Lawrence Berkeley National Laboratory Recent Work
Title A THERMODYNAMIC ANALYSIS OF THE Cr-C-O, Mo-C-O, AND W-C-O SYSTEMS
Permalink https://escholarship.org/uc/item/0ks8c2ms
Author Worrell, Wayne L.
Publication Date 1964-08-01
eScholarship.org Powered by the California Digital Library University of California UCRL-11609
University of California
Ernest 0. Lawrence Radiation laboratory
A THERMODYNAMIC ANALYSIS OF THE Cr-C-0, Mo-C-0, AND W -C-O SYSTEMS
TWO-WEEK lOAN COPY This is a Library Circulating Copy which may be borrowed for two weeks. For a personal retention copy, call Tech. Info. Division, Ext. 5545
Berkeley, California DISCLAIMER
This document was prepared as an account of work sponsored by the United States Government. While this document is believed to contain correct information, neither the United States Government nor any agency thereof, nor the Regents of the University of California, nor any of their employees, makes any warranty, express or implied, or assumes any legal responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by its trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof, or the Regents of the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof or the Regents of the University of California.. ------, -r=1 To be pub_2is~ed_m Trans. Met. :~c:_ ~IME. _;-____....f
. ; tiCRL-11609
UNIVERSITY OF CALIFORNIA Lawrence Radiation Laboratory 1 Berkeley, California
!
' \
·· ... '•·· I .. /
,· ·---...... ;,_~
.A THERMODYNAMIC ANALYSIS OF THE Cr-C-0, Mo-C-0, AND
-~·. : . . W-C-0- SYSTEMS .t Wayne L. Worrell : Au-gust, 1964 .. :...... r UCRL.- 11609
A TherJ?odynamic Analysis of the C~':'~-o,.·Mo-C-0,· and r . ·' .. W-C-0 Systems· ,.
...... ' : ~. •...... · Wayne L ... Worrell.: .
. ...
•. I, •
. . . ' .. ' .{\bstract ·, .. _ . . ' ·. ~ . '. . Thermodynamic data for the stable carbides and oxides ..
of chromium, moly;bdenum, and tungsten have been critically ·,:··· evaluated and are used to deternw.ne tqe :stable condensed phases ~ .. ·. ·. ~ n .. . . 1, . at one atmosphere total pressurE( in each metal-carbon-oxygen.·
system. Pourbaix-:-Ellingham .diagrams have been constructed
.\ and are used to estimate the minimum temperatures necessary.· .·· .. _··,. : "· ~ ' .. to obtain these metals by carbothermic reduction under reduced ' ' .· .. '
pressures.
·.··.··
~; '• .
·~:. :·. -· .' . ' . :; . . .. ~ . . -·; . ';.; ..... , .
... ': ,. Wayne L. Worrell; Junior.Member AIME, .is a post-doctoral ·
fellow, Department· of Mineral Technology, College of Engineering,
•. and Inorganic Materials Research Division, .Lawrence Rad~ation
Laboratory, University of California, Berkeley, California .. ·
·_... ·: .. .'~ .. . .'\'. ~ . . .'' ;, ,., ', ' ' . ' :. ·: ~--. ', ~ ' . .. ~ . ' . : :.... ·.·.·, .·• ... . I '·.· ,,.- : ·.·- . . ·.,. ·- ·. :, .. '• ·.'· .• .. ·.•. '· .. ;. ' ' . .-2-
Introduction
• Reliable thermodynamic data for the carbides and oxides .of
molybdenum and· tungsten have recently become available.· Using these·.· , ·
' data and earlier data for the analogous chromium compounds, the stable
• I phases in the Group VI metal-carbon-oxygen systems at specific temper-
atures and pressures can be. determined. ; .'·
To provide a complete picture of the thermodynamically stable .
regions in the metal-carbon-oxygen s;y:stems of vanadium, columbium 1 and tantalum, Worrell and Chipman have described and constructed '' .. ,.
Pourbaix•Ellingham diagrams in which the two co-ordinates are oxygen'·
· • potential (-RTlnP ) and temperature. In a Pourbai~-Ellingham diagram 02 for a three-component system, the phase rule requires that at equilib-
·· rium two condensed phases define an area, three condensed phases
determine a line, and four condensed phases specify a point.
