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Effect of Heat Treatment on Structure and Wear Resistance of High Chromium Cast Steel Containing Boron
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ４,２ １( ５):５ ３ ２ Ｇ ５ ３ ８
Ef f e c to fHe a tTr e a tme n tonS t r u c t u r eand We a rRe s i s t anc eo f Hi omi um Ca s tS t e e lCon t a i n i ngBo r on ghChr ２ Qi Ｇ hongCEN１ , Ha i Ｇ b i nZHANG２ , Han Ｇ guangFU
( １． Schoo lo fMa t e r i a l sSc i enc eandEng i ne e r i ng,Na t i ona lEng i ne e r i ngRe s e a r chCen t e ro fWa s t eRe s ou r c e Re c ove r ngUn i ve r s i t fSc i enc eandTe chno l ogy,Kunmi ng６５００９３,Yunnan,Ch i na; ２． Schoo lo f y,Kunmi yo Ma t e r i a l sSc i enc eandEng i ne e r i ng,Be i i ngUn i ve r s i t fTe chno l ogy,Be i i ng１００１２４,Ch i na) j yo j Ab s t r a c t:Themi c r o s t r uc t u r e,me chan i c a lp r ope r t i e sandwe a rr e s i s t anc eo fh i omi umc a s ts t e e lc on t a i n i ngbo Ｇ ghchr r ona f t e rd i f f e r en the a tt r e a tmen t swe r es t ud i edbyme anso ft heop t i c a lmi c r o s c opy ( OM),t hes c ann i nge l e c t r onmi Ｇ c r o s c opy ( SEM),XＧ r ayd i f f r a c t i on ( XRD),ha r dne s s,impa c tt oughne s s,t ens i l eandp i n Ｇ on Ｇ d i s cab r a s i ont e s t s．The r e su l t sshowt ha ta s Ｇ c a s tmi c r o s t r uc t u r e so fbo r on Ｇ f r e eh i omi um s t e e lc ons i s to fma r t ens i t eandaf ew ( Cr, ghchr Fe) a r b i de,andt hema c r o Ｇha r dne s so fbo r on Ｇ f r e eh i omi ums t e e li s５５－５７HRC．Af t e r０ ５ma s s％ Bwa s ghchr ７C ３c addedi n t oh i omi umc a s ts t e e l,a s Ｇ c a s ts t r uc t u r et r ans f o rmsi n t oeu t e c t i c( Fe, Cr) Cr, Fe) C, B) nd ghchr ２B,( ７( ３a ma r t ens i t e,andt hema c r o Ｇha r dne s sr e a che s５８－６０ HRC．Hi empe r a t u r equench i ngl e adst ot hed i s c onne c t i on ght andi s o l a t edd i s t r i bu t i ono fbo r i de,andt he r ea r emany ( Cr, Fe) C, B) r e c i i t a t edpha s e si nt hequench i ngs t r uc Ｇ p ２３ ( ６p t u r e．Quench i ngf r om１０５０ ℃ ,h i omi ums t e e lob t a i nedt heh i s tha r dne s s,andt heha r dne s so fh i omi Ｇ ghchr ghe ghchr umc a s ts t e e lc on t a i n i ngbo r oni sh i rt hant ha to fbo r on Ｇ f r e eh i omi ums t e e l．Thechangeo fquench i ngt emＧ ghe ghchr r a t u r eha snoobv i ouse f f e c tonimpa c tt oughne s so fh i omi ums t e e l,andt hei nc r e a s eo fquench i ngt empe r a Ｇ pe ghchr t u r el e adst ot ens i l es t r eng t hhav i ngani nc r e a s i ngt endency．Att hes amequench i ngt empe r a t u r e,t hewe a rr e s i s t anc e o fh i omi umc a s ts t e e lc on t a i n i ngbo r oni s mo r eexc e l l en tt hant ha to fbo r on Ｇ f r e eh i omi um s t e e l．Hi ghchr ghchr gh chr omi umc a s ts t e e lgu i dec on t a i n i ngbo r onha sgoodpe r f o rmanc ewh i l eus i ngi ns t e e lba rmi l l． Ke r d s:h i omi umc a s ts t e e l;bo r ona l l oy i ng;mi c r o s t r uc t u r e,me chan i c a lp r ope r t a rr e s i s t anc e ghchr y;we ywo
Wh i t ec a s ti r onwi t hh i omi umc on t en ti s ghchr , wi de l edi n we a rapp l i c a t i ons．Howeve r wh i t e y us c a s ti r onha sl owt oughne s sandi sno ts a f ei nimpa c t we a rcond i t i on．Manya t t emp t shavebe en madet o imp r ovet he s et so f ma t e r i a l sr ega r d i ngt ough Ｇ ype ne s sandwe a rr e s i s t anc ebyadd i ngd i f f e r en ta l l oy i ng [ ] e l emen t sl i kev a n a d i um,t i t a n i um,n i ob i um,e t c１－４ ． Thema i nob e c t i veo fadd i ngadd i t i ona la l l oy i nge l e Ｇ j men t si st oa l t e rt hec a rb i des t ruc t u r eo ft hema t e r i Ｇ a l． S i z eandc ompo s i t i ono ft hec a rb i dec ana l s obea l Ｇ t e r ed us i ng d i f f e r en ts o l i d i f i c a t i on r a t e so r he a t [ ] t r e a tmen t s５－７ ．Many i nve s t i t i ons have shown ga t ha tt hede c r e a s eo fc a rbonc on t en ti sane f f e c t i ve me a sur ef o rimpr ov i ngt het oughne s so fh i o Ｇ ghchr mi umc a s ti r on．Ont heba s i so ft h i s,t he ma t e r i a l s s c i en t i s t sdeve l opedc a s th i hc h r o m i u m w e a r r e s i s t Ｇ g [ ８－１０] , an ts t e e l ．Neve r t he l e s st hevo l umef r a c t i ono f
c a rb i dei st he mos timpo r t an tpa r ame t e rt oob t a i n , we a rr e s i s t anc e a l t hough t hecompos i t i on o ft he sur r ound i ng ma t r i xa l socon t r i bu t e st ot het o t a lma Ｇ t e r i a lp r op e r t i e s． Soh i h r omi umc a s ts t e e lha sl owe r ghc we a rr e s i s t anc ebe c aus eo fl owe rc a rboncon t en tand sma l l e rc a rb i devo l umef r a c t i on．S t e e l smi c r oa l l oyed [ １１] wi t hbo r onhaveh i rdenab i l i t l l Ｇ ghha y ．Usua ybo r oni saddedi n t ot hel ow a l l oyc a s ts t e e li nt r a c e s l i ke０ ００３－０ ００５ ma s s％．The mi c r o Ｇ add i t i on o f bo r onc animp r ovet heha rdenab i l i t a n d i n c r e a s e t h e y [ , ] we a rr e s i s t anc eo fl ow a l l oy c a s ts t e e l１１ １２ ．When t hebo r on con t en ti nl ow a l l oy c a s ts t e e lexc e eds ０ ５％ ,h i hh a r d n e s sb o r i d ea e a r si nt h ea s Ｇ c a s t g pp , s t ruc t ur e andt hewe a rr e s i s t anc ec anbeobv i ous l y [ , ] i nc r e a s ed１３ １４ ． I nt hep r e s en ts t udy,ak i ndo fh i gh chr omi umc a s ts t e e lcon t a i n i ngbo r onwa sdeve l oped wh i ch ha s be t t e r we a rr e s i s t anc et han c a s th i gh
Founda t i onI t em: I t em Spons o r edbyNa t i ona lNa t ur a lSc i enc eFounda t i ono fCh i na ( ５１２７４０１６);Na t ur a lSc i enc eFounda t i ono fBe i i ngo fCh i na j ( ２１４２００９);P l anI t emo fBe i i ngEduc a t i onCommi t t e eo fCh i na ( KM２０１３１０００５００３) j B i o r aphy: Qi ＧhongCEN,Do c t o r,As s o c i a t ePr o f e s s o r; E Ｇma i l: en＠１２６ c om; Re c e i v e dDa t e:Novembe r１,２０１２ qhc g
I s sue５ Ef f e c to fHe a tTr e a tmen tonS t r uc t u r eandWe a rRe s i s t anc eo fHi omi umCa s tS t e e lCon t a i n i ngBo r on ghChr
chr omi um s t e e landh i rs t r eng t handt oughne s s ghe t hanh i h c h r o m i u m w h i t ec a s ti r o n．T h ea i m o f g r e s en ts t udyi st oi nve s t i t et hee f f e c to fquench Ｇ p ga i ngt r e a tmen ton mi c r o s t ruc t u r e,me chan i c a lp r op Ｇ e r t i e sand we a rr e s i s t anc eo fh i omi um c a s t gh chr s t e e lcon t a i n i ng bo r on．Hi omi um c a s ts t e e l gh chr c on t a i n i ngbo r onha sbe ensuc c e s s f u l l edi nt he y us r o l l i ng mi l lgu i de．
１ Exp e r imen t a lPr o c e du r e １ １ Pr e r a t i ono fs amp l e pa Thes t e e l s we r e me l t edi na mi dd l e Ｇ f r equenc y i nduc t i onf urna c ewi t hamax imum me l t i ngc apa c i t y o f１５０kg．Af t e rbe i ngdeox i d i z edwi t ha l umi n i uma t １６００－１６２０ ℃ ,t hemo l t ens t e e lwa st r ans f e r r edi n Ｇ t oap r e Ｇhe a t edl ad l e．Af t e rt her emova lo fd r o s sand s l ag,t he mo l t ens t e e lwa spou r eda t１４８０ ℃ i n t o t heme t a lmo l dst op r oduc eYＧ b l o cki ngo ta c c o r d i ng t oRe f s [ １５, １６]．The me t a lmo l dswe r ep r ehe a t ed be f o r ec a s t i ng,andt hepr ehe a t i ngt empe r a t u r ewa s ２４０ ℃ ,andt hepr ehe a t i ngt imewa s３h．Mo r eove r, h i omi um c a s ts t e e lgu i de sc on t a i n i ng bo r on ghchr we r ec a s tbyt h el o s twa xc a s t i ng me t hod． F i n a lchemi Ｇ c a lc ompos i t i ono fs amp l e si sshowni nTab l e１．The s amp l e swe r ehe a t Ｇ t r e a t eda t９００,９５０,１０００,１０５０, and１１００ ℃ f o r２h,r e spe c t i ve l o l l owedby o i l y,f c oo l i ngt ot her oomt empe r a t u r e．Then,t hes amp l e s we r et empe r eda t２００ ℃f o r６h,f o l l owedbyc oo l i ng t ot her oom t empe r a t u r ei ns t i l la i r．Me t a l l u r i c a l g s amp l e s we r ecu td i r e c t l f r o m １ ０ mm a b o v et h e y bo t t omo ft heYＧ b l o cki ngo t．Theshapeandd imen Ｇ s i ono fYＧb l o cki ngo ta r eshowni nF i １． g Tab l e１ Ch emi c a lc ompo s i t i ono fs e c imen s ma s s％ p El emen t
