July 15, 1958 J. W.

LONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filled Dec. 15, 1949 8 Sheets-Sheet i

AERA, CCAL, SYBO, CRSA, CLASS CHECA, GRA

(Shoenflies System) -
Beryl 3BeO'Al2O3 6SiO D6h
2 Commercial
bullite 3.Alao 2SiO2 Cornereia
Potassium Feldsper Ko'Al2936Sio Technee
l Spodunene Li20 Al2O3 4S10. Comercial
ioniu zno"ZrO2SiO2 Technical
girirconium 2rosio Technical
Berium airconate Bao'ZrO. Techniel
Si Technical
Cooercial
Crs Cornercial
2. A
Fe

Cobalt Orde Technical

Cuprous Oride Technical
Chronic Oxide Technical

2B Iron Odds Technical

tagnetito) .
Iron Oxide Convercial
(Rematite)
langanous Oxide Countercial
Nickel Oxide Technical

John 4 Zongy

33 auce 7.4nr-2a,
(towed
 July 15, 1958 J. V. LONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filled Dec. 15, 1949 8 Sheets-Sheet 2

GROUP MATERIAL CHEMICAL, SYBOL CRISTA, CLASS CHEICA GRAD

(Shoenflies System)
Zirconium Dioxide ZrO2 O Technical
fluxinuin Oxide A120 o Technical
Titan Dioxide Technical

2rco Commercial
Tin Oxide (Stennie) Technical
Beryllium oido Coamercial
Silicon Carbide Commercial

Zinc Oxide Technical

Silica (Quartz) Commercial

Boron Oxide Technical

Phoephoric Pentoxide Technical

Lithium Fluoride Technical

Sodium Fluoride Teehnica
Potassita fluoride Teehnical
Calcium Fluoride Technica
Magnesium Oxide Technical
Calcium Oxide Technical
Molybdenua Dioxide Techical

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nventot
John M. Long

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 July 15, 1958 J. W. LONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filed Dec. 15, 1949 8. Sheets-Sheet 3

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 July 15, 1958 J. v. Long 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filed Dec. 15, 1949 8 Sheets-Sheet 4
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 July 15, 1958 J. V. LONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filed Dec. 15, 1949 8 Sheets-Sheet 5
Y P C A

COATING
NBER

AIS OO S5 120 hours et l60OF

AS OO S8 -- S29 72 hours at 1600°F
AISI 1020 STEEL S8 -- S2. A. 72 hours at 1600°F
AISI 1010 STEEL S45 72 hours at 1600°F
AISI 1030 STEEL, S30 - S3l 72 hours at 1700'F
AISI 130 STEEL S30 -- S3. 72 hours at 1700°F
AISI 347 STEFL, Ski -- S2 72 hours at 1700°F
AISI 347 STEEL S38 72 hours at 180of
AISI 310 STEEL, SAl -- S43 72 hours at 170of
AISI 314 STEEL Sal + S43 72 hours at 18COf
S9
AISI 3A as { S28
72 hours at 1850°F
Inconel s39 + s32 72 hours at 180of
55 (STELLITE) S3 72 hours at 1850'F
S-816 (Allegheny- S3A 72 hours at 1850'F
Ludlum)
- S44.
Witallium l80OF

Hastelloy B { 72 hours at 1850°F

* Explanation of Coating Combinations
S8 - S29 indicates double coat, single firing:
i.e., S8 applied, then S29 applied, then fired
S9 indicates two single coats, each fired separately,
i.e., S9 applied and fired,
then S28 applied and fired

Afg. 3 nuovo
John 4 Long

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July 15, 1958 J. W. LONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filled Dec. 15, 1949 8 Sheets-Sheet 6

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July 15, 1958 J. V. ONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filed Dec. 15, 1949 8 Sheets-Sheet 7

Afg. 8

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John M. Long
July 15, 1958 J. V. LONG 2,843,507
CERAMIC COATINGS AND METHODS OF FORMULATION
Original Filled Dec. 15, l949 8 Sheets-Sheet 8

