phase diagram study of alloys in iron carbon chromium mo-ni

8/12/2019 Phase Diagram Study of Alloys in Iron Carbon Chromium Mo-Ni

1/13

Journal of Research of the Nalional Bureau of Standards Vol. 58, No.1 , January 1957 Research Paper 2728Phase Diagram Study of lloys in the Iron Chromium-

Molybdenum Nickel Systemc. 1. Bechtoldt and H. C. Vacher

Alloys in the iron-chromium-molybd enum-nickcl syste m were examined after qu enchingfrom 2,200, 2,000, 1800, 1,650, and 1,500 F. Compositi onal limi ts of s tability of sevenph ases were summarized in diagram s. Fe Mo was foun d. to be a s table phase; and a ternarypha se, not previously repo rte d, was id entified to ha v e the approximate compos ition of 4percent of chromium 53 percent of iron , and 43 percent of molybdenum.

1. IntroductionA study was made recently at the Bureau [1 ,2)1f the microstru ctures in austenitic sta inless steelscontaining approximately 3.5 percent of molybdemun . This study showed that the m icrocon stituen tssigma (a-), chi x), and carbides could be separatedfrom t llC alpha iron (ex Fe ) and gamma iI on (Y F e)phases by dissolution and then ident ifi ed by X -ray

diffract ion . The study also revealed a dearth ofinformation in phase diagrams that would define theranges of composition and temp erature of st ab ilityof (T and x in quaternary alloys of theiron -chromiummolybdeuum-nickel system. Accordingly , an investigation was started with the purpose of supplyinginformat ion of th is kind .Th e six binary systems involving chmmium , iron ,molybdenum , and n ickel l] ave been studied extensively, and apparenLly relia ble phase diagrams areavailable over a wide range of temperatme. However, the information on the four ternary systemswas su fficiently complet( to permit constru ct ion ofdiagrams only at 2,200 F. Obv iou sly a comprehensive investigation of the entire qua te rnary systemwould require an immense amount of work. I t wasdecided, con sequent ly, that atte ntion would befo cused on iron-chromium-molyb denum-nickcl alloysco ntaining 70 pcrce nt of iron. Th e work then wouldbe of interest in the field of heat-resist in g alloys andat the same time furn ish data to check co ntemporaryisothermal phase diagrams of the chromium-iwnmolybdenum chromium-iron-nickel, iron-molybdenum -nickel, and iron-molybdenum systems.

2. Experimental Procedures2 .1. Plan of InvestigationLimiting th e investigation to 70 -percent-ironalloys made it possible to investigate the alloys atseveral temperatures , thus making it easier to compare the results with previous investigation s. Th ea Fe and Y Fe phases have wide solubility ranges at2,500 F and the react ions that result in the formation of (T and x arc moderately fast at temperaturesabove 1,500 F. Thus equilibrium could be attainedin a reasonab le time, and the reactants could bequ ench.ed. Th e wide solubility ranges facilitatedthe p reparation of the alloys from the powdered

I Fi gul es in brac kets illelicate the li tera tu re references at the end of this paper. 7

meta ls. Seventy-percent-iron alloys, mad e fromchromium iron, molybdenum and nickel powders,whose source and purity are shown in table 1, weresin tered at 2,500 F , cooled slowly to room temperature, reheated to 2,200, 2,000, 1,800, 1,650, and1,500 F, and then quenched to room temp eratur e.A large range of co mpositions was covered (fig. 1)T An1- ,; 1. N{ nuf cturer and chemical analyses of metal powders

lVrctal powder I Ma nu facturer I Chem ieal a nalysisi\t(olyb cl cnum ___ Johnsan, & 00 _ 99.9 min im ulll.1)0 _________ _ C har les I fa rd y, Inc ___ 99.9 minim ulll.i > ickcL _________ In ternational N ickel s peetrogmg hic m et hod: 0.01Co., co ur tesy of A I, 0.00] 0, 0.001 Cu, 0.1FranciS B. Foley. Fe 0.00] M.g, 0.001 Mil,0.001 Pb 0.01 S i.

] 0 __ - - - - ____ l i c.: in tcgratingV[ etal Spectrogra phic met hod: 0. 1Co . A ], 0.001 Ca 0.0 1 Cr 0. 1Cu ,O.O ] M g, 0.001 Pb ,O. OIrl i. Che rn ieal methods:Chromiuln ______ El ectro M eta llurgical 0. 12 Co, 0.09 F e, 0.06 Si.Clwnical me thods : 0.01 C,Co., cour tC sy of 0.03 Fe 0.01 Cu, 0.01 PbR usse ll Franks. 0.0: 3 S, 0.5< 0 , 0.0]2 J [ ,0.008 N.Iron --- ---.---- Ge neral Aniline & Ca rbon yl iron : 99.6 to 99.9.Fi lm Co.Il. Va luC's a l c maximum limits. A nalyscs of nickel were maci ca LLl e Burea u;Lheolhe rs were given by lhe manufctC LUre rS.

IG U RE 1. Compositions of alloys investigated containing 70percent of iron and areas in which hard phases were foundafter sintering tl eatment at 2 500 F nd furnace cooling.


