Text

Metallurgical Evaluation of Diesel Generator Turbocharger Guide Vane Holddown Bolts at Grand Gulf Nuclear Station - Unit 1
	ML20093H560
Person / Time
Site:	Grand Gulf
Issue date:	07/31/1984
From:	Brihmadesam J; MIDDLE SOUTH SERVICE, INC.
To:	;
Shared Package
ML20093H535	List: AECM-84-0373, Forwards Response to NRC 840717 Request for Addl Info Re Tdi Engine Insp.Augmented Maint/Surveillance Program (Table A-1) Supersedes All Previous Commitments for Augmented Program Requirements; ML20093H560; ML20093H572;
References
	NUDOCS 8407250192
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. Attachment 2 to

, AECM-84/0373 METALLURGICAL EVALUATION OF DIESEL GENERATOR TURBOCHARGER GUIDE VANE HOLD DOWN BOLTS AT GRAND GULF NUCLEAR STATION - UNIT 1 PREPARED FOR: NUCLEAR PLANT ENGINEERING MISSISSIPPI POWER & LIGHT COMPANY PORT GIBSON, MISSISSIPPI 39150 PREPARED BY: J. S. BRIHMADESAM NUCLEAR ENGINEERING DEPARTMENT

.a MIDDLE SOUTH SERVICE, INC.

NEW ORLEANS, LOUISIANA 70112 JULY, 1984 8407250192 840720 PDR ADOCK 05000416 G PDR I_ _ . _ _ _ _ . _ _ . _ _ _

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TABLE OF CONTENTS Section Py LIST.0F FIGURES. .. . . .. .............. iii

1.0 INTRODUCTION

. . . . .. . . ... .... ...... 1 l 2.0 VISUAL ~ EXAMINATION . . . . . .............. 1 3.0 METALLOGRAPHY. . . .. . . . .............. 2 4.0 FRACTOGRAPHY .-. . . . . . . .............. 4

. '5.0 CHEMICAL ANALYSIS. . .. . . ... ....... .... 6

6.0 CONCLUSION

S. . . . . .. . . .............. 9

7.0 REFERENCES

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LIST OF FIGURES Figure No.

Title Pm 1 AS-RECEIVED TURBOCHARGER BOLTS FROM DIVISION I. . . ' . . 12 2 - AS-RECEIVED FRACTURE SURFACE OF BROKEN BOLT FROM DIVISION 1. . . . . . . . . . .. . . . . . . . . . . . 13 3 INTERGRANULAR CRACKING AT FRACTURE SURFACE. . . . . . . 14 4 SEM METALL0 GRAPH AT FRACTURE SURFACE. . . . . . . . . . 15 5 SEM METALL0 GRAPH AT FRACTURE SURFACE. . . . . . . . . . 16 6 SEM METALL0 GRAPH. .-. . ... . . . . . . . .. . . . . .. 17

7' SEM METALL0 GRAPH OF INCLUSION . . . . . . . . . . . . . 18

8. SEM HETALLOGRAPH OF INTERGRANULAR CORROSION PRODUCT . . 19 9 PHOTOMICROGRAPH OF BROKEN TURBOCHARGER BOLT FROM' DIVISION I. . . . . . . . . . . . . . . . . . . . . .. 20 10 PHOTOMICROGRAPH OF UNBROKEN TURBOCHARGER BOLT FROM DIVISION I. . . . .. . . . . . . . . . . . . . . . . . -21 11 PHOT 0MICR0 GRAPH OF BROKEN TURBOCHARGER BOLT FROM DIVISION I. . . . .. . . . . . . . . . . . . . . . . . 22 12 PHOTOMICROGRAPH OF UNBROKEN TURBOCHARGER BOLT FROM DIVISION I. . . ... . . . . . . . . . . . . . . . . . 23 13 PHOTOMICROGRAPH OF NEW UNUSED A-286 BOLT FROM DIVISION I. . . ... . . . . . . . . . . . . . . . . . . 24

-14 PHOTOMICR0 GRAPH OF IURB0 CHARGER BOLT FROM DIVISION II . 25 15 PHOTOMICROGRAPH OF TURB0 CHARGER' BOLT 'FROM DIVISION II . 26 16 PHOTOMICROGRAPH OF TURBOCHARGER BOLT FROM DIVISION II . 27 17 PHOTOMICROGRAPH OF TURBOCHARGER BOLT FROM DIVISION II . 28 s

18 PHOTOMICROGRAPH OF TURBOCHARGER BOLT FROM DIVISION II . 29 19 PHOTOMICROGRAPH OF TURBOCHARGER BOLT FROM DIVISION II . 30

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20 PHOTOMICROGRAPH OF WASHER FROM DIVISION II TURBOCHARGER BOLT. . . . . . . . . . . . . . . . . . . . . . . . . . 31 iii 4

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LIST OF FIGURES (CONTINUED)

~ Figure No. Title Page 21 'SEM FRACTOGRAPH - DIVISION I BROKEN BOLT HEAD . .... 32 22 'SEM FRACTOGRAPH - DIVISION I BROKEN BOLT HEAD . .... 33 23' iSEM FRACT0 GRAPH - DIVISION I BROKEN BOLT HEAD . .... 34 24 35

[SEMFRACT0 GRAPH-DIVISIONI'BROKENBOLTHEAD. ....

25 SEM FRACT0 GRAPH - DIVISION I BROKEN' BOLT HEAD . .... 36

'SEM FRACTOGRAPH - DIVISION I BROITN BOLT HEAD . .... 37

27. SEMFRACTOGRAPH-DIVISIONIBkOKENBOLTHEAD... .. 38 28 SEM FRACTOGRAPH - DIVISION I BROKEN BOLT HEAD . ... . 39

. 29 -SEM FRACT0 GRAPH - DIVISION I BROKEN BOLT HEAD . . . .. 40 1; - .

30 ~ CHEMICAL IDENTIFICATION OF FRACTURE SURFACE , ..... 41 31 ' CHEMICAL IDENTIFICATION'0F CORROSION PRODUCT WITHIN GRAIN BOUNDARY CRACKS . ................ 42 Y 32 CHEMICAL IDENTIFICATION OF INCLUSION. . ........ 43 33 CHEMICAL IDENTIFICATION OF A WHITE PHASE OBSERVED ON

, ' GRAIN BOUNDARY... . . . . . . . . . . . . . . . . . ..

