Note: Descriptions are shown in the official language in which they were submitted.
~o 5340 8 CER 15
DESCRIPTION OF THE INVENTION
.
Dental restoration generally comprise a metal core
or framework to which porcelain is bonded on the visible
surfaces for esthetic reasons. For many years gold has
been the basic structur~l metal for preparing the metal
core or framework. However, because of the cost of gold,
many attempts have been made to devise non-precious metal
alloys which could be used in place of gold. Such compositions
are illustrated, for example, by U.S. Patent Nos. 1,736,053;
2,o89,587; 2,156,757; 2,134,423; 2,162,252, 2,631,095, 3,121,629,
3,464,817; 3,544,315; 3J685,115; 3,716,418; 3,761,728; and
3,834,024, and ln standard dental literature such as Sk~nner
and Phillips, "TH~: SCIENCE 0~ DENTAL MAq~ERLALS," p. 582,
Sixth edition, W. B. Saunders Com~any, Philadelphia and London,
1967 and Morrey and Nelson, "DENTAL SCIENCES H~NDBOOK," p. 168,
~erican Dental Association and National Institute of Dental
Research, U.S. Government Printing Office, Washington~ D.C.,
1970. Suitable alloys are generally nickel or cobalt-based
alloys~ particularly, nlckel-chromium alloys.
,
When such non-precious metal alloys are to be employed
as a framework or core to be faced with porcelain, generally
the porcelain is fired directly onto the metal surface and
is held there by mechanical bonding. To produce mechanical
bonding, a surface roughening of the metal is required.
Appropriate roughening for mechanical bonding is extremely
difficult. Moreover~ mechanical bonding is not always adequate
to endure the stresses of daily use and a separation of the
porcelain from the metal framework in whole or in part
lQ534~`8
~E~ l~?
frequently occurs. It is desirable to provide a
bond resistant to such separation.
The present invention is directed to bonding
agents and more particularly, it relates to compositions
and methods for bondingdentalporcelain to a non-precious
metal alloy ~ramework. When dental porcelain is bonded to
the metal framework using the bonding agents of the present
invention, a strong bond is formed which is able to resist
separation of the porcelain under far greater stresses than
ln the absence of bonding agent. Moreover, the components are
free of materials which cause tissue necrosis or present
toxicity problems.
,
The bonding agent composition of the present invention
comprises: (1) a metal to porcelain bond forming component
consisting of powdered aluminum in admixture with a
powdered glass, said glass being characterized by fusing
at a temperature in the range of about 1750F. to 1850F.
preferably about 1800F. with (2) a carrier componen~ which
is a substance capable of providing a reducing atmosphere
during the firing or baking of the bonding agent. Glass
as herein employed is a mixture of non-crystalllne oxides
as ls generally understood in the art and hereinafter more
fully described. The carrier may be an inert carrier having
no function than as a carrier and the reducing atmosphere
necessary during the baking or firing of~the bonding
agent provlded by separately supplied reducing gases; however,
"` ~Q534(~t~
the preferred embodiment of the present invention contemplates
the reducing atmosphere to be supplied by the carrier component.
The expression "bonding agent composition" as herein employed
refers to both the bonding-forming component and carrier. The
expressions "bond-forming component" and "bond-forming agent"
refer to the aluminum-glass mixture. The expressions "core",
"framework", "substrate", and "structure" when employed with
"metal" are intended to have the same significance and refer
to the dental structure which is to be faced with porcelain.
Broadly, the invention relates to a bonding agent
composition suitable for bonding dental porcelain to a metallic
core of a non-precious metal alloy in a dental restoration
comprising (a) a bond-forming component of powdered aluminum
in admixture with a powdered glass fusing at temperatures in
the range of from about 1750F. to about 1850F., and (b) a
carrier component comprising a liquid organo-silicon compound
capable of providing a reducing atmosphere at temperatures of
from about 1200F. to about 1900F., wherein said glass is of
a mixture of oxides which include the following in approximate
weight percent: 47-74% silicon dioxide; 1-16% aluminum oxide;
3-17% sodium oxide; 0.6-6% calcium oxide; and 0.4-4% magnesium
oxide.
