Glossary

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Adhesive

A material that resists adhesion. A film or coating applied to surfaces to prevent sticking, such as a parting or mold-release agent.

 

Abradable coating

The sacrificial member of a two-component clearance control (gas path seal) system, usually applied to a static component.

 

Abrasion

(1) a roughening or scratching. (2) grinding or wearing away using abrasives.

 

Abrasion rate

The rate at which material is removed from a surface during abrasion. Usually expressed in terms of (1) thickness removed per unit of time or traversed distance, and (2) mass removed per unit of time or distance travelled.

 

Abrasion resistance

The ability of a material to resist surface wear.

 

Abrasive

(1) a hard substance used for grinding, honing, lapping, superfinishing, polishing, pressure blasting, or barrel finishing. Typical materials include alumina, silicon carbide, boron carbide, diamond, cubic boron nitride, garnet, and quartz. (2) hard particles that wear away a surface when moved across it.

 

Abrasive blasting

A process for cleaning, finishing, or roughening with an abrasive under high pressure. See preferred term blasting or blast cleaning.

 

Abrasive wear

Removal of material by particles moving across a surface. The particles may be loose or part of another surface in contact with the surface being worn. Compare with adhesive wear.

 

Acetylene (C2H2)

Unsaturated aliphatic hydrocarbon gas used as a fuel in combustion gas flame spraying.

 

Acoustical room

A soundproof enclosure containing thermal spraying and sometimes auxiliary equipment. Its purpose is to reduce or isolate unacceptable operating noises from the surrounding environment.

 

Adhere

To cause two surfaces to be held together by adhesion.

 

Adherence

The attachment of a material or coating to a surface (either by adhesion or other means). See also adhesion.

 

Adhesive

A substance used to hold bodies or materials together. The word is a general term used to include the following: cement, glue, mucilage, and paste. The terms are often used interchangeably.

 

Adhesive bond

Attractive forces between a coating and the substrate.

 

Adhesive wear

Wear by transference of material from one surfaceto another due to solid-phase welding. Particles removed

From one surface are permanently or temporarily attached to the other surface. Compare with abrasive wear.

 

Air cap

A device for forming, shaping, and directing an air patternfor the atomization of wire or ceramic rod during spray

 

Air filter

Mechanism for cleaning air of such contaminants aswater, oil, and solid matter.

 

Anode

The positive electrode in a thermal spray device. In aplasma thermal spray gun, it is the front electrode, often thenozzle. In electric arc spray guns, one feed wire guide is the positiveelectrode.

 

Arc

A luminous discharge of electrical current crossing the gapbetween two electrodes.

 

Arc chamber

The confined space within the plasma thermalspray gun enclosing the anode and cathode in which the arc is struck.

 

Arc plasma

See plasma.

 

Arc voltage

The voltage across the arc.

 

Arc wire spraying

See preferred term electric arc spraying.

 

Assembly

A number of parts or subassemblies combined orjoined together.

 

As-sprayed

The condition of the thermal sprayed coating andwithout subsequent thermal, mechanical, or chemicalprocessing.

 

Atomization

The division of molten materialat the end of the wire or rod into fine particles.

 

Atomizer

A device that atomizes a sample. See also atomization

Backfire

The momentary recession of the flame into the flamespray gun tip, followed by immediate reappearance or completeextinction of the flame.

 

Biomaterials

A group of materials suited for implantation intoliving tissue. The materials may be either organic or inorganic.

 

Blasting or blast cleaning

A process for cleaning or rougheningmetal objects with an air blast or centrifugal wheel that forciblydirects abrasive particles against the workpiece.

 

Bond

The junction between the coating and the substrate, or itsstrength. See also adhesive bond, mechanical bond, and metallicbond.

 

Bond coat

A preliminary (or prime) coat of material thatimproves adherence of the subsequently sprayed deposit.

 

Bonding

The joining together of two materials.