2/13


3/13

F I GURE 3. Microstnlctll1e of alloy 70 Fc-2 Cr-28 Mo ft rreheating to 2 500 Ji for 2 hours and quenching in water.Conce ntrated hydrochlor ic acid containing few drops of nit ric acid followcdy 15 seconds in cold alka lin fcrr icyanidc Jhascs identified wereda rk) surrounded by p white) in matrix (Widmanstiittcn s tru cture)

rnate bands of a and p. X1000.5, 75, 250, 500, and 1,000 hr, respectively,nd then quenching in water. Before rehea ting theat were not bri ttle were compressedder 150,000- to 200,000-lb/in .2 pressure. This opas tic deformation, redu cedro sity and accelerated the reactions during thereheating periods. In the course of examining thcreheated alloys, pa r t icularly those reheated at thcmp eratures, it was found that the microtru cture of the hard phases had changcd very l it tle;nd that, in a few alloys, the number of phasesstinguished was more than could cocxist if equilibhad been established . Normally, according tophase rule, the maximum number of phasesibrium at a temperature and pressure is 4 inqu aternary system, except when a phase transfortion occurs; then there may be 5 or in the uniquease 6 . The foregoing observat ions indicated that,t the reheating temp eratures, diffusion wi thin thehard phases or from the hard phases to the matrixwas slow ; consequently, the approach to equilibriumwas slow if several hard phases were involved. Theareas in figure 1 show the compositions inwhich the hard phases were found in the slow-cooledin te red alloys. The es tablishment of equilibrium in

lte alloys having compositions near the cluomiumron-molybdenum ternary system, particularly atgh molybdenum content s , was doubtful, and theossibility of a ttaining equilibrium was even less att lte lower temp era t ure.t was found tha t equilibrium could be approachedre readily if th e qu es tionable slow-cooled sin teredwere given a solu tion treatm ent prior to reheatng to temperatures at which equilibrium was to bettained. Th e solution treatment consisted in reting to 2,500 F , holding for 2 hr , and thenuenching in water. n th e solution-treated condition th e alloys consisted of either or both the a F e

409 709- 5 7 2 9

and Y F e phases, except those alloys whose compos itions were near the 30-percen t-molybd enum cornerof th e diagram fig. 1). These alloys contained tracesof primary E, p or a fine acicular stru cture fLg. 3),which later was found to be p precipi tated in a matrixof a Fe . The results as a whole indicated th at theproximity of equilibrium was greatcr in a shorterp eriod by precipi ta tion from th e sof t phases than byrcactions involving the hard phases. For the h eat ingperiods used in this work, it was onl)r at 2,200 Fthat both the slow- cooled sin tered and the solutiontreated specimens gave consisten t resul ts.In general, the boundar ies bet ween the area containing the a and Y phases were considered to beaccurate to X-percent-alloy composition; theboundaries b etween the hard phases were consideredto be less accurate.

2.4. Procedures for the Identific a tion of PhasesThe polishing procedUl e used in preparing thesp ec imens for etching, preliminary to microscopicexamination, was conventional except for the laststage, which consisted of eith er an electropolishing

treatment or a combination of electroly tic and mechanical m ethods. The electrolyte consisted of 70percen t of glacial acetic acid, 20 percent of aceticanhydride, and 10 percen t of perchloric acid 75strength) by volume and was used at a potent ialbet ween 40 and 50 v, dc. Th e most successful etchingreagent was alkaline ferricyanide, made to the following strength: 20 g of K 3F e CN)6 plus 20 g of KOHper 100 ml of water. This solu tion precipi tatedK 3F e CN)6 at room temp era ture because of thccomm on ion effect; but, inasmuch as sa tisfactoryresults we re being ob ta ined, no attemp t was made toadjust its concentra tion.The alkaline ferricyanide reagent was bo th sta iningand etching in its attack and was used either coldroom temp eratUl e) or hot 200 F ). Th e sequ encein which th e interference colors app eared was approxima tely the same; however, the developmen t periodsof th e co lors differed considerably as a function ofthe tempera ture of th e reagent . The final color ofth e film app eared to be copper brown , with v ariationsof hue for different constituents. The (] phase required 2 or more min in the hot solution to acquireth e brown film figs. 4 and 5) , whereas in a like period,1) was deeply etched fig. 5). Although no t shown inth is figUl e, E also was deeply etched by the hotsolution. In th e cold solution, 1) and E, wh en present ,acquired a deep copper-brown film within 10 secfigs. 6, 7,8 , and 9). The X phase reacted slightlyfaster than (] bu t was sufficiently different to permiteasy identification figs. 4 and 5) . The rate ofstaining of p was between tha t of 1) and X figs. 9 ,10 , and U ).Primary a acquired a ligh t- tan stain on prolongedetching in the hot alkaline-ferr icyanide r eagen t,whereas Y or transformed Y was not affected fig . 4).In specimens con taining hard phases that were verysensitive to the hot reagent, primary a could bedistinguished from primary Y or transformed Y eitherby previously etching wi th aqua regia fig. 6 or by


4/13

FI GURE 4. NIi cTostnrctuTe of alloy 70Fe-2l 0 -6 :\10-3 N i af ter Teheating to1 500 0 F for 500 homs.Two minutes in hot 200 F ) alkaline fe rricyanidereagent. Ph ases identified were a (light gray), ..,(white), q (nonunifonnly stained), and x (black).X250.

FIGURE 7. Substructm'e in the l phase.Alloy 70 Fe-22.5 Mo-7.5 Ni af ter Teheating to 2 200 0 F fOT 5 h01trs.lO -pClcent chromic acid elect rolytically, followedb y 10 second s in co ld alkaline ferricyanide. Ph asesidentified \yerea (white) , .. (white and sub struct ure),and da rk). XIOO.

FIG URE 5. J\ IiaostTuc tW'e of alloy 6 .50 -70 Fe-6.5 Ki-4 Mo after re heat ingto 1 500 0 F f or 500 hours.Stained 30 seco nds in hot alkalin e frrricyan id ereagent. Ph a. 3 s identified wore Y mat rix, q gray ),

X (black ), and (very sma ll pitted co nstituent).reas showing co nce n tration of q and x \\ I C prima rya a. t sintrring temperaturc, those showing co ncentration of 7J and a trace of x wero primary Y. X500.