Bo r on Ｇ f r e e h i t e e l ghCrs
C
B
０ ３５
－
Cr
S i
Mn
Al
１０ ０６ ０ ４１０ ３２ －
Fe
Ba l anc e
Hi t e e l ghCrs ０ ３４ ０ ４６ １０ ０３ ０ ４００ ３５０ ３７ Ba l anc e c on t a i n i ngbo r on
F i １ Shap eandd imen s i ono fYＧ b l o cki ng o t g
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１ ２ Mi c r o s t r u c t u r ee xami na t i on Thei nve s t i a t i o nt e c h n i sus edf o rt he mi Ｇ g que c r os t ruc t ur echa r a c t e r i z a t i ono fc a s th i omi um ghchr s t e e li nc l udedXＧ r ayd i f f r a c t i on ( XRD),op t i c a lmi Ｇ c r os copy (OM ),ands c ann i nge l e c t r on mi c r os copy ( SEM)．Thes amp l e swe r ee t chedwi t h５％ n i t a lf o r op t i c a lmi c r os copyexami na t i on,wh i l ea mi x t ur eo f ５ mL HCl,４５ mL４％ p i c r a land５０ mL５％ n i t a l wa sus eda sane t chan tf o rSEM ana l i s．XRD wa s ys c a r r i ed on an MXP２１VAHF d i f f r a c t ome t e r wi t h coppe rKαr ad i a t i ona t４０kVand２００mA．Thes amＧ l e wa ss c annedi nt he２ θr angeo f２０ °－８０ °i na p s t ep Ｇ s c anmode ( ０ ０２ °pe rs t ep)．Theme a sur emen t o fvo l umef r a c t i ono fbo r i deandbo r oc a rb i de sus eda Le i c ad i i t a limage sana l e ront hede ep l t ched g yz ye spe c imens． １ ３ Me chan i c a lpe r f o rmanc et e s t s Thet ens i l et e s t swe r epe r f o rmedonaun i ve r s a l ma t e r i a lt e s t i ng ma ch i ne．Thed imens i onso fspe c i Ｇ e ei den t i c a lspe c Ｇ menswe r eϕ１０mm×１３０mm．Thr imenswe r et e s t ed,andt heu l t ima t et ens i l es t r eng t h wa s de t e rmi ned f r om t he l oad Ｇ d i sp l a c emen td i a Ｇ r ams．Theave r ageva l ue sf r om t hr e et e s tspe c i Ｇ g menswe r er epo r t edhe r e．Cha r t chedimpa c t pyunno t e s t swe r epe r f o rmeda tr oom t empe r a t ur eus i nga ３００Jc apa c i t ch i nef o rt hespe c imens wi t hd i Ｇ y ma mens i onso f２０mm×２０mm×１１０mm． Imp a c tt ough Ｇ n e s sva l ue swe r ea l sot heave r ageo ft hr e espe c imens． The ma c r o Ｇha rdne s st e s t i ng wa s done us i ng an MW３２ ＧHRＧ １５０ t e h a r d n e s s t e s t e r ．T h e mi c r o Ｇ yp ha rdne s swa s me a sur edby us i ng a Vi cke r s mi c r o Ｇ ha rdne s st e s t e ra tal oado f０ ５N．Atl e a s ts eveni n Ｇ den t a t i onswe r emadeone a chs amp l eunde re a chex Ｇ r imen t a lcond i t i ont oc he c kr e r odu c i b i l i t ft he pe p yo ha r dn e s sd a t a． １ ４ S l i d i ngwe a rt e s t s We a rt e s t s we r econduc t edi nan MLＧ １０t ype [ ] i n abr a s i on t e s t i ng ma ch i ne shown i nF i ２１７ ． p g Te s tl oadwa s４ ９N,t hemax imums l i d i ngd i s t anc e wa s１６ ４ m andt hes l i d i ngspe ed wa s０ １ m s－１ f o ra l lt het e s t s．Thed i skd imens i onwa s２２０mmi n d i ame t e rand５ mmi nt h i ckne s s．Thes amp l e swe r e abr adedona２８０g r i tS iCwa t e rs andpape r．Thes i z e s s o ft hespe c imens wa sϕ６ mm×２５ mm．The ma l os s e swe r eme a sur edbyus i ngas c a l ewi t h０ １ mg r e so l u t i on．Ther e l a t i ve we a rr e s i s t anc e( st he β)i r a t i oo ft he we a r ma s sl os so fcon t r a s t ma t e r i a l ( Cr １２MoVs t e e l)t ot ha to fbo r on Ｇ f r e eh i t e e l ghCrs andh i t e e lcon t a i n i ngBr e spe c t i ve l ghCrs y．
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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 ２１
１—Con t r o l l e r; ２—Load; ３— Ho l de r; ４—Spe c imen; ５—Di sk; ６—Revo l ve r．
F i ２ S ch ema t i cd r awi ngo ft h eab r a s i v ewe a rt e s t e r g
２ Re s u l t sandDi s c u s s i on ２ １ Mi c r o s t r u c t u r e and ha r dne s so fa s Ｇ c a s th i gh chr omi ums t e e lc on t a i n i ngbo r on Theso l i d i f i c a t i on mi c r o s t ruc t u r e so fbo r on Ｇ f r e e ( , h i hc h r o m i u ms t e e l c o n s i s to fα Ｇ F ea n da f e w C r g
Fe) a rb i de．Thevo l umef r a c t i ono fc a rb i de ypec ７C ３t i ssma l l e rt han１ ０vo l ％．The ma c r o Ｇha rdne s so f bo r on Ｇ f r e eh i omi ums t e e li s５５－５７HRC．The ghchr mi c r o Ｇha rdne s so fα ＧFei s５９５－６３０ HV,andt he ma t r i xi sma r t ens i t e． Af t e r０ ５ ma s s％ B wa saddedi n t oh i o Ｇ ghchr mi um c a s ts t e e l,t heso l i d i f i c a t i on mi c r os t ruc t ur e s o fh i hc h r o m i u m s t e e lc o n t a i n i n b o r o no b v i o u s l g g y changed．Unde rt he common so l i d i f i c a t i on cond i Ｇ t i on,t he r ea r e manyeu t e c t i cbo r i de sandbo r oc a r Ｇ b i de si na s Ｇ c a s ts t ruc t ur e s,a sshowni nF i ３．The g vo l umef r a c t i ono fbo r i de sandbo r oc a rb i de si sabou t ５％ －７％．The ma t r i xi s ma r t ens i t e．The mi c r o Ｇ ha rdne s so fma t r i xi s６４０－６６０ HV be c aus eo ft he s t r eng t hen i nge f f e c to fbo r on,andi ti sh i rt han ghe t ha to fbo r on Ｇ f r e eh i omi ums t e e l．Thema c r o Ｇ ghchr ha rdne s so fh i omi um s t e e lcon t a i n i ng bo r on ghchr r e a che s５８－６０ HRC．TheXRDspe c t rumi nF i ４ g showst ha tt hebo r i dei s( Fe, Cr) ndt hebo r oc a r Ｇ ２Ba ( , ) ( , ) , ( b i dei s Cr Fe ７ C B ３ ．Mo r eove r eu t e c t i c Fe, Cr) sne two rks t ruc t ur e,andeu t e c t i c( Cr, Fe) ２Bi ７ ( C, B) sd i s conne c t i onandi so l a t eds t ruc t ur e． ３i
F i ３ Mi c r o s t r u c t u r eo fa s Ｇ c a s th i r omi ums t e e lc on t a i n i ngbo r on g ghch
F i ４ XRDs e c t r umo fa s Ｇ c a s th i r omi um g p ghch s t e e lc on t a i n i ngbo r on
２ ２ Ef f e c to fqu ench i ngonmi c r o s t r u c t u r eandpr op Ｇ e r t fh i omi ums t e e lc on t a i n i ngbo r on yo ghchr Af t e ro i lquench i ngp r oc e s s i ngf r om d i f f e r en t , t empe r a t ur e st hemi c r os t ruc t ur eo fbo r on Ｇ f r e eh i gh chr omi um s t e e lha s no obv i ous change compa r ed wi t ha s Ｇ c a s t mi c r os t ruc t ur e．When quench i ngt emＧ r a t ur e exc e eds １０００ ℃ ,c r t a lg r a i n be c ame pe ys coa r s e．Howeve r,quench i ngt r e a tmen tha sobv i ous e f f e c tont hemi c r os t ruc t ur eo fh i hc h r o m i u ms t e e l g , con t a i n i ngbo r on a sshowni nF i ５．Hi empe r a Ｇ g ght t ur equench i ngl e adst ot hed i s conne c t i onandi so l a Ｇ t edd i s t r i bu t i ono fbo r i de．Theh i h e r t h e u e n c h i n g q g t empe r a t ur ei s,t he mo r eobv i oust hebr okent r end o fbo r i dene two rki s． Fu r t he rmo r e,t he r ea r emanys e Ｇ
I s sue５ Ef f e c to fHe a tTr e a tmen tonS t r uc t u r eandWe a rRe s i s t anc eo fHi omi umCa s tS t e e lCon t a i n i ngBo r on ghChr
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( a)９００ ℃ ; ( b)９５０ ℃ ; ( c)１０００ ℃ ; ( d),( e)１０５０ ℃ ; ( f)１１００ ℃．
F i ５ Mi c r o s t r u c t u r eo fh i r omi ums t e e lc on t a i n i ngbo r onqu ench i ngf r omd i f f e r en tt emp e r a t u r e s g ghch
