TRIBOLOGY

Author: IGLESIAS VICTORIA PATRICIA.
Year: 2003.
University: POLITÉCNICA DE CARTAGENA [www.upct.es].
Place of defense: INGENIEROS INDUSTRIALES.
Place of preparation: ESCUELA TÉCNICA SUPERIOR DE INGENIERÍA INDUSTRIAL.

Summary: Two strategies have been developed to improve the performance tribológico torque aluminio-acero: 1. Using fluid ordered the type of ionic liquids and liquid crystals, as additives in lubricating a conventional aluminum alloy in its slide against steel, 2. Studying the behavior tribológico new materials pulvimetalúrgicaos base alumninio ebtenidos by mechanical alloy. In this paper we have used three liquid crystals and liquid as additives to 1% by weight of a base oil parafínico nafténico.Los liquid crystals were selected by the increasing polarity of their molecules: 4.4 '-dibutilazobencero (CL1) lower colesteril linoleato (CL2) lower chloride dodecilamonio (CL3). Moreover, in this work has been used for the first time an ionic liquid. (Tetrafluoruro of 1-etil, 3-metil-imidazolonio) as lubricant additive. We have determined the values of viscosity at 25 and 100Â ° C for new lubricants, as well as the maximum number of molecules that can be aligned additive per unit area and the approximate cost of each of the aditivos.Todo it reflects the advantage the ionic additives on the neutral. Tests have been conducted on friction and wear to load, speed and temperature using variable settings on spike, according to the ASTM G99. The behavior of liquid crystals depends on the conditions experimentadas.Así CL3 is the one that presents a greater reduction dela friction and desgastae of aluminum -acero able to severe contact, ie high loads, speeds and temperatures, while the ionic liquid remains low values of friction (less 0.1) and attrition (less 10-5 mm3m-1) in the full range of conditions tested. Moreover, it has established the interactions triboquímicas of ionic additives with steel surfaces and aluminio.Sólo liquid ion leads to the formation of compounds luminio containing fluorine may well harden the surface of the aluminum and reduce wear . The second part of the work has been studied the influence of manufacturing processes on the tribological properties of new materials pulvimetalúrgicos based aluminum, both dry and lubricating base oil used in the absence of additives. It has been studied a new material under mechanically alloyed atmosphere amonicaco, compared with other mechanically alloyed in the air, as well as aluminum pulvimetalúrgico simple qu has not been mechanically alloyed prior to the consolidation process. We have established loads and temperatures transitional wear soft desgarte more severe for each of the materials. While aluminum simple worn harsh and at room temperature for loads exceeding 1.23 N, mechanically alloyed material in ammonia worn soft to 150Â ° C with a reduced rate of attrition of 60% over the mechanically alloyed material in air and until the orders of magnitude with respect to luminio simple. The higher wear resistance of the material mechanically alloyed low ammonia is attributed to the increase in hardness and reduced poncentaje porosity, as well as its fine microstructure reinforced by the presence of phases endurecedoras submicroscópicas the type of aluminum nitrides and carbides. In all cases have been established 8 the mecca 368 tional wear through microscopic observation and microanalysis of the footprints and wear particles.

Author: GÓMEZ BOTERO ASTRID MARYORY.
Year: 2005.
University: BARCELONA [www.ub.es].
Place of defense: UNIVERSITAT DE BARCELONA.
Place of preparation: UNIVERSITAT DE BARCELONA.

Summary: The purpose of this paper is to evaluate the mechanical and tribological properties of several hard coatings made by techniques PVD, through tests conducted in a ball on disk without lubrication and a team abrasive. Additionally study the mechanical properties of the coatings concerned as hardness, modulus of elasticity, and tensions accession. Also to understand as far as circumstances permit mechanisms that occur at the surface interactions in the tribological tests. The coatings CrC obtained by evaporation by cathodic arc showed some coatings with amorphous structure and excess carbon obtained with acetylene pressure of 6.1 Pa presenting friction coefficients as low as 0.05 and a very low wear. With the slightest pressure of methane, 0.4 Pa, coatings were obtained with crystalline structure Cr3C2, coefficients of friction with senior (0.4-0.7) and a substantial wear. The harshness of these coatings ranged from 23 to 10 Gpa as increased pressure from acetylene. -0.5) and the rate of wear slip 1.5x10 -14 m3/Nm. Other coatings of this group showed contained carbon sub-estequiométricos of phase Cr3C2, which presented high friction coefficients, up to 0.7 and high attrition rates. A third group of CrC these coatings deposited by cathodic spraying magnetron revealed excess carbon, which exhibited low coefficients of friction and wear rates reduced, but without reaching the very low coefficient of friction and wear rates very low reached samples deposited by arc. Also explored multilayer coatings Cr / CrC spray deposited by cathodic mangetrón varying thickness period of multilayers and a monolayer coatings of Cr3C2 for comparison purposes. It was found that the tribological properties of each of the layers that form the multilayer determine the tribological properties dela estructuramulticapa. The friction in the first test cycles, reflecting the ratio of the outer layer that was always that of CrC, but once this layer is worn, the friction increased due to the chromium layer. A detailed study of wear in the multislice allowed to determine the mechanism of wear layer to layer and the changes in friction coefficient associated with this mechanism. The thickness of the multi-period showed a minimal influence on friction. The multilayer coatings presented on the other hand, better resistance to wear slip that the coating reference CrC. The multilayer coatings with a lower thickness period showed values lower tensions and the highest values of critical loads. The critical loads for membership showed that the multilayers exceeded the critical load of the single reference. We studied coatings CrAIN presenting hardnesses extremely high, compared with the usual hard coatings. The harshness of these coatings increases when, in the shell, is increased polarization negative substrate until -300V. All strains CrAIN exceeded the hardness that had layers reference CrN. The coatings CrAIN revealed high friction coefficients to be considered a good coating tribológico however, the rate of attrition is presenting the lowest of all coatings studied.