case study of failure analysis s2

Technical Report

Failure Analysis of

Shaft Com Gear Shift

By Integrated Master Student Team

BangkitIndriyana (1106154274)

M. Ekaditya Albar (1106154305)

RhidiyanWaroko (0806331935)

StefannoWidyYunior (0806332004)

YudiPrasetyo (0806455950)

Department of Metallurgy and Materials EngineeringUniversity of Indonesia

October2012

Technical Report

Failure Analysis of









October2012

Technical Report

Failure Analysis of









October2012

Failure Analysis Assignment

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1. Background

Component of a motorcycle that is "Gear Shift Shaft Com" produced by PT. Y

which acts as a supplier of automotive components for PT. ISI has been damaged during

use. Observations indicated that the damage occurred in the weld joint where the welds are

not fused between the plates with the shaft. This causes the transmissioncannot move the

gearshift from position 1 to position 2, 3 and 4. The next component is submitted to the

Department of Metallurgy and Materials UI to analyze the cause of the damage these

components.

2. Fish Bone Diagram (Root Cause Analysis)

The fish bone diagram is perform during the performance of the analysis work in

order to get more acquaint of the specimen to be tested. The interim results of the fish bone

diagram as shown below:

Manufacture is a critical phase which has important roles for the quality of Gear

Shift Shaft Com, in this case, assembly process, material has been chosen, operating

condition of the sample (the environment during the performance of the sample), and the

maintenance are properly done by the operator and the user. So, the analysis is going to be

focused on manufacturing phase.


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1. Background







components.











2

1. Background







components.











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It is obvious that the failure occur in the weld area, this fact endorsed the probability

that the failure root cause ascribeto the welding process. The other processes during the

performance of the manufacturing process widely open to be envisaged in this analysis. The

welding root cause fish bone diagram as shown below:

There are five possible processes which can leads to the failure of the component. To

ascertain and provision the cause of the failure of the component, a number of investigations

is perform in order to get data (or information) and acquaint to the problem.

3. Scope of Investigation

The scope of the testing performed to investigate the sample "Gear Shift Shaft Com"

produced by PT. Y is as follows:

Visual examination

Chemical composition using OES

Hardness testing

Metallography testing (macrostructure and microstructure)

Fractographyexamination using Scanning Electron Microscope (SEM)

Micro chemical composition test by EDS


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Visual examination


Hardness testing





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Visual examination


Hardness testing





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4. Examinations

4.1. Visual Examination

Figure 1. Sample Shaft Com Gear Shift as received

Figure 2. Sample Failed Shaft Com Gear Shift as received

4.2. Chemical Composition by OES

Gear Shift Shaft Com was subjected to chemical composition test using Optical Emission

Spectrometer (OES). Table 1 shows the chemical composition test result of samples.

Table 1.Chemical composition results on as received components

Material C(%)

Si(%)

Mn(%)

S(%)

P(%)

Cr(%)

Ni(%)

V(%)

Mo(%)

Cu(%)

Al(%)

AISI1045M(S45C)

0.42-0.48

0.15-0.35 0.6-0.9 0.035

max 0.03 - - - - - -

SHAFT 0.50 0.197 0.661 0.010 0.015 0.067 0.057 0.001 0.025 0.134 0.006

SPCC 0.12max -- 0.5 max 0.045

max0.04max -- -- -- -- -- --

PLATE 0.10 0.009 0.348 0.013 0.005 0.023 0.020 0.001 0.005 0.044 0.045


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4. Examinations








Material C(%)

Si(%)

Mn(%)

S(%)

P(%)

Cr(%)

Ni(%)

V(%)

Mo(%)

Cu(%)

Al(%)

AISI1045M(S45C)

0.42-0.48

0.15-0.35 0.6-0.9 0.035

max 0.03 - - - - - -

SHAFT 0.50 0.197 0.661 0.010 0.015 0.067 0.057 0.001 0.025 0.134 0.006

SPCC 0.12max -- 0.5 max 0.045

max0.04max -- -- -- -- -- --

PLATE 0.10 0.009 0.348 0.013 0.005 0.023 0.020 0.001 0.005 0.044 0.045


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4. Examinations








Material C(%)

Si(%)

Mn(%)

S(%)

P(%)

Cr(%)

Ni(%)

V(%)

Mo(%)

Cu(%)

Al(%)

AISI1045M(S45C)

0.42-0.48

0.15-0.35 0.6-0.9 0.035

max 0.03 - - - - - -

SHAFT 0.50 0.197 0.661 0.010 0.015 0.067 0.057 0.001 0.025 0.134 0.006

SPCC 0.12max -- 0.5 max 0.045

max0.04max -- -- -- -- -- --

PLATE 0.10 0.009 0.348 0.013 0.005 0.023 0.020 0.001 0.005 0.044 0.045


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Based on the test result, the chemical composition of shaft sample is close to AISI 1045M

(S45C) and the chemical composition of plate sample is closed to SPCC.

