W. E. V d m , R. E. Pence, R. T. Massey arid R. T. Cassidy

Miamisburg, OH

and \

APSTIIACT

The f o m t i c n of a crack-free seal between a 300 series stainless steel an3 a

glass-cemnic hzs in the past been very difficult.

h s been in &taw glass-ceramic c a p s i t i o n s whose coefficient of t h e expansion

(CTE) approac'les that of the 300 series metal pi- parts. Stainless steels of the 300

series have very high CTE values that range fram approx. 180-220 x lo'' Q ~ / C Q / ~ C

(,E.-300°C).

'IZle p r L q cause of this difficdty

Therefore, the ccrresponding g l a s s d c &mild have a similarly high

t o w i l e the formtion of stress-free seals. Both a t E-M;-Mound and a t M;&G

Zlec t ; -cn ic ccxipnents, lithia-alumina-silica (m) glass-cadcs have ncw been

scccessfully developed and sealed to 304L stainless steel. These mck-free seals have

keen routinely fabricated using tm techniques: by adjusting the p r e n t glass carrposition

c r by a d j u s t b g t i le sealhg/qstallazation (or sealkg,/devitrification) cycle tht is

rmt ine ly used in forming seals between LAS glass-ceramic d nickel-&& alloys.

seals were determined to be hennetic, w i t h leak rates of < cc/sec of Srp helium.

Additional data on rn values and alloy yield strengths will be given which shw the

feasibility of using these materials in the manufacture of various cumponents including

All

feedthroughs and pyrotechnic mmpnents.

spztroscopy (W) results show the quality and integrity of the glass-ceramic/stainless

s t e e l interface.

Metallography, SEM and wavelength dispersive I

whenevex possible, these data are ccnrrpared to similar studies

DISCLAIMER

Portions of this document may be illegible in electronic image products. Images are produced from the best available original document.

.

DISCLAIMER

This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, exprcss or implied, or assumes any legal Iiabiiity or responsibility for the accuracy, completeness, or use- fulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any spe- cific commercial product, process, or service by trade name, trademark, manufac- turer, or otherwise does not necessarily constitute or impiy its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof.

feedthruugh wd a pyrotechnic &vice) are presented in Figure 1. Besides providing

electrical isolation, the glass-ceramic also must be chemically inert.

especially tme in various pymkchu 'c applications where the energetic materid is in

direct contact with the ijlass-ceramic. ('1

met&/glass-ceramic seal must be strong enmgh to w i t h s t a n d the pressure that is

developed when the energetic mterial is igniw.

its heticity to assure the optbum function of the ccnrrponent. Depemhxj cn the

qpplication, it h a m s apparent that the seal mtlst exhibit a d l e n t physical and

0ilemim.l properties.

utilize precipitation-hardenable srrperalloys, such as Inconel-718, have been

in re lo^&.(^)

msir usefulness in various applications.

these superalloys are tricky to lnachine and are very tmpemnmtal in their welding

characteristics.

stainless steels may be p r e f h .

available rrateridl which is easy to machine ard has very gcxd W e l M i l i t y , particularly

?Iris is

wing activation of these c a p n e n t s , the

In addition, the seal must maintain

For very high strength W t s , glass-Ceramic/metal seals that

H m e v e r , these supralloys have various deficiencies w h i c h have l i m i t e d

Frau experience, it has been determined that

when hi* strength is not a rquimwnt, other materials such as

A stainless steel, such as 304L, is a widely

when carpred to a superalloy.

fabricate glass%emnic/metal seals utilizing 304L.

apparent that the principle thrust of the investigation w a s abtaining glass-ceramic

mteridls which exhibited high C!IE values.

exist in d e r tertiary glass systms, such as I ~ ~ ~ O - Z R O - S ~ O ~ glass.(4)

this work deals only w i t h LAS CcnnpOsitianS primarily because of the degree of s u m at

Because of these advantages, research w a s undertaken to

Early on in the resarch, it became

Hi* expansion glass-ceramics are knm to

~c;rwever,

Mound and other DOE sites that has been noted in p y m t e d n 'c device d e v e l w when

sealing w i t h LAS glasses. ?herefore, this paw deals only W i t h developmt of LAS

glas~-Ceramic/3041 seals.

