In ferrous materials such as steel, which accounts for the vast majority of tribological components, the primary basic mechanism of surface hardening is by phase transformation to form the relatively hard martensitic phase in the surface layer. The process involves heating of the material, at least in the surface region, to a temperature in excess of the austenitizing temperature, then followed by rapid cooling thereby transforming the austenite phase into martensite. The method of application of heat is often the distinguishing feature of the numerous thermal hardening techniques. Heat can be applied in the conventional furnace, laser, electricity (induction), flame and many others. Each of the various methods has their own advantages and disadvantages. The method of choice is often guided by the specific component requirements and economics. Some variant of the thermal heat treatment process of steel material can also involve the change of the chemistry or composition of the near-surface material. These thermo-chemical processes include carburizing, nitriding, boriding, etc.