X-RAY ANALYSIS OF CARBON IN 316 AUSTENITIC STAINLESS STEEL : RESULTS OF A GERMAN-FRENCH ROUND ROBIN TEST

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X-RAY ANALYSIS OF CARBON IN 316

AUSTENITIC STAINLESS STEEL : RESULTS OF A GERMAN-FRENCH ROUND ROBIN TEST

L. Meny, C. Walker, M. Champigny

To cite this version:

L. Meny, C. Walker, M. Champigny. X-RAY ANALYSIS OF CARBON IN 316 AUSTENITIC STAIN- LESS STEEL : RESULTS OF A GERMAN-FRENCH ROUND ROBIN TEST. Journal de Physique Colloques, 1984, 45 (C2), pp.C2-613-C2-616. �10.1051/jphyscol:19842143�. �jpa-00223814�

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JOURNAL DE PHYSIQUE

Colloque C2, supplément au n°2, Tome h5, février 1984 page C2-613

X-RAY ANALYSIS OF CARBON IN 316 AUSTENITIC STAINLESS STEEL : RESULTS OF A GERMAN-FRENCH ROUND ROBIN TEST

L. Meny, C.T. Walker* and M. Champigny

Departement de Technologie, Centre d'Etudes Nuoleaires de Saolay, 91191 Gif-sur-Ivette Cedex, Franae

^European Institute for Transuranium Elements, Postfaeh. 2866, 7500 Karlsruhe, F.R.G.

Résumé - Quatre échantillons d'"acier austénitique type 316 contenant entre 300 et 3000 ppm de carbone ont été analyses par huit laboratoires (trois en Allemagne, cinq en France). Les résultats montrent qu'une concentration de 0,2. % en poids de carbone peut être déterminée avec une précision relative

meilleure que +10 %, et que la limite de détection expérimentale du carbone dans un tel acier est d'environ 300 ppm.

A b s t r a c t - Four specimens of 316 a u s t e n i t i c s t a i n l e s s s t e e l with carbon c o n t e n t s between 300 t o 3000 ppm have been a n a l y s e d by e i g h t l a b o r a t o r i e s : t h r e e i n Germany and f i v e i n F r a n c e . The r e s u l t s show t h a t a carbon c o n c e n t r a t i o n of 0 . 2 wt^ can be determined with a p r e c i s i o n of b e t t e r than +10 % r e l a t i v e and t h a t t h e experimental l i m i t of d e t e c t i o n for carbon i n such a s t e e l i s about 300 ppm.

I - INTRODUCTION

Because the Mn2L£, the Cr2Lo<: and the Ni3Lo(. X-ray lines interfere with the CK line /1/, the analysis of carbon in stainless steel represents one of the most difficult problems facing the electron microanalyst.

In recent years there has been much debate about the limit of

detection for carbon in such steel and the precision with which this element can be measured. To clarify the situation, a group of

European microanalysts attending an ANRT meeting at Karlsruhe in 1981 decided to carry out a "round robin test".

II - PARTICIPANTS

H. Grubmeier (3), J. Ransch (if), C. Alvani (k), C.T. Walker (2), L. Meny (1), M. Champigny (1), R. Cytermann (5), M. Perrot (5), D. Benoit (6), P. Billou (6), G. Blanc (7), M. Grange (7) and M. Moncel (8).

(3) KFA-Julich, Institute fur Reaktorwerkstoff. Postfach 1913, 5170 Julich, Fed. Rep. Germany.

(4) Werkstoffinstitute Weissenfeld, Feldkirchener Str. 29, 8011 Weissenfeld, Fed. Rep. Germany.

(5) Departement de Technologie, Centre d'Etudes Nucleaires de Saclay, 91191, Gif-sur-Yvette, Cedex, France.

(6) IRSID BP No. 129, 78105 St. Germain en Laye, Cedex, France.

(7) Laboratoire de Microanalyse, Centre de Recherches, Ugine Aciers, 73400-Ugine, France.

(8) Longs-Metaux Qualite (LMQ), Sacilor-Sollac, BP No. 11, 57191- Florange, Cedex, France.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19842143

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JOURNAL DE PHYSIQUE

111

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EXPERIMENTAL

Four s p e c i m e n s o f 316 a u s t e n i t i c s t a i n l e s s s t e e l ( ~ r , 16.3 w t % ; N i , 14.0 wt%) w i t h homogeneous c a r b o n c o n t e n t s r a n g i n g from 300 t o 3000 ppm were a n a l y s e d i n e i g h t l a b o r a t o r i e s : t h r e e i n Germany and f i v e i n F r a n c e . The s p e c i m e n s were mounted t o g e t h e r i n a Bi-Sn a l l o y . A f i f t h specimen c o n t a i n i n g 70 ppm c a r b o n was i n c l u d e d f o r t h e

d e t e r m i n a t i o n o f t h e X-ray background. The l a b o r a t o r i e s were

i n s t r u c t e d n o t t o u s e diamond p a s t e o r e t h a n o l when r e f u r b i s h i n g t h e specimens.

