Ion Implantation

Ion implantation is the process of modifying the physical or chemical properties of the near surface of a solid by embedding appropriate atoms into it from a beam of ionized particles. The use of accelerated electron beams can produce penetration into a substrate surface on the order of 0.1 to 0.2 pm (1000 to 2000 A) at 100 kV, and with higher accelerating voltages the potential for depth of penetration is increased. Surfaces may be treated by ion implantation to produce an effective alloyed surface layer where the composition varies as a function of depth.

Although virtually any element in the periodic table can be injected into near-surface regions of a solid using ion implantation, the ions that improve the properties of steels include:

• Adhesive and abrasive wear: Ni, Ti + C, Y, and Ta + C

• Corrosion and oxidation wear: Cr, Ta, and Y

The most common use of ion implantation for improving the properties of ferrous alloys involves tool steels used in metalworking and machining applications (see the article "Surface Engineering of Specialty Steels" in this Volume). Other end-use applications of ion implantation include improved wear, corrosion, and rolling contact fatigue in bearing alloys such as type 440C stainless steel and 52100 bearing steel (Ref 59, 60).

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