CA1081057A - Spray bonding of nickel-aluminum and nickel-titanium alloys - Google Patents
Spray bonding of nickel-aluminum and nickel-titanium alloysInfo
- Publication number
- CA1081057A CA1081057A CA271,665A CA271665A CA1081057A CA 1081057 A CA1081057 A CA 1081057A CA 271665 A CA271665 A CA 271665A CA 1081057 A CA1081057 A CA 1081057A
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- nickel
- alloy
- aluminum
- substrate
- coating
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Abstract
ABSTRACT OF THE DISCLOSURE
An alloy of nickel and aluminum, which also may contain varying percentages of intermetallics, in the form of a wire or rod is sprayed in an electric arc spray gun to form a self-bonding coating on a smooth, clean substrate. Alternatively an alloy of nickel and titanium, which also may contain varying percentages of intermetallics, in the form of a wire may be similarly electric arc sprayed to effect a self-bonding coating on a substrate. The nickel aluminum alloy and possible inter-metallics or the nickel titanium alloy and possible inter-metallics are supplied as a wire feed to the electric arc spray gun, and when heated in the electric arc of the spray gun and sprayed onto a substrate will form a coating that has a high degree of tenacity to many metal substrates and also has a moderate degree of hardness, low Rc, high Rb. The self-bonding is attributed to the formation of superheated liquid in the arc process and the affinity of the superheated liquid to iron, nickel, aluminum, etc.
An alloy of nickel and aluminum, which also may contain varying percentages of intermetallics, in the form of a wire or rod is sprayed in an electric arc spray gun to form a self-bonding coating on a smooth, clean substrate. Alternatively an alloy of nickel and titanium, which also may contain varying percentages of intermetallics, in the form of a wire may be similarly electric arc sprayed to effect a self-bonding coating on a substrate. The nickel aluminum alloy and possible inter-metallics or the nickel titanium alloy and possible inter-metallics are supplied as a wire feed to the electric arc spray gun, and when heated in the electric arc of the spray gun and sprayed onto a substrate will form a coating that has a high degree of tenacity to many metal substrates and also has a moderate degree of hardness, low Rc, high Rb. The self-bonding is attributed to the formation of superheated liquid in the arc process and the affinity of the superheated liquid to iron, nickel, aluminum, etc.
Description
BACKGROUND OF HE INVENTION
; This invention relates to a method of electric arc spraying self-bonding materials and an article formulated by the same. More specifically, the invention relates to a thermal spraying of nickel aluminum alloys or nickel titanium alloys, which alloys may include varying percentages of intermetallics of nickel and aluminum or nickel and titanium, respectively, in wire form using an electric arc spray gun.
The use of thermal sprayed coatings has been widely accept-ed in recent years, for example, for protecting substrates for cry-ogenic or refractory purposes, for parts repair, for protection of a substrate from oxidizing or from other hostile environments, and for many other purposes. However, the search for new materials with which to spray and new techniques for spraying is continuing '1 in an effort to achieve better coatings befitting new applications ;' and time saving methods particularly to avoid preliminary base or substrate preparation and/or post coating and base treatment.
; Several types of thermal spraying guns are available in-cluding combustion flame spray guns, e.g., the oxy-fuel gas type, plasma arc spray guns and electric arc spray guns. Combustion flame spray guns require a source of fuel, such as acetylene, and oxygen ;
and the temperatures produced therein are usually relatively low and often incapable of spraying materials having melting points i exceeding 5,000F. Plasma arc spray guns are usually the most ex-pensive type and they produce much higher temperatures than the com-bustion type, e.g. up to approximately 30,000F. Furthermore, plasma arc spray guns require a source of inert gas, such as argon, ~ for creation of the plasma, and the gas flow rate and electric power - therefor require extremely accurate control for proper operation. ;~
.. ~ . ,.
On the other hand an electric arc spray gun simply requires a source of electric power and a supply of compressed air or other gas~ as is well known, to atomize and to propel ~he melted material in the arc to the subs~rate or target.
., :
.'`'':', ~j -1- ' '',~' " `" ~L081057 Many different base or substrate materials may be coated by thermal spraying techniques, including ferrous and non-; ferrous materials, such as iron, steel, aluminum and the like.
; However, when most conventional coating materials are sprayed, whether initially in wire, rod, or powder form, the base material requires substantial preliminary preparation, such as rough~ning ~' by grit blasting or the like, under-cutting, pre-heating and so on, in order to ensure sufficient adhesion of the sprayed coating to the base material. Sometimes post-spraying treatment, such as fusing or sintering, is required to effect good bonding between ~. .
the coating and the substrate.
A recent development in the art of spray coating has been the use of an exothermic spray material in the form of powder wherein each particle of the powder is a composite composed of ;~` nickel and aluminum. This material, one type of which is sold ;~:i under the numerical identification 404 and another 450 by Metco, ~; Inc., Westbury, New York, when sprayed in a thermal spray device will undergo an exothermic reaction and will bond reasonably well to a clean, smooth, i.e. not roughened, base material surface coating the latter. One problem with the method of thermal spray-!'~,,' ing such exothermic or synergistic powder material is the difficult task of manufacturing the necessary specialized composite powder Cj ~ !
~ particles. It has been found that spraying simply a mixture of .i, powdered aluminum particles and powdered nickel particles will not work to achieve the necessary substantially complete exothermic re-, ....................................................................... . .
action for a good bond to an unprepared base material without further treatment of the coated base material. Another disadvantage to this method of spraying such composite particles is incomplete reaction in the arc/flame thus depositing unreacted particles plus ~,t,',( 30 free nickel and free aluminum, both rather weak materials when com-, . . .
1 pared to their products.
.
:., . .:
.," ~ ~ .
.. . .
.. . .
~0B105~
SUMMARY OF ~HE INVENTION
In accordance with the present invention, an alloy of nickel and aluminum in wire form, "wire" implying elongated mate-rial dimensioned from a thin strand to a relatively thick rod, is supplied as a wire feed and is sprayed in an electric arc spray gun to coat a substrate or base material, such as steel or aluminum.
Depending on the relative weight percentages of aluminum and nickel in the alloy, there also may be contained therein, i.e. in the wire, varying percentages of intermetallics of nickel and aluminum, such as NiAl or Ni3Al, as will be apparent from a phase diagram of ` nickel and aluminum. Hereinafter when reference is made to nickel aluminum alloy or nickel titanium alloy it is to be understood that the alloy material also may include intermetallics of nickel and aluminum or nickel and titanium, respectively.
Upon being melted, atomized and sprayed by an electric arc spray gun the nickel aluminum alloy and possibly contained inter-metallics, if any, material is deposited at temperatures normally ~, greater than 1,400 F. onto a cool, clean, smooth or ground substrate or base material. The sprayed material will bond well to clean, ~ 20 smooth or ground base materials usually to form a coating having ad-i hesion and cohesion parameters or properties approximately equal to or greater than those parameters or properties of a coating formed by thermal spraying exothermically reacting powder. Analytical i results of tests of base materials coated with electric arc sprayed nickel aluminum alloy provided in wire form tend to indi-, cate that the secure bond between the base and the coating is due to atomic diffusion or metallurgical influences wherein atoms of the deposit coating are carried into the base or substrate . .
and atoms of the substrate are carried into the deposit coating.
-. . .
, 30 Also in accordance with the invention an alloy of nickel and .. '' ; ' ~: , . . .
~; -3-,.,........................................................................ . :
.,.~ , ~ 11)13~10~i7 titanium may be used in the same manner and with similar results as the nickel aluminum alloy; however, the invention will be described in detail mostly with respect to the electric arc spraying of a nickel aluminum alloy wire.
In undertakiny the method of the present invention whereby a wire comprised of a nickel aluminum alloy i5 supplied to an electric arc spray gun and that gun is used to apply a spray i coating to a base material, a nu~ber of important advantages are realized over the prior art. Firstly, the process uses an electric arc spray gun, which is more economically operated than other thermal spray equipment. Second, the material to be sprayed is supplied as a wire, which is more convenient to use than powder.
The wire may be a thin strand all the way up to a relatively thick rod as long as it is suitable for spraying through an electric arc spray gun. Third, the wire is readily formed as an alloy of ' the two primary materials nickel and aluminum or nickel and titanium, as mentioned above also possibly with respective ; intermetallics, and with varying amounts of additional hardening and fluxing additi~eq. Fourth, the cohesive, adhesive and hardness 1 20 attributes of the coating on an article formed by the method ¦ of the invention are generally equivalent to or better than corres--`i ponding attributes for a coating on an articLe sprayed with powder ;
!', using other thermal spray devices.