T a b l e 1

-

A n a l y t i c a l C o n d i t i o n s

Parameter Laboratory

A B C 0 E El F FI G H

X-ray tahe-off angle (deg.) 18 18 40 40 40

Acceleration Potential (kV) 12 10 10 15 10

Beam Current (nA) 250 250 30 68" 150

Number of determinations 30 5 150 10 12

Counting Lime (s) 50 300 60 20 30

Area analysed b' bm2) 36 3 96 25 8

Standard Diamond Diamond Cr,, Cs -<I Diamond

ZAF Correction Ruste Rusie Blrks Ruste

Counter gas: Argon 90%. Methane 10%

Crystal. Lead Stearate.

a) Absorbed Current.

b) Derived using Castaings expression for electron spread.

C) Calibration curve constructed using Stainless Steel of known Carbon content

LO 40

10 10

150 100"

12 10

30 30

8 6

- 1 hamond

Ruste

40 40

10 10

100"' looa'

10 2

100 100

6 1

Diamond Ruste

18 10 240~'

18 I00

12 Oiamond

Ruste

The a n a l y t i c a l c o n d i t i o n s were n o t d i c t a t e d . It i s s e e n from t a b 1 8 1 t h a t t ~ o d i f f e r e n t i n s t r u m e n t s were u s e d (X-ray t a k e - o f f a n g l e , 18 and 40 ) and t h a t a c c e l e r a t i o n v o l t a g e s o f 10 12 and 15 kV were employed w i t h beam c u r r e n t s between 30 and 306 nA. To d e c r e a s e c a r b o n c o n t a m i n a t i o n a l l the l a b o r a t o r i e s u s e d a c o l d t r a p . I n two c a s e s (Labs. A and H! t h e c o l d t r a p was u s e d i n c o n j u n c t i o n w i t h a m i c r o - l e a k d e v i c e and i n two o t h e r s (Labs. F and G) i t was employed t o g e t h e r w i t h a r e f r i g e r a t e d b a f f l e above t h e d i f f u s i o n pump.

G e n e r a l l y , a diamond s t a n d a r d was f a v o u r e d , b u t o n e l a b o r a t o r y c h o s e C r C a n d t h r e e employed c a l i b r a t i o n c u r v e s . S i x o f t h e s e v e n l a g a r g t o r i e s t h a t worked w i t h a s t a n d a r d u s e d t h e c o r r e c t i o n pro- c e d u r e o f R u s t e /2/ w i t h t h e a b s o r p t i o n c o e f f i c i e n t s ( t a b l e 2 ) g i v e n by R u s t e and h i s co-workers /I-3/,

T a b l e 2

-

^Carbon^KA b s o r p t i o n C o e f f i c i e n t s

L a b o r a t o r y Absorber

Fe C r N i Mo

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I V

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RESULTS

The d i f f e r e n c e between t h e measured and t r u e c a r b o n c o n c e n t r a t i o n s a r e shown i n f i g . 1. It i s s e e n t h a t t h e h i g h e r t h e c a r b o n c o n t e n t o f t h e specimen, t h e s m a l l e r i s t h e s c a t t e r i n t h e r e s u l t s from t h e d i f f e r e n t l a b o r a t o r i e s . N e a r l y a l l t h e l a b o r a t o r i e s were a b l e t o measure 0.2 w t % c a r b o n w i t h a p r e c i s i o n o f b e t t e r t h a n 10 % r e l a t i v e . Where a c a l i b r a t i o n c u r v e was employed i n s t e a d o f a s t a n d a r d , t h e r e was l i t t l e d i f f e r e n c e i n t h e p r e c i s i o n . Moreover, t h e u s e o f a s u p p l e m e n t a r y a n t i c o n t a m i n a t i o n d e v i c e (oxygen j e t o r r e f r i g e r a t e d b a f f l e ) d i d n o t s i g n i f i c a n t l y improve t h e p r e c i s i o n o f t h e r e s u l t s

( c f . f i g , 1 and t a b l e 1). A s t o t h e a n a l y t i c a l p a r a m e t e r s ( a c c e l e r - a t i o n p o t e n t i a l , beam c u r r e n t , c o u n t i n g t i m e , e t c . ) t h e i r e f f e c t s on p r e c i s i o n c o u l d n o t be a s c e r t a i n e d .

1

A B C D E E l F F 1 G H A B C D E E ' F F ' G H

Fig. 1

-

D i f f e r e n c e between t h e measured and t r u e c a r b o n c o n c e n t r a t i o n s .