FIG li RE 8. S1tbstntcture in the l phase.Alloy 70 Fe-26 YIo-4 Ni after re heatingto 2 000 0 F for 75 hours.lO-pcrccn t chrom ic ac id elect rolyticall y followedby 10 seconds in co ld alkaline fe rricyanidc. Phases

id entified were a white), l white with subst ru c-ture) , and da rk). X500.

FIGURE 6. NIicrostrvcture of alloy 70Fe-9 01 -18 Mo-3 l \i af teT re heating /01 8000 F for 250 hours.Aqu a regia followed by 20 second s in th e co ldalkaline fcrricyanido reagent. Phases identified werea outlin ed in.., matrix, x l ight gray), and (dark ).X250.

FIG URE 9. M icrostnlcture of alloy 7Fe-2 01 -28 Mo af ter Teheating to 2 200F for 5 hows.10 seconds in a lkaline fcrricyanidc reagen t.Ph ases id entified were a mat rix with p speckled)within the network formed by . (black). X I00.

F IGURE 10. MiC1 o stntcl1tre of alloy 70 F e-9 01 -21 Mo afterreheating to 2 000 0 F for 75 hours. FIG URE 11. Micros /r ue/w e of alloy 70 Fe-4 Or-22 Mo-4 Niaf ta Teheating to 2 0000 F for 75 hours.Aq ua regia follow ed by2 0 second s in co ld alkali ne ferrieyauide reagent . Ph asesid entified wer Ca ma trix containi ng x l ight gray) and p (black). X IOO.

10

10-percent chromic acid elec trolyt ically followed by 30 seconds in hot alkalinefe l ricyanide reagent . Ph ases id entified wcr amat rix containing Y outlined andunstained), and p (d ark ). X 250 .


5/13

I ' , , , I ' , , ,1122 0

' 10 ( . ',oj H .O, O }Pn oselI I 2 00

r - ~ iPs e u d o h el OI;lOnol

10 ..

Rh o Lo H lce Unk n own

' '12

C hi C ub ic

~ 5Co, fod . Fe . rilttr

0

0'

5 0

' 03

0

110

5 9 m a Te Irooor o I

' 00 ,4 5 4 0

Oeor,e 2 e

f UHE 12. Di actome ter charts oj the hard phases x, 7 ,


6/13

3, Structure of PhasesBecause all of the five hm'd phases encountered inthe 70-percent-iron quaternary alloys can be represented in a chromium-iron-molybdenum ternarydiagram, this type of diagram, without regard fortemperature, has been used to represent theirapproximate composition (fig, 13 ) .The well-known T phase has a tetragonal structure[4], and in the chromium-iron system T has the com

position of FeCI', and is stable below 1,508 F [5].I f considered on a temperature gradient, T has asolid-solution field [6,7] through the chromium-ironmolybdenum ternary to the chemicfil compositionFeMo [8,9] in the iron-molybdenum system, whereit is stable only above 2,160 F [10] .The X phase [11] has a low-symmetry cubic structure of the filpha-manganese type find fi chemicalformula, Fe3 6Crl2MolO [12 ,13]. Results of this investigation, discussed later, indicate thfit X has anupper limit of stability at approximately 2,150 F.The phase has a rhombohedral st ructure [14,15],and the chemical composition Fe3M02 [7 ,8,16]. TheO phase can dissolve considerable nickel [17] but verylittle chromium.The 1 phase was found , early in the work inresidues separated from the qu aternary alloys, tohave a hexagonal str ucture. This suggested thatthe struc ture of 1 was the Laves type and isomorphicwith that of FezW [15]. Kuo [18], in discussingVerSnyder s and Beattie s paper [19], in which theyreport a phase of the Laves type in a modified 12-percent-chromium stainless alloy, pointed out thatZaletaeva , et al. [20] had reported recently theexistence of FezMo. Zaletaeva found fi hard phasein a O.I-percent-carbon, 16-percent-chromium, 25-percent-nickel, 6-percent-molybdenum filloy thatWA S considered to be FezMo, but this was not con-

MoPhases Temperature RangeOF

Maximun MinimunCT Feer 1508CT eMo 28 2160

271) 175X 215 14001

Solidus 17501FeMo N Unknown

Xe36Crl Mo loF IG URE 13. Schematic representation o the compositions othe hard phases in the chromiwn-iron-molybdenum system.

2

firmed by chemical analysis. Kuo also gave additional indirect evidence of the existence of Fe2Mo.These reports are in line with the early work ofVigoroux [21], who had reported Fe2:' (0 on the basisof chemicfil analysis of residues obtained from alloysmade by reducing mixtures of iron and molybdenumoxides.The foregoing review definitely indicated theexistence of a FezMo phase, notwithstanding thefact that it is not included in the contemporarydiagram [3]. In order to determine whether or notFeMo , Fe3MoZ, and FezMo co uld be made by powdertechnique and to provide standard diffraction patterns of the and 1 phases, several iron-molybdenumalloys were investigfited.Iron-molybdenum alloys having compositions ofFeMo, Fe3Mo Z and FezMo were prepared and sintereel. Alloys FeMo and Fe3Mo z were reheated to2,690 F for 2 hI' and quenched in water. AlloyFe2Mo was heated to 2,500 F for 2 hI' and quenchedin water. Specimens then were reheated to 2,200,2,000, 1,800, 1,650, and 1,500 F , as previouslydescribed. The phases indicated by diffraction patterns obtained from the reheated specimens are listedin table 3. The FeMo alloy quenched from 2,690 Fwas CT but was O and ex Mo when quenched from2,200 F. This indicates that FeMo decomposes ata higher temperature than indicated by the ironmolybdenum diagram, providing the alloy did nottransform in quenching. The Fe3M02 alloy quenchedfrom 2,690 F was T with a trace of , but was whenquenched from 2,200 and 2,000 F. The FezMoalloy quenched from 2,500 and 2,200 F was ex andbut was ex, and T when quenched from 1,500 F.Obviously equilibrium was not established, but theresult s did indicate that at. 1,500 F , ex, and were reacting to form 1 and that 1 was not stable at 2,000F. In order to establish better the existence ofFezMo and to provide an alloy from which it co uld beseparated with minimum contamination, an alloyhaving the composition 80-percent-il'on and 20 -percent-molybdenum was prepared, sintered , and soltion-treated at 2,500 F. Quenched from 2,500 F ,this alloy was ex; from 2,200 and 2,000 F, ex and E;from 1,800 F, ex and '1; and from 1,650 and 1,500F, ex and 1 . Equilibrium was not established at.1,800 F, probably because the upper temperatureof stability of 1 is near 1,800 F .

