Copy of `Poeton - Glossary of Surface Engineering Terms`

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Poeton - Glossary of Surface Engineering Terms Category: General technical and industrial > Coating Date & country: 15/12/2007, UK Words: 133

Corrosion
Chemical or electrochemical reaction between a metal and the local environment whether wet or dry which results in deterioration in the properties of the metal.

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.

Composite
Mixture of two or more materials. Nearly all have a reinforcing material(wood, glass, etc), called filler, and a natural or artificial resin, called matrix to achieve specific characteristics and required properties.

Coating
The application of a thin (generally less than 1mm) layer of material onto the surface of a 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).

Chromising
High temperature (approx 900oC) pack or gaseous diffusion of chromium into the surface of a component to enhance high temperature corrosion and oxidation resistance.

Chromating
Chromate conversion is a process which completely degreases and removes all traces of the oxide film, replacing it by immersion (a rinse) with chromate coating which can then be painted. It is used as a post-treatment for cadmium, zinc and aluminium coatings

Cermet powders
A composite powder of metal and ceramic constituents produced by methods such as agglomeration, sintering and spray drying. Examples include WC-Co, TiC-Ni.

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.

Cavitation Erosion
A form of erosion causing material to be removed by the action of vapour bubbles in a very turbulent liquid.

Case-hardening
See Carburising

Carbonitriding
Similar to Carburising (see below). 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).

Carbide diffusion
A salt bath treatment at about 900oC for high carbon tool steels. Produces a very hard layer of vanadium carbide, typically 10µ thick.

Cadmium ion plating
The deposition of cadmium by a vacuum process to provide galvanic corrosion protection.

Cadmium plating
The electrolytic deposition of cadmium to provide galvanic corrosion protection. Restricted by environmental considerations.

Boronising
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 100µ deep).

Bond coat
A coating applied as an intermediary between the main or top coating and the substrate in order to improve the bond strength.

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.

Bond
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 or metallurgical or a combination of these.

Blasting
A pressurised stream of some materials (Glass, plastic, metal, , etc) applied on a surface to clean and/or roughen. It can be, depending on the media, abrasive an non- abrasive.

Autoclaving
The production of a stable, protective oxide on steel parts by treatment in a pressurised, high temperature steam containing atmosphere.

Arc Wire Spraying
A thermal spray process in which two electrically conducting wires are brought together to form an electric arc. The consequent molten metal is then projected by a air stream towards the workpiece to form a coating.

Anodising
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.

Aluminium Ion Plating
The deposition of aluminium by a vacuum evaporative process. Provides galvanic corrosion resistance. Normally given a passivation treatment.

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 (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-polimerising phathalic anhydride with glycerol, to give a brittle cross. Linked polymer.

Agglomerated powder
A mechanically mixed combination of fine particles of different materials held together with an organic binder and formed into power particles.

Adhesive Wear
Wear caused by sliding surfaces, where surface asperities interact and adhere.

Abrasive Wear
Wear caused by hard, sharp particles.

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.

Abrasive blasting
A pressurised stream of hard metal or oxide grit material used to clean and/or roughen surfaces prior to coating.

Abradable coatings
Coatings which are designed to rub down against the action of a mating surface to form a tight gas or air seal.