THE

EFFECTS

OF

SAMPLE

THE

RESULTS

OF

SPECTRAL

COMPLEX OF

A

IRON-BASED COMBINED Yu. and

M. Z.

COMPOSITION

ON

ANALYSIS ALLOYS

BY

CHEMICO-SPECTRAL Buravlev, N. N. Khorol'skaya

I.

OF MEANS METHOD

Motrii,

UDC

543.42

Many p r o p e r t i e s of metals and alloys a r e d e t e r m i n e d by special features of the s t r u c t u r e , and by the chemical composition of thin s u r f a c e l a y e r s , and also by the composition and s t r u c t u r e of boundary zones of c r y s t a l l i t e s [1, 2]. Unfortunately, the absence of sufficiently reliable methods, capable of giving information on the changes in composition in such m i c r o - s p a c e s , has made it difficult to develop means of improving the exploitable p r o p e r t i e s of the alloys. The basic difficulty is a s s o c i a t e d with the very small thickness of the i n t e r c r y s t a l l i t e boundary regions (zones), which may v a r y in thickness f r o m a few hundred or a thousand atom l a y e r s to a few tens or a hundred m i c r o n s , depending on the composition and also on the c r y s t a l l i z a t i o n conditions in the t r e a t m e n t of the alloy. In consequence of the uneven relief of f r a c t u r e s , the use of local methods of layered s p e c t r a l analysis [,3, 4] does not always solve the problem, even with the use of e l e c t r i c sparking to s e l e c t the sample [5]. The combined c h e m i c o - s p e c t r a l method [8]* is of considerable value for analysis of the boundary regions of p o l y c r y s t a l l i n e metals and alloys at f r a c t u r e s , and also for the determination of the change in content of elements in thin s u r f a c e l a y e r s produced by oxidation, diffusion p r o c e s s e s , or internal a d s o r p tion phenomena [6, 7]. The method p r e s u m e s the availability of a nondestructive method of taking a sample [9, 10], together with a method for s p e c t r a l analysis of the resulting solution. It can be used not only under n o r m a l conditions but also under field conditions, for example, the s p e c t r a l method with sampling by an e l e c t r i c spark. It was shown p r e v i o u s l y [8] that the method could be used for simple and mediumalloy steels; s t r a i g h t - l i n e calibration curves were obtained for a number of elements over a wide enough concentration range. However, the possibilities of its use have still not been adequately investigated. In p a r t i c u l a r , in the analysis of complex alloys, e s p e e i a l l y w i t h a c i d - r e s i s t i n g alloys, h e a t - r e s i s t a n t alloys, e t c . , i r i s not c l e a r to what extent proportionality is observed between the concentrations of elements in the solid sample and t h e i r contents in solution. It would be expected, f r o m general c o n s i d e r a tions, that passivation or selective etching of individual elements might o c c u r during the dissolution of s i m i l a r alloys; this would lead to the a p p e a r a n c e of s y s t e m a t i c e r r o r s in the results of analysis. The cause of these e r r o r s might be a difference in the p r o c e s s of dissolution of the m a t e r i a l resulting f r o m a change in the alloy composition. Alternatively the e r r o r s might originate in the subsequent s p e c t r a l analysts of the solutions, f r o m the effects of "third" elements. Accordingly, it is important to investigate the special features of the use of the method under consideration for the analysis of complex alloys. The p r o duction of data in this field is also n e c e s s a r y for the development of methods of supression, or of methods of c o r r e c t i n g the analytical results for both the above f a c t o r s . The obiect of our work was to investigate the special features of the effects of sample composition on the results of the s p e c t r a l analysis of complex, i r o n - b a s e d alloys, when the combined c h e m i c o - s p e c t r a l method was used. *This method may be called the " c o m b i n e d ' as opposed to n o r m a l c h e m i c o - s p e c t r a l methods. T h e l a t t e r n o r m a l l y involve chemical t r e a t m e n t of the sample (concentration, t r a n s f o r m a t i o n into other compounds, etc.), which is then subjected to s p e c t r a l analysis. T r a n s l a t e d f r o m Zhurnal Prikladnoi Spektroskopii, Vol. 21, No. 4, pp. 587-592, October, 1974. Original a r t i c l e submitted November 29, 1973. 9 76 Plenum Publishing Corporation, 22 7 West 17th Street, New York, N. Y. 10011. No part o f this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, microfilming, recording or otherwise, without written permission o f the publisher. A copy o f this article is available from the publisher for $15.00.

