Ion implantation is a surface treatment process in which ions of nitrogen or carbon are accelerated and made to penetrate the surface of a component to impart wear resistance.
The atoms of nitrogen or carbon are converted into an ion form by electron collisions in a plasma, focused into a stream using magnets and accelerated by a voltage gradient towards the substrate. Using this approach, a high energy ion beam (50 to 200keV) can be directed onto the component surface.
Ion implantation is not a surface coating process, it is a technique which implants ions of nitrogen or carbon below the substrate surface and into the matrix of the substrate material. Implantation depths range from about 0.1 to 0.3µm. It is analogous to diffusion processes such as carburising or nitriding, but requires a much lower substrate temperature of about 200°C. Ion dosage varies from 1015 to 1018 ions/cm2 dependant on ion species, component material and property requirements. It also has the advantage of being able to implant ions which would not normally diffuse or are insoluble in the substrate material.
Ion implantation is a batch process and has a treatment time of about 2 to 10 hours. The process is much more reproducible and controllable than most other conventional surface treatments. After ion implantation, the component surface requires no further treatment prior to use.
The process is used to harden the surfaces of steels and cemented carbides used for tooling in cutting, pressing, punching, extrusion, moulding and stamping processes. Most ions are implanted to improve wear, oxidation and fatigue resistance. The process may be unsuitable for components that reach high temperatures, above 800°C. Implanted nitrogen ions have high mobility at these temperatures and may rapidly diffuse away from the surface.
Ion implantation can be carried out on virtually all ferrous and non-ferrous materials, but is presently used mainly for steels and cemented carbides. The process can readily be applied to components that already have a surface coating, such as chromium plating.
FAQ: What is plasma carburising/plasma nitriding?
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