44 1

34' CHEMICAL: IDENTIFICATION OF CORROSION PRODUCT WITHIN GRAIN CRACK NEAR FRACTURE SURFACE-. .-......... 45 35 CHEMICAL IDENTIFICATION OF CORROSION PRODUCT DEPOSIT ON WASHER. . . . . . - . . . . . . . . . . . . . . . ... . . 46 -

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CHEMICAL IDENTIFICATION OF CORROSION PRODUCT ON BOLT 1 HEAD. . . . . _ . . . . . . ................ . 47 37 CHEMICAL IDENTIFICATION OF WHITE CORROSION PRODUCT ON RADIUS OF BOLT AT HEAD TO SHANK . . . . . . . . . . . . 48 9

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1.0 INTRODUCTION

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-Inspection of the Division I Diesel Generator Turbocharger during the NRC mandated teardown of the diesel engine (May - June 1984) revealed

'that.two bolts on one turbocharger had broken off and were missing.

4TheLloc! k wire securing these bolts'was also broken. On the other

~ turbocharger one bolt had broken off but was held in. place by the lockwire.. The remaining six bolts on the first turbocharger and seven lbolts on the second were intact and showed no evidence of cracking., A 2

similar inspection of the Division.II diesel: engine turbocharger revealed no such damage. The bolt material was determined to be A-286 stainless steel (see Section 5 for chemical analysis).

1.2: History

'The turbochargers on Division I diesel engine were replaced during

, maintenance operations on the engine in September 1983. The replacement turbochargers were obtained from Grand Gulf-Unit 2 engines which were in'a warehouse. It is believed that these turbochargers had about 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months of operation at the factory and had subsequently Lbeen in storage for a' period of four to six years. Exact storage conditions.could not be ascertained. These turbochargers, after installation on Division I engine, had experi'enced a total of 572 hours0.00662 days 0.159 hours 9.457672e-4 weeks 2.17646e-4 months 'of operational time and 119 starts during that time.

The turbochargers on Division II diesel cugine are original equipment and had a total operational time of 900 hours0.0104 days 0.25 hours 0.00149 weeks 3.4245e-4 months and 128 starts.

' 2.0.-VISUAL EXAMINATION-The broken bolt head and the intact bolts from both Division I and Division II diesel engines were visually examined under a low power stereo-

' microscope. The bolts had a reddish oxide deposit in areas exposed to 4

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2.0 (CONTINUED) exhaust gases. On some bolts there was a whitish salt-like deposit at the head to shank radius. Some bolts also had a small ridge of reddish brown oxide at:the interface between nozzel ring and turbocharger body. These observed features are shown in Figure 1. The fracture surface of the

~ broken bolt showed a smooth half moon surface and a grainy morphology elsewhere. A macrograph of the fracture surface is shown in Figure 2.

Lower power microscopic evaluation of the bolts did not reveal the presence of cracks in any of the other bolts and the fracture surface of the broken bolt showed evidence of secondary cracking in the grainy region.

3.0 METALL0 GRAPHY Meta 11ography was performed on the following specimens:

1. Cross-section of the broken bolt from Division I turbocharger.

2. Cross-section of a good bolt from Division I turbocharger.

'3. Cross-section of a good unused bolt.

4._ Cross-section'from four bolts'from Division I turbocharger (two each from right and left banks identified as R2,'R6, L1 and L3).-

.5.: A washer from Division II turbocharger.

3il Broken Bolt A cross-section, as shown in Figure 2, was obtained, polished and etched. The crack profile is shown in Figure 3. The crack is intergranular and appears to-be filled with corrosion products. In order to determine the morphology and identify the corrosion products, this cross-section was further analyzed using a Scanning Electron Microscope (SEM) . - SEM metallographs are presented in Figures 4 through 8. Figure 4 is taken at the fracture surface showing the Individual grains, secondary cracking and a profile of secondary cracks on the polished face. Figure 5 shows the existence of the

. ' branched intergranular cracks which connect to other cracks that 2

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- a.1 1p; 3.1 .(CONTINUED) emanate from.the fracture surface. Intermetallic precipitates, primarily titanium and molybdenum, are also evident. At a higher

-magnification, Figure 6, the corrosion product within the grain boundaries is clearly visible. The corrosion product was identified to be.pr.edominantly iron with no evidence of sulphur. Thus, the product,being iron oxide. This aspect is further discussed in Section 5, Chemical Analysis. Figure 7 shows the attack at the grain boundary and the-remanant of a precipitate. The precipitate was found to be mostly titanium. Figure 8 shows a grain boundary corrosion product deposit with evidence of a whitish phase along the grain boundary.

This whitish phase was found to be a nickel rich phase. The chemical identification of the corrosion products and phases identified here are presented in Section 5.

3.2 Microstructure comparisons -

, The microstructures of Division I turbocharger bolts (one broken plus one unbroken) are shown in Figures 9 through 12. Figure 13 is a micrograph of an unusual bolt. , Figures 9 and 10 show evidence of intermetallic precipitates, some grain boundary precipitates and large austenite grains. Figures 11 and 12, at a higher magnification show the grain boundary precipitation more clearly. Figure 13, micrograph of an unused.boit, is taken at a slightly higher magnification than those in Figures 9 and 10. A comparison between these three figures clearly shows that the' bolts in Division I turbocharger had significantly larger grains and were sensitized (i.e., grain boundary carbide precipitation). Also, comparing Figures 9 and 10 to the photo micrographs in Reference 1 a similar observation is evident.

The microstructures of Division II turbocharger bolts are shown in Figures 14 through 19. Figures 14 through 17 are micrographs at 400x

.on each of the four bolts (L1, L3, R2 and R6). A comparison between these microstructures and those shown in Figures 9 and 10 clearly show 3

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3.2 ,(CONTINUED) that the Division I turbocharger bolts had significantly l'arger austenite grains. The bolts from the Division II turbocharger had i ~

seen longer operational' time and similar operating conditions (i.e..

