International Journal of Computational Engineering Research||Vol, 03||Issue, 5|| www.ijceronline.com ||May ||2013|| Page 69 Ni-Based Cr Alloys and Grain Boundaries Characterization 1 Aezeden Mohamed and 2 Tarek Mohamed 1 (Faculty of Engineering and Applied Science, Memorial University, St. John’s, NF, Canada, A1B 2X3) 2 (Waha Oil Company, Engineering Research Department, Tripoli, Libya,) amohamed@mun.ca . I. INTRODUCTION Ni-base alloys are widely used in space and marine environments due to their high strength, ductility and corrosion resistance. It is well documented that grain boundary serration occurs by the formation of precipitates along grain boundaries [1–6]. Investigators have found that, grain boundary serrations in stainless steel improve creep and fatigue properties of this alloy [5]. Furthermore, it has been found that in alloys 304 and 316 stainless steels, when grain boundaries are serrated the amount of carbides reduced and carbide precipitate shape changed from triangular to planar which has been proven to improve fatigue properties for those alloys [7]. In other studies [8,9] it was found that grain boundary serration occurs before carbides are precipitated on the grain boundaries. These studies also claim that when precipitation of carbides eventually occurs, planar carbides form along serrated boundaries while triangular carbides form along the unserrated boundaries. This contradicts previous reports that claim that grain boundary serration is due to precipitation of phases in the grain boundary serration. It has been found that the phase precipitated on grain boundaries in stainless steels are M 23 C 6 type carbides [10-17]. Therefore, the main purpose of this study is to investigate the effect of carbon content on the morphology of grain boundary serration. Figure 1Model shows grain boundary serration formation in stainless steel due to M 23 C 6 precipitation, (a-a) grain boundary prior to formation of M 23 C 6 ; (b-b), (c-c) serrated grain boundary after formation of M 23 C 6 [10]. II. EXPERIMENTAL PROCEDURE In order to investigate morphology of grain boundary serration in three kinds of Ni-base alloys are Hastelloy C22, Inconel 600, and Inconel 601, specimens were all solution heat treated at 1000C for 1 hour followed by air cooling. Specimens were investigated under constant conditions using scanning electron microscopy and energy dispersive spectroscopy SEM-EDS. ABSTRACT: Three Ni-base alloys Hastelloy C22, Inconel 600, and Inconel 601 with carbon contents of 0.003, 0.05, and 0.3 wt. % respectively were used to investigate the effect of carbon on the morphology grain boundaries at constant heat treatment. From microstructural characterization and analysis, it was observed that the lowest carbon content resulted in planer character grain boundaries, the carbon content produced wavy grain boundaries and the highest carbon content produced saws-teeth grain boundaries. It is suggested that higher carbon contents result in the formation of occurred grain boundaries due to the formation of M 23 C 6 morphology. Keywords: Boundary, Carbides, Grain, Hastelloy, Inconel, Morphology, Serration, Triangle