With the foregoing in mind it is a primary object of the :! `
invention to provide a method of imp~oved electric arc spraying as in the noted respects.
Another object of the invention is to provide a self-bonding sprayed coating to ferrous and non-ferrous substrates, which do not require any substantial preliminary preparation -1 30 to ensure a strong bond between the coating and the substrate.
An additional object of the invention is to electric arc spray a wire comprised of an alloy including at least two .., .
. -4-1081~S~
materials that self-bond to a base or substrate material, and, more particularly, wherein the alloy comprises nickel and al~minum or nickel and titanium and possibly additional respective inter-metallics.
A further object of the invention is to provide an article including a base or substrate having at least a partial coating of an alloy of nickel and aluminum or an alloy of nickel and titanium applied by electric arc spraying nickel aluminum ~alloy wire or nickel titanium alloy wire onto a surface of the `I 10 base or substrate.
Still another object of the invention is to provide a convenient, relatively uncomplicated, relatively inexpensive and effective method of electric arc spraying a self-bonding material onto a base or substrate material and an article formed thereby.
;These and other objects and advantages of the present ln-vention will become more apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully 20 described and particularly pointed out in the claims~ the following -description and the annexed drawings setting forth in detail a cer-,' tain illustrative embodiment of the invention, this being indica-; tive, however, of but one of the various ways in whiah principles of the invention may be employed.
; BRIEF DESCRIPTION OF THE DRAWINGS
,~.... . .
In the annexed drawings:
Fig. 1 is a schematic representation of an electric arc spray gun apparatus for carrying out the method of the invention to produce a sprayed, self-bonding coating on a base or substrate material;
Fig~ 2 is a magnified view at 250 times of a portion of ,... .. . . .
an article formed in accordance with the method of the invention showing the interfaces of a sprayed coating and a steel substrate;
.' .
Fig. 3 is a graph representing a microprobe analysis using a scanninq electron microscope across an electric arc sprayed nickel aluminum alloy--steel interface illustrating atomic diffusion; and Fig. 4 is a magnified view at 250 times of a portion of an article formed in accordance with the method of the invention il-lustrating particularly the in~erface of a sprayed nickel aluminum coating and a steel substrate.
DESCRIPTION OF T~IE PREFERRE.D ~ODIM~NT
Wire comprised of an alloy of nickel and aluminum or an alloy of nickel and titanium, each possibly containing varying percentages of intermetallics depending on the respective weight percents of nickel and aluminum or nickel and titanium according to the respective phase diagrams, is fed to an electric arc spray gun,such as an Arcspray 200 electric arc spray gun manufactured and sold by Metallisation Limited, Dudley, Worcs., England, a Metco ~/A gun, or the like. The wire alloy feed may comprise approximate-ly from 80 to 98~ by weight nickel and approximately from 2 to .
20~ by weight aluminum, and preferably com~rises approximately 90 to 95~ by weight nickel and approximately 4 to 6~ by weight aluminum. Hardening and fluxing additives, such as carbon, manganese, sulfur, silicon, titanium, copper and iron, also may be included in various respec~ive amounts. Preferahly the wire alloy comprises a minimum of 93% nicke}, from 4 to 5.2% aluminum, from 0.25 to 1.00~ titanium and no more than a maximum of 0.25%
copper, 0.50~ manganese, 0.60~ iron, 1.7~ silicon, 0.3~ carbon, :., and 0.01~ sulfur--all these being respective percents by weight.
Although the wire is comprised of an already formed alloy, -;l during which formation the intermetallics also may be formed, the :. ~
actual compounds in the alloy are not known with accuracy; howevar, the particular comp~unds comprising the alloy are not believed critical to the self-bonding of the thermal sprayed coating of the . ~ , .
:,;' .
:
t)5~ :
alloy wire on a base material.
When using nickel titanium alloy wire, the wire alloy may comprise, by weight, approximately from 40 to 70% nickel and approximately from 30 to 60% titanium, and preferably comprises approximately 54 to 56~ nickel and approximately 44 to 46%
titanium. ~ardening and fluxing additives also may be included, as described above.
The wire is melted in the electric arc developed in the electric arc spray gun and the molten particles are propelled by an air or other gas stream flow toward a surface of a base or substrate material for coating the same. During this spraying process, the nickel and aluminum alloy or nickel and titanium alloy will be super- I
hea~ed to temperatures exceeding the melting points of the constitu-ents or their alloys and self-bond to said substrate or base metal.
In the present invention the material to be sprayed is in the form of a wire comprised of an alloy of nickel and aluminum or nickel and titanium--not composite particles, not closely ~. :
associated particles and not two different materials making up, respectively, different strands of a multiple strand wire. The ; 20 nickel and aluminum alloy or nickel and titanium alloy is melted . .~. .
or at the least substantially softened in the arc of an elec~ric ........................................................................ .. .
arc spray gun. The hot material is then propelled by an air or -other gas stream blast to the surface of a base or substrate to ; coat the same. As will be described in more detail below, the sprayed material of the invention will bond well to the ground clean and smooth surface of a base apparently due primarily to atomic diffusion at the interface.
;~ Referring now particularly ~o Fig. 1, a conventional electric arc spray gun 10 receives a material input feed of two wires 11, 12 from two wire spools 13, 14 and an electrical input from a power supply 15. Each of the wires 11, 12 is comprised of a nickel aluminum alloy, possibly with nickel and aluminum .'' ~.
~ 7 _7_ ~10~05t7 intermetallics and possibly with added fluxing and hardening additives. Proximate the output or nozzle 16 of the gun 10~
an electric arc is created by power from the supply 15 that may be fed to the ends of both the wires, which are b~ought toward one another to create the electric arc in known manner. The ends of the wires are preferably melted in the heat of the arc, and an air blast created by an external compressed air supply, not ` shown, may atomize the material in the arc and propels the hot melted material to the surface 17 of the base or substrate 1~ material 18 to build a coating 19 thereon. A feed mechanism . in the spray gun 10 feeds the wires 11, 12 from the spools 13, 14 to the arc area to maintain a wire supply there, as is ;~ conventional. The sprayed coating will adhere well to many ferrous and non-ferrous substrates without any substantial pre-liminary preparation of the substrate except to ensure that it is clean, for example, using an emery cloth.
` The feed wires 11, 12 alternatively may be formed of .:, a nickel titanium alloy, which also self-bonds satisactorily .,.:.
to the smooth clean surface of ferrous and non-ferrous substrates upon being electric arc sprayed to coat the same. When using a nickel titanium alloy wire feed it is preferred that the wire ~! be comprised approximately rom 40 to 70% by weight nickel and - approximately from 30 to 60~ by weight titanium, and preferably ~ is comprised o from 54 to 56% by weight nickel ancl from 44 to , . . .
46% by weight titanium. ~s in the case wi~h the nickel aluminum "..~
alloy, the wire feed may include intermetallics as well as additional hardening and fluxing additives.
; In Examples I- IV and VI below the sprayed nickel ..:
aluminum alloy wire was comprised of the following materials, - 30 indicated as percents by weight as follows:
. .
,''~
.. . .
1al8~S7 I TABLE I
':
Element: C Mn S Si NiA1 Alloy Wire 0.14 0.26 0.0050.49 Element: Ni Ti Cu Al Fe . . .
` I~iA1 Alloy Wire 94.29 0.42 0.10 4.31 0.05 -. ~
EX~MPLE I
. . .
An electric arc spray gun supplied with a nickel aluminum alloy wire feed was used to spray coat several different , substrate materials, including hardened(Rc 50 minim~jAISI-1095 steel and aluminum samples. Before being spray coated, all of the sub-.:. . .
` strate specimens were ground smooth to remove surface irregularities i~ and half of the substrate specimens then were roughened by grit blasting with SAE No. 20 mesh alumina. After such preparation, both the ground smooth and the rough~ned substrate specimens were electric arc sprayed with the nickel aluminum alloy wire to ;' a 0.25 to 0.30 inch thickness. ~
Adhesion test~ then were performed of the coated substrates according to AST~l C633-69 "Adhesion or Cohesive Strength of , Flame Sprayed Coatings". 'rhe measured coating strength is presented in Ta~le II.
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.
; TABLE II
~, TENSILE/
;~ SUBSTRATE BOND STRENGTH (pSl) ~; and ~. MATERIAL CONDITION ~CTUAL AVLRAGE
.'', _ ~ ~
~` ~,500 . - .
