A to Z of Terms related to the Thermal Spray Process and Surface Engineering
- Abradable coatings
- Coatings which are designed to be abraded by a mating surface to form a tight gas or air seal, while retaining good erosion resistance.
- Abrasive blasting
- A process for cleaning and roughening a surface by means of an abrasive directed at high velocity against the work piece.
- Abrasive Wear
- Wear due to hard particles or hard protuberances forced against and moving along a solid surface.
- Acetylene C2H2 (ethyne)
- Unsaturated aliphatic hydrocarbon gas. Used as a fuel gas in combustion thermal spray processes, welding and cutting. Acetylene has the highest flame temperature and requires the smallest amount amount of oxygen to form a neutral flame.
- Acoustic emission
- Acoustic emissions are sound or ultrasound pulses generated during crack initiation or propagation in materials and coatings as a result of being subjected to stress. Acoustic emissions can be detected by transducers.
- Adhesive Wear
- Wear due to localized bonding between contacting solid surfaces leading to material transfer between the two surfaces or the loss from either surface.
- Several particles adhering together.
- Agglomerated powder
- A powder made up of agglomerates
- Air classification
- The separation of powder into particle size fractions by means of an air stream of controlled velocity.
- Aluminising (gas)
- High temperature (approx. 900oC) pack or gaseous diffusion of aluminium into the surface of a component to enhance high temperature corrosion and oxidation resistance.
- Alkyd resin
- A type of polyester resin used in paints and other surface coatings. The original alkyd resins were made by co-polymerising phathalic anhydride with glycerol, to give a brittle cross. Linked polymer.
- Aluminising (hot dip)
- An aluminium coating process based on submersion in liquid metal, usually with a strip steel product being continuously fed through the bath. Provide galvanic corrosion protection.
- Aluminising (Thermal Spray Method)
- Thermal sprayed coatings of aluminium usually on substrates of steel or nickel chromium alloys which are subsequently heat treated to aluminise the surface.
- Aluminium Ion Plating
- The deposition of aluminium by a vacuum evaporative process. Provides galvanic corrosion resistance. Normally given a passivation treatment.
- non-crystalline, or devoid of regular structure.
- A negatively charged ion
- Positively charged electrode (nozzle in plasma gun) - the electrode of an electrolytic cell at which oxidation is the principle reaction. (Electrons flow away from the anode in the external circuit. Its usually the anode where corrosion occurs and metal ions enter solution.)
- Anodic coating
- A coating that becomes the anode in an electrochemical cell with the substrate (cathode). The only metals in common use for thermal spraying which are anodic to iron and steel are zinc and aluminium.
- The production of an oxide layer on aluminium alloys. The process is electrolytic, a typical electrolyte being sulphuric acid. Treatment at room temperature produces thin, decorative layers with some corrosion protection. Treatment at 0oC produces hard, thicker layers (up to 100µ) with wear resistance. They can be post sealed to give improved corrosion resistance.
- Apparent density
- The weight of a unit volume of powder or coating
- Apparent hardness
- The value obtained by testing a coating or sintered material with standard indentation hardness equipment. (See macrohardness) Since the reading reflects a composite of pores and solid material, (which may be particles relatively poorly bonded together) it is usually lower than that of an equivalent solid wrought or cast material. Not to be confused with particle hardness (See microhardness).
- Atmosperic Plasma Spray Proces.
- Arc Wire Spraying
- A thermal spray process where two electrically conducting wires are brought together to form an electric arc. Molten material formed in the arc is projected by a compressed gas stream towards the work piece to form a coating.
- Argon (Ar)
- Monatomic noble gas, atomic number 18, one of the most inert elements. Commonly used as a primary plasma gas in the plasma spraying process and providing inert environments for many processes.
- The dispersion of a molten material into particles by a rapidly moving gas or liquid stream or by mechanical dispersion.
- Atomised powder
- A powder produced by the dispersion of a molten material into particles by a rapidly moving gas or liquid stream or by mechanical dispersion.
- The production of a stable, protective oxide on steel parts by treatment in a pressurised, high temperature steam containing atmosphere.
- A cementing medium used in producing composite or agglomerate powders.