c ondp r e c i i t a t edpha s e si nt hequench i ngs t ruc t u r e． p Theamoun to fs e c ondpr e c i i t a t edpha s e sde c r e a s ed p andt he i rs i z ei nc r e a s edwi t ht hei nc r e a s eo fquenchＧ i ngt emp e r a t u r e．Wh e nqu e n c h i ngt empe r a t u r er e a ched , １１００ ℃ t heamoun to fs e c ondp r e c i i t a t edpha s e s p de c r e a s edobv i ous l sshowni nF i ５( f)．Themi Ｇ y,a g c r o s t ruc t ur ei nF i ５( e)showst ha ts e c ondp r e c i i Ｇ g p t a t edpha s e sd i s t r i bu t edg r anu l a r l rt he ma t r i x yove andt hes i z eo fmo s to fg r a i nswa s０ ５－１ ０μm．The XRDspe c t rum o fF i ６app r ovedt ha ts e c ond p r e Ｇ g ( , ) ( , ) c i i t a t edpha s e swe r e Cr Fe ２３ C B ６ t r o Ｇ p ypebo c a rb i de s．Be c aus epa r t i a leu t e c t i cbo r i de sandbo r o Ｇ c a rb i de swe r ed i s s o l vedi n t ot he ma t r i x,wh i chl ed t ot hei nc r e a s eo fbo r on,c a rbonandchr omi umc on Ｇ c en t r a t i onsi nt hema t r i x,s ot he r ei sasma l lquan t i Ｇ t fr e t a i nedaus t en i t ei nt hequench i ngs t ruc t u r e． yo F i ７and８showt hei n f l uenc eo fquench i ng gs t empe r a t ur eont heha r dne s so fh i omi ums t e e l． ghchr I tgoe supunt i lt hequench i ngt empe r a t ur er e a che s １０５０ ℃ wh i l ec oo l i ngi nt h eo i la ndd r op sdowna st h e t empe r a t ur eexc e eds１０５０ ℃．Theha r dne s so fquen Ｇ
F i ７ Ef f e c to fqu ench i ngonmi c r o Ｇha r dn e s so f g h i r omi ums t e e l ghch
F i ８ Ef f e c to fqu ench i ngonma c r o Ｇha r dn e s so f g h i r omi ums t e e l ghch
F i ６ XRDs e c t r umo fh i r omi ums t e e l g p ghch c on t a i n i ngbo r onqu ench i ngf r om１０５０ ℃
chedh i omi ums t e e li sa f f e c t edno ton l he ghchr ybyt , mi c r os t ruc t ur e bu ta l sobyt hequan t i t i e so fbo r on, c a rbonanda l l oy i nge l emen t si n ma r t ens i t eandt he r e s i dua laus t en i t e．Whenquencheda tl owe rt empe r Ｇ , , a t ur et he r ewou l dbel e s sbo r on c a rbonanda l l o Ｇ i nge l emen t sd i s so l vedi nt heaus t en i t e,ands a t u Ｇ y r a t edbo r on,c a rbonanda l l oy i nge l emen t si n ma r Ｇ
５３６
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 ２１
t ens i t ewe r esma l la f t e rquench i ng,r e su l t i ngi nl ow ha r dne s so ft hema t e r i a l．Whenquench i ngt empe r a Ｇ , t u r eexc e eds１０５０ ℃ t he r ewou l dbet oo muchbo Ｇ r on,c a rbonanda l l oy i nge l emen t sd i s s o l vedi nt he aus t en i t e,andt heaus t en i t e wou l d be c omes t ab l e , wi t ht hede c r e a s eo fMspo i n tr e su l t i ngi n mo r er e Ｇ s i dua laus t en i t er ema i n i ngi nt he mi c r o s t ruc t u r ea f Ｇ t e rquench i ng andl owe r ha r dne s so ft he ma t e r i a l , d i s t i nc t l t ebo r on c a rbonanda l l oy i nge l e Ｇ y．Adequa men t swou l dd i s s o l vei naus t en i t ewh i cht r ans f o rms t o ma r t ens i t edu r i ngc oo l i ngandt heh i s tha r d Ｇ ghe ne s spe akwa sob t a i neda squench i ngt empe r a t u r ei s cho s ena sabou t１０５０ ℃．Mo r eove r,be c aus eo ft he ex i s t enc eo fbo r i deandt hes o l u t i ons t r eng t hen i ngo f bo r one l emen t,t hemi c r o Ｇ ha r dne s sand ma c r o Ｇ ha r d Ｇ ne s so fh i omi um c a s ts t e e lc on t a i n i ng bo r on ghchr a r eh i rt hant ho s eo fbo r on Ｇ f r e eh i omi um ghe ghchr s t e e l． F i ９s howst hee f f e c to fquench i ngt empe r a t u r e g onimpa c tt oughne s so fh i omi um s t e e l．The ghchr changeo fquench i ngt empe r a t u r eha snoobv i ouse f f Ｇ
F i ９ Ef f e c to fqu ench i ngonimpa c tt oughn e s so fh i g gh ch r omi ums t e e l( t emp e r i nga t２００ ℃ f o r６h)
e c tonimpa c tt oughne s so fh i omi um s t e e l． gh chr Howeve r,t he r ea r emo r ebo r i de si nh i hc h r o m i u m g , c a s ts t e e lcon t a i n i ng bo r on and bo r i dei s br i t t l e s e．The ex i s t enc eo f bo r i de wi l l de c r e a s et he pha t oughne s so f ma t e r i a l,sot heimpa c tt oughne s so f h i omi um c a s ts t e e lcon t a i n i ngbo r oni sl owe r ghchr t hant ha to fbo r on Ｇ f r e eh i omi ums t e e l．F i １０ ghchr g i st hef r a c t og r aphyo fimpa c ts amp l e,andt hef r a c Ｇ t ur emodeo fs amp l ei sc l e avagef r a c t ur e．Noobv i ous d imp l ei sf oundont hef r a c t ur ei n t e r f a c e,andt he f r a c t ur eo fh i omi um c a s ts t e e lcon t a i n i ngbo Ｇ ghchr r onbe l ongedt obr i t t l ef r a c t ur e．Howeve r,t he r ea r e somet e a rr i dge sont hef r a c t ur ei n t e r f a c e,sot heimＧ c tt oughne s so fh i omi um c a s ts t e e lcon t a i Ｇ pa ghchr n i ngbo r oni sh i rt hant ha to fwh i t ec a s ti r onand ghe /cm２ be exc e eds９ ０J c aus eo fi t sl owe rc a rboncon Ｇ c en t r a t i on． F i １１showst hee f f e c to fquench i ngt empe r a Ｇ g t ur eont ens i l es t r eng t ho fh i omi ums t e e l．The ghchr i nc r e a s eo fquench i ng t empe r a t ur el e adst ot ens i l e s t r eng t hhav i ng ani nc r e a s i ngt endenc i n y．The ma r e a sonsmaybede s c r i beda st ha tt heamoun to fbo Ｇ r i de sand bo r oc a rb i de sd i s so l vedi nt he ma t r i xi n Ｇ c r e a s e sandt he mo r l og i e so fbo r i de sandbo r o Ｇ pho c a rb i de schanget ober oundand mo r ei so l a t edf o r Ｇ ma t i on a st he quench i ng t empe r a t ur ei nc r e a s e s, wh i chi sshowni nF i ５．Howeve r,t he r ea r e mo r e g bo r i de si nh i hc h r o m i u m c a s ts t e e lc o n t a i n i n b o g g Ｇ , r on andbo r i dei sbr i t t l epha s e．Theex i s t enc eo fbo Ｇ r i dewi l lde c r e a s et hes t r eng t ho f ma t e r i a l,sot he t ens i l es t r eng t ho fh i omi um c a s ts t e e lc on t a i Ｇ ghchr n i ngbo r oni sl owe rt hant ha to fbo r on Ｇ f r e eh i o Ｇ ghchr mi ums t e e l．
F i １０ Impa c tf r a c t o r aphyo fbo r on Ｇ f r e eh i r omi ums t e e l( a)and g g ghch ( ) h i r omi umc a s ts t e e lc on t a i n i ngbo r on b ghch
２ ３ We a rr e s i s t anc eo fh i omi ums t e e lc on t a i Ｇ ghchr n i ngbo r on F i １２showst he ma s sl o s sandr e l a t i ve we a r g r e s i s t anc eo fh i omi um s t e e lquench i ngf r om ghchr
d i f f e r en tt empe r a t ur e s．Att hes amequench i ngt emＧ r a t ur e,t hema s sl os so fh i omi umc a s ts t e e l pe ghchr con t a i n i ng bo r oni sl owe rt hant ha to fbo r on Ｇ f r e e h i omi ums t e e l,andt hewe a rr e s i s t anc eo ft he ghchr
I s sue５ Ef f e c to fHe a tTr e a tmen tonS t r uc t u r eandWe a rRe s i s t anc eo fHi omi umCa s tS t e e lCon t a i n i ngBo r on ghChr
F i １１ Ef f e c to fqu ench i ngont en s i l es t r eng t ho fh i g gh ch r omi ums t e e l( t emp e r i nga t２００ ℃ f o r６h)
５３７
f o rme ri smo r eexc e l l en tt hant ha to ft hel a t t e r．The change o f quench i ng t empe r a t ur e ha s no obv i ous e f f e c tont hewe a rr e s i s t anc eo fh i omi ums t e e l． ghchr I nt hes ame we a rcond i t i on,t he ma s sl os so fcon Ｇ t r a s tma t e r i a l( Cr １２MoVs t e e l)i s２２ ４ mg,wh i ch i sh i robv i ous l hant ha to fh i omi umc a s t ghe yt ghchr s t e e lcon t a i n i ngbo r on,andi t sr e l a t i vewe a rr e s i s t Ｇ anc ei sl owe rt hant ha to ft hel a t t e r,a sshowni n ( ) , F i １２ b ． I nt hewe a ro fma t e r i a l st hef o rmu l af o r g compu t i ngt hewe a rr a t ei sg i venbyRe f s [ １８, １９] ( Wt＝W c＋Wf １) W c＝K１
P H
