Microstructure and structural behavior of ion-nitrided AISI 8620 steel

The ion nitriding behavior of AISI 8620 alloy steel has been examined under varying process conditions. The process variables included time (1-8 h), temperature (450-600 degreesC) and a 70% H-2-30% N-2 gas mixture. The structure of the compound layer was studied by X-ray diffraction (XRD) and light optical microscopy. These studies showed that the thickness of the compound layer increased with increasing time at 500 degreesC and 550 degreesC; however, at 600 degreesC, the thickness of the compound layer decreased with increasing time. Phase changes during ion nitriding at 600 degreesC have been investigated using XRD, scanning electron microscope (SEM) and energy dispersive spectrometry (EDS). The maximum surface hardness was obtained at 500 degreesC for 8 h and a larger diffusion layer was obtained at 600 degreesC for 8 h. A braunite Layer formed at 600 degreesC. (C) 2001 Elsevier Science Inc. All rights reserved.