 

Bond strength

The force required to pull a coating free of itssubstrate. Usually expressed in megapascals (MPa) or poundsper square inch (psi).

 

Brazing

A group of welding processes for joining materials byheating them to a suitable temperature and using a filler metal with a liquidus above 450 °C (840 °F) and below the solidus ofthe base materials. The filler metal is distributed between thesurfaces of the joint by capillary attraction.

 

Brinell hardness number (HB)

A number related to the appliedload and to the surface area of the permanent impression madeby a ball indenter.

 

Buildup

The construction or fabrication of a coating.

 

Buildup sequence

The order in which the passes of a multiplepassspray process are deposited. See also spraying sequence.

Carrier gas

The gas used to convey powdered materials from thepowder feeder to the spray gun.

 

Cathode

The negative electrode of an electrolytic cell. In aplasma generator, it is the rear electrode.

 

Ceramics

Any of a class of inorganic nonmetallic productsthat are subjected to a high-temperature exposure duringmanufacture or use (approximately 540 °c, or 1000 °f). Typically,but not exclusively, a ceramic is a metallic oxide, boride,carbide, or nitride, or a mixture of such materials. See alsoadvanced ceramics and refractory materials.

 

Ceramic-metal coating

A mixture of a ceramic material with ametallic phase.

 

Ceramic rod flame spray gun

A flame spraying device whereinan oxyfuel gas flame provides the heat, and the surfacing materialto be sprayed is in ceramic rod form.

 

Ceramic rod flame spraying

A spraying process in which thematerial to be sprayed is in ceramic rod form. See also flamespraying.

 

Ceramic rod speed

The length of ceramic rod sprayed in a unitof time.

 

Coating

A layer of material applied by thermal spraying for thepurpose of corrosion prevention, resistance to high-temperaturescaling, wear resistance, lubrication, or other purposes.

 

Coating density

The ratio of the determined density of a coatingto the theoretical density of the material used in the coatingprocess. Usually expressed as percent of theoretical density.

 

Coating strength

A measure of cohesive bonding within a coating,as opposed to coating-to-substrate bonding (adhesivestrength); coating tensile strength is usually expressed in kilopascals(KPa) or pounds per square inch (Psi).

 

Coating stress

The stresses in a coating resulting from rapidcooling and solidification of molten material or semimolten particlesas they impact the substrate. Coating stresses are a combinationof body and textural stresses.

 

Cohesion

The state in which the particles of a thermal spray coatingare bound together either mechanically or metallurgically.

 

Cold spray

A kinetic spray process using supersonic jets of compressedgas to accelerate near-room-temperature powder particlesat ultrahigh velocities. The unmelted particles, traveling atspeeds between 500 to 1500 m/s (1600 to 5000 ft/s), plasticallydeform and consolidate on impact with their substrate to create a coating.

 

Control console

The instrumented unit from which the spray gunis operated and the operating variables are monitored and controlled.

 

Cored wires or rods

Multicomponent composite wire consistingof an outer sheath surrounding one or more powdered metal/ceramic/plastic elements.

 

Corrosion

The chemical or electrochemical reaction between amaterial, usually a metal, and its environment that produces adeterioration of the material and its properties.

 

Corrosion rate

Corrosion effect on a metal per unit of time. Itmay be expressed as corrosion depth per unit of time (penetrationrate, for example, mils/yr) or the mass of metal turned intocorrosion products per unit area of surface per unit of time(weight loss, for example, g/m2/yr). Corrosion rate reportsshould contain information on the type, time dependency, andlocation of the corrosion effect.

 

Corrosion resistance

The ability of a material to withstand contactwith ambient natural factors or those of a particular, artificiallycreated atmosphere, without degradation or change inproperties. For metals, this could be pitting or rusting; fororganic materials, it could be crazing.

 

Coupon

A piece of material from which a test specimen is to beprepared. A coupon will experience the same processing stepsas the part it represents.

 

Cycle

The time required to achieve a final coating. Includescleaning, masking, roughening, positioning, spraying, clean up,and finishing.

