High temperature cobalt-base alloy resistant to corrosion by liquid metals and to sublimation in vacuum environmen

Ashbrook, R. L.

Freche, J. C.

Sandrock, G. D.

English

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REPLY TO 
ATTN OF: GP 
FROM: 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON. D.C. 20546 
October 15, 1970 
~ ~ ~ / ~ c i e n t i f i c  & Technical Information Division 
Attention: Miss Winnie M. Morgan 
~ ~ / ~ f f i c e  of Assistant General 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U.S. Patents in STAR 
In accordance with the procedures contained in the code GP 
to Code US1 memorandum on this subject, dated June 8, 1970, 
the attached NASA-owned U.S. patent is being forwarded for 
abstracting and announcement in NASA STAR. 
The following information is provided: 
U.S. Patent No. 
Corporate Source 
Supplementary 
Corporate Source 
Lewis Research Center 
NASA Patent Case No.: XLE-02991 
Gayle Parker 
Enclosure : 
Copy of Patent 
- 
7 
. 3 (NASA CR OR TMX OR AD NUMBER) 
I 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710006550 2020-03-17T02:40:31+00:00Z
united States Patent 06 ce patented act. 3,2X6,865 4, 19683 
1 2 
metal matrix can greatly affect this process. It  would 
3,276,865 be expected that a reduction in the percent of high vapor 
HIGH TEMPERATURE COBALT-BASE ALLOY pressure alloying elements in the alloys used would John C. Freche, Pairview Park, Richard L. Ashbrook, lessen this problem, Cleveland, and Gary D. Sandrock, Faifview Park, Ohio, 5 From a corrosion resistance standpoint, cobalt resists assignors to the United States of America as represented 
by the Administrator of the NaCioual and corrosion by mercury more than nickel but less than iron. 
Space Adminislration It appears that cobalt is at least equivalent to nickel 
N o  Drawing. Filed June 15, 1964, Ser. No. 375,401 in corrosion resistance in alkali metals up to the limit of 
4 Cialms. (CI. 75-170) its useful temperature range. Certain stainless steels, 
10 although acceptable up to 1600' F. in contact with the 
The invention described herein may be manufactured alkali metals, show a low compatibility with mercury 
and used by or for the Government of the United States if they have a high nickel and/or a high chromium content. 
of America for governmental purposes without the pay- Nickel-base alloys are not compatible with mercury, but 
ment of any royalties thereon or therefor. may be used with the alkali metals up to approximately 
The present invention relates to an improved cobalt- 15 1700" F. Refractory columbium alloys, although having 
base alloy having high strength at elevated temperatures excellent elevated temperature strength characteristics and 
up to 2200" F. The invention is further concerned with cor-osion resistance to both mercury and the alkali metals, 
a cobalt-base alloy that is resistant both to corrosion are very subject to oxidation. This makes pilot or ground 
by liquid metals and to sublimation in a vacuum environ- tests of prototype units using this material extremely diffi- 
ment. 20 cult and expensive. 
Various components of turboelectric space power sys- It is, therefore, an object of the present invention to 
terns, especially the ducting for the liquid metal heat provide an improved cobalt-base alloy having high strength 
transfer media, present difficult material problems because at temperatures up to 2200" F. 
they are subjected to the dual environment of liquid metals Another object of the invention is to provide an im- 
on one surface and a high vacuum on the other. Aho, 25 proved cobalt-base alloy which is resistant both to cor- 
materials for these components must be workable and rosion by liquid metals and to sublimation in a vacuum 
weldable to  permit forming into sheet or tubing for environment. 
ducting applications. Commercially available materials A further object of the invention is to provide an 
