ML20207H249

Metallurgical Analysis of End Cap-to-Header Weld Overlay Boat Samples from Quad Cities Station Unit 2

ML20207H249
Person / Time
Site:	Quad Cities
Issue date:	07/20/1988
From:	COMMONWEALTH EDISON CO.
To:
Shared Package
ML20207H245	List: ML20207H243 ML20207H249
References
M-3106-88, NUDOCS 8808240412
Download: ML20207H249 (15)

Text

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" A174GtMEAlT- 3 SYSTEM MATERIALS ANALYSIS DEPARTMENT REPORT ON METALLURGICAL ANALYSIS OF END CAP-TO-HEADER WELD OVERLAY (02A-S10) BOAT SAMPLES FROM QUAD CITIES STATION UNIT 2 Introduction Ultrasonic (UT) reflectors were found in the end cap-to-header weld overlay (02A-S10) at Quad Cities Unit 2 by General Electric (GE) j nondestructive inspection personnel using an automatic technique.

The reflectors were verified by manual scanning performed by GC and SMAD NDE personnel. Three boat samples were removed from the overlay to capture select UT reflectors. Questions arose as to the exact location of the firt two boat samples. Therefore, a third sample was removed,under guidance from SMAD NDE and metallurgical personnel, which captured a reported UT reflector. A detailed metallographic i-examination of all three boat samples snowed no evidence of flaws. ,

Although the source of reflectors could not be defined, metallo- '

i-graphic examination did reveal large columnar grains. These grains are thought to be the source of the spurious ultrasonic indications. -

l Boat Sample M1 -

t This boat sample was removed approximately 3.1" from the edge of '

the overlay nearest the end cap and 2.8" from the zero reference stamp. The boat sample was oriented in the circumferential direction to capture reflectors identified as #33, and #70, as shown in Figure

1. The as received boat sample measured 0.350" deep, 0.525" vide and 2.50E" long.

Boat sample M1 is shown in Figure 2. The sample was sectioned at the five locationc shown in Figure 3. Each cross section was metallographically prepared and examined at magnifications from 50x khj8240412880816 g ADOCK 05000265 PNV

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- Page 2 to 200x. These examinations were performed after polishing, and again after etching. No defects were observed. The weld metal microstructure exhibited a primary ferrite solidification mode.

Figure 4 shows the weld metal grain structure.

Microhardness measurements made in several different locations revealed a wold metal hardness equivalent to 95 Rockwell B-Scale. A qualitative analysis was performed in several different locations using an energy dispersive spectrometer (EDS) attachment on a scanning electron microscope (SEM). The results indicated the weld metal is type 308, nominally 19% chromium, 9% nickel.

Boat Sample #2 Boat sample #2 had its major axis oriented axially. Figure 5 shows the location of boat sample #2 which was 1.5" from the zero punch mark and extended to the edge of the overlay. Figure 6 shows the as received boat sample and the markings where cuts were made to examine various cross sections.

The cross sections of the sample were metallographically prepared and examined in the polished conditio1 and in the etched condition at magnifications from 50x to 200x. No evidence of flaws were observed. The weld metal exhibited a primary ferrite solidification mode. Figure 7 is a photomicorgraph of the Weld metal microstructure.

Microhard7ess measurements in various areas were equivalent to 95 Rockwell B-Scale. A qualitative analyses made at several locations in the weld metal with EDS revealed a composition similar to that observed in boat sample M1 (nominally 19% Cr-9% Ni).

M-3106-88 Page 3 Examination of Boat Sample #3 Boat sample #3 was axially oriented as shown in Figure 8. Cuts were made to view two circumferential indications captured in the sample in the transverse direction as shown in Figure 9. After the first cut was made, both mating faces which would exhibit any flaw l

in the transverse cross section (this is the most favorable orien-tation to detect a crack or welding related problem such as lack of I fusion deft:t) were mounted and polished. Each face was examined at several different magnifications from 50x to 200x in both the polished and etched conditions. After each examination, the samples l were repolished and examined. Each polishing operation removed i I

approximately 1/16". This was done three times which means four dif- I ferent transverse planar sections through the sample were examined.