Deposition efficiency (DE)

The ratio, usually expressed in percent,of the weight of spray deposit to the weight of the materialsprayed.

 

Deposition rate

The weight of material deposited in a unit oftime. It is usually expressed as kilograms per hour (kg/h) orpounds per hour (lb/h).

 

Deposition sequence

The order in which the increments ofsprayed material are deposited.

 

Distortion

Any deviation from an original size, shape, or contourthat occurs due to the application of stress or the release ofresidual stress.

Electric arc spraying

A thermal spraying process in which anelectric arc is struck between two consumable electrodes of acoating material. Compressed gas is used to atomize and propelthe material to the substrate.

 

Electrochemical corrosion

Corrosion that is accompanied by aflow of electrons between cathodic and anodic areas on metallicsurfaces.

 

Electrocorrosive wear

Wear of a solid surface that is acceleratedby the presence of a corrosion-inducing electrical potentialacross the contact interface. Moisture from the air can facilitatethis type of corrosion wear when a galvanic couple exists andthe contacting materials are sufficiently reactive.

 

Electrode

In arc and plasma spraying, the current-carrying componentsthat support the arc. See also anode and cathode.

 

Electrode cable

Same as electrode lead.

 

Electrode holder

A device used for mechanically holding theelectrode while conducting current to it.

 

Electrode lead

The electrical conductor between the electricalsource and the electrode holder.

 

Erosion

(1) loss of material from a solid surface due to relativemotion in contact with a fluid that contains solidparticles. (2)progressive loss of material from a solid surface due to mechanicalinteraction between that surface and a fluid, a multicomponentfluid, an impinging liquid, or solid particles. (3) loss ofmaterial from an electrical contact surface due to an electricaldischarge (arcing).

Feed hopper

A container used for holding and metering powder for delivery to the spray device.

 

Feeding

Conveying powder or wire to the thermal spray gun.

 

Feed lines

Hoses that convey powder to the spray device.

 

Feed rate

The rate at which material passes through the spraydevice in a given length of time. A synonym for spray rate.

 

Feedstock

Any consumable form of spray material used in theapplication of a coating.

 

Ferrous

Metallic materials in which the principal component isiron.

 

Flame spraying

Thermal spraying in which a coating material isfed into an oxyfuel gas flame, where it ismelted. Compressedgas may or may not be used to atomize the coating material andpropel it onto the substrate. The sprayed material is originally inthe form of wire or powder. The term “flame spraying” is usually used when referring to a combustion-spraying process, as differentiated from plasma spraying.

 

Flow

The volume or weight of a gas or spray material in a givenlength of time. Generally expressed as cubic feet per hour(cfh), liters per minute (l/min), and pounds per hour (lb/h).

 

Flow meter

A device for indicating the rate of gas flow in a system.

 

Flow rate

The time required for a powdered material sample ofstandard weight to flow through an orifice in a standard instrumentaccording to a specified procedure.

 

Fusion

The melting together of sprayed metal and base metal(substrate), or of sprayed metal only.

Gas atomization

An atomization process whereby molten metalis broken up into particles by a rapidly moving gas stream. Theresulting particles are nearly spherical, some with attachedsatellites.

 

Gas flow rate

The quantity of gas delivered or used during a thermalspray or grit-blasting operation.

 

Grit

Crushed ferrous or nonmetallic abrasive material in variousmesh sizes used in abrasive blasting to clean and/or roughensurfaces.

 

Grit blasting

Abrasive blasting with small, irregular pieces ofsteel, malleable cast iron, or hard, nonmetallic materials.

 

Grit size

Nominal size of abrasive particles in blasting mediaand/or a grinding wheel, corresponding to the number of openingsper linear inch in a screen through which the particles canpass. Usually expressed by Society of Automotive Engineersnumbers, such as SAEG25.