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John M. Long

eltowed
United States Patent Office 2,843,507
Fatented July 15, 1958

partment and Tank Automotive Center, the National

2,843,507 Advisory Sommittee for Aeronautics, and the Porcelain
Enamel Institute. These organizations have investigated
CERAMC COATINGS AND METHODS OF means of providing oxidation and corrosion resistance for
FORMULATION metals and alloys by utilizing known principles of enamel
John V. Long, San Diego, Calif., assignor to Solar. Air formulation to extend the temperature range of previously
craft Company, San Diego, Calif., a corporation of developed enamels for low temperature applications.
California In spite of the vast amount of research and develop
Continuation of application Serial No. 133,945, Decem ment, including the extensive Government direct and sub
ber 15, 1949. This application August 31, 1953, Serial 10 sidized research carried on in this field, the prior com
No. 377,381 mercial enamel and ceramic coatings for metals have in
general required the use of separate base coats to secure
18 Claims. (C. 117-129) adherence to the metal to be coated, and outer coatings to
secure reasonable protective properties, and require com
The present discovery and invention relate to improved 5 plex formulations with comparatively thick applications,
compositions of matter and methods of their production, and the finished coatings have relatively poor adherence,
and more particularly to new protective layers and coat poor protective qualities particularly at elevated tempera
ings of the ceramic or enamel type for metals and alloys; tures, and poor thermal and mechanical shock resistance.
said layers and coatings having qualities of thinness, ad In particular, a strong persistent demand by designers
herence, thermal and mechanical shock resistance, and 20 of lightweight, high power, high temperature equipment
latitude and simplicity of coating formulation, heretofore for coatings applied in very thin layers (in the range of
unattainable in prior ceramic and enamel coatings. .0005 to .003 of an inch in thickness) which have high
Historically the origin of the art of enameling and thermal and mechanical shock resistance, and which will
ceramic coating of metals is lost in antiquity. Examples provide corrosion and oxidation protection for extended
of enamel coated metal jewelry date back to the fourth periods of service life at temperatures above 1500. F. has
century B. C. For the past century commercial iron and not been met by the prior art. Various prior efforts and
sheet metal enameling for protective and ornamental pur failures to supply this demand even with the extensive
poses has been highly developed, and research in this government subsidized research are noted in the papers
field has been particularly active from the beginning of read at the Conference on Ceramic Materials for Appli
the present century, and rapidly accelerated in efforts to 30 cation to Aircraft Power Plants sponsored by the Head
meet the needs of the two world wars. quarters Air Materiel Command, Wright-Patterson Air
For a number of years the exhaust manifolds of cer Force Base, Dayton, Ohio, on May 27 and May 28, 1948.
tain automobile engines have been coated with the con Coatings applied in very thin layers are quite impor
ventional type of glossy porcelain enamel to prolong their tant, for example, on gas turbine blades in which distortion
lives. These were, however, unsatisfactory for airplane 5 of the air foil cannot be tolerated, in reduction of weight
exhaust manifolds which operated at temperatures of the of jet engine parts, and in coating extremely thin edges,
order of 1000 F.; and it accordingly became the prac all types of welds, and combinations of various metal
tice to make airplane exhaust manifolds of heat resistant thicknesses. Thinness is also a substantial factor in better
nickel-chrome alloys. adherence which eliminates cracking, chipping, spalling
Also since early in 1942, designers of high temperature 40 and damages done by flying ceramic particles which may
Systems, particularly jet engines, rockets, gas turbine be considerable in high speed gas turbines and the like
power, plants, heat exchangers, etc., have encountered when comparatively thick coatings are used.
serious materials problems, because available metals and Accordingly, a primary object of my invention is the
alloys lack corrosion and oxidation resistance in the provision of novel simplified methods of formulating and
temperature range above 1500 F. The military needs compounding protective compositions of matter which,
and rivalries requiring increased thermal efficiencies, and when applied in verythin layers to metals and their alloys,
prolongation of the life of such high temperature devices, have considerably improved thermal and mechanical
have created an additional urgent demand for better shock resistance, high oxidation and corrosion resistance
materials and/or methods by which currently used mate at very high temperatures, and other desirable properties
rials can be protected in such uses. A solution of these heretofore unattainable in protective ceramic and enamel
problems appeared to lie in developing high temperature coatings, and which provide those skilled in the ceramic
protective ceramic coatings with the required properties arts with wide latitude in selection of materials to produce
to increase corrosion and oxidation resistance, and to en desired properties in formulating or compounding im
hance metal stability at higher temperatures. In addition, proved portective layers for metals and alloys.
it appeared that ceramic coatings could be used on low Another object of my present invention is to provide
temperature alloys made of readily available materials, protective compositions of matter which may be simply
which normally lacked high temperature corrosion and formulated and which, when formed on or applied to the
oxidation resistance, to permit their substitution for surfaces of metals, such as iron, steel, molybdenum, nickel,
strategic materials. chromium, cobalt, tantalum, tungsten, etc., and their al
For some years past, intensive direct government and 60 loys, will provide verythin, impervious, highly refractory,
government subsidized development and private develop corrosion and oxidation resistant layers of surface com
ment of such coatings has been under way both in this positions which are tightly bonded to the base material,
country and abroad. In this country such developments and are of exceptional mechanical and thermal shock
have been particularly active at the United States National resistance, and which do not materially, increase the
Bureau of Standards, the department of Ceramic Engin 65 weight of the protected objects, are highly useful at nor
eering of the University of Illinois, the Ohio State Uni mal temperatures, and provide prolonged life at elevated
versity Research Foundation, Armour Research Founda temperatures.
tion of the Illinois Institute of Technology, Rutgers Uni A further object of my invention is to provide novel
