Microstructure and Mechanical Microstructure and Mechanical

Properties of Properties of

Hydrogenated WC-C NanocompositeHydrogenated WC-C Nanocomposite

S. J. Parka),b)

K.-R. Leea), D.-H. Kob), J. H. Hanc), K. Y. Eun a)

a) Thin Film Research Center, Korea Institute of Science and Technology

b) Department of Ceramic Engineering, Yonsei University

c) Korea Research Institute of Standard and Science

Applications of DLC FilmApplications of DLC Film

Thermal instability Thermal instability – degradation beyond 500°Cdegradation beyond 500°C

High residual compressive stressHigh residual compressive stress

– Max 10 GPaMax 10 GPa

Poor adhesion Poor adhesion – Steel, Oxide, Sulfide, etc.Steel, Oxide, Sulfide, etc.

Disadvantages of DLC FilmDisadvantages of DLC Film

Trends of Hard CoatingsTrends of Hard Coatings

Single layer filmsSingle layer filmsDiamond, DLC, CNx,

Nitride, Carbide etc.

Compound singleCompound single layer filmslayer films NanocompositesNanocomposites

Functionally Functionally gradient coatingsgradient coatings

Nano-multilayer films

S. Veprek et al., Surface Coat. Technol.

133-134 (2000) 152

A.A.Voevodin et al.,

Tribology International 29 (1996) 559

How to Overcome How to Overcome the Disadvantages of DLC Filmthe Disadvantages of DLC Film

TiC and WC nanograins embeded in DLC matrixTiC and WC nanograins embeded in DLC matrix

Transition metal carbide + DLCTransition metal carbide + DLC

Nanocrystalline/DLC nanocompositeNanocrystalline/DLC nanocomposite

The desirable combination of hardness, toughness, low The desirable combination of hardness, toughness, low

friction and wear in ambient environmentfriction and wear in ambient environment

A. A. Voevodin et al. Thin Solid Films, 342 (1999) 194

Purpose of the Present WorkPurpose of the Present Work

TThe he synthesis of WC-C nanocomposite thin film synthesis of WC-C nanocomposite thin film

using a hybrid DC magnetron sputtering with RF using a hybrid DC magnetron sputtering with RF

PACVD systemPACVD system

Relationship between the mechanical Relationship between the mechanical

properties and the microstructureproperties and the microstructure

Experimental ConditionsExperimental Conditions

Hybrid DC magnetron sputtering

CH4+ Ar (CH4/(Ar+CH4 ) : 0.33 – 0.58)

Deposition pressure : 1.33 Pa

Cathode target current : 300 mA

Substrate bias : -150 Vb RF biasing

Substrate : P-type (100) Si wafer

100 ㎛ Si wafer

for stress measurement

Roughing Pump

TMPMatching Box

RF13.56MHz

Gas

W Target

Substrate

W Concentration in the FilmW Concentration in the Film

Residual Stress of the FilmResidual Stress of the Film

W Sputtering at –150Vb

W Sputtering of Poisoned Target with Carbon PA-CVD with CH4

Hardness of Hardness of the Filmthe Film

W Sputtering at –150Vb

PA-CVD with CH4

W Sputtering of Poisoned Target with Carbon

XRD Spectrum of XRD Spectrum of the Filmthe Film

Diffraction Pattern of the FilmDiffraction Pattern of the Film

6. 9 at.% 26 at.%14.5 at.%

TEM Micrograph of TEM Micrograph of the Filmthe Film

• Diffraction Pattern • Plan-View Image

W : 6.9 at.%

40 nm

Resistivity of Resistivity of the Filmthe Film

G-Peak Position of G-Peak Position of the Filmthe Film

PA-CVD with CH4

W Sputtering of Poisoned Target with Carbon W Sputtering at –150Vb

Structural Change Structural Change with W Concentrationwith W Concentration

W : Below 13 at.% W : 13 - 15 at.% W : Beyond 15 at.%

DLC Matrix

c-WC Crystalline

Relationship between Structure and Relationship between Structure and Mechanical Properties Mechanical Properties

ConclusionsConclusions

Nanocomposite of WC phase and DLC matrix was produced by Nanocomposite of WC phase and DLC matrix was produced by the the addition of W into DLC films. The content of WC phase was addition of W into DLC films. The content of WC phase was proportional to the W concentration in the film.proportional to the W concentration in the film.

The mechanical properties of WC-C nanocomposite were closely The mechanical properties of WC-C nanocomposite were closely

related to the physical contact of WC nanocrystalsrelated to the physical contact of WC nanocrystals..

- Below 13 at.% of W, mechanical properties of WC-C film were determined by DLC matrix because WC nanocrystals were isolated.

- Beyond 13 at.% of W, WC nanocrystals began to contact. Hence, the mechanical properties of WC nanocrystals affected the mechanical properties of the nanocomposite film. Because the physical contact increased with increasing WC content, the hardness of the film increased.

Friction Coefficient of the FilmFriction Coefficient of the Film