~ ~ z z - L ~ , ~

~m different amroaches were used to obtain LZS glzss-cerami : c materials which

&&it& very hi+ tkem\al expansions in the 170-200 X

f b t teckrticpe was based on the developrent of parent glass capsitions which would

cq-stdlize into hi* t h d expansion glass-cemmics after being subjected to a defined

tixe-tenprature &ixj/crystdllization (or sealing/devitrif ica t icn) cycle.

is presented in Figure 2.

stuciy wfii~h was perfomed by some of the authors. (5)

c a p s i t i o n in particular (which will be referred to as the 'high expansion' glass) was

identified a s shrnirc~ p d s e in f0xmh-q seals w i t h metals having high CTE values. The

a n p s i t i o n of this glass is presented in Mle I; the glass has a very -1

ccncmtraticn of a z o 3 . in mmfa&zrhj glass-ceradc/Inmel 718 seals is also shown in Table 1.

c n p s i t i o n will

cn/@C w e . n e

m i s cycle

This first technique was simplified .sawwhat due to an earlier

ram that w, one glass

mother glass ccnrposition w h i c h is presently used a t jwund

This

ref- ta as the ' w i n e ' glass. (6)

me secmd technique w a s based on developing a ti.Me--ture sealing/

crystallization cycle which could be used w i t h the tbaselinet LAS glass cumpsition, and

result in Lle desired very high themil. -ion glass-Ceramic. The specialized

tiw-terpxature sealiq/uystallization cycle which w a s developed is similar to the

cycle Shawn in Figure 2, but at this time it is underyohg patent evaluation so the exact

cycle nust remain propriety. ('1

could 5e xminplished h any reasonable prqranmble furnace typically used in formkg

31ass-~eramic coxp=ositions.

very high t h d expansion glass-ceramic.

~n any case, the cycle is not d i f f i d t t o perfom and

~s second technique was also successful in obtaining a

. 3941; sa~-J~(=s steel housixjs vere prqar&d to evaluate seal Lixgrity. TJO t p ~ ~ of

cmpnents w e r e fabricated using eit-z F ? l o y C-4 or Iiastelloy C-276 as p h

materials. Figure 1 shews photcxjrzph? of thLe k i types.

mysicd characteristics of the mnpmnt, such as hermeticity, alloy yield strength

cIF= meamrarmts w e r e performed U S ~ and CTE w e r e riwsurd us- classical t xhn iq~es .

a Theta ciual pushrod dilatm&er an3 the results are shcwn in Table 1. Single ckystd

sapphire was used as the reference mterial and the furnace w a s heated at 8°C/xnh fram

rccnn tenq=erature to 30OoC. Hermeticity was meamred on the finished cconponents With a

Veeco helium mass spectmwter leak tester.

was fourid to have a leak rate of

coqnnents w e r e helium leak tested; twenty feedthroughs an3 eleven p t e c b i c actuators

{see Figure I) All the c a p n e n t s passed the helium leak test.

samples were fabricated frcm 304L stainless steel and the effect on their tensfie

strength was detemined as a function of the time-tenprature sealing/crystallizatim

cycle.

cycle of Figure 2, the strength decreased to 28 hi.

A test piece was consi6ered hermetic if it

of STP hdiuq/sec. A totdl of tkirty-one

Sta.r&rd AS?M tensile

&-received 304L was measur& to have a yield strength of 61 k s i . After the

Saqles were &e for metallography by the usual method of cutting, mountirq an3

For the SEMJWES studies, the polished samples w e r e cart=on-coated. polishing.

o p t i d photajraphs were m r d e d on a Zeiss Metdllcgraph and the SEN/WIE results were

recorded on a JEOL 733 Suprprobe.

The

seal- of a metal to a glass-ceramic requires t \e ccrsideration of s e v w

=tal, the glass-ceramic and the interface formed between t l e t w o . If CI'E matching does

not OCQV, unwanted tensile or mmpressive Stresses can develop which could lead to

eventual destruction of the seal. High. streqths w i t h i n the metal/glass-Ceramic sealed

system are often rqy i red ; the mgniede of the strength is dictated by the final use of

the cmpnent.