1283

The m a t e r i a l s u s e d f o r i n v e s t i g a t i o n w e r e the s t a n d a r d s of s e t s 31, 96, and 104. All t h r e e g r o u p s of a l l o y s had a p p r o x i m a t e l y the s a m e c o n c e n t r a t i o n i n t e r v a l s for m a n g a n e s e and s i l i c o n . The s t a n d a r d s of s e t 104 w e r e denoted as for the s p e c t r a l a n a l y s i s of plain s t e e l s ; it had been shown e a r l i e r that when the c o m b i n e d c h e m i c o - s p e c t r a l method was used, such e l e m e n t s as m a n g a n e s e , s i l i c o n , and o t h e r s t r a n s f e r r e d to the s o l u t i o n p r o p o r t i o n a t e l y to t h e i r contents in the s o l i d s a m p l e s [8]. Consequently, s i m u l t a neous r e c o r d i n g of the s p e c t r a of s o l u t i o n s of a l l t h r e e g r o u p s of a l l o y s e n a b l e d us to e s t i m a t e the concent r a t i o n s e n s i t i v i t i e s of s i l i c o n and m a n g a n e s e in h i g h - a l l o y , c h r o m e - - n i c k e l a l l o y s ( s t a n d a r d s of s e t s 96 and 31). This e s t i m a t i o n was c a r r i e d out by c o m p a r i n g the s l o p e s of the c o r r e s p o n d i n g c a l i b r a t i o n c u r v e s with the s l o p e s of the c u r v e s f o r the d e t e r m i n a t i o n of t h e s e e l e m e n t s in c a r b o n s t e e l s . The method f o r inv e s t i g a t i n g the e f f e c t s of " t h i r d " e l e m e n t s on the r e s u l t s of the a n a l y s i s of c o m p l e x a l l o y s involved a c o m p a r i s o n of the mutual d i s p o s i t i o n of the c a l i b r a t i o n c u r v e s f o r the d e t e r m i n a t i o n of m a g n a n e s e , s i l i c o n , t i t a n i u m , and a l u m i n u m . By this c o m p a r i s o n of the c u r v e s for the d e t e r m i n a t i o n of m a n g a n e s e and s i l i c o n in a l l o y s of s e t 104 with the c u r v e s f o r the two o t h e r s e t s , we w e r e a b l e to e s t a b l i s h the s i m u l t a n e o u s effects of high c o n c e n t r a t i o n s of c h r o m i u m (4 to 14%) and n i c k e l (17 to 43%), m o d e r a t e c o n c e n t r a t i o n s of t i t a n i u m (1 to 4%), and low c o n c e n t r a t i o n s of a l u m i n u m (0.3 to 1.2%). M o r e o v e r , a p p r a i s a l of the mutual d i s p o s i t i o n of the c u r v e s f o r d e t e r m i n a t i o n of m a n g a n e s e , s i l i c o n , t i t a n i u m , and a l u m i n u m , obtained using only s t a n d a r d s of s e t s 96 and 31, m a d e it p o s s i b l e to c o n s i d e r the effect of a p p r o x i m a t e l y doubling the n i c k e l c o n c e n t r a t i o n (about 20% in one g r o u p and 40% in the o t h e r ) . Each point on the g r a p h s was plotted on the b a s i s of the m e a n of 5 to 6 s p e c t r o g r a m s , which e n s u r e d a p r e c i s i o n of about 4 to 5% r e l a t i v e (the r o o t m e a n s q u a r e e r r o r of a s i n g l e m e a s u r e m e n t was 10 to 12% r e l a t i v e } . The e f f e c t s of e l e m e n t s w e r e t a k e n as s i g n i f i c a n t if the s y s t e m a t i c d i s c r e p a n c i e s between the c o r r e s p o n d i n g c a l i b r a t i o n c u r v e s e x c e e d e d the " t h r e e s i g m a " c r i t e r i o n . Since the c o n s i d e r a b l e a l l o y i n g of a l l o y s of the l a s t two g r o u p s led to a s i g n i f i c a n t change in the i r o n content, the c a l i b r a t i o n c u r v e s w e r e c o n s t r u c t e d with a l l o w a n c e for dilution of the a l l o y b a s e . The n o n d e s t r u c t i v e method of taking a s a m p l e has been d e s c r i b e d in d e t a i l [8]. The g i s t of the m e t h od is to t a k e a s a m p l e f r o m the s u r f a c e u n d e r i n v e s t i g a t i o n by m e a n s of d i s s o l u t i o n . This was done by a p plying a d r o p of s o l v e n t to a c l e a n e d a r e a of the s u