ML18024B297
| ML18024B297 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 01/10/1980 |
| From: | Cooper R, Gray R OAK RIDGE NATIONAL LABORATORY |
| To: | |
| Shared Package | |
| ML18024B296 | List: |
| References | |
| RO-50-296-79-19, NUDOCS 8001310261 | |
| Download: ML18024B297 (56) | |
Text
RESULTS FROM METALLOGRAPllIC EXAMINATION OF A CORE SPRAY PIPING WELD FROM TVA'S BROWNS FERRY NUCLEAR PLANT UNIT 3 R. H. Cooper and R. J. Gray Metals and Ceramics Division OAK RIDGE NATIONAL LABORATORY Oak Ridge, Tennessee 37830
- Operated by Union Carbide Corporation for the U.S. Department of Energy under Contract W-7405-cng-26.
CONTENTS lo INTRODUCTION o o o o o o o ~ o o o o o e e o e o o o o o o
- 2. SAMPLE EXAMINATION . . . . . e e e . . . . . ~ . . . ~ . . ~ ~ 2 Initial Sample Preparation . . . . ~ ~ ~ 2 Sectioning and Preparation for Metallographic Examination ~ . 3 3 ~ RESULTS ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 3 4~ DISCUSSION ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 6 5 ~ CONCLUS ION ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 9 6~ REFERENCES ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 10
- 2. SAMPLE EXAMINATION Metallographic examinations were centered on that portion of the pipe that produced the indication during ultrasonic inspection. These efforts encompassed both light microscopy as well as scanning electron microscopy (SEM).
Initial Sample Preparation The 112-cm-long pipe section was initially removed from its unshielded shipping container and unwrapped in the High Radiation Examination Labora-tory (HRLEL) at the Oak Ridge National Laboratory. Smear checks on the outside contour were made for alpha radiation. The overall external radiation level associated with this pipe section was 350 millirem with the major portion of this being beta-gamma radiation. In view of this radiation level, personnel handling and subsequently sawing the piping section were carefully supervised by ORNL's health safety personnel. At this point, TVA personnel performed an additional ultrasonic inspection at ORNL to locate precisely the location of the indication prior to sectioning of the piping. From this information, a 7.7-cm-diam plug containing the area producing the indication waa removed using a hole saw. Because it was essential that the plug be removed intact, and without a guide hole, a perimeter guide for the saw was used, see Fig. 3. A portable magnetic base drill press, dedicated to machining operations associated with con-taminated materials, was used for this operation, Fig. 4 ~ The radioactivity emanating from the inside contour of the resulting plug sample was 400 millirem.
The 7.7-cm plug was subsequently ultrasonically inspected by a repre-sentativc of ORNL's nondestructive inspection group. This effort confirmed the source of the defect indication noted by TVA was contained in the 7.7-cm plug and the defect indication waa located at or near the root pass of the weld.
- 1. INTRODUCTION A 112-cm-long by 25-cm-diam stainless steel pipe from the Tennessee Valley Authority's Browns Ferry Nuclear Plant Unit 3 was delivered to Oak Ridge National Laboratory (ORNL) for metallographic examination. The pipe was part of the core spray piping system and contained a circumferential weld identified as DCS-3-18. The weld joined the core spray pipeline to the reactor vessel safe end. Figure 1 shows the appearance of the pipe 1 section as it was received at ORNL. Figure 2 indicates the location of the core spray piping relative to the reactor vessel including the design of the reactor nozzle, safe end, and core spray piping .
The core spray line is 25.5 cm schedule 80 welded pipe fabricated from type 304 stainless steel (ASTM A 358). The safe end appears to be a forging of type 316 stainless steel ~ The core spray piping to safe end joint is a multipass weld made with type 308 stainless steel filler material. TVA reported the environment associated with this piping section as nonflowing demineralized water at a temperature ranging from 60 to 270'C (140 to 520'F) and gage pressure ranging from 0 to 6.9 MPa (1000 psi) ~ TVA further indi-cated that there was no reason to suspect the environment seen by this pipe section had deviated from the range of environments typically experienced by the core spray piping in a BWR system.