IT

T B L E 3. Phases identified in iron-molybdenum alloysReaction tern perature 0 FAtom ratio M o

content I2,500 2,200 2,000 1,800 1,650 1,500- --WeightF eMo ______ 63Fe ,Mo ,_ . __ 55F e, lVfo_____ 46.220

(a)(b )a, 'a , '

Ea1v.lo ________ _____________________ __ _a E X, E a, Ea E a, E x , E J a Tf a 7J

Reheated to 2.690 F for 2 hr, and Quenched in water. Examination showedb Reheated to 2 690 F or 2 hr, and quenched in water. Examinatio n showed Tand trace of E.


7/13

T AR L ;; 4. Data obtained .fl'om standaTd X-ray diDrac tionpatl n f OT the . phase, F e3lvf0220 20HI d I b (C o-Ka hkl d [ b (Co- K aracl ia- radia-tion ) ti on)

-IC4110113

1,010()01211 620120210, 1120420511 9207101 3208

2,01010, 16101711, 15:l002 11 0

:l0621 1120 10

.4 deo .43,46 (\ 30,00 1,020 I. 22582.373 90 44.33 1,1 18 } 1. 2231 252,289 4 46.05 0,0212,179 117 48, 5 1 20 17 I. 2 176 152. 141 20 49,4:l 220 I. 1870 252.077 100 51. 08 2,020 1. 0894 102,0,;0 42 ,51. 79 1,1,21 1. 0874 18

}2.0:l1 52 52, 30 2, 117 I. 0834 40024 } 1. 0704I. 958 20 54. 40 30 15L 910 :l2 5:;, 90 3 1 10 1. 0424 20I 825 9 '58, 74 22 12 1.0 081 12I. 79 4 59.82 401 1. 0274 4I 78 1 GO.:lr. 3,1 Il } L 0249 IRI 732 62,20 402I 605 67,73 20,22 }1.0J541. 495 7a. 50 '1041. 4182 78 .20 405 1. 0082 6I 3889 80, 18 407 0.9902 (,I 370n 17 8 1. 47 30, 18 .9885 11I 3291i 25 84.55 4,0\0 ,9546 3I. 30,;2 23 8(; ,52 2,2 18 . 9 128 19I. 2939 22 87.41i 0021

I.2(i,;2 13 89,98 21,23 .9 071Lallier 1)(lnl lH'LCrS

o n a l ~ ~ t c l l l : ( I A , c= 25 686 A, and c a= .I), I09.Hh omb ohr dr nl sys tem: a = 8.99d 2 A, ~ H . 6 .

de(93.729:l.9994.5597,79

11 0.3911 0. fi9111. 2911 :l. ;1611 8.2011 8.99121. 05121. 56

12;J, :;0125.05129. III129.621:l9, JOl5i. 00HiO.86

S eparated from 80 F e-20 Mo ,, loy n f tc r reh ea ti n g to 2,0000 F for 75 hr . T h eF e m at r ix was di sso l ved e lec t rol yt ically in a lO -p erc e n t H C I s olu t ion.L 'I'he rela. tive height of pea k in th e dinracLomctcr chart obta in ed wi t h Co- Karadiation with respect LO stronges t line., A 11 an g les grea t e r than 58. 74 cl cg a I e to the pc a k of the Co K a, w,,,,clen g t h ,

The latt ice pRI'am ete)'s cRlc uh ted from Lhe daLaobtained from diffnlCL ion charts for the E th aL hadbeen separated from the 80-percenL-iron, 20-percentmolyb denum alloy after l'ehea ting to 2,000 0 F (ta ble4) co mpare very well with the values, a= 4.741 Aand c= 25.63 A, repo rted by Arnfelt and vVestgren[1 5]. The excellent agreement of the observed intensities, obtained for r] from the residue after rehea t ing to 1,650 0 F , with the calculated in tensitiesobtained by Ver-Snyder and Beattie (table 5) , isco nsidered to confirm that Fe2MO does exist and thatit has the Laves MgZnz t.ype of structure. Ch emicalana lysis of the separated r] (table 6) indicates tha tF e2Mo can dissolve up to 4 percent of iron at 1,650F . Similar analyses of r] separated from the quaternary Rlloys indicate that nickel and chromium alsoare soluble in the structure .The p phase , obt.ained from a quaternary alloycontaining 1 percent of nickel, was identified RSh aving a composit ion of approximately 4 percent ofchromium , 53 percent of iron , and 43 percent ofmolybdenum (table 6); but as yet the structure isunknown. This composition ha s been co nfirmed byspecially prepared alloys ( table 7) , which also indicateth at p h ilS an increased solubility field near the solidus. The d-spacing of p showed a pronounced shiftto larger va lues with the addition of molybdenum .The iron-rich co mp osition approximate s the typeformula AB2 of the L aves stru cture , consideringmolybdenum RS the A uni t and iron and chromium 13