- A pressurised stream of particulates (ceramic, plastic, metal, etc.) applied on a surface to clean, peen or abrade.
- Blended Powder
- A powder consisting of two or more different powder materials thoroughly mixed.
- This represents the state of adhesion between the coating and the substrate. It's strength will depend on the details of the spraying process and the materials used. Bonding mechanisms may be mechanical, physical, chemical or metallurgical or a combination of these.
- Bond coat
- A coating applied as an intermediary between the main or top coating and the substrate in order to improve the bond strength and/or to provide a corrosion or oxidation barrier.
- Bond strength
- The strength of the adhesion between the coating and the substrate. A number of test methods are in use to measure the bond strength of coatings.
- The diffusion of boron into the surface of a component (usually steel) by a high temperature (approx. 900oC) gas or pack process. Produces hard phases within the surface (Typically 100µm deep).
- Cadmium plating
- The electrolytic deposition of cadmium to provide galvanic corrosion protection. Restricted by environmental considerations.
- Cadmium ion plating
- The deposition of cadmium by a vacuum process to provide galvanic corrosion protection.
- Similar to Carburising. Diffusion of carbon and nitrogen at about 900oC (by pack, gas, salt bath or plasma process) into low carbon steel, followed by quenching and tempering to produce martensitic case (typically 1mm thick).
- Carburising (also called Case Hardening)
- Diffusion of carbon at about 900oC (by pack, gas, salt bath or plasma process) into low carbon steel, followed by quenching and tempering to produce martensitic case (typically 1mm thick).
- Carrier gas
- Usually nitrogen or argon gas that carries powder into the thermal spray process.
- See Carburising
- Negatively charge electrode. Electrode of an electrolytic cell at which reduction is the principle reaction. (Electrons flow towards the cathode in the external circuit.) Cathodic coating Coatings which become the cathode in an electrochemical
cell with the substrate (anode). This type of coating protects the substrate from corrosion only by being a complete barrier. If the coating allows the environment to reach the substrate, accelerated corrosion of the substrate will occur.
- Cathodic protection
- A technique to reduce the corrosion rate of a metal by making it the cathode of an electrochemical cell. Thermal spray zinc and aluminium coatings provide this protection to steel substrates, the coating being the anode and the steel being the cathode.
- A positively charged ion.
- The formation and rapid collapse within a liquid of cavities or bubbles that contain vapour or gas or both.
- Cavitation Erosion
- A form of erosion causing material to be removed by the action of vapour bubbles in a very turbulent liquid.
- Cermet powders
- A blended or composite powder of metal and ceramic constituents.
- Chemical conversion coating
- A protective or decorative non-metallic coating produced in situ by chemical reaction of a metal with a chosen environment. (It is often used to prepare the surface prior to the application of an organic coating.)
- Chemical Vapour Deposition (CVD)
- The deposition of a coating by means of a chemical reaction in gases in a chamber producing components which deposit on and adhere to the substrate.
- Chromate conversion is a process which completely degreases and removes all traces of the oxide film, replacing it by immersion with a chromate coating which can then be painted. It is used as a post-treatment for cadmium, zinc and aluminium coatings
- High temperature (approx. 900oC) pack or gaseous diffusion of chromium into the surface of a component to enhance high temperature corrosion and oxidation resistance.
- The application of a thick (generally above 1mm) coating which melts or diffuses into the substrate. Processes include weld cladding and plasma transferred arc (PTA).
- The application of a layer of material onto the surface of a substrate.
- Cold welding
- Cohesion between two surfaces of a metal, generally under the influence of externally applied pressure at room temperature.
- Cold Spray
- or cold gas-dynamic spraying process uses the energy stored in high pressure compressed gas to propel fine powder particles at very high velocities at a substrate to form a coating.
- Mixture of two or more materials. Nearly all have a reinforcing material (metal, wood, glass, etc.), called filler, and a natural or artificial resin, called matrix to achieve specific characteristics and required properties.
- Composite Coating
- Mixture of two or more materials. Many thermal spray coatings could be considered as composites.
- Composite Powder
- A powder in which each particle consists of two or more distinct materials joined together.( Not the same as a powder blend.)