( ２)
F i １２ Ef f e c to fqu ench i ngt emp e r a t u r eonma s sl o s s( a)andr e l a t i v ewe a r g ( ) ( r e s i s t anc e b o fh i r omi ums t e e lt emp e r i nga t２００ ℃ f o r６h) ghch
P ( ３) ２ ( εfH ) whe r e,Wti st hewe a rr a t eo f ma t e r i a l s;W ci st he ; st he we a rr a t e we a rr a t ec aus ed by cu t t i ng Wf i c aus edbyf a t i sp r e s su r e;H i sha r dne s sand gue;P i εf i sf r a c t ur es t r a i na ts i ng l e ax i st ens i l et e s t i ng wh i chr e f l e c t st het oughne s s． Fr omt heaboveequa t i ons,i tc anbeno t edt ha t t hewe a ro fma t e r i a l sc ons i s t so fcu t t i ngwe a randf a Ｇ t i a rf o rh i Ｇ s t r e s sab r a s i on．Thef o rme rde Ｇ guewe gh heha r dne s so fma t e r i a l sandt hel a t t e ri s pendsont r e l a t edt ot heha r dne s sandt oughne s so f ma t e r i a l s． Hi omi umc a s ts t e e lc on t a i n i ngbo r onha sh i ghchr gh Wf＝K２
ha rdne s sb e c au s eo ft hea dd i t i ono fbo r on,andi t sma Ｇ t r i xha sa l sogoodt oughne s sbe c aus eo fi t sl owe rc a r Ｇ , boncon t en t soi t swe a rr e s i s t anc ei sexc e l l en t． SEM image so fwo r ns u r f a c ei nF i １３s howt ha tt heamoun t g o ff ur r owi sl a r t sshapei sbr oadandde ep ge,andi ont hebo r on Ｇ f r e eh i omi um s t e e l．Th i si sbe Ｇ ghchr c aus et he ha rdne s so f bo r on Ｇ f r e eh i omi um gh chr s t e e li sl owandt he r ei snoeu t e c t i cpha s eont hema Ｇ , t r i x abr a s i vepa r t i c l e sc anbee f f e c t i ve l yembedded i nt he wo rnsur f a c e,sobo r on Ｇ f r e eh i omi um ghchr s t e e lshowspoo rwe a rr e s i s t anc e．ThoughCr １２MoV s t e e lha sh i rdne s sandgoodcu t t i ng Ｇwe a rr e s i s t Ｇ ghha anc e,i t sc a rboncon t en ti sh i het oughn e s so f ghandt
F i １３ SEMima e so fwo rns u r f a c eo fbo r on Ｇ f r e eh i r omi ums t e e l( a),h i r omi umc a s ts t e e l g g ghch ghch ( ) ( ) c on t a i n i ngbo r on b andCr １２MoVs t e e lc
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 ２１
５３８
Fe) C,B) r e c i i t a t ed pha s e si nt he quench i ng p ２３ ( ６ p s t ruc t ur e,andh i h e rt e m e r a t u r e u e n c h i n l e a g p q g ds t ot heappe a r anc eo fr e t a i nedaus t en i t e． ( ３)Quench i ngf r om１０５０ ℃ ,h i omi um ghchr , s t e e l o b t a i n e dh i h e s th a r d n e s s a n dt h eh a r d n e s so f ２ ４ App l i c a t i o no fh i h c h r o m i u ms t e e l c o n t a i n i n b o r o n g g g i omi umc a s ts t e e lcon t a i n i ngbo r oni sh i r Ther o l l i ng mi l lgu i demadef r om h i omi Ｇ h ghchr ghe ghchr hant ha to fbo r on Ｇ f r e eh i omi um s t e e l．The umc a s ts t e e lc on t a i n i ngbo r onwa st e s t edont hef i n Ｇ t ghchr f quench i ng t empe r a t ur e ha s no obv i ous i sh i ngr o l l i ngs t andso fs t e e lba rmi l la t２５m/s．The change o f f e c tonimpa c tt oughne s so fh i omi ums t e e l, s e r v i c er e su l t so fgu i de sa r eshowni nF i １４．As e ghchr g hei nc r e a s eo fquench i ngt empe r a t ur el e adst o c ompa r edt oo t he rgu i de s,t hegu i deo fh i omi Ｇ andt ghchr , t ens i l es t r eng t hhav i ngani nc r e a s i ngt endenc um c a s ts t e e lc on t a i n i ng bo r on ha sh i t r eng t h y． ghs ４)Att hes amequ e n c h i ngt emp e r a t u r e,t hewe a r t oughne s sandexc e l l en twe a rr e s i s t anc eandt he rma l ( e s i s t anc eo fh i omi um c a s ts t e e lcon t a i n i ng f a t i e s i s t anc e．Mo r eove r,t he r e wa snoc r a ck, r gh chr guer r oni smo r eexc e l l en tt hant ha to fbo r on Ｇ f r e eh i spa l l i ng,ands t i ck i ngs t e e li nt heus eo fh i o Ｇ bo gh ghchr omi um s t e e l．Hi omi um c a s ts t e e lgu i de s mi umc a s ts t e e lgu i dec on t a i n i ngbo r on．The manu Ｇ chr ghchr t a i n i ng bo r ona r eus ed ont hef i n i sh i ng r o l l i ng f a c t u r i ngp r o c e s so fh i omi um c a s ts t e e lgu i de con ghchr t andso fs t e e lba rmi l la t２５m/s．Thes e r v i c el i f eo f c on t a i n i ngbo r oni ss imp l eanda si tdoe sno tc on t a i n s i omi um c a s ts t e e lgu i d e sc on t a i n i ng bo r oni s nob l ea l l oy i nge l emen t s,t hep r oduc t i onc o s ti ss i Ｇ h ghchr g ７％ h i rt hant ha to fCr １２MoVs t e e lgu i d e． n i f i c an t l owe rt hant ha to fo t he rgu i de ma t e r i a l s． ９４ ghe yl Theapp l i c a t i ono fh i omi um c a s ts t e e lgu i de ghchr Re f e r enc e s: c on t a i n i ng bo r onc ani nc r e a s e wo rkr a t eo fr o l l i ng １] M． F i l i v i c,Z．Kamb e r o v i c,M．Ko r a c,Ma t e r．T r a n s． ５２ ( ２０１１) po mi l landde c r e a s et hepr oduc t i onc o s to fr o l l edme t a l [ ３８６ Ｇ ３９０． andimp r ovet hesu r f a c equa l i t fr o l l edme t a l． yo [] , , , , ma t r i xi sl ow andt he r ei sl owf a t i Ｇwe a rr e s i s t Ｇ gue anc e,soi t s we a rr e s i s t anc ei sl owe rt hant ha to f h i omi umc a s ts t e e lc on t a i n i ngbo r on． ghchr
F i １４ Con t r a s to fgu i d e son Ｇ l i n es e r v i c er e s u l t s g
３ Conc l u s i on s ( １)As Ｇ c a s ts t r u c t u r eo fbo r on Ｇ f r e eh i h r omi Ｇ ghc ums t e e lc on s i s t so fma r t e n s i t ea ndaf ew ( Cr, Fe) ７C ３ c a rb i de,andi t sma c r o Ｇ h a r dn e s si s５５－５７ HRC．Af t e r ０ ５ ma s s％ B wa saddedi n t oh i omi um c a s t ghchr s t e e l,a s Ｇ c a s ts t ruc t u r et r ans f o rmsi n t oeu t e c t i c( Fe, nd ma r t ens i t e,andi t s Cr) Cr,Fe) C,B) ７( ３ a ２B,(
ma c r o Ｇha rdne s sr e a che s５８－６０ HRC． ( ２)Qu e n c h i ngh a snoobv i ou se f f e c tont h emi c r o Ｇ s t r u c t u r eo fbo r on Ｇ f r e eh i h c h r o m i u m s t e e l ．H i h g g t empe r a t ur e quench i ng l e adst ot he d i s c onne c t i on andi so l a t edd i s t r i bu t i ono fbo r i dei nh i omi um ghchr c a s ts t e e lcon t a i n i ngbo r on,andt he r ea r emany ( Cr,
２ K．Bouhaml a A．Had i H．Maouche H．Me r r ad i Rev．Me t Ｇ j a l l． １０８ ( ２０１１)８３ Ｇ ８８． [ H． Zh i,I n t． J．Ma t e r． D．Xi ng,YM．Gao,X ３] Z H．Huang,J Re s． １０３ ( ２０１２)６０９ Ｇ ６１２． [ ４] S． I n t h i de ch,Y．Ma t suba r a,Ma t e r．Tr ans．４９ ( ２００８)２３２２ Ｇ ２３３０． [ ５] AE．Ka r an t z a l i s,A．Leka t ou,H．Mav r o s,J．Ma t e r．Eng． Pe r f o rm． １８ ( ２００９)１７４ Ｇ １８１． [ Fu,Ma t e r． H． Zh i,J Y． Peng,HG． ６] YH．Qu,J D． Xi ng,X Le t t． ６２ ( ２００８)３０２４ Ｇ ３０２７． [ r e Me t Ｇ P．Wang,YC．Huang,Ra ７] E J．Guo,L H．Wang,L a l s１８ ( ２００９)６０６ Ｇ ６１１． [ ８] R．Ra z av i ne ad,S．F i r oo z i,S MH．Mi r baghe r i,S t e e lRe s． j I n t． ８３ ( ２０１２)８６１ Ｇ ８６９． [ ９] O N．Do a n,J A．Hawk,J H．T l c z ak,We a r２５０ Ｇ ２５１ ( ２００１) g y ４６２ Ｇ ４６９． [ １０] L M．Chang,J H．L i u,S X．Yu,Y．Chen,B．L i u,J． I r on S t e e lRe s． １４ ( ２００２)No ６,４５ Ｇ ４９． [ １１] T．Ha r a,H．As ah i,R．Uemo r i,H．Tameh i r o,I S I JI n t．４４ ( ２００４)１４３１ Ｇ １４４０． [ １２] J C．Kuang i, HG．Fu,L T．Wang,Tr ans．Ma t e r．He a t Tr e a t． ２８ ( ２００７)７８ Ｇ ８１． [ １３] X D． Song,Z Q． J i a ng,HG． Fu,Found r e c hno l． ２７ ( ２００６) yT
８０５ Ｇ ８０８． [ １４] I M．Sp i r i d i nova,Me t a l l oved．Te rm．Obr ab．Me t．２ ( １９８４) ５８ Ｇ ６１． [ １５] P F．Wu,X D． L i u,GD． Che,Y． Lu,J M．Wang,J F． L i, ( ) Found r h i n a５ ７ ２ ０ ０ ８ ６ ３ Ｇ ６ ５． yC [ １６] Z Q． J i ang,HG．Fu,J．Yang,J H．Wang,Tr ans．Ma t e r． He a tTr e a t． ２８ ( ２００７)１５８ Ｇ １６０． [ １７] NJ．Rendo ′,M．Ol s s on,We a r２６７ ( ２００９)２０５５ Ｇ ２０６１． [ １８] HG．Fu,Q．Xi ao,HF． Fu,Ma t e r． Sc i．Eng．A３９６ ( ２００５) ２０６ Ｇ ２１２． [ １９] S．Tur enne,F．Lava l l e e,J．Ma s ounave,J．Ma t e r．Sc i．２４ ( １９８９)３０２１ Ｇ ３０２８．