5 exhaust gas temperatures). Therefore it is clear that the larger

~

'grainsize in_ Division I turbocharger was due to the heat treatment process rather than a service induced condition. Figures 18 and 19 t' .are a higher magnification micrograph of bolts L3 and R6. Comparing Figures 18 and 19 with Figures 11 and 12 it is evident that carbide

-pr'ecipitation at the grain boundaries is significantly lower (Figure -

19) or not present (Figure 18). Once again, as shown earlier from grainsize comparisons, the sensitization observed on Division I turbocharger bolts-(Figures 11 and 12) are clearly attributable to the

' heat treatment process rather than to operational conditions.

Figure 20 is a micrograph of the washer and it shows a typical microstructure of A-286 material..

4.0 FRACTOCRAPHY The broken bolt fracture surface was examined using a Scanning Electron Microscrop (SEM). 'Fractography was performed both on a as-received condition and a cleaned (removal of. oxide layer using HC1) condition. The

. cleaning was necessary to identify fracture initiation, propagation and

final failure. These areas are shown in Figure 2. .

+ 4.1 Pre-cleanina Fractography

+_ Figure ;21~is a'fractograph taken at the mid-section of the granular fracture surface. It shows the grains and secondary cracks. The surface near the initiation site showed a similar appearance. Figure 22 is a fractograph at' a higher magnification, in the same region, showing the individua1' grains, a secondary crack at grain boundary and the oxide layer covering the fracture surface. The oxide layer was 4

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w 4.1 (CONTINUED) very_ adherent typical of high temperature oxidation. Figure 23 is a fractograph taken in that region (predominantly shear, Figure 2) and shows evidence of a dimpled structure though the oxide layer blurs the clear evidence. Figure 24 is a fractograph taken at the lip region.

The lip on_the profile at the cut section plane (end view) showed a 45' drop. . The ahear lip is covered by oxide precluding a positive evidence of-its presence. Based on the observations on the as-received surface it was decided to clean the surface in order to reveal the fractographic details that were not readily discernible.

The surface was cleaned using a 50% solution of hydrochloric acid (HC1).

4.2 Post-Cleaning Fractography Figures 25 through 29 show the fraccographs of the fracture surface after it.was cleaned. Figure 25 is taken near the edge where the crack initiated. The fracture surface shows the grains and secondary cracks. Comparing Figures 25 and 27, it is evident that the oxide

' layer has been removed and the underlaying metallic surface revealed.

This initiation site is typical of intergranular stress corrosion cracking (ICSSC). Figure 26 is a fractograph taken in the wide region of the grainy morphology. This figure can be directly compared with Figure 21. Again, this is evidence of an IGSCC crack. Figure 27 is a fractograph taken in the transition region (see Figure 2 for location) where evidence of IGSCC and overload failure are both present. At this stage the IGSCC crack had propagated to a significant length whereby the preload in the bolt was being supported by a very small ligament area. Just adjacent to the transition zone is a region of pure ductile failure (see Figure 2 for location). This is shown in the fractograph in Figure 28. The dimpled structure, not clearly evident in Figure 23, is now obvious. This region marks the final stages of fracture of the bolt. The last stage of fracture was by a shear lip and this is shown in Figure 29. Once again, comparing 5

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4.2' (CCONTINUED) t Figure 29 and Figure 24 it is clear that this region is better 4- >

revealed after cleaning. Based-on the fraccographic observations it is evident that the crack initiated and propagated by IGSCC over a majority of the f racture area, converted to a mixed mode -(IGSCC plus shear) when overload conditions were approached, to an overload -

ductile tearing mode and finally to a shear lip failure. This progression is approximately mapped in Figure 2..

. 5.0 CHEMICAL ANALYSIS

~The purpose of chemical analysis was to:

1. Ascertain the bolt material spe61fication since the material specification was unknown;

2. Identify the chemical species of the corrosion products on the fracture surface, within the grain boundaries, on the grain boundary and in the precipitates; and,

3. Identify the chemical species in the different colored corrosion products identified in the bolt and washers.

Item 1 was performed by. wet chemistry techniques and items 2 and 3 using the energy dispersive x-ray fluorescence analysis feature in the SEM.

5.1 Bolt Material Chemical Analysis The chemistry of the bolt as determined by wet gravimetric chemistry and typical composition from Reference 2 are provided below:

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Chemisty (wt/%)

. Element As Determined Per Reference 2 Chromium 13.69 15.0 Nickel 24.28 26.0 Molybdenum 1.02 1.25 Titanium 1.98 2.00 Vanadium 0.24 0.30 Silicon 0.23 -

Manganese 0.16 -

Aluminum 0.16 0.20 Copper 0.06 -

Phosphorous 0.013 -

Boron 0.004 .005 Sulphur 0.009 -

Carbon 0.042 0.04 Iron Balance 55.2 Based on this comparison it was determined that the bolt material was A-286 stainless steel (iron-based precipitation hardening alloy) super alloy.

5.2 Chemical Identification Corrosion Products (Item 2)

The fracture surface of the broken bolt was analyzed in the SEJ!. The clemical species identified on the fracture surface are provided in Figure 30. Other than those attributable to the base metal, the presence of zinc, silicon, sulfur and calcium can be attributed to their presence in a typical fuel oil. The small sulfur peak indicates that the sulfur in the fuel oil was relatively low. At such low concentration of sulfur in combustion gases it is not conceivable that sulfidation could be the cause of ICSCC. Furthermore, per Reference 7

5.2 (CONTINUED) 3, for alloys with nickel concentration greater than 25 wt% and chromium less than 15 vt%, should sulfidation occur, the corrosion product would be predominantly nickel and sulfur (from NiS). This is because higher amounts of chromium would be necessary to preclude the formation of a low melting nickel sulfide eutectic. Also, Reference 3 provides a table for recommended maximum service temperatures in sulfur dioxide atmospheres for some selected stainless steels -- these temperatures range from 1292*F for a 410.S.S to 1850*F for 446.S.S.