versity, Battelle Memorial Institute, New York State compositions of matter which in very thin layers give
College of Ceramics and others, in co-operation with the 70 substantial protection to materials of the foregoing types
United States Air Materiel Command, United States for extended periods of service life against oxidation and
Naval Research, the United States Army Ordnance de corrosion above 1500 F.
 2,843,507
9 4
Another object of my invention is to provide protec ing formulated and applied thereto according to the
tive compositions of simplified formulation, and pro principles of the present invention. These micrographs
ducible with simplified manufacturing controls, which may were made with plane-polarized illumination since, under
be formed on the surfaces of the material to be protected light the ceramic coating, being somewhat translucent
in thicknesses of the order of .0005 to .003 of an inch, would record dimly or not at all. Due to the polarized
and which will adhere to extremely thin and raw metal light, the metal in each case appears quite dark and the
and alloy edges, to all types of welds, and to combina etched areas of the metal and grain boundaries are exag
tions of various metal thicknesses, without cracking, chip gerated as are dirt, grease, and other foreign matter.
ping or spalling under severe mechanical and thermal Figure 4 is a 100 power magnification and shows,
shock. 10 from top to bottom, the Bakelite (used to hold the speci
It is a further object of the invention to provide a novel men), the ceramic layer, areas of diffusion at the ceramic
process for protectively coating metallic surfaces involv metal interface, and the base metal with the dark areas
ing the selection of coating material ingredients that all being matrix and the light areas natural inclusions (sul
have substantially the same crystal structure and which phides, silicates, etc.). In this as well as the remaining
when combined and fired upon a metallic surface develop figures, the Bakelite appearing at the top of each photo
at the metallic surface a final crystal structure that is graph contains light splotches which are ceramic and/or
substantially the same as that of the normal surface layer abrasive particles embedded therein during the grinding
of the metal. - and polishing of the specimen.
A further object of the invention is to provide a novel in Figure 5 (250X) the interface between the metal
process for coating metallic surfaces wherein materials 20 base and ceramic layer shows a fairly continuous dark
that possess the same or very nearly the same crystal line, separating the ceramic layer from the interdiffusion
structure as the oxides that are normally formed on such Zone. The light areas appearing in the metal base are
metallic surfaces are thermally bonded to the surfaces. caused by etched pits. Because the ceramic is harder
Other objects of my invention will appear from the than the metal, it is difficult to polish the specimens to
following disclosure of preferred embodiments thereof an absolutely flat plane and, therefore, in some pictures
and from the appended claims. Referring to the draw either the metal or the ceramic is slightly out of focus.
Ings: In this particular photograph, the metal is sufficiently out
Figures 1 and A comprise a tabulation of metals and of focus to exaggerate the etched pits.
ceramic raw materials which I have so far found available Figure 6 (250X) is one of the better showings of the
for use in the formulation of my improved protective 30 diffusion areas. The grain boundaries are clearly out
compositions, and are illustrative of the types and char lined because the metal is very slightly out of focus.
acteristics of the materials that may be used in carrying As a hypothetical point, if, before this specimen was
out my invention and discovery. This tabulation indi etched, the layer of ceramic could have been put on the
cates materials, chemical symbol, chemical grade, and 35 metal area, then the etch cycle completed, and the ceramic
crystal class of such materials, where presently known or removed before this micrograph was taken, the grain
readily available in the literature, according to Shoenflies boundaries would not be visible because no etching action
system of designation. Materials are listed generally could have taken place through the ceramic coating.
according to their functions in several groups as follows: In Figure 7 (100X) is also a good showing of the
Group I.-Complex minerals which increase stability diffusion layer joining the ceramic coat and metal base.
and durability of coatings and comprised in general of in Figure 8 (100X) the metal is slightly out of focus
complex compounds made up of materials listed in and therefore the inner metallic compounds are exagger
Groups 2-5, inclusive. ated but the ceramic coating shows quite clearly.
Group 2A.-Metals which have been used in high Figure 9 (100X), the ceramic is slightly out of focus
temperature alloys which increase adherence and thermal while the metal is well in focus with good grain boundary
shock resistance of my improved compositions. delineation. As a result the diffusion area is not too
Group 2B.-Oxides of metals which have been used in obvious. It is to be understood, however, that while as
high temperature alloys which increase adherence and in this photograph, the laminar zone of interdiffusion
thermal shock resistance of my improved compositions. between metal and ceramic does not record obviously
Group 3.-Oxides which may be classed as partial 50 in all the photographs as compared, for example with
glass network formers or which increase the durability Figure 6, this interdiffusion existed in all specimens
of glasses. tested.
Group 4.-Oxides which are definitely known to form Figure 10 (100X) shows, as can be seen by the "spotty"
glasses. appearance of the metal, one of the super alloys such as
Group 5.-Materials which produce fluxing action or N-155 and S-816, the interdiffusion zone being clearly
are so-called glass modifiers. delineated at the interface although not so well defined as
Figures 2 and 2A comprise a tabulation of some in Figure 6. ..
Specific examples of typical protective compositions form In Figure 11 as in Figure 9 the area of interdiffusion
ulated from materials of the various groups of Figure 1 is not particularly well defined. However, both coat and
in accordance with my invention and discovery, num 60 metal are in excellent focus and the interface is particu
bered consecutively for convenient reference hereinafter. larly clear.
Amounts of constituents are given by relative weight. AS best appears in Figure 6, it will be seen that the
Figure 3 is a tabulation of illustrative examples of my fired coatings of my invention form a layer bonded to
best coating applications which have so far been formu the base metal by a laminar zone of interdiffusion of the
lated, applied and tested on the various listed metals ceramic and base materials. It has been found that the