- Chemical or electrochemical reaction between a material and it's environment which results in deterioration in the properties of the material.
- Corrosion fatigue
- The process in which a metal fractures prematurely underconditions of simultaneous corrosion and repeated cyclic loading at lower stress levels or fewer cycles than would be required in the absence of the corrosive environment.
- Corrosion potential
- The potential of a corroding surface in an electrolyte relative to a reference electrode measured under open circuit conditions.
- Corrosive wear
- Wear in which chemical or electrochemical reaction with the environment is significant.
- Crevice corrosion
- Localized corrosion of a metal surface at, or immediately adjacent to, an area that is shielded from the full exposure to the environment because of close proximity between the metal and the surface of another material.
- Crushed powder
- Powder formed from a solid which is then crushed to the appropriate size for spraying.
- Copper plating
- The electrolytic deposition of copper to provide either a
corrosion barrier (often as an undercoat for hard chrome plate) or for reclamation of worn parts.
- See Chemical Vapour Deposition
- The removal of grease and oil from a surface. Degreasing by immersion in liquid organic solvents or by solvent vapours condensing on the parts to be cleaned.
- Deposit corrosion
- Localized corrosion under or around a deposit or collection of material on a metal surface. (See also crevice corrosion.)
- Detonation Gun
- A thermal spray process in which the coating material is heated and accelerated to the work piece by a series of detonations or explosions from oxy-fuel gas mixtures.
- Diamond-like Carbon
- A thin carbon-based coating applied by either PVD or PACVD. It has high hardness and low friction.
- Diffusion Coating
- An alloy coating produced by applying heat to one or more coatings deposited on a basis metal.
- The ability of a material to deform plastically without fracturing.
- Electrochemical cell
- An electrochemical system consisting of an anode and a cathode in metallic contact and immersed in an electrolyte. (The anode and cathode may be different metals or dissimilar areas on the same metal surface.
- Electroless Nickel
- The autocatalytic deposition of nickel/phosphorous and nickel/boron have many useful corrosion and tribo/corrosion applications. Unlike the electrolytic processes, they produce a deposit with completely uniform coverage. In the case of Ni P, deposits around 25 to 50 microns thick with a hardness of about 500Hv is obtained, but thermal ageing at temperatures around 400°C can develop hardness values in excess of 1000Hv.
- A conducting medium in which the flow of current is accompanied by movement of matter. A substance that is capable of forming a conducting liquid medium when dissolved or melted.
- Production of chemical changes of the electrolyte by the passage of current through an electrochemical cell.
- Electromotive Force Series (EMF Series)
- A list of elements arranged according to their standard electrode potentials, with "noble" metals such as gold being positive and "active" metals such as zinc being negative.
- The property of certain materials that enables them to return to their original dimensions after an applied stress.
- The electrodeposition of an adherent metallic coating upon an electrode for the purpose of securing a surface with properties or dimensions different from those of the substrate material.
- The severe loss of ductility or toughness or both, of a material, usually a metal or alloy.
- Removal of material from a surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid, or impinging liquid or solid particles
- Associated action involving corrosion and erosion in the presence of a corrosive substance.
- A roughened surface produced by chemical, electrochemical or mechanical means. To dissolve unevenly a part of the surface of a material to highlight microstructure in metallography.
- Corrosion that proceeds laterally from the sites of initiation along planes parallel to the surface, generally at grain boundaries or coating interfaces, forming corrosion products that force metal or coating away from the body of the material, giving rise to a layered appearance.
- Exothermic reaction or material
- Certain materials undergo chemical reactions when thermally sprayed and produce extra heating. This can be useful in improving adhesion of the coating to the substrate.
- A cumulative effect causing a material to fail after repeated applications of stress none of which exceeds the ultimate tensile strength. The fatigue strength (or fatigue limits) is the stress that will cause failure after specified number cycles.
- Fatigue wear
- Wear of a solid surface caused by fracture arising from material fatigue.
- The portion of a powder composed of particles which are smaller than the specified size
- Flame hardening
- The localised surface heating of a medium carbon steel by an impinging gas flame so that the temperature is raised above 900oC. The part is quenched (or self-quenches by virtue of the remaining cool bulk of the component) and tempered to produce a hard martensitic structure at the surface.
