Raman imaging for surface characterisation of annealed electrical steel surfaces

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1 Phy. Sttu Solidi A 211, No. 6, (2014) / DOI /p Prt of Specil Iue on Engineering of Functionl Interfce Rmn imging for urfce chrcterition of nneled electricl teel urfce Crin Hmbrock 1,2, Kriztin Vincze-Miny 3, Sbine Hild 3, nd Achim Wlter Hel *,1,4 1 Intitute for Chemicl Technology of Inorgnic Mteril, Johnne Kepler Univerity Linz, Altenberger Str. 69, 4040 Linz, Autri 2 Voetlpine Sthl GmbH, Reerch & Development, voetlpine-strße 3, 4020 Linz, Autri 3 Intitute for Polymer Science, Johnne Kepler Univerity Linz, Altenberger Str. 69, 4040 Linz, Autri 4 Chritin Doppler Lbortory for Combintoril Oxide Chemitry t the Intitute for Chemicl Technology of Inorgnic Mteril, Johnne Kepler Univerity Linz, Altenberger Str. 69, 4040 Linz, Autri Received 4 September 2013, revied 17 Februry 2014, ccepted 7 Mrch 2014 Publihed online 25 April 2014 Keyword nneling, energy diperive X-ry pectrocopy, Rmn imging, teel, X-ry photoelectron pectrocopy * Correponding uthor: e-mil [email protected], Phone: þ , Fx: þ phyic ttu olidi ppliction nd mteril cience Rmn pectrocopy i powerful tool in the determintion of biologicl nd polymeric mple. However, lo the ue of Rmn pectrocopy for inorgnic ppliction like for the determintion of different iron oxide fter pecific corroion experiment or meteorite compoition i common. In thi work, the method of Rmn imging h been ued for urfce chrcterition of high temperture long-term nneled teel mple function of the dew point of the nneling tmophere. The invetigtion reveled tht t high dew point, oxide (Al 2 O 3, SiO 2 ), ilicte (Fe 2 SiO 4 ) nd pinel phe (Fe 2 SiO 4 -pinel) could be identified by Rmn imging where t low dew point the rectivity of luminium with nitrogen nd oxygen w preferred nd the phe of luminium nitride (AlN) well ome luminium oxide (Al 2 O 3 ) could be detected. The Rmn imging w upported by EDX mpping to obtin the elementl compoition of the urfce nd by XPS meurement to get n inight into the bonding tte of the element which both confirmed the reult obtined vi Rmn imging. 1 Introduction Rmn pectrocopy w introduced in the 1960 nd mny dvntge nd propect hve been evluted ince then. Tody, Rmn pectrocopy cn be ued in mny different field of ppliction, like for biologicl, polymeric or inorgnic ubtnce. A chrcterition of compound by ex itu meurement fter the tril [1, 2] nd mechnitic tudy of behviour in pecific environment by in itu meurement [3, 4] re min ubject tht re decribed vi Rmn pectrocopy. For inorgnic ubtnce, the comprehenion of corroion mechnim on rcheologicl rtefct [5 7] nd the tructurl chnge or the ctive ite during ctlytic ctivity [4, 8 10] on the one hnd nd the chrcterition of the compound formed in pecific environment, uch different iron (hydro-)oxide fter expoure to lty oil [11, 12], chloride olution [3], high temperture [13] or fter contct with liquid metl like zinc [14] on the other hnd re necery to be known for complete undertnding of the mechnim. There re mny dvntge of Rmn pectrocopy, e.g. tht no mple preprtion i necery before the meurement nd tht the method i non-detructive [15]. The min dvntge i it high opticl reolution becue monochromtic light (ler) i ued for excittion. The combintion with confocl microcope mke it poible to reduce bckground ignl, to provide n enhnced contrt nd t the me time to decree the cquiition time of individul pectr [16]. The ft cquiition of pectr nd the enhnced enitivity re epecilly ueful when performing Rmn imging. With thi method it i poible to obtin ditribution mpping of different phe [5 6, 17] nd lo emi-quntittive reult of different compound by clcultion [5, 18]. Rmn imging therefore combine the dvntge of identifiction of pecie vi Rmn pectrocopy with the poibility of quntifiction of e.g. iron (hydro-) oxide fter the pecific corroion experiment or long-term expoure to ir [6, 17, 19]. In thi work, high grde electricl teel, teel contining up to 5% lloying element, minly ilicon, luminium nd mngnee, i ued. Electricl teel i

