Tribological Studies on Coating-Lubricant Combinations in Different Contact Configurations
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Diamond-like carbon (DLC) coatings are increasingly being used for both friction reduction and wear protection of machine elements working under boundary lubricated conditions. In this work, the use of DLC coatings for various interfaces of a radial piston hydraulic motor was evaluated. Tribological studies were carried out on different combinations of DLCs and lubricants, using a range of contact configurations. Two types of tetrahedral amorphous carbon (ta-C) DLC coatings (of varying thickness and surface morphology) and seven hydraulic oils (of different API groups and additive packages) were tested. Different tribological test configurations used were steel cylinders against DLC coated steel discs (non-conformal line contact) under reciprocating sliding motion; cast iron blocks against DLC coated steel rings (non-conformal line contact) under unidirectional sliding motion; and cast iron pins against DLC coated steel discs (conformal area contact) under unidirectional sliding motion. As the contact configuration changed, coating characteristics (including roughness and hardness) influenced the tribological performance of the different coating-lubricant combinations tested. The tribological behaviour of the lubricating oils varied according to the contact conditions and the DLC coating surface morphology. Mineral base oils with rust inhibitors or synthetic polyalphaolefins, and synthetic ester base oils gave excellent friction and wear reduction, depending upon the DLC coating roughness and the test setup. Zinc containing oils increased both friction and counter surface wear. These results have shown that the tribological behaviour of ta-C DLC coatings in boundary lubricated conditions is influenced by four factors, i.e., the contact configuration; the lubricant chemistry; the surface morphology of the DLC coating; and the nature of the counter surface.
Place, publisher, year, edition, pages
2015. , 130 p.
Technology, Diamond-like carbon (DLC) coating, conformity, lubrication regimes, running-in, lubricant additives
IdentifiersURN: urn:nbn:se:ltu:diva-59355Local ID: fe427b01-5d7c-46c7-bb82-0461612d0468OAI: oai:DiVA.org:ltu-59355DiVA: diva2:1032742
Subject / course
Student thesis, at least 30 credits
Mechanical Engineering, master's level
Validerat; 20151208 (global_studentproject_submitter)2016-10-042016-10-04Bibliographically approved