and alloys, with firing temperatures and times, and A. M. interdiffused layer at the interface remains even when
C. test data. the primary or external coating has been spalled off and
Figures 4 to 11 are photomicrographs of typical com that said interdiffused layer provides a substantial degree
positions formed on base materials of AISI steel alloys of protection for the base material. Thus it will be ap
1010, 347, 310, 314; Inconel; (Vitallium); and the Alle 70 preciated that a coated base is composed of three layers,
gheny Ludlum cobalt-chromium-nickel alley known under namely, a first or structural layer consisting entirely of
the designation S-816. the base metal; a second or outer layer which is purely
Figures 4 to 11, inclusive, of the drawings are repro ceramic in nature, vitreous in appearance and crystalline
ductions of actual photomicrographs of sections through or cryptocrystalline in structure; and, at the interface
Specimens comprising a metal base having a ceramic coat 75 of the base metal and the coating, a third lamination con
 2,843,507
5 6
sisting of interdiffused crystals of base and coating ma crystals with atomic spacings the same, or nearly the
terials. same, as that along the crystal edges of the base mate
In other words a bond between the metal and coating rials. And that binding of the protective layer to the
is achieved by means of atomic lattice interfitting be basematerial is due to the lattice fit through the residual
tween the crystals thereof, the third lamination being in valence selectrons or a rapid exchange of the electrons
fact a combined bonding layer and secondary protective between the atoms of the protective layer and the free
layer. electrons in the base material. It is also my theory that
The basic concept of my invention comprises the dis electrostatic attraction may increase the bonding energy
covery that it is possible to methodically, accurately and but that the union between my improved protective layer
predictably select ingredients to be combined and fired in O and the base material is more than likely somewhere
thin layers upon metallic surfaces, which combinations between lienic and metallic, and consequently a homo
of ingredients develop in the final thermally bonded polar or valence bond.
layer a crystalline or crypto-crystalline structure that is In any event, in accordance with my discovery and
optimum for combination with the metallic Surface. My invention, produce new outer protective layers on the
understanding is that there is developed in the fired layer base materials having various new and improved prop
a crystal or like structure of such atomic space grouping crities not present in prior protective coatings, including
as to have good lattice interfit with the crystal structure superior corrosion, mechanical and thermal shock resist
of the metallic surface. I have ascertained that any of ance, and also superior bonding to and union with the
a large number of ingredients are available for substitu base material. In many instances my improved pro
tion in the combination in place of any of the ingredients, 2O. tective layers may be hammered without chipping or
the substitute ingredients having, similar crystal Space spalling.
groups, so that ingredients of the layer to be applied to in carrying out my invention, I have discovered that
a given metallic surface may be selected by those skilled the metal and ceramic constituents used to formulate my
in the ceramic arts and put together on the foregoing improved coatings may be classified in general under the
basis with due consideration for all special requirements first three of the six systems of crystallization outlined
of the final product to produce layers that are known to in W. E. Ford's fourth edition of Dana's Textbook of
have maximum adherence and optimum protective values. hiineralogy. These include the isometric, tetragonal and
In carrying out the invention according to its preferred hexagonal systems. Also, that the majority of the avail
embodiment, I strive to replace the normal oxide coating able materials fall in the normal class of each system
of the metallic surface with a protective layer of Supe which contains crystals exhibiting the highest degree of
rior properties. Hence the preferred technique is to Symmetry. Some exceptions are apparent for materials
select those ingredients which possess the crystal space in the hexagonal system where materials lower in grade
grouping the same or nearly the same as the normal of symmetry have been effectively used. These include
oxides, and which also are selected for the type of pro some classed as hemimorphic, rhombohedral and trape
tection desired. The combination of ingredients is com zohedral. Materials in the orthorhombic and monoclinic
pleted by this process of selection and then fired upon systems have also been used as constituents to produce
the surface. If different properties are required for cer satisfactory, compositions, but in all such cases the pro
tain conditions of operation, ingredients of appropriate tective quality and life of the coating is reduced below
properties may be substituted on the foregoing basis of those attainable in my better-coatings. The space groups
40 of the materials used to formulate my improved protec
related crystal structure.
With regard to the following disclosure, my present tive compositions as indicated by the symbols of the
improved methods of formulation and my improved com Shoenflies system in the X-Ray Crystallographic Data
positions are formed on my discovery that by utilization section of the Handbook of Chemistry and Physics, 31st
of the ceramic materials outlined in Figures 1 and 1A, edition, 1949, are as follows:
crystalline or crypto-crystalline protective compositions
are developed on firing which have good lattice fit be O4. O5 Oh,7 OD,4. DE,9 Dh,
2 4. f
63 Da, D,4. Civ,
4.
C19
tween the protective surface layer and the metal or alloy
to be protected, which are novel and have 'greatly im and
proved protective qualities on the surfaces of the base 3
materials, and which have highly useful, new and im Ch.
proved properties. For example, in treating oxidation Space groups for many complex minerals classified in
resistant metals and alloys, I can form very thin surface Figures 1 and 1A according to function in Group 1 and
layers of new protective materials having considerably Space groups for Some glass forming network materials
improved refractoriness and oxidation resistance com 55 in functional Group 4 are presently unknown or not
pared to the normal oxide films on such metals and alloys. readily available in published literature but it is believed
My improved compositions may be combinations with that they can be identified with the crystallographic sys
such normal protective films to produce better ones, or tems and classes as outlined.
may replace them, and can be applied as protective layers in applying my discovery and invention to the formu
or films on base materials whose normal oxide coatings 60 lation and production of my basic improved protective