This represents sequential examination of approximately 3/8" along the direction transverse to the reflectors. No flaws were observed.

The weld metal exhibited a primary ferrite solidification mode.

Figure 10 is a montage of a cross section of boat sample M3. Ir the cross section shown, very large columnar grains can be seen. These grains have their major axis oriented in the same direction as the UT indications reported. The elongated columnar grains extend through many different weld passes. In one case, an elongated grain extended from approximately 0.08" below the surface of the weld to 0.345" beneath the surface. These large grains oriented parallel to the UT reflectors marked, appear to be the only possible cause for the erroneous indications.

Microhardness measurements were made at several different loca-tions. The average measured hardness in the base metal heat affected

M-3106-88

, .Page 4 zone (HAZ) converted to the Rockwell B Scale (Rb) ranged from 96 to

99. The first layer of weld metal ranged from 94 to 99 Rb, and 0.3" below the surface, the wald metal hardness was 95 to 99 Rb.

Various locations across the entire weld were qualitatively analyzed to determine the chemical composition. The analyses were performed in an SEM equipped with an EDS attachment. The results from all the locations indicated that the weld metal composition was similar to that of boat samples #1 and #2. In addition, a complete quantitative chemical analysis was performed. The results of the analysis are presented in Table 1. The composition of the weld metal sampled fit the ASME SFA 5.9 ER308L filler metal specification.

Discussion No defects were found in any of the three boat samples examined. The weld metal hardness and chemistry were acceptable.

The weld metal microstructure exhibited a primary ferrite solidifi-cation made in all areas examined, this structure is known to enhance i

the resistance to hot cracking problems. The only apparent reason for the erroneous UT reflectors is large columnar grains oriented 3 i

perpendicular to the curface. These grains could reflect the refracted L waves used in the ultrasonic inspections.

6 Approved by: )4f/V4 / _ e Reported by* % . x /A Copies to: N. yJ.Kalivianakis, 1230E w .. v ,y J. S. Abel, 35 FNW G. P. Wagner, 24 W LaSalle Bank

, D. L. Farrar, 1248E R. Bax, Quad Cities G. F. Spedl, Quad Cities G. J. Tagatz, Quad Cities R. J. Tamminga, 1535E I. Johnson, Nucl. Lic (2) 12.1 1886s

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ranged fron 0.35"-0.60" i beneath the OD surface. ,

1. 33-circumferential depth l ranged fron 0.24"-0.55" FORINFORMAD0N OWLY beneath the oD surface.

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1. 70-axial depth ranged from 0.55"-0.60" beneath Figure 1. Sket'ch showing the relative the OD surface.

position of the #1 boat sample in relation to the reflectors reported as contamination cracks by GE NDE inspectors.

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Indication Data

1. 69-axial depth ranging from 0.18"-

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utnocR Figure 5. Sketch of boat samples #1 and #2 showing their positions relative to UT reflectors.

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Figure 6 As received boat sample #2. This sample measured 3.724" long, 1.022" wide, and 0.73" deep. The lines on the sample mark areas which were cross sectioned.

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Reflector Data

1. 40-circumfere'ntial depth ranging from 0.28"-0.60" beneath the OD surface.

, #41-circumferential depth ranging from 0.19"-0.60" beneath the OD surface.

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Reflector Data

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Table 1 Chemical Analysis (l) of the Weld Metal Sample Boat Sample'#3 ASME SAE 5.9 ER308L Carbon 0.03 0.03 mar Manganese 2.18 1.0-2.5 Phosphorus 0.016 0.03 max Sulfur 0.005 0.03 max .

Silicon 0.44 0.30-0.65 Nickel 9.60 9.0-11.0 Chromium 20.14 19.5-22.0 Molybdenum 0.10 0.75 max Copper 0.05 0.75 max (1) All values are reported in weight percent.

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