- Flame spraying
- A thermal spraying process in which the particles are heated and accelerated in a flame (combustion flame, plasma flame). Old term for thermal spray process.
- A solid inert material added to a synthetic resin or rubber, either to change its physical properties or simply to dilute it for economy.
- Small amplitude oscillatory motion, usually tangential, between two solid surfaces in contact.
- Fretting corrosion
- A form of fretting wear in which corrosion plays a significant role.
- Fretting wear
- Wear arising as a result of fretting (see fretting).
- The reaction force resulting from surface interaction and adhesion during sliding. The friction Coefficient is defined as the friction force divided by the load.
- Fused coatings
- A process in which the coating material is deposited by thermal spraying and then fused by post heat treatment. This can be done by flame, induction heating, furnace or by laser.
- Fused and crushed powder
- Powder formed from a fused solid mass which is then crushed to the appropriate size for spraying.
- Damage to the surfaces of materials sliding in contact with each other, usually caused by the localised welding together of high spots. Common for materials like stainless steel, aluminium alloys and titanium.
- Galvanic corrosion
- Accelerated corrosion of a metal because of an electrical contact with a more noble metal or nonmetallic conductor in a corrosive electrolyte.
- Galvanic Series
- A list of metals and alloys arranged according to their relative corrosion potentials in a given environment.
- Gas carburising
- See Carburising
- Gas flow rate
- The flow rate of gas (e.g. litres per minute) through the spraying torch.
- Gas nitriding
- see Nitriding
- Gas nitrocarburising
- See Nitrocarburising
- A hot dip process for deposition of zinc for galvanic corrosion protection of steel.
- Gold plating
- The electrolytic deposition of gold for decorative or electrical applications.
- Granular powder
- Particles having approximately equidimensional nonspherical shapes.
- The removal of material by the use of fixed abrasives like grinding wheels or emery paper.
- Grit blasting
- A pressurised stream of hard metal or oxide grit material used to clean and roughen surfaces prior to coating.
- Hard Chromium Plating
- The electrolytic deposition of chromium to form a very hard (1000Hv), tough coating with good wear resistance. The structure is micro-cracked.
- The application of a cladding or coating of material designed to resist wear.
- Hardness test
- A test designed to assess the resistance to penetration from a load. The surface is indented under a defined load and the depth or area of penetration is measured.
- Helium (He)
- Monatomic noble gas, Most inert element, atomic number 2. Used as a plasma gas in the plasma spraying process.
- High Velocity Air-fuel Spraying (HVAF)
- A Thermal spray process. The spray powder particles are injected into a high velocity jet formed by the combustion of fuel with air, heated and accelerated to the work piece.
- High Velocity Oxy-fuel Spraying (HVOF)
- A Thermal spray process. The spray powder particles are injected into a high velocity jet formed by the combustion of oxygen and fuel, heated and accelerated to the work piece.
- The high temperature/high pressure consolidation of a
powder metallurgy component or thermally sprayed coating. Density is
greatly increased and metallurgical changes provide enhanced corrosion
and wear properties.
- Hot dip coating
- A metallic coating obtained by dipping the substrate metal
into a molten metal.
- See High Velocity Air fuel spraying
- See High Velocity Oxygen fuel spraying
- Hydrogen (H2)
- Diatomic gas, atomic number 1, The lightest element, very
reactive and powerful reducing agent. Used as a secondary plasma gas in
the plasma spraying process and as a fuel gas in combustion thermal
- Hydrogen embrittlement
- Hydrogen induced cracking or severe loss of ductility
caused by the presence of hydrogen in the metal. Hydrogen absorption
may occur during electroplating, pickling etc. ( The use of hydrogen as
a secondary gas in plasma spraying does not appear to effect substrates
and the majority of coatings, one exception being titanium coatings.)
- Tending to absorb water.
- Tending to repel water or lacking affinity for water
- A process of filling the pores of a coating with resin,
wax or oil. (See sealer, vacuum impregnation)
- Induction heating
- The heating of a electrically conductive material by an
induction coil producing alternating magnetic fields which induce
alternating electric currents to flow in the material and cause heating
by resistance. Used in many heating process (induction fusing,
induction plasma, induction hardening etc..)