To obtain a well-defined area at high oxygen potentials and tem- :_ · ·- peratures, the initial carbon to oxygen mole ratio is specified to be more .. ·
. than sufficient to reduce the oxide but not enough to convert all the metal ·
to carbide. Thus, the lowest regions in the subsequent Pourbaix-Ellingham
diagrams represent areas in which the metal and its· carbide are the stable
condensed phases.
,,..- ·'.! ·-.-~. ·,
.,·- · . ! .. ·:·- .. / . ~ . . . ' ..... ····' . -: ..
'"' '· ... ;· .. ·, -:
'.'•. . ·: ... ' . '\ : '" ~ :' '._;:-- ., .·-·.· ·, .. ' .. . . .~ ; ·.· ·-·. ·:,'; .. ,_ ·.,:, .:_ ~ .. .'r • ·.•'. ,. -3-
Cr -c -0 System .
A. Thermodynamic Data. To simplify the subsequent calcu-_ · ,· .
lations, all thermodynamic data _are presente4 in the form of linear_:
Gibbs-energy-of-formation* equations which are .reasonably. accurate . I \ ..
* In accord with the decision of the Commission on Physico-Chemical .·. ·
·Symbols and Terminology of the IUPAC. the term Gibbs energy of
formation is adopted to represent the free energy of formation at ... constant temperature and pressure.·
· over the entire temperature ranges of the diagrams.
The. thermodynamic data for the compounds occurring in· the
Cr-C -0 system are s:ummarized in Table I. The only chromium oxide
sufficiently stable to exist in the'Cr-C-0 system is Cr . T~ermo- ": ( 2o3 · dynamic data for this oxide and for CO and CO were taken from the · ',, ' 2 2 compilation.of Coughlin. .. The Gibbs-energy-of-formation equations 3 . for the chromium. carbide phases are those of Richards<;m wl;lo has ·.··:: 4 critically .evaluated the original. work of Kelley and co,-workers. . 5 Several volatile chromium· oxides have been reported, but their ; .. · .··, .·, · influence is negligible in Cr-C -0 system . ·.: .<· ~ ..
. .·, .. :: ·::.. ,:
... · .. -~. .; ...
' ...... ~ ' '. ·' ;, , '·
;:' .. ' ·.~: ·.. : .. '. '· ·:-· .\..' .. :_·.;-' ~ .. -~_, .... ,, .... ··'' ...... :_ ...... ~ .... :.~ ..... ~ ..... ~--~ ...... ~·····"·-..._...... ,_ __ .., ... --~-·~·····<..·-·-"•'''-. -4;..
. i
B •. Phase Relationships. ·The condensed phases of the Cr-C-0 r 1.t .•. . system in equilibrium with vapor at one atmosphere 'pressure are shown
in Figure 1. No t.ernary oxycarbide phases are shown because the . ·~,. existence of such compounds is unknown to the author. The temperat11re ·
/ . ,/ a:t which any two condensed phases become, . unstable is indicated along
the two-phase eq11ilibrium lines in the diagram. In this ternary systein,
the equilibrium vapor at the indicate.d reaction temperatures is entirely
·. CO. It should be noted that Cr c ~d Creutectically melt in the . 23 6 -'. 6 vicinity. of 1500° C; thus, . the two upper equilibrium lines in Figure 1 · are dotted, since the 'indicated temperatures have been calculated hypo-. ·.
thetically using the data for solid Cr c . 23 6 C. Pourbaix-Ellingham Diagram. In the Cr-C-0 system, ·.
. Cr 0 and C are the stable condensed phases at low temperatures and ... · 2 3 high oxygen pressures (low values of -RTlnP ). As the temperature 0. 2 . : . or oxygen potential increases, a phase region appears in which Cr c 3 2 Cr 0 are the stable condensed phases.. The three condensed phase ·• ... · ~d 2 3
- '-':.·
·. -RTlnPO '· = .·. 1 72, 000.-. 42:. 5 T . (1) . ··.:· . . . . . 2 ·.·
Equation 1 represents the top line shown in Figure 2, .. which is the .:_':,; . ,.·. : ',\ Pourbaix-Ellingham diagr~m for: the Cr-C-0 system. By a similar
·...... • method, the other equilibrium lines in Figure 2 were det~rmin~d. · · .. ' ..• '.1.
