A

Abradable

Abradable: A Thermal Spray Coating that can either be applied by Plasma Spraying or Combustion Powder spraying that is used as a clearance control coating in Compressors and Turbines.

Abrasive Wear

Abrasive Wear: Wear due to hard particles or protuberances forced against & moving along a solid surface.

Acoustic Room

Acoustic Room: A soundproof enclosure, containing Thermal Spray Equipment eg Plasma or HVOF. It is designed to contain the high noise levels associated with the Thermal Spray Process from escaping to the local environment

Adhesion

Adhesion: A binding force that holds together molecules of substances whose surfaces are in contact or near proximity

Adhesive Strength

Adhesive Strength: The size of attractive forces generally physical in nature, between a Thermal Spray Coating and the substrate.

Adhesive wear

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.

Agglomerate

Agglomerate: Several particles adhering together as in: Agglomerated Powder used in Thermal Spraying.

Air classification

Air classification: The separation of powder into particle size fractions by means of an air stream of controlled velocity.

Aluminising (Thermal spray method)

Aluminising (Thermal spray method): Thermally sprayed coatings of aluminium usually on substrates of steel or nickel chromium alloys which are subsequently heat treated to aluminise the surface. See “TSA”.

Anode

Anode: The electrode maintained at a positive electrical potential. In typical Plasma Spraying gun designs this is typically called the nozzle.

Arc

Arc: A luminous discharge of electrical current crossing the gap between two electrodes

Arc Gas

Arc Gas: The gas introduced in to the arc chamber and ionized by the arc to form a plasma

Arc Plasma

Arc Plasma: A gas that has been heated by an electric arc to at least a partially ionized condition enabling it to conduct an electric current.

Arc Spraying

Arc Spraying: A thermal spray process using an arc between two consumable electrodes of surfacing materials as a heat source and a compressed gas to atomize and propel droplets of the surfacing material on to the substrate.

Atomization

Atomization:
1. The division of molten material at the end of the wire into fine particles
2. The process used in the manufacture of powder

Atomized powder

Atomized powder: A powder produced by the dispersion of molten material into particles by a rapidly moving gas or liquid stream or by mechanical dispersion.

B

Blended powder

Blended powder: A powder consisting of two or more different materials which are thoroughly mixed in order to provide a material capable of producing an alloyed deposit.

Bond

See "Mechanical Bond" and "Metallic Bond"

Bond Coat

Bond Coat: The initial thermal spray coating layer that is applied for the purpose of optimizing the bond strength between the Thermal Spray coating and the substrate

Bond strength

Bond strength: The strength of the adhesion between the coating and substrate, or, in some cases between coating layers. A number of test methods can be used to measure the bond strength of coatings. A typical test would be to ASTM C633.

Buildup

Buildup: The deposit of the Thermal Spray coating material to the required thickness prior to any machining that forms the finished coating.

C

Carbide

Carbide: A chemical compound formed between carbon and a metal or metals, examples of those used in the Thermal Spray Process are Chromium Carbide and Tungsten Carbide

Carrier Gas

Carrier Gas: The gas used to carry powdered material from the powder feeder or hopper to the thermal spray gun

Cathode

Cathode: The electrode maintained at a negative electrical potential. In a plasma gun it is usually the rear electrode.

Cavitation erosion

Cavitation erosion: A form of erosion causing material to be removed by the action of vapour bubbles in a very turbulent liquid. Effects can be reduced via the application of ceramic coatings.

Cermet

Cermet: A physical blend of metal and ceramic powders.

Coating

Coating:
1. The act of building a thermal spray deposit on to a substrate
2. The spray deposit

Coating density

Coating density: A non standard term for the thermal spray coating density ratio.

Coating stress

Coating stress: The stresses in a coating resulting from rapid cooling of molten material or semi molten particles as they impact and adhere to the substrate.

Cold Spray

Cold Spray: or Cold Gas Dynamic spraying. This process uses the energy stored in a high pressure compressed gas in order to propel fine powder particles at very high velocities in order to form near 100% dense deposits.

Composite coating

Composite coating: A thermal spray coating consisting of two or more dissimilar spray materials which may or may not be layered.