~:: GROUND4,900 ~,767 .,~ . 4,900 STEEL
,.1 4,900 ,~, ROUGHENED 6,000 5,400 .: . 5,300 ~:
. _
; This invention relates to a method of electric arc spraying self-bonding materials and an article formulated by the same. More specifically, the invention relates to a thermal spraying of nickel aluminum alloys or nickel titanium alloys, which alloys may include varying percentages of intermetallics of nickel and aluminum or nickel and titanium, respectively, in wire form using an electric arc spray gun.
The use of thermal sprayed coatings has been widely accept-ed in recent years, for example, for protecting substrates for cry-ogenic or refractory purposes, for parts repair, for protection of a substrate from oxidizing or from other hostile environments, and for many other purposes. However, the search for new materials with which to spray and new techniques for spraying is continuing '1 in an effort to achieve better coatings befitting new applications ;' and time saving methods particularly to avoid preliminary base or substrate preparation and/or post coating and base treatment.
; Several types of thermal spraying guns are available in-cluding combustion flame spray guns, e.g., the oxy-fuel gas type, plasma arc spray guns and electric arc spray guns. Combustion flame spray guns require a source of fuel, such as acetylene, and oxygen ;
and the temperatures produced therein are usually relatively low and often incapable of spraying materials having melting points i exceeding 5,000F. Plasma arc spray guns are usually the most ex-pensive type and they produce much higher temperatures than the com-bustion type, e.g. up to approximately 30,000F. Furthermore, plasma arc spray guns require a source of inert gas, such as argon, ~ for creation of the plasma, and the gas flow rate and electric power - therefor require extremely accurate control for proper operation. ;~
.. ~ . ,.
On the other hand an electric arc spray gun simply requires a source of electric power and a supply of compressed air or other gas~ as is well known, to atomize and to propel ~he melted material in the arc to the subs~rate or target.
., :
.'`'':', ~j -1- ' '',~' " `" ~L081057 Many different base or substrate materials may be coated by thermal spraying techniques, including ferrous and non-; ferrous materials, such as iron, steel, aluminum and the like.
; However, when most conventional coating materials are sprayed, whether initially in wire, rod, or powder form, the base material requires substantial preliminary preparation, such as rough~ning ~' by grit blasting or the like, under-cutting, pre-heating and so on, in order to ensure sufficient adhesion of the sprayed coating to the base material. Sometimes post-spraying treatment, such as fusing or sintering, is required to effect good bonding between ~. .
the coating and the substrate.
A recent development in the art of spray coating has been the use of an exothermic spray material in the form of powder wherein each particle of the powder is a composite composed of ;~` nickel and aluminum. This material, one type of which is sold ;~:i under the numerical identification 404 and another 450 by Metco, ~; Inc., Westbury, New York, when sprayed in a thermal spray device will undergo an exothermic reaction and will bond reasonably well to a clean, smooth, i.e. not roughened, base material surface coating the latter. One problem with the method of thermal spray-!'~,,' ing such exothermic or synergistic powder material is the difficult task of manufacturing the necessary specialized composite powder Cj ~ !
~ particles. It has been found that spraying simply a mixture of .i, powdered aluminum particles and powdered nickel particles will not work to achieve the necessary substantially complete exothermic re-, ....................................................................... . .
action for a good bond to an unprepared base material without further treatment of the coated base material. Another disadvantage to this method of spraying such composite particles is incomplete reaction in the arc/flame thus depositing unreacted particles plus ~,t,',( 30 free nickel and free aluminum, both rather weak materials when com-, . . .
1 pared to their products.
.
:., . .:
.," ~ ~ .
.. . .
.. . .
~0B105~
SUMMARY OF ~HE INVENTION
In accordance with the present invention, an alloy of nickel and aluminum in wire form, "wire" implying elongated mate-rial dimensioned from a thin strand to a relatively thick rod, is supplied as a wire feed and is sprayed in an electric arc spray gun to coat a substrate or base material, such as steel or aluminum.
Depending on the relative weight percentages of aluminum and nickel in the alloy, there also may be contained therein, i.e. in the wire, varying percentages of intermetallics of nickel and aluminum, such as NiAl or Ni3Al, as will be apparent from a phase diagram of ` nickel and aluminum. Hereinafter when reference is made to nickel aluminum alloy or nickel titanium alloy it is to be understood that the alloy material also may include intermetallics of nickel and aluminum or nickel and titanium, respectively.
Upon being melted, atomized and sprayed by an electric arc spray gun the nickel aluminum alloy and possibly contained inter-metallics, if any, material is deposited at temperatures normally ~, greater than 1,400 F. onto a cool, clean, smooth or ground substrate or base material. The sprayed material will bond well to clean, ~ 20 smooth or ground base materials usually to form a coating having ad-i hesion and cohesion parameters or properties approximately equal to or greater than those parameters or properties of a coating formed by thermal spraying exothermically reacting powder. Analytical i results of tests of base materials coated with electric arc sprayed nickel aluminum alloy provided in wire form tend to indi-, cate that the secure bond between the base and the coating is due to atomic diffusion or metallurgical influences wherein atoms of the deposit coating are carried into the base or substrate . .
and atoms of the substrate are carried into the deposit coating.
-. . .
, 30 Also in accordance with the invention an alloy of nickel and .. '' ; ' ~: , . . .
~; -3-,.,........................................................................ . :
.,.~ , ~ 11)13~10~i7 titanium may be used in the same manner and with similar results as the nickel aluminum alloy; however, the invention will be described in detail mostly with respect to the electric arc spraying of a nickel aluminum alloy wire.
In undertakiny the method of the present invention whereby a wire comprised of a nickel aluminum alloy i5 supplied to an electric arc spray gun and that gun is used to apply a spray i coating to a base material, a nu~ber of important advantages are realized over the prior art. Firstly, the process uses an electric arc spray gun, which is more economically operated than other thermal spray equipment. Second, the material to be sprayed is supplied as a wire, which is more convenient to use than powder.
The wire may be a thin strand all the way up to a relatively thick rod as long as it is suitable for spraying through an electric arc spray gun. Third, the wire is readily formed as an alloy of ' the two primary materials nickel and aluminum or nickel and titanium, as mentioned above also possibly with respective ; intermetallics, and with varying amounts of additional hardening and fluxing additi~eq. Fourth, the cohesive, adhesive and hardness 1 20 attributes of the coating on an article formed by the method ¦ of the invention are generally equivalent to or better than corres--`i ponding attributes for a coating on an articLe sprayed with powder ;
!', using other thermal spray devices.
With the foregoing in mind it is a primary object of the :! `
invention to provide a method of imp~oved electric arc spraying as in the noted respects.
Another object of the invention is to provide a self-bonding sprayed coating to ferrous and non-ferrous substrates, which do not require any substantial preliminary preparation -1 30 to ensure a strong bond between the coating and the substrate.
An additional object of the invention is to electric arc spray a wire comprised of an alloy including at least two .., .
. -4-1081~S~
materials that self-bond to a base or substrate material, and, more particularly, wherein the alloy comprises nickel and al~minum or nickel and titanium and possibly additional respective inter-metallics.
A further object of the invention is to provide an article including a base or substrate having at least a partial coating of an alloy of nickel and aluminum or an alloy of nickel and titanium applied by electric arc spraying nickel aluminum ~alloy wire or nickel titanium alloy wire onto a surface of the `I 10 base or substrate.
Still another object of the invention is to provide a convenient, relatively uncomplicated, relatively inexpensive and effective method of electric arc spraying a self-bonding material onto a base or substrate material and an article formed thereby.
;These and other objects and advantages of the present ln-vention will become more apparent as the following description proceeds.
To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully 20 described and particularly pointed out in the claims~ the following -description and the annexed drawings setting forth in detail a cer-,' tain illustrative embodiment of the invention, this being indica-; tive, however, of but one of the various ways in whiah principles of the invention may be employed.
; BRIEF DESCRIPTION OF THE DRAWINGS
,~.... . .
In the annexed drawings:
Fig. 1 is a schematic representation of an electric arc spray gun apparatus for carrying out the method of the invention to produce a sprayed, self-bonding coating on a base or substrate material;
Fig~ 2 is a magnified view at 250 times of a portion of ,... .. . . .
an article formed in accordance with the method of the invention showing the interfaces of a sprayed coating and a steel substrate;
.' .
