Diffusion: involves the alteration of surface layers of a material by diffusing atoms of a different material into the part surface.

It is used for surface hardening and increasing wear resistance, typified by carburizing (C), nitriding (Ni), carbonitriding (C, Ni), chromizing (Cr), and boronizing (Bo).

Chromizing can also improve corrosion resistance besides increasing part hardness.

Aluminizing (calorizing) and siliconizing can improve corrosion resistance and high-temperature oxidation resistance in carbon steel, alloy steels, and alloys of nickel and cobalt.

Diffusion method:

Pack diffusion: workparts are surrounded with aluminum powders plus other ingredients to promote the diffusion reactions. The diffusion coating is carried out at temperatures between 1650⁰ to 2200⁰ F (900⁰ to 1200⁰ C). The thickness ranges from 0.010 in. (0.25 mm) to 0.040 in. (1.0 mm).

Slurry method: fine aluminum powders mixed with binders and other ingredients in water are applied to the work by dipping or spraying.

Ion Implantation: involves embedding atoms of one (or more) foreign element(s) into a substrate surface using a high-energy beam of ionized particles.

It is used to alter chemical and physical properties of the layers near the substrate surface.

Created by Dr. Wang