Composite powder

See "Powder Composite"

Controlled Atmosphere Chamber

Controlled Atmosphere Chamber: An enclosure either filled with an inert gas or evacuated to below atmospheric pressure in which thermal spraying can be performed under controlled atmosphere conditions to minimize or prevent oxidation of the coating or the substrate.

Corrosion

Corrosion: Chemical or electrochemical reaction between a material and it’s environment which results in deterioration in the properties of the material.

Crushed Powder

Crushed Powder: Powder formed from a solid which is subsequently crushed and sized appropriately for the relevant spraying process.

D

Degreasing

Degreasing: 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

Deposit: A non standard term to describe the application of a thermal sprayed coating.

Deposition efficiency

Deposition efficiency: The ratio, usually expressed as a percentage, of the weight of the thermal spray deposit to the weight of the thermal spray powder processed using any of the thermal spray processes.

Deposition rate

Deposition rate: The weight of thermal spray material deposited in a unit of time

Detonation Flame Spraying

Detonation Flame Spraying: Sometimes abbreviated to "D-Gun". A thermal spraying process variation in which the controlled explosion of a mixture of fuel gas and oxygen is utilized to melt and propel the thermal spray material to the substrate.

Diffusion coating

Diffusion coating: An alloy coating produced by applying heat to one or more coatings deposited on a base metal.

Dwell time

Dwell time: The length of time that the thermal spray material is exposed to the heat source within the thermal spray process which thereby produces and maintains a molten condition.

E

Electric Arc Spraying

Electric Arc Spraying: A non standard term for Arc Spraying

Electrode

Electrode: A component for the electrical circuit through which current is conducted to the arc. See anode and cathode

Erosion

Erosion: Removal of material from a surface due to mechanical interaction between that surface and a fluid, a multi-component fluid, impinging liquid or solid particles. Erosion can be combated effectively via the application of a wide range of thermally sprayed coatings.

Exothermic reaction or material

Exothermic reaction or material: Certain materials undergo chemical reactions when thermally sprayed and therefore can produce extra heating effects. This can be useful in improving adhesion to the substrate. See “Bond Coat”.

F

Feed rate

Feed rate: A non standard term used to describe spray rate

Flame Spraying

Flame Spraying: A thermal spray process in which an oxyfuel gas flame is the source of heat for melting thermal spray materials in wire or powder form. Compressed air may or not be used to atomize the molten particles and propel them on to the substrate to form a thermal sprayed coating

Fretting wear

Fretting wear: Surface damage resulting from relative motion between surfaces in contact under pressure

Fuel gases

Fuel gases: Gases such as acetylene, natural gas, propane, propylene and other fuels normally used with oxygen for heating and melting thermal spray materials within the Flame Spraying process.

Fused Coating

Fused Coating: A self-fluxing spray deposit which is subsequently heated to coalesce with itself and with the substrate

Fused and crushed powder

Fused and crushed powder: Powder formed from a fused solid mass which is then crushed to the appropriate size for spraying.

G

Gas flow rate

Gas flow rate: The flow rate of gas (e.g. litres per minute) through the relevant spraying torch.

Grinding

Grinding: The removal of material by the use of fixed abrasives. Examples include the diamond grinding of HVOF sprayed carbide containing coatings.

Graded coating

Graded coating: A thermal spray coating composed of mixed materials in successive layers which progressively change in composition from the constituent material of the substrate to the surface of the thermal sprayed deposit. Also referred to as graduated or gradated coating

H

Hard chrome plate replacement

Hard chrome plate replacement: Thermally sprayed coatings (typically HVOF applied carbide materials) used as an effective replacement for electroplated materials without the negative aspects associated with hexavalent chromium.

Hardness test

Hardness test: A test designed to assess the resistance to penetration from a load. Typically used a quality control test for thermal spray coatings.

Hardfacing

Hardfacing: A term used to describe a Thermal Spray deposit applied with the intention to reduce wear. Can sometimes be referred to as a wear resistant coating.

Helium

Helium: Monatomic noble gas. Most inert element, atomic number 2. Use as a plasma gas in plasma spraying.

