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«by YUJIAO ZOU ANDREI STANISHEVSKY, CHAIR SHANE AARON CATLEDGE AMBER L GENAU GREGG M JANOWSKI YOGESH K VOHRA A DISSERTATION Submitted to the graduate ...»

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THE MICTROSTRUCTURE, MECHANICAL PROPERTIES, AND THERMAL

STABILITY OF TERNARY Cr1-xMoxNy THIN-FILMS

by

YUJIAO ZOU

ANDREI STANISHEVSKY, CHAIR

SHANE AARON CATLEDGE

AMBER L GENAU

GREGG M JANOWSKI

YOGESH K VOHRA

A DISSERTATION

Submitted to the graduate faculty of The University of Alabama at Birmingham, in partial fulfillment of the requirements for the degree of Doctor of Philosophy

BIRMINGHAM, ALABAMA

2012 ii

THE MICTROSTRUCTURE, MECHANICAL PROPERTIES, AND THERMAL

STABILITY OF TERNARY Cr1-xMoxNy THIN-FILMS

YUJIAO ZOU

PHYSICS

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 CrN and γ-Mo2N depending on the composition. The surface roughness of the films varied from the pure CrN and pure γ-Mo2N in the nanoscale range. The hardness and Young’s modulus were found in the range of 9.0 - 22 GPa and 175- 330 iii 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.

Key words: Magnetron sputtering, Thermal stability, Mechanical property, Chromium

–  –  –

Time flies! I can't imagine I am going to finish my PhD work soon. The accomplishment of my PhD would not be achieved without many people to whom I would like to express my sincere gratitude.

First of all, I would like to express my gratitude to Dr. Andrei Stanishevsky.

During my doctoral studies he directed me to the thin films and surface engineering field, and guided me through the research, answered many theoretical questions and helped me with the experimental work. He always endorsed my curiosity and gave me freedom to pursue different scientific problems.

Secondly, thank Dr. Yogesh K Vohra, it is his Nanoscale Science and Applications class introduced me to the science of nanotechnology and generated my research interest in nanostructured thin film materials.

The third to whom I owe great deal is Dr. Shane Aaron Catledge. He unselfishly shared his knowledge, helped and trained me in many experiment techniques.

My gratitude goes also to Dr. Corinne Nouveau, Issam Rahil, Luc Imhoff, from Laboratoire Bourguignon des Matériaux et Procédés, CER Arts et Métiers ParisTech of Cluny, France for performing magnetron sputtering system and TEM/SEM measurements.

A special gratitude goes to my collogue Michael Walock, I am deeply indebted to for his help and support with my doctoral work.

I would also like to express my gratitude to Gopi Samudrala and Leigh Booth, for

–  –  –

I want to express my gratitude to everyone who helped me with the theoretical and experimental work, and people in Physics department at UAB, for friendly atmosphere and for help with practical work.

At the end, I would like to thank my parents and friends. Your friendship and understanding, which I received during the years, helped me to overcome burdens of

–  –  –

ABSTRACT……………………………………………………………………………..ii ACKNOWLEDGMENTS………………………………………………………………iv LIST OF TABLES……………………………………………………………………viii LIST OF FIGURES…………………………………………………………………….ix CHAPTER State-of-the-art in hard coatings ……………………………………...…..…...1 1.