do not inhibit oxidation. compositions, materials are usually selected from the
In carrying out my invention, utilize mixtures of first two or three groups tabulated in Figures 1 and 1A,
materials tabulated by groups according to function in applied to the metal or alloy to be coated and fired.
Figures 1 and 1A and selected from the groups depend Alterations and Substitutions based on tests are then
ing upon the coating characteristics desired. These se made, using, if necessary, other materials selected from
lected materials are mixed in combinations, which when any of the five groups on the basis of similar crystal
applied in thin layers to the metallic base materials to space grouping, until the optimum protective layer for
be protected and properly fired as hereinafter set forth the particular purpose is obtained. Excellent protection
in detail, develop crystal or crypto-crystalline structures has been obtained with layers formulated with materials
having one or more axes comparable to the crystal axes 70 from two or more groups because tests indicate that all
of the base materials. As a result of extensive tests mixtures apparently combine upon firing to develop an
and experience with my improved compositions and their atomic Spacing, along an edge of the crystal lattice, the
new and Superior properties, I have developed a simpli sane, or nearly the same, as that along the edge of the
fied theory, that certain materials including those listed crystal of the metal or alloy being coated.
combine - on firing to form solid solutions containing 75 Selection of materials used in coatings is in general
 2,843,507
7 8
governed by their functions outlined above in the brief with my invention may consist of the following materials
description of the drawings, the environment in which in parts by weight:
protection is required, and the type of coating desired.
For example, to increase adherence and thermal shock
resistance of my protective compositions, I add a mate
rial selected from Groups 2A and 2B. To increase sta
bility and durability I add specific ceramic compounds
from Group 1 or materials from Group 3. To obtain
more vitreous or impervious coatings I add materials These materials are mixed with a suitable quantity of
from Groups 4 and 5. I can also control the properties O water and a suspension or thickening agent, such as
of coatings by selecting and adding materials from any citric acid, Ca(NO), methyl cellulose, or the sodium
group to produce chemical resistance; coatings which salt of polymerized d-mannuronic acid known as Kelgin
do not attack the base metal or oxidation and corrosion LV, and milled to a fineness suitable for spraying,
resistant coatings to fit most engineering requirements. dipping, slushing or brushing, depending upon the appli
When necessary or desirable, I limit oxide formation cation and the thickness of the coating required or de
on the base material by controlling the furnace firing sired. The resulting slip is then applied to the prepared
atmosphere. metal, for example, A. I. S. I. (S. A. E.) No. 1010 steel
In the formulation of protective layers having speci and fired at a temperature of about 2200 F. for about
fied properties for specific materials, in accordance with 20 10 minutes. The suspension agent used is not critical
my invention, samples of the material to be protected and may be any water soluble dispersing agent known
may be used in sizes depending upon material avail to those versed in the ceramic arts which produce hard,
ability. Samples 2 x 4 inches, 1/2 x 3 inches and /2 x 1 tough and flexible films on drying. Firing time and tem
inch are ordinarily used for metals and alloys. The peratures vary and depend upon size of sample, gauge, etc.
materials to be used in the formulation of the protective A controlled atmosphere firing of the coating results
layer are selected according to function and crystal space in a Smoother, better coating than otherwise and for
grouping from Figures 1A and 1B of the drawings. No some applications is quite important. For control, de
special preparation such as fritting is required. The mix pending upon the base material coated, a slightly oxidiz
ture need only be ground to the fineness required. ing, neutral, or reducing atmosphere may be used or the
After mixing, water and a suspension agent are added, furnace atmosphere diluted with an inert gas. In some
and the mixture milled to produce a slip of the fineness cases, better results are obtained in ordinary furnaces
desired. Most of my formulations require only about by using a suitable metal container or box to enclose
one hour of milling, although the time may be more the coated part and flushing the box with inert gas dur
or less, depending upon the ingredients and their hard ing firing. Although any inert gas appears to give satis
ness. After milling, the slip is adjusted by adding or 3. 5 factory results for control purposes, I prefer to use nitro
removing water to provide a viscosity suitable for dipping, gen because of ready avaliability and lower cost. While
spraying, or slushing onto the base material. Applica the end result is a combination of coating formula and
tion by spraying is preferred because this method pre atmosphere, the firing technique or coating composition
vents beading and permits more uniform thickness. No may be easily altered to fit practically all furnace condi
special preparation of the metal or alloy to be protected 43 tions by those skilled in the art, and permits satisfactory
is required, except that it be free of dirt, oil and excess coatings to be applied to any of the rapidly oxidizable
scale, a condition readily obtained by sandblasting to metals without the coatings spalling, fishscaling or blis
mention one of several methods known to those skilled tering. With proper control, the thickness of normal met
in the art. al or alloy oxides may be limited to provide a better,
After coating, the samples are furnace or air dried more uniform surface bond. For rapidly oxidizable
and then fired for a period of time and temperature metals, such as molybdenum, iron, "Hastelloy B" (a Hay
dependent upon the base material and the mixture used nes Stellite Company alloy whose nominal composition
and determined by experiment. Coatings are then is Ni 65.1%, Mo 28.6%, Fe 4.7%, C .05%, Min 59%,
checked for adherence and thermal shock resistance and and Si .19%), etc., the normal oxide is kept to a mini
tested. Mechanical bending and hammering are used to mum during the firing, otherwise the coating will spall or
check adherence and water quenching to room tempera flux off.
ture from 1600 F. to 2000 F. to determine thermal The above formula is, of course, merely illustrative
shock resistance. Compositions which exhibit desired and the ranges and ceramic materials may be varied
properties under such treatment are then tested, using widely. For example, oxidation tests with iron as the base
the tentative Air Materiel Command ceramic coating test material at 1600 F. for extended periods show that