In a preferred embodiment of the present invention,
the bond-forming component is a mixture of aluminum and a
glass fusing within the range 1790 to 1810F. The aluminum
is in the form of a powder capable of passing through a 400
mesh screen and is preferably in the form of a powder of
particle size of 20 microns or finer. The glasses are a
mixture of non-crystalline oxides which include silicon
dioxide, aluminum oxide, sodium oxide, calcium oxide and
magnesium oxide; it may contain one or more of the follow-
~ _ 4-
ios3~08
ing oxides: stannic oxide, potassium oxide, lithium
oxide, boron oxide, titanium oxide, barium oxide, zirconium
oxide, etc. The amounts of the first-named oxides which
may be called the essential oxides may vary significantly
depending on the presence of and/or amount of the latter
or non-essential oxides. Thus, the essential oxides may
be present in amounts (by weight) as follows: a~out 47-74%
i - 4a -
1 053~08
CER 15
silicon dioxide, 1-16~ aluminum oxide~ 3-17~ sodium oxide,
o.6 to 6~o calcium oxide and 0.4-4% magnesium oxide. The other
oxides may be present in amounts as follows: 0-12% potassium
oxide, 0-25% stannic oxide, 0-5% llthium oxlde, 0-2% boron oxide
and 0-2% barium oxide. The preferred glasses are those in
which the oxide compo~ition may be within the following ranges
in percent by welght: 47-63% silicon dioxide; 9-25% stannic
oxide; 10-14% aluminum oxide; 8.5-10% potassium oxide; 3-5%
sodium oxide; 0.6-.13% calcium oxide; o.4-o.8~ magnesium oxide;
and 0-5% lithium oxide. Many suitable glasses are available
commercially as glassl porcelaln, ceramic oxides, etc. Other
glass compositions may be prepared by dry blending the
appropriate oxides in appropriaté amounts, fusing the mixture
to a frit~ quenching with water, drying and ball-mil~ng to
appropriate fineness as known in the art. The glass compositions
arç powders of particle size such as would pass through a
165-mesh screen (about 60 microns) or finer. The particle slze
of both the aluminum and the glass compositions are based
primariIy on the finest currently-available powders. When flner
powders become available, such would be desirable.
The carrier component of the novel bonding agent composi-
tions of the present invention are liquid organic silicon
(organosilicon) compounds such as silicone oil, silane, etc.
Suitable liquid organic silicon compounds are those which
maintain appropriate fluid paint-on characteristics after
incorporation of the bonding agent component powder. Preferred
organic silicon liquids are those having a viscosity range of
from about 4 to 40 centistokes at 25C. or 6 to 17 centistokes
105340~3
CER 15
lC~0 1~. or 45-85 Saybolt seconds. These organosilicon
compounds, in addition to providing appropriate fluidity
properties, also provide a reducing atmosphere.
In compositions comprising a powdered mixture of
aluminum and a glass in a liquid organic silicon compound,
the exact amount of liquld carrier to be employed with the
powdered mixture is not critical. Generally, such amounts
of liquid organosilicon compound is employed as to provide
the appropriate fluidity for painting on metal surfaces.
Employing liquids havlng a ~iscosity in the range of about 6
to 17 centistokes at 100F, compositions having æuitable paint-
on properties may be prepared by comblning for each part by
weight of solid bonding component mixture from 0.25 to o.75
parts by volume of liquid~ Usually the solids content of the
composition is from about 60~ to 80% by weight.
The relative amounts of aluminum and glass are
important. The alumlnum component may constitute from
about 40 to about 70 percent of the total solids mlxture,
the balance being the glass component. Good results are
obtained with a 50:50 mixture of aluminum to glass.