T AR LE 5. Data obtained from standa1'd X -my di,Orartionpattern for the 1) phase, Fe2Mo

ilkl rl 29(C o- K ,0 - Calcu- radbLiol l )scn 'cd laL'd d. 1 deg100 4,100 2 0,6 25,20IO 3,624 3 :l,6 28.58

102 2.812 (; 7,0 J7,09] 10 2.369 56 56.7 44 . 37103 2, 180 100 101. 0 48. 44200 2.05:l 16 14,6 5 1. 6711 2 2,020 93 100, 0 ,2, 57201 I. 98 4 (i8 73.2 53.60004 I. 93 1 9.6 55. 19202 1. 813 5.9 59, ] j104 I. 7478 (; 8.4 61. 56203 I. G04 7 1 0,3 67. 752 11 I. 52 17 0.5 ,5 72,0010.5 I. 4464 8 4, 1 76,40300 I. 3tl89 9 n. 4 8 1. 602 13 I. :l294 50 24.5 84.57302 1,290(; 20 17 ,8 87.57006 I. 287(; 10 88. 00205 1. 23 '19 20 18. 3 n,8210(, 1. 228(i 4 2. 4 9:l. 44214 I. 2103 1 3, g,;, 30220 I. 1859 ](i 14 , 9 97.92215 I 0954 7 2,4 109, 493 12 J. 09;10 J 0, 4 109.8 420(, I. 0911 .1.8 110, 10J 13 I. 0421 1,; 9. 1 11 8.2(;401 I. 0182 :1 122. 9J224 I 0 107 ;1 124, ,5 1'102 0.9198 2 128. (i421 li .9 9 12 2 128.98108 . 91(\2 14 144. 12310 . )l 71 4 114.4 8410 h - .89(jf, 172.090

. -"""-,, -'I ". Latti cp panllrctrrsI I ('xagon ,lI s.vstC -l l : c= 7.i2 )j. \ ,c a=1. ;28,

Se para,tcd from 80 ~ c - 2 0 1 a. lloy , aftcr re heat ing'to 1,650 } ' ft) J 500 hr . The a Fe matrix was d isso l\'cdcif'ctl'olyt ica lly in a IO-perce nt II C l solilt ion.b D ata obtained frolll paLLO'll of bac k -re fl ection focusing camera.e rh e ciatiH' height of peak in ihc diffractometercha rt obtained with Co- Ka radiation wit h J csp('ct Lali ll e.d Data takcn fro m VcrSy Jl clerand TIcaLtic, Trans. Am .Soc. Me ta ls 4.7 , p . 219 (1955),

T RLE 6. Chemical analysis of single-phase Tesicillesl >


8/13

T RLE 7. Phases identified in Cr-Fe-Mo alloys containingless than 70 pe rcent of ironHeaction temperatur e (0 F)

% % %16.5 53.1 30.4 a , U a U x b t A x,tA x,tA x t A5 48.5 n 46.5 p p, ' p, , p10 43 a 47 p, ' p, , p p5 55 40 a p a p a p a p10 58 32 , p p a , P, X a p X x A5 42 a 53 ,10 40 ' 50 p p, t p5 51 a44 p p ,A

2,60 0 2, 200 2, 150 2, 125 2,100 1, 500- - -18 56 20 , U a , u , tx X, tu X Xa X-ray diffract ion data only.b t, traces; A, ot her unidentified pha se or phases present.

not agree with that for p (table 8). Goldschmidt[23], in referring to unpublished work, stated thatN was isomorphic with a phase in the chromiumcobalt-molybdenum system that has the approximat.eformula C05Cr3Moz. Rideout and Beck [24,25]reported an R phase at the approximate composition of COlOCr41107 I f cobalt and chromium areconsidered the B unit , R also approximates the AB2type formula. The diffraction pattern of R differsfrom that of the N phase. Except for a few weaklines, there is excellent agreement of the R lines withthose of the p phase (table 8). The presence of pin the chromium-iran-molybdenum system is notincompatible with that of N, but the results for theformer do indicate that N is not stable at temperatures above 1,500 F . Alloys at lower temperatureswere not investigated.The p phase has been found to precipitate in 70-percent-iron ternary and quaternary alloys havingT BLE 8. Data obtained j T m standard X -ray d1J),mction pattern for p and similar data f01 the R phase [23, 24)in the Co-Cr-Mo system

p phase H ph ase p pb ase R ph ase29 20d I/fob (CoK d Id d I/l ob (CoK d Idradiation) radiation)

A deq A deg3.36 10 30.92 ---------- - - -- I 2451 13 91. 84 -- -- - - ------ --------2.83 9 36.92 ------------ - 1. 2403 29 92.29 I 231 \I '2.78 6 37.58 -------- - -- - -- I 2331 7 93.00 ------ - -----2.659 \I ' I 2289 28 93 . 41 1. 219 w2.63 7 39.80 2.612 v\v 1.2244 7 93.862.592 vw 1. 2163 10 94.682.529 VV \V 1. 2138 11 94.94 1. 207 \V2.473 w 1.2117 7 95.152.351 15 44.74 2.337 w 1. 2088 8 95.452.3 10 10 45.60 2.291 \V 1. 1952 6 96.90