Fig. 3 is a graph representing a microprobe analysis using a scanninq electron microscope across an electric arc sprayed nickel aluminum alloy--steel interface illustrating atomic diffusion; and Fig. 4 is a magnified view at 250 times of a portion of an article formed in accordance with the method of the invention il-lustrating particularly the in~erface of a sprayed nickel aluminum coating and a steel substrate.
DESCRIPTION OF T~IE PREFERRE.D ~ODIM~NT
Wire comprised of an alloy of nickel and aluminum or an alloy of nickel and titanium, each possibly containing varying percentages of intermetallics depending on the respective weight percents of nickel and aluminum or nickel and titanium according to the respective phase diagrams, is fed to an electric arc spray gun,such as an Arcspray 200 electric arc spray gun manufactured and sold by Metallisation Limited, Dudley, Worcs., England, a Metco ~/A gun, or the like. The wire alloy feed may comprise approximate-ly from 80 to 98~ by weight nickel and approximately from 2 to .
20~ by weight aluminum, and preferably com~rises approximately 90 to 95~ by weight nickel and approximately 4 to 6~ by weight aluminum. Hardening and fluxing additives, such as carbon, manganese, sulfur, silicon, titanium, copper and iron, also may be included in various respec~ive amounts. Preferahly the wire alloy comprises a minimum of 93% nicke}, from 4 to 5.2% aluminum, from 0.25 to 1.00~ titanium and no more than a maximum of 0.25%
copper, 0.50~ manganese, 0.60~ iron, 1.7~ silicon, 0.3~ carbon, :., and 0.01~ sulfur--all these being respective percents by weight.
Although the wire is comprised of an already formed alloy, -;l during which formation the intermetallics also may be formed, the :. ~
actual compounds in the alloy are not known with accuracy; howevar, the particular comp~unds comprising the alloy are not believed critical to the self-bonding of the thermal sprayed coating of the . ~ , .
:,;' .
:
t)5~ :
alloy wire on a base material.
When using nickel titanium alloy wire, the wire alloy may comprise, by weight, approximately from 40 to 70% nickel and approximately from 30 to 60% titanium, and preferably comprises approximately 54 to 56~ nickel and approximately 44 to 46%
titanium. ~ardening and fluxing additives also may be included, as described above.
The wire is melted in the electric arc developed in the electric arc spray gun and the molten particles are propelled by an air or other gas stream flow toward a surface of a base or substrate material for coating the same. During this spraying process, the nickel and aluminum alloy or nickel and titanium alloy will be super- I
hea~ed to temperatures exceeding the melting points of the constitu-ents or their alloys and self-bond to said substrate or base metal.
In the present invention the material to be sprayed is in the form of a wire comprised of an alloy of nickel and aluminum or nickel and titanium--not composite particles, not closely ~. :
associated particles and not two different materials making up, respectively, different strands of a multiple strand wire. The ; 20 nickel and aluminum alloy or nickel and titanium alloy is melted . .~. .
or at the least substantially softened in the arc of an elec~ric ........................................................................ .. .
arc spray gun. The hot material is then propelled by an air or -other gas stream blast to the surface of a base or substrate to ; coat the same. As will be described in more detail below, the sprayed material of the invention will bond well to the ground clean and smooth surface of a base apparently due primarily to atomic diffusion at the interface.
;~ Referring now particularly ~o Fig. 1, a conventional electric arc spray gun 10 receives a material input feed of two wires 11, 12 from two wire spools 13, 14 and an electrical input from a power supply 15. Each of the wires 11, 12 is comprised of a nickel aluminum alloy, possibly with nickel and aluminum .'' ~.
~ 7 _7_ ~10~05t7 intermetallics and possibly with added fluxing and hardening additives. Proximate the output or nozzle 16 of the gun 10~
an electric arc is created by power from the supply 15 that may be fed to the ends of both the wires, which are b~ought toward one another to create the electric arc in known manner. The ends of the wires are preferably melted in the heat of the arc, and an air blast created by an external compressed air supply, not ` shown, may atomize the material in the arc and propels the hot melted material to the surface 17 of the base or substrate 1~ material 18 to build a coating 19 thereon. A feed mechanism . in the spray gun 10 feeds the wires 11, 12 from the spools 13, 14 to the arc area to maintain a wire supply there, as is ;~ conventional. The sprayed coating will adhere well to many ferrous and non-ferrous substrates without any substantial pre-liminary preparation of the substrate except to ensure that it is clean, for example, using an emery cloth.
` The feed wires 11, 12 alternatively may be formed of .:, a nickel titanium alloy, which also self-bonds satisactorily .,.:.
to the smooth clean surface of ferrous and non-ferrous substrates upon being electric arc sprayed to coat the same. When using a nickel titanium alloy wire feed it is preferred that the wire ~! be comprised approximately rom 40 to 70% by weight nickel and - approximately from 30 to 60~ by weight titanium, and preferably ~ is comprised o from 54 to 56% by weight nickel ancl from 44 to , . . .
46% by weight titanium. ~s in the case wi~h the nickel aluminum "..~
alloy, the wire feed may include intermetallics as well as additional hardening and fluxing additives.
; In Examples I- IV and VI below the sprayed nickel ..:
aluminum alloy wire was comprised of the following materials, - 30 indicated as percents by weight as follows:
. .
,''~
.. . .
1al8~S7 I TABLE I
':
Element: C Mn S Si NiA1 Alloy Wire 0.14 0.26 0.0050.49 Element: Ni Ti Cu Al Fe . . .
` I~iA1 Alloy Wire 94.29 0.42 0.10 4.31 0.05 -. ~
EX~MPLE I
. . .
An electric arc spray gun supplied with a nickel aluminum alloy wire feed was used to spray coat several different , substrate materials, including hardened(Rc 50 minim~jAISI-1095 steel and aluminum samples. Before being spray coated, all of the sub-.:. . .
` strate specimens were ground smooth to remove surface irregularities i~ and half of the substrate specimens then were roughened by grit blasting with SAE No. 20 mesh alumina. After such preparation, both the ground smooth and the rough~ned substrate specimens were electric arc sprayed with the nickel aluminum alloy wire to ;' a 0.25 to 0.30 inch thickness. ~
Adhesion test~ then were performed of the coated substrates according to AST~l C633-69 "Adhesion or Cohesive Strength of , Flame Sprayed Coatings". 'rhe measured coating strength is presented in Ta~le II.
~.,.'j , '''' ".
.'''~`, ' ' ' .
. ~ `. . .
.. .:.. ..
' 1, ' :
: . .
,, . _g_ '''~: ,' ' '~
~.~''' . .
.'.~ , .
,~ .
.
; TABLE II
~, TENSILE/
;~ SUBSTRATE BOND STRENGTH (pSl) ~; and ~. MATERIAL CONDITION ~CTUAL AVLRAGE
.'', _ ~ ~
~` ~,500 . - .
~:: GROUND4,900 ~,767 .,~ . 4,900 STEEL
,.1 4,900 ,~, ROUGHENED 6,000 5,400 .: . 5,300 ~:
. _
2,700 :.
GROUNDlj500 2,500 " : . . 3,300 -.
~' ; ALUMINUM _ '~ : . 5,400 :, . ROUGHENED 6,700 6,033 . 6,000 . ~ , . ~'~
, : ~:
. "
''. ,.
,, , '' '' ' - . --10--". ~ .
, .;,............ . .
.; ~ .
i ~:"' ' ~' . .
A transverse section of one o F the coat~d, un-roughened substrate specimens was examined by light microscopy.
Structurally, as seen in Fig. 2, the deposit, the upper half of ~; the figure, was morphologically similar to other thermal sprayed materials, l.e., undulating, lamellar particles separated by oxides with interdlspersed voids. Dissimilariky was noticed, -however, at the interface. The coating-substrate interface was ` extremely tight, and at some points along the substrate side of the interface, there was a change in the martensitic structure, as can be seen slightly right of center along and below the interface line. Apparently, on impact with the steel, the i lower and darker half of Fig. 2, the hot, molten nickel aluminum particles caused the martensite to change into upper trans-'~ formation~products, probably retained austenite and some lightly tempered martensite, and to have accomplished this transformation, the steel would have had to have been heated above i~ critical v' ~ . .
- temperature of approximately 1,400F. There was, however, no ~ evidence of fusion or of a bond alloy layer at the interface, :,.j ' .
which led to the belief that the achieved self-bonding of "''! 20 the coating to the substrate was not chemical or metallurgical '~ but might be due to atomic diffusion.