The bonding agent compos~tion may be prepared by
intimately admixing the bond-forming component and the
carrier component in any suitabl~ manner tO obtain a
substantially uniform slurry composltion. Preferably,
1053408
CER 15
the solids, i.e. J the aluminum and glass powders, are pre-
blended and the powder blend intimately admixed with the
liquid organosllicon compound. The preparation of the
compositlon by admixing may be carried out just prlor to use
or the powder blend and llquid may be premixedJ i.e., the -
slurry compositlon may be pre-prepared. The composltion may
be employed by dental technlcians employing conventional
techniques,
The present invention i8 also concerned with employing
the bonding agent compoæition o~ the present in~ention to
securely adhere or bond dental porcelain to a metal core. A
preferred embodiment contemplates the use of the above-
described novel bonding composition in admixture with a
carrler component whlch provides a reducing atmosphere.
However, the present inventlon embraces the employment of
other means for providing a reducing or a non-oxidizlng inert
atmoæphere and the carrier component belng merely an inert
liquid of approprlate fluid properties.
In accordance with the method of the present invention
of bonding dental porcelain to a metal core or framework, the
novel bonding agent composition is applied uniformly to the
appropriate ~urface of the metal core which has been prepared
employing conventional techniques such aæ the Loæt Wax Technique
and which has been thoroughly cleaned such as with dilute acid
and/or sandpaper, and the coated metal core then baked in air
in the temperature range of about 1200F to about 1900F. in a
.
~ 053408 CER 15
dental porcelain furnace. The coated and fired metal core is
removed from the furnace, allowed to cool and then cleaned by
brushing off loose material and washing ultrasonically with
warm water and thereafter dried. The porcelain is then applied
and the resulting porcelain-coated metal core or framework
fired in a conventional manner.
In carrying out the first of the foregoing steps, the
bonding agent composition is applied in any suitable manner.
Generally, painting on with a brush is convenient. Good
results are obtained whether the coating may be described
; qualitatively as thi~k, thin or medium. It is critical and
es8ential that all surfaces be evenly coated with the bonding
agent composition.
In carrying out the baking step, the exact temperature
and time of heating may be varied. In a method con~enient
for use by dental technicians, the coated metal core is placed
- in a furnace preheated to l200F. and rapidly heated in air
to a maximum temperature in the range of-from about 1800F. to
about 1900F. at a rate of heating of about 90-100F. per
minute. PreferablyJ the maximum temperature is in the range
of from about 1840F. to about 1860F. The total heating
time when thé heating is carried out in this manner is less
fifteen minu-tes. Alterna-tively, heating may be carried out
at a lower temperature for a longer period.
1053408 CER 15
When the baking step is to be carried out in a non-
oxidizing (reducing or inert) atmosphere which is to be
provided by a source other than the carrier component, the
furnace is filled with a reducing or inert gas such as
hydrogen, nitrogen,.methane~ carbon monoxide, argonJ etc.
during heating. The coated metal core is heated as above
described.
The step of cleaning the surface of the coated metal
after baking on the bonding agent is also critical and essential
~o the obtaining of good adherence of porcelain to the metal.
~hen the cleaning step is omitted cracking of the porcel~in
is seen to occur Cleaning with a brush and then ultrasonically
. with water appears tQ give the best results although other
methods which remove non-adhering materials may al80 be
employed.
The porcelain is applied to the.bonding agent coated
metal surface~in any appropriate manner normally employed to
coat metal surfaces in theabsence of a b~nding agent. Pre-
~erred methods are painting on with a brush or coating with a
spatula. After application of the porcelain, the porcelain i8
fired.at temperatures appropriate for the particular porcelain
and metal employed. Thus,.it may be carried out at any
appropriate temperature range within the broader limits of from
about 1600F. to about 2000F. Thereafter, addltional coatings
f porcelain may be applied and fired in a conventional manner
to complete the production of the dental restoration in which
a bond is formed between the metal and porcelain which is
resistant to separation on application of mechanlcal stresses.
The bo ~ g agent compositions of the present inven-
tion are adapted to be employed with metal alloys and porcelains
which are suitable for use together in the absence of a bonding
a~ent.
Metal alloys for which the bonding agent compositions
of the present invention are most useful are the nickel and
cobalt based alloys, particularly the nickel-chromium alloys.
Representative alloys are found in the aforementioned patents
and dental literature on non-precious metal alloys. Other alloys
with which the bonding agent composition may be employed are
available under various trade names. Still other alloys with
which the bonding agent compositions are usefully employed are
the subject matter of Canadian application No. 244,988 filed
January 30, 1976.
