Plasma carburizing has opened the door to take advantage of higher processing temperatures than those used with conventional gas carburizing.
Surface treatment, also known as surface modification, surface engineering, and case hardening, can be divided into two distinctive groups: deposition and diffusion techniques. Deposition techniques are characterized as transporting a metallic substance from a source metal and depositing it onto the surface of another metal. These techniques include electroplating, hard coating (thermal flame spray), physical vapor deposition (PVD) and chemical vapor deposition (CVD). Diffusion techniques are further subdivided into two distinctive categories: thermochemical and thermal. Thermo-chemical diffusion techniques, namely nitriding, carburizing, carbonitriding, ferritic nitrocarburizing and boronizing are characterized as diffusing an element, such as carbon, nitrogen, sulfur, boron, and oxygen, into the surface of the steel by the application of the appropriate amount of heat, time, and the steel surface catalytic reaction. Figure 1 shows the process temperature range and process characteristics of different thermochemical diffusion techniques. Thermal techniques are those that modify the surface phases of steel containing sufficient carbon to allow the transformation from austenite to martensite when the appropriate amount of heat is applied to the immediate surface. This sometimes is known as phase hardening and is applied to processes such as flame, laser, induction, and electron beam.