Effect of Si Content and Temperature on Oxidation Resistance of Fe-Si Alloys

Effect of Si Content and Temperature on Oxidation Resistance of Fe-Si Alloys

􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇 JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL􀆰2 0 1 5,2 2( 3):2 3 8 G 2 4 4 􀪉􀪉􀪉􀪉􀪉...

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􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇􀪇

JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL􀆰2 0 1 5,2 2( 3):2 3 8 G 2 4 4

􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉􀪉 􀪉

Ef f e c to fS iCon t e n tandTempe r a t u r eonOx i da t i on Re s i s t anc eo fFe G S iAl l o s y 2 Xi ao G i angLIU1 ,  Yong G Gmi ngCAO2 ,  TaoJ IA2 , j quan HE ,  Guang 2 2 Teng G zh iWU ,  Zhen G yuLIU

( 1. Schoo lo fMe chan i c a lEng i ne e r i ng,ShenyangUn i ve r s i t fTe chno l ogy,Shenyang110870,L i aon i ng,Ch i na; yo , , , , 2. S t a t eKeyLabo r a t o r fR o l l i n n dA u t o m a t i o n N o r t h e a s t e r nU n i v e r s i t S h e n a n 1 0 8 1 9 L i a o n i n C h n a) yo ga y y g1 g i Ab s t r a c t:Ho t G r o l l e dFe G( 0 􀆰75-2 􀆰20) S i( ma s s% )a l l oy swe r eox i d i z e di nd r i ra t600-1200℃. Theox i da t i onp r o c e s s ya wa sc a r r i edou tbyt he rma lg r av ime t r i cana l s i s( TGA).At600-1150 ℃ ,ox i da t i onga i ncu r ve swe r eapp r ox ima t e l y y r abo l i c.El e c t r onp r obemi c r oana l s i s( EPMA)wa sapp l i edt oi nve s t i t ec r o s s G s e c t i on mo r l ogyo fox i del aye r pa y ga pho ande l emen td i s t r i bu t i ona c r o s st hel aye r.Atl owe rt empe r a t u r eo f700 ℃ ,t heox i del aye rc ons i s t edo fi n t e r na lox i da G t i onz one ( IOZ),i nne rS i G r i chl aye r( c ong l ome r a t eo ff aya l i t eand magne t i t e)andou t e rhema t i t el aye r,wh i l ea t h i rt empe r a t u r eo f1200 ℃ ,f aya l i t eandwus t i t ewe r eobs e r vedi nex t e r na lox i des c a l e.L i i dust empe r a t u r eo f ghe qu f aya l i t ewa sde t e c t edbyd i f f e r en t i a ls c ann i ngc a l o r ime t r DSC).Thr oughc ompa r i ngt heox i da t i on ma s sga i nand y( r abo l i cr a t ec ons t an to ft hea l l oy s,i twa sf oundt ha tox i da t i onr e s i s t anc eo fFe GS ia l l oywa senhanc edbyi nc r e a s i ng pa S ic on t en tbe l ow1150 ℃ wh i l ei nc r e a s i ngS ic on t en to ft hea l l oyr e su l t edi nh i rox i da t i onr a t eabove1150 ℃ owG ghe i ngt ot hel i i df aya l i t ef o rma t i on. qu Ke r d s:Fe GS ia l l oy;f aya l i t e;l i i dust empe r a t u r e;ox i da t i onr e s i s t anc e;S ic on t en t qu ywo

  S iwa sa dd e di n t oa l l o oimp r o v ei t se l e c t r oma G yt g [ [ ,] 1] n e t i cp r op e r t t r e ng t h2 3 a nd ox i d a t i on r e s i s t G y ,s [ ,] an c e4 5 ,a ndi ta l s oh e l e dt or e du c et h ec on t e n to fo t h G p [ 6] , , e re xp e n s i v ea l l o i nge l eme n t ss u c ha sCr Al e t c 􀆰 . y Ox i da t i onr e s i s t anc eo f Fe GS ia l l oy wa sr e l a t edt o s c a l e mo r h o l o a n do x i d a t i o nt e m e r a t u r e . S c a l e p gy p , mo r l ogydependedona tmo sphe r e t empe r a t ur e pho andS ic on t en t.Ox i da t i on behav i o ro fFe G( 0 􀆰01- 1 􀆰91) S i(ma s s% )a l l o swa ss t ud i e da t700-1000 ℃ y [] unde rd r i rc ond i t i onby Yange ta l 􀆰 7 .Theyap G ya r ovedt ha t ox i da t i on ma s s ga i n cu r ve sc omp l i ed p wi t hpa r abo l i cl awandox i da t i onr e s i s t anc ewa simG r ovedf o rt hea l l oyswi t hh i rS ic on t en t. Fo rt he p ghe a l l oywi t hl owe rS ic on t en t( be l ow0 􀆰51% ),i t sex G t e rna lox i des c a l ewa sma i n l ompo s edo fwus t i t e, yc magne t i t eand hema t i t e,wh i l ef o rt hea l l oy wi t h h i rS ic on t en t( above1 􀆰14% ),t heox i del aye r ghe ( ) , cons i s t edo fi n t e rna lox i da t i onz one IOZ i nne rS i G r i chl aye randou t e rhema t i t el aye r.Thes amea l l oy wa sox i d i z eda t850-1200 ℃ i nd r i rby Yange t ya