The porcelain which is to be bonded to the dental alloy
may be any porcelain appropriate to be employed with the alloy
chosen. By "porcelain" is meant dental porcelain as known in
the art and embraces dental glasses. They generally contain
silicon oxide, aluminum oxide, potassium oxide, sodium oxide,
and minor amounts of other oxides. Normally, the porcelain
covering which is first applied to the metal is an opaque porce-
lain. An opaque porcelain reduces the tendency of the metal
to be seen through the final coating. Opaque porcelains are
available commercially and include in the oxide composition either
zirconium oxide, tin oxide, titanium oxide, or zirconium sili-
cate as an opaquing agent. The opaque porcelain is normally
coated with a relatively thick layer or layers of body porce-
lain followed usually by a final layer or coating at the tips
of incisal porcelain. The body porcelain is available commer-
cially as gingival or body porcelain (sometimes called dentine)and may have a small amount of opaquing agent, and incisal por-
-- 10 --
1053~8
celain is usually of similar composition as body porcelain with-
Ollt opaquing agent. In all coatings subsequent to the first
coating, porcelain is bonded to porcelain. In the first coating,
porcelain is bonded to metal and the problems to be solved by
the bonding agent composition of the present invention are with
the porcelain-to-metal relationship. Thus, it is solely the por-
celain which is to be bonded to metal which is of concern in the
practice of the present invention. Since under present prac-
tice, the porcelain which is bonded to metal is that understood
in the art as opaque porcelain, the porcelains which are to be
bonded to metal by the bonding agent compositions generally are
opaque porcelains although not limited thereto,
Procelains which are advantageously bonded are feld-
spathic porcelains and are similar in oxide content to the glass
component of the instant bonding agent. Typical porcelain com-
positions are found in standard references such as Skinner and
Phillips, "THE SCIENCE OF DENTAL MATERIALS," p. 518, W.B. Saun-
ders Company, Philadelphia and London 1967; the compositions of
several commercial porcelains are listed on Page 60 of Jean-Marc
Meyer, "Contributions a l'Etude de la Liaison Céramo-metallique
des Porcelaines cuites sur Alliages en Prothèse Dentaire,ll Thesis,
University of Geneva, 1971. Suitable porcelains include those
having compositio~s described in U.S. Patent 3,052,982 of the
following oxide content: 61-67.8% SiO2; 11.7-17.1% A1203; 0.1 -
2.6% CaO, 0.1-1.8% MgO, 2.37-9.6% Na20 and 6.7-19.3% K20. The
foregoing composition may be modified to include lithium oxide
in amounts up to 5% and/or opaquing agent in amounts from about
0.05 to about 25% and the other oxides reduced or modified. Suit-
able opaque porcelains may have the oxides inthe following approx-
3~ imate ranges: SiO2 47 to 63%; A12O3 10 to 14%; CaO 0.6 to 1.3%;
K20 8.5 to 11%; Na20 1.5 to 5%; MgO 0.4 to 0.8%; and Sn02 9 to
25%. The present invention is not directed to the chemical
-- 11 --
1053~08
compostion of the porcelain; thus, any commercially-available
dental porcelain or porcelain compositions prepared by a skilled
artisan may be employed. Some of the commercially-available
porcelains include CERAMCO* Opaque Porcelain, CERAMO* Gingival
Porcelain, BIOBOND* Opaque Porcelain, BIOBOND** Body Porcelain,
VITA*** Porcelain, etc.