This weld passed an initial ultrasonic inspection and since that time has received ultrasonic inspections at periodic intervals. The last such inspection revealed a linear indication on the inside of the pipe lying parallel to the weld for a length of 12 to 25 mm. Assuming the top of the pipe to be a 12 o'lock position, the indication was noted at a 1 o'lock I
position. The purpose of this examination was to determine the source of these ultrasonic indications.
2 ~ SAMPLE EXAMINATION Metallographic examinations were centered on that portion of the pipe
'that produced the indication during ultrasonic inspection. These efforts encompassed both light microscopy as well as scanning electron microscopy (SEM) ~
Initial Sample Preparation The 112-cm-long pipe section was initially removed from its unshielded shipping container and unwrapped in the High Radiation Examination Labora-tory (HRLEL) at the Oak Ridge National Laboratory. Smear checks on the outside contour were made for alpha radiation. The overall external radiation level associated with this pipe section was 350 millirem with the major portion of, this being beta-gamma radiation. In view of this radiation level, personnel handling and subsequently sawing the piping section were carefully supervised by ORNL's health safety personnel. At this point, TVA personnel performed an additional ultrasonic inspection at ORNL to locate precisely the location of the indication prior to sectioning of the piping. From this information, a 7.7-cm-diam plug containing the area producing the indication was removed using a hole saw. Because it was essential that the plug be removed intact, and without a guide hole, a perimeter guide for the saw was used, see Fig. 3. A portable magnetic base drill press, dedicated to machining operations associated with con-taminated materials, was used for this operation, Fig. 4 ~ The 'radioactivity emanating from the inside contour of the resulting plug sample was 400 millirem.
The 7.7-cm plug was subsequently ultrasonically inspected by a repre-sentative of ORNL's nondestructive inspection group. This effort confirmed the source of the defect indication noted by TVA was contained in the 7.7-cm plug and the defect indication was located at or near the root pass of the weld.
~,
Reference photographs were made of both the outer and inner surfaces of the plug, Fig. 5(a) and (b) respectively. Because the nondestructive tests isolated the indication to an area near the weld root, the interior surface of the sample was extensively evaluated using a low-power stereoscope.
Sectioning and Preparation for Metallographic Examination Observations made with the stereoscope indicated the probable existence of a crack running along the toe of the weld, on the inside surface, see Fig. 5(b). From this observation, the plug was ultimately sectioned into six samples identified as TVA-1,C-1, C-2, S-l, S-2, and ST. The location of these samples relative to the inside surface is illustrated in Fig. 6.
Sample C-1 is a metallographic sample mounted to reveal a cross section, of the weld and is coincident with the approximate midpoint of the crack.
The area designated as S-l was prepared for scanning electron microscopy (SEM) studies of the sample surface containing the crack. After the SEM examination of S-l, this sample was cut to provide samples S-2 and C-2.
Sample C-2 is a second cross-sectional'iew of the weld, located in an area where the crack appeared farthest from the toe of the weld. Sample S-2 was removed from S-1 and further sectioned, as shown in Fig. 7, to allow this sample to be broken apart for SEM evaluation of the fracture surface.
The sample designated as TVA-1 was made available to TVA personnel as an archive sample and as a source of material for chemical analysis of the base metals and weld metal. In addition to metallographic analysis, micro-hardness traverses were carried out on sample C-1 and sensitivity charac-terization using the ASTM h262-h oxalic acid procedure were carried out on sample ST. In passing, it should be noted that the radioactivity level of I
the individual specimens was approximately 10 millirem.
- 3. RESULTS Based on the observations made on the plug with stereoscopy, it was confirmed that the ultrasonic indication was the result of a crack. This
crack is located in the type 316 stainless steel safe end and is parallel to the root pass of the weld, see Fig. 8. Approximately half of the cracked length is located near the weld fusion line on the type 316 stainless steel side, while the remaining portion of the crack appears to be approximately 1 mm away from this area and appears as discontinuous cracks'n addition to showing the location of the crack, the bottom of this photomacrograph, Fig. 8, reveals a topography thought to be related to the weld joint prepa-ration. These surface contours are replaced by a surface roughness in the area, near the weld where the crack is situated. Examination of metallo-graphic samples C-1 and C-2 in these respective areas did not provide any clues regarding the source of this surface roughness.