The r e s u l t s f o r 300 pprn c a r b o n ( f i g . 1 ) show a l a r g e s c a t t e r i n d i c a t - i n g t h a t t h i s c o n c e n t r a t i o n i s c l o s e t o t h e l i m i t o f d e t e c t i o n . I n t a b l e 3 t h e r e p o r t e d v a l u e s f o r t h e l i m i t o f d e t e c t i o n a r e compared vrith c a l c u l a t e d v a l u e s o b t a i n e d w i t h t h e e q u a t i o n s o f B i r k s /4/ and T i x i e r /5/. The r e p o r t e d v a l u e s r a n g e from 200 t o 450 ppm, w h e r e a s t h e c a l c u l a t e d v a l u e s c o v e r 90-990 ppm. The l a t t e r r a n g e i s g i v e n by t h e e q u a t i o n o f B i r k s /4/. T i x i e r ' s e q u a t i o n /5/ g i v e s a n a r r o w e r r a n g e o f 110

-

540 pprn v ~ h i c h i s i n b e t t e r agreement w i t h t h e s p r e a d o f t h e r e p o r t e d v a l u e s .

V

-

CONCLUSIONS

1. \!#%en t h e c a r b o n c o n c e n t r a t i o n o f a n a u s t e n i t i c s t a i n l e s s s t e e l e x c e e d s 1000 ppm, i t s a n a l y s i s by EPMA can be c a r r i e d o u t w i t h c o n f i d e n c e , p r o v i d e d t h a t t h e recommendations i n t h e l i t e r a t u r e a r e f o l l o w e d .

2. A c a r b o n c o n c e n t r a t i o n o f 2000 pprn can be d-etermined vaith a p r e c i s i o n o f b e t t e r t h a n 10 % r e l a t i v e .

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JOURNAL DE PHYSIQUE

T a b l e 3

-

L i m i t o f D e t e c t i o n

C a r b o n Concenlrotion. ppm.

Laboratory R e ~ o r t e d a f t e r Birks" a f t e r Tixier

''

--

d C,.

%;

=

::I

IRet4.19591

(

Fy

) . [ ~ ( I + ) " " T s p ~ ' * . C ~ t l ) ] [Ref 5. 19781 b1 Cmh= KT& 2 Tsp 13

F.correction factor, Cs~,corbon concenlration in standard: PSI, standard peak, 8.1. standard background; Trp. counting time specimen peok:

Bsp. specimen background; d s p . knawn constant introduced to lake account of differences in the counting lime for the specimen peok and background.

3, The p r e c i s i o n o b t a i n e d w i t h a c a l i b r a t i o n c u r v e i s s i m i l a r t o t h a t o b t a i n e d w i t h a s t a n d a r d .

4. With s h o r t c o u n t i n g t i m e s ( 4 5 min.), t h e p r e c i s i o n i s n o t s i g n i f i - c a n t l y improved by t h e u s e o f s u p p l e m e n t a r y a n t i c o n t a m i n a t i o n d e v i c e s .

5. The v a l u e o f t h e c a l c u l a t e d l i m i t o f d e t e c t i o n i s t o a l a r g e d e g r e e d e p e n d e n t on t h e e x p r e s s i o n c h o s e n and horn t h i s i s u s e d , 6. The e x p e r i m e n t a l l i m i t of d e t e c t i o n f o r c a r b o n i n a n a u s t e n i t i c

s t a i n l e s s s t e e l i s a b o u t 300 ppm.

R e f e r e n c e s

/1/ Coppola F!, Maurice F. and R u s t e J., Proc. 8 t h I n t . C o n g r e s s X-ray O p t l c s and M i c r o a n a l y s i - , , e i ~ . 7.?. Beamen, R.E. O g i l v i e and B.B. W i t t r y (Midland Mich., P e n d a l l CO.) 1980 581.

/2/ R u s t e J., J. Microsc. S p e c t r o s c . E l e c t r o n .

6

(1979) 123.

/3/ R u s t e J. and G a n t o i s M., J. Phys. D : ~ p p l . Phys. 8 ( 1 9 7 5 ) 872.

/4/ B i r k s L.S., E l e c t r o n P r o b e M i c r o a n a l y s i s . 2nd ed. (New York:

~ n t e r s c i e n c e ) 1971 112.

/5/ kncey M., B a s t e n a i r e F. and T i x i e r R., M i c r o a n a l y s i s a n d S c a n n i n g E l e c t r o n Microscopy, eds. F. M a u r i c e , L. Meny and R. T i x i e r

( O r s a y : L e s E d i t i o n s de p h y s i q u e ) 1979 319.

Erratum

L a b o r a t o r y E u s e d s t e e l s p e c i m e n s o f known c a r b o n c o n c e n t r a t i o n t o c o n s t r u c t t h e i r c a l i b r a t i o n c u r v e and n o t s t a i n l e s s s t e e l s p e c i m e n s a s i n d i c a t e d i n T a b l e 1.