Failure Analysis of GE-F9 Gas

Turbine Journal Bearings(Research Note)

Principle of Corrosion | Postgraduate Corrosion | 2011

Alfonsius B J Haslim

0806331355

Introduction: Jahromi, Goudarzi, & Nazarboland. (2008) [1]

Abstract– This paper presents a failure analysis of journal

bearings used in GE-F9 gas turbines. Detailed studies

including visual examination, optical microscopy, scanning

electron microscopy, XRD and oil analysis were performed to

determine the root causes of failure. Based on the results, it

was determined that fretting, sulfur attack and fatigue were

the main causes of failure.

Keywords– Journal bearing, bearing failure, fretting, sulfur

attack, fatigue.

Presentation Content’s

Introduction

Summary

Basic Theory

Study Case

Experimental & Discussion

BASIC THEORY

PART II

Fretting Corrosion

Fretting corrosion (a

corrosion phenomenon)

is a combined wear and

corrosion process in which

material is removed from

contacting surfaces. Occur

between two material

under load and is restricted

to very small amplitude

oscillations [2-4].http://corrosion.ksc.nasa.gov/i

mages/fret4.jpg

http://www.iahcsmm.org/Recertifica

tion/LessonPlans/images/CIS211pi

cs/exampleOfFrettingCorrosion.jpg

Recognizing Freeting Corrosion

Figure – Weight loss of mild steel

versus mild steel by freeting corrosion

[5].

Figure – Schematic of the fretting

process (form local surface dislocation

and deep pits) [3].

Example [3]

Prevention Fretting Corrosion [3-4]

1. Use of Lubricants, Surface

Treatments (Phospating), & Coating.

2. Increase the hardness of surfaces.

3. Decrease bearing loads on mating

surfaces.

4. Use of barriers to limit ingress of a

corrosive environment to mating

surfaces.

5. Restricting the degree of movement.

6. Selecting materials and combinations

that are less susceptible to fretting

corrosion (Table 4).

Sulfur Attack (Sulfidation)

Sulfidation is a reaction of a

metal or alloy with some form

of sulfur to produce a sulfur

compound that forms on or

under the surface of a metal or

a alloy [6].

Sulfur is one of the most common corrosive

contaminants in high temperature (2100 to

2200 F in excess air) industrial environment.

When combustion takes place with excess

air to ensure complete combustion of fuel

for generating heat in many industrial

processes, sulfur in the fuel reacts with

oxygen to form SO2 and SO3 [7-9].•Reducing Environment:

H2S

•Oxidizing

Environments: SO2

(Much Less Corrosive)

Some Application of Sulfidation

1. Calcining of mineral and chemical

feedstock [10].

2. Petrochemical Processing [11].

3. Fossil-fired boilers [11].

4. Petroleum Refining [12].

5. Coal Gasification [13-14].

6. Waste Incineration [15-16].

7. Fluidized-bed coal combustion [17-19].

http://newsimg.bbc.co.uk/media/images/4

1230000/gif/_41230096_mass_burn_inf4

16.gif

http://www.lawrencepumps.com/imag

es/PetroleumRefining.jpg

Some Cases

(Sulfidation) [7]

STUDY CASE

PART III

Journal and Bearing [1]

Failure analysis of GE-F9 gas turbine bearings having dimensional

characteristics given in Table 1 was the objective of this investigation. Therefore, in

the present case, samples of failed bimetal journal bearing were subjected to

detailed metallurgical investigations. Depending on environment temperature

(winter and summer) and cooling condition, the temperature of the lubricating

oil was between 70 to 90 °C.

Visual Examination [1]

Fretting

a) Damaged (Darkened regions). b) normal wear

EXPERIMENTAL &

DISCUSSION

PART IV

Chemical Composition of the bearing alloy [1]

Atomic adsorption Spectrometer

(http://elchem.kaist.ac.kr/vt/chem

ed/spec/atomic/graphics/aa.jpg)

Corresponds to ASTM B-23-

alloy 2.

Optical Microscopy and hardness measurements [1]

Matrix: 25.2 Cuboids: 77.2 Needles: 89.3

Microhardness Hv Results:

Scanning electron Microscope and XRD [1]

Containing Cu2S

The sulfide was formed by the action of sulfur acids in the lubricating oil on the

copper in the bearing material. The decomposition of sulfur compounds in the

lubricating oil usually occurs when moisture is present in the oil and when the

operating temperature is high and exceeds a normal condition. In the present

case, the frictional heat due to the oscillation of the bearing in the housing

bore has stimulated a sulfur attack.

Scanning electron Microscope and XRD [1]

Scanning electron Microscope and XRD [1]

Additives are chemical agents added to lubricating oil to improve oil

properties. Oxidation inhibitors (phenolics and dithiophosphate)

and rust inhibitors (organic acids and sodium petroleum

sulfonate) are among the additives which are extensively used in

gas turbine lubricating oil. In contrast to phenolics and organic acids,

dithiophosphate and sodium petroleum sulfonate include sulfur.

It is clear that a sulfur attack can be prevented by using sulfur-

free additives.

Oil Evaluation [1]

The results shown in Table 3 indicate that there was no problem

with the oil in the normal operating condition. The result values

have been compared with the recommended values mentioned

in the manufacturer’s instructions.

SUMMARY

PART V

Summary

Reference

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Note” Failure analysis of GE-F9 Gas Turbine Journal Bearings. Iranian

Journal of Science & Technology, Transaction B, Engineering. Vol. 32,

no. 81, pp. 61-66.

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Reference

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Reference

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