• ·.-.:. "1," -5-
The vertical line represents the separat1on of liquid and solid Cr c ; 23 6 r the equilibrium lines above this temperature are dotted because they
are estimated.
The dashed lines in Figure 2 represent values of -RTlnP . 0 2 2 6 for CO equilibrium pressures of ·1, 10- , and 10- atmosphere. /'
At elevated temperatures the CO pressure is equivalent to the total
equilibrium vapor pressure because the pressure of C0 and other .. 2 .. ..., :-·volatile. species is negligible.
Mo -C -0 System
A. Thermodynamic Data.· Gibbs-energy-of·~:formation equations
• I for the compounds occurring in the Mo-c .. o· system are given in Table II.
The Mo0 (g} equation is based oh the investigation of Burns and co- 3 7 , workers, while the M~0 3 (s} data is from the compilation of Kirig and 8 co-workers. The Mo0 equation was obtained from the equilibrium· 2 9 study of Glei.ser and Chip-man, who discuss and correlate the earlier· 10 1 data. A recent study by Rapp is, in good agr~ement with the Fesults ·' . ..
of Gleiser and Chipm~. The Mo . C ~quation is based also on the .. 2 21 9 resuits of Gleiser and Chipman. Althoug~ this equation applies only
to the metal-rich side of the Mo C phase (designated as' Mo : C), it 2 2 21 was also used in calculations involving carbon saturated Mo C. The 2 Mo c equation is an estimate based on the Mo c data and the eutectoid 3 2 2 decomposition of Mo c into Mo C and C, which is reported to occur 3 2 2 'I, • 11 at 1450°C. It should be noted that the phase previously reported as·· .... 12 MoC is actually Mo c . ,_· 3 2 ::'·,·· ···.: .. '··
·, '...... , ., .· . "< ~-:< ,·' .,·;,_ . ' -6-
B. Phase Relationships.. The solid _equilibrium phases of the
'W ,. Mo-C-0 system at 1 atm pressure are shown in Figure 3. The temper-
atureamthe C0 /CO gas ratio at which ~y two phases become unstable 2 are indicated along the two-phase equilibrium lines. The stability o:( __ ·
/ Mo0 and Mo c is such that they do not exist as equilibrium phases 3 3 2 at 1 atm pressure in the Mo-C-0 system.
It also should be noted that no ternary oxycarbide compounds .·, .:
13 14 are known to exist. However~ Kihlborg. ~ has reported several" binary oxides existing betw-een Mo0 and Mo0 . These oxides are 2 3
stable only over limited tem~erature· ranges and ~ot above 800° C. No ·'·
quantitative thermodynamic data are available for these oxides1 but
neglecting them does not affect the calculations and conclusions in this ' . paper. However~ Figure 3 would be_ altered somewhat with the inclusion·
. of these intermediate oxide phases.
·'-·-·· C. Pourbaix-Ellingham Diagram. Figure 4 in the Pourbaix- I
' Ellingham diagram for the Mo-C-0 system. The equations in Table II
were used to calculate the solid-phase equilibrium lines. Vapor ' ' 2 equilibrium lines 1 and 10- atm pressure are shown as dashed lines ·_.. of , . in Figure 4 .. The temperature atwhich the 1 atm line crosses each
solid-phase equilibrium line is indicated in Figure 3. _
Another dashed line representing the oxygen potential in equi- .
with Mo0 _(g) at 1_0 atm. is shown in Figure 4. The position , libri~m 3 -s of this line relative to the vapor equilibrium lines demonstrates that '' .. ·.·
' '~ . ,' '. -'1-
the pressure of Mo0 (g) is negligible compared to that of CO and c9 . 2 3 - '· Indeed# one shouldn't expect any significant amount·of gaseous oxide
under such reducing conditions.
