CAM AND FOLLOWER WEAR OF IC ENGINES

RAJEEV G PMM12S010

CONTENTS

• INTRODUCTION

• WEAR MECHANISM

• MODES OF FAILURES

• MATERIALS USED

• CONCLUSION

• REFERENCES

INTRODUCTION

Fig. 1. cam and follower in IC engine valvesFig. 2. cam and follower mechanism

INTRODUCTION

Cam and follower are used in internal combustion engines to provide a specific prescribed motion to a valve train system.

The cam follower motion is complex. Motion of cam is transferred to the follower by direct

contact under conditions of• high temperature• lubrication• High contact stress

CAM AND FOLLOWER WEAR

EFFECT OF WEAR

• The valve lift duration during the cycle influences engine performance

• The intake of charge and exhaust of gases are controlled by respective valves

• Valve lift motion is controlled by cam and follower movement

• The wear process at the interface of cam and follower adversely affect the engine performance

FACTORS AFFECTING THE WEAR

• Materials used• Rotational speed• Dynamics of the camshaft – follower kinematic pair• Temperature & viscosity of lubricating oil• Operational conditions

Typical diagram of cam follower system

WEAR MECHANISMBreak down of lubrication leads to metal to metal

contact – adhesive wear

The cam follower pair is under rolling-sliding contact.

The wear caused by surface fatigue because of repetition of contact load

Sometimes the abrasive wear observed

MODES OF FAILURES

Typically 3 modes of failures are observed

1. Pitting (surface fatigue ) Breaking-out of small rough portions of material surfaces Severe wear occurs when it promote scuffing Surface initiated or sub- Surface initiated

Fig. 2. pitted follower surface

MODES OF FAILURES

2. Polish wear (abrasive wear ) This type of wear found in every contacting surfaces Visually mirror finish appearance Dimensional check quantifies wear

Fig. 3. polish wear surface under cyclic loading

MODES OF FAILURES

3. Scuffing (adhesive wear) Severe form of wear Break down of lubrication; high degree of relative motion Local welding of two heavy loaded surfaces Tearing apart of welded material Fig. 4. scuffed surface

SEVERITY OF WEAR

SEM micrograph of scuffed surface SEM micrograph of pitted surface

Scuffed surfaces are associated with white layer

Pitting may not affect running behaviour until it promote scuffing

MATERIALS USED

Cam shaft Cast iron is widely used for large volume

production - grey cast iron - chilled cast iron - nodular cast iron - malleable cast iron

Steels are used in small volume production

Chilled cast iron camshaft

Steel camshaft

MATERIALS USEDCam shaft

MATERIALS USED

Followers chilled cast iron is widely used

Table showing cam shaft and cam follower materials

HOW TO REDUCE WEAR?

Surface treatmentsPhosphating : dipping the component in a bath of

phosphoric acid and phosphate for 15 min. At 80-100

oC• The crystalline surface layer inhibits adhesive wear

www.phosphating.net SEM image of phosphated surface

HOW TO REDUCE WEAR?Ferrox process &oxidation : This process involves

the use of a porous structure mass called Ferrox ( iron oxide and binder) deposited on surface

Produces oxide coating by treating in steam at 300 – 600 oC

Coating resist adhesive wear

www.baileysonline.comSEM micrograph of ferrox surface coating

HOW TO REDUCE WEAR?

Tufftriding : a nitrocarburizing process accelerated by blowing in compressed air.

• A thin non-brittle carbon bearing FeN layer is formed which resist wear process

www.wallworkht.co.uk SEM micrograph of tufftrided surface

HOW TO REDUCE WEAR?

Induction and flame hardening • Increases the hardness of various Cast irons by inducing martensite

transformation at surface• Hard surface resist wearcarburizing • Applicable to low carbon steels• Diffused carbon increases the surface hardnessChromium coating & carbo-nitriding of cam follower• These coatings are against scuffing wearUpper surface remelting methodApplication of technical ceramics, composites, hard sintered

metals

SUMMARY

• Engine performance depends on cam and follower movement.

• Cam and follower surfaces which are in dynamic contact suffer from different types of wear

• Scuffing is the most deleterious wear process• Different cast irons and steel are used for

manufacturing of camshaft and followers• Several surface treatment methods are used for

improving wear resistance of cam and follower

REFERENCES

• T.S. Eyre , B. Crawley ,Camshaft and cam follower materials, Tribology international August 1980, 147-152

• Nagaraj Nayak, P.A. Lakshminarayanan, M.K. Gajendra Babu, A.D. Dani, Predictions of cam follower wear in diesel engines, Wear 260

(2006) 181–192• J. Michalski, J. Marszalek, K. Kubiak,An experimental study of diesel

engine cam and follower wear with particular reference to the properties of the materials, Wear 240 (2000),168–179