[] a l 􀆰 8 .Theyf oundt ha t,a t1200 ℃ ,eveni fS icon G , t en twa sabove1 􀆰14% t heex t e rna lox i des c a l ewa s s t i l lcompos edo f wus t i t e,magne t i t eandhema t i t e be c aus eo ft hef o rma t i ono fl i i df aya l i t e,andi t s qu l i i dust empe r a t ur e wa s abou t 1173 ℃.L i ue t qu [] a l 􀆰9 s t ud i edt hee f f e c to ft empe r a t ur eont hes c a l e s t ruc t ur eo fFe G 1 􀆰5S i( ma s s% )a l l oyandf oundt ha t s c a l es t ruc t ur ewa sa lmos tt hes ameexc ep ta t1000 and1200 ℃.At1000 ℃ ,t he r ewe r ef ewox i dep r e G c i i t a t e sa tsubsur f a c eo ft hea l l oyanda t1200 ℃ , p f aya l i t eno ton l o rmedal aye rbu ta l sopene t r a t ed yf [ ] i n t ot heou t e rox i des c a l ede ep l r e ze ta l 􀆰 10 y.Suá s t ud i ed t he ox i da t i on behav i o ro f Fe G(0 􀆰078 - 3 􀆰060) S i( ma s s% )a l l oysi na i r.Theyf oundt ha t,a t , 1150 ℃ f o rt hea l l oyswi t hS icon t en to f1 􀆰88and 3 􀆰06ma s s% ,t heox i del aye rwa scompos edo fou t e r magne t i t eand wu s t i t el a e randi nn e rf a a l i t el a e r, y y y wh i l ea t1200℃ ,t hes t ruc t ur eo fou t e rl aye rconve r G t edt ocong l ome r a t eo fmagne t i t e,wus t i t e,hema t i t e

andf aya l i t e.Re s e a r chonox i da t i onbehav i o ro fFe GS i

Founda t i onI t em: I t em Spons o r edbyNa t i ona lHi G t e chRe s e a r chandDeve l opmen tPr og r amo fCh i na ( 2011BAE13B04);Na t i ona lNa t ur a l gh Sc i enc eFounda t i ono fCh i na ( 51204047,51204053) B i o r aphy: Xi ao G i angLIU,Do c t o rCand i da t e,Le c t ur e sh i Gma i l: ox i de s c a l e@163 􀆰c om; Re c e i v e dDa t e:Novembe r19,2013 j p; E g

I s sue3       Ef f e c to fS iCon t en tandTempe r a t u r eonOx i da t i onRe s i s t anc eo fFe GS iAl l oy s 

a l l oywa she l f u lonsu r f a c equa l i t on t r o lo fs i l i con p yc [ ] s t e e l.Fukagawae ta l 􀆰 11 f oundt he me chan i sm o f r eds c a l ede f e c tf o rma t i oni nS i G addeds t e e lbyana l G y [ ] z i ngt heox i da t i onp r o c e s s. L i ue ta l 􀆰 12 ob t a i nedt he me chan i sm o fb l a cks t r i r a t edonsu r f a c eo f psgene ho t G r o l l eds i l i c ons t e e lba s edonox i da t i onbehav i o r r e s e a r chonFe G 2 􀆰2S i( ma s s% )a l l oy.    I nt he p r e s en ts t udy,ho t G r o l l ed Fe G( 0 􀆰75- 2 􀆰20) S i(ma s s% )a l l oyswe r eox i d i z edi nd r i ra t ya 600-1200 ℃ andt hel i i dust empe r a t u r eo ff ay G qu a l i t ewa sde t e c t ed,wh i ch wa sl owe rt hant heva l ue t e s t edbe f o r e.Usua l l aya l i t ewou l dh i nde rd i f f u G y,f ; s i ono fi r oni ons howeve r,i t wou l dp r omo t et he d i f f us i on wheni t wa si nl i i ds t a t e.Thus,t he qu e f f e c to fS ic on t en tonox i da t i onr e s i s t anc eo ft hea l G l oyswa sd i f f e r en taboveo rbe l owt h i st empe r a t ur e.

239

Al so,t he p r ope r wo rk i ngt empe r a t ur e wa sa s c e r G t a i nedf o ra l l oysby me anso fi nc r e a s i ngS icon t en tt o imp r ovei t sox i da t i onr e s i s t anc e.