W -c -0 System
A. Thermodynamic Data. Thermodynamic data for the compounds/
occurring in the W -C -0 system are given in Table III. Ackermann and. 15 Rauh have studied recently t~e W-0 system at high temperatures#
and the equation for W o (g) is,from their results. Data for the solid 3 9 oXides were obtained from the equilibrium· study of St. Pierre and ; 16 co-workers and are in good igreement ~ith i!he ca{orimetric investi- ·. gation of King and co-workers. !3
The Gibbs-energy-of-formation eq_uations for WC and W C are 2 17 those previously calculated by Worrell'. The WC equation was· obtained 18 by combining Mah1s heat-of-fo;mation value with the results of the 19 equilibrium stuqy of Gleiser and Chipman. The W c equation is 2 bas~d 18 on Mah's heat;.,of-formation value and an estimat~d entropy ..of forma 20 tion~ The w c and WC_ data predict 1327o.:c: for the eutectoid decom- .. 2 . . \ position of w2c ~tow and wc,:which is iri good agreement with the
1 .• reported value of 1300° G.~ · :. B. Phase Rel:ationships. The solid equilibrium phases of the
•v W-C-0 system at l atm. pressure are shown in Figure 5# in which the
reaction equilibrium temperatures and C0 /CO gas ratios are indicated~ · .• 2 along the two-phase equilibrium lines. . _The 'W_ C carbide is stable only_ .·.. · 2 above 130ooc··: and thus is not shown.
'·· . ~. ·;·: :.· .: ' -8-
It also should be noted that the equations presented in Table III predict
that wo2. 72 decomposes into. wo2. 90 and wo2 below ,620°C, and that
wo2. 90 decomposes into wo3 and wo2 below 580°C.
22 A fifth oxide of composition W 0 has been reported, its 3 ~ut occurrence is probably the result of minor traces of a third element. 23 Kihlborg was unable to prepare the analogous Cr 0 and Mo 0 phases, 3 3 24 25 which had been previously reported by Schonberg. • However, the
·---·existence of W 0 would alter only slightly the thermodynamic analysis 3 ·of the W -C-0 system.
No ternary oxycarbid~ compounds are known,to exist in the \ W -C -0 system.
C . Pourb aix-Ellingham Diagram. The the rmodyriamic data
in Table III were used to determine .the solid-phase equilibrium.. lines
shown in Figure 6, which is the Pourba:ix -Ellingham diagram for the 2 W-C-0 system. Vapor equilibrium lines for 1 and 10- atm. pressure
,..:·, : .: are super-imposed on Figure 6. The temperature at which the 1 atm '..
line crosses a solid-phase line is indicated in Figure 5. Another
dashed line representing the oxygen potential in equilibrium with 6 W o (g) at 10- atm. is shown also in Figilre 6. The W-C-6 system ... 3 9 is thus similar to the Mo-C-0 system in that the equilibrium vap<;>r is
composed entirely of CO and C0 , and the amount of gaseous oxide is 2 negligible.
.. ·.~'. . . ' '' • •'• -~·, ,;,,,.,.<•~••·•••••••--•-•~..1·•·'"~'•"~·..!•-•••~" ,,,,,,._,,., ,,,,;,,\,~-k"• ---~·-•· •·~ koo •·'•"'' ·••-•-·•--'""'''••d,.o\.t-•. •,.·•· -9-
·-~
Applications of the Pourbaix-Ellingham· Diagrams
Besides presenting an ·over-all picture of the thermodynamically
stable regions in the }'4-C-0 ternary system# Figures 2# 4, and 6 are
useful in estimating the minimum temperature necessary to obtain a __ _ / metal (saturated with carbon and oxygen) or a given carbide by carbo-
thermic reduction at a specified pressure. The minimum temperature
necessary to obtain chromium under a particular reduction pressure
is the temperature at which that CO pressure line crosses the . .
' for specified reduction pressures' are tabulated in Table IV.
In the Mo-C-0 and W-C-0 systems, the equilibrium vapor
_consists of varying amounts of CO and C0 ; and one has to calc~late 2 first the equilibrium vapor composition for a specified total pressure.
The minimum temperatures necessary to obtain molybdenum and tungsten
for specified reduction pressures have been calculated and are presented:_
~ in Table IV. In the Mo-C-0 system~ the vapor in equilibrium with
Mo C, Mo0 and from 70 CO at 1 atm. total pressure· 2 2 Movarie~ perc~nt . -6 to 77 percent CO at 10 atm. In the W-C-0 system, the vapor in . , . equilibrium with we, wo2 and w varies from 62 percent co at 1 atm. 6 ·pressure to 50 percent CO at 10- atm.
