The range of processes used to treat the surfaces of engineered materials is quite wide and the results vary on a number of different factors, including the process, the coating media and the substrate surface. If the universe of surface treatments were to be categorized according to two criteria - the first being that the metallurgy produced by the process is equivalent and the second being that the equipment used to implement the process is related - then all surface treatments can be classified into one of six categories:

HEAT TREATMENTS -

Heat treatments affect the entire volume of the substrate material and extend to the surface region. Heat treatments can be performed either in air or in a vacuum chamber.

CASE HARDENING PROCESSES -

Case hardening processes produce a hardened case layer INSIDE of the surface of a substrate by thermally-driven diffusions of species, such as C, N, or B. The case hardening process can be implemented in a salt bath at atmospheric pressure, an elevated pressure chamber (gas nitriding, carburizing) or a vacuum chamber (ion nitriding, carburizing).

CHROME PLATING, CONVERSION COATING & ANODIZING PROCESSES -

Chrome plating, conversion coating and anodizing processes are used to deposit coatings ON the substrate surface, rather than inside it. They are all chemical processes implemented in an aqueous media contained in a tank at atmospheric pressure. A wide variety of metallic and metallic oxide coatings can be deposited.

PLASMA SPRAYING -

Plasma spraying is used to build thick coatings ON the substrate surface and there is always a distinct interface between the coating and the substrate. Plasma spraying can be done in air at atmospheric pressure or in a low-pressure chamber and is usually used to deposit thick metallic or oxide coatings.

PHYSICAL VAPOR DEPOSITION (PVD) COATINGS -

Physical vapor deposition is used to deposit thin hardcoatings ON the substrate surface. A limited variety of metallic nitride, carbide, oxide and diamond-like carbon coatings can be deposited. A vacuum environment is required.

ION BEAM ENHANCED DEPOSITION (IBED) COATINGS -

Unlike all conventional treatments, IBED is a physical - as opposed to a chemical or thermal - process. The temperature rise during processing can be held below 200 degrees Fahrenheit so no thermally-induced volumetric changes in bulk properties or physical dimensions are produced. IBED processing combines the benefits of thermal diffusion processing and conventional coating technologies because the coating atoms first penetrate INTO the substrate to form a case layer in the surface, and then are GROWN OUT from this case layer as a thick coating. Driven in kinetically instead of thermally, IBED coatings are "ballistically bonded" to the substrate, thus forming a metallurgical bond that is much stronger than a mechanical or Van der Waals bond. And because the IBED process is kinetically driven, solid solubility limits can be exceeded which is the mechanism that allows deposition of a variety of types of coatings on virtually any substrate material.