considered for such applications are certain stainless improved cobalt-base alloy which is workable and weld- 
steels as well as wrought nickel- and cobalt-base alloys. 30 able to permit forming into sheet or tubing for ducting 
Refractory metal alloys of colu~nbium have been con- applications. 
sidered for temperatures of 2000" F. and above. These and other advantages of the invention will be 
Turbine engine parts and other engineering structures apparent from the !.pecification which follows. 
which operate in air at high temperatures must have The present invention is embodied in alloys having 
adequate oxidation resistance or be capable of operating 35 the following composition range wherein the percentages 
satisfactorily with protective coatings. Both cobalt- and are by weight: 
nickel-base alloys have been proposed for such structures. 
~ a c h  of the classes of commercially available material Cobalt ------------- From a b o ~ t  36% to about 89.4%. 
considered for turboelectric Space power systems has Tungsten ----------. From about 10% to about 45%. 
certain limitations. For example, stainless steels are 40 Titanium ----------, F~~~ about .s% to about 2%. 
restricted to  applications where the temperature does carbon ------------ F~~~ about -1 % to about 1 %. 
not exceed approximately 1400" F. if long life in the Zirconium ---------- From a h u t O %  to about 3%. 
neighborhood of 10,000 hours is to be obtained, even at chromium ---------. prom ahut 0% to abut 10%. 
the relatively low stress levels, such as 5,000 p.s.i., which 4j Rhenium -,--------- F~~~ about 0% to about 3%. 
are likelv to be encountered in ducting a~~licat ions.  
~ r o u ~ h t ~ c o m m e r c i a l  cobalt- and nickel-6ase-alloys are 
limited to applications where the temperatures do not 
exceed approximately 1600" and 1700" F., respectively, 
at similar stress levels. 
The vapor pressures of various metals differ, and this 
imposes another limitation on the use of certain com- 
mercially available materials. As a result of these dif- 
ferences in vapor pressures some metals tend to evaporate 
more than others in a high vacuum. Chromium and 
aluminum are paflicuiarly susceptible to evaporation 
losses, Vifiitally all stainless steels as well as cobalt- 
and nickel-base alloys contain appreciable quantities of 
chromium, and most nickel-base superalloys contain 
aluminum, as well. Therefore, evaporation of chromium 
and aluminum may occur during long time exposure of 
these alloys to a high vacuum environment, and the 
structural integrity of these alloys may be affected. The 
manner in which the alloying element is tied up in the 
The above alloy composition represents an improve- 
ment over the alloy disclosed in copending United States 
patent application Serial No. 355,126, filed March 26, 
50 1964. The present alloys include chromium and rhenium 
in addition to the alloying constituents disclosed in the 
copending application, 
Chromium is included because it is one of the most 
eEective eternents for strenghening the binary alloy 
e5 Co-25W. Z r e  presence of chromium in relatively small 
a n ~ o u n b  in alioys is not as detrimental, insofar as evapora- 
tion loss is concerned, as the relatively large amounts in 
the range of 20% to 25% present in conventional cobait- 
base alloys. If present in small quantities, the concentra- 
tion of chromium at the surface is less, as would be any 
concentration gradient that occurred in servicc, and con- 
sequently the driving force for diffusion of chromium to 
the surface would be less. A preferred alloy having 
3,276,866 
3 
chromium added Lo the ailsy dkclosed in the mpndirag 
4 
TABLE 111 
application has the followiarg com~sitionr: 
Percent 
Cobalt ---,--,------------------------- About 69.6 Alloy / T c ~ ; ? .  I %$ 
T u ~ ~ t e n  .............................. About 25 a; 
~ O Y  
Co-25W-1Ti-1Zr-0.4C -------------.---- 
Co-25W-lTi-lZr-3Cr4.4C .------------ 
iirror~glh, 
p.5.i. 
--