The minimum terri.·peratures necessary to form the WC and Mo C · I . 2 carbide and the C0 /CO equilibrium ratios at reduction pressures of 1 2 -2 . and 10 ·atm. are tabulated in Table V. .. ~ .. -· ,...... ::..:.:..: ...... :...... : .. _~-·-·····--··· ~- ?,~ .:; (~_.,_ .. ~ .. ::...... ·.! .) ~ .. ·~., .• .:.. .•• ____ ~ •. .1 ... :: .... l...... !.).:...~:~:.:.J;: ..J..:..'._,~--.~-_._.~--~--··--; : ...... :-..~___ . ').:· ... :-·· ..... ·- --·-~·:•. ~. -~---~-· ·-~- :-.. ..· •...... •. •------~ -~---··- __ _..-;;;..--~·· .-10-
2 In Figures 4 and 6 •. the .1 and 1 0- .atm vapor equilibrium lines
r are shown to illustrate the carbothermic reduction paths at these· pres- • sures. Along these lines, the composition of ~e equilibrium vapor
changes from 100 percent C0 at very. low temperatures to 30-40 2 " percent C0 at the metal-carbide boundary. 2 It should be emphasized that the above analyses of the carbother-
mic reduction paths are dependent on equilibrium conditions being
maintained. However. kinetic factors' may be encountered which will . inhibit the approach to equilibrium states, particularly at low temper--
atures.
Acknowledgments
The author wishes to express his appreciation to Professors
Ralph Hultgren and Leo Brewer for their support ~d encouragement
and to Raymond Qrr for his interest and helpful suggestions. This work·
·was done under the auspices of the U. S. Atomic Energy Commission.
References
1. W. L. Worrell and J. Chipman. ~r ans. AIME 23 0, {1964):
. 2. J. P. Coughlin, U. S. Bur. Mines Bull. 542 {1954).'
3. F. D. Richardson, J. Iron and Steel Inst. 175, 33 {1953).
4. K. K. Kelley, F.. S ..; Boericke,. G. E. Moore, E. H ..Huffman; i andW. M. Bangert, U.S. Bur. Mines T. P. 662 (1944). . ·c,.·_
5 .. R. T. Grimley, R. B. Burns, and M. G. Inghram, J. Chern. Phys.
34, 664 (1961). i : '
. '' -ii-
6. E. K. Storms, Los Alamos Scientific ~Lab Report LAMS-2674 (1962).
") 7. R. P. Burns, G. DeMaria, J. Drowart, and R. T. Grimley, .J. Chem.
Phys., 32, 1363··(1960).
8. E. G. King, W. W. Weller, and A.· ·u. Christensen, U. S. Bur.
Mines R. Pc,;· .I.. , 5664 ( 1960).
9. M. Gleiser and J. Chipman, ·J. Phys. Chem., 66, 1539 (1962}.
10. R. A. Rapp, Trans. AIME, 227, 371 {1963).
11. T. C. Wallace, C. P. Guitierrez, and P. L. Stone, J. Phys. Chem., I 2.:!_. 796 (1963).
12~~- E. Rudy, F. B_enesovsky, and K .. Sedlatschek, Monatshefte, 92,
941 (1961}.
13. L. Kihlborg, Acta. Chem. Scand., ~. 954 (1959) .. · ·
14. L. Kihlborg, Arkiv. Kemi.. 3_!_ (44} 471 (1964).
' 15. R. J. Ackermann and E. G. Rauh, J. Phys. Chem., 2.:!_. 2596 (1963).
16. G. R. St. Pierre, W. T. · Ebihara, M. J .. Pool, and R. Speiser,
Trans. AIME, 224, 259 (1962).
17. W. L. Worrel~. Trans. AIME, 230, :.~Y.<:(1964).·
18. A. D. Mah, u~ S~ Bur. Mines RI 6337 (1963).
19. M. Gleiser and J. Chipman.· Trans. AIME, 224, 1278 (1962).
20. W. L. Worrell, J ~ Phys. Chem .• 68, . 954 (1964).
""'.! 21. G. W. Orton, Tr·ans~. AIME, 230, 600 (1964). !I -· 2 2. G. Hagg and N. Sch'6nberg, Acta. Cryst.• :!_. 351 (1954) ..
23. L. Kihlborg. Acta. Chem. Scand. ~. 2458 (1962).
24. N. Schonberg, ·Acta. Chem. Scand. _!l. 221 ( 1954). ) . : i 25. N. Sch'6nberg, Acta. Chem .. Scand • .£?.., 617 (1954). .. , .... ~··· .• ~. ••.•••••• '.,~. --· "'" .t '·~ " .•.• l , __ . .. -. .: ·-~~ ·, : ... : .... ·--·~- ...... ~· "."" ...