JOURNALOFIRON ANDSTEELRESEARCH,INTERNATIONAL２ ０ １ ４,２ １( ５):５ ３ ２ Ｇ ５ ３ ８
Ef f e c to fHe a tTr e a tme n tonS t r u c t u r eand We a rRe s i s t anc eo f Hi omi um Ca s tS t e e lCon t a i n i ngBo r on ghChr ２ Qi Ｇ hongCEN１ , Ha i Ｇ b i nZHANG２ , Han Ｇ guangFU
( １． Schoo lo fMa t e r i a l sSc i enc eandEng i ne e r i ng,Na t i ona lEng i ne e r i ngRe s e a r chCen t e ro fWa s t eRe s ou r c e Re c ove r ngUn i ve r s i t fSc i enc eandTe chno l ogy,Kunmi ng６５００９３,Yunnan,Ch i na; ２． Schoo lo f y,Kunmi yo Ma t e r i a l sSc i enc eandEng i ne e r i ng,Be i i ngUn i ve r s i t fTe chno l ogy,Be i i ng１００１２４,Ch i na) j yo j Ab s t r a c t:Themi c r o s t r uc t u r e,me chan i c a lp r ope r t i e sandwe a rr e s i s t anc eo fh i omi umc a s ts t e e lc on t a i n i ngbo Ｇ ghchr r ona f t e rd i f f e r en the a tt r e a tmen t swe r es t ud i edbyme anso ft heop t i c a lmi c r o s c opy ( OM),t hes c ann i nge l e c t r onmi Ｇ c r o s c opy ( SEM),XＧ r ayd i f f r a c t i on ( XRD),ha r dne s s,impa c tt oughne s s,t ens i l eandp i n Ｇ on Ｇ d i s cab r a s i ont e s t s．The r e su l t sshowt ha ta s Ｇ c a s tmi c r o s t r uc t u r e so fbo r on Ｇ f r e eh i omi um s t e e lc ons i s to fma r t ens i t eandaf ew ( Cr, ghchr Fe) a r b i de,andt hema c r o Ｇha r dne s so fbo r on Ｇ f r e eh i omi ums t e e li s５５－５７HRC．Af t e r０ ５ma s s％ Bwa s ghchr ７C ３c addedi n t oh i omi umc a s ts t e e l,a s Ｇ c a s ts t r uc t u r et r ans f o rmsi n t oeu t e c t i c( Fe, Cr) Cr, Fe) C, B) nd ghchr ２B,( ７( ３a ma r t ens i t e,andt hema c r o Ｇha r dne s sr e a che s５８－６０ HRC．Hi empe r a t u r equench i ngl e adst ot hed i s c onne c t i on ght andi s o l a t edd i s t r i bu t i ono fbo r i de,andt he r ea r emany ( Cr, Fe) C, B) r e c i i t a t edpha s e si nt hequench i ngs t r uc Ｇ p ２３ ( ６p t u r e．Quench i ngf r om１０５０ ℃ ,h i omi ums t e e lob t a i nedt heh i s tha r dne s s,andt heha r dne s so fh i omi Ｇ ghchr ghe ghchr umc a s ts t e e lc on t a i n i ngbo r oni sh i rt hant ha to fbo r on Ｇ f r e eh i omi ums t e e l．Thechangeo fquench i ngt emＧ ghe ghchr r a t u r eha snoobv i ouse f f e c tonimpa c tt oughne s so fh i omi ums t e e l,andt hei nc r e a s eo fquench i ngt empe r a Ｇ pe ghchr t u r el e adst ot ens i l es t r eng t hhav i ngani nc r e a s i ngt endency．Att hes amequench i ngt empe r a t u r e,t hewe a rr e s i s t anc e o fh i omi umc a s ts t e e lc on t a i n i ngbo r oni s mo r eexc e l l en tt hant ha to fbo r on Ｇ f r e eh i omi um s t e e l．Hi ghchr ghchr gh chr omi umc a s ts t e e lgu i dec on t a i n i ngbo r onha sgoodpe r f o rmanc ewh i l eus i ngi ns t e e lba rmi l l． Ke r d s:h i omi umc a s ts t e e l;bo r ona l l oy i ng;mi c r o s t r uc t u r e,me chan i c a lp r ope r t a rr e s i s t anc e ghchr y;we ywo
Wh i t ec a s ti r onwi t hh i omi umc on t en ti s ghchr , wi de l edi n we a rapp l i c a t i ons．Howeve r wh i t e y us c a s ti r onha sl owt oughne s sandi sno ts a f ei nimpa c t we a rcond i t i on．Manya t t emp t shavebe en madet o imp r ovet he s et so f ma t e r i a l sr ega r d i ngt ough Ｇ ype ne s sandwe a rr e s i s t anc ebyadd i ngd i f f e r en ta l l oy i ng [ ] e l emen t sl i kev a n a d i um,t i t a n i um,n i ob i um,e t c１－４ ． Thema i nob e c t i veo fadd i ngadd i t i ona la l l oy i nge l e Ｇ j men t si st oa l t e rt hec a rb i des t ruc t u r eo ft hema t e r i Ｇ a l． S i z eandc ompo s i t i ono ft hec a rb i dec ana l s obea l Ｇ t e r ed us i ng d i f f e r en ts o l i d i f i c a t i on r a t e so r he a t [ ] t r e a tmen t s５－７ ．Many i nve s t i t i ons have shown ga t ha tt hede c r e a s eo fc a rbonc on t en ti sane f f e c t i ve me a sur ef o rimpr ov i ngt het oughne s so fh i o Ｇ ghchr mi umc a s ti r on．Ont heba s i so ft h i s,t he ma t e r i a l s s c i en t i s t sdeve l opedc a s th i hc h r o m i u m w e a r r e s i s t Ｇ g [ ８－１０] , an ts t e e l ．Neve r t he l e s st hevo l umef r a c t i ono f
c a rb i dei st he mos timpo r t an tpa r ame t e rt oob t a i n , we a rr e s i s t anc e a l t hough t hecompos i t i on o ft he sur r ound i ng ma t r i xa l socon t r i bu t e st ot het o t a lma Ｇ t e r i a lp r op e r t i e s． Soh i h r omi umc a s ts t e e lha sl owe r ghc we a rr e s i s t anc ebe c aus eo fl owe rc a rboncon t en tand sma l l e rc a rb i devo l umef r a c t i on．S t e e l smi c r oa l l oyed [ １１] wi t hbo r onhaveh i rdenab i l i t l l Ｇ ghha y ．Usua ybo r oni saddedi n t ot hel ow a l l oyc a s ts t e e li nt r a c e s l i ke０ ００３－０ ００５ ma s s％．The mi c r o Ｇ add i t i on o f bo r onc animp r ovet heha rdenab i l i t a n d i n c r e a s e t h e y [ , ] we a rr e s i s t anc eo fl ow a l l oy c a s ts t e e l１１ １２ ．When t hebo r on con t en ti nl ow a l l oy c a s ts t e e lexc e eds ０ ５％ ,h i hh a r d n e s sb o r i d ea e a r si nt h ea s Ｇ c a s t g pp , s t ruc t ur e andt hewe a rr e s i s t anc ec anbeobv i ous l y [ , ] i nc r e a s ed１３ １４ ． I nt hep r e s en ts t udy,ak i ndo fh i gh chr omi umc a s ts t e e lcon t a i n i ngbo r onwa sdeve l oped wh i ch ha s be t t e r we a rr e s i s t anc et han c a s th i gh
Founda t i onI t em: I t em Spons o r edbyNa t i ona lNa t ur a lSc i enc eFounda t i ono fCh i na ( ５１２７４０１６);Na t ur a lSc i enc eFounda t i ono fBe i i ngo fCh i na j ( ２１４２００９);P l anI t emo fBe i i ngEduc a t i onCommi t t e eo fCh i na ( KM２０１３１０００５００３) j B i o r aphy: Qi ＧhongCEN,Do c t o r,As s o c i a t ePr o f e s s o r; E Ｇma i l: en＠１２６ c om; Re c e i v e dDa t e:Novembe r１,２０１２ qhc g
I s sue５ Ef f e c to fHe a tTr e a tmen tonS t r uc t u r eandWe a rRe s i s t anc eo fHi omi umCa s tS t e e lCon t a i n i ngBo r on ghChr
chr omi um s t e e landh i rs t r eng t handt oughne s s ghe t hanh i h c h r o m i u m w h i t ec a s ti r o n．T h ea i m o f g r e s en ts t udyi st oi nve s t i t et hee f f e c to fquench Ｇ p ga i ngt r e a tmen ton mi c r o s t ruc t u r e,me chan i c a lp r op Ｇ e r t i e sand we a rr e s i s t anc eo fh i omi um c a s t gh chr s t e e lcon t a i n i ng bo r on．Hi omi um c a s ts t e e l gh chr c on t a i n i ngbo r onha sbe ensuc c e s s f u l l edi nt he y us r o l l i ng mi l lgu i de．
１ Exp e r imen t a lPr o c e du r e １ １ Pr e r a t i ono fs amp l e pa Thes t e e l s we r e me l t edi na mi dd l e Ｇ f r equenc y i nduc t i onf urna c ewi t hamax imum me l t i ngc apa c i t y o f１５０kg．Af t e rbe i ngdeox i d i z edwi t ha l umi n i uma t １６００－１６２０ ℃ ,t hemo l t ens t e e lwa st r ans f e r r edi n Ｇ t oap r e Ｇhe a t edl ad l e．Af t e rt her emova lo fd r o s sand s l ag,t he mo l t ens t e e lwa spou r eda t１４８０ ℃ i n t o t heme t a lmo l dst op r oduc eYＧ b l o cki ngo ta c c o r d i ng t oRe f s [ １５, １６]．The me t a lmo l dswe r ep r ehe a t ed be f o r ec a s t i ng,andt hepr ehe a t i ngt empe r a t u r ewa s ２４０ ℃ ,andt hepr ehe a t i ngt imewa s３h．Mo r eove r, h i omi um c a s ts t e e lgu i de sc on t a i n i ng bo r on ghchr we r ec a s tbyt h el o s twa xc a s t i ng me t hod． F i n a lchemi Ｇ c a lc ompos i t i ono fs amp l e si sshowni nTab l e１．The s amp l e swe r ehe a t Ｇ t r e a t eda t９００,９５０,１０００,１０５０, and１１００ ℃ f o r２h,r e spe c t i ve l o l l owedby o i l y,f c oo l i ngt ot her oomt empe r a t u r e．Then,t hes amp l e s we r et empe r eda t２００ ℃f o r６h,f o l l owedbyc oo l i ng t ot her oom t empe r a t u r ei ns t i l la i r．Me t a l l u r i c a l g s amp l e s we r ecu td i r e c t l f r o m １ ０ mm a b o v et h e y bo t t omo ft heYＧ b l o cki ngo t．Theshapeandd imen Ｇ s i ono fYＧb l o cki ngo ta r eshowni nF i １． g Tab l e１ Ch emi c a lc ompo s i t i ono fs e c imen s ma s s％ p El emen t