Considering this, it is not plausible that sulfidation could be the cause. In order to confirm the primary cause it was decided to identify the grain boundary corrosion product species. Figure 31 shows the identification of chemical species in the corrosion product shewn in Figure 6. The corrosion product is predominantly iron with a notable absence of sulfur and very minute amounts of nickel. This would indicate that the corrosion product was predominantly iron oxide. Figure 32 shows :he identification of the precipitate shown in Figure 7. The precipitate is primarily an intermatallic compound of titanium and molybdinum. Once again absence of sulfur is noted.

Figure 33 identifies the product which appears as a white phase on the grain boundary in Figures 6 and 8. Figure 33 shows that the phase consists of species from the base metal itself. This is not believed to be a corrosion product. Figure 34 identifies the corrosion product within a grain boundary close to the fracture surface in Figure 4.

Comparing this with Figure 31 shows the only difference being the presence of zinc in Figure 34. The minute amount of zine was also observed in Figure 30 and believed to be from the combustion gases.

The notable absence of sulfur and predominanca of iron cler.rly shows the cause to be a high temperature oxidation mechanism. This observation is supported by articles in References 4 and 5 dealing with high temperature corrosion processes in stainless steels.

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I 5.3 Chemical Identification of Corrosion Deposits (Items 3) n The corrosion products observed on the bolts and the washers were analyzed.~ The corrosion product on the washer was a biege colored

? deposit and the identification of species is provided in Figure 35.

The species indicate that these are products of combustion of the fuel oil. The brown colored deposits on the head of the bolt is identified in. Figure 36 and this spectrum is similar to the one from the washer.

Comparing these two to that from the fracture surface (Figure 30) it

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, is clear that the fracture surface did not contain the quantities present on the exposed surfaces. On one of the bolts, R-1 of Division II,'a white deposit was observed in the fillet region between the shank and head of the bolt. Identification of this product is provided in Figure 37. This product had a significant quantity of copper. The amount of copper in the base metal (0.06 wc%) is not sufficient to show such a large peak. The presence of copper on this

, bolt's surface is unknown. However, the bolt did not show any evidence.of pitting or cracking underneath this product. Therefore, the occurrence of copper in this deposit is not a cause for concern.

6.0 ' CONCLUSIONS Based on the analyeis, observations and evidence presented above, the following conclusions can be supported:

o Division I turbocharger bolts were found to have had a larger grain size than those of Division II and that the Divisfon I bolts were sensitized (carbide at grain boundaries) indicating that the Division I bolts were improperly heat treated.

s o Fractographic studies showed that the fracture was initiated and propagated by ICSCC, with ductile tearing and shear failure occurring during the final stages due to simple mechanical overload.

9

6.0 (CONTINUED) o Analysis of the corrosion products within grain boundary cracks, the fracture surface, bolt head and washers clearly show the IGSCC to be caused by high temperature oxidation. Sulfidation mechanism is ruled out because:

a. absence of sulfur in the corrosion products within grain boundaries;

b. extremely small amount of sulfur on fracture surface as compared to the corrosion products on the bolt and washer; and

c. the morphology of the fracture surface (granular versus sponge like appearances for sulfidation attack).

o ICSCC of the fractured bolts in Division I turbocharger occurred since these bolts were predisposed to this phenomenon by virtue of them being sensitized (improper heat treatment). Whereas the bolts from Division II were found to have had a proper heat treatment and no sensitization, hence did not experience any cracking though it had been in service for twice as long as those on Division I.

o- A comparison between the microstructure of the Division I and Division 11 turbocharger bolts show that the larger grain size and sensitization of Division I bolt was not caused by operating temperatures. Instead it is heat treatment caused. Therefore, measuring turbocharger inlet temperature may not be meaningful to the present cause.

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7.0 REFERENCES

1. "Metallography, Structures and Phase Diagrams". Vol. 8, Metals Handbook, Eighth Edition, American Society for Metals, Metals Park, Ohio.

2. " Properties and Selection: Stainless Steels, Tool Materials and Special. Purpose Metals", Metals Handbook Vol. 3, Ninth Edition, American Society for Metals, Metals Park, Ohio.

3. " Handbook of Stainless Steels", D. Peckner and I. M. Bernstein, Editors, McGraw Hill.

4. " Source Book on Materials for Elevated Temperature Applications",

E. P..Bradley, Editor, American Society for Metals, Metals Park, Ohio.

5. " Super Alloys - Source Book", M. J. Donachie, Jr., Editor, American Society for Metals, Metals Park, Ohio.

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Figure 1 As-received Turbocharger Bolts From Division I 12

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Figure 2 As-received Fracture Surface of Broken Bolt From Division I Shows where specimen for metallography was obtained. The areas gof fracture initiation and propagation were marked based on fractegraphic evaluation presented in Section 4.0.

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'.. _{'-)'.1 Etchant: 107, 0xalic Acid Magnification: 100x Electolytic Etch Figure 3 Integranular Crack at Fracture Surface Crack follows grain boundaries showing a typical IGSCC appearance. Inclusion like islands in the matrix are Intermetallic Compound precipitates.

l 14

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4 Magnification : 500x Etchant: 10% 0xalic Acid '

Electroljtic Etch Figure 4_ SEM Metallograph at Fracture Surface

, ~-

, n.

Grains on fracture surface 'and a ' secondary' crack are visible. Ttc cracks on polished facc -are branches fr ,m a. main . secondary c. ack that emanates to the fracture surface. The main

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.

denotes area for chemica'l' identification Y

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Etchant: 10% 0xalic Acid Magnification: 5000x Electrolytic Etch Figure 6 SEM Metallograph Corrosion Product (Iron Oxide) in Grain Boundaries (Division I)

Corrosion product within grain boundary crack clearly visible.

Also visible is a white phase segregation along grain boundary.

denotes chemical identification area 17

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Inclusion was found to be an intermetallic compound precipitate formed during aging treatment. Precipitate was a Titanium-Molybdenum Intermetallic Compound.

denotes chemical identification spot 18

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Etchant: 10% 0xalic' Acid Magni fication : 5000x Electrolytic Etch 1

I Figure 8 SEM Metallograph of Intergranular Corrosion Product l Nickel rich phase along grain boundary.

denotes chemical identification pot 19

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Etchant: 10% 0xalic Acid Magni fication : 400x Electrolytic Ecch Figure 9 Photomicrograph of Broken Turbocharger Bolt (Division I)

Note large grains and intermetallic precipitates. There is some evidence of grain boundary precipitation.

i.