1 Exp e r imen t a lPr o c e du r e

  Thet e s tp l a t e swe r esupp l i edf r om WuhanI r on andS t e e lCo r r a t i onandt he i rchemi c a lcompos i G po t i onsa r eshowni nTab l e1.Thespe c imenswi t hd i G mens i onso f12 mm×10 mm we r e ma ch i nedou to f t he s ep l a t e sandaho l eo f2 mm i nd i ame t e r wa s d r i l l edne a roneendo fe a chspe c imenf o rsuspend i ng i nt hef urna c echambe ro ft het he rma lg r av ime t r i c ana l z e r.Al lsur f a c e so ft hespe c imenwe r epo l i shed y on a s e r i e so f abr a s i ve pape r s up t o 1200 g r i t,

wa shedwi t ha c e t onei nanu l t r a son i cba t handd r i ed.   The rma lg r a v ime t r i can a l s i s( TGA)expe r imen t s y

     Tab l e1 Ch emi c a lc ompo s i t i ono fe xp e r imen t a la l l o s       ma s s% y Al l oy

C

S i

Mn

P

S

Als

Fe

Fe G 0 􀆰75S i

0 􀆰005

0 􀆰750

0 􀆰250

<0 􀆰030

<0 􀆰005

0 􀆰005

Ba l anc e

Fe G 2 􀆰20S i

0 􀆰005

2 􀆰200

0 􀆰400

<0 􀆰030

<0 􀆰005

0 􀆰400

Ba l anc e

Fe G 1 􀆰50S i

0 􀆰005

1 􀆰500

0 􀆰800

we r ec a r r i edou t,andspe c imenswe r esuspendedi n t hef u rna c echambe r.Af t e reva cua t i on,i twa sf i l l ed wi t ha r t i lt hep r e s su r eo ff u rna c echambe rr e G gonun t urnedt o10-2 Pa. I ne a chexpe r imen t,as amp l ewa s he a t edi na r tmo sphe r ea tar a t eo f50 ℃/mi n gona un t i li tr e a chedt hep r e G de t e rmi nedt empe r a t u r er an G i ng f r om 600 t o 1200 ℃.As t he t empe r a t ur e g r e a chedt hepr e G s e tva l ue,d r i rwi t haf l owr a t eo f ya / 50mL mi nwa si n t r oduc edi n t ot heTGAchambe rt o conduc tt he480 mi n ox i da t i on expe r imen t s.Af t e r t hei s o t he rma lpe r i od,TGAchambe rwa sc oo l edt o r oomt empe r a t u r ea tar a t eo f99 ℃/mi ni na r t G gona mosphe r eimmed i a t e l y.   Th eme t a l l og r a i cp r e a r a t i on,s u c ha smoun t i ng, ph p , , r i nd i ng andpo l i sh i ng wa spe r f o rmedi nt heusua l g [ ] s equenc e13 .Thee t chedspe c imens we r eexami ned bye l e c t r onpr obemi c r oana l i s( EPMA),andgen G ys e r a l l heba ck G s c a t t e r ede l e c t r onimage ( BEI)mode yt wa sus ed.Compo s i t i ono fox i d es c a l ef o rme da t700 ℃ wa sde t e c t edbyus i nganXG r ayd i f f r a c t ome t e r.Mi x G t ur eo ff aya l i t eandFeox i de swa sob t a i nedf r omex G t e rna lox i des c a l eo fFe G 2 􀆰2S ia l l oya t1200 ℃ and l i i dust empe r a t u r eo ff aya l i t e wa sa s c e r t a i nedby qu d i f f e r en t i a ls c ann i ng c a l o r ime t r t s y (DSC).And i compo s i t i on wa sana l z ed wi t h wave l eng t hd i spe r G y s i vespe c t r o s c opy (WDS).