- Induction hardening
- The localised surface heating of a medium carbon steel by
an induction coil so that the temperature is raised above 900oC.
The part is quenched (or self-quenches by virtue of the remaining cool
bulk of the component) and tempered to produce a hard martensitic
structure at the surface.
- A process resulting in a continuing succession of impacts
between (liquid or solid) particles and a solid surface.
- Impingement corrosion
- a form of erosion-corrosion generally associated with the
impingement of a high velocity, flowing liquid containing air bubbles
against a solid surface.
- Interconnected porosity
- A network of pores in and extending to the surface of a
- A process in which a beam of positive ions is projected
towards and into the surface. It is carried out in partial vacuum and
the ions diffuse into the surface layer of the substrate. Typically
this is carried out with nitrogen giving a nitrided effect.
- Ion nitriding
- Also called plasma nitriding. A vacuum glow discharge
technique of nitriding. See Nitriding.
- Ion plating
- A process in which positive ions produced in a glow
discharge are attracted to the substrate which is connected as the
cathode. The ions are typically made by evaporation.
- Irregular powder
- Particles lacking symmetry.
- Intergranular corrosion
- Preferential corrosion at or adjacent to the grain
boundaries of a metal or alloy.
- Internal oxidation
- The formation of isolated particles of corrosion products
beneath the surface of the metal or coating. (This occurs as a result
of preferential oxidation of certain alloy constituents by inward
diffusion of oxygen, nitrogen, sulphur, etc.
- Liquid fuel used in some HVOF thermal
- Rubbing two surfaces together, with or without abrasives,
for the purpose obtaining extreme dimensional accuracy or superior
- Laser alloying
- The application of a powder to a surface followed by
fusing and alloying into the surface via the heat from an impinging
- Laser glazing
- The melting and quenching of a surface to form a fine
grained structure or 'glaze'.
- Laser hardening
- The localised surface heating of a medium carbon steel by
an incident laser so that the temperature is raised above 900oC.
The part is quenched (or self-quenches by virtue of the remaining cool
bulk of the component) and tempered to produce a hard martensitic
structure at the surface.
- Liquid impingement erosion
- Progressive loss of material from a solid surface due to
continue exposure to impacts by liquid drops or jets.
- Localized corrosion
- Corrosion at discrete sites, for example, pitting, crevice
corrosion, and stress corrosion cracking.
- See 'Vacuum or Low Pressure Plasma Spraying.'
- Any substance interposed between two surfaces for the
purpose of reducing the friction or wear between them.
- The hardness of a coating as measured on a macroscopic
scale, which shows the coatings bulk properties.
- Magnetron sputtering
- See Sputtering. In this PVD process, the sputtering action
is enhanced by intense magnetic fields.
- The continuous phase of a material or coating in which
separate particles of another constituent are embedded. (Like tungsten
carbide particles in a cobalt matrix)
- Mechanical bonding
- Usually represented by mechanical interlocking of the
deposited particles with the rough heights on the substrate surface
produced during grit blasting.
- Metallurgical bonding
- Produced by diffusion or chemical bonding between the
coating and substrate.
- A micrograph is produced when a section of the coating is
taken, polished to show the particulate layers and then photographed
through a microscope.
- The hardness of a coating as measured on a microscopic
scale. Can show the hardness of individual phases within the coating
and avoid the effects of porosity.
- One millionth of an inch, 0.000001".
- One millionth of a metre, 0.001mm.
- A device for measuring powder particle size distributions.
- One thousandth of an inch, 0.001" (Common in USA)
- Minus sieve
- The portion of a powder sample which passes through a
standard sieve of specified number e.g. -140 mesh +325 mesh. ( See plus
- Nickel plating
- The electrolytic deposition of nickel to form a corrosion
barrier or to reclaim a worn part. Can also include hard ceramic
particles to from a wear resistant composite coating.
