Volume 58, Issue 8

Considering the dependance of materials’ properties on the microstructure, it is imperative to carry out a thorough microstructural characterization and analysis to bolster its development. This article is aimed to inform the users about the implementation of FIJI, an open source image processing software for image segmentation and quantitative microstructural analysis. The rapid advancement of computer technology in the past years has made it possible to swiftly segment and analyze hundreds of micrographs reducing hours’ worth of analysis time to a mere matter of minutes. This has led to the availability of several commercial image processing software programs primarily aimed at relatively inexperienced users. Despite the advantages like ‘one-click solutions’ offered by commercial software, the high licensing cost limits its widespread use in the metallographic community. Open-source platforms on the other hand, are free and easily available although rudimentary knowledge of the user-interface is a pre-requisite. In particular, the software FIJI has distinguished itself as a versatile tool, since it provides suitable extensions from image processing to segmentation to quantitative stereology and is continuously developed by a large user community. This article aims to introduce the FIJI program by familiarizing the user with its graphical user-interface and providing a sequential methodology to carry out image segmentation and quantitative microstructural analysis.

For numerous steel grades, detailed descriptions of different etching techniques and etching times for microstructural analysis are available. However, there are only few reference works for low-alloyed cast iron. Particularly for complex microstructures with combined fractions of bainite, ferrite, pearlite, retained austenite, carbides and martensite, there are only few detailed collections. In addition, the effects of the etchants are rarely investigated for the same image section. Therefore, this study will exclusively compare identical microstructural regions and the effect of different etchants on them. Two specific sample areas were selected in a low-alloyed cast iron and the effect of both surface removal etching and tint etching reagents on them was examined under a reflected light optical microscope and a scanning electron microscope. The results of the study have shown that some etchants for complex microstructures are only suitable in case potentially present phases are already known. However, the combined use of two etching solutions in particular, led to a very detailed and highcontrast image, capable of revealing and resolving microstructures with a variety of phases.

Elastic sealing elements used in combustion chamber assemblies of heavy-duty gas turbine engines used for power generation fractured from high cycle fatigue failure. The subject assembly was burner rig tested in a special testing facility. It was speculated that the affected spring seals likely failed due to forced excitation during burner rig testing, since no material imperfections or fabrication flaws, such as spot weld imperfections, were detected that could have contributed to the failure.