Tribology and Micro-Chemistry of Sputter Deposited Composite Coatings on Honed Steel Substrates
Wu, Lawrence Ching-Yu
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https://hdl.handle.net/2142/67024
Description
Title
Tribology and Micro-Chemistry of Sputter Deposited Composite Coatings on Honed Steel Substrates
Author(s)
Wu, Lawrence Ching-Yu
Issue Date
1980
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Language
eng
Abstract
The tribology and micro-chemistry of TiO(,2)-TiC composite coatings on chemically honed steel substrates has been investigated. The primary wear resistant coatings (TiC) were deposited by rf sputtering using a dc substrate bias and the solid lubricant coatings (TiO(,2)) were deposited in an Ar and O(,2) mixed rf glow discharge. Chemically honed steel substrates which consisted of a checkerboard of raised squares separated by 1.5 (mu)m deep channels were prepared by photolithographic and masking techniques. A pin-on-disc apparatus was used to measure friction and wear characteristics of composite coatings. The composite coating chemistry was analyized by Auger Electron Spectroscopy (AES); in addition, AES was used to characterize the wear transfer mechanism between steel and the composite coating.
A large improvement in the adhesive quality of TiC films deposited on flat steel substrates resulted from reducing the oxygen partial pressure during initial deposition. It was also found that under bias sputtering conditions in the presence of small amount of oxygen, carbon was preferentially chemically resputtered as oxygen was incorporated. The oxygen ions dissociate upon striking the surface and reacting with atoms in the film, producing volatile CO and CO(,2) as well as TiO(,2).
Advancing delamination cracks which caused failure of TiC films were stopped by the barriers in the honed steel surface. In addition the depth of honing controlled the effective TiC coating thickness. The transient friction and wear behavior associated with honed uncoated surface was greatly reduce when surface was coated with TiC. However, severe wear of rider was resulted when rubbing against coated, honed surface. TiO(,2) acting as a lubricant can reduce wear. However, its durability is strongly influenced by the nature of its failure mechanism during repeated wear cycles. The reservoir structure was found to be a valuable technique in wear reduction and in increasing the wear life of composite coatings. The trapping of wear debris was observed indicating that the choice of materials used for the composite coating is important in wear improvement.
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