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Science, Maths & Technology
Ion implantation
Within a vacuum chamber, surfaces to be hardened are bombarded with a high energy stream of ions that penetrate the surface. This is not a diffusion process. Once impregnated into the surface, the ions (usually carbon or nitrogen) lose their energy and stop moving. The compressive stresses generated in the surface layers improve mechanical and ...
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Science, Maths & Technology
Induction/flame hardening
Induction hardening involves using induced electrical currents to very rapidly generate heat via hysteresis, usually in a workpiece made from medium to high carbon steel. Flame hardening uses oxy-fuel burners to heat the workpiece via conduction. Both procedures use quenching after heating, often followed by tempering and/or stress relieving.
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Science, Maths & Technology
Carbonitriding / carburising
Carbon or carbon and nitrogen together, in a medium of gas, solid or liquid, are diffused into the surface of component(s), particularly those made from low carbon steels. Changes to the chemical composition of the surface (austenite) lead to high carbon content in the surface material, which when quenched transforms to a hard coating (martensite).
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Science, Maths & Technology
Plasma arc spraying
A stream of high temperature plasma and the powder coating material are carried via an electric arc, to the workpiece to be coated.
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Science, Maths & Technology
Plasma nitriding/carburising
The surface of the workpiece is saturated with either carbon atoms (carburising plasma) or nitrogen atoms (nitriding plasma). Carburising, carried out at high temperatures, involves bombarding the surface to be coated with the plasma. The workpiece is held under vacuum until carbon atoms have diffused into the heated surface, to form hardened ...
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Science, Maths & Technology
Laser surface treatment
A surface treatment used to harden or clad surfaces of ferrous metals. For hardening, a laser beam with a high power density heats a small area on the surface of the workpiece, causing changes to the atoms in the lattice of the material (austenite). As the beam moves away, to another spot on the surface, the heated area is rapidly cooled by the ...
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Science, Maths & Technology
Thermal spraying (Hardfacing)
The surface to be coated is cleaned and roughened, to provide adhesion of molten particles in the coating material when it’s sprayed onto the workpiece. The coating material is melted using thermal, electrical or thermochemical means. Molten materials (metals, alloys or ceramics) are sprayed onto a substrate material (the component) where they ...
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Science, Maths & Technology
Physical vapour deposition (PVD)
Evaporated atoms from the coating material are transported, in the form of a pressurised vapour under vacuum, to the workpiece to be coated. Vapour is deposited onto the surface of the workpiece, where it condenses forming very thin layers of coating at nanometre thickness. Multilayer coatings can be built up.
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Science, Maths & Technology
Toyota diffusion (TD)
Elements such as vanadium, niobium and chromium, are diffused into a ferrous metal component, via a chemical reaction that takes place in a high temperature salt bath with a borax mix. After quenching and tempering, a very hard carbide layer remains on the surface of the component. This surface coating is often applied to extend the life of ...
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Science, Maths & Technology
Phosphating (non-electrolytic coatings)
Often used on ferrous metals to provide a protective, corrosion-resistant phosphate film prior to painting. The phosphate coating, created via a precipitation reaction, adheres well to the base metal, also offering good surface adhesion for paint or powder coating.
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Science, Maths & Technology
Anodising
An electrochemical process causes a layer of anodic oxide to form on the surface of a non-ferrous base metal, such as aluminium. Oxide provides protection from corrosion and wear, as well as a good surface finish for painting. Also used for decorative effect.
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Science, Maths & Technology
Electroless plating
Metal ions within a chemical solution, using an autocatalytic reaction, deposit a uniform layer onto the surface of prepared (cleaned and etched) material to be coated. The process is purely by chemical reduction and no electrical current is necessary.