 

Gun extension

Tubes of various lengths containing the nozzleand attached to the front of a thermal spraying device to permitspraying within confined areas or deep recesses.

High-velocity oxyfuel (HVOF) process

A flame spray processthat takes place at very high pressures and combustion jet temperatures.

 

Hot corrosion

Accelerated metal surface corrosion resultingfrom the combined effects of oxidation and reactions with contaminantsto form a molten salt on the metal that fluxes,destroys, or disrupts the normal protective oxide.

Impact wear

Wear of a solid surface resulting from repeated collisionsbetween that surface and another solid body.

 

Impingement

A succession of impacts between liquid or solidparticles and a solidsurface.

 

Impingement angle

See preferred term spray angle.

 

Inert gas

A gas that is stable, does not support combustion, anddoes not form reaction products with other materials. Includedare helium, argon, and sometimes nitrogen.

Lubricant

Any substance interposed between two surfaces forthe purpose of reducing the friction or wear between them.

Manual spraying

Spraying wherein the thermal spray device ishand held by the operator, who also inputs its operating parameters.

 

Mask

A device for protecting a surface from the effects of blastingand/or coating. Masks are generally either reusable (permanent)or disposable.

 

Masking tape

A tape used as a stopoff or deterrent to grit-blastroughening and/or the adherence of thermal spray particles.Tapes are generally of a disposable nature.

 

Mass flow controller

A device for metering and controlling theamount/mass (not volume) of gas fed to the spray gun or powderfeed system.

 

Mechanical testing

Methods by which the mechanical propertiesof a coating or material are determined.

 

Mechanical wear

Removal of material due to mechanicalprocesses under conditions of sliding, rolling, or repeatedimpact. The term includes adhesive wear and abrasive wear.Compare with corrosive wear and thermal wear.

 

Melting point

Temperature at which a pure metal, compound, oreutectic changes from solid to liquid; the point that the liquidand the solid are at equilibrium.

 

Metal arc spraying

See preferred term electric arc spraying.

 

Metal cored wire

A composite filler metal wire consisting of ametal tube or other hollow configuration containing alloying ingredients. Minor amounts of additive ingredients facilitate arcstabilization and oxide fluxing.

 

Metallizing

Forming a thermal spray coating using wire. Seepreferred terms wire flame spraying or electric arc spraying.

 

Metal powder

Material consisting of metallic particles, usuallyin the size range of 0.1 to 1000 µm.

 

Metal spraying

Fabrication by depositing plasticized and/ormolten metal onto a suitable substrate. See also thermal sprayingand flame spraying.

Oxidative wear

A corrosive wear process in which chemicalreaction with oxygen results in a loss of material, or where anoxidizing environment predominates.

Parameter

Any one of a group of thermal spray process variablesor operating conditions. Usually refers to spray gun settingsand target manipulation.

 

Plasma spraying

A thermal spraying process in which a non-transferredarc is a source of heat that ionizes a gas that meltsthe coating material and propels it to the workpiece.

 

Powder

Material manufactured into finely divided particles.When explicitly blended for thermal spraying, powder fallswithin a specific mesh range, usually finer than 120 mesh.

 

Powder feeder

A mechanical device designed to introduce acontrolled flow of powder into the spray device.

 

Powder feed gas

See preferred term carrier gas.

 

Powder feed rate

The quantity of powder introduced into thehot, gaseous stream per unit of time. Expressed in pounds/hour(lb/h) or grams/minute (g/min).

 

Powder flame spraying

A thermal spraying process in which thematerial to be sprayed is in powder form. See also flame spraying.

 

Powder injection

Feeding of a powder through a powder portinto a thermal spray flame or plasma stream.

 

Powder injection angle

Angle at which powder is introduced tothe flame or plasma.

 

Powder port

Internal or external device through which powderis injected into the flame or plasma stream.

 

Propane (C3H8)

A colourless fuel gas used in flame spraying; it isfound in natural gas.