` A qualitative spectrographic analysis of the sprayed ,....................................................................... ;
coating was made Witil the following result:
;~ TABL~. III
.;
Mn Heavy Trace Al Minor Si Heavv Trace B Slight Trace Cr lIeavy Trace Co Trace Ni Major Cu Heavy Trace Ti Minor Zr Slight Trace Mo Heavy Trace Ag Detected " "!
Fe Heavy Trace Pb Slight Trace ~: ;
Mg Very Slight Trace Sn Trace 1 Zn Detected -,.: :
: :. . .
,, . . . . . : , . .
~`` 108~S~
:
A 12 inch by one inch diameter steel bar pxoduced from hardened (Rc 50 minimum) AISI-1095 steel, which was heat treated and ground smooth on its surface, was spray coated with a .150 inch thickness of material by an electric arc spray gun having the nickel aluminum alloy wire supplied thereto, as described above. The macrohardness of the coating was measured on the Rockwell B scale usin~ a 1/16th ball indentor with a lOOkg load, and the measured microhardness was in the range of from 69 to 71. Moreover, a microhardness of the same sample was determined utilizing a rhomboidal diamond indentor and a " .
100 gm load (KHN 100) In accordance with this latter test it was possible to isolate and to determine the hardness of ` individual particles, the average measurement of hardness being 179 KIINloo, which value converts to Rb85. The difference in coating and particle hardness was attributed to voids and oxides within the coating which collapse under the load o the ball ; indentor. Furthermore, the coating density ~as measured and found to be 0.2758 pounds per cubic inch.
EXAMPLE III
A nickel aluminum alloy wire was supplied to an electric arc spray gun and the gun was used to spray coat a low carbon steel substrate. rrhe coated substrate was prepared ,~ for a metallographic viewing using a scanning electron microscope (SEM). A graph illustrative of the microprobe analysis across l the coating-s*eel interface is illustrated in Fig. 3. In the ¦ graph, which is read from right to left beginning approximately 1l three microns beneath the surface of the steel substrate, the ;~ iron content thereof is at maximum value, whereas there is j 30 virtually no nickel found. Similarly, at a depth approximately three microns into the coating, beginning at the left-hand side :: I
-':: 'I ' .
., -12-:
,,,.
of the yraph, the amount of nickel is at a substantially maximum level and substantially no iron is found. ~t the interface, however, there is no sharply defined boundary; rather, it is .~ quite.clear that a relatively large number of iron atoms or . particles have diffused into the nickel coating and a large number of nickel atoms or particles have diffused into the iron :. substrate. This atomic migration or diffusion to a depth somewhat less than one micron into the substrate and into the coating t appears to be the reason for the high tenacity or affinity of . 10 the electric arc spray coating to the substrate.
The chemistry of the coating material was determined by wet analysis, and the values in percents by weight obtained .` are noted below:
. TABLE IV
. C 0.06 Ti 0.65 .- Mn 0.21 Cu O.C08 :.
: S 0.003 Al 5.45 :: Si 0.34 ~ Fe 0.043 .:. .
~ Ni 92.80 : , .
.~ 20 EXAMPLE IV
. "
....................... The adherence of a coating formed by an electric arc sprayed nickel aluminum alloy wire to various eng.ineering metals "
;l was ascertained. Each of the substrate specimens was clean .
.~ and unroughened, and each was electric arc sprayed using the . .-.:l nickel aluminum alloy wire. The adhesion tests were carried .l out as described above in Example I for the following materials, ~
and the obtained adhesive/cohesive strength between the ~ ~.
.1 coating and the substrate were as follows:
:,~ l : .
~'1 ' ' ' ::~
r, " '' ~.-: -13-.";:..
, ....
::.
,., ~ .;
.. :............................. . .
TABL~ V
; SUBSTRATE MATERIAL ADiIESIV~/CO~IESIyE STRENGTH
_.
ACTUALAV~RAGE
(psi)(~
Steel, AISI ~330 5180 Annealed, R~96 5210S2S0 ~: 5450 i ` 4710 -~ lIardened, R 48 48904713 '~ Carburized AISI 1010 4890 ', FC62 ` 48504883 ~ 4910 .,~
.l ~itr ted, Nitralloy 135G 56105033 ~- 4870 i~ ~
` 18-8 Stainless Steel 4120 R~75 41404200 , Martensitic Stainless 3890 AISI 431, Rc44 41004107 : 43 ~ge }lardenable Steel 4910 17-4pH, RC42 48704857 , Aluminum 3200 ~ loo-o 18002303 :, 1910 , :~ 23402210 23~02583 . 2670 ~' ~agnesium 1790 ;~ AZ80~T6 18001847 ``~ 1950 ' ' I
I Gray Cast Iron 4280 .il . 31703633 ,:~, 3450 :~ Titanium 3320 ;, Ti6A14V 2970 ', Copper NO-TEST1390 . 780 '.' :' ~''';' :`. -1~ -., ";' ~lO~310$7 From the tests conducted as described in Example IV, it appears that an electric arc sprayed nickelaluminum alloy wire material will not adhere very well to a copper substrate. Ilowever, adherence to various types of ferrous materials as well as non-` ferrous. materials, including aluminum,magnesium and titanium, clearly is manifest.
EXAMPLE V
~i Three different nickel aluminum alloy wires were ' electric arc sprayed onto respective substrates to determine whether any variations occurred in adhesive and cohesive strengths .
and in microhardness and macrohardness characteristics of therespective sprayed coatings as the actual ratio of nickel to - aluminum and the quantity of hardening, fluxing and other additives were varied. The three nickel aluminum alloy wires, designated . .
.~ "H"j "I" and "W" were first analyzed by wet chem~.cal analysis to determine their chemical makeup in percent by weight, and the result of that analysis is presented as follows~
-~ TABLE VI ..
: . .
.. ~lement: C Mn S Si Ni , . .....
:~ Wire : .
. Sample _ .
I" 0.005 0.23 - 1.68 92.397 .;; "I" 0.040 0.23 - 0.47 93.636 :
; "W" 0.003 0.27 - 1.02 92.~2 .
Element : Ti Cu Al Fe . Wire .: . Sample .:., "Il" .44 0.0~ 5.06 0.108 .. ` "I" .40 0.08 5.05 0.094 . "W" .40 0.72 5.14 0.275 .:,,-,:, .. , , - :
.' ', .
,; ' ": . ' .. .;, -~.................................... 15 . .
.... ~
" .
The test procedures and specimen preparation were performed similar to those described above with reference to Examples I and II, and the respective specimen substrates were formed of aluminum,iron, or copper.
Each of the respective specimen substrates was electric arc sprayed with one of the nickel aluminum alloy wires indicated above as "~ "I" or "~". A Metco electric arc spray yun was used according to the following parameters:
Electrodes: 15 Gage Atomizing air: 92 psi ~-~ Amperage: 260 to 275 amps.
~ Voltage: 34 volts ; The tensile/bond strength of the respective spray coated substrates and the failure mode of each were determined - as above, and the results are presented in following Table VII.
Under the Failure Mode category in the table, the location of the failure and the -type of failure are indicated. For example, "Interfac~/Ad" means that failure occurred at the ; interface between the sprayed coating and the substrate and ~- 20 the failure was in the adhesion of the coating to the substrate.
'~oating/Cohe" means that failure occurred only in the coating itself and the failure was in the cohesiveness or cohesion of ~' the coating material itself. "Epoxy Failure" means that the , .; ~
failure occurred in the epoxy matexial securing the test ; sample to the testing apparatus.
..
...
...
'''' ' :
. ,, . ~
."", , , .: .
~, . .
.
'~:'1 .
. .
'".,;, :', ~. "' ; ' .!.' ~
TABLE VII ::
~ ~ .
TENSILE/BOND :
~T~RIAL STRENGTII
COAT- ACTUAL, A~G., FAILURE MODE
ING SUBST~ATE (psi) ~psi) LOCATION/TYPE
6700 Interface/Ad . Aluminum 56006200 Interface/Ad . 6300 Interfa~eJAd ., _ _ .
. 4800 . Coating/Cohe ; ~ . Iron 5600 4867Coating/Cohe 4200 Coating/Cohe . . _ _ .~ No Test . Copper No Test 2167 . ~.
:l. . 6500 Interface/Ad :
:, . . . _ ~
' : 6700 Interface/Ad :~ Aluminum 6 0 0 05 ~ 67 Interface/Ad .4900 Interface/Ad ." ~
52û0 Coating/Cohe Iron 6500 5733Coating/Cohe ~'~ ~ ` 5500 : Coating/Cohe ~a~ . No Test . Copper No Test . .