2 phyic p ttu olidi 1430 C. Hmbrock et l.: Surfce chrcterition of nneled electricl teel urfce necery for the efficient production of electric cr, wind power plnt or genertor nd the demnd for better qulity electricl teel i contntly riing. Thi i uully ccompnied by higher mount of lloying element but lo the production prmeter re of gret importnce. To uccefully produce non-grin oriented electricl teel t high temperture of bout 950 8C [20, 21], the oxidtion of the electricl teel under given tmophere nd dew point h to be tken into ccount. Thi oxidtion trongly influence the qulity nd the corroion of the teel, cn be een lo in other field of ppliction [22, 23]. Thi pper focue on the chrcterition of electricl teel urfce fter long-term high temperture nneling. Rmn imging i the method of choice ince the rection product nmely oxide of the lloying element re not found with other urfce nlyticl method; they rther determine the elementl compoition only. The novelty of thi pproch i the cle chrcterition on electricl teel by Rmn imging. In contrt to the homogeneou film formed on high lloyed teel uch tinle teel (Cr Ni) inhomogeneou thicker cle frgment re formed on electricl teel (Al Mn Si) for which phe identifiction i deirble. Such chrcterition h o fr not been ccomplihed nd will primrily help to undertnd nd chrcterie the phe exiting cloe to the thermodynmic equilibrium fter the nneling procedure. If thi i known, ubequent experimentl kinetic pproch cn be choen to evlute the rective pecie during high temperture nneling which will help to improve the production of electricl teel t given temperture. 2 Experimentl 2.1 Smple preprtion The electricl teel mteril ued for thi invetigtion w upplied by voetlpine Sthl GmbH. The mple were tken before the finl nneling tep (dimenion mm 2 ) with thickne of 0.5 mm to be ued for different lbortory nneling procedure. The compoition of the tndrd indutril high grde electricl teel i hown in Tble 1. Before the ubequent nneling tep in the lbortory furnce, the teel w cut into mple with the dimenion of mm 2, engrved nd clened in n lkline olution t 65 8C. The long-term nneling for 2 h t 950 8C h been performed in two chmber furnce correponding to two different tmophere with two different dew point meured by dew point mirror (Generl Etern, 1311DR). The mple were plced on mple holder nd nlyed fter nneling. The prmeter for the nneling including the heting nd cooling rte of the furnce cn be found in Tble Chrcterition method All chrcterition were performed on the urfce of the teel tht hd not been in contct with the mple holder. After nneling, the mple were kept in dry tmophere until the ctul meurement. No further mple preprtion or modifiction w ued before the nlyi vi Rmn imging or FEG- SEM-EDX (Field Emiion Gun Scnning Electron Microcope Energy Diperive X-ry detector). For the Rmn imging WITec Alph 300R confocl Rmn microcope with Nd:YAG ler (523 nm) t power of 30 mw w ued. A Nikon objective len (mgnifiction 20 ir, NA ¼ 0.8) provided pot ize of 1.6 mm. Thi etup enured lterl ptil reolution of 800 nm (x, y nd z xi). The ptil reolution in z-xi w bout 500 nm. The Ryleigh pek w uppreed by uing hologrphic edge filter. Applying diffrction grting with 600 groove per cm, pectrl reolution of pproximtely 3cm 1 w chieved for full pectrum rnging from 0 to 3750 cm 1. The rnge bove 2000 cm 1 will not be hown no pek could be oberved there. For Rmn imging, motoried XY piezo