In order to better interpret these observations, sample S-1 (see Fig. 6) was set up in such a way that the entire root weld pass area of this specimen (including the area later removed to make sample C-2 and S-2) could be examined with the scanning electron microscope . This area was contiguously inspected by initially indexing the SEM field of view on the cut edge located at the left side of the sample and subsequently indexing across the sample with consecutive fields until the entire weld root area had been examined.
Four selected fields from this evaluation were photographed, Fig. 9(a) through (d) ~ Their approximate locations on this sample are: the cut edge, 10.8, 16.7, and 21.6 mm from the edge, respectively. These relative locations have been identified in Fig. 6 as M-1 through M-4. These photomicrographs, Fig. 9(a) and (b), confirm that the crack runs along the fusion line near the left-hand edge of sample S-l, but moves away from this interface as one approaches the right aide of sample S-l. These observations would suggest that the crack terminates as it reaches the fusion zone of the weld.
As indicated'previously, sample S-2 was removed from the left side of S-l and was split open to allow SEM evaluation of the fracture surface, see Fig. 7. Three selected fields from this evaluation were photographed, Fig. 10.
These photomicrographs illustrate the topography of the fracture. surface near the interior pipe surface, mid-crack depth, and the bottom of the crack.
Evaluation of the area near the middle of the crack revealed a topography typical of intergranular fracture covered with areas of corrosion product.
This topography is representative of intergranular stress-corrosion cracking (IGSCC)o
N Analysis of the fracture area near the interior surface was also found to have features characteristic of intergranular fracture; however, this I
surface was covered with a thicker layer of corrosion product. Analyses of this SEM field indicates that in the same environment, a greater quantity of corrosion product has formed on the fracture surface than on the interior surface of the pipe. This observation suggests sensitization in the heat-l affected zone, resulting in the preferential at'tack of the grain boundaries ~~
The photomicrograph of the area near the end of the crack was included
'n I
Fig. 10 for completeness. This SEM field contains areas characteristic of intergranular fracture resulting from the propagation of the crack and a topography representative of ductile tearing. The latter area is a result of pulling the sample S-2 apart. In the transition area between these two topographies, one can identify apparent fatigue striations at higher magni-fications. Such indications could have resulted from handling sample S-2 prior to breaking it or from small in-service cyclic loads concentrated at the tip of the crack. Because striations are not seen elsewhere along the fracture surface, fatigue is not considered to be a significant factor in the propagation of this crack.
This cracking was further characterized by metallographic analysis of cro'ss sections of the wc.ld, specimens C-1 and C-2 ~ This analysis, indicated that the crack at these locations is approximately 22 mm deep or less than 15X of the thickness of the pipe (Figs. 11 and 12, respectively). An evalu-ation of the cracked area in both samples C-1 and C-2 at higher magnification, Fig. 13(a) and (b) and Fig. 14, respectively, confirm the SEM observations that the crack is intcrgranular and also shows significant branching.
l The location of mctallographic sample C-1 was selected at an area where the crack appears closest to the weld fusion line. Evaluation of this sample I
at higher magnification reveals that the crack intersects the surface at the toe of the weld, Fig. 13(a).
As indicated earlier, TVA had chemical analyses performed on the base metals and weld metals associated with the specimen identified as TVA in Fig. 6. The results of these analyses are summarized in Table 1. These analyses confirm that the base metals are types 304 and 316 stainless steels
and that the weld metal was type 308 stainless steel. No deviations from the normal range of either alloying and trace elements was noted ~ Because sensitization is known to play a large role in the cracking response of stainless steels in BWR piping applications, one should note that the carbon levels of both base metals and weld metal are sufficiently high to make these materials vulnerable to sensitization (0 058 to 0 059X)
~ ~ ~
In view of the role sensitization plays in the IGSCC phenomenon, a grain boundary sensitivity test, ASTM A262-A (oxalic acid procedure), was performed on a specimen similar to the one shown in Fig . 1 1 ~ Despite the reportedly limited responsiveness of the A262-A procedure to detect the vulnerability of austenitic stainless steels to IGSCC, this procedure appeared to be the most convenient method of obtaining some relative indi-cation of sensitivity in these materials within the time frame available for the testing and preparation of this analysis ~ The micros tructure resulting from the oxalic acid exposure for both the types 304 and 316 stainless steel materials, Fig. 15, indicated that only type 304 stainless steel was sensitized ~ In addition, this test revealed Neumann bands in the type 316 material, suggesting that this material had experienced plastic deformation. The results of this test confirmed the apparent inadequate responsiveness of the oxalic acid procedure reported by GE ~
The microhardness traverses of sample C-1 were carried out to complete the characterization of this core spray pipe to safe end weld'he results of these tests are summarized in Fig. 17 'nd indicate no deviations from expected results.