r f a c e , bounded by m o l t e n p a r a f f i n . Aqua r e g i a was taken as s o l v e n t f o r a l l the a l l o y s i n v e s t i g a t e d . The etching t i m e amounted to 30 min, at a t e m p e r a t u r e of 18~ Subsequently, when the d i s s o l u t i o n p r o c e s s was c o m p l e t e d , the s o l u t i o n was t r a n s f e r r e d to a m e a s u r i n g c y l i n d e r , the s u r f a c e was w a s h e d with a few d r o p s of d i s t i l l e d w a t e r which w e r e added to the m e a s u r i n g c y l i n d e r , and the v o l u m e was m a d e up to 1 m l . The s p e c t r o g r a p h i c i n v e s t i g a t i o n s of the r e s u l t i n g s o l u t i o n s w e r e c a r r i e d out by a r c excitation; s o m e 5 d r o p s of s o l u t i o n w e r e a p p l i e d to the ends of c a r b o n e l e c t r o d e s , which w e r e then heated to 80 to 90~ to r e m o v e the s o l v e n t . The a p p a r a t u s used was an I S P - 3 0 s p e c t r o g r a p h with an i n t e r m e d i a t e c o n d e n s e r s y s t e m , a s p e c t r o g r a p h i c s l i t width of 18 #, an a r c g e n e r a t o r ( c u r r e n t 3 to 4 A), and an M F - 2 m i c r o p h o t o m e t e r . The photog r a p h i c p l a t e s w e r e of t y p e III, of s e n s i t i v i t y 6 A l l - U n i o n State Standard units, the r e c o r d i n g t i m e f o r the s p e c t r a was 60 s e c , and t h e r e was no p r e b u r n . The data obtained (see Fig. l a ) e n a b l e d us to note the following p o i n t s . F i r s t of all the good mutual d i s t r i b u t i o n of the c o r r e s p o n d i n g points on the c a l i b r a t i o n c u r v e s , the r e c t i l i n e a r i t y of the l a t t e r o v e r the r a n g e of c o n c e n t r a t i o n u n d e r c o n s i d e r a t i o n , and a l s o t h e i r s a t i s f a c t o r y s l o p e s i n d i c a t e d that m a n g a n e s e and s i l i c o n w e r e t r a n s f e r r e d to the s o l u t i o n p r o p o r t i o n a t e l y to t h e i r i n i t i a l contents in the s o l i d s a m p l e s . This was a v e r y i m p o r t a n t f e a t u r e , pointing to the p r o s p e c t s of the u s e of the combined c h e m i c o - s p e c t r a l method for the a n a l y s i s of c o m p l e x a l l o y s . The effects of " t h i r d " e l e m e n t s showed up in the d e t e r m i n a t i o n of v a r i o u s e l e m e n t s . F o r e x a m p l e , in the d e t e r m i n a t i o n of s i l i c o n , the s y s t e m a t i c d i s c r e p a n c i e s between the c a l i b r a t i o n c u r v e s for s t a n d a r d s of s e t 104 on the one hand, and for s t a n d a r d s of s e t s 31 and 96 on the o t h e r hand, amounted to 30 to 40% r e l a t i v e . The extent of this effect was l e s s only if the mutual d i s t r i b u t i o n s of the two l a t t e r s e t s w e r e c o n s i d e r e d (10 to 15% r e l a t i v e , or z e r o in the c o n c e n t r a t i o n r a n g e s w h e r e the c u r v e s i n t e r s e c t e d } . In the c a s e of m a n g a n e s e d e t e r m i n a t i o n the d i s c r e p a n c y between the c u r v e s for s i m p l e and h i g h - a l l o y s t e e l s a l s o depended on the r a n g e of c o n c e n t r a t i o n d e t e r m i n e d ~ the c u r v e s f o r the a l l o y s t e e l s w e r e s y s t e m a t i c a l l y d i s p l a c e d d o w n w a r d s , With a m a x i m u m d i s p l a c e m e n t of 100 to 150% r e l a t i v e . A p p r o x i m a t e l y the s a m e d i s p l a c e m e n t s w e r e o b s e r v e d f o r the d e t e r m i n a t i o n of t i t a n i u m . In the c a s e of a l u m i n u m , the s y s t e m a t i c d i s c r e p a n c i e s between the c u r v e s , c o n s t r u c t e d by r e c o r d i n g the s p e c t r a of s t a n d a r d s of s e t s 31 and 96, w e r e c o n s i d e r a b l y l e s s than this, amounting to 20 to 25% r e l a t i v e . Thus, u n d e r o t h e r w i s e s i m i l a r