-12-
,. :TABLE I. Thermodynamic Data. for the -stable Compounds Occurring in the Cr-C-0 System.
Compound Standard Free Energy of Formation, cal/mole I / co (g) -26, 760- 21.0 T
C0 (g) -94, 260 - 0. 3 T 2
Cr 0 {s) -~.2'7.1;· ~00,,+ ~61 ,-. f3: TJ. 2 3 . cr c {s) -98, 300 - 9. 2 T 23 6 Cr C {s) -:-41, 700- 6. 2 T 7 3 1 ..__------~~--~----'------~''·:·. Cr3c 2 s -20,200 -.2. 8 T -
TABLE II. Thermodynamic Data for the Stable Compounds
Occurring in the Mo-C-0 System.
Compound Standard Free Energy of Formation. calf mole
Mo0 {g) ' -85, 050 + 13. 9 T 3
Mo0 {s) -176;!000 + 58. 0 T > 3 Mo0 {s) -137,900 + 40.2 T 2
.. ! Mo . C{s} -12, 000 - 1. 5 T 'i 2 21 ) . ·. . Mo c (s) -14, 600 - 3. 0 T " 3 2 . . .. ! ...... I :··
• I , .• -~-..:~:..', .. :. :·~.,_..: __ : -~ .:~ ...... ~ ...... ·-.:~ • .:.-~ ...... \·.'.'. .:..~ •• ::...... !.. ,.;;~-~.:;; • .:.·.-.. ) .. .1. .. :, • ... ' •••~ •'··-"'· ·... '·.• .:...-t .•• ~~, •• :.:!..:..~:i:.(t'l..~.:.~ ..... _...... :_;r....• _:.... -. .•.• ....:,·~·•. ...!:.' • ...:-··.-:. ···~--~-.. -•. ~-J .. ..:~: .... ~ .. -·:..,.,.;,:,.:.-...,~- . ..-__.______•______....
, ' r. TABLE III. Thermodynamic Data for the Stable Compounds r· Occurring in the W-C-0 System.
Compound Standard Free Energy of Formation~ cal/ mole: I I W309 (g) -474, 100 +.110. 3 T
wo {s) -197, 540 + 58. 0 T 3
wo2. 90(s) -189, 950 + 54~ 7 T .. , - wo2. 72(s) -i76, 500 + 49. 0 T ..
wo (s) .. I' -131 ~ ·7 0 0 + 3 6 .. 8 T 2 \ ·- .. we (s) -9. 600 + 1.· 0 'l'
w c {s) -6,400-1.0 T 2 - \
TABLE IV. Minimum Temperatures Necessary to Obtain .
Chromium~- Molybdenum, and Tungsten by
Carbothermic Reduction ..
l Reduction Pressure, atm Temperature~ oc , I· Cr Mo w 1 -- 1070 900 2 10- 1360 825 685 . .._\ .., .. I 4 ' 10- 1110 655 .. 540 ' 10-6 •· ' 915 535 430 I . -· -14-
J '
,(. TABLE V,. Minimum Temperatures Necessary to form r
WC o.nd Mo C by Carbothermic Reduction. 2
~. --- Reduction Pressure, atm ,, we Mo2C '. Temp.~,.C PcofPco Temp. °C Pco 1Pco 2 2
,_ 1' 535 8.52 630 1. 94 10-2 380 . 19.0 465' 2.23 -
( l
"''·/
·' '
.;_;.
;- .. ,.
'1 ' •. • ·, :.· • .. ' '•
' :·
. \ I '
•' ' ' J ·'·
\)
/ Cr
. ' ...... ~ ,,. -. ' ...... Figure 1•. Condensed Equilibrium Phases of the Cr-C-0 System ~· :at 1 atm vapor pressure. (The temperature (° C) ·at which any two phases become unstable is , . · ··. indicated along the two-phase line~) . ·... .. -~ --~;~; ~------·----- ··--·~ ... ·----- ... ---.;
._·,·
• 1", ,I . , . ,., ,j·,. ' • •• .: • ·,.:-; < ~-. __ 1, r·
\,}'
I
\ . \ \ \ \ \ \ \ \ \ \ 120 - 0 (,) .::1! Liquid, - Cr N 140 0 a_ c c:>\ 1- 0:: . I
0 2000 Temperature (° K) -· -·- ...... ---·----:---·· -.
