Thermal Spray Glossary O-S

Thermal Spray Glossary O-S


Open Circuit Voltage.
The potential difference applied between the anode and cathode prior to initiating the arc.
The excess spray material that is not deposited on the part being sprayed.
A chemical compound, the combination of oxygen with a metal forming a ceramic; examples - aluminum oxide, zirconium oxide.
Oxidizing Flame.
An oxyfuel gas flame having an oxidizing effect (excess oxygen).
Oxyfuel Gas Spraying.
A nonstandard term for flame spraying.


A measurable factor relating to several variables; loosely used to mean a spraying variable, spraying condition, spray rate, spray distance, angle, gas pressure, gas flow, etc.
Parent Metal.
A nonstandard term for substrate.
Particle Size.
The average diameter of a given powder or grit granule.
Particle Size Distribution.
Classification of powdered materials as determined by various testing methods defining the particle sizes and quantities in a given sample.
Particle Size Range.
See preferred term Particle Size Distribution.
A single progression of the thermal spray device across the surface of the substrate.
Physical Bond.
See preferred term Metallic Bond.
See preferred term Thermal Spraying Gun.
See Arc Plasma.
Plasma Forming Gas.
See preferred term Arc Gas. Plasma Metallizing. A nonstandard term for plasma spraying.
Plasma Spraying (PSP).
A thermal spraying process in which a nontransferred arc is utilized as the source of heat that ionizes a gas which melts and propels the coating material to the workpiece.
Plenum Chamber.
The space between the inside wall of constricting nozzle and the electrode.
Cavity type discontinuities within a sprayed coating (voids).
Postflow Time.
The time interval between plasma arc shutdown and electrode cooling, to inhibit oxidation of electrodes.
The application of heat to an assembly after a thermal spraying operation.
Material manufactured into finely divided particles.
When explicitly blended for thermal spraying, powder falls within a specific mesh range, usually finer than 120 mesh (125 microns).
Fine powder is usually defined as having particles smaller than 325 mesh (44 microns).
Powder Alloy.
Powder prepared from a homogeneous molten mixture of elements, and sometimes entrapped carbides or metal oxides. All of the particles have approximately the same composition.
Powder Blend.
A heterogeneous mixture of two or more alloy powders.
Powder Clad (Wire Clad).
Powder or wire wherein one alloy is encapsulated in another; a composite.
Powder Composite.
Two or more independent materials, combined to form a single integrated unit.
May be either chemically clad or mechanically agglomerated.
Powder Feeder.
A device for conveying powdered materials to thermal spraying equipment.
Powder Feed Gas.
See preferred term Carrier Gas.
Powder Feed Rate.
The quantity of powder introduced into the hot, gaseous stream per unit of time.
Powder Fame Spraying.
A thermal spraying process variation in which the material to be sprayed is in powder form; all oxyfuel gas processes. See Flame Spraying (FLSP).
Powder Injection.
Feeding of a powder through a powder port into a thermal spray flame.
Powder Metallizing.
A nonstandard term for powder flame spraying.
Powder Port.
Internal or external orifice through which powder is injected into flame or plasma.
Prenow Time.
The time interval between start of shielding gas flow and arc or gas ignition.
The heat applied to the base metal or substrate immediately before spraying.
Preheat Temperature.
A specified temperature that the substrate is required to attain immediately before material deposition.
Primary Gas.
The major constituent of the arc gas fed to the gun to produce the plasma; usually argon or nitrogen.
The detailed elements of a process or method used to produce a specific result.
Protective Atmosphere.
A gas envelope or vacuum surrounding the part to be thermally sprayed, with the gas composition controlled with respect to chemical composition; dewpoint, pressure, flow rate, etc. Examples are inert gases, combusted fuel gases, hydrogen and vacuum.
Protective Barriers.
Curtains or portable fireproof canvas shields, sometimes required to enclose work areas, when there is a possibility of the spray stream being misdirected, or where the glare of the arc or flame could injure unprotected eyes.
Protective Clothing.
Leather or metal coated articles designed to prevent burns from ultraviolet radiation or misdirected particles.


Quench Rate.
The speed at which a sprayed particle cools upon striking the surface of the substrate.


Rate of Deposition.
See Deposition Rate.
Reducing Flame.
A gas flame having a reducing effect (excess fuel gas).
Refrigerated Dryer.
The application of a refrigeration cycle to physically lower the dewpoint.
Regenerative Dryer.
A double column apparatus containing a drying medium for moisture absorption, which is automatically regenerated.
See Gas Regulator.
Relative Density.
See preferred term Apparent Density Ratio.
Residual Stress.
Stress remaining in a structure or member as a result of thermal or mechanical treatment or both. See Coating Stress.
Resonance Time.
See preferred term Dwell Time.
Root Mean Square (RMS).
A method of defining the average roughness of a surface. It is the square root of the sum of all individual measurements divided by the number of measurements.
Rotary Roughening.
A method of surface roughening in which are revolving roughening tool is pressed against the surface being prepared, while either the work or the tool, or both, move.
Rough Threading.
A method of surface roughening which consists of cutting threads with the sides and tops of the threads jagged and torn.