High Velocity Oxy Fuel (HVOF) Spraying

High Velocity Oxy Fuel (HVOF) Spraying: A thermal spray process in which a fuel gas is mixed with oxygen and delivered at high pressure to the HVOF gun and ignited to form a high velocity oxygen/fuel gas stream in to which thermal spray powders are introduced and propelled on to the substrate

Hydrogen

Hydrogen: 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. Used as a fuel gas in combustion thermal spray processes.

I

Impregnation

Impregnation: A process of filling the pores of a coating with resin, wax or oil. See “Seal Coat” and “Vacuum Impregnation”.

Intrconnected porosity

Intrconnected porosity: A network of pores in and extending to the surface of a coating.

Interface

Interface: The contact surface between the thermal spray deposit and the substrate

J

K

Kerosene

Kerosene: Liquid fuel used in certain HVOF thermal spray processes.

L

Lapping

Lapping: Rubbing two surfaces together with, or without abrasives, for the purposes of obtaining extreme dimensional accuracy or superior surface finish.

Low Pressure Plasma Spraying (LPPS)

Low Pressure Plasma Spraying (LPPS): A thermal spray process variation in which the process is carried out under controlled atmospheric conditions. The process is carried out in a vacuum chamber and the thermal spray gun is normally operating in a low pressure environment of an inert gas, normally Argon.

M

Macrohardness

Macrohardness: The hardness of a coating as measured on a macroscopic scale, which shows the coatings bulk properties.

Mechanical bond

Mechanical bond: The adherence of a thermal spray deposit to a roughened surface by the mechanism of mechanical interlocking.

Metallurgical bond

Metallurgical bond: Produced by diffusion or chemical bonding between the coating and the substrate.

Metallizing

See "Thermal Spraying"

Micrograph

Micrograph: A micrograph is produced when a section of the coating is taken, polished to show the coating structure and then photographed through a microscope.

Microhardness

Microhardness: The hardness of a coating as measured on a microscopic scale. Can show the hardness of individual phases within the coating.

N

Nitrogen

Nitrogen: Diatomic gas. Used as a primary and secondary gas in plasma spraying.

Non transferred arc

Non transferred arc: An arc that is established between the electrode and the constricting nozzle. The workpiece or substrate is not in the electrical circuit.

Nozzle

Nozzle:
1. A device that atomizes air in an arc spray gun
2. The anode in a Plasma gun

O

Overspray

Overspray: The excess thermal spray material that is not deposited on the part being sprayed.

Oxide layers

Oxide layers: Found typically in metallic coatings as a result of the reaction of the particles with air in the presence of heat generated by the spray process.

Oxyfuel Gas Spraying

Oxyfuel Gas Spraying: A non standard term fopr Flame Spraying

P

Parameter

Parameter: A measurable factor relating to several variables, loosely used to mean a thermal spraying variable, spraying condition, spray rate, spray distance, angle, gas pressure, gas flow etc.

Particle size

Particle size: The average diameter of a given powder or grit granule

Particle size distribution

Particle size distribution: Classification of thermal spray powder materials as determined by various testing methods defining the particle sizes and quantities in a given sample

Particle size range

See Particle size distribution

Pass

Pass: A single progression of the Thermal Spray Gun across the surface of the substrate

Plasma

See Arc Plasma

Plasma Spraying

Plasma Spraying: A thermal spray process in which a non-transferred arc is produced by ionizing an inert gas that then forms the heat source in to which thermal spray materials are injected which are then subsequently propelled to the substrate to form a thermal spray coating.

Porosity

Porosity: Cavity type discontinuities within a thermal sprayed coating

Powder

Powder: Thermal spray material manufactured in to finely divided particles. When explicitly blended for thermal spraying these powders generally fall between an upper limit of 125 microns and 5 microns.

Powder Alloy

Powder Alloy: Powder prepared from a homogenous molten mixture of elements. All of the subsequent particles have approx the same composition

Powder Blend

Powder Blend: A mixture of two or more alloy powders.

Powder Composite

Powder Composite: Two or more independent materials combined to form a single integrated unit.

Powder Feeder

Powder Feeder: A device for transporting powdered materials to the thermal spraying equipment.