- The diffusion of nitrogen into alloy steel to form hard
nitrides in the surface layer (typically 250µm). Performed at
between 500 and 750oC from a gas, salt bath or plasma glow
- The diffusion of nitrogen and carbon into alloy steel or
mild steel to form hard nitrides in the surface layer (typically
250µ). Performed at between 500 and 750oC from a gas,
salt bath or plasma glow discharge.
- Nitrogen (N2)
- Diatomic gas. Used as a primary and
secondary gas in plasma spraying. Inert to most materials, with
some exceptions like titanium.
- Noble metal
- A metal that does not readily tend to furnish ions, and
therefore does not dissolve readily, nor easily enter into such
reactions as oxidation, etc. The opposite of base metal.
- Nodular powder
- Irregular particles having Knotted, rounded, or similar
- Loss of electrons by a constituent of a chemical reaction.
(Also refers to the corrosion of a metal that is exposed to an
oxidising gas at elevated temperatures.)
- An environment or material which promotes oxidation
- Oxygen (O2 )
- Gas used to support combustion of fuel gases in combustion
thermal spray processes. Achieves much higher flame temperatures than
- Pack carburising
- See Carburising
- The application of organic based layers (acrylics, etc.)
for corrosion protection and decorative purposes.
- Particle chemistry
- The elements contained within the particles of a spray
- Particle size
- The controlling lineal dimension of an individual particle
as determined by analysis with sieves or other suitable means.
- Particle size distribution
- The percentage by weight, or by number, of each fraction
into which a powder sample has been classified with respect to sieve
number or microns.
- The process in metal corrosion by which metals become
passive. (See passive)
- A type of inhibitor which appreciably changes the
potential of a metal to a more noble (positive) value.
- The state of a metal surface characterized by low
corrosion rates in a potential region that is strongly oxidising for
- Blasting process using spherical shaped beads or shot for
cleaning and/or modifying surface properties.
- A property measured as a rate of passage of a liquid or
gas through a coating
- Plus sieve
- The portion of a powder sample retained on a sieve of
specified number. (See minus sieve.)
- Physical Vapour Deposition
- A term covering all the vapour deposition processes
including Ion plating, It does not include CVD as this is chemical not
- A conversion treatment to produce a thin phosphate-based
layer on a steel surface, providing improved corrosion protection and
good surface for painting.
- Photo-thermal NDT
- An NDT technique for spayed coatings. A repeated pulse of
heat, from a laser source, flows through the coating and substrate. The
thermal signature is detected and related to the input signal thereby
indicating coating thickness.
- A form of wear characterized by the presence of surface
cavities the formation of which is attributed to processes such as
fatigue, local adhesion, or cavitation.
- corrosion of a metal surface, cofined to a point or small
area, that takes the form of cavities
- Plasma Carburising
- See Carburising
- Plasma jet or plasma flame
- A jet of highly ionised gas usually produced from a plasma
torch. An electric arc is struck between a cathode and anode and is
then blown through a nozzle to form the flame or jet.
- Plasma Nitriding
- Also called Ion Nitriding. See Nitriding
- Plasma Spraying
- A thermal spraying process in which the heat source is a
- Plasma Transferred Arc (PTA)
- Similar to the plasma spray process in that powder is sprayed
through a plasma, but instead of being heated via a neutral plasma
(carrying no electric current) the arc is transfered to the substrate
(made to be the anode). This is a hot process and produces coatings
similar to fused or weld hardfacing coatings.
- The formation of grooves by plastic deformation of the
softer of two surfaces in relative motion.
- A condensation polymer formed by the interaction of
polyhydric alcohols and polybasic acids. They are used in some coatings
and the manufacture of glass-fibres products. See Alkyd resin.
- Organic substance having large molecules consisting of
repeated units. There are a number of natural polymers, such as
polysaccharides synthetic polymer are extensively used in plastics.
- The presence of pores or voids in a coating, usually
expressed as a percentage by volume.
- Powder coating
- A polymeric coating deposited via electrostatic attraction
- Powder injection angle
- The angle from which the powder is injected into the
plasma jet in plasma spraying.
- Pre-alloyed powder
- A powder composed of two or more elements which are
alloyed in the powder manufacturing process and in which the particles
are of the same nominal composition throughout.
