All ETDs from UAB

Advisory Committee Chair

Andrei Stanishevsky

Advisory Committee Members

Shane Aaron Catledge

Amber L Genau

Gregg M Janowski

Yogesh K Vohra

Document Type

Dissertation

Date of Award

2012

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The microstructure, thermal stability and mechanical properties of ternary chromium molybdenum nitride (Cr-Mo-N) films were studied. In this work, a series of Cr-Mo-N films with different Cr/Mo ratios were deposited on CoCrMo and silicon substrates at various deposition temperatures by using a dual rf-magnetron sputtering system with Cr and Mo targets and nitrogen as reactive gas. Thermal processing at temperatures up to 700°C in air and up to 800°C in microwave plasma with H2/N2 gas mixture were employed to evaluate the thermal stability of films. The films' microstructure was investigated by scanning electron microscope (SEM) and X-ray Diffraction (XRD). The surface morphology was studied by atomic force microscopy (AFM), and the chemical composition was analyzed by X-ray photoelectrons spectroscopy (XPS) and Energy-Dispersive X-ray Spectrometer (EDS). The mechanical properties were studied by Nanoindentation and Tribometry. The coatings exhibited mainly face centered cubic (fcc) structure with some secondary phase precipitates. All as prepared films showed mean grain size 13-21 nm and the lattice parameters varying between those of cubic CrN and Mo2N depending on the composition. The surface roughness of the films varied from the pure CrN and pure Mo2N in the nanoscale range. The hardness and Young's modulus were found in the range of 9.0 - 22 GPa and 175- 330 GPa, respectively, with larger values observed for Mo-rich layers. The coefficient of dry friction with Ti counterpart varied from 0.41 to 0.67. Thermal stabilities of Cr-Mo-N coatings during the annealing up to 700°C in air have been studied. It has been found that Cr1-xMoxNy films with Cr-rich content are more stable than those with Mo-rich content. All properties were improved by increasing the deposition temperature.

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