<0 􀆰030

<0 􀆰005

0 􀆰250

Ba l anc e

2 Re s u l t s   F i 􀆰1dep i c t st hema s sga i ncur ve so ft hespe c i G g mensa tva r i oust empe r a t ur e s.Atl owt empe r a t ur e s, t ak i ng700and900 ℃ f o rexamp l e,t he ma s sga i n cur ve sp r e s en tpa r abo l ashape.Ox i da t i onr e s i s t anc e i simp r ovedbyi nc r e a s i ngS icon t en t( F i 􀆰1( a)and gs 1( b)).At1150 ℃ ,ma s sga i ncur ve sa r es t i l lpa r a G , bo l i c bu tox i da t i onr e s i s t anc ewa sno tenhanc edby i nc r e a s i ngS icon t en t.Thef i na lox i da t i onma s sga i ns ( ) ) a r ea lmos tt hes ame ( F i 􀆰 1 c .O x i d a t i o n m a s s g i no fFe G 2 􀆰2S ia l l oyi sl a r rt hant hos eo ft heo t hG ga ge e ra l l oysa tmos tpe r i odo ft heox i da t i onp r oc e s s.At 1200 ℃ ,be c aus eo ft hef a s tox i da t i onr a t eo ft hea l G , l oys t heme a sur i ngr angeo fTGAi se a s i l obeex G yt c e eded.Thus,ox i da t i onpe r i oda tt h i st empe r a t ur ei s sho r t enedt o30 mi n.Ox i da t i oncur ve so ft hespe c i G mensa r el i ne a r. I nconc l us i on,t hee f f e c to fS icon G t en tonox i da t i onr e s i s t anc eo fFe GS ia l l oya s soc i a t e s wi t h ox i da t i ont empe r a t ur e,and a tl ow t empe r a G t ur e s,i ti simp r ovedbyi nc r e a s i ngS icon t en t.   I no rde rt oexp l a i nt hee f f e c to ft empe r a t ur eand , S icon t en tonox i da t i onma s sga i nmo r ec l e a r l e l a G yr t i onsh i twe en ma s sga i nandox i da t i ont empe r a G pbe t ur eo ft hea l l oysi scompa r edi nF i 􀆰2. I ngene r a l, g ox i da t i onma s sga i ni si nc r e a s edbyr a i s i ngox i da t i on

240

    J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l              Vo l 􀆰22 

( a)700 ℃ ;   ( b)900 ℃ ;   ( c)1150 ℃ ;   ( d)1200 ℃.

F i 􀆰1 Ma s sg a i nc u r v e so ft h es e c imen sa tv a r i ou st emp e r a t u r e s g p

F i 􀆰2 Ef f e c to fS ic on t en tonox i da t i onma s s g a i na tv a r i ou st emp e r a t u r e s g

t emp e r a t u r e.Re l a t i on s h i e twe e nox i da t i onr a t eand pb t empe r a t u r ec ou l dbeexp r e s s edby Ar rhen i usequa G [ ] t i on14 æ Q ö÷ ç ( ÷     kp=k°pexpçç - 1) RT ÷ø è whe r e,kpi spa r abo l i cr a t ec ons t an t;k°pi sc ons t an t; ; Qi sox i da t i ona c t i va t i onene r R i s a sc o n s t a n t gy g ( ) andTi sox i da t i ont empe r a t u r e. Re f e r r edt oEq 􀆰1 , kpi nc r e a s e sa lmo s texponen t i a l l t hT ,andt hus, ywi

cur ve si nF i 􀆰2 pr e s en texponen t i a l.I tc anbeob G g , , s e r vedt ha t be l ow1150 ℃ ox i da t i onr e s i s t anc eo f t hea l l oysi simp r ovedbyi nc r e a s i ngS icon t en t.Es G c i a l l t1000-1150 ℃ ,ox i da t i onr e s i s t anc eo f pe ya , Fe G 2 􀆰2S ia l l oyi sh i h e r . A t1 1 5 0 ℃ m a s s a i n so f g g t he a l l oys a r es imi l a r, wh i ch demons t r a t et ha t add i ngS ii n t ot hea l l oyi si nva l i dt oimp r oveox i da G t i onr e s i s t anc eo fFe GS ia l l oys. ,   I nf a c ta sshowni nF i 􀆰1( a)t o1( c),t hei n i G gs t i a ls t ageo ft heox i da t i on ma s sga i ncur vei sl i ne a r anda f t e rt ha t,mos tpa r t so ft hecur vea r epa r abo l i c. Ati n i t i a ls t age,d r i rs t a r t st obei n t r oduc edi n t o ya t hechambe ro fTGA wh i chmake st hea l l oyox i d i z ed i nd i l u t eoxygena tmosphe r e. Be c aus eo ft hef a s tox i G , da t i onr e a c t i onr a t ea tt hea l l oysur f a c e ox i da t i on r a t ei scon t r o l l edbyd i f f us i ono foxygenf r oma tmos G r ei nt hed i s t anc e wh i ch wou l dr e su l ti nl i ne a r phe , , ma s sga i ncur ve.Me anwh i l ea ti n i t i a ls t age a l t e r a G t i ono ff l ow r a t ea l sod i s t urbst he mi c r oba l anc eo f TGA s eve r e l o rs imp l i c i t hesho r ti n i t i a l y.Sof y,t s t age ( 0-60 mi n)wa sneg l e c t edandt hepa r abo l i c s t agewa scons i de r edon l e l a t i onsh i twe en y.Ther pbe ox i da t i on ma s sga i npe run i ta r e aands r er oo to f qua

I s sue3       Ef f e c to fS iCon t en tandTempe r a t u r eonOx i da t i onRe s i s t anc eo fFe GS iAl l oy s 

ox i da t i ont imei si l l us t r a t edi nF i 􀆰3t o5,andi ti s gs f oundt ha tt her e l a t i onsh i sba s i c a l l i ne a r.Th i s pi yl [ ] r e su l ti si na c c o r danc ewi t h Wagne r ′ smode l15 æ m ö÷2 çΔ ( ÷÷ =2      çç kwt 2) èA ø sox i da t i onma s sga i n;A i ssu r f a c ea r e a whe r e,Δm i ; ; o ft hespe c imens ti sox i da t i ont ime andkwi sox i G da t i onma s sga i npa r abo l i cc ons t an t.Ther e su l t sa l so