tge w ued to cn the mple. The entire pectrum of the confocl Rmn imge w collected with n integrtion time of 0.1 every 0.25 mm in n re of mm 2 (equivlent to 14,400 individul pectr, one pectrum for ech point meured). After dt cquiition, ll pectr were proceed by the WITec Project Softwre which llowed integrting individul pek to obtin n intenity mpping of ech pek correlted to the poition nlyed on the mple re. The brighter the pot on the mple re the higher i the integrted re of the individul pek which i directly correlted to the concentrtion of thi compound. Tble 1 Compoition of the tndrd high grde electricl teel. element Si Al Mn Cr P C Ti S wt% <0.02 <0.02 <0.005 <0.005 <0.005 Tble 2 Anneling prmeter for the two different chmber furnce (furnce 1 correponding to mple 1; furnce 2 correponding to mple 2). furnce tmophere temperture (8C) nneling time (h) heting-cooling rte (8C min 1 ) 1 10% H 2 in N % H 2 in N þ10 (etimted)

3 Originl Pper Phy. Sttu Solidi A 211, No. 6 (2014) 1431 The electron microcopic imge of the urfce h been tken with the econdry electron (SE) detector on FEG- SEM Supr 35 from ZEISS t n electron bem energy of 5 kev, the cro-ectionl imge h been tken with the bckcttered electron (BSE) detector on the me intrument. The elementl compoition h been monitored with n EDX mpping on the me urfce re uing n EDAX ytem with Si(Li)-detector 10 mm 2 uing n electron bem energy of 15 kev. A imilr mgnifiction of bout mm 2 h been choen for the EDX mpping for better comprion of the two mpping. The XPS meurement complementry method h been performed with Thet Probe (Thermofiher, UK) operted with the Avntge oftwre to confirm the compoition obtined vi Rmn nd EDX mpping. The X-ry ource w monochromted Al K line ( ev) with pot ize of >300 mm nd power of 75 W. For chrge neutrlition flood gun FG02 w ued. The urvey cn were performed t p energy of 200 ev with tep ize of 1 ev in binding energy nd dwell time of 50 m. The quntifiction w ccomplihed by uing Scofield enitivity fctor [24]. 3 Reult nd dicuion Two different lbortory nneling condition hve been choen to evlute on the one hnd the urfce compoition nd on the other hnd the dvntge nd poibilitie of Rmn pectrocopy. The mteril for both condition et of nneling were the me but the nneling prmeter differed widely in term of dew point, mple 1 w nneled t very low dew point of 50 8C where mple 2 w nneled t dew point of bout þ10 8C. The other prmeter like temperture (950 8C), nneling time (2 h) nd tmophere (10% H 2 in N 2 ) were kept the me for both mple. 3.1 Smple 1 (nneling t 950 8C for 2 h t dew point of 50 8C) The urfce propertie of mple 1 were chrcteried by uing Rmn imging. The imge nd pectr re hown in Fig. 1 reveling different pek with vrying intenity over the nlyed re. The higher the concentrtion of one pek (correlted to one pecific compound) the brighter i the intenity of the pot in the Rmn imge. Figure 1 how the Rmn imge of the pek t 618 cm 1 nd the correlted Rmn pectrum cn be found in Fig. 1b. Thi pek nd lo pek of the Rmn pectrum hown in Fig. 1d (correponding to the Rmn imge in Fig. 1c) cn be correlted to different crytlline tructure of luminium nitride [25]. Thi compound w not found in the minerl dt be [26] but becue of the elementl compoition obtined vi EDX mpping (ee Fig. 4) the compoition w confirmed nd pecific literture concerning Rmn pectrocopy of luminium nitride could be erched for reveling three chrcteritic pek [25, 27]. Furthermore the publiction were deling with the Rmn hift becue of difference in orienttion of the AlN crytl or in the thickne of the AlN lyer which did not occur here. Figure 1e diply the Rmn mpping of the bnd t 219 cm 1, where Fig. 1f how the correponding Rmn pectrum of the bright re. Correlting the pectrum to reference