2.258 8 46.72 2.238 V\V 1.1776 5 98.852.186 w 1.1747 6 99.182.189 100 48.27 2.171 1.1585 9 101. 082.176 80 48.59 2.159 1. 1559 11 - 101. 402 151 6 49.18 1. 1432 5 102. 962.122 80 49.90 2.106 m s l. 0980 16 109.012.069 59 51. 27 2.052 Il lS 1. 0911 11 110.122.020 48 52.59 2.005 s I. 0822 15 111 . 582.003 76 53.08 1. 987 m s 1. 0736 J6 112.841. 984 41 53.64 1. 966 111S 1.0687 11 113. 631.971 22 54.05 1.954 i l l 1. 0616 14 114.821. 890 vw 1. 0450 6 117.731. 896 30 56.33 1.881 w 1. 0091 11 124.841. 860 9 57.52 l. 849 vw 0.9959 8 127.831. 784 15 60.22 1. 770 i l l V .9942 13 128. 241. 742 8 61. 82 . 9910 129.001. 505 5 73.05 . 9890 - 129.48I. 479 6 74.52 . 9835 130. 86I 430 7 77. 52 . 9757 7 132. 801. 420 4 78.14 . 9739 11 133.401.414 5 78.60 .9 722 8 133. 901. 392 5 79. 98 . 9678 5 135 . 101. 383 3 80.60 .9631 12 136.481.373 15 81. 27 .9606 8 137. 241. 368 11 81. 68 .95 82 7 137. 961. 351 9 82.89 .95 39 4 J39.341. 304 14 86.60 1. 29[ vw .9447 8 .144.641. 2903 31 87.77 1. 280 w .9256 7 150.201. 2890 25 87.83 .9175 154. 251. 2827 6 88.42 . 9127 157.061. 2785 29 88.79 I. 268 i l lW .9093 6 159.281. 2728 28 89.29 1. 263 w . 9062 4 161. 501. 2555 30 90.86 1. 246 vw . 9027 22 164. 50

Se parated from 4 Cr70 Fe-26 Mo a lloy after rebea ti ng to 2,500 F [or 2 hr, Qu enchin g ill water, and reheat illg to 2,200 F for 25 hI'.electrolyti cally in a lO pcreent HCI solution. 'fh e aJ e ma trix was d.isso1 vcdb The relative heig ht of pea k in the difl'raetometer chart ob ta ined with Co-Ka radiation \dth r espect to st rongest line .e All angles greater th an 78.60 arc to t he peak of the CO-1( 1 wav ele ngtb.d s, St rong; ms, medium strong; m, medium ; mw , m ediulTI weak; w, weak; VW, vcry weak; vvw, vcry vcry weak .- Probably higb because o[ s uperposition o[ the CO-Ka2 wave length.

4


9/13

FIG URE 14: j\ ficTostructure 65 Fe-35 Mo alloy after jeheatU1g wzthm hquulu s, 2, 675 P , and quenching in weLter .Concentrated h y d r acid ) containing [Ol drops o[ ni t ri c acid. Sholl s

V l d m a : l s tructure Xray diffractometer cha rt obtained[rom polLshed sur face md Caled that and p lI ere present . X l500.approximately ?OpeycenL of molybdenum on quenchg from the smlermg temperature. This suooeststhat the precipitfLtion obse rved by earlier w ~ ~ k e r[ 10, 16] in the iron-moly?denum binary lloysight be p An alloy conLnmll1g 65 percent of ironand 35 percent of molybdenum when quenehed from

t l ~ e m e ~ t , was found Lo cont::in a and p by X-rayl l f l r a c t l O n methods. T I ~ e m.lcro str ucture (fig. 14 )that upon sohdlflCfLtLOn, a formed first andhen p precipitated forming the WidmnnstatLentructure. ':fhe p phase nppears to be trfLn sitory oretastable m uon-molybdenum binary and iron-nickel ternary alloys sornewhfLt analoa -

If in the silver-aluminum ~ y s t e m [26] h e r ~ -p should not be indicated in the phase d i ~ g r a mthese systems .

4. Phase Diagrams4.1. he Iron-Molybdenum System

The contemporary phase diagram for the ironsystem [3] was modified to include theATOMIC PERCENT Mo

10 20 30 40 501800

30001600

14 0 26w w' '> >12 22 g51 18

800 1400600

5 iO 7 8 9 oWEI GHT PERCENT hto

G URE 15. Conlempomry phase di gmm of the iron-molybdenwn system modified to show the . phase5

pha se that ha s been tontatively desiona,Lcclas J (fig. 15 ) . The field for Fe"Mo was nas u Lo conform wiLh pre enL knowledge. b4.2. The Iron-Chromium-Molybdenum Alloys

Containing 70 and 80 Percent of Iron. The information from a survey of LhelIterature on the chromwm-Hon-molybdenum system