which comprises 72 hours of alternate heating and air satisfactory oxidation resistance and adherence is ob
quenching and soaking at contemplated operating tem tained using coating S-5 throughout the following ranges
peratures. Included are a cyclic heating period for fifteen by weight:
minutes followed by an air quench every half hour for
an eight hour period and then a sixteen hour soak re 60 Beryl Si SiC
peated each day until seventy-two hours have been com
pleted. 5-50% 40-95% 0-35%,
All compositions listed in the formula chart, Figures
2A and 2B, are useful in differing applications, and will
pass at least five hours of this test. Additional protec 65 As will be seen from the charts, Figures 1, 1A, 2 and
tive life and other desired characteristics are obtained 2A, certain Substitutions may be made in this formula,
by Substitution of materials in specific basic formulae provided the crystal Space groups are the same, or nearly
and repeating the processing of coating, firing and test the same, preferably those in the same class or those that
ing in a manner well known to those skilled in the art, exhibit the next lowest order of symmetry. As an ex
until compositions are determined, which will give the 70
ample, nickelous oxide or cobaltic oxide may be sub
desired life and characteristics required for a specific stituted for silicon, and zinc oxide or beryllium oxide
application. may be substituted for silicon carbide. Since the avail
By way of specific example, composition S-5 of Figure able crystalline space group and crystallographic data
2 is an excellent basic mixture for the protection of of complex ceramic compound similar to beryl is limited,
metals and alloys, and when formulated in accordance 75
the full range of substitute materials cannot presently be
Selected on the basis of crystal space lattice, but I have
 2,848,507
9 10
determined by experiment and test that mullite As shown by the charts, LiF and NaF belong in the
(3Al3O3.2SiO2), potassium feldspar (KO.AlO.6SiO), 5
Zinc zirconium silicate (ZrO.AroSiO) and others O.
list in the complex mineral Group 1, Figure 1, may be 5 crystal space group, but I have found by test that ce
lSed.
I have also determined that the wide range of ceramic ramics with crystal space group
Substitutions permits some contamination and variations 4.
in the grades of the materials to be used without resultant
deterioration of coating. For example, thin, Strong,
D
tightly adhering, thermal shock resistant compositions 0 may also be added or substituted therefor. This group
have been developed by using reagent, chemically pure, includes MoC, which appears to react in a manner similar
technical and commercial grade materials. This latitude to modifiers, and produce more vitreous compositions.
does much to simplify the control and formulation of my My improved basic and vitreous compositions are ex
improved protective compositions for specific uses. In tremely flexible and may be applied and fired (1) direct
addition, byproper selection of materials, those who are 15 ly on metals and their alloys, (2) successively as base
familiar with the ceramic art can alter firing times and and top coating, (3) together, or (4) may be mixed to
temperatures to meet specific conditions. For the com gether and applied and fired. Typical examples of these
positions disclosed herein, it has been determined that the combinations follow:
firing time will vary from two to twenty minutes and fir Coating S-12. (Figure 2) consists essentially of the
ing temperature from 1500 F. to 2600°F, as indicated 20 following parts by weight:
for some compositions in the tabulation of Figure 3.
The wide range of acceptable materials permits my Beryl Si Al2O3 BeO TiO2 .
basic protective compositions to be altered to develop
more or less refractoriness, more vitreous impervious 25 8 . 4 8 2 6.
Surfaces, and resistance to chemical attack by the proper
Selection of ceramic materials. I have also discovered
that my improved basic compositions may be combined and coating S-28 (Figure 2A) consists essentially of the
following parts by weight:
and/or fired in various combinations.
For example, I have discovered that a more impervious
composition than coating S-5 results by the addition of 30 Beryl ZrO. SiO B;03 BeO LiF NaF
one part by weight of titanium dioxide, which does not
detract from the basic coating qualities. Such a more 8 2. 8 2 2 2
impervious composition (S-7 of Figure 2) by way of ex
ample consists essentially of the following parts by weight; 35 (1) Both may be applied and fired directly on metals and
their alloys to produce satisfactory protection composi
tions (2) or S-12 may be applied and fired as a base, and
SiC. then S-28 applied and fired as a top coating, (3) or S-12
may be applied and then S-28 applied and both fired to
1 gether, (4) or S-12 may be mixed with S-28 to produce
40 coating S-40 consisting essentially of the following parts
These materials are mixed, applied and fired in the by weight:
same manner as the basic ceramic mixture, except that Beryl si Zrosio, B.O. Also, BeOTio, LiF NaF.
firings for five minutes at a temperature of 2200 F is
required. 16 4. 2 8 2 8 4. 6. 1 2
I have also found that tin oxide or zircon may be sub
stituted for the titanium dioxide since they are of the which is applied and fired as a single coating.
same crystal class. I have also discovered that many These examples are merely illustrative and by no means
other additions of refractory materials or metals may be limit the application, mixing and firing technique to that
made in or to the formula. These include tantalum 50
1nitride, chromium, cobalt, or combinations of metals described.
and ceramics. In the substitution or addition of metals, terials The basic concept and wide range of ceramic ma-.
I have determined that the best results are obtained if and compounds, which can be used in coating
the metal added forms an oxide of high melting point of : formulation, permits more refractory single protecting
compositions to be mixed or highly refractory top com
suitable crystal space group, that will fit the composition. 55 positions to be added in a manner somewhat similar to
A more-vitreous coating can be obtained by includ
ing known glass-network formers of proper crystal-space: that used for vitreous coatings. For example, the refrac
group and the addition of a flux or so-called glass modifier: toriness of coating. S-8 which consists essentially of the
of proper crystal-space group. Tests show that if a coat following parts by, weight:
ing formula is compounded to included SIOPOs, or 60
B2O3, along with other ceramics selected according to Beryl Coso, BeO TiO2
my invention and discovery and lithium fluoride, sodium
fluoride, or potassium fluoride are added, a glassy or 12 6 6 6
vitreous surface is formed. A typical example is coating
S-28 (Figure 2A) which consists essentially of the fol 65
lowing parts by weight: may be increased by adding a top layer. of coating S-8TI
which consists essentially of the following parts by weight:
Beryl ZrO2 SiO2 B2O3,
ZrOs. SIO Also, Beo
5 2. 10.5