pectr, the bnd t 219 cm 1 nd lo the bnd t 286 nd 1305 cm 1 could be relted to hemtite [28]. The mll pek t round 380 cm 1 (ee Fig. 1f) w not lbelled but it could be correlted to n iron hydroxide (FeOOH) [28]. Thoe iron (hydro-)oxide probbly evolved from corroion of the urfce t mbient temperture the tmophere w protective for iron during the nneling tep. The tmophere w lo protective for other lloying element in the electricl teel, like ilicon nd mngnee, becue of the low oxygen prtil preure t dew point of 50 8C (correponding to preure of P). Only the formtion of luminium nitride (nd ome oxide, ee Fig. 11) w fvoured. The SEM imge of the urfce re tht h lredy been nlyed vi Rmn imging i diplyed in Fig. 2. The urfce tructure ppered rther homogeneou; only t ome pot difference in the urfce tructure w viible which grew during nneling (ee Fig. 2 in the upper middle of the imge). The very low dew point of bout 50 8C nd the protective tmophere of 10% H 2 in N 2 eem to influence the urfce tructure directly. The dotted tructure viible on the urfce of the mple correpond well to the Rmn imge in Fig. 1 nd c. Looking t the nneled electricl teel in croectionl view (ee Fig. 3) reveled homogeneou thickne ditribution of the urfce lyer. The oxidtion depth w le thn 1 mm nd only compoed of luminium with nitrogen nd ome oxygen (ee Fig. 11). When looking t the EDX mpping of the homogeneou mple urfce, the elementl nlyi reveled high concentrtion of luminium nd nitrogen (ee Fig. 4 nd b). Thi doe not only correpond very well to the informtion obtined vi Rmn imging but lo the pttern with mll dot, viible in Fig. 4, i the me. Thi pttern cn lo be detected when looking t the element iron (Fig. 5) nd when compring luminium with iron it cn be een tht the iron content get lower with higher luminium content, nd vice ver. Thi cn be explined when looking t the penetrtion depth of both method the Rmn imging i urfce enitive method which penetrte ome nm, where the EDX mpping h lightly higher penetrtion depth of bout 1.5 mm t the energy ued. The deeper the poibility of penetrtion into the urfce, the more iron from the ubtrte cn be detected. Due to the rther thin lyer of <1 mm (reveled by cro-ectionl nlyi, ee Fig. 3) the content of iron detected by EDX mpping i high. Since Rmn imging h n even mller penetrtion depth, the chrcterition of the urfce lyer with it Rmn-ctive ignl w ucceful. On top of thi homogeneou lyer of AlN n pprently different egment i viible, probbly grown during nneling. When looking t the EDX mpping performed on the urfce, the elementl compoition could be identified

4 phyic p ttu olidi 1432 C. Hmbrock et l.: Surfce chrcterition of nneled electricl teel urfce Figure 1 () nd (b) Rmn imge nd Rmn pectrum of the pek integrl of the pek t 618 cm 1, (c) nd (d) Rmn imge nd Rmn pectrum of the pek integrl of the pek t 666 cm 1 nd the ocited pek t 919 cm 1. (e) nd (f) Rmn imge nd Rmn pectrum of the pek integrl of the pek t 219 cm 1 nd the ocited pek t 286 nd 1305 cm 1. being lmot pure iron with ome ilicon content (ee Fig. 5 for iron, EDX mpping of ilicon i not hown here). Thi prt of the mple ppered drk in the Rmn mpping (Fig. 1 nd c) becue pure iron h no ctive bnd in Rmn pectrocopy. Thi my be didvntge when looking t teel mple but here the focu w lid on the identifiction of phe grown during nneling. Additionlly the meurement w ey to be performed (no mple preprtion necery) nd with the help of complementry method (e.g. EDX mpping) thi deficit of the method w compented. The Rmn imge in Fig. 1e reveled ome bright pot which cn be directly correlted to high mount of oxygen in the mple cn be een when looking t Fig. 5b. A the pek in the Rmn pectrum were correlted to ome iron oxide, thi could be confirmed with the EDX mpping well.

