Influence of laser structural patterning on the tribological performance of C-alloy TMD coatings

Abstract

IntroductionRising consumption of infinite energy resources because of economic growth and finding out how to generate growth with fewer resources have become the crucial issues throughout the world. Scientists have been investigating energy dissipation and material loss, particularly in relation to friction and wear, for more than 300 years. In fact, about one-third of world energy resources in the present use, appears as friction in one form or another. These two concepts, namely friction and wear, are considerably connected with the field of science called tribology [ ].Tribology is the technology and science of interacting surfaces in relative motion. The word tribology is derived from the Greek word ‘Tribos’ which means rubbing, so tribology would be the science of rubbing. Estimates show that the ignorance of tribology in the U.S. results in losses, equal to about 6% of its gross national product or about $200 billion per year. Thus, saving energy and materials using reducing friction and wear is a beneficial solution, also resulting in an increased lifetime of components [ , ]. Using solid lubricants is one the effective solutions to reduce the coefficient of friction and wear. These lubricants could be very beneficial in the systems where oil lubrication is not possible as the vacuum applications or the sliding contacts where the presence of contaminants must be prevented such as in food industry. In addition, most of the liquid lubricants are environmentally harmful as the European Union has been placing some restrictions on use of these materials [ ]. The liquid lubricants such as oils could also be evaporated in elevated temperatures, resulting in damage to surfaces. The tribofilms generated by these lubricants can maintain a steady thickness which remains unaffected by a load, temperature and the like. In solid lubricating, tribological contacts lead to a transferring a thin layer of material from the surface of the coating to the counterface, usually known as a transfer film or tribofilm. Due to chemical reactions with the surrounding environment, the wear surfaces can show different chemistry, microstructure, and crystallographic texture from those of the bulk coating; so, these coatings illustrate different characteristics in different environments. For example, a typical solid lubricant can give extremely low friction and long wear life in one environment and fail in a different environment [4].Diamond-like carbons (DLCs), transition metal dichalcogenides (TMDs), polymeric composite coatings and the like are among the solid lubricants which are commonly utilized. Usage of some surface and subsurface analytical techniques such as X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and so on has provided the fundamental understanding of synthesis-structure tribology relationships in solid lubricant materials [ , ]. The present research work is aimed at investigating the effect of laser structural patterning on the tribological performance of W-S-C coatings.

IntroductionRising consumption of infinite energy resources because of economic growth and finding out how to generate growth with fewer resources have become the crucial issues throughout the world. Scientists have been investigating energy dissipation and material loss, particularly in relation to friction and wear, for more than 300 years. In fact, about one-third of world energy resources in the present use, appears as friction in one form or another. These two concepts, namely friction and wear, are considerably connected with the field of science called tribology [ ].Tribology is the technology and science of interacting surfaces in relative motion. The word tribology is derived from the Greek word ‘Tribos’ which means rubbing, so tribology would be the science of rubbing. Estimates show that the ignorance of tribology in the U.S. results in losses, equal to about 6% of its gross national product or about $200 billion per year. Thus, saving energy and materials using reducing friction and wear is a beneficial solution, also resulting in an increased lifetime of components [ , ]. Using solid lubricants is one the effective solutions to reduce the coefficient of friction and wear. These lubricants could be very beneficial in the systems where oil lubrication is not possible as the vacuum applications or the sliding contacts where the presence of contaminants must be prevented such as in food industry. In addition, most of the liquid lubricants are environmentally harmful as the European Union has been placing some restrictions on use of these materials [ ]. The liquid lubricants such as oils could also be evaporated in elevated temperatures, resulting in damage to surfaces. The tribofilms generated by these lubricants can maintain a steady thickness which remains unaffected by a load, temperature and the like. In solid lubricating, tribological contacts lead to a transferring a thin layer of material from the surface of the coating to the counterface, usually known as a transfer film or tribofilm. Due to chemical reactions with the surrounding environment, the wear surfaces can show different chemistry, microstructure, and crystallographic texture from those of the bulk coating; so, these coatings illustrate different characteristics in different environments. For example, a typical solid lubricant can give extremely low friction and long wear life in one environment and fail in a different environment [4].Diamond-like carbons (DLCs), transition metal dichalcogenides (TMDs), polymeric composite coatings and the like are among the solid lubricants which are commonly utilized. Usage of some surface and subsurface analytical techniques such as X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), atomic force microscopy (AFM) and so on has provided the fundamental understanding of synthesis-structure tribology relationships in solid lubricant materials [ , ]. The present research work is aimed at investigating the effect of laser structural patterning on the tribological performance of W-S-C coatings.