Abstract
Plasma nitriding is the low-nitriding potential process characteristic of its ability to nitride stainless steels and powder metal components without special preparations or unusual controls. This is possible thanks to its specific mechanism and presence of sputtering, the phenomenon which occurs throughout the entirety of the process. Typically, the plasma process produces a nitrided layer with the gamma prime-Fe4N compound zone on top of it. This is very important whenever a good bending fatigue property of the part is needed. The abovementioned materials can also be treated with conventional gas nitriding, but with special cycles requiring very sophisticated control. Mechanical masking, protection from direct contact of the glow discharge with a given surface, prevents hardening of the mechanical components in the areas, which should stay soft, such as the threads, small holes and others. The uniformity of nitriding large/long parts, such as shafts and extruder screws, allows economical treatment in module-type vessels. Easy doping of the plasma with hydrocarbons allows for forming a thicker compound zone of the ε-Fe2NxCy-type. This significantly improves tribological and anticorrosion properties. Enhancement of the wear properties for higher temperature applications is possible when doping plasma with silicon is applied. The plasma process can also be carried out at the temperature range 350-400° C to all types of stainless steels. Formation of expanded austenite at such a low temperature is possible when nitrogen or carbon is diffused. This is applied for stainless steels where their corrosion resistance must be supported or enhanced in their wear resistance applications. Examples of the best applications will be presented.