1284

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F i g . 1. C a l i b r a t i o n c u r v e s f o r t h e d e t e r m i n a t i o n of I) s i l i c o n , II) m a n g a n e s e , III) t i t a n i u m , and IV} a l u m i n u m , o b t a i n e d a) with n o n d e s t r u c t i v e s a m p l i n g , b) with c o m p l e t e d i s s o l u t i o n of t h e s a m p l e , and e) by r e g i s t e r i n g t h e s p e c t r a of m o n o l i t h i c s a m p l e s . I) Si 288.1 n m - - F e 288.0 nm, II) Mn 293.9 n m - - F e 294.4 nm, IID Ti 308.8 n m - - F e 309.8 rim, and IV) AI 308.2 n m - - F e 308.3 n m . 1), 2), and 3) a r e t h e s t a n d a r d s of s e t s 31, 96, and 104 r e s p e c t i v e l y .

c o n d i t i o n s , t h e e f f e c t s of t h e " t h i r d " e l e m e n t s d e p e n d e d on t h e p r o p e r t i e s of t h e e l e m e n t to be d e t e r m i n e d , i t s c o n c e n t r a t i o n r a n g e , and a l s o on t h e a l l o y c o m p o s i t i o n . In c o n s i d e r i n g t h e q u e s t i o n of t h e b a s i c r e a s o n s c o r r e s p o n d i n g to t h e p r o d u c t i o n of s y s t e m a t i c e r r o r s , it w a s n e c e s s a r y to a v o i d c o m p l e t e l y a n y f r a c t i o n a l s e p a r a t i o n of i n d i v i d u a l e l e m e n t s by d i s s o l u t i o n d u r i n g t h e e t c h i n g of t h e s a m p l e . F o r t h i s p u r p o s e we c a r r i e d out e x p e r i m e n t s with c o m p l e t e d i s s o l u t i o n of a p p r o p r i a t e q u a n t i t i e s of t u r n i n g s of t h e a l l o y s c o n c e r n e d . S o m e 0.4 g of t u r n i n g s , w e i g h e d to a p r e c i s i o n of 0.0002 g on a n a n a l y t i c a l b a l a n c e , w a s d i s s o l v e d by h e a t i n g in a q u a r e g i a t o g i v e a t o t a l v o l u m e of 25 m l [it w a s c a l c u l a t e d t h a t a p p r o x i m a t e l y t h e s a m e p r o p o r t i o n of s t e e l s a m p l e d i s s o l v e d in the a p p l i e d d r o p of s o l v e n t when t h e n o n d e s t r u c t i v e m e t h o d w a s u s e d u n d e r t h e c o n d i t i o n s d e s c r i b e d a b o v e ] .