5 Originl Pper Phy. Sttu Solidi A 211, No. 6 (2014) 1433 Figure 3 SEM imge of the cro-ection of the electricl teel nneled for 2 h t 950 8C with dp of 50 8C in n tmophere of 10% H 2 in N 2 (15 kev, BSE detector, cle 2 mm). Figure 2 SEM imge of the urfce of the electricl teel nneled for 2 h t 950 8C with dp of 50 8C in n tmophere of 10% H 2 in N 2 (15 kev, SE detector, cle 10 mm). 3.2 Smple 2 (nneling t 950 8C for 2 h t dew point of bout þ10 8C) The econd mple chrcteried by Rmn imging w prepred t different dew point (bout þ10 8C inted of 50 8C) in the me nneling tmophere (10% H 2 in N 2, 950 8C). In thi tmophere, higher mount of oxygen (correponding to prtil preure of P) w vilble which reulted in different phe on the urfce. In generl, more complex oxide nd no nitride compound could be found. The reult of the Rmn mpping nd the correponding Rmn pectr re hown in Fig. 6. In the re from 0 to Figure 4 EDX mpping of luminium Al () nd tomic nitrogen N (b) tken t n electron bem energy of 15 kev with econdry electron detector. Figure 5 EDX mpping of iron Fe () nd tomic oxygen O (b) tken t n electron bem energy of 15 kev with econdry electron detector.

6 phyic p ttu olidi 1434 C. Hmbrock et l.: Surfce chrcterition of nneled electricl teel urfce Figure 6 () nd (b) Rmn imge nd Rmn pectr of the pek integrl of the pek t 826 cm 1 nd the ocited pek t 926 nd 845 cm 1 ; (c) nd (d) Rmn imge nd Rmn pectr of the pek integrl of the pek t 710 cm 1 nd the ocited pek t 578 nd 1305 cm cm 1 n extenive bckground correction mde it impoible to evlute the pek in tht prt of the pectrum. The pek bove thi Rmn hift were correlted to different compound. Figure 6 nd b how the Rmn imge of the min pek t 826 cm 1 nd the Rmn pectrum of thi region. The mximum of the bnd t 826 cm 1 nd it ymmetricl hpe with houlder t 845 cm 1 well correponding pek t 926 cm 1 refer to ilicte tructure. The elementl compoition of the ilicte w detected vi EDX mpping where no mgneium nd only rther low content of mngnee (contined in forterite nd kirchteinite, repectively) could be found. The pek were therefore identified the minerl fylite [29] which i lo in ccordnce with the literture bout high temperture oxidtion t high oxygen content [30]. The Rmn imge diplyed in Fig. 6c nd it correponding Rmn pectrum (Fig. 6d) how three different pek t 578, 710 nd 1305 cm 1. The pek could not ll be correlted to one pecie but the pek t 578 nd 1305 cm 1 indicted mll mount of hemtite. Although the dew point for the nneling of thi mple w higher thn for the firt mple, the nneling tmophere w till protective for iron. Therefore n tmopheric corroion fter the nneling i uppoed to hve oxidied the iron lightly. Correlting the reference pectr (dtbe for minerl ee Ref. [26]) to the pek t 710 cm 1, no mtching pek could be found. In literture the devition of the Rmn hift depending on the compoition i decribed when tlking bout fylite nd forterite [18, 29]. Such mixture of compound cn be found here well, compoed of Fe 2 SiO 4 pinel (pek t bout 672 cm 1, [31, 32]), nd ilicon dioxide, correponding to the minerl tihovite/ tridymite (pek in the rnge of cm 1, [33]). The correponding confirmtion pek of ilicon dioxide i not hown here it i locted t 2924 cm 1. The compoition i uppoed to be bout 50:50 the pek with Rmn hift of 710 cm 1 i ituted in between. However, due to difference in lyer thickne or crytl orienttion, the expected Rmn hift my hve ome devition. Thoe devition cnnot be detected by chooing different reference pectr but it i helpful to look for correponding literture or to