1.1. Introduction to hard coatings





1.2. Review of binary nitride coatings

1.3. Review of ternary nitride coatings

1.4. Deposition Methods

1.4.1 Magnetron Sputtering

1.4.2 Cathodic Arcs

1.5. Influence of deposition parameters on film's microstructure

1.6. Stress in the films

1.7. Structure/property relationship for hard coatings

1.8. Case of ternary CrMoN coatings

1.9. Goals of the research

2. Experimental approaches

–  –  –

2.2.3 Characterization of film's mechanical properties

2.2.3.1 Nanoindentation

2.2.3.2 Tribometry

2.2.3.3 Stress measurements

3. Cr-Mo-N coatings on CoCrMo substrates

3.1. Sample preparation

3.1.1 Film deposition

3.1.2 Thermal processing of films

3.2. Experimental results of structure and morphology

3.2.1 Scanning Electron Microscopy (SEM)

3.2.2 X-Ray Diffraction (XRD)

3.2.3 X-ray Photoelectron Spectroscopy (XPS)

3.2.4 Atomic Force Microscopy (AFM)

3.3. Mechanical properties

3.3.1 Nanoindentation

4. Cr1-xMoxNy coatings on Si substrates

4.1. Samples preparation

4.1.1 Film deposition

4.1.2 Thermal processing of films

4.2. Experimental results of structure and morphology

4.2.1 Scanning Electron Microscopy (SEM)

4.2.2 X-Ray Diffraction (XRD)

4.2.3 Transmission Electron Microscopy (TEM)

4.2.4 X-ray Photoelectron Spectroscopy (XPS)

4.2.5 Energy Dispersive X-ray Spectrometry (EDS)

4.2.6 Stress

4.2.7 Atomic Force Microscopy (AFM)

4.3. Mechanical properties

4.3.1 Nanoindentation

4.3.2 Tribology

5. Discussion and Conclusion

–  –  –

Table1.1 Selected properties of metallic hard materials

Table 3.1 Overview of CrMoN coatings with different thermal processes

Table 3.2 Mechanical properties and surface roughness overview of the CrMoN coatings under various thermal processes

Table 4.1 Deposition parameters of the as-deposited Cr 1-x Mo x N y coatings on Si substrates

Table 4.2 Chemical composition of the Cr 1 - x Mo x N y coatings deposited at 400°C

Table 4.3 Residual stress in the Cr1-xMoxNy coatings deposited at 400°C.

...........82 Table 4.4 Deposition parameters of multilayer coatings CrN/MoN (m1),(m2) and single layer Cr 25 Mo 25 N50 coatings deposited at room temperature (c1) and high temperature (c2)

Table 4.5 Selected properties overview of the Cr-Mo-N coatings deposited at

–  –  –

Fig1.1 Growth of production in German machine industry

Fig1.2 Standard coatings developed in the last three decades

Fig1.3 Film vapor deposition process flow diagram

Fig1.4 Schematic diagram of a typical magnetron sputtering system

Fig1.5 Schematic diagram of a typical cathodic arc source

Fig1.6 Structure Zone Diagram for plasma based thin film deposition.................16 Fig2.1 The Nordiko 3500 RF magnetron sputtering system

Fig2.2 The vacuum diagram of the magnetron sputtering system

Fig2.3 Guns arrangement of the sputtering system

Fig2.4 Substrate holder in the chamber of the sputtering system..........................24 Fig2.5 The electrode beneath the substrate holder

Fig2.6 Schematic diagram of a typical Scanning Electron Microscopy................27 Fig2.7 Mechanism of the beam hitting sample in a SEM

Fig2.8 Schematic diagram of a typical Transmission Electron Microscopy.........30 Fig2.9 Diagram of Bragg's Law

Fig2.10 Schematic diagram of the X-ray beam detection in XRD

Fig 2.11 a)Spring depiction of cantilever b) SEM image of triangular SPM cantilever

–  –  –

Fig2.12 Schematic of AFM instrument showing "beam bounce" method of detection using a laser and position sensitive photodiode detector

Fig2.13 Plot of force as a function of probe-sample separation

Fig2.14 Ideally a probe (tip) with a high aspect ratio will give the best resolution. The radius of curvature of the probe leads to tip convolution. This does not often influence the height of a feature but the lateral resolution

Fig2.15 The mechanism of X-ray ejecting electrons in XPS

Fig2.16 A typical load-displacement curve of fused silica

Fig2.17 Load-displacement curve showing the unloading (Su) and loading (Sl) slopes used in calculation of hardness and Young's modulus. Also indicated is the plastic work of indentation Wp which is the area bounded by the loading and unloading curves and the displacement axis

Fig2.18 The mechanism diagram of the tribometer

Fig2.19 An image of a typical CSM nanotribometer

Fig2.20 Image of a Wyko NT1100 Profilometer

Fig3.1. A cross-sectional scanning electron micrograph of the as-prepared Cr25Mo25N50 coating

Fig3.2 X-ray diffraction patterns of (1) as-deposited CrMoN ternary film, (2) annealed in air at 800°C, and (3) annealed in H2/N2 microwave plasma at 800°C

Fig3.3 XPS results of (1) as deposited CrMoN coating

Fig3.4 XPS results of (2) CrMoN coating annealed in air at 800°C

–  –  –

Fig3.6 XPS results of (4) annealed in air at 600°C+in mw plasma at 800°C ….. 55 Fig3.7 XPS results of (5) annealed in mw plasma at 800°C+in air at 800°C.......55 Fig3.8 Atomic Force Microscopy (AFM) results of Cr25Mo25N50 coatings under different treatments (1) as deposited Cr25Mo25N50 coating (2) annealed in air at 800°C (3) annealed in mw plasma at 800°C

Fig3.9 AFM picture of (4) annealed in air at 600°C+in mw plasma (5) annealed in mw plasma +in air at 800°C

