Changing the characteristics of the nitrided layer using three different plasma configurations

Abstract

Direct current (DC) plasma nitriding offers some disadvantages, especially in parts with complex geometries, where the presence of edges is significant, such as gears, molds, and needle punched parts are strongly affected by this effect, leading to irregular formation of nitrided layers and high variation in surface hardness. To solve these problems two techniques were developed as alternatives, namely: pulsed plasma nitriding and cathodic cage nitriding. In this work, these three nitriding techniques were compared using AISI 1045 steel as substrate. Steel discs were nitrided with the purpose of evaluating the influence of these different plasma configurations on the characteristics of the nitrided layer. The treatments in the three techniques were carried out at the same pressure, temperature, time and gas atmosphere. The samples were characterized for the microstructure, microhardness and crystalline phases present. X-ray diffraction with grazing incidence was used to verify the order of the nitrites formed and to estimate the thickness of the single-phase layers. Differences between the configurations with respect to the occurrence of restriction rings, total thickness (x ε + x γ') and relative (x ε /x γ') compound layers were observed.