- The smoothing of a material surface by means of the action
of abrasive particles attached usually to a fabric cloth. The final
mechanical step in metallographic preparation.
- Propane (C3 H8)
- Aliphatic hydrocarbon gas used as a fuel gas in thermal
- Propylene (C3 H6)
- Hydrocarbon gas used as a fuel gas in thermal spray
processes. Higher flame temperature than hydrogen and propane.
- Pull-out occurs when particles are plucked from the
coating during machining or grinding. Also occurs during metallographic
preparation. It is sometimes confused with porosity.
- See Physical Vapour Deposition
- Quality Control
- All aspects of the control of the spraying process
including the surface preparation, spraying, control of thickness
deposited and the oxide and porosity levels, surface finish and NDE
checks as specified.
- Reducing Agent
- A substance that cases reduction, thereby itself becoming
- A reaction in which electrons are added to the reactant.
More specifically, the addition of hydrogen or the abstraction of
- A synthetic or naturally occurring polymer
- RFI Shielding
- Thermal spray coatings of electrically conductive metals
such as zinc, aluminium and copper are used on non-conducting composite
casing materials to shield sensitive electronic devices from radio
frequency electromagnetic interference.
- Rhodium plating
- The electro-deposition of rhodium for oxidation resistance
combined with surface hardness.
- Sacrificial coating
- A coating that provides corrosion protection wherein the
coating material corrodes in preference to the substrate,thereby
protecting the latter from corrosion.
- Salt Bath Carburising
- See Carburising
- Salt Bath Nitriding
- See Nitriding
- Salt Bath Nitrocarburising
- See Nitrocarburising
- A severe form of wear characterized by the formation of
extensive grooves and scratches in the direction of sliding.
- The mechanical removal or displacement, or both, of
material from a surface by the action of abrasive particles or
protuberances sliding across the surfaces.
- Sealant, Sealer
- A preparation of resin or wax type materials for sealing
the porosity in coatings.
- A process which, by absorption of a sealer into thermal
spray coatings, seals porosity and increases resistance to corrosion of
the underlying substrate material.
- Self-bonding coatings
- A name given to thermal spray coatings that are capable of
bonding to clean smooth surfaces. Bond and "one-step" coatings are
normally in this group. These are paticularly important where grit
blasting or surface roughening processes must be omitted.
- A decrease in dimensions of a coating during processing.
- Shrinkage stress
- The residual stress in a coating caused by shrinkage
- Shot peening
- The bombardment of a component surface with steel or
ceramic shot. Produces a residual compressive stress in the surface and
improves fatigue and stress corrosion performance.
- Sieve classification
- That portion of a powder sample which passes through a
standard sieve of specified number and is retained by some finer sieve
of specified number.
- A gaseous and/or mechanical or physical barrier placed
around the spraying process designed to reduce the ingress of air into
the system and so reduce oxidation of the of the materials being
- Silver plating
- The electro-deposition of silver for electrical,
decorative or anti-fretting properties.
- Size analysis
- Analysis of the size of the particles being deposited by
- Size distribution
- The distribution of sizes within a size analysis. The
distribution may be normal or skewed in some way due to the powder
- The lifting or detachment of a coating from the substrate.
- Spray chamber
- A chamber in which the spraying process is carried out. It
may merely be an acoustic chamber for plasma spraying or a vacuum
chamber for vacuum plasma spraying.
- Spray dried powder
- Powder formed by the spray drying process.
- Spray-fused coatings
- A process in which the coating material is deposited by
flame spraying and then fused into the substrate by the addition of
further heat. This can be applied by flame, induction heating or by
- This is a glow discharge process whereby bombardment of a
cathode releases atoms from the surface which then deposit onto a
nearby target surface to form a coating.
- Steam tempering
- The production of a stable oxide on steel parts by
treatment in steam at about 300oC. Improves corrosion
performance and reduces friction.
- A measure of the extent to which a body is deformed when
it is subjected to a stress.
- The force per unit area on body that tends to cause it to
deform. It is a measure of the internal forces in a body between
particles of the material of which it consists as they resist
separation, compression, or sliding.
- Stress corrosion cracking
- A cracking process that requires the simultaneous action
of a corrodent and sustained tensile stress.