4e DISCUSSION In September 1974 the first of a series of cracks in austenitic stain-less steel BWR piping was found at the Dresden Nuclear Power Station.> As a results several committees and task groups were formed to categorize the available information regarding this cracking phenomenon and to recommend methods of mitigating the problem. As a result of these efforts, a list of major metallurgical characteristics associated with this phenomenon has been suggested ~ and includes the following:
0 Cracks typically run parallel to circumferential welds.
Cracking always initiates from the inside surface and propagate outward.
Cracks are associated with nonstabilized types 304 and 316 stainless steels.
I The cracks are coincident with sensitized material adjacent to welds.
Initiation always occurs near weld joints where residual stresses from welding plus the contribution of thermal gradients, secondary pressure effects, and design stresses result in accumulative stress levels exceeding the yield strength of the material in a localized area.
These cracks are the result of intergranular stress corrosion and appear as intergranular branched cracks.
The crack or cracks evaluated in this analysis were found to have the following significant features:
1 . This crack was located in the heat-affected zone of the circum-ferential core spray pipe to safe end weld DSC-3-18.
- 2. The material, type 316 stainless steel, is not stabilized and has a carbon level sufficiently high to make this alloy vulnerable to sensitization.
- 3. Metallographic and SEM analysis clearly document the intergranular and branched nature of this crack.
In addition to these points, it should be noted that the crack occurred in the 1 o'lock position. Approximately 40X of all core spray cracks have been located in this position.4 From past experience, a majority of cracks have been observed at joints that make a transition from larger to smaller diameters.4 hs indicated in Fig. 2, this is also the situation for the core spray pipe to safe end weld evaluated here. From these observations, it is concluded that the cracking observed in this pipe section was the result of the same generic IGSCC phenomenon observed in other BWR piping systems.
A cursory review of the QE Task Croup Report4 indicates that numerous cases of IGSCC have been noted in the core spray safe end materials, but few, 'if any, of the safe ends were reportedly fabricated from type 316
stainless steel. Many of these safe end materials were found to be furnace sensitized as a result of the postweld heat treatment of the pressure vessel.
The results of the ASTM A262-A test suggest that this was not the case for this type 316 stainless steel safe end. The GE Task Group also reports an apparent low incidence of IGSCC cracking in type 316 stainless steel; however, GE also points out this may be due to the small quantity of this material Used in BWR piping to determine the exact initiation site or a rationale for applications'fforts initiation were carried out in this analysis'ecause of the quantity of corrosion products on the inside pipe surface and on the fracture surfaces evaluated, Fig. 10, no clues regarding the point of initiation could be determined. Macroscopic examinations of metallographic samples C-1 and C-2, Figs. 11 and 12, provided an excellent opportunity to evaluate the quality of the multipass core spray to safe end weld'his visual observation suggests that this weld is sound and defect free. As a result, no unusually large weld defects such as cracks, laps, or porosity, are thought to have been a significant contributor to the initiation of this crack.
It is also interesting to review the crack propagation path into the pipe wall. At the location of metallographic sample C-l, Fig. 11, the crack is located at the toe of the weld, while 2 cm away the crack is 1 mm from the weld, Fig. 12. The GE report provides numerous examples of cracks that have propagated in this manner. In practically every case the GE report indicates that crack propagation is arrested when the crack enters the weld metal. Although the crack evaluated here appears to be following this pattern, neither the initiation nor the termination sites were identified'he results of the ASTM h262-h test showed sensitization in only the type 304 material. The fact that the crack occurred in the type 316 material further confirms the conclusions reported by GE that the h262-h procedure is not sufficiently responsive to detect the minimum level of sensitivity needed to initiate IGSCC.