· Figu~e 2 •. Pourbaix-Ellingham Diagram for the Cr-c-o· System.
______.. ______··-····-·--···-!
.\
· .. :·-· _..-:_!_· •,, .· . ~.. . : ·.. !-.-- .. , .· .. · . r ... .j .· . . \" .· ·_;,_, ·' ,· .· ·, -:-,: ::.,·;-•.. ·' ..... ': ·'
'• ·,·_, ·. ·_-·_ ';_'· ' ~ . ·':• ·,·. .',. '· . "·,··. ·. :. " , . ,..
<._I
Mo I
c 0
Figure 3. Solid equilibrium Phases of the Mo-C-0 System at 1 atm: · · vapor pressure. (The temperature (°C) and the C0 /CO ... · gas ratio (R) at which any two phases become .. 2 . · ... t..) unstable are indicated along the two-phase line.)·
. ··-----· ~- ~ ...... ·····-- ...... : ... ______~---·········--- .. ------~-----·---~·-·- ..
. ·· ...... :· ; ' . . ,' . f .~ ' ...· :; . . ~. \, ...... · ;.·. ; ··~ :, ! . . . . ';. ·: ·' .. · .. •• •.• ·1·. ·,' ·•· .• ;:· ·:.·. '1,,._ .. ·":,. •' · ~- . '...... :. ' .·.·.·._,;, .··,. • j • • • .} ·.. ·' ~ ·. ·.· ' . ·.;. ;_ . ; .. J
/
- 0 0 . Mo02 , C j(! I \
N 1 atm ' a? ' ' c: ' c\ ' ' 1- . \ .cr: I
Mo, Mo 2 C
0 400 800 2000 Temperature ( 0 .1()
. Figure 4. ·. Pourbaix~Ellinghatri Diagram for·the Mo-C-0 System. ·
'· .... ~.:.. ---·~ .:~>·! ,': __ . ', -.. ·····-·;..:::.:.: ...... i 1 •',.J
...
···., ' ' .·.:_' ·-.· . _.:·i .. ·... ·.. ·· .•. -~ .~·.' ···.' · .. : ., ,:·1' ,.. ' . ·. ·:.·: ., . , ... .·.:· . ...
i'· ~' '
.• .! ' • I
\.!
w i ' f·
t '
i: f i f' ... l f ' ! .,
i· \ 1 J
~ :...... i-1I .,,i;.'·' i.'
'·<" '· f" I !
c
Figure 5 Solid Equilibrium Phases of the W-C-0 System at 1 atm · · .; vapor pressure. (The temperature (° C) and the C0 /CO · 2 .gas ratio (R). at which any two phases become . uri stable are indicated along the two-phase line. ) ·
'!
. \
:: . . -· ,··
. :-·· . . . :;. ; .
....I,
/
-6 10 atm
0 (,) -..:.: N '\ rE c ' "\ ....ct 0:: ' WC,W . I, I '
0 800 1200 1600 2000 Temperature· (°K) .. ·- .... '£··-·--·- ... --·-· Figure 6. ·Pourbaix-Ellingham Diagram for the W-C-0 System ...·
~- ·~-~--; . ~-····.:.-.~-- '
·.1 ·. . . • ....
' -~- . ;···
··. . ·. .'' . . . ' .·: .. i. ·.,. ; .~ ; . ,. '> . .. ·.· . .··,; .· ,· . ·, ·.· . .._ . ' ·' ·... .:.·.--- ··.-· . . . ' . . . ~ ; ··:· . .. . : . '. . ,•.-: .. •.·· .. -.,. t,.' . ·. ' ;' :: . This report was prepared as an account of Government sponsored work. Neither the United States, nor the Com mission, nor any person acting on behalf of the Commission:
A. Makes any warranty or representation, expressed or implied, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, appa ratus, method, or process disclosed in this report may not infringe privately owned rights; or
B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of any infor mation, apparatus, method, or process disclosed in this report.
As used in the above, "person acting on behalf of the Commission" includes any employee or contractor of the Com mission, or employee of such contractor, to the extent that such employee or contractor of the Commission, or employee of such contractor prepares, disseminates, or provides access to, any information pursuant to his employment or contract with the Commission, or his employment with such contractor.