Contents Brief Introduction to Diamondlike Carbon Coatings Applications

Contents • Brief Introduction to Diamond-like Carbon Coatings • Applications of DLC to Automobile Parts • DLC Research at KIST

What is DLC ? • Amorphous Solid Carbon Film • Mixture of sp 1, sp 2 and sp 3 Hybridized Bonds • High Content of Hydrogen (20 -60%) • Synonyms – – Diamond-like Carbon (Hydrogenated) amorphous carbon (a-C: H) i-Carbon Tetrahedral Amorphous Carbon Heart valve Hard disk

Bond Structure of Carbon 1 S 2 2 S 22 P 2

2 -D Analogy of Structure a-C: H ta-C

Properties of Solid Carbon Property Diamond DLC Graphite Density (g/cm 3) 3. 51 1. 8 – 3. 6 2. 26 Atomic Number Density (Mole/cm 3) 0. 3 0. 2 – 0. 3 0. 2 Hardness (Kgf/mm 2) 10000 2000 - 8000 500 Friction Coeff. 0. 05 0. 03 – 0. 2 0. 1 Refractive Index 2. 42 1. 8 – 2. 6 2. 15 – 1. 8 Transparency UV-VIS-IR Opaque Resistivity (Wcm) >1016 1010 - 1013 0. 2 – 0. 4

경질코팅층의 내마모 윤활특성 마찰계수. 마모도 DLC WC Ti. N Cr. N Ti. CN 2. 0 1. 6 1. 2 0. 8 0. 4 (상대비교치) 0. 2 0. 4 0. 6 0. 8 1. 0 Against steel ball, 50% RH, RT (Source : Nanotech Co. Ltd)

Applications of DLC CD/DVD Mold Form Die VCR Head Drum Spacer Tool Hard Disk & Slider Wrist Pin Digital VCR Tape Razor Blade

Applications of DLC Carbofilm. TM by Sorin Biomedica, Inc.

Deposition Methods 1000 Energy Cold Substrate Impact Energy (e. V) Ion Source 100 Dense Carbon Polymer Like Carbon 10 1 Dense Hydro. Carbon Amorphous Carbon (sp 2) Carbon Source Plasma Polymers Hydrocarbon Source

Ion Energy Distribution PACVD

Examples of the Deposition Method

Development of Diesel Engines • Diesel engines are designed with continuously increasing power densities since the introduction of HP-fuel injection systems (1993). • Power and torque of diesel engines increased at a much higher rate than gasoline engines. • Meet environmental laws and cost reduction requirements. Momentum development for typical 2 liter Petrol and Diesel engines over 35 years. (Source : Dr. Strondl @ Hauzer)

Driving Force : Economy and Environment • Reduction of Energy Consumption – Reduction of friction • Reduction of Emission – Higher pressure fuel injection – Predictable wear of piston ring • Cost Reduction – Reduction of parts number e. g. sliding bearing instead of needle bearing coated piston pin coated tappet • Wear Protection – Higher load per surface area

Friction Loss in Engine camshaft tappets valves piston rings crankshaft (Source : Dr. Strondl @ Hauzer, 2005)

Available Coatings at Present Carbon based Nitride based Me-C: H a-C: H Me a-C Cr. N Ti. N Production method PVD/PACVD PVD PVD Hardness (HV 0. 05) 800 -2200 1500 -3500 1500 -2500 2000 -7000 2000 -2200 Friction coefficient 0. 1 -0. 2 0. 02 -0. 1 0. 05 -0. 1 0. 02 -0. 1 0. 4 0. 7 Internal stress (GPa) 0. 1 -1. 5 1 -3 2 -6 0. 1 -1 0. 5 -2 Thickness (µm) 1 -10 1 -3 1 -5 1 -3 1 -40 1 -8 Practical problems +++ ++ Process stability + +++ Industrial experience +++ ++ - - +++ (Source : ICMCTF 2005 / 2006)

Coating Technology for Automobile Engines (Source : Dr. Strondl @ Hauzer, 2005)

Penetration Fraction of PVD (2006) • Diesel Pump 100% since 1994 • Crankshaft Bearing 100% since 1987 • Piston Ring 10% since 1993 • Valve train (Tappet) 2% since 2001 • Piston Pin 1% since 2002 • Gear < 1% since 2000

