Abrasive
Material (such as crushed chilled cast iron, crushed steel grit, aluminum oxide, silicon carbide, flint, garnet, or crushed slag) used for cleaning or surface roughening.

Abrasive blasting
A method of propelling abrasive using a compressed gas (typically air) or pressurized liquid (typically water) as the propellant. Also known by terms related to the abrasive media in use, including: sand blasting, shot blasting, grit blasting, bead blasting and blast cleaning.

Air filter
Mechanism for cleaning air of contaminants such as water, oil and solid matter.

Almen gauge
An instrument using a dial or digital indicator, a plunger and a platform for mounting an Almen strip. The gauge is used to measure the arc height of a peened Almen strip. Digital gauges provide arc height readings to four decimal places (0.0001").

Almen strip
Thin strips of spring steel used to quickly gauge the shot peening process. Developed by John Almen at General Motors, these strips are used in conjunction with an Almen gauge to determine the intensity of the shot peen stream.

Alumina
The chemical compound aluminum oxide. A ceramic used in powder or rod form in thermal spraying operations. May also be used as an abrasive grit blasting medium.

Anode
The electrode maintained at a positive electrical potential.

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

Arc gas
The gas introduced into the thermal spraying arc chamber and ionized by the arc to form a plasma gas.

Arc height
A measurement of the amount of deflection or bow in an Almen strip, after it has been shot peened. The measurement is taken at the center of the concave side of the peened Almen strip using an Almen gauge. Readings are normally in thousandths of an inch (0.001"), or in millimeters (mm), while digital gauges can provide readings out to 0.0001".

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

Bond coat
A preliminary (or prime coat) of material that improves adherence of the subsequent spray deposit.

Carbide
A chemical compound formed between carbon and a metal or metals, such as tungsten carbide, tantalum carbide, titanium carbide, and chromium carbide.

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

Cathode
The electrode maintained at a negative electric potential.

Cermet
A physical mixture of ceramics and metals, such as alumina plus nickel, and zirconia plus nickel.

Cold working
The process of deforming metal plastically beyond its yield strength but below its recrystallization temperature (normally room temperature). Cold working normally sets up residual stresses in the material, and is achieved through stretching, compressing, bending, twisting, cold rolling, cold drawing, and by shot peening.

Compressive stress
Force or forces applied toward a common point, for instance a block squeezed in a vise.

Coverage
The measurement of surface area which has been shot peened as indicated by the degree of overlapping dimples, expressed as a percentage of a complete overlapping of dimples.

Deposition efficiency
The ratio, usually expressed in percentage, of the weight of thermal spray deposit to the weight of the material sprayed.

Deposition rate
In thermal spraying, the weight of material deposited in a unit of time.

Fatigue failure
The fracture of a material due to cyclic stresses or loads.

Flame spraying
A thermal spraying process in which an oxyfuel gas flame is the source of heat for melting the surfacing material. Compressed gas may or may not be used for atomizing and propelling the surfacing material to the substrate.

Flow meter
A device for indicating the rate of gas flow in a thermal spray system.

Fretting
A type of wear that occurs between tight-fitting surfaces subjected to cyclic relative motion of extremely small amplitude.

Galling
A condition caused by excessive friction between high spots in a material resulting in localized welding with subsequent spalling.

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

Oxide
A chemical compound. The combination of oxygen with a metal forming a ceramic, such as aluminum oxide, zirconium oxide.

Peening intensity
A measurement of the energy imparted to a materials surface by a stream of shot. The intensity is determined from interpretation of an Almen saturation curve. The peening intensity is the first point on a curve (not necessarily a data point) and commonly referred to as "T1." Beyond this point, the curve or arc height of the Almen strip increases by no more than 10% when the peening time is doubled ("2T").

Plasma spraying
A thermal spraying process in which a nontransferred arc is utilized as the source of the heat that ionizes a gas, which melts and propels the coating material to the workpiece.

Plastic deformation
Deformation that remains permanent after removal of the load that caused it.

Porosity
Cavity type discontinuities within a thermal sprayed coating.

Primary gas
The major constituent of the arc gas fed to the thermal spray gun to produce the plasma, usually argon or nitrogen.

Ricochet peening
Shot peening of a surface achieved by deflecting shot off from another surface. This occurs in applications where surfaces cannot be reached by normal line-of-sight nozzles or lances.

Saturation curve
A best-fit curve generated from a set of arc height readings produced by shot peening an Almen fixture for different time intervals.

Secondary gas
The minor or second constituent of the arc gas fed to the thermal spray gun to produce the plasma.

Shadow mask
A protective device that partially shields the area of work, thus permitting some overspray to produce a feathering at the coating edge.

Shear stress
Stresses due to forces on an object when the forces are slightly offset from one another; for example, the use of scissors in cutting a material.

Shot peening
A process used to produce a compressive residual stress layer and modify mechanical properties of metals. Shot peening entails impacting a surface with shot (round metallic, glass or ceramic particles) with force sufficient to create plastic deformation.

Stress corrosion cracking
Failure by cracking under combined action of corrosion and a tensile stress, either external (applied) or internal (residual).

Tensile stress
Forces applied to a material in opposite directions.

Thermal spraying
A group of processes in which finely divided metallic or nonmetallic surfacing materials are deposited in a molten or semi-molten condition on a substrate to form a spray deposit. The surfacing material may be in the form of powder, rod, cord, or wire.

Waterjet stripping
Also known as weater jet cleaning. High pressure water jet stripping or cleaning involves the use of high pressure water propelled at high speeds to clean surfaces and materials of all types.