4.3. Hardness Testing

Hardness testing was conducted by Vickers micro-hardness. It is found that the hardness of

weld area, HAZ, and fusion line respectively 367 HV, 396 HV, 689 HV. The hardness of

base metal for plate material is 166 HV and for shaft material 243 HV.

Table 2.Hardness testing results on welding components

Location Location Hardness ofSample 1 (HV)

1. Base Metal 1 1662. Plate surface 6133. Base Metal 2 2434. Weld Metal 3675. Fusion Line 6896. HAZ 396

Figure 3.Scheme of hardness testing on welding components


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4.4. Metallography Testing

4.4.1. Macrostructure

Figure 4. Macroscopic of shaft com gear shift (good sample), magnification 7X, 2% nital etch

Figure 5. Macroscopic of shaft com gear shift on the left side (good sample), magnification 10X, 2% nital etch

Figure 6. Macroscopic of shaft com gear shift on the right side (good sample), magnification 10X,

2% nital etch


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Figure 7. Macroscopic of failedshaft com gear shift (rejected), magnification 10X, 2% nital etch

Figure 4 shows proper penetration of the good sample with the presence of huge porosity

(left weld-Fig. 5). Figure 6 shows a good weld joint area without any evidence of defects.

Fig.7 shows the weld penetration is not good on the shaft and plate material. Fig. 7 also

indicated that the weld design use a gap that serves as ventilate of the gas of zinc produced

by welding process.

4.4.2. Microstructure

Figure 8.The microstructure of base metal plate.Nital etch


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Figure 9.The microstructure of base metal shaft.Nital etch

Figure 10.The microstructure of carbonitided plate surface.Nital etch

Figure 11.The microstructure of weld metal.Nital etch


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Figure 12. The microstructure of HAZ, Nital etch

Figure 13. The microstructure of fusion line, Nital etch

Figure 14. Macrostructure of failed shaft com gear shift, magnification 10X, 2% nital etch

The microstructure of base metal of the plate sample shows typical of ferrite-pearlite

structures (Figure 8). The diffusion of carbon is occurs due to the different level of

concentration of carbon in shaft sample. It is obvious that during the performance of the

welding process, the carbon concentration on the surface of the shaft is higher than the inner


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area of the shaft. Bainite structure in HAZ area (Figure 12) and bainite structure in weld area

(Figure 11)are imposed by the observation. The hardness of weld area and HAZ are

approximately 367 and 396 HV, which indicated the range of hardness of bainite

structure.There is no indication of thepresence of micro-inclusions at grain boundaries and

defects in microstructure. Figure 10 and 13 indicates the formation of nitrides and carbide in

the fusion line. These phasesare produced by carbonitrided process during manufacture of

the plate and ascertained by the hardness of the area, approximately 689 HV(see table 2),

that value of hardness tend to be large and is brittle.

4.5. FractographyExamination using Scanning Electron Microscope (SEM)

Figure 15. SEM image in weld area (good sample) with Quadrant Back Scattering Detector (QBSD), 45X


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Figure 16. SEM image in weld area (good sample) with Secondary Electron Detector (SE1), 80X



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The figure 15, 16, 17, and 18 are show that the specimen contains porosity in the weld area.

The gap between the specimen is prepared to allows the gas resulted by vaporization zinc to

out from the weld. The porosity, spread uniformly in the welding area. This causesthe

mechanical properties of the material decreases significantlyand failure occurs during utilize

the material. Figure 19 shows porosity at higher magnification.


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4.6. Micro chemical composition test by EDS

Table 3.EDS results on welding components

Element Element %C 1.71O 41.62Si 0.47Cl 2.20Ca 0.23Ti 0.95Fe 27.66Zn 25.16

5. Results and Discussions

Galvanized steel is widely used for car bodies due to its corrosion resistance.

However, it is associated with serious problems related to the welds quality when welding is

applied as a process to a joint without gaps. In the plate used for gear shaft com, material is

galvanized. It may cause defects in weld area. Zn has higher vapor pressure than Fe, the

higher value of vapor pressure of Zn are tend to have contributed to the explosion. The

problem of welding continued-zinc coated products lies in the different of vaporization and

melting point of Zn compared to steel. Arc can be contaminated by zinc in its vapor state,

results in an unstable and erratic arc and produced a few of porosity in the weld bead,

because zinc in its vaporized state cannot escape or trapped in the weld area.The pores

resulting from the aforementioned processinfluence the mechanical characteristics, leading to

defectivewelds. Accordingly, they should be prevented in advance.Zn also have poor

weldability, highly reactive, easy to form intermetallic compounds at temperatures close to

the melting temperature of zinc brittle.The presence of zinc is indicated in EDX (Table 3).

Figure. ????


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Figure. ????


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Figure. ????