.: No Test , .. _ .
.~ . 7000 Epoxy E'ailure ;
Aluminum 8200 7533Epoxy Failure i . 7400 . Interface/Ad ,, . l 5 2 0 0 .Co ating,/Cohe ~'~; W Iron 6500 5733Coating/Cohe $: ~ : 5500 Coating/Cohe ',~ _ No Test Copper No Test i : .
: No Test ~, . _ _ . _ ':"1 .
' -17-.,. ~ .. .
1~ 5~
None of the spraying materials adhered well to the copper substrates. For each of the iron substrates, the failure mode was cohesive in nature, i e., failure occurred due to breaking of the coating rather than separation at the interface.
In all but two of the aluminum coated substrates the failure was of an adhesive nature, i.e., failure occurred at the interface. In two instances of aluminum coated substrates, the failure was at the epoxy coupling used in the test.
; From the results presented in the above table, it will be clear that ~he nickel aluminum alloy wire that is electric arc sprayed to coat smooth surfaces of aluminum and iron substrates will self-bond extremely well to those substrates.
Coating microhardness for each of the specimens including the coated substrates was determined utilizing the rhomboidal ICnoop indentor with a 50 gm load. ~acrohardness was ascertained using . !
a one kilogram load and the Vickers hardness (DPI-I~ tester, the measurements using the latter being converted for facility of comparison to the Rockwell C scale indicated in column :; .
Rc in Table VIII below. The results of the microhardness and macrohardness measurements are presented as follows:
TABLE VIII
TERIAL Rc CON-COATING SUBSTI~ATE l~llN50 DPII YERSION
.. ` _ __ __. .
r~
Aluminum 449 283 27.7 Iron 562 Copper 562 _ . _ - Aluminum 631 316 3I.9 ~: I Iron 618 311 31.2 Copper 605 292 28 9 Aluminum 605 279 27.0 W Iron 670 283 27.7 i Copper 710 293 28.9 ,, ~ . :
l81~5~7 In view of the above two tables presented in this example, it is clear that nickel aluminum alloy wire having varying proportions of Eluxing and hardening agents and some variation in the ratio of nickel to aluminum will exhibit good self-bonding properties when electric arc sprayed onto steel or aluminum substrates. Variations in the ratio of nickel to aluminum and in the additives will not appreciably reduce the bond tenacity. Moreover, by varying or shifting the fluxing and `-hardening additives in the nickel aluminum alloy wire, the hard- -; 10 ness of the resulting sprayed coating is affected.
The microstructure of respective stPel specimens having smooth or ground surfaces onto which the respective nickel aluminum alloy wires "H", "I" and "W" were sprayed was examined.
A photomicrograph taken of the interface of the nickel aluminum alloy wire "I" applied over a hardened, tempered, ground smooth martensltic substrate is illustrated in Fig. 4. The lower and ~`;; ` darker portion of the figure represents the martensite and the : upper lamellar and lighter colored area represents the sprayed i. - coating. Approximately at a location slightly right of the i` 20 center of the igure is a lightened area in the martensite, which is an area of untempered martensite caused, apparently, due to .
the heat of the nickel aluminum coating as it is applied to the martensite.
; EXAMPLE VI
.":.; :
Samples of a nickel aluminum wire feed, as identified ~.' ' .
in Table I above, were electric arc sprayed onto respective steel and aluminu~ substrates and subsequently heat treated as follows:
~;~; Aluminum- 12 hours at 950F., water ,~ quenched, aged 6 hours at 525F.
`~ Steel- 8 hours at 1200F., furnace cooled.
.. .. .
~ ~ ~ ... .
':, , i; ,. , . ~
llQ~10~
Aside from exhibiting excellent resistance to thermal shock the samples displayed higher than normal adhesive strength. When tested in accordance with Example I fracture occurred not in the deposit but rather in the epoxy. Results were as follows:
Aluminum9300 psi 10800 psi ` Steel11200 psi lOgOO psi `
11800 psi ~` :
Thus, the described treating process, including aging, will increase the overall strength of the coating and the coating-substrate bond strength. Therefore, it will be clear that the overall integrity of the deposit or coating may ~e increased by ' heat treatment and/or aging.
While the foregoing examples and discussion have been directed to the electric arc spraying of a nickel aluminum alloy in wire form to coat a smooth substrate in a manner~such that the coating will self-bond to the smooth surface of the ;' substrate, other alloy materials that will self-bond when ' sprayed from an electric arc spray gun also may be used in ;
accordance with the invention. As described above, one such ; materlal is an alloy of nickel and titanium comprised of approxi-mately 40 to 70% by weight nickel and approximately 30 to 60%
by weight titanium and preferably approximately 54 to 56% by ~' weight nickel and approximately 44 to 46~ by weight titanium.
. .. . .
It has thus been found that an alloy of nickel and aluminum in wire form which is electric arc sprayed to coat a clean smooth `~ substrate will self-bond to the substrate without the occurrence ;
of an exothermic reaction. On the other hand pre-alloyed nickel . ~ , , .
.
`
05~
aluminum powder does not bond well to such a substrate when sprayed in a plasma or combustion gas, nor will nickel aluminum .
alloy wire bond well to such a substrate when combustion gas sprayed.
:.
r~loreoverr it also has been found that pre-alloyed nickel aluminum wires when electric arc sprayed exceed the reported property values of composites applied by other thermal spray techniques. Furthermore, electric arc spray rates and deposit efficiencies, especially using the nickel aluminum alloy ~ 10 wire or nickel titanium alloy wire in accordance wlth the ; invention, are appreciably higher yielding of superior deposits at lower costs than thermal spraying synergistic, exothermic r' ' materials.
,;:
....
'; I
;' .
,',''i ,' .
i, .~,i~ i .~.,'.;', ~' ' ~` i ' ,Yi ~ .
~!
~'`. .
/` ~ '' .. ,..... ' . :
.'".'~
,~.'J;
,.. ~
i ~, 1 ' ';''' i ~A
.`, j'.. . . . . .
~ '.
~'''', ,",, ~ .
~ 21 :' i ,
GROUNDlj500 2,500 " : . . 3,300 -.
~' ; ALUMINUM _ '~ : . 5,400 :, . ROUGHENED 6,700 6,033 . 6,000 . ~ , . ~'~
, : ~:
. "
''. ,.
,, , '' '' ' - . --10--". ~ .
, .;,............ . .
.; ~ .
i ~:"' ' ~' . .
A transverse section of one o F the coat~d, un-roughened substrate specimens was examined by light microscopy.
Structurally, as seen in Fig. 2, the deposit, the upper half of ~; the figure, was morphologically similar to other thermal sprayed materials, l.e., undulating, lamellar particles separated by oxides with interdlspersed voids. Dissimilariky was noticed, -however, at the interface. The coating-substrate interface was ` extremely tight, and at some points along the substrate side of the interface, there was a change in the martensitic structure, as can be seen slightly right of center along and below the interface line. Apparently, on impact with the steel, the i lower and darker half of Fig. 2, the hot, molten nickel aluminum particles caused the martensite to change into upper trans-'~ formation~products, probably retained austenite and some lightly tempered martensite, and to have accomplished this transformation, the steel would have had to have been heated above i~ critical v' ~ . .
- temperature of approximately 1,400F. There was, however, no ~ evidence of fusion or of a bond alloy layer at the interface, :,.j ' .
which led to the belief that the achieved self-bonding of "''! 20 the coating to the substrate was not chemical or metallurgical '~ but might be due to atomic diffusion.
` A qualitative spectrographic analysis of the sprayed ,....................................................................... ;
coating was made Witil the following result:
;~ TABL~. III
.;
Mn Heavy Trace Al Minor Si Heavv Trace B Slight Trace Cr lIeavy Trace Co Trace Ni Major Cu Heavy Trace Ti Minor Zr Slight Trace Mo Heavy Trace Ag Detected " "!
Fe Heavy Trace Pb Slight Trace ~: ;
Mg Very Slight Trace Sn Trace 1 Zn Detected -,.: :
: :. . .
,, . . . . . : , . .
~`` 108~S~
:
A 12 inch by one inch diameter steel bar pxoduced from hardened (Rc 50 minimum) AISI-1095 steel, which was heat treated and ground smooth on its surface, was spray coated with a .150 inch thickness of material by an electric arc spray gun having the nickel aluminum alloy wire supplied thereto, as described above. The macrohardness of the coating was measured on the Rockwell B scale usin~ a 1/16th ball indentor with a lOOkg load, and the measured microhardness was in the range of from 69 to 71. Moreover, a microhardness of the same sample was determined utilizing a rhomboidal diamond indentor and a " .