As a result of this investigation, it was determined that the deepest crack penetration in the two areas examined was 15X of the 136-am-thick wall Even with this small depth of penetration, this crack was readily
0 detected by ultrasonic inspection techniques'n view of the current problem with IGSCC cracking in BWR piping systems, it is important to emphasize ultra-sonic inspection as a viable method of detecting cracks in their early stages and minimizing the potential of pipe leakage.
5 ~ CONCLUSION A metallurgical analysis has been completed on a weld between the core spray pipe (type 304 stainless steel) and the pressure vessel safe end (type 316 stainless steel) from the Browns Ferry Nuclear Plant Unit 3 ~
The purpose of this analysis was to identify the source and possible cause of the indication found during routine ultrasonic inspection of this piping section. This analysis revealed that the source of this indication was a crack that ran circumferentially for approximately 25 mm along the inside surface of the pipe. The crack was located in the 1 o'lock position of the pipe's inner wall and penetrated approximately 15X of the pipe's thickness of 136 raa. (This depth was measured in only two locations.)
This analysis did not identify a point of initiation for this crack.
Metallographic analysis of cross sections of the pipe and SEM evaluation of the fracture surface indicate that the fracture was totally intergranular and exhibited branching characteristics as it penetrated the wall, and was totally confined to the heat-affected zone of the weld. This morphology is indicative of IGSCC. Contrary to the presence of the fracture in the type 316 material, the ASTM h262-A (oxalic acid procedure) did not reveal indications of sensitivity in the type 316 materials This confirms the findings of others that the oxalic acid test procedure is not sufficiently responsive to detect the minimum level of sensitivity needed to initiate IGSCC in austenitic stainless the relatively small depth of penetration of this crack, it steels'espite should be emphasized that this defect was readily detected by ultrasonic inspection techniques.
10 6 ~ REFERENCES
- 1. "Standard Recommended Practices for Detecting Susceptibility to Inter-granular Attack in Stainless Steels," Designation A262, Annual Book of ASTM Standards, American Society for Testing and Materials, Philadelphia, 1976.
- 2. W. L. Walker, Comparison of Several Methods of Measurin the De ree of Sensitization of T e 304 Stainless Steel, NEDO-13342 (May 1973).
- 3. Pipe Cracking Study Group, Investigation and Evaluation of Crackin in Austenitic Stainless Steel Pi in of Boilin Water Reactor Plants, NUREG-75/067 (October 1975).
- 4. H. H. Klepfer et al ~ , Investi ation of Cause of Crackin in Austenitic Stainless Steel Pipin , Vol ~ 1, NEDO-21000-1 (July 1975).
Table 1. Summary of Chemical Analysis on Core Spray Pipe Section Element, wt X Sample C Mn P S Si Ni Cr Mo V Cb+Ta Ti Co Cu Al B N2 Type 316 SS 0.059 1.43 0.030 0 '12 0 '5 11.0 16.75 2 '3 0.03 >0 ~ Ol >0.01 0.26 0 '9 0.03 0.00 0.032 Weld Metal 0.053 1.75 0.031 0.008 0.40 9.43 20.50 0.09 0.07 >0.01 >0.01 0.15 0.02 0.030 Type 304 SS 0.058 1 ~ 74 0.032 0 '06 0.54 9.70 18.43 0.22 0.05 >0.01 0 '2 0.09 0 '0 0.01 0.00 0 '33
Y-167309 l ,
'I I
I 1
NELD Fig. 1. Photograph of the 112- by 25 ~ 5-cm As-Received Pipe Section Containing the Core Spray Pipe to Safe End Weld. This photograph was taken immediately after unpacking the pipe section in ORNL High Radiation Exami-nation Laboratory. Arrow shows location of a defect indication found by ultrasonic inspection.
Y-167166 CODE SPAAY PWE AEACTOD YE55EL ADD IIOZZLK SOAK SPIAY. ISA SOS CLA55 Z LOW AllOYSTEOI TYPICAL WKLD DCSO-15 SAfE EIIO CORE TYPE 5 IS STAIILESS 5TEEL COIE SPAAY PWIIO SPRAY TYPE SOS STAIILKSS STEEL LINE SECTION Of PPE EECKIYED AT OAIIL DETAIL OF CORE SPRAY TO SAFE END DESIGN Fig. 2. Drawing Illustrating the Relative Location of the Core Spray Pipe and Safe End to 'the Reactor Pressure Vessels A detailed drawing indi-cates the relative design of core spray pipe to safe end to reactor vessel joints'
l Y-1 673'f 0 Cz Fig. 3. Photograph of Guide Template Used for Removing the 7.7-cm Plug from Pipe Section with 7.7-cm Hole Saw.