Powder Feed Rate

Powder feed rate: The quantity of powder introduced in to the thermal spray process gases per unit of time.

Preheat

Preheat: The heat applied to the substrate immediately before depositing a thermal sprayed coating

Primary Gas

Primary Gas: The major gas used within the Plasma Spray process usually Argon or Nitrogen

Q

R

Residual Stress

Residual Stress: Stress remaining in a structure as a result of thermal or mechanical treatment or both.

S

Seal coat

Seal coat: Material applied to infiltrate and close the pores of a thermal spray coating

Secondary Gas

Secondary Gas: The minor gas of the plasma arc gas combination. Typically Hydrogen or Helium.

Self Bonding materials

Self Bonding materials: Those materials that exhibit the characteristics of forming a metallurgical bond with the substrate in the as-sprayed condition.

Self-Fluxing Alloys

Self-Fluxing Alloys: Thermal spray materials that "wet" the substrate and coalesce whenheated to their melting point without the addition of an external flux. These materials normally contain Boron and or Silicon as fluxing agents.

Sieve

Sieve: One of a set of sieves, designated by the size of the openings, used to classify and sort powder to particle size.

Sieve Analysis

Sieve Analysis: A method of determining particle size distribution.

Spalling

Spalling: The flaking or separation of a sprayed coating

Splat

Splat: A single thin flattened thermally sprayed particle.

Spray

Spray: A moving mass of thermal sprayed dispersed liquid droplets or heat softened particles

Spray Angle

Spray Angle: The angle of particle impingement measured from the surface of the substrate to the axis of the thermal spraying nozzle.

Spray Deposit

See Thermal Spray Deposit

Spray Distance

Spray Distance: The distance maintained between the thermal spraying gun nozzle tip and the surface of the workpiece during spraying.

Spray dried powder

Spray dried powder: Powder formed by the spray drying process.

Spray Fused Coating

Spray Fused Coating: 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 laser.

Spray rate

Spray rate: The rate at which thermal spray material passes through the thermal spray process.

Substrate

Substrate: The parent or base material to which the coating is applied.

Surface activation

Surface activation: A method of cleaning or surface roughening the substrate by a forcibly projected stream of sharp angular abrasive grit.

Surface preparation

Surface preparation: The operations necessary to produce a desired or specific surface condition.

Surfacing

Surfacing: The application by thermal spraying of a layer or layers of thermal spray materials to a surface to obtain desired properties or dimensions.

Surfacing Materials

Surfacing Materials: The materials that is applied by the thermal spray process to a substrate during surfacing

T

Thermal Barrier coating

Thermal Barrier coating: A thermal spray coating used to reduce the rate of heat transfer to allow the components to operate at a higher temperature. Coatings normally associated with combustors for the Gas Turbine

Thermal Spraying

Thermal Spraying: A group of processes in which finely divided metallic or non-metallic thermal spray materials are deposited in a semi molten state to a substrate to form a thermal spray coating

Thermal spray deposit

Thermal spray deposit: The coating or layer of surfacing material applied by a thermal spray process

Thermal Spraying Gun

Thermal Spraying Gun: A device for heating, feeding and directing the flow of thermal spray materials.

Traverse Speed

Traverse Speed: The linear velocity at which the thermal spray gun traverses across the workpiece during the thermal spray coating process.

TSA

TSA: Thermally sprayed aluminium (TSA). Used as part of a galvanic protection system.

U

V

Vacuum impregnation

Vacuum impregnation: The process of sealing a coating in the presence of a vacuum. Penetration of the sealant through the coating is improved by this method. Can be used as part of the sample preparation process or as a method of improving the performance of a coating on a sprayed component.

Vacuum Plasma Spraying (VPS)

Vacuum Plasma Spraying (VPS): A thermal spray process variation in which the process is carried out under controlled atmospheric conditions. The process is carried out in a vacuum chamber and the thermal spray gun is normally operating in a low pressure environment of an inert gas, normally Argon.

W

Wire Flame Spraying

Wire Flame Spraying: A thermal spraying process in which the surfacing material is in wire form. (See Flame Spraying)

Wire Metallizing

See Wire Flame Spraying

X

Y

Z