Riassunto analitico
Tribological problems such as friction and wear in moving mechanical assemblies leading to energy dissipation and mechanical failures have always been focused to industry concerns. In fact, surface degradation caused by friction, wear and corrosion have a detrimental and costly impact on machinery, manufactured products and production efficiency. Tribological research for the most appropriate friction and wear values is essential in industry for parts and assemblies to function properly, thus allowing to lower costs and to reduce waste. Indeed, in most practical applications, the primary interest in the study of friction is sustained by the fact that the reduction of friction is directly linked to energy savings. Numerous techniques such as solid coating protection or liquid lubrication have been developed to minimize friction and wear. Diamond-like-carbon (DLC) is an example of a widely used solid lubricant both in industry and experimental studies, thanks to his optimal performances in terms of wear resistance, coefficient of friction value, and thermal stability. In the context of the study of friction and wear, both the properties of the involved materials and the test conditions have a combined impact on the final results. Concerning the test conditions, many structure types of wear-testing machine have been developed which allow to control exterior factors as load, sliding speed and distance, environment, and contact geometry, in order to simulate the actual working conditions. However, in most of the studies the friction and wear test is just taken as a tool to evaluate the performance of materials. Few papers are available on the study of the effect of the test method and experimental apparatus on the tribological performance of materials. As a consequence, the mechanisms underlying the complicated movements involving real mechanical components are far from understanding. Hence, it is interesting to study the effects that different test methods can produce on friction and wear performance of materials. In this thesis project, the tribological behaviour of aluminum samples coated with DLC films of two thickness values against a WC counterpart was studied. In particular, the focus was posed on the response of DLC films under two different sliding motion configurations, reciprocating and unidirectional. The two kind of tests were performed under comparable experimental conditions of applied load and sliding velocity, in humid air and at ambient temperature. The coefficient of friction and wear results were compared and additionally the structural and chemical characteristics of the worn surface on both the sample and counterpart were inspected using Raman spectroscopy and SEM analysis with EDS (Energy-Dispersive x-ray Spectroscopy).
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Abstract
Tribological problems such as friction and wear in moving mechanical assemblies leading to energy dissipation and mechanical failures have always been focused to industry concerns. In fact, surface degradation caused by friction, wear and corrosion have a detrimental and costly impact on machinery, manufactured products and production efficiency. Tribological research for the most appropriate friction and wear values is essential in industry for parts and assemblies to function properly, thus allowing to lower costs and to reduce waste. Indeed, in most practical applications, the primary interest in the study of friction is sustained by the fact that the reduction of friction is directly linked to energy savings.
Numerous techniques such as solid coating protection or liquid lubrication have been developed to minimize friction and wear.
Diamond-like-carbon (DLC) is an example of a widely used solid lubricant both in industry and experimental studies, thanks to his optimal performances in terms of wear resistance, coefficient of friction value, and thermal stability. In the context of the study of friction and wear, both the properties of the involved materials and the test conditions have a combined impact on the final results. Concerning the test conditions, many structure types of wear-testing machine have been developed which allow to control exterior factors as load, sliding speed and distance, environment, and contact geometry, in order to simulate the actual working conditions. However, in most of the studies the friction and wear test is just taken as a tool to evaluate the performance of materials. Few papers are available on the study of the effect of the test method and experimental apparatus on the tribological performance of materials. As a consequence, the mechanisms underlying the complicated movements involving real mechanical components are far from understanding. Hence, it is interesting to study the effects that different test methods can produce on friction and wear performance of materials. In this thesis project, the tribological behaviour of aluminum samples coated with DLC films of two thickness values against a WC counterpart was studied. In particular, the focus was posed on the response of DLC films under two different sliding motion configurations, reciprocating and unidirectional. The two kind of tests were performed under comparable experimental conditions of applied load and sliding velocity, in humid air and at ambient temperature. The coefficient of friction and wear results were compared and additionally the structural and chemical characteristics of the worn surface on both the sample and counterpart were inspected using Raman spectroscopy and SEM analysis with EDS (Energy-Dispersive x-ray Spectroscopy).
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