Influence of soot on tribological performance of uncoated and DLC-coated lubricated contacts. Friction and wear analysis.

Abstract

This project is motivated from now days trends in the automotive industry to increase fuel efficiency and fulfill environmental standards. To do so the increase of soot (carbon black particles) in the Internal Combustion Engines has become a big issue, challenging the environmental impact of disposing oil and overall maintenance cost of running a vehicle. Diamond Like Carbon (DLC) thin films are widely used for protection of components under high load from wear and/to reduce friction loses in combustion engines. To furthermore increase the properties of DLC, using Magnetron Sputtering (DCMS), standard steel balls for the 4 Ball Tester were coated with DLC doped with tungsten (W-DLC) and DLC doped with silver (Ag-DLC). In basic, the interaction among soot/W-DLC coated steel surfaces and soot/Ag-DLC coated steel surfaces as a possible solution to the soot wear problems and further development of soot wear resistant lubricants has been investigated. Before the test, the type of contact of the tribopair has been studied. Friction and wear properties of W-DLC and Ag-DLC have been tested in boundary lubrication conditions using a 4 Ball Test. To check the coating efficacity and its interaction with the base oil(Ester Base Oil), additive (Glycerol Monooleate) and soot (Carbon Black), Optical Microscope for wear scar images, 3D Profilometry to obtain the 3D profile of the wear scar and Raman Spectroscopy to check on the coating structure have been applied. Test results showed the benefit of the W-DLC/Steel and Ag-DLC/Steel contact over the Steel/Steel contact.

This project is motivated from now days trends in the automotive industry to increase fuel efficiency and fulfill environmental standards. To do so the increase of soot (carbon black particles) in the Internal Combustion Engines has become a big issue, challenging the environmental impact of disposing oil and overall maintenance cost of running a vehicle. Diamond Like Carbon (DLC) thin films are widely used for protection of components under high load from wear and/to reduce friction loses in combustion engines. To furthermore increase the properties of DLC, using Magnetron Sputtering (DCMS), standard steel balls for the 4 Ball Tester were coated with DLC doped with tungsten (W-DLC) and DLC doped with silver (Ag-DLC). In basic, the interaction among soot/W-DLC coated steel surfaces and soot/Ag-DLC coated steel surfaces as a possible solution to the soot wear problems and further development of soot wear resistant lubricants has been investigated. Before the test, the type of contact of the tribopair has been studied. Friction and wear properties of W-DLC and Ag-DLC have been tested in boundary lubrication conditions using a 4 Ball Test. To check the coating efficacity and its interaction with the base oil(Ester Base Oil), additive (Glycerol Monooleate) and soot (Carbon Black), Optical Microscope for wear scar images, 3D Profilometry to obtain the 3D profile of the wear scar and Raman Spectroscopy to check on the coating structure have been applied. Test results showed the benefit of the W-DLC/Steel and Ag-DLC/Steel contact over the Steel/Steel contact.