Saturated Air
To reach 690 kPa (100 psi) air at 100% humidity, it is necessary to compress approximately 0.23 ml (8 ft.') of free air, with its inherent moisture, into 0.028 ml (one cubic foot), since atmospheric humidity is usually more than 12.5% at
ambient. All undried compresed air systems at 690 kPa (100psi) and ambient temperatures are at 100% relative humidity.
One of a set of sieves, designated by the size of the openings, used to classify and sort powder to particle size.
Seal Coat.
Material applied to infiltrate and close the pores of a thermal spraying deposit. Secondary Gas.
The minor or second constituent of the arc gas fed to the gun to produce plasma.
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.
Surfacing materials that "wet" the substrate and coalesce when heated to their melting point, without the addition of an externally applied flux. These alloys contain boron or silicon, or both, as fluxing agents.
Shadow Mask.
A protective device that partially shields an area of the work, thus permitting some overspray to produce a feathering at the coating edge.
Shear Stress.
The stress on the slip plane produced by external loads tending to slide adjacent planes with respect to each other in the direction parallel to the planes.
Shielding Gas.
Protective gas used to prevent or minimize atmospheric contamination. See also Protective Atmosphere.
Shrinkage Stress.
A nonstandard term for residual stress.
See preferred term Screen.
Sieve Analysis.
A method of determining particle size distribution, usually expressed as the weight percentage retained upon each of a series of standard screens of decreasing mesh size. See also Particle Size Distribution.
Slick Up.
Point at which a self-fluxing alloy begins to shine during the fusing operation.
Solvent Degreasing.
The removal of oil, grease, and other soluble contaminants from the surface of the workpiece by immersion in suitable cleaners.
The flaking or separation of a sprayed coating.
A single thin flattened sprayed particle.
Splat Cooling.
Extremely rapid, high rate of cooling, the effects of which can be observed in thermal spraying deposits leading to the formation of metastable phases and an amorphous microstructure.
A moving mass of dispersed liquid droplets or heat softened particles.
Spray Angle.
The angle of particle impingement, measured from the surface of the substrate to the axis of the spraying nozzle.
Spray Booth.
See preferred term Exhaust Booth.
Spray Deposit.
See thermal spraying deposit.
Spray Deposit Density Ratio.
The ratio of the density of the spray deposit to the theoretical density of the surfacing material. Usually expressed as percent of theoretical density.
Spray Distance.
The distance maintained between the thermal spraying gun nozzle tip and the surface of the workpiece during spraying.
Spray Dry.
A method for making thermal spray powder, especially ceramic powder, by spraying a slurry into a heated chamber and drying it to powder.
Spray Rate.
The rate at which surfacing material passes through the gun.
Spraying Sequence.
The order in which different layers of similar or different materials are applied in a planned relationship, such as overlapped, superimposed, or at given angles.
Stabilizing Gas.
The arc gas, ionized to form the plasma, is usually introduced into the arc chamber tangentially. The relatively cold gas chills the outer surface of the arc stream, tending to constrict the plasma, raise its temperature, and force it out of the anode (nozzle) in a steady, relatively unfluctuating stream.
Statistical Process Control (SPC).
To enhance, optimize and control coating properties influenced by parameter interaction.
Step Mounting.
The intentional overlapping of several workpieces in order that one protects or masks its neighbor during the blasting or spraying process.
To volatilize from the solid state to a gas.
Any material to which a thermal spraying deposit is applied.
Extra small, minute powder particles, usually less than five microns in size.
The difference between the higher actual temperature at the evaporator outlet and the lower theoretical temperature of the refrigerant at pressure.
Surface Feet Per Minute (SFPM).
Linear velocity of the thermal spray gun as it traverses the length of the workpiece.
Also, the circumferential velocity of the substrate.
Surface Preparation.
The operations necessary to produce a desired or specified surface condition.
Surface Roughening.
A group of methods for producing irregularities on a surface. See also Dovetailing, Groove and Rotary Roughening, Rotary Roughening, Rough Threading, and Threading and Knurling.
The application by thermal spraying of a layer or layers of material to a surface to obtain desired properties or dimensions, as opposed to making a joint.
Surfacing Material.
The material that is applied to a substrate during surfacing.
Surfacing Metal.
The metal that is applied to a substrate during surfacing.