These materials are mixed, applied and fired in the These coatings may be applied and fired using the
same manner as the basic ceramic mixture, and fired for 75 same technique as that for developing more vitreous
five minutes at a temperature of 2150 F.
 2,848,507
11. 12
coatings, except that some highly refractory top coatings positions of Matter and Methods of Their Production,
cannot be fired directly upon the metal or alloy. now abandoned.
The chemical resistance of the materials that may be Certain terminology used in the claims is defined as
used in coating formulation also permits formulation of follows: (1) The expression in the claims of "materials
compositions in accordance with my invention with added in Group 1,' and like expressions relating to Groups 2,
chemical resistance and without deterioration in basic 3, 4 and 5, refer respectively to all the materials listed
composition properties. For example, by incorporating in corresponding Groups 1, 2, 3, 4 and 5 in Figures 1 and
only acid resistant materials in the coating, high tem 1-A of the drawings in this application (and such equiva
perature, acid resistant compositions may be fired on lents thereof as may fairly fall within applicant's dis
metals and alloys to provide base material protection. 10 closure under the patent law doctrine of equivalents).
My improved compositions may also be fritted in a (2) The word "essential' used in the third last clause
manner similar to that used in the enamel art, by mix of process claims numbers 12-17 is not intended to in
ing and smelting at temperatures from 1700 F. to 3000 clude mill additions.
F. until maturity is indicated by the ability to draw a The terms "fire bonded' and “firing' used in the
smooth glass thread from the batch. The smelt is then 5 claims are not limited to heating the base metal and ce
quenched by pouring it into water and then it is dry or ramic coating through the direct application of fire to
wet ground to the fineness desired for spraying, dipping bond the coating to the base metal, but include also
or slushing. This process imparts more uniformity and indirect heating, as for example, heating in a furnace or
higher refractoriness to some coatings, but is seldom the like.
required and is described to illustrate the wide flexible 20 The invention may be embodied in other specific forms
range of inherent mixture properties when the coatings without departing from the spirit or essential character
are formulated by selection of materials in accordance istics thereof. The present embodiments are therefore
with my invention and discovery. to be considered in all respects as illustrative and not
All of the numerous formulations in accordance with restrictive, the scope of the invention being indicated by
my invention and discovery so far tested give improved 25 the appended claims rather than by the foregoing descrip
protective results on all metals and alloys so far tried. tion, and all changes which come within the meaning
Lack of time and facilities have prevented the testing of and range of equivalency of the claims are therefore in
all available metals and alloys with my protective coat tended to be embraced therein.
ings. However, tests conducted over the past several What is claimed and desired to be secured by United
years show that by the proper selection of materials in 30 States Letters Patent is:
accordance with my invention and discovery, protective 1. An article of manufacture comprising a metallic
layers may be speedily formulated and fired on metals body having a crystalline structure, and a ceramic coating
and alloys to meet the most exacting requirements. To having a continuous surface consisting essentially of a
date, layers of protective composition have been pro crystalline or crypto-crystalline structure fire bonded on
duced for truck exhaust manifolds, burner cups, 35 said body, said coating having a crystalline interlocked
gas turbine combustion chamber liners, transition liners, permanent bond with said metallic body.
nozzle diaphragms, gas turbine and compressor blades, 2. An article of manufacture comprising: a metallic
rocket motors, and ramjets. Metals and alloys, includ body having a crystalline structure; a ceramic coating
ing molybdenum, tungsten, tantalum, S. A. E. steels 1010, having a continuous surface consisting essentially of a
1020, 4130, and 6323, Stainless steels Standard Type Nos. 40 crystalline or crypto-crystalline structure fire bonded on
403, 430, 501, 302, 321, 347, 310 and 314, Inconel said body; and a laminar zone of interdiffused particles
(Ni 80%, Cr 14%, Fe 6%), Vitallium (Cr 25%, Co of base metal and ceramic coating at the interface be
69%, Mo. 6%, C.24%) and Hastelloy B (Ni 65.1%, tween said coating and body.
Mo 28.6%, Fe 4.7%, C.05%, Mn.59%, Si.19%) have 45 3. An article of manufacture comprising: a metallic
all been successfully protected by improved composi body having a crystalline structure with at least its princi
tions, and the experience so far had with the foregoing pal constituent having unit cells of the cubic and hexag
wide variety of metals, alloys and articles subjected to onal classes; a ceramic coating having a continuous sur
very high temperatures indicates that satisfactory pro face consisting essentially of a crystalline or crypto
tecting composition for many other metals, alloys and crystalline structure fire bonded to said body, said coating
Services can be formulated in accordance with my meth 50 consisting of at least two materials having a crystal struc
ods herein disclosed. Also by my invention tightly ad ture of the cubic, hexagonal and tetragonal classes; and
hering, thermal shock resistant, vitreous protective sur a laminar zone of interdiffused crystals of base metal and
face layers may be produced on carbon, graphite, titanium ceramic coating at the interface between said ceramic
carbide, silicon carbide and the like. coating and metallic body.
A partial list of the base materials, compositions used, 55
4. An article of manufacture comprising: a metallic
firing times and temperatures, composition thicknesses, body having a crystalline structure; a ceramic coating hav
and Air Materiel Command (A. M. C.) data is given ing a continuous surface consisting essentially of a crystal
in the tabulation of Figure 3 of the drawings. line or crypto-crystalline structure fire bonded to said
It will accordingly be seen that materials with the fore body, said coating consisting of at least two materials
going properties, selected and applied to the base mate each from the group consiting of those having the space
60
rials in accordance with my invention, combine to form groupings of
thin, flexible, tightly adhering, protective layers that ma
terially extend the normal life of metals or alloys at 4 5 7 9 4. 2 6 6 4 r4 19
temperatures, and in corrosion and oxidation environ O, O, O OE, D, 6hy 3h 13d D, Civ, C
ments which produce rapid failure of the unprotected base 65 and
material, and open vast new possibilities of mechanical
design and improvement in high temperature equipment. C,
The best of these compositions are applied in very thin
layers of the order of .0005 to .003 of an inch, have a according to the Shoenflies system of identification; and
wider latitude of coating formulation, better adherence, 70 a laminar Zone of interdiffused crystals of base metal and
better mechanical and thermal shock resistance, and have ceramic coating at the interface between said ceramic
other desirable properties heretofore unobtainable with coating and metallic body.
prior enamels and ceramic coatings. 5. An article of manufacture comprising: a metallic
This application is a continuation of pending applica body having a crystalline structure; a ceramic coating hav
tion S. N. 133,045, filed December 15, 1949 for Com 75 ing a continuous surface consisting essentially of a crystal
 2,843,507
3. 14
line or crypto-crystalline structure fire bonded to said composition consisting essentially of about 6-20' parts
body, said coating consisting of at least two materials; by weight of one or more ingredients selected from the
one of said two materials, biing from one of Groups 1, materials in Group 1; about 0-24 parts by weight or more
2,3,4 and 5 of Figures 1 and 1-A, and the other of said ingredients selected from the materials in Group. 2; about