- The parent or base material to which the coating is
- Surface preparation
- Cleaning and roughening the surface to be sprayed, usually
by grit blasting. This is to increase the adhesion of the coating to
- The reaction of a metal or alloy with a sulphur containing
species to produce a sulphur compound that forms on or beneath the
surface of the metal or alloy.
- Surface topography
- The geometrical detail of a surface, relating particularly
to microscopic variations in height.
- The application of a coating or cladding to a surface to
impart a change in its surface behaviour.
- Tensile strength
- A measure of the resistance that a material offers to
tensile stress. It is defined as the stress, expressed as the force per
unit cross sectional area, required to break it.
- Tensile stress
- Axial forces per unit area applied to a body that tend to
- Thermal barrier coating
- A coating forming an insulating barrier to a heat source
to protect the substrate.
- Thermochemically formed coatings
- A painted, dipped or sprayed chromium oxide based coating
consolidated by repeated deposition and curing cycles (about 500oC).
- Thermal spraying
- A process in which coating material is heated and accelerated
from a spray torch towards the work piece. The deposited material forms
a coating on the surface.
- An NDE technique in which the coating is flash heated and
then viewed with an infra red camera. "Hot spots" indicate areas of
poor bonding or greater coating thickness.
- Transferred arc
- In a plasma torch the plasma jet is emitted from the torch and
the current flows from the internal cathode to the internal anode
represented by the nozzle of the torch. When the jet is carried to
another anode with it being electrically favourable to do so the
current will then transfer to the second anode, usually the work piece
and the arc is said to be transferred.
- The science and technology concerned with interacting
surfaces in relative motion.
- An NDE technique which relies on an ultrasonic beam
passing through a coating and substrate and providing a signal from the
back wall which is then detected. The height of this backwall echo
depends on the discontinuity in impedance from the sprayed coating to
the substrate. Bonding flaws can be easily seen by the weakening of the
back wall echo.
- Vacuum or Low Pressure Plasma Spraying
- Plasma spraying carried out in a chamber which has been
evacuated to a low partial pressure of oxygen. It is then usually
partially backfilled with argon to avoid the possibility of forming a
- Wire spraying
- A thermal spray process whereby the supply for the coating
material is fed into the gun in the form of a continuous wire.
- Loss of material from a surface by means of some
- -in tribology, the bonding between surfaces in
direct contact, at any temperature.
- Welding Process
- The joining of materials by the application of heat or
friction. Usually involves the localized fusion of both contacting
- Yttria-stabilized zirconia (YSZ)
- ceramic in which the crystal structure of zirconium dioxide is made stable at room temperature by an addition of yttrium oxide.
- Zinc (Zn)
- Thermal spray coatings of zinc or zinc alloys (eg Zn/Al,
Zn/Sn) provide galvanic corrosion protection.
- Zinc Plating
- The electro-deposition of zinc or zinc alloys (eg Zn/Ni,
Zn/Sn) to provide galvanic corrosion protection.
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Nature of Thermal Spray Coatings
Surface Engineering in a Nutshell
Surface Engineering Forum
Thermal Spray Gun Repair Service
Plasma Consumable Parts
Thermal Spray Powder Supplies
Thermal Spray Coatings on Carbon and Glass Fibre Reinforced Polymers
HVOF Coating of Paper Making Roll
Thermal Spray Processes:
Combustion Wire Thermal Spray Process
Combustion Powder Thermal Spray Process
Arc Wire Thermal Spray Process
Plasma Thermal Spray Process
HVOF Thermal Spray Process
HVAF Thermal Spray Process
Detonation Thermal Spray Process
Plasma Flame Theory
Cold Spray Coating Process
Wear and Use of Thermal Spray Coatings
Corrosion and Use of Thermal Spray Coatings
Glossary of Thermal Spray and Surface Engineering Terms
Image Directory for Thermal Spray Coatings
Plasma Gas Flow Information
Plasma Gas Flow Correction Calculator
Links to other interesting sites related to thermal spray and surface engineering
Periodic Table of the Elements
Calculators for Conversion between Units of Measurement
Surface Engineering Message Board Archive
Surface Engineering Message Board Archive Index
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