100 gm load (KHN 100) In accordance with this latter test it was possible to isolate and to determine the hardness of ` individual particles, the average measurement of hardness being 179 KIINloo, which value converts to Rb85. The difference in coating and particle hardness was attributed to voids and oxides within the coating which collapse under the load o the ball ; indentor. Furthermore, the coating density ~as measured and found to be 0.2758 pounds per cubic inch.
EXAMPLE III
A nickel aluminum alloy wire was supplied to an electric arc spray gun and the gun was used to spray coat a low carbon steel substrate. rrhe coated substrate was prepared ,~ for a metallographic viewing using a scanning electron microscope (SEM). A graph illustrative of the microprobe analysis across l the coating-s*eel interface is illustrated in Fig. 3. In the ¦ graph, which is read from right to left beginning approximately 1l three microns beneath the surface of the steel substrate, the ;~ iron content thereof is at maximum value, whereas there is j 30 virtually no nickel found. Similarly, at a depth approximately three microns into the coating, beginning at the left-hand side :: I
-':: 'I ' .
., -12-:
,,,.
of the yraph, the amount of nickel is at a substantially maximum level and substantially no iron is found. ~t the interface, however, there is no sharply defined boundary; rather, it is .~ quite.clear that a relatively large number of iron atoms or . particles have diffused into the nickel coating and a large number of nickel atoms or particles have diffused into the iron :. substrate. This atomic migration or diffusion to a depth somewhat less than one micron into the substrate and into the coating t appears to be the reason for the high tenacity or affinity of . 10 the electric arc spray coating to the substrate.
The chemistry of the coating material was determined by wet analysis, and the values in percents by weight obtained .` are noted below:
. TABLE IV
. C 0.06 Ti 0.65 .- Mn 0.21 Cu O.C08 :.
: S 0.003 Al 5.45 :: Si 0.34 ~ Fe 0.043 .:. .
~ Ni 92.80 : , .
.~ 20 EXAMPLE IV
. "
....................... The adherence of a coating formed by an electric arc sprayed nickel aluminum alloy wire to various eng.ineering metals "
;l was ascertained. Each of the substrate specimens was clean .
.~ and unroughened, and each was electric arc sprayed using the . .-.:l nickel aluminum alloy wire. The adhesion tests were carried .l out as described above in Example I for the following materials, ~
and the obtained adhesive/cohesive strength between the ~ ~.
.1 coating and the substrate were as follows:
:,~ l : .
~'1 ' ' ' ::~
r, " '' ~.-: -13-.";:..
, ....
::.
,., ~ .;
.. :............................. . .
TABL~ V
; SUBSTRATE MATERIAL ADiIESIV~/CO~IESIyE STRENGTH
_.
ACTUALAV~RAGE
(psi)(~
Steel, AISI ~330 5180 Annealed, R~96 5210S2S0 ~: 5450 i ` 4710 -~ lIardened, R 48 48904713 '~ Carburized AISI 1010 4890 ', FC62 ` 48504883 ~ 4910 .,~
.l ~itr ted, Nitralloy 135G 56105033 ~- 4870 i~ ~
` 18-8 Stainless Steel 4120 R~75 41404200 , Martensitic Stainless 3890 AISI 431, Rc44 41004107 : 43 ~ge }lardenable Steel 4910 17-4pH, RC42 48704857 , Aluminum 3200 ~ loo-o 18002303 :, 1910 , :~ 23402210 23~02583 . 2670 ~' ~agnesium 1790 ;~ AZ80~T6 18001847 ``~ 1950 ' ' I
I Gray Cast Iron 4280 .il . 31703633 ,:~, 3450 :~ Titanium 3320 ;, Ti6A14V 2970 ', Copper NO-TEST1390 . 780 '.' :' ~''';' :`. -1~ -., ";' ~lO~310$7 From the tests conducted as described in Example IV, it appears that an electric arc sprayed nickelaluminum alloy wire material will not adhere very well to a copper substrate. Ilowever, adherence to various types of ferrous materials as well as non-` ferrous. materials, including aluminum,magnesium and titanium, clearly is manifest.
EXAMPLE V
~i Three different nickel aluminum alloy wires were ' electric arc sprayed onto respective substrates to determine whether any variations occurred in adhesive and cohesive strengths .
and in microhardness and macrohardness characteristics of therespective sprayed coatings as the actual ratio of nickel to - aluminum and the quantity of hardening, fluxing and other additives were varied. The three nickel aluminum alloy wires, designated . .
.~ "H"j "I" and "W" were first analyzed by wet chem~.cal analysis to determine their chemical makeup in percent by weight, and the result of that analysis is presented as follows~
-~ TABLE VI ..
: . .
.. ~lement: C Mn S Si Ni , . .....
:~ Wire : .
. Sample _ .
I" 0.005 0.23 - 1.68 92.397 .;; "I" 0.040 0.23 - 0.47 93.636 :
; "W" 0.003 0.27 - 1.02 92.~2 .
Element : Ti Cu Al Fe . Wire .: . Sample .:., "Il" .44 0.0~ 5.06 0.108 .. ` "I" .40 0.08 5.05 0.094 . "W" .40 0.72 5.14 0.275 .:,,-,:, .. , , - :
.' ', .
,; ' ": . ' .. .;, -~.................................... 15 . .
.... ~
" .
The test procedures and specimen preparation were performed similar to those described above with reference to Examples I and II, and the respective specimen substrates were formed of aluminum,iron, or copper.
Each of the respective specimen substrates was electric arc sprayed with one of the nickel aluminum alloy wires indicated above as "~ "I" or "~". A Metco electric arc spray yun was used according to the following parameters:
Electrodes: 15 Gage Atomizing air: 92 psi ~-~ Amperage: 260 to 275 amps.
~ Voltage: 34 volts ; The tensile/bond strength of the respective spray coated substrates and the failure mode of each were determined - as above, and the results are presented in following Table VII.
Under the Failure Mode category in the table, the location of the failure and the -type of failure are indicated. For example, "Interfac~/Ad" means that failure occurred at the ; interface between the sprayed coating and the substrate and ~- 20 the failure was in the adhesion of the coating to the substrate.
'~oating/Cohe" means that failure occurred only in the coating itself and the failure was in the cohesiveness or cohesion of ~' the coating material itself. "Epoxy Failure" means that the , .; ~
failure occurred in the epoxy matexial securing the test ; sample to the testing apparatus.
..
...
...
'''' ' :
. ,, . ~
."", , , .: .
~, . .
.
'~:'1 .
. .
'".,;, :', ~. "' ; ' .!.' ~
TABLE VII ::
~ ~ .
TENSILE/BOND :
~T~RIAL STRENGTII
COAT- ACTUAL, A~G., FAILURE MODE
ING SUBST~ATE (psi) ~psi) LOCATION/TYPE
6700 Interface/Ad . Aluminum 56006200 Interface/Ad . 6300 Interfa~eJAd ., _ _ .
. 4800 . Coating/Cohe ; ~ . Iron 5600 4867Coating/Cohe 4200 Coating/Cohe . . _ _ .~ No Test . Copper No Test 2167 . ~.
:l. . 6500 Interface/Ad :
:, . . . _ ~
' : 6700 Interface/Ad :~ Aluminum 6 0 0 05 ~ 67 Interface/Ad .4900 Interface/Ad ." ~
52û0 Coating/Cohe Iron 6500 5733Coating/Cohe ~'~ ~ ` 5500 : Coating/Cohe ~a~ . No Test . Copper No Test . .
.: No Test , .. _ .
.~ . 7000 Epoxy E'ailure ;
Aluminum 8200 7533Epoxy Failure i . 7400 . Interface/Ad ,, . l 5 2 0 0 .Co ating,/Cohe ~'~; W Iron 6500 5733Coating/Cohe $: ~ : 5500 Coating/Cohe ',~ _ No Test Copper No Test i : .
: No Test ~, . _ _ . _ ':"1 .
' -17-.,. ~ .. .
1~ 5~
None of the spraying materials adhered well to the copper substrates. For each of the iron substrates, the failure mode was cohesive in nature, i e., failure occurred due to breaking of the coating rather than separation at the interface.
In all but two of the aluminum coated substrates the failure was of an adhesive nature, i.e., failure occurred at the interface. In two instances of aluminum coated substrates, the failure was at the epoxy coupling used in the test.