The selection of the porcelain in terms of exact com-
position is dependent to a greater degree on the metal alloy
substrate which is to be faced with the porcelain than on the
instant bonding agent. For the bonding agent to have the advan-
tageous properties provided by the present invention, it is ex-
pected that the selection of the porcelain be appropriate for
the metal alloy core or substrate employed. Thus, the thermal
expansion properties of porcelain should be compatible or reason-
ably matched with that of the alloy. It is recognized that a
meaningful single coefficient of expansion is not obtainable for
porcelain as it is for metal over the broad temperature range
of about 25 to 600C. and that coefficients of expansion values
are valid only for a narrow range of temperatures. Frequently,
therefore, after preliminary determination of the coefficients
of expansion, empirical methods are employed for the selection
of the porcelain to be employed with the, particular alloy. The
method of selection of porcelain for use with a particular alloy
is not part of the present invention, but when a reasonably
"matched" porcelain and metal alloy are to be bonded together,
the use of the present novel bonding agent greatly enhances the
bonding properties. Thus, even porcelain-to-metal bonds which
by previous standards would be considered to be good bonding
appear greatly inadequate when seen in the light of the present
invention.
* Trademark of Johnson & Johnson or Affiliated Company
** Trademark of Dentsply International, Inc., York, Pennsylvania.
*** Trademark of Vita Zehnfabrick, Saechiagen, West Germany
~053~(38
The greatly superior strength of the bond provided by
the bonding agent compositions of the present invention may be
demonstrated qualitatively and quantitatively. Thus, when
mechanical stress such as a hammer blow is applied to crowns
or test disks faced with porcelain prepared by employing a
bonding agent of the present invention, there is substantially
little or no separation at the porcelain-to-metal interface
whereas when it is applied to those prepared without use of bond-
ing agent, the porcelain tends to separate cleanly from the
metal.
The strength of the bond at the interface may be fur-
ther demonstrated by cutting or sawing a slit on the porcelain
face, inserting a flat bar or knife blade into said slit and
applying torsional force. The crowns or disks prepared without
use of the bonding agent completely or substantially completely
separate at the porcelain-metal interface on application of this
unusual force while the crowns prepared by the use of the bond-
ing agent of the present invention remain securely bonded. Thus,
even when extraordinary stresses are applied, the porcelain-to-
metal bond remains intact and fracture or fractures occur insteadwithin the porcelain structure.
The bond strength may also be demonstrated quantitati-
vely. However, the actual values may vary depending on the par-
ticular alloy and porcelain combination, on the method of deter-
mining bond strength, or on the treatment of metal surface prior
to bonding. Thus, when the bond strength is measured as a force
required to separate a metal rod from a porcelain disc bonded
circumferentially around such rod, the quantitative values are
found to be higher than when the bond strength is measured as a
force required to separate porcelain bonds between the end faces
of two rods. Also~ the porcelain to metal bond strength values
generally are higher when porcelain is applied to a sand-blaste(l
- 13 ~
~53~(~8
surface than when applied to a polished surace or even to an
untreated surface. However, whatever quantitative values may be
a.ssigned, it is found that for any particular combination of alloy
and porcelain, bonding strength is unexpectedly superior when
the bonding agent compositions of the present invention are em-
ployed.
The success of the bonding agent composition of the
present invention appears to be associated with the ability
to provide a bond forming component in elemental and oxidized
forms at appropriate times at the interface region. The provi-
sion of a reducing atmosphere insures the presence initially of
the bond forming component in the elemental form. On continued
heating, conversion of a desirable portion of the bonding com
ponent to an oxidized form is believed to take place which can
subsequently react with the porcelain during the porcelain firing
step. However, when the heating is over an extended period or
exceeds about 1950F., the bonding power is found to have been
diminished when subsequently porcelain is applied and fired. The
invention, however, is not limited to any particular theory. Re-
gardless of what explanation may be advanced as to what happens
at the interface, a superior bond is obtained by the employment.
of the bonding agent composition of the instant invention.
The following examples illustrate the invention, but
are not to be construed as limiting:
EXAMPLE I
A bonding agent having the composition set forth below
is prepared by intimately mixing together the components.