LT most metal/glass-cemnic system, the metal has the higher CTE. Thus, the g c d of

this work was to fin2 d t a b l e LAS glass canpcsitions wkich, f o l l a h g devi t r i f icat ion

(or crystall ization), would yield caparable expansion coefficients.

illustrates t l e CTE plots of the b,m LFS glasses, 304L stainless steel, an3 the pin

materials of Hastelluy C-4 and Hastelloy C-276.

very high expansion coefficient, aFprox. 185 x

Figure 3

The data show 304L stahless t o have a

c ! m / e C (€U!-300°C), ard thus

requireS a high expansion glass-Ceramic for a match.

devitrified (or ceramd) t o give the prcper a. The glasses in Table 1 can be

The final glass-ceramic is not only

strower but chemially mre durable than the original glass. me devi t r i f id glass that

con+bir!s < 1 w t % alumina, the 'high expansion' glass, has an expansion that is closely

mtcled to the stainless steel. m e high CTE value for this glass was detexmined to

mt from the formation of tridymite m o r cristabdlite during crystallization.(5)

A match w a s also found with the 'baselinel glass that had been sealed b the stainless

w i t h the proprietary d ing /c rys t a l l i za t i an cycle. (7)

w e r e found routinely to be crack-free and hexmetic.

~n either case, resultant ~ e d l s

~n fidking glass-ceramic to metal seals, the molten glass must ke capable of

adequately Wetting the metal &a= and subeqwntly must be capable of forming a seal

w i t h the metal surface.

=tal as a result of chemical reacths be- the hot glass and the ~nztal(~,~) which

xcurs during the seal* step of Figure 2.

formtion of products that are lccated a few microns fm the metal/glass interface an3

Normally, seal foxmation h l v e s adherence of the glass to the

mese chemical reactions result in the

similar to the chemistry observed when seal- the IAS glass b Incanel 718 in previous

investigations. 8-10)

Yield strength of as-received 304L stainless steel, Wat is before the defined

tLw-tapr&..re sealing/oystdll ization cycle, w a s measured t o be 6 1 ksi; however, after

L ie cycle, +,e streqtkk decreased b 28 ksi. This decrease in strerlgth can be attributed

t o tke annealing of the stainless steel which causes softening of the metal. Yield

strexqtlhs were also masurd for Inconel 718 under the same conditions, t h a t is fol1aJh-g

L le cycle Wi',cut precipitation hardening (see Figure 2). I n Inanel-718 the strength

was found *a increase after the cycle because of formation of the precipitation-hardenbg

phase, Ni3Nb.

sealing,/crystallization cycle neans that cmpnents made with 304L have the potential of

Thus, the fact that the stahless steel iS weakened during the

not be- as strong as empnen t s made w i t h Inconel 718. Although the stainless

cmpnerlts my not be as strong, this work shows they can be routhely prccfuced, and

the i r seals cm be made crack-free and hennetic.

c m p n e n t s khick do not

Thus, 304L would be better suited f o r

very h.k& s l z .

-->- *-- , LA.i+us;c:s

~rack-free hernetic 304yLAs glass-ceramic caipments an be routinely f ab r i caw

? ~ r i ? g eiL?er one of t w o developed tedmkpes.

L%e LAS parent glass ampsi t ion , by rettucing t l e U203 content, or altering the

sdirq/crystal l izat ion cycle.

w e r e relatively stress-free due to the "mtching" of the ccefficients of t he rm&

expansion between the 304L stainless steel houskg and the glass-ceramic. Seals

?he techniques hvolved eitler alter%

The mmpnents t h a t w e r e prcctuced by either procetture

fabricated with 304L have k e a determined to form by means of a chemical reaction.

During seal- the 304L m e t a l shell reacts w i t h the hot glass caushg the formation of an

interface consisting of reaction and diffusion zones similar to the well-studied m e 1

718/T;is system.

systms wculd be useful for lmer strength applications.

Yield Stzm detemhations on the 304L mnpnents shm& that these

?xe fact that 304L is mre

readily weldable than the N i - b a s e d alloys also m3ce-s it attractive for 'C

campnents where r?& assembly often requires laser welding.

7

1 A.

2 .

3.

4.

5.

6 .

7 .

a.

9.

10.

Miamisburg, OH 45342, December, 1986.

0. L. m e t t and L. C. ala, t fcmpnent cha.z?--adtistics d melopent ~ e p o r t " ,

S~w6-0699, Sandia National Laboratories, Albuquerque, NM 87185, May, 1987.

D. P. I0mne.r and R. T. Massey, Ceramic F3xT and Science pToc., 5/7-81, 739 (1984).

f i l l a n , P. W., Glass-Cerarm 'cs, Second Edition, Academic Press, Iandon, 1979.

D. P. Kraxler, G. L. Ramfile, D. A. l3uckner, J. P. McCarthy, A. B. Nease and D. B.

Sullqer, Thysicdl property changes of a Lithia-AlUmina-SiliCa Based G l a s s as a

Fmction of Ccmpusitionlt, MIX-3272, Monsanto Research Cmpration-Mound, MiaixL,sburg,

OH 45342, July, 1985.