241

r e f l e c tt ha td i f f us i ono fi ona c r os st heox i des c a l ei sa r a t e G con t r o l l i ngs t epdur i ngt heox i da t i onp r oc e s so f Fe GS ia l l oys. anb ec a l c u l a t e df r omt hes l op ei nF i s 􀆰3t o5.   kw c g Ther e su l t sa r el i s t edi nTab l e2. I ngene r a l,kwi n G c r e a s e swi t hi nc r e a s i ngt empe r a t ur e. Be l ow1150 ℃ , kw o fFe G 0 􀆰75S ia l l oyi sh i rt hant ha to fFe G 2 􀆰2S i ghe fFe G 0 􀆰75S i a l l oy.Espe c i a l l t1000-1100 ℃ ,kw o ya

F i 􀆰3 Re l a t i on s h i e twe enox i da t i onma s sg a i nands r er o o to fox i da t i ont imef o rFe G 0 􀆰75S ia l l o g pb qua y

F i 􀆰4 Re l a t i on s h i e twe enox i da t i onma s sg a i nands r er o o to fox i da t i ont imef o rFe G 1 􀆰5S ia l l o g pb qua y

F i 􀆰5 Re l a t i on s h i e twe enox i da t i onma s sg a i nands r er o o to fox i da t i ont imef o rFe G 2 􀆰2S ia l l o g pb qua y

    J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l              Vo l 􀆰22 

242

          Tab l e2 Ca l c u l a t e dkw o ft h ea l l o s             μm2/( cm4 􀅰 mi n) y Al l oy

[ 7]

Fe G 0 􀆰01S i

Fe G 0 􀆰75S i Fe G 1 􀆰5S i Fe G 2 􀆰2S i

600 ℃

4 􀆰90×10

-2

700 ℃ 1 􀆰30

800 ℃ 12 􀆰0

900 ℃ -

7 􀆰01×10-4 2 􀆰64×10-3 2 􀆰91×10-3 3 􀆰88×10-3

6 􀆰52×10-4 2 􀆰28×10-3 2 􀆰29×10-3 4 􀆰16×10-3

1000 ℃

1050 ℃

1100 ℃

1150 ℃

0 􀆰196

0 􀆰791

15 􀆰8

16 􀆰0

0 􀆰579

17 􀆰2



0 􀆰148



0 􀆰628

4 􀆰01×10-4 2 􀆰32×10-3 2 􀆰70×10-3 4 􀆰38×10-3 4 􀆰51×10-3 5 􀆰07×10-2

a l l oyi sano r de ro f magn i t udeg r e a t e rt hant ha to f Fe G 2 􀆰2S ia l l oy.At900 ℃ ,t hecu r veo fFe G 2 􀆰2S ia l G l oy ( F i 􀆰5)dev i a t e sf r om al i neobv i ous l e ad i ng g y,l t odev i a t i ono fc a l cu l a t edkw ,wh i chc aus e sad i f f e r G en tr e su l tf r om t hec onc l us i onabove.At1150 ℃ ,

kw o fFe G 2 􀆰2S ia l l oyi sg r e a t e rt hant ha to fFe G 0 􀆰75S i a l l oy.Thec a l cu l a t edr e su l ti sc ons i s t en twi t ht her e G su l ti nF i 􀆰2.Be s i de s,t hec a l cu l a t ed da t ai nt he g r e s en ts t udya r ec ompa r ed wi t hc a l cu l a t edone so f p [ ] Fe G 0 􀆰01S ia l l oyf r omo t he rs t udy16 . I ti sf oundt ha t ( ) kw o fFe G1 􀆰5-2 􀆰2 S ia l l oyi ssma l l e rt hant ha to f Fe G 0 􀆰01S ia l l oya t600-800 ℃.Thus,t hee f f e c to f S icon t en tonox i da t i onr e s i s t anc ea tl owt empe r a t ur e i sve r i f i edaga i n.

