2006. 5. 30. KIST-현대자동차 협력 포럼 KIST 미래기술연구본부 이 광 렬 엔진부품을 위한 카본계 내마모 윤활코팅 2006. 5. 30. KIST-현대자동차 협력 포럼 KIST 미래기술연구본부 이 광 렬

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 sp1, sp2 and sp3 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 1S2 2S22P2

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

Properties of Solid Carbon Property Diamond DLC Graphite Density (g/cm3) 3.51 1.8 – 3.6 2.26 Atomic Number Density (Mole/cm3) 0.3 0.2 – 0.3 0.2 Hardness (Kgf/mm2) 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 VIS-IR Opaque Resistivity (Wcm) >1016 1010 - 1013 0.2 – 0.4

경질코팅층의 내마모 윤활특성 DLC WC TiN CrN TiCN 마모도 마찰계수. 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 Razor Blade Hard Disk & Slider Digital VCR Tape Wrist Pin

CarbofilmTM by Sorin Biomedica, Inc. Applications of DLC CarbofilmTM by Sorin Biomedica, Inc.

Deposition Methods Ion Source Energy Cold Substrate Impact Energy (eV) 1 10 100 1000 Amorphous Carbon (sp2) Dense Source Hydrocarbon Hydro- Polymer Like Plasma Polymers Ion Source Energy Cold Substrate

Ion Energy Distribution PACVD

Examples of the Deposition Method 다음은 Si 함유 DLC 필름을 증착하는데 사용한 장비의 간략한 모식도와 증착조건 입니다. 13.56 MHz를 사용한 R.F PACVD법을 사용하였고 Source Gas로는 벤젠과 수소로 희석된 Silane개스를 혼합하여 사용하였습니다. 증착압력은 10mtorr로 하였고, 바이어스 volatage는 -400V를 가하였습니다. 필름내 Si의 함량을 조절하기 위하여 혼합개스 내의 Silane개스의 함량을 0에서 90%로 변화시켜 가면 증착을 하였습니다. 기판은 Si(100)웨이퍼를 사용하였고, 필름의 두께는 1 micro meter로 증착하였습니다. Si함량에 따른 마찰거동을 조사하기 위하여, Si이 포함되지 않은 순수한 DLC 필름과 Si이 0.5, 2, 9.5 at.% 함유된 DLC 필름을 제작하였습니다.

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 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 a-C CrN TiN Production method PVD/PACVD PACVD 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 0.4 0.7 Internal stress (GPa) 0.1-1.5 1-3 2-6 0.1-1 0.5-2 Thickness (µm) 1-10 1-5 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 5nm 5nm W-DLC by Hybrid Ion Plating (KIST) CrC/W-DLC Multilayer (Hauzer)

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

Unit Injection System (1.9TDI) 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 CO2-emission Source: Volkswagen AG, Wolfsburg

Rocker Arm + Hydraulic Element Valve Train Tappets Rocker Arm + Hydraulic Element Coating CrN, a-C:H:W/Cr Si-DLC/Si Thickness 2 – 6 µm Coating on Top side Benefit Wear + friction Coating Endurance+ Release Thickness 1 – 5 µm Coating on Head hydraulic element Rockerarm (racing) Benefit 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 CrN (PVD Arc) ~10 µm DLC (PACVD) / Me-DLC (PVD) (Source : KIST & DHI 1996)

DLC Application by Nissan 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 Razor Blade Hard Disk & Slider Digital VCR Tape Wrist Pin

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

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

~10mm Thick Films Deposition Method 250KHz PACVD using CH4 at 200 mTorr Cylinder Coating Technology (analogy to VCR Head Drums) Buffer Layer Design for Optimum Adhesion ~10mm Thick Films

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

Anti-scuffing Property of Piston Rings Test condition : load :200N, marginal lub. condition 250 200 150 Time to failure(hour) 100 50 Cr WS2-1 WA2-2 GN PVD DLC

Wear Test under Dry Lubrication Conditions

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

Hard Cr Coated Piston Ring DLC/Cr Coated Piston Ring Before Test 6.5mm 100mm Before Test Before Test 5.3mm After Test 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