H. L. itlccollister and S. T. Reed, IfGlass-C"ararm. 'c Seals to Inconelf9, U.S. patent 4 414

282, November, 1983.

Fcr mre information contact one of the authors, D. P. Xramer.

R. D. Watkins ard R. E. Loehrran, IIInterfacial Rwictim Between A Caqlex Lithiium

S i l i c a t e Glass-Cerarm 'c and mco& 718l*, Attvanced ceramic Materials, ~(i), 77-80

(1986) . S. M. Craven, D. P. Kramer and W. E. ploddeman, lfCh&stry of GZass-Cerarm 'cs to Metal

Bc;lding for Eeader @lications. 11. Hydrosen -le Formation lxlrhq Glass-Cerarm 'C

to N e t a l Sea lkg@l , MLM-3403, &caber , 1986, Mansanto Researdl COrporation-Ysdnd,

Mhmisburg, OH 45342.

W. E. M c d 6 @ ~ n , S. M. maven iL?d D. P. Kramer, I1Ni3Nb Alloy Species in Oxide

Surfaces of Inconel 718", J. Aner. Ceramic Soc., 68(111, 298 (1985).

P

Table 1 Materials Us& In Fabricating Sta in less Steel/

G l a s s - C e r a m ‘c ccnrq?onents (data given in wt%)

Si0,- p2%-

2.45 tbaselinet 75.0 glass

1 2 . 3 4.75 4.2 1.3

‘high expnsion’ 77.7 glass

12.2 <O. 94 4.6 2.41 2.72 -175

304L 72.0 18.5 10.0 KO. 1 <0.04 -180

16. 61. 16. - 2. 1. 0.08 0.15 -126

‘h2StdlOy C-276 5.1 14.8 55.1 15.9 2.5 3.9 1.5 0.08 0.02 -125

CTE = coefficient of Dmmal Expansion. * ** *** ****

Hastelloy C-4 also contains 0.7 wt% titanium. Resultant C E after sealjng,/cqstallization cycle shcwn i n Figure 2. Resultant after proprietary sealing/crystallization cycle.

Figure 1.

Ficpre 2.

Figure 3 .

F k ~ u r e 4.

Figure 5.

Figure 6.

%IO Cmp1e.x Cumprmts Fabricatd w i t h 304L Stainless S W / G Z a s s - c e r a r m 'C

Seals: a) F&thmughandb) pyrotechru 'c mice.

~ine-~emperature Crystdllization/Sealing Cycle for Processing Glass-Cerarm 'c to

Metal seals.

ccefficient if ~hermal Expansion (CTE) plots of the

Expansion' GZass-Cerarm 'cs, 304L Stainless S W , an3

Ir,conel 718, Hastelloy C-4 and C-276.

optical phatograph (20x) Smwirg a CraCk-Free pymtechru 'c Device Fabricated

With 304L Stainless Steel.

SEM p h o t c r m i ~ p h ( E O x ) Showing Reaction and D i f u s s i o n Zones at the

Metal/LAs Interfaces. Metals are 304L Shell an3 Hastellay C-276 Pin.

h , Mts shuwing Diffusion of chraminum fm 304L S t z i b l e s s Steel into LAS

G l a s s .

c

0 "( 5 0

0 U I

L

p. c',

0 0 0 /

/

, /

C 3 0

73

0 0 0

- c 0 .-

c .- E 0 a 0 N

, o o b o m a m

t a. a. 0 c

c.r

- Q)

E t- .-

\ c .- E m 7

t I c I

/ c .- E

0

0

c

m a tn

200

180

160

140

120

100

.-.I 0 HASTELLOY C-276

,- HASTELLOY C-4 9 .-=- HI- EXP'GLASS

.-+-- BASELINE-GMSS -- 304-1: STAINLESS

I 1 I I I I I I I a I I I I

0 200 400 600 TEMPERATURE (oC)

800 1000

i

a

x 0

between 304L (left) -i-

- -____--__-- -I____

0.028 reglon , . .

Ledger: 0 C r +NI 4 Fe 0,022

0.02

304L v) 0

ar: I

Y

stain less steel Shell

5

0.008

0.006

0.004

0,002

react ion zone

U S glass-ceramic

dfff usion zone

.. 0 40 80 120 160 200 240

Mlcrons