Demands in Automobile Applications • Low wear of Coated Part – Suppress abrasive wear – Suppress adhesive wear – Suppress fatigue wear • Low Wear on Counterpart • Low Coefficient of Friction Composition Multilayer structure Microstructure Optimized to the application for minimum wear and power consumption

Nanocomposite / Multilayer 5 nm W-DLC by Hybrid Ion Plating (KIST) Cr. C/W-DLC Multilayer (Hauzer)

Fuel Injection System Part: Coating thickness Benefit Diesel fuel injector and plunger a-C: H, W-C: H with metallic buffer >1 μm Wear resistance, preventing seizure 2000~3000 bar Figure from Robert Bosch Gmb. H

Unit Injection System (1. 9 TDI) Technical Data Engine power: 96 KW (130 PS) Injection pressure: 2050 bar Pressure power: 14. 000 N Advantages • Increased efficiency (lower friction) • Increased engine torque • Reduce energy consumption • Reduction of the CO 2 -emission Source: Volkswagen AG, Wolfsburg

Valve Train Tappets Coating Thickness Coating on Benefit Rocker Arm + Hydraulic Element Cr. N, a-C: H: W/Cr Si-DLC/Si 2 – 6 µm Top side Coating Wear + friction Benefit Thickness Coating on Endurance+ Release 1 – 5 µm Head hydraulic element Rockerarm (racing) Wear (Source : Dr. Strondl @ Hauzer)

Piston Ring - Sliding contact - Abrasive wear (also liner to be protected) - Temperature load Coating 200 µm hard Cr (galvanic) 30 -40 µm Cr. N (PVD Arc) ~10 µm DLC (PACVD) / Me-DLC (PVD) (Source : KIST & DHI 1996)

DLC Application by Nissan 日産自動車，水素フリーDLCコーティングによ る摩擦低減技術を開発 日經 BP 2006/03/15 21: 15 Compatibility with special lubricant of different additives (m = 0. 07) 연말 실용화 목표

Gears Full oil film lubrication DLC has not shown a beneficial influence. Boundary lubrication (stopping/starting, severe load, temporary loss of lubricant) DLC coatings can significantly reduce wear. Maximum load carrying capacity of gears can be increased by 10 -40%. Coated spur gear

Door Lock to reduce noise

Coating Technology for Automobile Engines (Source : Dr. Strondl @ Hauzer, 2005)

DLC Research @ KIST • Synthesis and Application of DLC Films – – – Control of structure and properties of DLC films Modification of DLC films by third element addition Nanoscale structure manipulation for novel functions Tribo-chemical Aspect of DLC Films Mechanical Properties of Thin DLC Films Application technologies • Adhesion improvement • Coating layer optimization • Production process development http: //diamond. kist. re. kr/DLC

Applications of DLC CD/DVD Mold Form Die VCR Head Drum Spacer Tool Hard Disk & Slider Wrist Pin Digital VCR Tape Razor Blade

Technology Transfer to Industry J&L Tech Co. Ltd Daewoo Electronics Co.

Application to Top Ring Required Properties of Top Ring – – – Schematics of Diesel Engine Anti-scuffing Wear Resistance Low Friction Coefficient Chemical Stability Self Lubrication Low Cost

Deposition Method • 250 KHz PACVD using CH 4 at 200 m. Torr • Cylinder Coating Technology (analogy to VCR Head Drums) • Buffer Layer Design for Optimum Adhesion ~10 mm Thick Films

Reciprocal Tribometer (Plint 77) sliding direction cylinder liner (boron cast iron) piston ring

Anti-scuffing Property of Piston Rings Test condition : load : 200 N, marginal lub. condition 250 Time to failure(hour) 200 150 100 50 0 Cr WS 2 -1 WA 2 -2 GN PVD DLC

Wear Test under Dry Lubrication Conditions

Result of Dynamo Test (900 h) Hard Cr Coated Ring DLC coated Ring Before Test After test

Hard Cr Coated Piston Ring DLC/Cr Coated Piston Ring 6. 5 mm 100 mm Before Test 5. 3 mm After Test

Issues in Carbon Base Coatings • Adhesion – In most cases, film adhesion is more important than the mechanical properties. • Environmental Effects – Compatibility with new lubricants – Adhesion degradation in aqueous environment • Tribochemical Reaction for Fundamentals – In-situ observation of the contact surfaces – Third element effect – Multilayer effect • Market Penetration – Based on the advanced technology