was summanJled 111 tempera Lure-composit ion dia (fig:s .. 16 and 17 ) for comparison with the results 111 tlus ltlVest lga t lon (figs. I S and] 9). Pu tmfLnet a1. [6] and Baen fLncl Duwez [7] indica ted e x L e n s i v ~con taining. u, whereas :M cMullin, et a1. [12]ll1clwated thIS area contained X and only smallf i e l c ~ o n t u. Goldschmid t [22], in additionto helds o n t a , 1 1 1 l ~ g e and (J a,t 1,090 F , indica,teclother fields that ll1clllcled the N phase previouslvdi scussed. .Fr?m the results for the 70-percent-i ron alloys (fig.l S) , It was concluded Lh aL there were fields con tfLining p at high t e m p ~ r a L u r e s . The upper limit of X isll1d lca,ted a,t approxuna tely.2, 150 F. This was justified by the absence of X, 111 alloys containing 15 .5 ,lS, .9.5, and 22.5 percent of mo ly bdenum, nIter rehea tulg to 2,200 F and on Lhe ba sis of results obLainecl with an lloy that cormsponded to tbe composition of X [12 ]. These resul ts (table 7) showed Xwas present at 2,150 F but not at 2,200 F . Thepresen ce of a plus (J at 2,200 and 2,150 F nd Xplus u. at 2,125 F , i ~ l d i that Lhe IS-percent chromwm , 56-percent-uon, and 26-percent-mblybdenum alloy cuLs across mono- and bi-phase fields inLhe range from 1,500 to 2,600 F.A llorizontal line was drawn sligh tly below 1 SOO F Lo indicate the lower limit of e; however, ' it isbelieved that the lowcr lim it of p is boLLer represented~ y . the euLecto d Lype. or decomposition (fig. IS ).fillS sect l.on of the chagram IS con Sid ered to betentative be cause of tile difficul ty in approximatilOequilibrium ill alloys containing 22.5 to 2S per ce ntof molybdenum. T he boundaries of fields containing X were not exLrapolated be1011 1 500 F becausethere is evid ence that X might have'a lower limit ofsta bility. The x phase was not ob served in thealloy having the x composition when reheated for16 hr at 1,400 F; furthermore, only traces of x andlarge amou n ts of J were found in the 70-percen t-ironalloys, having compositions in tbe X area outlined infigure 1, that were examined after the sin tering treatmen ts. In th e sin tering treatmen ts the cooling ratewas rapid between 2,500 and 1,5 00 F . Th eboundary between the a and a-plus-ufields wasco nnected to the point in the dnomium-iron systemindicated in the diagram by Cook and Jon es [5].The connecting cur ve appears reasonableThe results of examinations of the iron-chromiummolybdenum alloys conta ining SO percen t of iron aresummarized in figure 19 and appear consistent withthose obtained for the 70-percent-iron alloys. Theiron-chromium-molybdenum . alloys containing SOpercent of iron were prepared to help interpret andsubstantiate the results for the 70 -percen t-ironalloys , particularly those alloys whose composition


10/13

2600 0 Pu lmon, Potter, 8 Gront ,-. cMul l i n Reiter,S Ebel ing24 00 0 Baen S Ouwez 90 Goldschmidt -- -- ; ,;,-1,

-'1200 Cook6Jones ---- , ,---- I+ 5 y k e s -- I, : a-- E- ,20 0 0 ,-- b/ / ,wa:OJ>- 1800' :w-" 1600>-1400

1200

/ , I/ / ,a / a + (J ,Q+E+O' \,

I/ :1 I \,oA tl 6 cO= - ( a ~ 1/a+x . >-----,4a < ~ < ) - -: ,&. I I I / I6, .6 // ~ l I t X . c r ) / "a . c r } a , I a E(J a +O' ,

1 / - /f I Jao a + u 0 (0+ o-tN)- o( a +N r O-(a ... f: + N..-O(a+f:

1000 I I I I IC, 3 12 15 18 21 24 27 MeWEIGHT PERCENT Me

FIG U RE 16. Temperature-composit ion diagram for iron-ch romium-nwlybdenum alloys containing 70 perc ent of i1' 1LConstructed [rom data in published reports.

24 00

2200

2000-0w' 1800:OJ>-


11/13

w

o Dos 8. Be c kA Sykes

y

1800


12/13

3 r 3 r

2

3 r

3

3 Cr

CUHE 22 Phase diagrams OT i1 On-chTomium-molybdenum-nickel alloys containing 70 peTcent oj il on at 2,2 , 2, 000 1,800,1,650, and 1,5 F.

8


13/13

5. SummaryAlloys con taining 70 and 80 per cent of iron, andof chromium , molybdellum, and ickelrying from 0 to 30 and 20, respectively, were prered from known mixtu res of powdered metals,d into 2-g pellet s, and sintered in dryat 2,500 F Sintered pellets were re

2,200, 2,000, 1,800, 1,650, and 1,500and 1,000 h , respectively,quenched in water. Some pellets were reheated2,500 F before reheating at these temp cratures.e carbon content of the sintered pellets was less0. 01 perce nt, the oxygen content was 0.003 to007 percent, and the nitrogen con ten t was 0.003Two soft phases, a Fe alld Y Fe, and five hard

0 , x, , and p, were ident ified as stable coist ing phases in the iron-chromillm-mo]ybdenumThe 0 , and r/ ph ases were identifiedthe iron-molyb denum alloys and have the comsition FeMo , Fe3NIoz, and FezMo , respectively.e x and p ph ases were identified in lhe chromiumnum alloys. Th e r/ and p ph ases havebeen identified previously in the iron-molybdeand chromium-iron-molybdenum alloys, reec tively. Th e composition of p in tlle quaternaryoy containing 70 pOl'cent of iron, 4 pOl'cent ofium , 25 percent of molybd enum, and 1 perll t of 11 ickel was 53 perce n t of iron , 4 pOl'cen t ofrom iulll, and 4:3 percent of molybd enum. Th e phas been iden ti fi ed also in iron-mo lybdenumys containin g 70 percent of iron and inenum alloys, bu t only in the qu enchedndit ion.. In this co ndition tllO alloys had a charstic Widmanstaten st ructure consisti ng ofnds of a Fe and p. Diagrams were conructed to show the fields of stabili ty with respectcomposition fo r coexist ing phases in the quaterrnary , and binary alloys.

The authors are grateful fo r the assistance ofbert I . Frank , who made many of the residueparations and diffractometer charts th at werephases.