Bo r on Ｇ f r e e h i t e e l ghCrs
C
B
０ ３５
－
Cr
S i
Mn
Al
１０ ０６ ０ ４１０ ３２ －
Fe
Ba l anc e
Hi t e e l ghCrs ０ ３４ ０ ４６ １０ ０３ ０ ４００ ３５０ ３７ Ba l anc e c on t a i n i ngbo r on
F i １ Shap eandd imen s i ono fYＧ b l o cki ng o t g
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１ ２ Mi c r o s t r u c t u r ee xami na t i on Thei nve s t i a t i o nt e c h n i sus edf o rt he mi Ｇ g que c r os t ruc t ur echa r a c t e r i z a t i ono fc a s th i omi um ghchr s t e e li nc l udedXＧ r ayd i f f r a c t i on ( XRD),op t i c a lmi Ｇ c r os copy (OM ),ands c ann i nge l e c t r on mi c r os copy ( SEM)．Thes amp l e swe r ee t chedwi t h５％ n i t a lf o r op t i c a lmi c r os copyexami na t i on,wh i l ea mi x t ur eo f ５ mL HCl,４５ mL４％ p i c r a land５０ mL５％ n i t a l wa sus eda sane t chan tf o rSEM ana l i s．XRD wa s ys c a r r i ed on an MXP２１VAHF d i f f r a c t ome t e r wi t h coppe rKαr ad i a t i ona t４０kVand２００mA．Thes amＧ l e wa ss c annedi nt he２ θr angeo f２０ °－８０ °i na p s t ep Ｇ s c anmode ( ０ ０２ °pe rs t ep)．Theme a sur emen t o fvo l umef r a c t i ono fbo r i deandbo r oc a rb i de sus eda Le i c ad i i t a limage sana l e ront hede ep l t ched g yz ye spe c imens． １ ３ Me chan i c a lpe r f o rmanc et e s t s Thet ens i l et e s t swe r epe r f o rmedonaun i ve r s a l ma t e r i a lt e s t i ng ma ch i ne．Thed imens i onso fspe c i Ｇ e ei den t i c a lspe c Ｇ menswe r eϕ１０mm×１３０mm．Thr imenswe r et e s t ed,andt heu l t ima t et ens i l es t r eng t h wa s de t e rmi ned f r om t he l oad Ｇ d i sp l a c emen td i a Ｇ r ams．Theave r ageva l ue sf r om t hr e et e s tspe c i Ｇ g menswe r er epo r t edhe r e．Cha r t chedimpa c t pyunno t e s t swe r epe r f o rmeda tr oom t empe r a t ur eus i nga ３００Jc apa c i t ch i nef o rt hespe c imens wi t hd i Ｇ y ma mens i onso f２０mm×２０mm×１１０mm． Imp a c tt ough Ｇ n e s sva l ue swe r ea l sot heave r ageo ft hr e espe c imens． The ma c r o Ｇha rdne s st e s t i ng wa s done us i ng an MW３２ ＧHRＧ １５０ t e h a r d n e s s t e s t e r ．T h e mi c r o Ｇ yp ha rdne s swa s me a sur edby us i ng a Vi cke r s mi c r o Ｇ ha rdne s st e s t e ra tal oado f０ ５N．Atl e a s ts eveni n Ｇ den t a t i onswe r emadeone a chs amp l eunde re a chex Ｇ r imen t a lcond i t i ont oc he c kr e r odu c i b i l i t ft he pe p yo ha r dn e s sd a t a． １ ４ S l i d i ngwe a rt e s t s We a rt e s t s we r econduc t edi nan MLＧ １０t ype [ ] i n abr a s i on t e s t i ng ma ch i ne shown i nF i ２１７ ． p g Te s tl oadwa s４ ９N,t hemax imums l i d i ngd i s t anc e wa s１６ ４ m andt hes l i d i ngspe ed wa s０ １ m s－１ f o ra l lt het e s t s．Thed i skd imens i onwa s２２０mmi n d i ame t e rand５ mmi nt h i ckne s s．Thes amp l e swe r e abr adedona２８０g r i tS iCwa t e rs andpape r．Thes i z e s s o ft hespe c imens wa sϕ６ mm×２５ mm．The ma l os s e swe r eme a sur edbyus i ngas c a l ewi t h０ １ mg r e so l u t i on．Ther e l a t i ve we a rr e s i s t anc e( st he β)i r a t i oo ft he we a r ma s sl os so fcon t r a s t ma t e r i a l ( Cr １２MoVs t e e l)t ot ha to fbo r on Ｇ f r e eh i t e e l ghCrs andh i t e e lcon t a i n i ngBr e spe c t i ve l ghCrs y．
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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 ２１
１—Con t r o l l e r; ２—Load; ３— Ho l de r; ４—Spe c imen; ５—Di sk; ６—Revo l ve r．
F i ２ S ch ema t i cd r awi ngo ft h eab r a s i v ewe a rt e s t e r g
２ Re s u l t sandDi s c u s s i on ２ １ Mi c r o s t r u c t u r e and ha r dne s so fa s Ｇ c a s th i gh chr omi ums t e e lc on t a i n i ngbo r on Theso l i d i f i c a t i on mi c r o s t ruc t u r e so fbo r on Ｇ f r e e ( , h i hc h r o m i u ms t e e l c o n s i s to fα Ｇ F ea n da f e w C r g
Fe) a rb i de．Thevo l umef r a c t i ono fc a rb i de ypec ７C ３t i ssma l l e rt han１ ０vo l ％．The ma c r o Ｇha rdne s so f bo r on Ｇ f r e eh i omi ums t e e li s５５－５７HRC．The ghchr mi c r o Ｇha rdne s so fα ＧFei s５９５－６３０ HV,andt he ma t r i xi sma r t ens i t e． Af t e r０ ５ ma s s％ B wa saddedi n t oh i o Ｇ ghchr mi um c a s ts t e e l,t heso l i d i f i c a t i on mi c r os t ruc t ur e s o fh i hc h r o m i u m s t e e lc o n t a i n i n b o r o no b v i o u s l g g y changed．Unde rt he common so l i d i f i c a t i on cond i Ｇ t i on,t he r ea r e manyeu t e c t i cbo r i de sandbo r oc a r Ｇ b i de si na s Ｇ c a s ts t ruc t ur e s,a sshowni nF i ３．The g vo l umef r a c t i ono fbo r i de sandbo r oc a rb i de si sabou t ５％ －７％．The ma t r i xi s ma r t ens i t e．The mi c r o Ｇ ha rdne s so fma t r i xi s６４０－６６０ HV be c aus eo ft he s t r eng t hen i nge f f e c to fbo r on,andi ti sh i rt han ghe t ha to fbo r on Ｇ f r e eh i omi ums t e e l．Thema c r o Ｇ ghchr ha rdne s so fh i omi um s t e e lcon t a i n i ng bo r on ghchr r e a che s５８－６０ HRC．TheXRDspe c t rumi nF i ４ g showst ha tt hebo r i dei s( Fe, Cr) ndt hebo r oc a r Ｇ ２Ba ( , ) ( , ) , ( b i dei s Cr Fe ７ C B ３ ．Mo r eove r eu t e c t i c Fe, Cr) sne two rks t ruc t ur e,andeu t e c t i c( Cr, Fe) ２Bi ７ ( C, B) sd i s conne c t i onandi so l a t eds t ruc t ur e． ３i
F i ３ Mi c r o s t r u c t u r eo fa s Ｇ c a s th i r omi ums t e e lc on t a i n i ngbo r on g ghch
F i ４ XRDs e c t r umo fa s Ｇ c a s th i r omi um g p ghch s t e e lc on t a i n i ngbo r on
２ ２ Ef f e c to fqu ench i ngonmi c r o s t r u c t u r eandpr op Ｇ e r t fh i omi ums t e e lc on t a i n i ngbo r on yo ghchr Af t e ro i lquench i ngp r oc e s s i ngf r om d i f f e r en t , t empe r a t ur e st hemi c r os t ruc t ur eo fbo r on Ｇ f r e eh i gh chr omi um s t e e lha s no obv i ous change compa r ed wi t ha s Ｇ c a s t mi c r os t ruc t ur e．When quench i ngt emＧ r a t ur e exc e eds １０００ ℃ ,c r t a lg r a i n be c ame pe ys coa r s e．Howeve r,quench i ngt r e a tmen tha sobv i ous e f f e c tont hemi c r os t ruc t ur eo fh i hc h r o m i u ms t e e l g , con t a i n i ngbo r on a sshowni nF i ５．Hi empe r a Ｇ g ght t ur equench i ngl e adst ot hed i s conne c t i onandi so l a Ｇ t edd i s t r i bu t i ono fbo r i de．Theh i h e r t h e u e n c h i n g q g t empe r a t ur ei s,t he mo r eobv i oust hebr okent r end o fbo r i dene two rki s． Fu r t he rmo r e,t he r ea r emanys e Ｇ
I s sue５ Ef f e c to fHe a tTr e a tmen tonS t r uc t u r eandWe a rRe s i s t anc eo fHi omi umCa s tS t e e lCon t a i n i ngBo r on ghChr
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( a)９００ ℃ ; ( b)９５０ ℃ ; ( c)１０００ ℃ ; ( d),( e)１０５０ ℃ ; ( f)１１００ ℃．
F i ５ Mi c r o s t r u c t u r eo fh i r omi ums t e e lc on t a i n i ngbo r onqu ench i ngf r omd i f f e r en tt emp e r a t u r e s g ghch