 

Propylene (C3H6)

A fuel gas used in flame spraying, particularlyhigh-velocity oxyfuel. It is derived frompetroleum hydrocarboncracking.

Rectifier

An electrical device for converting alternating currentto direct current.

 

Robotic spraying

The use of a computerized, articulated, or multiaxismanipulation mechanism to traverse the spray gun and/ortarget during coating application.

 

Roughness

(1) relatively finely spaced surface irregularities, theheights, widths, and directions of which establish the predominantsurface pattern. (2) the microscopic peak-to-valley distancesof surface protuberances and depressions. See also surfaceroughness.

Sandblasting

Abrasive blasting with sand. See also blasting orblast cleaning.

 

Self-bonding materials

Those materials that form a metallurgicalbond with the substrate in the as-sprayed condition.

 

Self-fluxing alloys

Certain materials that “wet” the substrate andcoalesce when heated to their melting point, without the additionof a fluxing agent. The alloys usually contain temperaturesuppressants such as boron and/or silicon.

 

Shielding gas

During spray application, a stream of inert gasdirected at the substrate and spray stream to provide an atmosphericbarrier and minimize oxidation.

 

Shotblasting

(1) blasting with round metal shot to remove millscale more rapidly or more effectively than done by sandblasting.See also shot peening.

 

Shot peening

Cold working of metals by the impingement of astream of shot, directed at the metal surface at high velocityunder controlled conditions. This produces compressivestresses in the metal surface, resulting in an increase in fatiguestrength.

 

Sliding wear

The motion of two moving bodies in which theirsurface velocities, at the point of contact, are different withregard to magnitude and/or direction.

 

Spray

A moving mass of dispersed liquid droplets or heat-softenedparticles.

 

Sprayability

Material attribute enabling it to be readily passedthrough a spray device without degradation and be depositedonto a prepared substrate.

 

Spray angle

The angle of particle impingement, measured fromthe surface of the substrate to the axis of the spraying nozzle.

 

Spray booth

See preferred term exhaust booth.

 

Spray chamber

An enclosure in which spraying is confined. Itgenerally contains a protective atmosphere.

 

Spray deposit

A coating applied by any of the thermal spraymethods. See also thermal spraying.

 

Spray distance

During spraying, the distance maintainedbetween the spray gun nozzle tip and the workpiece surface.

 

Spray drier

A vessel into which an aqueous powder slurry issprayed through injection ports, atomized, andhurled into aheated gas stream in which it is dried. The dried droplets aretypically tiny, spherical, free-flowing agglomerates.

 

Spray forming

The fabrication of free-standing shapes bydepositing a material onto a mandrel, or other host surfaces, andremoving the spray deposit after achieving the desired thickness.

 

Spray fuse

Processing in which a coating is deposited and subsequentlyfused by heating.

 

Spraying sequence

The order in which different layers of materialare applied in a planned relationship, such as overlapped,superimposed, or at certain angles.

 

Spray metallizing

See preferred term metallizing.

 

Spray nozzle

(1) in atomizing metal powders, an orifice throughwhich molten metal passes, forming a stream that is disintegratedby a gas, a liquid, or by mechanical means. (2) in spraydrying, the head in which the injector ports are located.

 

Standoff distance

See preferred term spray distance.

 

Substrate

The material, workpiece, or substance on which the

Coating is deposited.

 

Substrate preparation

The set of operations, including cleaning,degreasing, and roughening, applied to the base materialprior to applying a coating; intended to ensure adequate bondingof the coating.

 

Substrate temperature

The temperature attained by the basematerial as the coating is applied.

 

Subsurface corrosion

Formation of corrosion products beneatha metal surface.

 

Surface finish

Condition of a surface as a result of a final treatment.

 

Surface grinding

Producing a plane surface by grinding.

 

Surface integrity

Technology that involves the specification andmanufacture of unimpaired or enhanced surfaces through thecontrol of the manufacturing process.

 

Surface modification

Any alteration of a surface.