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Figure 10 Photomicrograph of Unbroken Turbocharger Bolt (Division I)

Large grains, intermetallic prccipitates and grain boundary precipitates.

21

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Etchant: 10% 0xalic Acid Magnification: 800x Electrolytic Etch Figure 11 Photomicrograph of Broken Turbocharger Bolt (Division I)

Note grain boundary precipitation, indicating sensitization of bolt material .

22 L

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Etchant: 10% 0xalic Acid Magnification: 800x Electrolytic Etch Figure 12 Photomicrograph of Unbroken Turbocharger Bolt (Division I)

Note grain boundary precipitation. Indi, cates sensitization of bolt material .

O 23

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e., f**;,m:u :s.w.. . av m . c A r u.re.:f W.' tW-Qh t &..

b .M Age g ' ;'

e.'{, t.r 78. e % :

U <

., w. . ._ v. .

u /,2 - . 4.

,. .,.g

~c :.t

.c..

.. -. t.y.?/

%. ,; ,,<k.

.xMgg-;..x

w. w.

. . u-

. gyc.,E

. u. :n. .6 w. q> . . ..., . : .

~m.an .

. x.

. ::n .. m . r. .. c . c.g.4fp.

.. r k s;ns.p\ t. ~, 7

.sr.q?v;$w.:.21

.: 9wy(Ea:;k. .. .

M qq p.:p;;;

lk;4. g ,.ls p 5i.W.w 3;:y+..v.. .bM.n, s#k. .-6)M.h crs .. ..

l[p.

. er<..r,e:.

I

.5..&.

N. ,, <.r

n. .

.;g N..

'y@a.

4.c

..b

. .h4-c,

.v, r- .f@; . v.n()NiE$1'y

.]..m..-

. :8 .

. ,,k .d..M,$q. s.. ". f

-.7J ' s: . m y. r.. ....- . :.- .,

I.t.;y .

i p ,. ,, * \ . .

.r

-4 ,.._..;

b . . . .

ang: .,a

' g . ;, ..t.1 .

, ....c.--

. w L,/esf. s v...N W.af i de' s'.w'imm ~ ,.. > 2. s .:.-s % d **.D %

Etchant: 10% 0xalic Acid Magnification: 500x Electrolytic Etch Figure 13- ' Photomicrograph of New Unused A-286 Bolt Small g~ ains. No evidence of grain boundary precipitation.

e 24

m l l

l br '

a D h

e l!!d,f// 1

. als -s a,

"'t,4 ?F u EV ?,#.M - ,

h Ygg e

(g6# hi'

M

@Qd:hh'AV 4c4%a

~s t

r m> ;pp.-,,e;w.w,

%?Ws% -

4 5

? p

,*g.,A,.

.w%,;iY (l

5.d.e if !'z,g;%k,s.s

- J }s.

w~$N

y s' V 6~V3f*?tyydM'.,1 o7

,? #7%.

4I: .' h *DVf fth @M;..i,1 p.rP

$,3+,

'l Etchant: 10% 0xalic Acid Magnification: 400x Electrolytic Etch Figure 14 Photomicrograph of Turbocharger Bolt From Division II L-1 Bolt Note smaller grain size than the Division I bolts. Micro-structure shows some evidence of stepping, indicating absence of sensitization.

25

s e

if.id*-o,c...h' n

.._* e .sqd:'s -

p v, i*, ~ l,A[*,

m .hyV.

. p .s;s

~wMe '.: , l u g%w=*.:.MN.,e T.tr s'.*

4 ;:pD, .s. win W 3h gp%;

f- .: 3.- .

1 1 u v& o +s . s ..

k h i f*t ." 8 * !. ,- [ c . '* %

' % s -1 e<*/ e.. V !,, 9

., ..d-%;w%up' > td? ~~W (!

. Ut

,))?(t .y h.. h*e tw;O, W,w (5 N ;'p'?NU )b

~

- a ._p .

a . .n -Q. .

!I*,E*hh " . y' k, . . m YA N* h 5*

$.. 7f4.0d(98tf!pfIt;,'.%..

~ s 1 l'*h. Q n.w,&,O.,e... . f.

' r- , /,

m ,f.

<: .=. . .gz.Q;;>;? ' ..v.9 '.

?, Ey,' w k.r r .;,:gg:r," g> ..h a;]4 a -

L' OX n 3 $$i?!:%

'1 ' _

b^l'h C h _$_ 1 5 4 Etchant: 10% 0xalic Acid Magnification: 400x Electrolytic Etch Figure 15_ Photomicrograph of Turbocharger Bolt From Division II L-3 Bolt (Same as figure 14) 26

-e e e

. g gg*, w-*.,. .* e g 7 .; e - p. _ , g . x - w . - g ,

, ...y. *. -

g'J '-

.(. . . . s. 9 -' . s, . - O .M.

g'

,\ ;

.... ~.m. w'Y.Ca .c

.t. ';; < -:. .., . s .-

. , Y, Y s. -< ) <

, i e, . , p ,. . ,,3. . y .~... ..

. , e.;.?,

.. * . -. . . . . ...1, , . ..

i .o ; . .' . wy-6 .* .<p e 'l

.e

~

m .

.g

..~.ao. )s .

.a. -: <.

,,.. . ...=,.:. = -

.+%. ( ;r,.s.: ,.e,.Nr:.G.W.:

- .J' .ch ;>, . ,.., ..y

.:..r , u .a.c

.v. v.,v. . . .~ ..r c.. ,~. y) -

l:,- . f g./.M' M-.. p...;n..~ .~^x..h. ^1./;%

m.

. = - **

e*-

..e 2,O C.i o . ,% .'e6 .

,;,g *'.d.L.

Y 4',**Ju> .t v ., J % .. .,' --Y).

~ s'

-},4

,:q*. P.u .' b,g e.s ." ,- .

....s p 2.'e e ..

. -. t N. >

p: .' . L , .'

