The present state of the nitriding process

Nitriding processes of various metals, mainly steels, in different gaseous atmospheres are reviewed. Addition of a small quantity of gaseous phosphorus to the NH sub 3 in nitriding process, is found to increase the hardness and wear resistance and to reduce frictional effects of a nitrided sample. The nitrided case obtained at a temperature below the eutectoid is found to consist of ( epsilon + gamma ', gamma ') nitride phase (in type 38Kh3MYuA steel). Various rules of formation of the structure and properties of surfaces in nitriding of refractory metals (Mo, Cr, Nb) are discussed, and the influence of nitriding production factors on the structure and properties of the hardened case is determined. A general mathematical model for describing the chemicotechnological processes is presented. Nitriding processes are characterized by the measurements of a large number of interrelated physicochemical parameters. Optimization of the automated systems for controlling of nitriding is predicted.