엔진부품을 위한 카본계 내마모 윤활코팅 2006. 5. 30. kist- 현대자동차 협력...

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

a-C:H ta-C

2-D Analogy of Structure

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 (cm) >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 0.2 0.4 0.6 0.8 1.0( 상대비교치 )

Against steel ball, 50% RH, RT(Source : Nanotech Co. Ltd)

Applications of DLC

VCR Head Drum

CD/DVD Mold

Spacer Tool

Form Die

Hard Disk & Slider

Digital VCR Tape

Razor Blade

Wrist Pin

Applications of DLC

CarbofilmTM by Sorin Biomedica, Inc.

Deposition Methods

Energy

Ion Source

Cold SubstrateIm

pact

Ene

rgy

(eV

)1

10

100

1000

Amorphous Carbon

(sp2)

DenseCarbon

CarbonSource

HydrocarbonSource

DenseHydro-Carbon

PolymerLike

Carbon

PlasmaPolymers

PACVDPACVD

Ion Energy Distribution

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.

0

100

200

300

400

1970 1975 1980 1985 1990 1995 2000 2005

Year

Nm Diesel

Petrol

(Source : Dr. Strondl @ Hauzer)

Momentum development for typical 2 liter Petrol and Diesel engines over 35 years.

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

(Source : Dr. Strondl @ Hauzer, 2005)

camshafttappets

valves

piston

piston rings

crankshaft

Carbon based Nitride based

Me-C:H a-C:H Me a-C a-C CrN TiN

Production method

PVD/PACVD PACVD PVD PVD PVD PVD

Hardness (HV 0.05)

800-2200 1500-3500 1500-2500 2000-7000 2000-2200 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 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

+++ ++ - - +++ +++

Available Coatings at Present

(Source : ICMCTF 2005 / 2006)

(Source : Dr. Strondl @ Hauzer, 2005)

Coating Technology for Automobile Engines

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 applicationfor minimum wear and power consumption

Nanocomposite / Multilayer

CrC/W-DLC Multilayer (Hauzer)W-DLC by Hybrid Ion Plating (KIST)

5nm

5nm

Part: Diesel fuel injector and plungerCoating: a-C:H, W-C:H with metallic bufferCoating thickness >1 μmBenefit Wear resistance, preventing seizure

Figure from Robert Bosch GmbH

Fuel Injection System

2000~3000bar

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

Unit Injection System (1.9TDI)

Valve Train

Tappets Rocker Arm + Hydraulic Element

Coating CrN, a-C:H:W/Cr Si-DLC/SiThickness 2 – 6 µmCoating on Top side

Benefit Wear + friction

Coating Endurance+

ReleaseThickness 1 – 5 µmCoating 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 ( = 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

(Source : Dr. Strondl @ Hauzer, 2005)

Coating Technology for Automobile Engines

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

VCR Head Drum

CD/DVD Mold

Spacer Tool

Form Die

Hard Disk & Slider

Digital VCR Tape

Razor Blade

Wrist Pin

Technology Transfer to Industry

J&L Tech Co. Ltd

Daewoo Electronics Co.

Required Properties of Top Ring

– Anti-scuffing– Wear Resistance– Low Friction Coefficient– Chemical Stability– Self Lubrication– Low Cost

Application to Top Ring

Schematics of Diesel Engine

Deposition Method

• 250KHz PACVD using CH4 at 200 mTorr• Cylinder Coating Technology

(analogy to VCR Head Drums)• Buffer Layer Design for Optimum Adhesion

~10m Thick Films~10m Thick Films

Reciprocal Tribometer (Plint 77)

sliding directionpiston ring

cylinder liner(boron cast iron)

Anti-scuffing Property of Piston Rings

Cr WS2-1 WA2-2 GN PVD DLC0

50

100

150

200

250T

ime

to

fa

ilure

(ho

ur)

Test condition :load :200N, marginal lub. condition

Wear Test under Dry Lubrication Conditions

0 5000 10000 15000

0.2

0.3

0.4

0.5

DLC coated Ring

Hard Cr Ring

No-lubricant conditionLoad 50N

Fric

tion

Coe

ffic

ient

Number of Cycle.

Hard Cr Coated Ring DLC coated Ring

Before Test Before Test

After Test After test

Result of Dynamo Test (900h)

Before Test Before Test

After Test After Test

100m6.5m

5.3m

Hard Cr Coated Piston Ring

DLC/Cr Coated Piston Ring

Issues in Carbon Base Coatings

• Adhesion– In most cases, film adhesion is more important than th

e 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