98,580 
90,425 
63,000 
37,400 
24,000 
21,800 
20,800 
9s 050 
73: 500 
m.. 
~icaniurn -------,---------------------- About 1 
Zirconium ............................. About 1 
Co-25W-1Ti-1Zr-0.4C (As Cast) ....-._..-....---. Chromium ............................. About 3 C0-25W-lTi-lZr-3Cr-O.4C(As Cnst)....-----.--.. 
Cabon --- - - - - - - - - - - - - - - - - - - - - - - . . - -  About .4 C0-25W-lTi-lZr-3Cr-0.4C (AS Cast)_ _ ___-___-___ 
Co-25W-1Ti-1Zr-3Cr-0.4C (As Cnst)-_ -.--_.....- A comparison of as-cast strw-rupmre propefties of the 10 C D - ~ ~ W - ~ T ~ - ~ Z I - ~ C ~ - O . ~ C  (AS C%t)-- . ...---.--- 
Co-25\fr-l'ri-1Zr-3Cr-0.46 (As Cnst) -----....---- 
~pesent alloy with those of a preferred alloy disclosed Co-25W-lTi-lZr-3Cr-0.4C (AS cast)  ... -.--..--..- 
in the copending application is &own in Table 1 wherein Co-ZW-"i-l"r3Cr-2Rca.4(: (AS Cast).--.----- Co-25W-lTi-lZ1-3Cr-2Ra-0.4C (As Cast) ..--.---. 
SHEET ALLOY8 
the samples are uncoated and nominal cumpositions are ~o-25~-1Ti-l~r-3Cr-2~e0.4~ (AS 
listed. Co-25W-lTi-lZr-3Cr-2Re4.4C (As15 C0-25W-lTi-lZ1-3Cr-2Re-O.4C (As 
Co-26W-lT1-1Zr-3Cr-2R~0.4C (AS 
TABLE I Co-%W-1Ti-1Zr-3Cr-2ReO.4C (As 
Room 
~ o o l n  
1,645 
1,800 
2,000 
2,045 
2, loo 
Room 
1,600 
Streg, 
p.s.1. 
16,000 
16,000 
20 Co-25W-1Ti-121-0.4C (As rolled) -. -..-.----.-.-- 
Co-25W-lTi-lZr3Cr-0.4C (As rolled)-.. _---.--..- 
Co-25\V-lTi-lZr-3Cr-O 4C (Annealed) --..-------- 
~ o - 2 5 ~ - 1 ~ i - l Z r - 3 ~ 1 - 0 : 4 ~  (Annealed) --.._....  
Co-25W-lTi-lZc-3Cr-O.4C (Almealed) --...-.----- 
Co-25W-lTi-lZr-3Cr-2Re4.4C (As rolled)..-..--.. 
Co-25W-lTi-lZr-3Cr-2Re-0.4C (Annealed)-.-.--- 
25 C0-25~V-lTi-lZr-3Cr-2Re-0.4C (Annealed)-.-.--- 
Co-25W-lTi-lZr-3Cr-2Rs0.4C (Annealed) ----..- 
Temp., 
O F. 
.---- 
1,850 
1,850 
Room 
Room 
Room 
1,600 
1 800 
~ h o m  
Room 
1,600 
1,800 
Avernge 
Rupture 
Life lu 
Air, hrs. 
82 
131 
179,330 
221,330 
173,750 
71, It0 
37,100 
211,150 
181,750 
77,650 
37,200 
Rhenium is added to the above alloy because it is a 
potential solid~olution strengthener and stable carbide The cobalt-base alloys of the present invention can be 
former. The evaporative loss rate of  rhenium is extremely prepared either by vacuum induction melting or by in- 
low, and another preferred alloy having rhenium zidded to 30 duction melting under an inert gas blanket. In inert gas 
the above ~refefled alloy has the following nominal corn- melting the bottom of a cold zirconia crucible is covered 
position: with a small quantity of electrolytic cobalt. Carbon in 
l'ercent the form of lamp black compacts is placed in the crucible 
Cobalt -----,,------------------------ About 67.6 and covered with briquetted titanium, and the whole is 
Tungsten ............................. About 25 35 covered with electrolytic cobalt nearly filling the crucible. 
Titanium ............................. About I A cylindrical shield is placed around the top of the cruci- 
............................ About 1 ble, and a flow of argon is directed at the top of tile 
Chromium .......................... About 3 charge. 
Rhenium ............................. About2 Once the charge begins to settle, the remaining cobalt is Carbon .............................. About .4 40 added. When this portion of the charge is completely 
melted, tungsten is added in the form of short length 
Uncoated having One the preferred lIomina1 rods, The melt is then superheated to 30500 and held 
Co-Zm-1Ti-1Zr-3Cr-2Re-0'4C* were sVwm lor three minutes to insure dissolving of the tungsten. The 
rupture tested in air at various conditions. The resulting melt is then allowed to cool to 29000 F. and poured. Dur- data are Tab'e 'I The l 5 f W  45 ing pouring the inert gas coverage is removed. Melts are ps.i.2 1850' data are directly comparable lo the data poured into investment molds heated to 16000 F. and per- 