c ondp r e c i i t a t edpha s e si nt hequench i ngs t ruc t u r e． p Theamoun to fs e c ondpr e c i i t a t edpha s e sde c r e a s ed p andt he i rs i z ei nc r e a s edwi t ht hei nc r e a s eo fquenchＧ i ngt emp e r a t u r e．Wh e nqu e n c h i ngt empe r a t u r er e a ched , １１００ ℃ t heamoun to fs e c ondp r e c i i t a t edpha s e s p de c r e a s edobv i ous l sshowni nF i ５( f)．Themi Ｇ y,a g c r o s t ruc t ur ei nF i ５( e)showst ha ts e c ondp r e c i i Ｇ g p t a t edpha s e sd i s t r i bu t edg r anu l a r l rt he ma t r i x yove andt hes i z eo fmo s to fg r a i nswa s０ ５－１ ０μm．The XRDspe c t rum o fF i ６app r ovedt ha ts e c ond p r e Ｇ g ( , ) ( , ) c i i t a t edpha s e swe r e Cr Fe ２３ C B ６ t r o Ｇ p ypebo c a rb i de s．Be c aus epa r t i a leu t e c t i cbo r i de sandbo r o Ｇ c a rb i de swe r ed i s s o l vedi n t ot he ma t r i x,wh i chl ed t ot hei nc r e a s eo fbo r on,c a rbonandchr omi umc on Ｇ c en t r a t i onsi nt hema t r i x,s ot he r ei sasma l lquan t i Ｇ t fr e t a i nedaus t en i t ei nt hequench i ngs t ruc t u r e． yo F i ７and８showt hei n f l uenc eo fquench i ng gs t empe r a t ur eont heha r dne s so fh i omi ums t e e l． ghchr I tgoe supunt i lt hequench i ngt empe r a t ur er e a che s １０５０ ℃ wh i l ec oo l i ngi nt h eo i la ndd r op sdowna st h e t empe r a t ur eexc e eds１０５０ ℃．Theha r dne s so fquen Ｇ
F i ７ Ef f e c to fqu ench i ngonmi c r o Ｇha r dn e s so f g h i r omi ums t e e l ghch
F i ８ Ef f e c to fqu ench i ngonma c r o Ｇha r dn e s so f g h i r omi ums t e e l ghch
F i ６ XRDs e c t r umo fh i r omi ums t e e l g p ghch c on t a i n i ngbo r onqu ench i ngf r om１０５０ ℃
chedh i omi ums t e e li sa f f e c t edno ton l he ghchr ybyt , mi c r os t ruc t ur e bu ta l sobyt hequan t i t i e so fbo r on, c a rbonanda l l oy i nge l emen t si n ma r t ens i t eandt he r e s i dua laus t en i t e．Whenquencheda tl owe rt empe r Ｇ , , a t ur et he r ewou l dbel e s sbo r on c a rbonanda l l o Ｇ i nge l emen t sd i s so l vedi nt heaus t en i t e,ands a t u Ｇ y r a t edbo r on,c a rbonanda l l oy i nge l emen t si n ma r Ｇ
５３６
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 ２１
t ens i t ewe r esma l la f t e rquench i ng,r e su l t i ngi nl ow ha r dne s so ft hema t e r i a l．Whenquench i ngt empe r a Ｇ , t u r eexc e eds１０５０ ℃ t he r ewou l dbet oo muchbo Ｇ r on,c a rbonanda l l oy i nge l emen t sd i s s o l vedi nt he aus t en i t e,andt heaus t en i t e wou l d be c omes t ab l e , wi t ht hede c r e a s eo fMspo i n tr e su l t i ngi n mo r er e Ｇ s i dua laus t en i t er ema i n i ngi nt he mi c r o s t ruc t u r ea f Ｇ t e rquench i ng andl owe r ha r dne s so ft he ma t e r i a l , d i s t i nc t l t ebo r on c a rbonanda l l oy i nge l e Ｇ y．Adequa men t swou l dd i s s o l vei naus t en i t ewh i cht r ans f o rms t o ma r t ens i t edu r i ngc oo l i ngandt heh i s tha r d Ｇ ghe ne s spe akwa sob t a i neda squench i ngt empe r a t u r ei s cho s ena sabou t１０５０ ℃．Mo r eove r,be c aus eo ft he ex i s t enc eo fbo r i deandt hes o l u t i ons t r eng t hen i ngo f bo r one l emen t,t hemi c r o Ｇ ha r dne s sand ma c r o Ｇ ha r d Ｇ ne s so fh i omi um c a s ts t e e lc on t a i n i ng bo r on ghchr a r eh i rt hant ho s eo fbo r on Ｇ f r e eh i omi um ghe ghchr s t e e l． F i ９s howst hee f f e c to fquench i ngt empe r a t u r e g onimpa c tt oughne s so fh i omi um s t e e l．The ghchr changeo fquench i ngt empe r a t u r eha snoobv i ouse f f Ｇ
F i ９ Ef f e c to fqu ench i ngonimpa c tt oughn e s so fh i g gh ch r omi ums t e e l( t emp e r i nga t２００ ℃ f o r６h)
e c tonimpa c tt oughne s so fh i omi um s t e e l． gh chr Howeve r,t he r ea r emo r ebo r i de si nh i hc h r o m i u m g , c a s ts t e e lcon t a i n i ng bo r on and bo r i dei s br i t t l e s e．The ex i s t enc eo f bo r i de wi l l de c r e a s et he pha t oughne s so f ma t e r i a l,sot heimpa c tt oughne s so f h i omi um c a s ts t e e lcon t a i n i ngbo r oni sl owe r ghchr t hant ha to fbo r on Ｇ f r e eh i omi ums t e e l．F i １０ ghchr g i st hef r a c t og r aphyo fimpa c ts amp l e,andt hef r a c Ｇ t ur emodeo fs amp l ei sc l e avagef r a c t ur e．Noobv i ous d imp l ei sf oundont hef r a c t ur ei n t e r f a c e,andt he f r a c t ur eo fh i omi um c a s ts t e e lcon t a i n i ngbo Ｇ ghchr r onbe l ongedt obr i t t l ef r a c t ur e．Howeve r,t he r ea r e somet e a rr i dge sont hef r a c t ur ei n t e r f a c e,sot heimＧ c tt oughne s so fh i omi um c a s ts t e e lcon t a i Ｇ pa ghchr n i ngbo r oni sh i rt hant ha to fwh i t ec a s ti r onand ghe /cm２ be exc e eds９ ０J c aus eo fi t sl owe rc a rboncon Ｇ c en t r a t i on． F i １１showst hee f f e c to fquench i ngt empe r a Ｇ g t ur eont ens i l es t r eng t ho fh i omi ums t e e l．The ghchr i nc r e a s eo fquench i ng t empe r a t ur el e adst ot ens i l e s t r eng t hhav i ng ani nc r e a s i ngt endenc i n y．The ma r e a sonsmaybede s c r i beda st ha tt heamoun to fbo Ｇ r i de sand bo r oc a rb i de sd i s so l vedi nt he ma t r i xi n Ｇ c r e a s e sandt he mo r l og i e so fbo r i de sandbo r o Ｇ pho c a rb i de schanget ober oundand mo r ei so l a t edf o r Ｇ ma t i on a st he quench i ng t empe r a t ur ei nc r e a s e s, wh i chi sshowni nF i ５．Howeve r,t he r ea r e mo r e g bo r i de si nh i hc h r o m i u m c a s ts t e e lc o n t a i n i n b o g g Ｇ , r on andbo r i dei sbr i t t l epha s e．Theex i s t enc eo fbo Ｇ r i dewi l lde c r e a s et hes t r eng t ho f ma t e r i a l,sot he t ens i l es t r eng t ho fh i omi um c a s ts t e e lc on t a i Ｇ ghchr n i ngbo r oni sl owe rt hant ha to fbo r on Ｇ f r e eh i o Ｇ ghchr mi ums t e e l．
F i １０ Impa c tf r a c t o r aphyo fbo r on Ｇ f r e eh i r omi ums t e e l( a)and g g ghch ( ) h i r omi umc a s ts t e e lc on t a i n i ngbo r on b ghch
２ ３ We a rr e s i s t anc eo fh i omi ums t e e lc on t a i Ｇ ghchr n i ngbo r on F i １２showst he ma s sl o s sandr e l a t i ve we a r g r e s i s t anc eo fh i omi um s t e e lquench i ngf r om ghchr
d i f f e r en tt empe r a t ur e s．Att hes amequench i ngt emＧ r a t ur e,t hema s sl os so fh i omi umc a s ts t e e l pe ghchr con t a i n i ng bo r oni sl owe rt hant ha to fbo r on Ｇ f r e e h i omi ums t e e l,andt hewe a rr e s i s t anc eo ft he ghchr
I s sue５ Ef f e c to fHe a tTr e a tmen tonS t r uc t u r eandWe a rRe s i s t anc eo fHi omi umCa s tS t e e lCon t a i n i ngBo r on ghChr
F i １１ Ef f e c to fqu ench i ngont en s i l es t r eng t ho fh i g gh ch r omi ums t e e l( t emp e r i nga t２００ ℃ f o r６h)
５３７
f o rme ri smo r eexc e l l en tt hant ha to ft hel a t t e r．The change o f quench i ng t empe r a t ur e ha s no obv i ous e f f e c tont hewe a rr e s i s t anc eo fh i omi ums t e e l． ghchr I nt hes ame we a rcond i t i on,t he ma s sl os so fcon Ｇ t r a s tma t e r i a l( Cr １２MoVs t e e l)i s２２ ４ mg,wh i ch i sh i robv i ous l hant ha to fh i omi umc a s t ghe yt ghchr s t e e lcon t a i n i ngbo r on,andi t sr e l a t i vewe a rr e s i s t Ｇ anc ei sl owe rt hant ha to ft hel a t t e r,a sshowni n ( ) , F i １２ b ． I nt hewe a ro fma t e r i a l st hef o rmu l af o r g compu t i ngt hewe a rr a t ei sg i venbyRe f s [ １８, １９] ( Wt＝W c＋Wf １) W c＝K１
P H
( ２)
