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Amélioration du comportement par implantation ionique^*

Ion implantation applications in mecanics industry^**

Unirec (groupe Usinor - Sacilor), Firminy, France

Abstract

Ion implantation is a well-known process long since in the semi-conductors industry. It has been finding some interesting industrial applications in the metal processing industry for a few years only.

This surface treatment consits in adoping of the superficial layers involving an enrichment in selected constituents using implantation of ions. New metallurgical structures are created. They generally lead to a hardening of the near-surface region and compressive stresses are created in the implanted zone. An improvement of the wear andlor corrosion behaviour of different materials may be observed according to the implanted ion.

The main advantages of this treatment are the following ones

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  the treatment is p erformed under high vacuum ;

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  the interface is not sharp ; there is no risk of delamination or poor adherence ;

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  the treatment is performed at room temperature or low temperature ; thus, no modification of the bulk properties and the piece dimensions can occur ;

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  there is no modification o f the surface roughness : ion implantation can be performed on precision parts which can be treated after manufacture or machining to their final dimensions.

The most developed applications concern nitrogen implantation into steels, for which an improvement of the wear resistance is observed. This improvement depends on the use conditions of the treated pieces (load, temperature) : life-time of toolings for forming, cutting, control,... can be enhanced by a minimum factor from 2 to 10.

Ta or Ti + C implantations decrease the friction coefficient and corrosion phenomena into bearings and gears used in aerospace and aircraft industry. Implantations of tin, chromium and other elements decrease high temperature corrosion by aqueous media of zirconium alloys.

The applications fie ld s mainly concerned by this process are the following ones :

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  high-precision mechanics with highly sophisticated, high-value-added and high-tech components ;

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  aerospace, aircraft, nuclear industry ;

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  biomedical with orthopaedic implants.