Thermal Barrier Coatings : A group of ceramic coatings, including Yttria Stabilized Zirconia (YSZ) and Magnesium/Zirconate, used to protect the substrate in extreme heat environments. The heat rejection properties of TBCs excel in applications to an excess of 3000 °F. TBCs have been used successfully on piston tops, valves, exhaust systems, etc.

Splat: A single sprayed particle that resembles a thin, flattened drop of liquid, under magnification.

Metallic bond: The principal bond that holds metals together and is formed between base metals and filler metals in all processes.

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

Gradated coating: A thermal spray deposit composed of mixed materials in successive layers that progressively change in composition from the constituent material lot to the surface of the sprayed deposit.

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

Plasma spraying : A thermal spray process in which a nontransferred arc is used as the source of heat that ionizes a gas which, in turn, melts and propels the coating material to the work piece.

Abrasion : To wear away by friction.

Wear: To damage, erode or consume by long, hard use.

Spalling: The flaking or separation of a sprayed coating.

Bond strength: The force required to pull a coating free of a substrate, usually expressed in kPa (psi).

Anode : The electrode maintained at a positive electrical potential.

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

Plasma: An electrically neutral, highly ionized gas composed of electrons, ions, and neutral particles.

Feed rate : A nonstandard term for spray rate.

Powder: Material manufactured into finely divided particles. When blended for thermal spraying, powder falls within a specific mesh range, usually finer than 120 mesh (125 microns).

Carbide : A chemical compound formed between carbon and a metal or metals; examples include tungsten carbide, tantalum carbide, titanium carbide, chromium carbide.

Ceramic : Any of the various hard, heat-resistant, and corrosion resistant coatings made up of non-metallic materials.

Cermets : A mixture of ceramics and metals used as a thermal spray material.

Alumina : Aluminum oxide; a ceramic used in powder or rod form in thermal spray operations.

Oxide: A chemical compound; the combination of oxygen with a metal forming a ceramic; ex. Aluminum oxide.

Mask: A device for protecting a substrate surface from the effects of blasting or adherence of a spray deposit.

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.

Cladding : 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).

Erosion : 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.

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.

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

Oxidation : Loss of electrons by a constituent of a chemical reaction. (Also refers to the corrosion of a metal that is exposed to an oxidizing gas at elevated temperatures.)

Oxidizing : An environment or material which promotes oxidation.

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.

Porosity : The presence of pores or voids in a coating, usually expressed as a percentage by volume.

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 particularly important where grit blasting or surface roughening processes must be omitted.

Shroud : 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 sprayed.