Nitriding – Its Growth and Tribological Benefits for Surface Engineering

Nitriding is here to stay. Various nitriding methods, their history and processing options are compared in this review.

A critical question is, “Why has the nitriding field grown so rapidly in recent years?” The answer is complex, but this paper considers the question by looking at two factors: tribological properties of nitrided layers and advances in equipment and processes which have improved reliability, repeatability and flexibility.

Nitriding has a rich history spanning over 100 years. It is the nitrided surface itself that is largely responsible for increased interest. The surface engineering that is possible along with its predictable and relatively distortion-less results are huge factors in its growth.

Two nitriding technologies have become dominant in recent years: gas and ion. Gas nitriding has gone from simple atmosphere furnaces using single or two-stage processes, to advanced vacuum purged equipment that can carefully predict and control nitriding potential. Ion (plasma) nitriding has progressed from plasma heating in cold wall vacuum furnaces to the use of hot wall technologies and pulsed plasma. Both processes and their advances are discussed as each offers engineers choices that result in properly nitrided parts capable of meeting the most stringent requirements.