COMPOSITION I
Aluminum powder (-400 mesh) 2 grams
Glass 2 grams
- 14 -
~0534~8
SiO2 49.64% by weight
A123 12.04% by weight
Na20 3.60% by weight
CaO 0.76% by weight
MgO 0.48% by weight
K20 8.40% by weight
SnO2 21~0~/o by weight
Li20 1.19% by weight
B203 0 . l~/o by weight
~e23 0.013% by weight
BaO 0.14% by weight
Silicone Oil*about 1.5 milliliters
The resulting composition is a fine slurry suitable
for painting on metal. The foregoing bonding agent composition is
painted on flat disks of a non-precious metal alloy. The alloy
employed is of the following composition in weight percent: 71.3%
nickel; 19.1% chromium, 4.~/0 silicon, 4.1% molybdenum; and 1.4%
boron and is the subject matter of Canadian application No. 244,
988, filed January 30, 1976.
The painted disks are dried at the door of a dental
furnace and then heated in the furnace at temperatures of
from 1200F. to 18~0F. in air. The disks are removed from the
furnace and bench cooled. After cooling, the disks are brushed
with a toothbrush and water to remove loose particles of bonding
agent and then ultrasonically cleaned for 5 minutes with warm
water and dried~ CERAMCO* Opaque Porcelain is then applied to
the surface and fired according to manufacturer's directions. A
layer of CERAMCO* Gingival Porcelain is also applied and fired.
Thereafter, each specimen is cut through the porcelain layer with
a DEDICO** Cut Off Wheel to form a slit, and a screwdriver placed
in the slit and torsional force applied to attempt to pry off
*Silicone Oil - GE No. 69, viscosity 6-17 centistokes 100F,
density 8 lbs./gal. GE No. 69 is a TrademarX.
*CERAMCO - Trademark of Johnson & Johnson
** DEDICO - Trademark
1053~ 8
the porcelain. The porcelain is resistant to separation from
the metal.
- 15a -
1053408
CER 15
EXAMPL$ II
In a similar manner, a bonding agent of the following
composition 1~ prepared.
COMPOSITIO~ II
Aluminum powder 2 grams
Glass* 2 gr~m~
Sillcon Oil (GE #69~ 2.5 mllllllters
*Same oxlde content as in Composltion I.
The composi~ion 1s a slurry sultable ~or applying
on metal surfaces by palnting.
The strength of bon~ formed between metal and
O porcelain by employing the foregoing b~ndlng agent
composition is determlned by tests measuring mechanlcal
properties in the following manner:
.
Employing the no~-precious metaI alloy (o~ composition
described ln Exa~ple I), slugs which are 1 centlmeter ln
length and 3/8 inch ln diameter, are prepared. For each
test, a pair of slugs are employed. Each pair of slugs are
poli6hed on one end with sandpaper. The bonding agent is then
applied to the pol~shed ends and baked by placing in a furnace
preheated to 1~00F. and the temperature raised in air at a
rate of 90-100F. and the temperature raised in alr at a rate
of 90-100~./minute to 1850F. On reaching 1850F, the slugs
are removed from th~ ~rnace and bench-cooled.
16
10534(~8
CER 15
The test slugs are cleaned in a manner similar to
that described in Example I and dried. Thereafter, a layer
of opaque porcelain (same as that employed in Example I) is
applied to the bonding agent covered surface and fired by
heating from 1200F. to 1700F. in vacuum (about 29 inches
of mercury) and from 1700F. to 1850F. in air.
Then, a second layer of the same opaque porcelain is
applied and the porcelaln covered surfaces are ~oined together~
Enough porcelain is applied so that when the porcelain-covered
1~ ends are joined, theré iB sufficient porcelain to extend
beyond the perlphery, the excess compensating for the 8hrinkage
which occurs on firing. The ~oined slugs (test specimens)
are heated in a furnace at temperatures of from 1200F to
1700F in vacuum and from 1700F. to 1850F. in air. After
reaching 1850F., the ~pecimens are maintained at that
temperature for 2 minutes.
Control specimens, employing no bonding agent are
prepared by (a) polishing one end of each pair as above
described for the test 6pecimens; (b) applying opaque
porcela1n o~ the same composition as for the test specimens
to the polished ends and firing; and (c) applying a second
layer of porcelain, ~oining the two ends and firing; the
procedure differing only in the omission of the steps of
applying and baking on of the bondlng agent.
17
10534(~8
CER 15
The excess porcelain on the test and control specimens
are ground off so that the diameter of the porcelain portion
is of the same dimension as that of the metal.
