Efeito da fonte de plasma na nitretação de amostras de aço aisi 1045

Abstract

Conventional plasma nitriding (DC) offers some disadvantages, especially in parts with complex geometry, due to problems such as arc, hollow cathode effect and edge effects, which may cause nitrided layer or localized overheating of the part. To solve these problems two techniques were developed as alternatives, namely: pulsed plasma nitriding and cathodic cage nitriding. In this work, the nitriding using these three different techniques was investigated in AISI 1045 steel. Steel discs were placed on the sample holder, both in the horizontal position - with a larger contact area and in the vertical position - with a smaller contact area. To evaluate the influence of the electric contact area. The treatments in the three techniques were carried out at the same pressure, temperature, time and gas atmosphere. It was verified that in order to maintain these fixed conditions, pulsed plasma required the lowest power, followed by DC plasma and cathodic cage treatment requiring more power. The samples were characterized for the microstructure, microhardness and crystalline phases present. X-ray diffraction with grazing incidence was used to verify the order and thickness of nitrites formed. Differences were observed between the three techniques regarding the occurrence of restriction rings and thickness of total (xε + xγ‟) and relative (xε / xγ‟) composite layers. It was also found that the effect on the reduction of electrical contact was more sensitive in the treatment with pulsed plasma. These differences are discussed in light of the mechanisms of each technique