1285

The undissolved p a r t i c l e s were decomposed by boiling. We then r e c o r d e d the s p e c t r a of the resulting solutions, using the s a m e method of application to the ends of carbon e l e c t r o d e s . C o m p a r i s o n of the data obtained ( F i g . l b ) with the picture for the effects of "third" elements in the nondestructive method (Fig. l a ) showed considerable s i m i l a r i t i e s with the mutual disposition of curves for the d e t e r m i n a t i o n of silicon, manganese, titanium, and aluminum. If, in the course of nondestructive sampling, the effects of "third" elements had led to selective dissolution of individual elements and iron, we would have expected a considerable difference in the analytical r e s u l t s as compared with the variant involving complete dissolution of turnings. Accordingly, the fact that the s y s t e m a t i c d i s c r e p a n c i e s between the curves did not d e c r e a s e significantly when the method of complete dissolution of the sample was used, led to the conclusion that p r o c e s s e s of selective dissolution of individual elements and iron did not o c c u r significantly when the method of nondestructive sampling was used. Simultaneous examination of figures a and b (of Fig. 1) with the data of figure c (Fig. 1), obtained by s p e c t r a l analysis of monolithic s a m p l e s of the above sets of s t a n d a r d s (by a r c excitation, with the s a m e p a r a m e t e r s , and a s p e c t r a l r e cording time of 15 sec without preburn), led us to conclude that the disposition of the curves was p r e s e r v e d . This also showed that when the analysis was c a r r i e d out by the combined c h e m i e o - s p e c t r a l method under the conditions d e s c r i b e d above, the essential f a c t o r contributing to the s y s t e m a t i c e r r o r was the effect of sample composition on the p r o c e s s at the electrode and not the effect on the dissolution p r o c e s s , even when the s p e c t r a l analysis of solutions was c a r r i e d out. It was shown p r e v i o u s l y [11] that in s p e c t r a l analysis of monolithic standards of the above sets with a vacuum quantometer, the points c o r r e s p o n d i n g to samples of all groups of alloys could be s a t i s f a c t o r i l y i n c o r p o r a t e d on c o m m o n c u r v e s . F r o m this it follows that when the specific conditions for the quantom e t r i c method were used (analysis in an a t m o s p h e r e of purified argon, with a low-voltage s p a r k s o u r c e , and the s a m p l e as cathode), the effects of "third" elements w e r e inconsiderable. This c i r c u m s t a n c e p r o vided a basis for supposing that by the use of improved methods of analysis of solutions, we might cons i d e r a b l y reduce the effects of "third" elements which were observed in our work. In fact, our method for the analysis of solutions essentially involved a p r o c e d u r e for analysis of the d r y salt residue on the e l e c t r o d e s after evaporation of the solvent. It is well known that with this method t h e r e is n o r m a l l y c o n s i d e r a b l e development of electrode p r o c e s s e s , leading to fractional evaporation, which i n c r e a s e s t h e e f f e c t s on the analytical r e s u l t s of the chemical and m o l e c u l a r composition of the sample. Accordingly, we a r e extending our investigation to the use of other methods for introducing the s a m p l e into the d i s c h a r g e : the fulgurator method, a rotating graphite disc, sputtering, etc. It is known that these substantially reduce the effects of "third" elements, or s u p p r e s s them altogether. In conclusion, it should be noted that the method proposed is not intended for the r e p l a c e m e n t of a n u m b e r of other methods (electric s p a r k sampling, l a s e r analysis, some methods for local layered analy s i s , e t c . ) , b u t c a n be used in a n u m b e r of cases as a supplement and for f u r t h e r development. LITERATURE

1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

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CITED

Ya. S. Umanskii; B. N. Finkel'shtein, and M. E. Blanter, The Physical Principles of the Science of Metals [in Russian], Metallurgizdat (1949). K . I . Kashchenko, P r i n c i p l e s of Physical Metallurgy [in Russian], Metallurgizdat (1962). N . G . Isaev, Zavod. Lab., 10, 1010 (1949); Izv. Akad. Nauk SSSR, Set. Fiz., 5, 689 (1950). N . V . Korolev, V. V. Ryukhin, and S. A. Gorbunov, E m i s s i o n Spectral Microanalysis [in Russian], Leningrad, Mashinostroenie (1971). K . I . Taganov, The Spectral Analysis of Metals and Alloys with P r e l i m i n a r y Sampling [in Russian], Moscow, Metallurgiya (1968). V . I . A r k h a r o v , T r u d y Instituta Fiziki Metallov, Akad. Nauk SSSR, No. 20, 201 (1957). E. Zh. Glikman and R. E. B r u v e r , The P h y s i c s of Metals, No. 43 [in Russian], Kiev, Naukova Dumka (1972), p. 42. Yu. M. Buravlev, A. M. Gaisinskaya, Z. F. Antonova, and L. N. Babanskaya, Zh. Analiticheskoi Khim., 26, No. 9, 1702 (1971). N . A . Tananaev, A Nondestructive Method for the Analysis of F e r r o u s , Nonferrous, and P r e c i o u s Metals [in Russian], Metallurgizdat (1948). A . G . Loshkarev, Collection, Investigations in the Field of Analytical C h e m i s t r y [in Russian], Sverdlovsk, Sverdlovskogo Gornogo Instituta ~1960), p. 3. Yu. M. Buravlev, The Effects of the Composition and Dimensions of the Sample on the Results of the Spectral Analysis of Alloys [in Russian], Kiev, Tekhnika (1970).