3 Di s c u s s i on

  Ox i des c a l ef o rmeda t700 ℃ wa sadop t edt oan G a l z es c a l e mo r l ogyo fFe GS ia l l oysa tl owt emG y pho r a t u r e s( F i 􀆰6).Fr om c ompa r i s on o ft hec r os s G pe g s e c t i ons c a l e mo r l ogy andl i nes c ann i ngr e su l t, pho s c a l es t ruc t u r e so ft hea l l oyswe r es imi l a r. S i G r i chr e G i on wa sobs e r veda tsubsu r f a c eo ft hea l l oy sub G g



14 􀆰2



29 􀆰8

s t r a t eandi nne rpa r to ft heox i del aye r.Be c aus et he con t en t so f Mn and Al we r el ow,t he i rva r i a t i on a c r os st hes c a l e wa sno tobv i ous.Ox i depa r t i c l ei n [ ] IOZ wa scons i de r edt obeS iO2 16 .S i G r i ch pha s ei n [ ] i nne rpa r to ft heox i des c a l ewa sf aya l i t e17G20 . Et ched wi t h2% hyd r och l o r i ca c i dso l u t i oni ne t hano l,hemG a t i t e and wus t i t e pha s e s we r ep r e f e r en t i a l l t G ya , t a cked wh i l et hemagne t i t ewa sl e f te s s en t i a l l G yun [ ] e t ched13 .Thus,hema t i t ewa st hema i ncomponen t o fou t e rl aye rand magne t i t eex i s t edi ni nne rpa r to f , t hes c a l e.Att heme an t ime p i e c e so fex t e rna lox i de s c a l espa l l edspon t aneous l i ngcoo l i ng we r eco l G ydur l e c t edf o rXG r ayd i f f r a c t i onana l i s,and ma i ncomG ys t we r ei den t i f i ed a s hema t i t e and magne t i t e ponen ( F i 􀆰7).Ther e su l tr e f l e c t edt ha tf aya l i t ewa sl i ab l e g t oadhe r et ot hea l l oysur f a c eandcou l dno tspa l le a s G , i l t hou t e rox i del aye r.Mo r eove r f o rma t i ono f y wi S iO2i nIOZandf aya l i t ei ni nne rpa r to fex t e rna lox G i des c a l ewou l dh i nde rt hed i f f us i ono fFei onwh i ch [ 19, 20] suppo r t edt he g r owt ho fex t e rna lox i des c a l e . Duet ot hei nsu f f i c i en tsupp l fFei on,h i l enc e yo ghva Feox i d ewa sl i ab l et of o rm,s u c ha sma e t i t eandhemG gn

( a)Fe G 0 􀆰75S ia l l oy;   ( b)Fe G 1 􀆰5S ia l l oy;   ( c)Fe G 2 􀆰2S ia l l oy.

F i 􀆰6 Cr o s s G s e c t i onmi c r o r aph so ft h es e c imen sa t700 ℃ andEPMAl i n es c an ss howi ngd i s t r i bu t i on so f g g p O,S i,Mn,AlandFea c r o s sox i d es c a l e

I s sue3       Ef f e c to fS iCon t en tandTempe r a t u r eonOx i da t i onRe s i s t anc eo fFe GS iAl l oy s 

243

  Ox i des c a l ef o rmeda t1200 ℃ wa sadop t edt o d i s cus st hes c a l e mo r l ogya th i empe r a t ur e s pho ght ( ) F i 􀆰 8 . O n eo b v i o u sd i f f e r e n c e f r o mt h e s c a l em o r G g l ogyf o rmeda tl owt empe r a t ur e swa st ha tS i G r i ch pho s e wa sa l sof oundi nex t e rna lox i des c a l e.Ac G pha co rd i ngt o mapp i ng o fS ie l emen t,t hepene t r a t i on dep t ho fS i G r i ch pha s ei n t oex t e rna lox i des c a l ei n G c r e a s edf o rFe GS ia l l oywi t hh i rS icon t en t.Espe G ghe c i a l l n Fe G 2 􀆰2S ia l l oy,S i G r i ch pha s e had a lmos t yi t r a t edt hr ought heex t e rna lox i des c a l e.Ath i pene gh t empe r a t ur e sabovel i i dust empe r a t ur eo ff aya l i t e, qu

F i 􀆰7 XRDs e c t r umo fe x t e rna ls c a l ef o r g p Fe G 1 􀆰5S ia l l o t700 ℃ ya

a t i t e.I nc onc l us i on,a tl ow t empe r a t u r e s,ox i de , s c a l eo ft hea l l oyswa sc ompo s edo fIOZ c ong l omG e r a t eo ff aya l i t eand magne t i t e,andou t e rhema t i t e l aye r.Ba s edont heva r i a t i ono fS ic on t en ti nF i 􀆰 6 g , S icon t en ta ti nne rpa r to ft heex t e rna lox i des c a l e wa sh i rf o rFe G 2 􀆰2S ia l l oyc ompa r ed wi t ho t he r ghe a l l oys,wh i chimp l i edh i h e r o r t i o no ff a a l i t eo r g p y /a S iO2a ts c a l e l l oyi n t e r f a c eandt huss t r onge rab i l i t y t oi n t a c td i f f us i ono fFei onso ft heox i des c a l ea tl ow t empe r a t u r e s.