. . . .n s

.$ .k.;A .: 1;

. so.-

. :*. . p ,. s f o g,; .;% 4

.'*f. f y .. % :%:,. .., 9. ... k . . .

. .. L~ .,cr.,

f.N. .. .g

.r

..; w*. . > . ~ . , . . . .. 3,

.12. .:': i s . .a- f .

.. .y

.:.6 ' j $1.ld..C. A s.E R .S.',b Ed 2.31

Etchant: 10% 0xalic Acid Magnification: 400x Electrolytic Etch Figure 16 Photomicrograph of Turbocharger Bolt From Division II R-2 Bolt (Same as figure 14) 27

l r

p;=. pg;.a r.

.~ -,;f

?fi',

p

-~=s ,-- (g-l p

W ' { l'~ &Q* i.

M. ., Q S- ;.b Ag}.tw? Q 0lb.g4 .'l-' i; -

k

$N l k [' ' _- .ji f_E g

&a&n n z,

,;.'N'CY lg:, !. , h, lhk -u ... '-

>< ., e s Ec .

c

, fYi;>y;~ Gf $NeY . y< ,?., .sl Y. :- -

a' jkY. W .,ii- $'f , ,I#* S ?g $a , n' i.af i, e'

- l

k N* . : . i .

Etchant: 10% 0xalic Acid Magnification: 400x Electrolytic Etch Figure 17 Photomicrograph of Turbocharger Bolt From Division II R-6 Bolt (Same as figure 14) 28 i .

Pd,.ti ,. W--

at .um Lp5bkig%.Mrf5%.....%c,'Q:.h..' % ga x c v

w ; ..-s nQ. u &. m , c: %.c ; ;. y.

, y k %q=.,,.?;s.

~

. q 4 s sqo 4 yE yhp ...a~' ~n. ww';

w.. % 4

,as.4M*,$7 @I-l 6% ?.:.o .

. -a , . w ng'y 8,M. .',.p..t:T=

.r.s wr n .,e.+n d '*h,s., ;-.

,.. w... #, c c. .m.. r. ., +

. ,r . .

s v .,

a

'. + p. ..-n, w.sv.y.g

. e. , .

t s .1M. . . F $.NSA.

f. ./ A. . f l.*~ e t.s,e *-- u . ;t,l4

.#s,T:.,hr. . %4,a,n, ,; :

fip4M...I.'p..,T,,u*Q'M".V,.N5',

-- w x, r u,. ). y a. ag:.>

'W.$,m,3 ;

iii.J ph1s;fh'N5k'ftfA2,I'E.h$'f.T/E bkI m

M+L-Ffoi u ! . *,%. . ; .'f*y,.

f Q, ,e; \' ",z,

n~. ; .%n

-*! ,is fsFg'i* A4 :. J.r.y W.jn

- --~_.--o ' .r.g. _s t ..8,n. ;:a; Etchant: 10% 0xalic Acid Magnification: 8C0x Electrolytic Etch Figure 18 Photomicrograph of Turbocharger Bolt From Division II L-3 Bolt Note absence of grain boundary precipitation. Material was not sensitized.

29

i

.. .- .- .n 3, . - -

' %. . s A.

. . ', g,...Q; A,f f. ,4..

. . ," ,LM,y ~.

4 .;,'C. e,..

y.j4.'.'p%D

. , #m*D;u. '-.)%'%t g:tW. %Q,.. . ,4. %b i '* ;<

N@i.h, 4,tJ k... p:

sy=. s h

C~:pf, 3w}

t.s.rd(hy{jsc.sd.).'e:.L.-

%ii J,W, .'.? %w.-n'

.1lga %zai.; m '.h f d C q5 .-

( @.. W y . s/ W sE h ; a-p s}g g g:f. W :;

4A ; :. wg.,k . n" ewnn%,,,ot,y.

wew g;1

%.w.

$,bhy .'lhY.hi 3

'N < ffi $ '

Nile., #

w% ;%.. ..A %d

? Shgp*-

B,c,g - T9sv,V- A ,(. .v43.. Sp *- 4

'e w n JM.

p, i y .( ~ ' g.- t .9 i. -u d4,2?n%g' ' . . .i p .. . . . -

f, %-* *sp

. 2. + ,

. 5, _.;. %.--i ,-[st?;/g,,g<.

Q%M. hI yp~

iip *&:g*d A; g%p!/' ^ '

D

+MJ,y47*}ypg 'aQ;%' .,w.hf'.A*}14%,1 < MS(..

~1 a .-

44 og . A y r.* t . p;,< . ,w

.x , q' r. g

- > 319*.gMc . sn2'.hy\

.5 .

.;%n Rs v -

y 'h. 3m <x et s %,,,

i l

Etchant: 10% 0xalic Acid Magnification: 800x .

Electrolytic Etch Figure 19 Photomicrograph of Turbocharger Bolt From Division II 1 Very slight evidence grain boundary precipitation. Material is not sensitized.

5 i

i 30

o 5Q'kFTs & > iQ"f.-Fj'L. y G ;*qq-4 .;o.

t y

? I

.nq1 % n, Ai 9,.s.2.ig?,&

y w .% y;.*.**qq?

g %pNJ w, .yu:.

e,3 . c. ~3% r .;,, s iftp kedb:3!$pr..4h -

$$(@??@?%@0 14

%@$$dv@$y M 5t h2

$i pad 4se%gM+.hoh!gswwc

> s ,' N O IC y N f > N T. h #

Ld:^.VT-sk?f*sr3_;4"Q.C'<,.&rfQ*1%q$v2.: ,1 Etchant: 10% 0xalic Acid Magnification: 400x Electrolytic Etch Figure 20 Photomicrograph of Washer From Division II Turbocharger Bolt Typical A-286 microstructure.

i I

31

(

~

jf:

r a ,,. - p: wg k

g p '*pb.

a .

% .a

, \

, . .. $/I' If,hh;. -

'$ 5_ _

.r aM. ,

f .

' g~gf x n

f,$s

f'3 Q8hbSYkfgb g

^

t

< l.

$fe

'\

. kN l p

,4 - t .e*r81

, , . . ~

M

!DP$$,. & . , 39A.[.kh;&,3 "jd%6 "'ite N:42 6

Magnification: 200x Figure 21 SEM Fractograph - Division I Brok'en Bolt Head Individual grains and secondary cracks are visible.