two materials being from one of the other 3 of said 4-22% parts by weight of one or more ingredients se
groups; and a laminar. Zone of interdiffused crystals of lected from the materials in Group 3; about 0-14 parts
base metal and ceramic coating at the interface between by weight of one or more ingredients selected from the
said ceramic coating and metallic body. materials in Group 4; and about 0-8 parts by weight of
6. An article of manufacture as defined in claim 1, one or more ingredients selected from the materials in
wherein the total thickness of said coating and laminar O Group 5; making a slip including said composition as
Zone is less than 0.003 of an inch. the essential component thereof; applying said slip to said
7. An article of manufacture comprising: a metallic base; and firing it to form a ceramic coating on said
body having a crystalline. structure; a ceramic coating base.
having a continuous surface consisting essentially of a 13. A process of ceramic coating a metallic base com
crystalline or crypto-crystalline structure fire bonded on 5 prising the steps of: compounding a protective coating
said body; and a laminar zone of interdiffused particles of composition comprising a mixture consisting essentially
base metal and ceramic coating at the interface between of about 8-20 parts by weight of one or more ingredients
said coating and body; said coating consisting principally selected from the materials in Group 1; about 3/8-6 parts
of one or more ingredients having a crystal structure of by weight of one or more ingredient sselected from the
the cubic, hexagonal and tetragonal classes with an atomic 20 materials in Group 2; about 5-22/2 parts by weight of
lattice spacing that is substantially an integer of the lattice one or more ingredients selected from the materials in
spacing of the principal material of said metal body. Group 3; about 2-10% parts by weight of one or more
8. An article of manufacture comprising: a metallic ingredients selected from the materials in Group 4; and
body having a crystalline structure with at least its princi about 1-7 parts by weight of one or more ingredients se
pal constituent having unit ceils of the cubic and hexag 25 lected from the materials in Group 5; making a slip in
onal classes; and a ceramic coating having a continuous cluding said composition as the essential component there
surface consisting essentially of a crystalline or crypto of; applying said slip to said base; and firing it to form
crystalline structure fire bonded to said body, said coat a ceramic coating on said base.
ing consisting of at least two materials having a crystal 14. A process of ceramic coating a metallic base com
structure of the cubic, hexagonal and tetragonal classes, 30 prising the steps of: compounding a protective coating
said coating having a crystalline interlocked bond with composition comprising a mixture consisting essentially
said metallic body. of about 6-12 parts by weight of one or more ingredients
9. A process of ceramic coating a metallic base that selected from the materials in Group 1; about 4-12 parts
has a crystalline structure with at least its principal con by weight of one or more ingredients selected from the
stituent having unit cells of the cubic and hexagonal 35 materials in Group 3; about 4-14 parts by weight of one
classes, comprising the steps of: compounding into a slip or more ingredients selected from the materials in Group
as principal ingredients thereof a mixture of at least two 4; and about 1-8 parts by weight of one or more in
materials each having a crystalline structure with unit gredients selected from the materials in Group 5; making
cells of the cubic, hexagonal and tetragonal classes; ap a slip including said composition as the essential com
plying said slip to said metallic base; and firing it until 40 ponent thereof; applying said slip to said base; and firing
a ceramic coating consisting essentially of a crystalline or it to form a ceramic coating on said base.
crypto-crystalline structure is permanently bonded there 15. A process of ceramic coating a metallic base com
O. prising the steps of: compounding a protective coating
10. A process of coating a metallic base with a ceramic composition comprising a mixture consisting essentially
coating of crystalline or crypto-crystalline structure com 45 of about 8 parts by weight of one or more ingredients
prising the steps of: compounding into a slip as principal selected from the materials in Group 1; about 4-24 parts
ingredients thereof a mixture of at least two materials, one by weight of one or more ingredients selected from the
of said materials being selected from one of Groups 1, 2, materials in Group 2; and about 4-16 parts by weight of
3, 4 and 5 in Figures 1 and 1-A and the other of said ma one or more ingredients selected from the materials in
terials being selected from one of the others of said groups; 50 Group 3; making a slip including said composition as
applying a layer of said slip to said metallic base; and fir the essential component thereof; applying said slip to said
ing it until a ceramic coating consisting essentially of a base; and firing it to form a ceramic coating on said base.
crystalline or crypto-crystaline structure is permanently 16. A process of ceramic coating a metallic base
bonded thereon. comprising the steps of: compounding a protective coat
11. A process of ceramic coating a metallic base that ing composition consisting essentially of about 8-12 parts
has a crystalline structure with at least its principal con by weight of one or more ingredients selected from the
stituent having unit cells of the cubic and hexagonal material in Group 1; about 2-8 parts by weight of one
classes, comprising the steps of: compounding into a slip
as principal ingredients thereof a mixture of at least two or more ingredients selected from the materials in Group
materials each having a crystalline structure with a space 60 2; about 16-23 parts by weight of one or more ingredi
lattice of the ents selected from the materials in Group 3; and about
8-14 parts by weight of one or more ingredients selected
O,4 O.5 OY,7 OE,9 D.,4. D.,
19 2
Dh, 6
D3d, D,4 Civ,
4. 19
Cy from the materials in Group 5; making slip including
said composition as the essential component thereof; ap
and 65 plying said slip to said base; and firing it to form a ceramic
3
Ch. coating on said base.
17. A process of ceramic coating a metallic base com
prising the steps of: compounding a protective coating
classes according to the Shoenflies system of identifica 70 composition consisting essentially of about 8 parts by
tion; applying said slip to said metallic base; and firing weight of one or more ingredients selected from the ma
it until a ceramic coating consisting essentially of crystal terials in Group 1; and about 20 parts by weight of one
line or crypto-crystalline structure is permanently bonded or more ingredients selected from the materials in
thereon. Group 3; making a slip including said composition as the
12. A process of ceramic coating a metallic base com 75 essential component thereof; applying said slip to said
prising the steps of: compounding a protective coating
 2,848,507
5 6
base; and firing it to form a ceramic coating on said References Cited in the file of this patent
base. UNITED STATES PATENTS
18. A protective coating composition comprising a
mixture consisting essentially of about 8-20 parts by 2,040,215 Rava ------------------ May 12, 1936
weight of one or more ingredients selected from the ma 2,300,454 Lucas ------------------ Nov. 3, 1942
terials in Group 1; about 3/8-6 parts by weight of one 2,311,039 Emery----------------- Feb. 16, 1943
or more ingredients selected from the materials in 2,321,763 McIntyre ------------- June 15, 1943
Group 2; about 5-22% parts by weight of one or more 2,337,521 Cooper --------------- Dec. 21, 1943
ingredients selected from the materials in Group 3; about 2,391,468 Long ----------------- Dec. 25, 1945
2-10% parts by weight of one or more ingredients se O 2,467,114 Deyrup --------------- Apr. 12, 1949
lected from the materials in Group 4; and about 1-7 2,475,469 Bennett et al. ----------- July 5, 1949
parts by weight of one or more ingredients selected from FOREIGN PATENTS
the materials in Group 5. 121,628 Australia ------------- June 24, 1956