t hel i i df aya l i t ewou l dg r owi n t ot heex t e rna lox i de qu s c a l ewh i chwou l ds e r vea sf a s td i f f us i onpa t hf o rFe i ons.The r e f o r e,g r owt hr a t eo ft heex t e rna lox i de , s c a l ewa sg r e a t l c c e l e r a t ed.Me anwh i l ea tl i i dus ya qu t empe r a t ur eo ff aya l i t e,add i ng S ii n t ot hea l l oyt o enhanc ei t sox i da t i onr e s i s t anc e wa sou to fe f f e c t. Tak i ngox i des c a l ef o rmeda t1200 ℃i nFe G 2 􀆰2S ia l G l oya sanexamp l e,compos i t i ona tpos i t i onsma rked i nF i 􀆰8( d)wa sde t e c t edby WDS.Ther e su l t sa r e g , l i s t edi n Tab l e3 andt heco r r e spond i ng chemi c a l f o rmu l awe r eFe0􀆰72 O,Fe0􀆰88 O and Fe1􀆰95S iO4􀆰2 a t P1,P2andP3,r e spe c t i ve l r e f o r e,t her e l evan t y.The

( a)Fe G 0 􀆰75S ia l l oy;   ( b)Fe G 1 􀆰5S ia l l oy;   ( c)Fe G 2 􀆰2S ia l l oy;   ( d)En l a r i ewo fa r e aAi n( c). gedv

F i 􀆰8 Cr o s s G s e c t i onmi c r o r aph so fs e c imen sa t1200 ℃ andEPMA mapp i ngs howi ngd i s t r i bu t i ono f g g p S ia c r o s sox i d es c a l e Tab l e3 Compo s i t i onana l s i so fe x t e rna ls c a l ef o r y Fe G 2 􀆰2S ia l l o t1200 ℃    a t 􀆰% ya

Po s i t i on

Fe

O

S i

Al

Mn

P1

41 􀆰7001

57 􀆰6551

0 􀆰0000

0 􀆰5116

0 􀆰1332

P3

27 􀆰0808

58 􀆰4238

13 􀆰9075

0 􀆰1476

0 􀆰4403

P2

46 􀆰8231

52 􀆰8723

0 􀆰0000

0 􀆰0424

0 􀆰2622

s e swe r emagne t i t e,wus t i t eandf aya l i t e,r e spe c G pha t i ve l t he robv i ousd i f f e r enc ewa st heex G y.Thus,ano i s t enc eo fwus t i t ei nt heex t e rna lox i des c a l e when ox i da t i on pr o c e s s wa sc a r r i ed ou t above l i i dus qu t empe r a t u r eo ff aya l i t e.Pr e s enc eo f wus t i t ei nt he

s c a l ea l sop r ovedt hed i f f us i ona c c e l e r a t i nge f f e c to f l i i df aya l i t ewh i ch madet hesupp l fFei onr e l a G qu yo t i ve l t e. yadequa    Cons i de r i ngs i i f i c an te f f e c to fl i i df aya l i t e gn qu , onox i da t i onr a t eo fFe GS ia l l oy i ti sne c e s s a r o yt me a sur el i i dust empe r a t ur eo ff aya l i t e.S i G r i chex G qu t e rna lox i des c a l eo fFe G 2 􀆰2S iwa sob t a i nedf o rDSC. Asshowni nF i 􀆰9,dur i nghe a t i ngpe r i od,s i i f i G g gn c an te ndo t he rmi cp e akwa sob s e r v e da t1150 ℃ ,wh i c h imp l i edl i f i edp r oc e s so ff aya l i t e.Dur i ngcoo l i ng que , , r i od e xo t he rmi cp e akwa sf ounda t1150 ℃ wh i c h pe imp l i edso l i d i f i c a t i onp r o c e s so ff a a l i t e. I nc on c l u s i on, y

244

    J ou r na lo fI r onandS t e e lRe s e a r ch,I n t e r na t i ona l              Vo l 􀆰22 

su l t si nh i rox i da t i onr a t ebe c aus eo fl i i df ay G ghe qu a l i t ef o rma t i on. Re f e r enc e s:

4 Conc l u s i on s

[ 1]  J 􀆰S. Sh i n,J 􀆰S.Ba e,H􀆰J.Kim,H􀆰M.Le e,T 􀆰D.Le e,E 􀆰J. Lave r n i a,Z 􀆰H.Le e,Ma t e r. Sc i.Eng.A407 ( 2005)282 G 290. [ 2]  S.Tan i i,K.Yamamo t o,D.Megumi,T.Sh i ba t a,Ma t e r. guch Sc i.Eng.A308 ( 2001)250 G 257. [ 3]  S. Suzuk i,K.Yanag i ha r a,S.Yama z ak i,K.Tanaka,Y.Wa s e G da,Sur f. I n t e r f a c eAna l. 35 ( 2003)276 G 281. [ 4]  H􀆰E.Evans,D 􀆰A.Hi l t on,R 􀆰A.Ho lm,S 􀆰J.Webs t e r,Ox i d. Me t. 19 ( 1983)1 G 18. [ 5]  T.Ada ch i,G.H.Me i e r,Ox i d.Me t. 27 ( 1987)347 G 366. [ 6]  J 􀆰L.Ruan,Y.Pe i,D.Fang,Ac t a Me ch.223 ( 2012)2597 G 2607. [ 7]  Y􀆰L.Yang,C 􀆰H.Yang,S 􀆰N.L i n,C 􀆰H.Chen,W􀆰T.Ts a i, Ma t e r.Chem.Phys. 112 ( 2008)566 G 571. [ 8]  C 􀆰H.Yang,S 􀆰N. L i n,C 􀆰H. Chen,W􀆰T.Ts a i,Ox i d.Me t. 72 ( 2009)145 G 157. [ 9]  X 􀆰J. L i u,G􀆰M. Cao,Y􀆰Q.He,T. J i a,Z 􀆰Y. L i u,J. I r onS t e e l Re s. I n t. 20 ( 2013)No 􀆰11,73 G 78. [ 10]  L. Suá r e z,P. Ro d r í e z GCa l v i l l o,Y.Houb a e r t,R. Co l á s,Co r r o s. gu S c i. 52 ( 2010)2044 G 2049. [ 11]  T.Fukagawa,H.Okada,Y.Ma eha r a,I S I JI n t.34 ( 1994)

   ( 1)Theox i da t i on ma s sga i ncu r ve so ft heFe G S ia l l oysc omp l t h pa r abo l i cl aw.Pa r abo l i cr a t e y wi cons t an ti nc r e a s e swi t hi nc r e a s i ngt empe r a t u r e. ( )    2 Typ i c a lox i des c a l emo r l ogyo ft hea l G pho l oysc ons i s t so fi n t e rna lox i da t i onz one, i nne rS i G r i ch l aye randou t e rhema t i t el aye r.Above1150 ℃ ,bo t h wus t i t eandf aya l i t ea r eobs e r vedi nt heex t e rna lox G i des c a l eo fFe GS ia l l oysduet ot hef o rma t i ono fl i G q u i df aya l i t e. ( )     3 Be l ow1150 ℃ ,ox i da t i onr e s i s t anc eo fFe G S ia l l oyi simp r ovedbyi nc r e a s i ngS ic on t e n t,wh e r e a s , above1150 ℃ i nc r e a s i ngS ic on t en to ft hea l l oyr e G

3451 G 3458. [ 15]  N. B i rks,G􀆰H.Me i e r,F 􀆰S. Pe t t i t,I n t r oduc t i ont ot heHi G gh t empe r a t ur e Ox i da t i ono f Me t a l s,2nded 􀆰,Cambr i dge Un i G ve r s i t e s s,New Yo rk,2006. yPr [ 16]  S.Tan i i,K.Yamamo t o,D.Megumi,T. Sh i ba t a,Ma t e r. guch Sc i.Eng.A308 ( 2001)250 G 257. [ 17]  R.Ro l l s,M􀆰H. Shahho s s e i n i,Ox i d.Me t. 18 ( 1982)115 G 126. [ 18]  M.Fukumo t o,S.Ma eda,S.Haya sh i,T.Na r i t a,Ox i d.Me t. 55 ( 2001)401 G 422. [ 19]  R 􀆰C.Logan i,W􀆰W. Sme l t z e r,Ox i d.Me t. 3( 1971)15 G 32. [ 20]  R 􀆰C.Logan i,W􀆰W. Sme l t z e r,Ox i d.Me t. 1( 1969)3 G 21.

F i 􀆰9 L i i du st emp e r a t u r eo ff a a l i t ed e t e c t e dbyDSC g qu y

l i i dust empe r a t u r eo ff aya l i t ewa sa r ound1150 ℃. qu The r e f o r e,e f f e c to fS ic on t en tonox i da t i onr e s i s t G anc eo fFe GS ia l l oy wa sva r i ab l edepend i ngonox i da G t i ont empe r a t u r eaboveo rbe l owt h i sc r i t i c a lt empe r G a t ur e. Soadd i ngS ii n t ot hea l l oyt oimp r ovei t sox i G da t i onr e s i s t anc ewa si nva l i d whent het empe r a t ur e wa sabove1150 ℃.

906 G 911. [ 12]  X 􀆰J. L i u,G􀆰M. Cao,D 􀆰M.Ni e,Z 􀆰Y. L i u,J. I r onS t e e lRe s. I n t. 20 ( 2013)No 􀆰8,54 G 59. [ 13]  R 􀆰Y.Chen,W􀆰Y􀆰D.Yuen,I S I JI n t. 45 ( 2005)52 G 59. [ 14]  J.T ak a d a,K.Ka s h iwa i,M.Ad a c h i,J.Ma t e r.S c i. 19 ( 1984) g