The slugs are then employed for testlng mechanical
properties in the INSTRON Instrument. In view of the small
size of the test specimens special adapter~ are prepared for
retaining the specimens while carrying out certain of the
measur~ments. The tests employed are as follows:
Tensile Strength: The specimens are placed directly
in the INSTRON and the force necessary to ~racture the specimen
by exerting a pulling force at opposite ends of the specimen
are noted,
Shear: The specimens are placed in an adapter compris-
ing two bars with an orlfice penetrating through each bar, the
orifices are capable of being aligned above one another and
retaining the specimen. The specimen is positioned so that
the porcelain-to-metal interface coincides with the interface
of the two adapter bars which are to be pulled in opposite
direct~ons. The adapter is placed in the INSTRON and the force
necessary to ~racture the specimen is measured.
Torsion: The specimens are placed in an adapter which
is designed to hold one end stationary while a twisting force
is applied to the othsr end and the adapter is placed in the
~NSTRON and the relative torsional force necessary to fracture
18
1053408
CER 15
the specimen is determined and recorded as levels. Torsional
level as herein employed is a calculated number based on the
load necessary to fracture the specimen multiplied by the
distance from the specimen at which the force is applied.
T~ree-Point Loading: The specimens are placed in a
special three-point loading apparatus mounted on the INSTRON
and the compression force necessary to cau6e failure at the
metal-porcelain interface read on the INSTRON.
Impact Testing: A device is prepared consi~ting of
two metal bars whlch are held side-by-side. These bars are
hinged in such a manner that one bar is fully rotatable
while the other is held stationary in a vertical position.
The test specimen is held on the stationary bar with a portion
extending over the edge of the first bar in a direction such
that it would be in the path of the second bar when the latter
is rotated. The secon~ bar then is swung at a measured force
and the relative force necesæary to cause fracture is
determined. Impact level as herein employed is a number
based on the linear distance travelled by a moving bar of
constant weight to cause fracture of the test specimen.
The difference between the values for the control specimen and
the test specimens are considered to be of greater significance
than the actual numerical values. The results are seen in Table I.
19
` 1053~08
CER 15
TABLE I
Mechanlcal Properties*
Tensile Shear 3-Point
Stren~th Strength Torsion Loading Impact
Specimen (psi~ (psi) (psi) (level)
Test ~onding agent) 5019 5889 3.056 10206 7.6
Control (no bond- 1781 - 2815 1.678 4153 3.6
ing agent)
*Test specimens - a~erage of seven to ten determinations.
Control specimens - average of flve to elght determinations
(except tenslle ætrength;average of two determinations).
EXAMPLE II
In a slmilar manner, a bonding agent having the
composltion set forth below i8 prepared.
COMP~SITION III
Aluminum Powder t-400 mesh) 3 grams
Glass* 2 grams
Silicone Oil (GE #69) 2 mllliliters
*Same çomposition as glass of Compositlon I.
.
The composition is applied to a clean metal core of a
non-precious metal alloy of the same composition as set forth in
Example I. The painted metal core is then dried, baked, cleaned
and faced with porcelains of the same compositions as employed
in Example I.
1053408
CER 15
The porcelain layers are then cut and torsional
force applied as descrlbed in Example I. It i~ found that
there is fracture of the porcelain but the metal-to-porcelain
interface remainsintact.
EXAMPLE IV
Aluminum powder and one or more glass compositions
(each consisting of a mixture Or oxides) are lntimately mlxed
together with silicone:oll to obtain bonding agent compositions
as substantially uniform slurries. The amounts of aluminum,
each oxide component of the glass, and the ~olume of organo-
silicon compound in the ~arious composltions are 11sted in
Table II.
21
~053408
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a~ O O O O O O O I O O O O
a~ . . . . . . . . ~ . .
N ~1 ~1 0 N N N ~1 ~1 0 ~1
O I O O O O O O O O O O
C~J O O O O O O O I OO O O
m .