; From the results presented in the above table, it will be clear that ~he nickel aluminum alloy wire that is electric arc sprayed to coat smooth surfaces of aluminum and iron substrates will self-bond extremely well to those substrates.
Coating microhardness for each of the specimens including the coated substrates was determined utilizing the rhomboidal ICnoop indentor with a 50 gm load. ~acrohardness was ascertained using . !
a one kilogram load and the Vickers hardness (DPI-I~ tester, the measurements using the latter being converted for facility of comparison to the Rockwell C scale indicated in column :; .
Rc in Table VIII below. The results of the microhardness and macrohardness measurements are presented as follows:
TABLE VIII
TERIAL Rc CON-COATING SUBSTI~ATE l~llN50 DPII YERSION
.. ` _ __ __. .
r~
Aluminum 449 283 27.7 Iron 562 Copper 562 _ . _ - Aluminum 631 316 3I.9 ~: I Iron 618 311 31.2 Copper 605 292 28 9 Aluminum 605 279 27.0 W Iron 670 283 27.7 i Copper 710 293 28.9 ,, ~ . :
l81~5~7 In view of the above two tables presented in this example, it is clear that nickel aluminum alloy wire having varying proportions of Eluxing and hardening agents and some variation in the ratio of nickel to aluminum will exhibit good self-bonding properties when electric arc sprayed onto steel or aluminum substrates. Variations in the ratio of nickel to aluminum and in the additives will not appreciably reduce the bond tenacity. Moreover, by varying or shifting the fluxing and `-hardening additives in the nickel aluminum alloy wire, the hard- -; 10 ness of the resulting sprayed coating is affected.
The microstructure of respective stPel specimens having smooth or ground surfaces onto which the respective nickel aluminum alloy wires "H", "I" and "W" were sprayed was examined.
A photomicrograph taken of the interface of the nickel aluminum alloy wire "I" applied over a hardened, tempered, ground smooth martensltic substrate is illustrated in Fig. 4. The lower and ~`;; ` darker portion of the figure represents the martensite and the : upper lamellar and lighter colored area represents the sprayed i. - coating. Approximately at a location slightly right of the i` 20 center of the igure is a lightened area in the martensite, which is an area of untempered martensite caused, apparently, due to .
the heat of the nickel aluminum coating as it is applied to the martensite.
; EXAMPLE VI
.":.; :
Samples of a nickel aluminum wire feed, as identified ~.' ' .
in Table I above, were electric arc sprayed onto respective steel and aluminu~ substrates and subsequently heat treated as follows:
~;~; Aluminum- 12 hours at 950F., water ,~ quenched, aged 6 hours at 525F.
`~ Steel- 8 hours at 1200F., furnace cooled.
.. .. .
~ ~ ~ ... .
':, , i; ,. , . ~
llQ~10~
Aside from exhibiting excellent resistance to thermal shock the samples displayed higher than normal adhesive strength. When tested in accordance with Example I fracture occurred not in the deposit but rather in the epoxy. Results were as follows:
Aluminum9300 psi 10800 psi ` Steel11200 psi lOgOO psi `
11800 psi ~` :
Thus, the described treating process, including aging, will increase the overall strength of the coating and the coating-substrate bond strength. Therefore, it will be clear that the overall integrity of the deposit or coating may ~e increased by ' heat treatment and/or aging.
While the foregoing examples and discussion have been directed to the electric arc spraying of a nickel aluminum alloy in wire form to coat a smooth substrate in a manner~such that the coating will self-bond to the smooth surface of the ;' substrate, other alloy materials that will self-bond when ' sprayed from an electric arc spray gun also may be used in ;
accordance with the invention. As described above, one such ; materlal is an alloy of nickel and titanium comprised of approxi-mately 40 to 70% by weight nickel and approximately 30 to 60%
by weight titanium and preferably approximately 54 to 56% by ~' weight nickel and approximately 44 to 46~ by weight titanium.
. .. . .
It has thus been found that an alloy of nickel and aluminum in wire form which is electric arc sprayed to coat a clean smooth `~ substrate will self-bond to the substrate without the occurrence ;
of an exothermic reaction. On the other hand pre-alloyed nickel . ~ , , .
.
`
05~
aluminum powder does not bond well to such a substrate when sprayed in a plasma or combustion gas, nor will nickel aluminum .
alloy wire bond well to such a substrate when combustion gas sprayed.
:.
r~loreoverr it also has been found that pre-alloyed nickel aluminum wires when electric arc sprayed exceed the reported property values of composites applied by other thermal spray techniques. Furthermore, electric arc spray rates and deposit efficiencies, especially using the nickel aluminum alloy ~ 10 wire or nickel titanium alloy wire in accordance wlth the ; invention, are appreciably higher yielding of superior deposits at lower costs than thermal spraying synergistic, exothermic r' ' materials.
,;:
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Claims (17)
1. A method of thermal spraying a metallic substrate to deposit a self-bonding coating on such substrate, comprising supplying an electric arc thermal spray gun with a wire feed comprising an alloy of nickel and aluminum or titanium, and using such electric arc thermal spray gun, spraying said wire feed onto such substrate to coat the same thereby to establish a diffusion bond between such coating and such substrate to provide a self-bonding coating on such substrate.
2. A method as set forth in claim 1, wherein said step of supplying comprises supplying a wire feed comprising an alloy of nickel and aluminum.
3. A method as set forth in claim 1, wherein said step of supplying comprises supplying a wire feed comprising an alloy of approximately from 80 to 98 percent by weight nickel and approximately from two to twenty percent by weight aluminum.
4. A method as set forth in claim 1, wherein said step of supplying comprises supplying a wire feed comprising an alloy of approximately from 90 to 95 percent by weight nickel and approximately from four to six percent by weight aluminum.
5. A method as set forth in claim 1, wherein said step of supplying comprises supplying a wire feed comprising an alloy of nickel and titanium.
6. A method as set forth in claim 1, wherein said step of supplying comprises supplying a wire feed comprising an alloy of approximately from forty to seventy percent by weight nickel and approximately from thirty to sixty percent by weight titanium.
7. A method as set forth in claim 1, wherein said step of supplying comprises supplying a wire feed comprising an alloy of approximately from fifty-four to fifty-six percent by weight nickel and approximately from forty-four to forty-six percent by weight titanium.
8. A method as set forth in claim 1, wherein said step of spraying comprises spraying said wire feed onto a smooth, clean substrate of metallic material.
9. A method as set forth in claim 1, further comprising the step of heat treating such coated substrate.
10. An article of manufacture, comprising a metallic substrate and a coating of an alloy of nickel and aluminum or titanium applied to said substrate by supplying to an electric arc thermal spray gun a wire feed comprising an alloy of nickel and aluminum or titanium, and using such electric arc thermal spray gun, spraying said wire feed onto said substrate to coat the same, thereby to establish a diffusion bond between said coating and said substrate, whereby said coating is self-bonding to said substrate.
11. An article as set forth in claim 10, wherein said coating comprises an alloy of nickel and aluminum.
12. An article as set forth in claim 10, wherein said coating comprises an alloy of approximately from eighty to ninety-eight percent by weight nickel and approximately from two to twenty percent by weight aluminum.
13. An article as set forth in claim 10, wherein said coating comprises an alloy of approximately from ninety to ninety-five percent by weight nickel and approximately from four to six percent by weight aluminum.
14 . An article as set forth in claim 10, wherein said coating comprises an alloy of nickel and titanium.
15. An article as set forth in claim 10. wherein said coating comprises an alloy of approximately from forty to seventy percent by weight nickel and approximately from thirty to sixty percent by weight titanium.
16. An article as set forth in claim 10, wherein said coating comprises an alloy of approximately from fifty-four to fifty-six percent by weight nickel and approximately from forty-four to forty-six percent by weight titanium.
17. An article as set forth in claim 10, wherein said coated substrate is heat treated.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA271,665A CA1081057A (en) | 1977-02-14 | 1977-02-14 | Spray bonding of nickel-aluminum and nickel-titanium alloys |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA271,665A CA1081057A (en) | 1977-02-14 | 1977-02-14 | Spray bonding of nickel-aluminum and nickel-titanium alloys |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1081057A true CA1081057A (en) | 1980-07-08 |
Family
ID=4107922
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA271,665A Expired CA1081057A (en) | 1977-02-14 | 1977-02-14 | Spray bonding of nickel-aluminum and nickel-titanium alloys |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1081057A (en) |
-
1977
- 1977-02-14 CA CA271,665A patent/CA1081057A/en not_active Expired
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