7 Originl Pper Phy. Sttu Solidi A 211, No. 6 (2014) 1435 Figure 7 EDX mpping of iron Fe () nd oxygen O (b) tken t n electron bem energy of 15 kev with econdry electron detector. Figure 8 EDX mpping of luminium Al () nd ilicon Si (b) tken t n electron bem energy of 15 kev with econdry electron detector. implement pectrl librry on crefully prepred reference mteril with exct compoition. The formtion of fylite, ilicon dioxide nd pinel (mde of iron or ome mngnee) w reported by Preznovic nd Spiegel who decribed the hort-term oxidtion of Fe Si nd Fe Mn model lloy in ir [30]. Aluminium n element in pinel i reported to uully occur t higher temperture of bove C [34]. Depite thi fct, ome luminium could be found in the urfce tructure when compring the elementl compoition of the EDX mpping (Fig. 7 nd 8). The bright pot viible in the Rmn imge in Fig. 6c could not be evluted in term of compoition becue the intenity w due to topogrphic influence which w reveled when looking t the mple by SEM (ee Fig. 9). It w not poible to detect thi contmintion with the confocl microcope ttched to the Rmn imging Figure 9 SEM imge of the urfce of the electricl teel nneled for 2 h t 950 8C with dp of þ10 8C in n tmophere of 10% H 2 in N 2 (15 kev, SE detector, cle 10 mm).

8 phyic p ttu olidi 1436 C. Hmbrock et l.: Surfce chrcterition of nneled electricl teel urfce Figure 10 SEM imge of the cro-ection of the electricl teel nneled for 2 h t 950 8C with dp of þ10 8C in n tmophere of 10% H 2 in N 2 (15 kev, BSE detector, cle 2 mm). intrument before the performnce of the meurement. However, the effect of topogrphy on the intenity of the Rmn imging ignl mut lwy be conidered. Looking t the SEM imge of the mple in Fig. 9, differently tructured urfce cn be detected when compring it to the imge in Fig. 2. On the left nd lower prt of the imge contmintion on top of the urfce i viible. Thi contmintion led to topogrphic effect in the Rmn imging well in the EDX mpping. Therefore it w not poible to evlute thi pot in term of compoition in neither of the method ued here. Not only the urfce tructure but lo the compoition nd the cle thickne re influenced by the dew point nd the nneling tmophere. A higher dew point incree the rectivity of the lloying element in the bulk mteril. The SEM imge of the cro-ection (ee Fig. 10) reveled urfce lyer thickne of up to 10 mm, compoed of vrition of (complex) oxide. The reult of the EDX mpping of elected element cn be een in Fig. 7 nd 8. Figure 7 how the compoitionl nlyi of iron () nd oxygen (b) nd the pttern cn be directly correlted to the urfce oberved vi SEM nd Rmn imging. Figure 8 how the two element luminium () nd ilicon (b). The locl ditribution of the lt lloying element mngnee i not hown here, becue the concentrtion t the urfce w too low to be relevnt. However, the EDX mpping reveled the me pttern lredy oberved for the other element. Cro-correlting the concentrtion of the element to ech other how tht high content of minly oxygen nd ilicon (ome luminium nd mngnee) i ccompnied by low content of iron. In thi wy correltion of the compoition nd the pprent urfce tructure become poible. Thi correpond well to the umption tht prt of the urfce tructure re compoed of ilicon dioxide, iron ilicte nd iron pinel. 3.3 Integrl XPS meurement An XPS meurement h been performed on both mple to get nother prove of the compoition obtined vi Rmn imging nd EDX mpping well informtion on the binding tte of the individul element. When compring the pectr of the two mple (ee Fig. 11), the XPS nlyi how lrge difference in compoition well. The pectrum of mple 1 (Fig. 11) how very high nitrogen nd luminium content nd only mll mount of oxygen. Figure 11b revel the pectrum of the econd mple, nneled t higher dew point. Here, mny different element, very high content of oxygen nd hrdly ny nitrogen could be detected. To obtin informtion bout the binding tte of the urfce tom, the Crbon 1 reference method w ued. The C1 pek of both mple w corrected to binding energy (BE) of 285 ev nd the binding energie of the individul pek of ech mple were corrected by the me fctor well. Both pectr, epecilly the econd mple, reveled poor ignl to noie rtio. Thi i why the ccurcy of the obtined binding energie my leve ome pce for doubt. Alo the uncertinty of the meurement of 0.2 ev h to be tken into ccount when compring the vlue. In mple 1, four min pek, depite the crbon, were found. One w the luminium Al2p pek t BE of ev. Thi could be correlted to luminium nitride Figure 11 Integrl XPS meurement on () mple 1 nd (b) mple 2.