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-
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_ n ~0 ~ 00 ~ OD ~0 ~0 ~o c1~ 0 ~ oo N
ct 'C~ ,1 ~1 ,~ ,1 ,1 ,1 ~1 _1 ~1 ,1 ,1 ,1 ,1
~ ~ , ......... ,, .
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b O N ~ r ~ N N N ~I C-- ~ ~ i
H _ al 0 .~1 0 0_I ~0 o o N~ a~ a ~ O
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; ~ ~I r o
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2~
1053 408 CER 15
The compositions are employed to test for bonding
properties in a manner similar to that described in Example I.
Thus, the compositions are painted on flat disks of a nickel-
chromium alloy of the same composition as that described in
Example I, the painted disks baked, then porcelaln (CERAMC0*
opa~ue) applied and fused onto the disks to obtain test
specimens. The porcelain layer 1s cut and torsional force
applied as previously described and the bond assessed as
good or bad. If there is no separation at the metal-porcelain
interface and the fracture occurs in the porcelain, the
bonding is considered Good; if there is separati4n at the
interface, the bonding is considered Bad.
The bonds in all the speclmens employing the bonding -
agent compositions llsted in Table II are rated Good.
- EXAMPLE V '
,
In a manner similar to that described ln Examples I,
III, and IV, bonding agent composltions having the following
compositions are prepared.
*Trademar~F Johnson & Johnson or Subsidiary.
.
~3
~os340s
CER 15
COMPOSITION IV
Aluminum powder (-20 microns) 2 grams
Glass 2 grams
SiO2 68~ by weight
A1203 3-% by weight
Na20 16% by weight
CaO 6.o% by weight
MgO 4.0~ by weight
K20 0.5% by weight
B203 1.5% by weight
BaO 2.0~o by weight
Silicone Oil (GE #69) 1.5 milliliters
COMPOSITION V
Aluminum powder (-20 microns) 2 grams
I Glass 2 grams
SiO2 74% by weight
A1203 1.0% by weight
Na20 16.5% by weight
CaO 5.0% by weight
MgO 3.5~ by weight
Silicone Oil 1.5 milliliters
. . .
2~
/~S3Yo8
- - ~PO-SITION VI
Aluminum powder (-20 microns) 1.6 grams
Glass 2.4 grams
SiO2 65.1% by weight
A12O3 13.3% by weight
Na20 6.07% by weight
CaO 1.37% by weight
MgO 0.92% by weight
K2O 9.78% by weight
SnO2 0.05% by weight
Li2o 1.01% by weight
Fe2O3 0.015% by weight
Silicone Oil 2.0 milliliters
In separate operations, the compositions are applied
to a clean metal core or substrate of non-precious metal alloy
of the following composition in weight percent:
71.3% nickel; 19.1% chromium; 4.6% silicon; 3.7% molybdenum:
and 1.3% boron and is the subject matter of Canadian applica-
tion No. 244,988, filed January 30, 1976.
The coated metal is baked in the manner described
in Example I. Thereafte~, the coated metal is faced with por-
celain employing the same porcelains and procedures described
in Example I.
~he samples show good adhesion of porcelain to metal.
2~
1053408
CER 15
EXAMPLE VII
In a similar manner, a bonding agent is prepared
by mixing together 2 grams of aluminum powder (20 microns),
2 grams of glass powder (same oxide content as in Composition
I) and a sufficient amount (1.5 -2.5 milliliters) of silicone
oil (GE #69) to produce a thick easily paintable composition.
The composition is employed to bond porcelain to slugs
of a nickel-chromium alloy of the same composition as
described in Example I.
The 61ugs are prepared for testing in a manner similar
to that described in Example II except as follows:
Ten pairs of slugs are employed without modifying the
surfaces of the alloy before applying the bonding agent (As
received surface). In ten other pa~rs of slugs, the surfaces
are ground with a diamond wheel prior to applying the bonding
agent (Ground surface). After application of the bonding
agent, the slugs are baked, cleaned, coated with porcelain
and fired in a manner similar to that previously described.
The slugs are then tested in the Instron testing instru-
ment for three-point loading as previously described. The
results are as follows:
As received surface 12,205 p.s.i.
Ground surface 10,364 p.s.i.
26