Surface covered with an oxide layer.

32

=

--*q. g, -> i eq[~-.;;...

~

7 W +. ? g N g! ,. , ,, '#'A Nik.g%y

=v~ y I

>+

?d/ ' #' 5 :.i , in '

I ,

M.M'.-i.

e.3.: :

.s' I S-Q,' .p ., y f.. f,'i 9 ~.

, l g , .g*

1

, , . 5', # g . f. ,f h k "I, 'y 3

g{'\ v)3 #

.5 ' i q Q ry

- - ., i

i. p. .y i .

Y;k '

M .; Y 2 . >

> .N <

L.i [ .3. f,; - .eg; s e, - -

i.

MA

. , ,,g, c! l hb$Y,,.d,--[Q.$.? i Magnification: 900x ,

Figure 22 SEM Fractograph - Division I Broken Bolt Head l At higher magnification secondary crack, austenite grains and oxide layer are clearly visible.

l 33

k YQ.!N $$ GM.,' .} -

T'ek ~ .J~' S$

tew[$

g e- I.Dl A

- fj))tIdf#- 1* ~ .. .h $2

} .'#![4 f

n:cf . . .

si

.(J

, pM ', 'a

_ m u m m u(

l Magnification: 1000x

. Figure 23 SEM Fractograph - Division I Broken Bolt Head Taken near the smooth appearing region in Figure 2.

Appearance of ductile tearing due to mechanical overload is blurred by oxide film.

d l

34

p,a s' ~

s. , T

>&}er*r?

gw r Tw.,te ,, w -

.7 53 --

w .

D gs 24 m. .

Y

b3 f ' '" , ~hW8 jq, eg[h h ,

E s

hfhkh.> kk! .

Magnification: 50x Figure 24 SEM Fractograph - Division I Broken Bolt Head Area near shear lip. Appearance of shear blurred "

by oxide film.

35

'Va~9 J ?- MMI' 9nfi

$#V.nW'%Y$r*#;h;$6G W:

y Ll4 feif'Afd;n$

q4c:~

$ a.

s

,y p

- 3. erg

,. N pee!,g97[.

5 m

?

T1,k ' &r ' ..,1r#

'$$h)4

~

[d../'*

+ pt y fjYs^ ' Yt0D f

'% . J' g .M;,IrpglA 47 ' 4- , 4 g' j [At , f' '

g NN;g? ! -

l ff' Jy . Y?C , W l

$Q .M Of .I ,'3, I MY. \l#-h*jb/Mg'O j-L'.%edAI 2:dW' ($??$$5$i Magnification: 450x Figure 25 SEM Fractograph - Division I Broken Bolt Head (After cleaning)

Fractograph taken near initiation point. Clear evidence that IGSCC initiated cracking.

36 L . _ _ _ _ -

o P 9 ~

7 y"

.. V 'Y1..u,*f,%[J" ff

/Qs ,, ,

,4

{Q h

5 5, , h * '

,,sb.Q:ag;,,su,22 J%'.,~gyjk%

$}jf5."".

4d $6jg

,M+w3b}JT,? ~~~

. ,3p: . .. , - a.,.

^

q C ~ f ., .- * , . .

7

' ~

s Magnification: 400x .

Figure 26 SEM Fractograph - Division I Broken Bolt Head (After cleaning)

Fractograph taken in the mid-region of grainy surface. Evidence of IGSCC is clear.

i I

37

rssc.o -

v

+

. , . ,'yJ2,$V b.yg$&*'D .2 hs. . 'f5

.x /f~'h;:

'< % %h Nk - = f , ,_ h fW 5%). - -

5f.. f$ %~'5 4 AA h(y Eh*[ . . ' M fta j fj ,

pQv: - r. . r. A k' .jVASL*

, 3. .\s86Y, kM , ',5 b'4 a U S '2 'el/ .~ 8;5 kw '

%f#V dudile feuiM Magnification: 200x Figure 27 SEM Fractograph - Division I Broken Bolt Head (After cleaning) .

Fractograph taken at transition region between grainy surface and smooth surface. Evidence of IGSCC (grains and secondary cracks) at upper half and ductile tearing at lower right.

b s

38 km_-

n 1 4

-? ? ,

Wypt'*i@f'E*s'A #f.NW#~;#

, W %,/

e .. sw::r ,p'

'p, h

.m. IY,,

? f.1 I

.w .gus, %a.,.l'4y,hh

~ !

h?b hhY Magnification: 160x SEM Fractograph - Division I Broken Bolt Head

~

Figure 28 (Aftercleaning)

Taken in the smooth region in Figure 2. Dimpled morphology typical of ductile tearing due to mechanical overload.

(Preload supported by a small ligament area) 39

s 7, ,yg y s w y rics.;.z e

fl ?-x;y.=y

%~*s2Mf i'A=3.,;$S%4, T. .

its#M$p"!JJ9w1to;-c g

Wz.y:4%;b.:4:s a v. rce w sp. i n ie di - % s- e .ca

- b.inlW

.s- ,

hD:NNhy$kU' Y,%w 'lhE4,g[.y*N.

~

[ ..NNNQ) h' a s w m e .e '

- ! I g 4 7 "'

r W b. 3.A. ~ n~ ?

e.: $byrf tak,ur#2m.}i i - + $$ h. 4 fg& r ^ A lg,a QoMTw;.2

% :-g g 4 Magnification: 40x Figure 29 SEM Fractograph - Division I Broken Bolt Head (After cleaning)

Shear lip formation is evident. Indicates the last step of fractur.e.

M 40

. , /

~- ,,

~

- a p : v i 10: SORFRCE CORTING -

? EG AG ~1 -

l 4

PST: LT= SOS CPS: 397 OT: 16 FS: 10t4 LOG GRTEC

3 i

.s r l

l t

s

! ~ , ~

- 0

! ./ ,

3 _

~

I '

i \

l 1

? y b

i h

l

? g -k .

