Concentration profiles through thin oxide scales by ion-probe microanalysis
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EXPERIMENTAL
TECHNIQUE
The materials examined were 0.0127 by 0.0127 by 0.0041 m coupons of Ni-22 wt pct Cr-2 vol pct ThOz (TDNiCr)* and Ni-20 wt pct Cr-3 vol pct Y~)3 which *FansteelMetallurgicalCorporationtradename. had been oxidized for v a r i o u s t i m e s up to 1.8 x 105 s at 1273 and 1 3 7 3 K i n 1.33 x 1 0 4 N / m 2 0 , o r in one c a s e , 1.01 x 105 N / m 2 a i r , a c c o r d i n g to a p r o c e d u r e d e s c r i b e d p r e v i o u s l y .4 The s c a l e s on t h e s e a l l o y s a r e in g e n e r a l v e r y p r o t e c t i v e (adherent and slow growing), so that after the oxidation t r e a t m e n t s given h e r e the oxide t h i c k n e s s e s do not exceed 1.0 p m . The oxidized s p e c i m e n s w e r e e x a m i n e d in the i o n probe m i c r o a n a l y z e r in plan with no f u r t h e r p r e p a r a tion a f t e r oxidation other than a v a p o r - d e p o s i t e d c o a t I. G. WRIGHTand M. S. SELTZER are Senior Scientist and Fellow, respectively, High Temperature Materials and Processes Division,Metal Science Group, Battelle-ColumbusLaboratories, Columbus, Ohio 43201. Manuscript submitted August 21, 1972. METALLURGICALTRANSACTIONS
ing of gold to m i n i m i z e charge b u i l d - u p . The depths of the holes d r i l l e d by the ion b e a m w e r e m e a s u r e d u s i n g a T a l y s u r f IV, and the oxide t h i c k n e s s e s by s u b s e q u e n t conventional m e t a l l o g r a p h i c t e c h n i q u e s . The i n s t r u m e n t used to m e a s u r e the c o n c e n t r a t i o n p r o f i l e s was a C a m e c a IMS-300 Ion M i c r o a n a l y z e r . In s i m p l e t e r m s , the Ion M i c r o a n a l y z e r u s e s a f o c u s s e d b e a m of i o n s , in this case p r e d o m i n a n t e l y 20+6 a c c e l e r a t e d to 11 kV, to s p u t t e r away the s u r f a c e of the s p e c i m e n being profiled. Since the oxides p r e s e n t on the s p e c i m e n s w e r e poor e l e c t r i c a l c o n d u c t o r s the t e c h n i q u e s of p r i m a r y b e a m s c a n n i n g and cyclic m a s s a n a l y s i s w e r e c o m b i n e d to d e t e r m i n e the p r o f i l e s . By cycling the m a s s s p e c t r o m e t e r o v e r s h o r t r a n g e s (15 to 20 at. m a s s units) e v e r y 20 s it was p o s s i b l e to cons t r u c t a detailed depth p r o f i l e for all e l e m e n t s of i n t e r est. In the case of the t h o r i a - c o n t a i n i n g alloy, for i n s t a n c e , two a d j a c e n t holes w e r e d r i l l e d in the s c a l e : for the f i r s t hole m a s s n u m b e r s 54 to 66 w e r e m o n i t o r e d + and CrO+6), and (for s p e c i e s C r + 54, Mn+5, Fe+6, N i + 58, Cu63 for the second, m a s s n u m b e r s 232 (Th +) and 248 (ThO +) were monitored. By u s i n g an a p p r o x i m a t e l y 200 p m d i a m . p r i m a r y 20 + b e a m and s c a n n i n g it over a s q u a r e a r e a a p p r o x i m a t e l y 400 p m on a side, n e a r l y f l a t - b o t t o m e d c r a t e r s w e r e p r o d u c e d over a s q u a r e a r
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