of ' and show f~~~~~ ' stress mitted to cool to room temperature natur;,lly without life over the alloys listed therein. Also shown are data speeding up the process artificially. for several of the skongaf known ~ ~ e r c i a ~ ~  available 
~ 1 1 0 ~ s  of this series have also been by the cobalt-base alloys. 60 more complex technique of vacuum melting in order that 
the effectiveness as alloying constituents of such elements 
TABLE 1l as titanium and zirconium should not be reduced by their 
reaction with atmospheric gases. This melting technique 
:;;ze can result in further improvement in the properties. Im- 
 ire in 55 proved cleanliness of the resulting vacuum melt can also 
Airl hn .  result in better strength as well as  improved ductility. 
Thus, by introducing a higher degree of complexity in the 
I casting process, improved alloys can be obtained. Ex- 
1,007 amples of rupture data from vacuum melts for two d o y s  
60 are shown in Table IV. 
Alloy 
3Cr-2Re ..-..--....------------------- 
3Cr-2Re ..-_.-_..--------------------+ 
~ C P - Z R ~  ...-..-.--_------------------* 
3Cr-2Re ...-.--.-.--.-.-..---------.-- 
3Cr-2Re __.----.-_-.------------------ 
3Cr-2Re ..-..--....------------------- 
3Cr-2Re -.-._---..---------.---------- 
3Cr-2Re ..-...--.--------------------- 
3Cr-2% ..-----.---------.------------ 
3Cr-2 Re -..---.-._--"---------------- - 
3Cr-2Re- ---- --- ...................... 
- 3 .  - -  - 
BM4Zz*-. .----.-" ----.-" -.--------- 
p . ~ . ~ .  
20,000 
15,GGO 
1 0 , m  
20,000 
16,000 
I 
1 T A B L E  N 
1 
I 
-- 
Temp,, 
o F. 
1,860 
1,850 
1,850 
2, OW 
2,000 
T& short-time high temperature stre~rgtb of the afore- 
mentioned preferred alloys is shown in Table 111 wherein 70 The alIoys of this invention derive their high elevated 
ultimate tensile slrengths of both preferred alloys as-cast temprature strength from several mechanisms which can 
and in sheet form are given for various temperatures. include solid solution strengthening of the cobalt matrix 
The ultimate tensile strength of a prefened alloy of the by tungsten, chromium and rhenium, by the precipitation 
copending application at  room temmrature is presnled of the intermetallic We03 phase and by the formation of 
for comparison purposes. 55 various carbides of Ti, Zr, 0, W and Re. 
3,276,885 
5 6 
In an alternate embodiment of the invention this alloy 3. A co"oa1t-base alloy capable of high load carrying 
series can read~iy be produced In either a cast or wrought capacity at elevated temperatures consisting essentially 
form. These aHoys have excellent characteristics for in- of 69.4% cobalt, 25% tungsten, 1% titanium, I %  zir- 
vestment casting; yet, chill cast slabs can be hot rolled conium, 3% chromium, and .4% carbon. 
without prior working to thin strip with almost no edge 5 4. A cobalt-base alloy capable of high load carrying ca- 
cracking. Thin sheet sections of these alloys are readiiy pacity at elevated temperatures consisting essentially of 
weldable using electron beam qelding procedures, an im- 67.6% cobalt, 25% tungsten, 1% titanium, 1% zirconi- 
portant requirement for ducting components. um, 3% chromium, 2% rhenium, and 0.4% carbon. 
What is claimed is: 
1. A cobalt-base alloy capable of high load carrying 10 References Cited by the Examiner 
capacity at elevated temperatures consisting essentially UNITED STATES PATENTS 
of from 39% to 89.4% cobalt, from 10% to 45% tung- 2,996,379 8/1961 Faulkner ------------ 75-1 71 
sten, from 0.5% to 2% titanium, from 0.1% to 1% Car- 3,085,005 4/1963 Michael et al. -------- 75-171 
bon, from 0% to 3% zirconium, and from 0% to 10% 3,118,763 1/1964 Thielemann ---------- 75-170 
chromium. l5 3,223,522 12/1965 Rausch et al. --------- 75-171 
2. The cobalt-base alloy of claim 1 additionally con- 
taining up to 3% rhenium, the cobalt content of said alloy DAVID L. RECK, Primary Examiner. 
being adjusted to acconlmodate the addition. R. 0. DEAN, Assistant Examiner. 


High temperature cobalt-base alloy Patent

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