their enhanced thermal transport properties.They are studied as\npromising alternatives to ordinary cooling fluids, but the tribiological effects of nanofluids on cooling-system materials are largely\nunknown. The authors have developed methodology that uses jet impingement on typical cooling-system materials to test such\neffects.Thework is presented of the authors� research on the interactions of a typical nanofluid (2% volume of alumina nanopowders\nin a solution of ethylene glycol in water) which is impinged on aluminum and copper specimens for tests as long as 112 hours. The\nsurface changes were assessed by roughness measurements and optical-microscope studies. Comparative roughness indicate that\nboth the reference cooling fluid of ethylene glycol and water and its nanofluid with 2% alumina produce roughness changes in\naluminum (even for the shortest 3-hour test), but no significant roughness differences were observed between them. No significant\nroughness changes were observed for copper. Microscopy observations, however, show different surface modifications in both\naluminum and copper by both the nanofluid and its base fluid. The possible mechanisms of early erosion are discussed. These\ninvestigations demonstrate suitable methods for the testing of nanofluid effects on cooling system-materials....
The newly synthesized perfluoropolyether (PFPE) ionic liquid whose terminal group is an ammonium salt with a carboxylic\nacid has better frictional properties when compared to the conventional PFPEs. Stick-slip motion was not observed even for the\nsmooth surface for the modified PFPE tape. The friction is almost independent of the PFPE structure, but depends on the amine\nstructures. The ammonium salt being tightly anchored to the rubbing surface covers uniformly, which leads to better lubricity. The\nhigher dispersive interaction of the hydrophobic group of the amine is endowed with a compensating friction reduction. Steric\nhindrance of the hydrophilic group causes a high friction. Based on these findings, a saturated long chain ammonium salt is the\nbest selection. Moreover, the modified PFPEs are dissolved in alcohol and hexane, which makes practical use convenient without\nany environmental problems. These ionic lubricants invented around 1987 have been used for magnetic tapes for about a quarter\ncentury because of their good lubricity and are reviewed in this paper....
The aim of the study is to evaluate the friction and wear behavior of high-strength alloys Ti-6Al-7Nb used in femoral stem and\ncompare it with a Ti-6Al-4V alloy cylindrical bar corresponding to ISO 5832-3 part 3/01-07-199 standard.The tribological behavior\nwas investigated by wear tests, using ball-on-disc and pin-on-disc tribometers. These tests consisted of measuring the weight loss\nand the friction coefficient of samples. The oscillating friction and wear tests have been carried out in ambient with oscillating\ntribotester in accordance with standards ISO 7148, ASTMG99-95a, and ASTMG133-95 under different conditions of normal loads\n(3, 6, and 10N) and sliding speeds (1, 15, and 25mm?s?1). As counter pairs, a 100Cr6 steel ball with 10 mm in diameter was used.\nResults show that the two alloys had similar friction and wear performance, although their grain structures and compositions are\ndifferent. Occurrence of large frictional occurred, is probably caused by formation and periodic, localized fracture of a transfer\nlayer. Higher friction with larger fluctuation and higher wear rate was observed at the higher siding speed. The Ti-6Al-4V wear\nmechanism transforms from ploughing and peeling off wear at low sliding speed to plastic deformation and adhesive wear....
Loading....