Improvement of Diamond-Like Carbon Adhesion on CoCrMo by Microdiamond and Nitrogen Incorporation for Wear Resistant Applications
Date
2017-09-25
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Masters
Abstract
Coating the joint surfaces with diamond like carbon (DLC) is a promising way to increase the
service lifetime of hip joints made of CoCrMo alloy. DLC thin films have been attracted the most
interest because of its extreme smoothness, low coefficient of friction, high hardness and
excellent biocompatibility. One of the key issues that limit the use of DLC is its poor adhesion to
commonly used biomedical alloys like CoCrMo. The low adhesion has been attributed to the
high internal stress, and Nitrogen (N) doping is one of main approaches to minimize it.
Nevertheless Nitrogen incorporation is being investigated due to the complex mechanism behind
the formation of different chemical species in the amorphous DLC network by using different
deposition techniques.
In the present thesis work, micro-diamond particles were synthesized on CoCrMo alloy sheets by
Microwave Plasma Enhanced Chemical Vapor Deposition (MPCVD) and nitrogen doped DLC
thin films were then deposited on them by Inductively Coupled Plasma assisted Chemical Vapor
Deposition (ICP-CVD) to improve DLC adhesion on CoCrMo sheets. The effect of nitrogen
doping and nanodiamond incorporation on the film adhesion was investigated by Rockwell
indentation. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to
analyze the chemical structure of the coatings. Morphology of the films was observed by
Scanning electron microscopy (SEM) and optical profilometry. The mechanical properties of the
films were measured by nanoindentation testing. Results showed that Nitrogen doping and
diamond incorporation could improve the film adhesion significantly. Raman and XPS spectra
showed an increase in sp2
bonding in N-DLC films with a consequent decrease in hardness
according to nanoindentation measurements. Surface roughness decreased while nitrogen content
increased according to optical profilometer images. The results have demonstrated that the
modified DLC films are promising for total hip joint replacement application.
Description
Keywords
DLC, Adhesion, CoCrMo, Nitrogen, Diamond, ICP-CVD
Citation
Degree
Master of Science (M.Sc.)
Department
Mechanical Engineering
Program
Mechanical Engineering