9 Originl Pper Phy. Sttu Solidi A 211, No. 6 (2014) 1437 (AlN, BE ev) nd lo the pek of nitrogen N1 t ev could be correlted to the vlue reported in literture for luminium nitride (BE ev) [35]. Due to the preence of oxygen trce t the urfce it i likely tht ome concurrent luminium oxide formtion hd tken plce. However, the ignl to noie rtio w not high enough to be ble to ditinguih the two ubtnce the binding energie re quite imilr. The mll iron Fe 2p 3/2 pek t bout ev could be correlted to mixture of hemtite nd ome mgnetite [36]. The oxygen O1 pek in the pectrum w not evluted becue it w uppoed to be mixture of the different oxide. The econd mple reveled more pek thn the firt mple becue lo ilicon Si2 nd ome mngnee Mn 2p 3/2 pek could be found. The Si2 pek t BE of ev correpond well to n olivine tructure like fylite being in concordnce lo with the O1 pek t the BE of ev [37]. Further the pek of iron Fe 2p 3/2 t BE of ev could be correlted to mixture of the binding energy of fylite nd ome iron oxide [36]. The Al 2p pek t ev could be correlted to luminium oxide [35]. The mount of mngnee nd nitrogen were too low for correltion of the binding energie. The BE-correltion of both mple re in good greement with the reult obtined vi Rmn imging. In both ce crbon could be detected on the urfce which i common nd well known effect in urfce nlytic. In the preent tudy thi vlue remin high ince no urfce clening by, e.g. Ar puttering w performed with repect to the interet in the very urfce which would hve been ffected by the puttering proce. 4 Concluion Rmn imging h been proven to be n efficient method for the identifiction of urfce tructure nd compoition on long-term high temperture nneled mple. With the vrition of the dew point of the nneling tmophere, different urfce compoition could be reveled which correponded well to literture [21 22, 30]. At high dew point (correponding to n oxygen prtil preure of bout P), ilicon nd luminium rected with oxygen in the tmophere to form oxide (Al 2 O 3, SiO 2 ), ilicte (Fe 2 SiO 4 ) nd pinel phe (Fe 2 SiO 4 -pinel). Epecilly the different ilicon phe could be eily identified nd ditinguihed vi Rmn imging. At low dew point (correponding to n oxygen prtil preure of bout P) the tmopheric condition were protective for iron nd for ilicon nd only the luminium rected with the oxygen well with the nitrogen of the nneling tmophere. Therefore not only oxide or ilicte phe but lo nitride compound uch luminium nitride (AlN) could be identified vi Rmn imging. With the help of the elementl compoition (obtined by EDX mpping) nd the bonding tte (obtined by XPS) the compoition obtined by Rmn imging could be verified nd even phe tht re not Rmn ctive, like e.g. pure iron, could be identified with the help of thoe complementry method. 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