6. ReferencesThe s igma-phase inves tigation pr ogram of Sub-Commi ttee VI of Commi ttee A- I0 , Ann ual Commi tteeHe ports , Am. Soe. Test in g Materials Proc . 53, 143(1953) .H . C. Vacher and C. J. Bechto ldt, Delta ferri te -au steniter eact ions and format ion of ca rbid e, sigma, and chiphases in 18 chromium-8 nickel-3.5 molyb denum stee ls,J . Research KBS 53, 67 (1954), RP2517 .\\". P. Sy kes, Metals Handbook , 1948 ed ., p. 1210 (Am.Soe. IVleta ls, Clevelan d, Ohio).G. Bergman and D. P. Shoema ker, The spa ee group ofthe cr-FeCr erysta l stru et ur e, J. Chem. Phys . 19, 515( 195 1) .] A. J . Cook and F. \ \ . Jon es, Th e br it t le constit uent ofth e iron-ehrom ium sys tem (sigma phase), J. Iron SteelIn st . (London ) 148, 21 7 (1943) .

[6] J. 'N. P utnam, n. D. Pott er, an d K. J. Grant, Th eternary sys tem, Cr-?I o-Fe, T rans . Am. Soe. IH eLa is 43,824 (1951 ) .[7] S. H. Baen and P. DUlI ez, Const it ut ion of Fe-Cr-i\roalloys at 1,200 0 F , Trans. Am. In sL i\Tin ing :'IIet. E ng.191, 3:31 (1951) .[8] T. Takei and T. i\Tl lra kami , On t he eql lilibrium di agramof the iron-molybdenum Trans. Am. Soc.Steel Treat in g 16, 3:39 (1929) .[9] H. J GoldschmidL , A molybdenum sigma ph ase, Hesea rch (London ) 2, :143 ( 1949).[10] W. P. Sykes, Di seussion to reference [7] , Tran s. Am. Soc.Steel Treat in g 16, 358 (1929).[11] TK. Andrmys, A new interm et allie ph ase in alloyssteels, Na t ure 164, 1015 (1949) .[12 ] J. G . Me\ I ullin , S. F . Reiter, and D. G. Ebeling, Eq uili brium struetu res in Fe -Cr -M o alloys, Tra ns. Am. Soe.i\1etals 46, 799 (1954).[13] J . S. I(asper, The orde ri ng of a tom s in the ch i-phase ofthe iron-chromium-molybdenum sy s tem , Acta ;. rotallu rgica 2, 456 (1954).[].4 ] H. Arnfelt, On t ile const itu t ion of t he iron-tungs te n a ndiron-molybdenum a lJov s, Iron Steol Inst . (London )Ca rnegie Scho l. Mem . 17, 1 (1928) .[15] H . Arnfelt a nd A. Wes tg ren, De int erm ediara fasernaskris ta ll byggnad och sammansattning i ja ra-vo lframoch ja rn-molybd enlegeringer, Jernkontorets Ann. 119,185 (J 935).[16] \\". P. Sykes, T he iron-molybden um sys tem, Tra ns. Am .Soc. Steel Treat in g 10, 839 (:1926 ) .[17] Di lip Ie Das an d Paul A. Beck, Survey of portions of theiron-nickel-molybdenum a nd coba lt-iron-molyb denumte rnary sys tems at 1,200 0 C, Nat. Ad v isory Comm .Aeronau t. Tech. Note 2896 (1953).[18 ] Kehs in Euo , D iscuss ion t o re ference [19], Tran s. Am.Soc. Metals 47, 227 ( 1955) .[19 ] F. L . VerSnyde r and J. J Beatt ie, Jr . , The Lave and ehip hases in a modifi ed 12-chl"Omium st ainless a lloy,Trans. Am. Soc. Meta ls 47, 211 (1955) .[20] n. P. Zaletaeva, H. F . La shko, M. D . Neste rova, andS. A. Iuganova, A new in term eta llie comp ound in t hebinary system Fe- :'I1o, Do klady Akad. Nauk SSSR 81,415 (1951).[21] K Vigouroux, Sur les fer romolybdenes purs, Comp t.rend. 142, 889 an d 928 (1906).[22] H . J . Goldsehmid t, Ph ase diagrams of the ternary sy. temFe-Cr-W and Fe-C r-Mo at low temperat ur es, IronSteel In st. (London ) Sy mposium on high t emp eraturesteels for gas t urbin es, p. 249 (1951).[2:3] H . J Go ld schmid t, A fur ther high temp erature cr-phaseand a note O re lat ions, Hesea rch (London) 4, 343(195] ) .[24] Sheldon Paul R ideout and Paul A. Beek, Survey ofPortions of the chromium-cobalt-nickel-molyb denumquate rnary sys te m at 1,200 0 C, Nat. Adv isory Comm .Aeronaut. Teeh. Note 2683 (1952) .[25] Sheldon Rideout, W. D. Man ly, K L. Ka m en, B. S.Lement, and Paul A. Beck, Intermedia te pha ses inte rnary a lloy sys tem of tran sition elements, Trans.Am. In st. M ining Me t . E ng. 191, 872 (1951).[26 ] C. S. Barre tt, A. H . Geisler, an d R. F. Mehl , Meehanismof precipi tat ion from the solid solution of silver inaluminum , T rans. Am. Inst. Mining Met. Eng. 143,13 4 (1941).[27] W. P. Rees, B. D. Burns, a nd A. J . Cook, Con stitut ion ofiron-nickel-chromium alloys at 650 0 C to 8000 C,J . Iron Steel In st. (London) 162, 325 (1949).[28] P . Schameister and R. Ergang, Das Zusta ndsschaubildEi sen-N ickel-Chr om unter besonderer Beriicksichtingung des nack Dauerg liihunger a uft retenden spradenGe fu gebesta nd te iles, Arch. Ei senhii tt e nw. 12, 459(1939) .[29] C. H . M. J enkins, E. H. BueknaJl , C. n. Aust in, andG. A. Me llor , Th e eonstitution of the a lloys of niekel,chromium , and iron, J . Ir on Steel In st. (Lond on)136, 187 (1937).

WASHINGTON, August 7, 1956.

phase diagram study of alloys in iron carbon chromium mo-ni

Documents