SEM-EDAX and optical microscopy investigations of sparked-in spots on AES analyzed steel FLORINA VIOLETA ANGHELINA, ION V. POPESCU,VASILE BRATU, ELENA STOIAN Department: Faculty of Materials Engineering,Mecathronics and Robotics, University: Valahia of Targoviste Address: Bd. Carol I, Nr. 2, 130024, Targoviste, Dambovita, COUNTRY: ROMANIA rectorat@valahia.ro,vianghelina@yahoo.com http://www.valahia.ro Abstract: In the context of quality assurance of test results SDAR-OES for stainless steels, the present work discuss the aspects of lightning spark of interaction with the sample. The investigations was made by optical and electronic scanning microscopy with EDAX. Key-Words: Scanning electron microscopy with EDAX, stainless steels AISI 316, AES, sparked spots, SDAR-OES. 1 Introduction Atomic emission spectroscopy (AES) is today the backbone of chemical analysis for the identification; specification and process control in virtually all branches of the metallurgical industry [1].During the researches concerning the contribution estimation of the influence factors to the AES uncertainty budget the authors fund out that burned area morphology bring new evidences on the sparking process. Thus, the classical AES sparking pattern depicted by Slickers [1, 4, 6, 7] and quite identical adopted in other representative papers [8÷10] seems to fail ignorring that the gap state during sample sparking could not be discribed as a plasma. The same, the extended ussage of temperature concept in their pattern is wrong as priviously was clear shown by L.B.Loeb[11] and subsecvently underlined by J.P.Walters[2]. Acctualy, there are strong evidences, from other AES close research domains, that sparking consists of individual breakdown chanels that branches and some of them could attain the streamer stadius.[12÷15]. In this vein we where supprise to note that the spark-in spots on an AISI 316 grade reveal proofs on latest streamer striking into the local melted sample surface as well as on unmelted or even „virgin” places. Besides, the inclusions seems to be ejected from burned area beiing partialy vaporised. The optical and scanning electron microscope (SEM) images bring valuable information on sparking-in process that spred a new light on it. 2 Problem Formulation Investigations were performed on a representative sample of AISI 316 grade. SDAR-OES tests were made with a Foundry-Master spectrometer having the following characteristics: Paschen-Runge optic with 140-500 nm wavelength range; spark discharge source of 500V at 450 Hz rate; Ar purged stand; tungsten counter-electrod washed with argon; evacuated optics. The microstructure of samples was investigated by a REICHERT optical microscope equipped with an automatic line for image acquisition and processing. The SEM-EDAX investigations were done with a XL- 30-ESEM TMP microscope. Buhler and MLG 11 equipments were used for specific sample surface finishing needed for microscopical investigations and for SDAR-OES analysis. The AISI 316 cylindrical sample of 40 mm in diameter was ten times spectrochemical tested in repetitive conditions to assess its elemental composition and the standard uncertainty of mass concentration. The standard uncertainty is estimated by the experimental standard deviation (STDEV) calculated as is specified in SR EN 130005:2005. We consider that relative experimental standard deviation (RSD) is more relevant for experimentalists. Table 1 shows the average elemental mass concentrations <c> and the associated STDEVs and RSDs. Proceedings of the 9th WSEAS International Conference on APPLICATIONS of ELECTRICAL ENGINEERING ISSN: 1790-2769 175 ISBN: 978-960-474-171-7