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Figure 20. Fillet weld or lapped joint of continued-zinc product

Figure21. Vapor pressure of several metals as a function of temperature

The test result shows the presence of carbide hardness in fusion line, with hardness

approximately 689 HV. The fusion line contained nitride and carbide phasethat cause high

hardness and brittle materials. This causes the material have high sensitivity to crack.The

carbon equivalents of each parent material are:

CE =% C + (% Mn / 6) + Si/24 + Cr / 5 + Mo / 4 + Ni/15


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CE Shaft : 0.5 + 0.11 + 0,008 + 0.0134 + 0.00625 + 0.0038 = 0.64

CE Plate : 0.1 + 0,058 + 0.000375 + 0.0046 + 0.00125 + 0.00133 = 0.16

Value of Carbon Equivalent (CE) shaft material is quite high, it is above 0.35, it is required

to do an additional treatment in areas other than the plate, the treatment such as preheats,

interpass temperature and post heat treatment to release stress and prevent cracking due to

welding. All heat treatment must do at temperature under melting point of Zn.

6. Conclusion and Recommendation

Zn vapor trapped in the area of weld metal makes the porosity in the weld metal, coupled

with the phase carbida and brittle nitrides at the fusion line area, making a broken component

on the connection between shaft and plate. When the product receives load, the connection

between the shaft and the plate contained porosity and brittle phase in, will instantly broken.

The recommendations we conduct in this case are:

Galvanizing steel should have special surface preparation, such as grinding the area

subjected to be welded to remove the zinc layer on the surface, that is because of melting

point of Zn is far lower than Fe. Zinc vaporizes at 902oC. So, when Fe in melt state, Zn in

vapor state. Zn vapor can contaminate the molten metal. That condition can make a few

of porosity in weld metal because of Zn in vapor state cannot escape.

To avoid the porosity and leak of penetration of the material, the laser-arc hybrid welding

process can be applied. The combination of laser welding power and arc welding power

simultaneously to compose a single weld, utilizing the advantages of both methods. This

process allows preheat and post heat treatments on the welds through the arrangement of

the laser and arc.


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Use special filler offor weld the galvanized component, such astitanium or any other filler

which needs low weld energy.

Do preheat before weld the materials. The relationship between carbon equivalent and

preheat and interpass temperatures are recommended is shown in Table 4.All heat

treatment must do at temperature under melting point of Zn. Because of carbon

equivalent in shaft 0.64, preheat and interpass temperature should do between 250-300oC

in areas other than the plate.

Table 4. The relationship between carbon equivalent and preheat and interpass temperatures are recommended

The price comparisons of the recommendation given above are as shown in Tabel 5.

Table 5.list of material which can remove abrasively carbonitrided, with hardness value and the price

Material Hardness Value (Hv) Price (USD) / kg powder

Carbon Boron Nitride 6000 200 – 2000

Boron Carbide 3700 10 – 50

Titanium Carbide 3200 10 – 60

Vanadium Carbide 2800 60 – 65

Tungsten Carbide 2400 35 – 80

Chromium Carbide 1400 10 – 40

Boron Carbide is very recommended because the price as cheap as chromium carbide but

boron carbide has more hardness value than chromium carbide, so the longer times it takes to

wear boron carbide than to wear chromium carbide. Then, The powder form of boron nitride


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can be fabricated by casting to become a wheel, like figure 23 below. In market, price of a

wheel is about USD 100 - 500.

Figure 23. Super abrasive wheel


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7. References

Sperko Engineering Services, Inc. 1999. Welding Galvanized Steel – Safely.

http://www.nakedwhiz.com/weldinggalvanized.pdf.Accessedseptember 25 2012, 11.14

WIB.

http://www.slbgroup.com/pdf/balltinfotech/thrustballtech.pdf.Accessed September 25th

2012, 12.01 WIB.

JIS S45C composition. http://www.meadinfo.org/2010/03/s45c-jis-mechanical-

properties.html. Accessed September 25th 2012, 11.30 WIB.

Welding Handbook. 2009. Kobe Steel, Ltd.

http://www.kobelcowelding.com/20100119/handbook2009.pdf. Accessed September

16th 2012, 15.30 WIB.

Cheolhee Kim, Woongyong Choi, Jeonghan Kim, and Sehun Rhee. 2008. Relationship

between the Weldability and the Process Parameters for Laser-TIG Hybrid Welding of

Galvanized Steel Sheets.Materials Transactions, Vol. 49, No. 1 (2008) pp. 179 to 186.

M. Pouranvari. 2011. Analysis of Fracture Mode of Galvanized Low Carbon Steel

Resistance Spot Welds. International Journal of Multidisciplinary sciences and

engineering, vol.2, No.6, September 2011.

HongpingGu and Boris Shulkin. Remote laser welding of zinc-coated sheet metal;

component in a lap configuration utilizing humping effect. Stronach Centre for

Innovation, Magna International Inc. Aurora, Ontario, L4G 7G6, Canada.

http://astralloy.infomedia.net/pdf/plate_outwear.pdf. Accessed October 6th 2012, 23.00

WIB.

http://www.3m.com/product/information/Superabrasive-Wheels.html. Accessed October

7th 2012, 00.11 WIB.

http://www.alibaba.com.

case study of failure analysis s2

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