Y-167311 6
il~ ~-
C
~4) qW t
~ e Fig. 4. Photograph of the Drill Press as it was set up to Remove the 7.7-cm-diam Plug from the Pipe Section.
Y.167316 1,'m
'(li 3 ~
i li (a)
(b)
}' }; . 5 . Pho tograph of the Exterior Surface ( a ) , and the Interior Su r fac e ( b ) , of the Core Spray Pipe to Safe End Weld ~ Ultrasonic testing revealed a defect indication in this area .
Y-167320
~~ ~ ., 1 I
I I
I I
I I
I CUT 2 Cm 3 Fig. 6. Interior Contour of the Core Spray Pipe to Safe End Weld, as Photographed in Fig. 5. The dashed lines show the location of saw cuts made to obtain samples TVA-1, C-l, C-2, S-l, S-2, and ST. Arrows M-1 through M-4 identify the relative location of the four SEM fields to be shown in Fig. 9.
Y-167339 316 SS 304SS
C Fig. 7. Photomacrograph of Sample C-1. The dashed lines show the location of saw cut made to obtain sample S-2. A load was subsequently applied at three points indicated by the arrows to break the sample for subsequent SEM evaluation of the fracture surface.
~ ~
Y-167343 1.27 col I;
(
'ls Fig. 8 ~ Photomacrograph of the Interior Surface of the Core Spray Pipe to Safe End Weld. The cracks are indicated with arrows.
Y-1 67314 I
t"w v re 0
O f
8 O
O Fig. 9. Four Selected Fields from the SEM Evaluation of the Cracked Area on the Inside Surface of the Core Pipe to Safe End Weld, Sample S-l.
0
~ ~
Y 157315
~WELD C '~
,p 0~ i~~s 0~
"gg.4,g 4s4 4S-'.
Q<< ~
I
-~gQ; 4 k
,~
I 1'l I
,~
il 4'p I
~ ~ 4 s dA' 'f.
%A 4 )j4 Oh
'06 aC44SS OOSO Fig. 10. Selected Fields from the SEM Evaluation of the Fractur'e Surface Exposed by Breaking Sample S-2.
~ ~
Y-1s7315
~WELD P
,~
'a)P
~
I 'I' Fig. 10. Selected Fields from the SEM Evaluation of the Fracture Surface Exposed by Breaking Sample S-2.
Y-167340 Fig. 12. Photomacrograph of Metallographic Sample C-2 ~ The crack is indicated with an arrow.
~ I ~
Y-1B7342 b
/ I ~
I 0
Y-O X
EOe Pn O
O O 8 Ol b
Fig. 13(a) and (b). Photomicrograph of Selected hreas of the Cracked Area from Sample C-l, see Fig. 11.
~ ~ 1 ~
0 Y-167342
/g+. A~ 'g; gP I
Y-
~
)
0 o 8 b
-Fig. 13(a) and (b): Photomicrograph of Selected hreas of the Cracked Area from Sample C-l, See Fig, 11
~ ~
Y-167341 O
~ ~ IV O
O 0 O
X Eos QIA '
D O CV 3
O Fig. 14. Photomicrograph of a Selected Area of the Cracked Area from Sample C-2, see Fig. 12 '
Y-167313 Fig. 15. Illustration of the Results of the AS'262-A Oxalic Acid Sensitization Test.
'r
~t fr
Y 167312 4 4177 189 4 4 162 16 202 166 167 TYPE 316 SS TYPE 304 SS 4 4 199 214 215 212 203 201 194 194 199 189 FRACTURE Fig. 16 'ummary of Microhardness Tests Performed on Sample C-l.
)
DISTRIBUTION D. F. Goetcheus (15 copies)
Tennessee Valley Authority 505 Edney Building Chattanooga, Tennessee 37401 R. J. Gray G. M. Adamson J. E. Cunningham J. R. Weir, Jr.
D. A. Canonico G. M. Slaughter R. H. Cooper R. K. Kibbe Patent Office Laboratory Records
P 4
1