F i １２ Ef f e c to fqu ench i ngt emp e r a t u r eonma s sl o s s( a)andr e l a t i v ewe a r g ( ) ( r e s i s t anc e b o fh i r omi ums t e e lt emp e r i nga t２００ ℃ f o r６h) ghch
P ( ３) ２ ( εfH ) whe r e,Wti st hewe a rr a t eo f ma t e r i a l s;W ci st he ; st he we a rr a t e we a rr a t ec aus ed by cu t t i ng Wf i c aus edbyf a t i sp r e s su r e;H i sha r dne s sand gue;P i εf i sf r a c t ur es t r a i na ts i ng l e ax i st ens i l et e s t i ng wh i chr e f l e c t st het oughne s s． Fr omt heaboveequa t i ons,i tc anbeno t edt ha t t hewe a ro fma t e r i a l sc ons i s t so fcu t t i ngwe a randf a Ｇ t i a rf o rh i Ｇ s t r e s sab r a s i on．Thef o rme rde Ｇ guewe gh heha r dne s so fma t e r i a l sandt hel a t t e ri s pendsont r e l a t edt ot heha r dne s sandt oughne s so f ma t e r i a l s． Hi omi umc a s ts t e e lc on t a i n i ngbo r onha sh i ghchr gh Wf＝K２
ha rdne s sb e c au s eo ft hea dd i t i ono fbo r on,andi t sma Ｇ t r i xha sa l sogoodt oughne s sbe c aus eo fi t sl owe rc a r Ｇ , boncon t en t soi t swe a rr e s i s t anc ei sexc e l l en t． SEM image so fwo r ns u r f a c ei nF i １３s howt ha tt heamoun t g o ff ur r owi sl a r t sshapei sbr oadandde ep ge,andi ont hebo r on Ｇ f r e eh i omi um s t e e l．Th i si sbe Ｇ ghchr c aus et he ha rdne s so f bo r on Ｇ f r e eh i omi um gh chr s t e e li sl owandt he r ei snoeu t e c t i cpha s eont hema Ｇ , t r i x abr a s i vepa r t i c l e sc anbee f f e c t i ve l yembedded i nt he wo rnsur f a c e,sobo r on Ｇ f r e eh i omi um ghchr s t e e lshowspoo rwe a rr e s i s t anc e．ThoughCr １２MoV s t e e lha sh i rdne s sandgoodcu t t i ng Ｇwe a rr e s i s t Ｇ ghha anc e,i t sc a rboncon t en ti sh i het oughn e s so f ghandt
F i １３ SEMima e so fwo rns u r f a c eo fbo r on Ｇ f r e eh i r omi ums t e e l( a),h i r omi umc a s ts t e e l g g ghch ghch ( ) ( ) c on t a i n i ngbo r on b andCr １２MoVs t e e lc
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 ２１
５３８
Fe) C,B) r e c i i t a t ed pha s e si nt he quench i ng p ２３ ( ６ p s t ruc t ur e,andh i h e rt e m e r a t u r e u e n c h i n l e a g p q g ds t ot heappe a r anc eo fr e t a i nedaus t en i t e． ( ３)Quench i ngf r om１０５０ ℃ ,h i omi um ghchr , s t e e l o b t a i n e dh i h e s th a r d n e s s a n dt h eh a r d n e s so f ２ ４ App l i c a t i o no fh i h c h r o m i u ms t e e l c o n t a i n i n b o r o n g g g i omi umc a s ts t e e lcon t a i n i ngbo r oni sh i r Ther o l l i ng mi l lgu i demadef r om h i omi Ｇ h ghchr ghe ghchr hant ha to fbo r on Ｇ f r e eh i omi um s t e e l．The umc a s ts t e e lc on t a i n i ngbo r onwa st e s t edont hef i n Ｇ t ghchr f quench i ng t empe r a t ur e ha s no obv i ous i sh i ngr o l l i ngs t andso fs t e e lba rmi l la t２５m/s．The change o f f e c tonimpa c tt oughne s so fh i omi ums t e e l, s e r v i c er e su l t so fgu i de sa r eshowni nF i １４．As e ghchr g hei nc r e a s eo fquench i ngt empe r a t ur el e adst o c ompa r edt oo t he rgu i de s,t hegu i deo fh i omi Ｇ andt ghchr , t ens i l es t r eng t hhav i ngani nc r e a s i ngt endenc um c a s ts t e e lc on t a i n i ng bo r on ha sh i t r eng t h y． ghs ４)Att hes amequ e n c h i ngt emp e r a t u r e,t hewe a r t oughne s sandexc e l l en twe a rr e s i s t anc eandt he rma l ( e s i s t anc eo fh i omi um c a s ts t e e lcon t a i n i ng f a t i e s i s t anc e．Mo r eove r,t he r e wa snoc r a ck, r gh chr guer r oni smo r eexc e l l en tt hant ha to fbo r on Ｇ f r e eh i spa l l i ng,ands t i ck i ngs t e e li nt heus eo fh i o Ｇ bo gh ghchr omi um s t e e l．Hi omi um c a s ts t e e lgu i de s mi umc a s ts t e e lgu i dec on t a i n i ngbo r on．The manu Ｇ chr ghchr t a i n i ng bo r ona r eus ed ont hef i n i sh i ng r o l l i ng f a c t u r i ngp r o c e s so fh i omi um c a s ts t e e lgu i de con ghchr t andso fs t e e lba rmi l la t２５m/s．Thes e r v i c el i f eo f c on t a i n i ngbo r oni ss imp l eanda si tdoe sno tc on t a i n s i omi um c a s ts t e e lgu i d e sc on t a i n i ng bo r oni s nob l ea l l oy i nge l emen t s,t hep r oduc t i onc o s ti ss i Ｇ h ghchr g ７％ h i rt hant ha to fCr １２MoVs t e e lgu i d e． n i f i c an t l owe rt hant ha to fo t he rgu i de ma t e r i a l s． ９４ ghe yl Theapp l i c a t i ono fh i omi um c a s ts t e e lgu i de ghchr Re f e r enc e s: c on t a i n i ng bo r onc ani nc r e a s e wo rkr a t eo fr o l l i ng １] M． F i l i v i c,Z．Kamb e r o v i c,M．Ko r a c,Ma t e r．T r a n s． ５２ ( ２０１１) po mi l landde c r e a s et hepr oduc t i onc o s to fr o l l edme t a l [ ３８６ Ｇ ３９０． andimp r ovet hesu r f a c equa l i t fr o l l edme t a l． yo [] , , , , ma t r i xi sl ow andt he r ei sl owf a t i Ｇwe a rr e s i s t Ｇ gue anc e,soi t s we a rr e s i s t anc ei sl owe rt hant ha to f h i omi umc a s ts t e e lc on t a i n i ngbo r on． ghchr
F i １４ Con t r a s to fgu i d e son Ｇ l i n es e r v i c er e s u l t s g
３ Conc l u s i on s ( １)As Ｇ c a s ts t r u c t u r eo fbo r on Ｇ f r e eh i h r omi Ｇ ghc ums t e e lc on s i s t so fma r t e n s i t ea ndaf ew ( Cr, Fe) ７C ３ c a rb i de,andi t sma c r o Ｇ h a r dn e s si s５５－５７ HRC．Af t e r ０ ５ ma s s％ B wa saddedi n t oh i omi um c a s t ghchr s t e e l,a s Ｇ c a s ts t ruc t u r et r ans f o rmsi n t oeu t e c t i c( Fe, nd ma r t ens i t e,andi t s Cr) Cr,Fe) C,B) ７( ３ a ２B,(
ma c r o Ｇha rdne s sr e a che s５８－６０ HRC． ( ２)Qu e n c h i ngh a snoobv i ou se f f e c tont h emi c r o Ｇ s t r u c t u r eo fbo r on Ｇ f r e eh i h c h r o m i u m s t e e l ．H i h g g t empe r a t ur e quench i ng l e adst ot he d i s c onne c t i on andi so l a t edd i s t r i bu t i ono fbo r i dei nh i omi um ghchr c a s ts t e e lcon t a i n i ngbo r on,andt he r ea r emany ( Cr,
２ K．Bouhaml a A．Had i H．Maouche H．Me r r ad i Rev．Me t Ｇ j a l l． １０８ ( ２０１１)８３ Ｇ ８８． [ H． Zh i,I n t． J．Ma t e r． D．Xi ng,YM．Gao,X ３] Z H．Huang,J Re s． １０３ ( ２０１２)６０９ Ｇ ６１２． [ ４] S． I n t h i de ch,Y．Ma t suba r a,Ma t e r．Tr ans．４９ ( ２００８)２３２２ Ｇ ２３３０． [ ５] AE．Ka r an t z a l i s,A．Leka t ou,H．Mav r o s,J．Ma t e r．Eng． Pe r f o rm． １８ ( ２００９)１７４ Ｇ １８１． [ Fu,Ma t e r． H． Zh i,J Y． Peng,HG． ６] YH．Qu,J D． Xi ng,X Le t t． ６２ ( ２００８)３０２４ Ｇ ３０２７． [ r e Me t Ｇ P．Wang,YC．Huang,Ra ７] E J．Guo,L H．Wang,L a l s１８ ( ２００９)６０６ Ｇ ６１１． [ ８] R．Ra z av i ne ad,S．F i r oo z i,S MH．Mi r baghe r i,S t e e lRe s． j I n t． ８３ ( ２０１２)８６１ Ｇ ８６９． [ ９] O N．Do a n,J A．Hawk,J H．T l c z ak,We a r２５０ Ｇ ２５１ ( ２００１) g y ４６２ Ｇ ４６９． [ １０] L M．Chang,J H．L i u,S X．Yu,Y．Chen,B．L i u,J． I r on S t e e lRe s． １４ ( ２００２)No ６,４５ Ｇ ４９． [ １１] T．Ha r a,H．As ah i,R．Uemo r i,H．Tameh i r o,I S I JI n t．４４ ( ２００４)１４３１ Ｇ １４４０． [ １２] J C．Kuang i, HG．Fu,L T．Wang,Tr ans．Ma t e r．He a t Tr e a t． ２８ ( ２００７)７８ Ｇ ８１． [ １３] X D． Song,Z Q． J i a ng,HG． Fu,Found r e c hno l． ２７ ( ２００６) yT
８０５ Ｇ ８０８． [ １４] I M．Sp i r i d i nova,Me t a l l oved．Te rm．Obr ab．Me t．２ ( １９８４) ５８ Ｇ ６１． [ １５] P F．Wu,X D． L i u,GD． Che,Y． Lu,J M．Wang,J F． L i, ( ) Found r h i n a５ ７ ２ ０ ０ ８ ６ ３ Ｇ ６ ５． yC [ １６] Z Q． J i ang,HG．Fu,J．Yang,J H．Wang,Tr ans．Ma t e r． He a tTr e a t． ２８ ( ２００７)１５８ Ｇ １６０． [ １７] NJ．Rendo ′,M．Ol s s on,We a r２６７ ( ２００９)２０５５ Ｇ ２０６１． [ １８] HG．Fu,Q．Xi ao,HF． Fu,Ma t e r． Sc i．Eng．A３９６ ( ２００５) ２０６ Ｇ ２１２． [ １９] S．Tur enne,F．Lava l l e e,J．Ma s ounave,J．Ma t e r．Sc i．２４ ( １９８９)３０２１ Ｇ ３０２８．