Fig3.10 Mechanical properties of (1) as deposited CrMoN coating (2) annealed in air at 800°C (3) annealed in mw plasma at 800°C (4) annealed in air at 600°C+in mw plasma (5) annealed in mw plasma +in air at 800°C

Fig4.1 SEM cross-section image of (c1) Cr25Mo25 N50 and (b1) Cr32Mo18 N50 films deposited at room temperature

Fig4.2 The surface morphology SEM images of the as-deposited (a1)CrN (b1) Cr32Mo18N50 (c1) Cr25Mo25N50 (d1) Cr18Mo32N50 (e1)MoN coatings deposited at room temperature

Fig4.3 Cross sectional and surface SEM pictures of (a2)CrN (b2)Cr 32 Mo 18 N 50 (c2)Cr25Mo25N50 (d2)Cr18Mo32N50 (e2)MoN coatings deposited at 400°C...........64 Fig4.4 SEM picture of as deposited (a2)CrN (b2)Cr 32 Mo 18 N 50 (c2)Cr 25 Mo 25 N 50 (d2)Cr 18 Mo 32 N50 (e2)MoN coatings deposited at 400°C annealed in air at 600°C

Fig4.5 SEM picture of (a2)CrN (b2)Cr32Mo18N50 (c2)Cr25Mo25N50 coatings deposited at

–  –  –

Fig4.6 XRD patterns of as deposited (a1)CrN (b1)Cr 32 Mo18 N50 (c1)Cr 25 Mo25 N50 (d1)Cr18Mo32N50 (e1)MoN deposited at room temperature

Fig4.7 XRD patterns of (a1)CrN (b1)Cr 32Mo18N50 (c1)Cr25Mo25N50 (d1)Cr18Mo32N50

–  –  –

600°C

Fig4.8 XRD patterns of (a1)CrN (b1)Cr32Mo18N50 (c1)Cr25Mo25N50 deposited at room temperature after annealed at air at 700°C

Fig4.9 XRD patterns of (a2)CrN as deposited at 400°C and under thermal processes

Fig4.10 XRD patterns of (e)MoN as deposited at 400°C and under thermal processes

Fig4.11 XRD patterns of (d2) Cr18Mo32N50 as deposited at 400°C and under thermal processes

Fig4.12 XRD patterns of (b2) Cr32Mo18N50 as deposited at 400°C and under thermal processes

Fig4.13 XRD patterns of (c2) Cr25Mo25N50 as deposited at 400°C and under thermal processes

Fig4.14 Lattice parameters CrxN and MoxN selected (111) or (200) crystal plane as a function of Mo content

Fig4.15 TEM high magnification cross-sectional and surface morphology of (c1) Cr25Mo25N50 coatings deposited at room temperature

Fig4.16 XPS results of (a1)CrN (c1) Cr25Mo25N50 (e1)MoN coatings deposited at room

–  –  –

Fig4.17 XPS results of as deposited (a2)CrN (b2)Cr 32 Mo18 N50 (c2)Cr 25 Mo 25 N 50 (d2)Cr18Mo32N50 (e2)MoN coatings deposited at 400°C

Fig4.18 AFM images of (a1)CrN (b1)Cr 32Mo18N50 (c1)Cr25Mo25N50 (d1)Cr18Mo32N50 (e1)MoN coat ings deposit ed at room t em perat ure....................83 Fig4.19 Surface roughness changes of (a1)CrN (b1)Cr 32 Mo 18 N50 (c1)Cr 25 Mo25 N50 deposited at room temperature after annealing processes……………………......84 Fig4.20 Surface roughness changes of (a2)CrN (b2)Cr 32 Mo 18 N50 (c2)Cr 25 Mo25 N50 (d2)Cr 18 Mo 32 N 50 (e2)MoN coatings deposited at 400°C after annealing processes

Fig4.21 Hardness and Young’s Modulus changes of (a1)CrN (b1)Cr 32 Mo 18 N 50 (c1)Cr 25 Mo 25 N 50 (d1)Cr 18 Mo 32 N 50 (e1)MoN coatings deposited at room temperature after annealing processes

Fig4.22 Hardness and Young’s Modulus of (a2)CrN (b2)Cr32Mo18N50 (c2)Cr25Mo25N50

–  –  –

Fig4.23 Hardness and Young’s Modulus changes of (a)CrN (b)Cr 32 Mo 18 N 50 (c)Cr25Mo25N50 coatings deposited at 400°C after thermal processes

Fig4.24 Cross-sectional SEM images of multilayer CrN/MoN (m1) and (m2) coatings



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