& ? ? * ~

E E 3 E & E

.. ~ , e a 1 l i s 7 y Y F

. 1 ,d {I th ll $

(* \iN Q$ lu;;

I Figure 30: Chemical Identification of Fracture Surface

i Zinc, Silicon, Sulfur and Calcium are attributable I l'

! i to fuel oil combustion products. The amount of I

! sulfur is not expected to cause sulfudation attack.

i 1 i 1 l R.000 2.557 5.115 7.672 18.23 l 8-19 KEV

EGLG 10: WITHIN GRRIN BOUNDARIES OT: IS FS: 2K LINEAR ORTEC PST: LT= 1005 CPS: 1985 2

1 i

-- Figure 31: Chemical Identification of Corrosion Product 1 4

Within Grain Boundary Crack Note absence of sulfur and small quantity of r.ickel. Indicates sulfudation is not a !

~'

causal mechanism. (See figure 6 for micrograph) t l g t

1 i

I' 4

( _.

b 5 5 e e i _,

8 2 5 4 = s e

I

l

".__"__^~~^-'^.____p _ , _ ___ ___

.... _ 3_g 19.23 7.672 5.115

9.000 2.557 E-19 KEV

m . , .

.g sc v >

~ - ,

p ,

x ., .

4 .

c w. . _ i . --

.s

.#3 4 / s._

. ;f.% NQ, , t, s

4 % .. T_.,

s

,, .e

, e.

f ' _'%c '- ," t 4, w, t "y. ,;

-s,7 e- , , ,

.;g -

- ,I'

, (. ,

-* '4 s. ' , , ,

i _

c w* .

\g. .g i k4 f1 J

' " 7, -

M, fc' 10: INCLUSION r 1 g- '3 "

24 FS: IK LINEFR-

' ORTEC-PST: LT= 100S CPS: 2571^ OL: .

,.. s s ,

oy .

~

f

f '

- s 2 .,! .

~

4 ,

^

~

-- y Figurei32:', Chemical Identification:of Inclusion -. ,

' Predominance:of Titanium ed Molybdenus 3 , indicates an intermetalli.c ' precipitate.

f(See figure 7 fdr micrograph) .

, e , s

/

I 4 4

s. ,

i .1

I 4 ..

f V ..

n (y i

'_ m ?

'j.

~'

[ y s

I ,

1 h , b 5a g O

e

.- t3 Y

1

-= - W - a:"N'i

-i . Ei

-- - - - % M-Tt IG.23 7.672 g,ggg 2.557 5.I15 a-l a M EV

EGLG 10: WITLilN GRRIN BOUNDARIES ORTEC CPS: 3496 OT: 56 FS: W l.lNEAR PST: LT= 1905 - . -

l 2

Figure 33: Chemical Identification of a White n

.. 5 Phase Observed on Grain Boundary T,pical of base metal composition (See figure 6 & 8 for micrograph)

.. l d

A 6_.

I

. h t

5 :

g

" E I

b 1

& D -

5 5 5 N b $ 5 ,

i a e : e -

I 4 a # T 2 I I y g.

w -x+ - ) 1~--

~~

i .. . _ _

' ' .____.___.4-._...__ _ _ - _ _ -

iG.23 i -4 7.672 5.I15 g.ggs 2.557 E-19 KEV

EEDS-Il EGLG 10:

PST: OFF CPS: 2048' OT: 16 FS: IK LINEAR GRTEC g Figure 34: Chemical Identification of Corrosion k Product Within Grain Boundary Crack Near Fracture Surface Note evidence of Zinc.

4 (See figure 4 'or micrograph) 1 l

c1 t

GEIB t

5 E a h 1 * .,

5 b 5 6 2 I ~

B" 1 i i x a p _w N' , ,

7.672

, i _%

10.23 G.009 2.557 S.Ils E-19 KEV

EGLG 10: BlEGE-COLORE0 DEPOSITS 0T: FS: 512 LINEAR GRTEC PST: OFF CPS: 1533 -

11 Figure 35: Chemical Identification of Corrosion Product Deposit On Washer Spectrum shows predominance of combustion product species.

Note the small amount of base metal elements and the reversal of trend from figure 30.

d I u a

E c 7 !

1 s t

g l'l

.s 1

t l

i .

l 'I I

1 I_ i l

o L

t I i -

-- l t l

( w/ m A w W W %' p u/ L )(

4_ __.... -

e,

-i

= - -

7.672 19 23 g,ggg 2.557 5 I15

, g-19 KEV

i

.a EGLG 10: BRouN-COLORED DEPOSITS- R1 PST: OFF CPS: 1838 OT: la FS: 512 LINEAR GRTEC

. = -

$ Figure 36: Chemical Identification of Corrosion Product 1

t On Bolt Head Similar to the washer - except that base metal elements l

' are more predominant here. 1:

B 6 5 5 !

.. g l o 0 5 e

i l 1

.. l f

F I E E

& 5 h I i

E D g E & ' '

t a v.

l. l 1 t

T 5 i.

7 e

{ z Ofk fiI h $ M 1 jh (

! . - - - - ,- _ g__- = .- .Ii 12.2J G.09R 2.557 5.115 7.672 R- 10 R EV

5 ...

< ,r

.cd 10: WHITE DEPOSIT - R1 EGLG PST: OFF CPS: 1867 OT: 13 FS: 512 LINEAR GRTEC

@ Figure 37: Chemical Identification of a White N Corrosion Product on Radius of Bolt (

~'

I at Head to Shank b Note presence of Copper. Base metal copper is not sufficient to cause this peak.

Source Unknown: However, presence of Copper is no cause for concern.

t_

g g

I 5 !

E f f &

d g

' Y 5 h $ E h a s E E a

.! E I E t

2 i ' y p

l l

u p i N pAhh 'N.yy I h 1

. . . iWV '~

R.000 2.557 s.II5 7.672 l a .' 2a E- 19 K EV

_

ML20093H560

Contents

Text

1.0 INTRODUCTION

6.0 CONCLUSION

7.0 REFERENCES

1.0 INTRODUCTION

7.0 REFERENCES

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ML20093H560

Text

1.0 INTRODUCTION

6.0 CONCLUSION

7.0 REFERENCES

1.0 INTRODUCTION

7.0 REFERENCES

Navigation menu

Search