 

Surface preparation

The operations necessary to produce adesired or specified surface condition.

 

Surface roughness

Fine irregularities in the surface texture of acoating or material. It is usually reported as the arithmeticroughness average, Ra, and is given in micrometers ormicroinches.

Tensile stress

A stress that causes two parts of an elastic body, oneither side of a typical stress plane, to pull apart. Contrast withcompressive stress.

 

Thermal barrier coating (tbc)

Two or more layers of sprayedcoating in which the initial coating that is closest to the substrateis a metal, generally a MCrAlY, and provides hot corrosion/oxidationprotection as well as performing the function of a bondcoat. Its coefficient of thermal expansion is generally tailored tomatch that of the host metal. Subsequent layers may be whollyrefractory oxides or mixes of the metal and the ceramic. A tbcis a thermally insulating coating system protecting the substratefrom the higher temperatures and corrosive products of the surroundingenvironment.

 

Thermal conductivity

The ability of a material to conduct heat.

 

Thermal cycling

The cyclic change in thermal environment.

 

Thermal decomposition

Decomposition of a compound into itselemental species at elevated temperatures.

 

Thermal expansion

Change in length of a material with a changein temperature. See also coefficient of thermal expansion.

 

Thermal fatigue

Fracture resulting from the presence of temperaturegradients that vary with time in such a manner as to producecyclic stresses.

 

Thermal resistance

A measure of the ability of a body to preventheat from flowing through it, equal to the difference betweenthe temperatures of opposite faces of the body divided by therate of heat flow. Also known as heat resistance.

 

Thermal shock

Development of a steep temperature gradient andaccompanying high stresses within a material or structure.

 

Thermal spray gun

A device for heating, feeding, and directingthe flow of a thermal spray material.

 

Thermal spraying

A group of coating processes in which finelydivided metallic or nonmetallic materials are deposited in amolten or semimolten condition to form a coating. The coatingmaterial may be in the form of powder, ceramic rod, wire, ormolten materials.

 

Thermal spraying deposit

The coating or layer of surfacingmaterial applied by a thermal spraying process.

 

Thermal spray powder

A metal, carbide, plastic, or ceramicpowder designed for use in thermal spray operations.

 

Thermal stresses

Stresses in a material resulting from nonuniformtemperature distribution.

 

Thermal wear

(1) material removal by softening, melting, orevaporation during sliding or rolling. (2) transfer of atomsfrom one body to another at elevated temperatures.

 

Torch

A device used for fusing sprayed coatings; it mixes andcontrols the flow of gases.

Vickers hardness number (HV)

A number related to theapplied load and the surface area of the permanentimpressionmade by a diamond indenter having included face angles of 136°

Wear

Surface damage involving a progressive loss of materialdue to relative motion between it and a contacting surface orsubstance.

 

Wear debris

Particles that become detached in a wear process.

 

Wear rate

Rate of material removal or dimensional change dueto wear per unit of exposure, for example, quantity of materialremoved (mass, volume, thickness).

 

Wear resistance

Resistance of a body to removal of material bya wear process. It is a function of the conditions under whichwear takes place and should be specified.

 

Wear scar

The portion of a surface that exhibits evidence thatmaterial has been removed from it due to wear.

 

Wire arc spraying

See preferred term electric arc spraying.

 

Wire feed speed

Rate of speed in millimeters per second (mm/s)or inches per minute (in./min) in which a filler metal is consumedduring spray.

 

Wire flame spray gun

A flame spraying device using an oxyfuelflame to provide the heat; the spray material is in wire or rod

Form. See also wire flame spraying.

 

Wire flame spraying

Spray process in which the feed stock is inwire or rod form. See also flame spraying.

 

Wire metallizing

See preferred term wire flame spraying.

 

Wire straightener

Device for controlling the cast of coiled metalwire, enabling it to be readily fed into the wire spray gun.

 

Work distance

The defined distance between the substrate surfaceand the nozzle of the spray gun.