Evaluation of the Etching Process for Analysis of Secondary Carbides in HCCI by Optical and Confocal Laser Microscopy

This work evaluates different etching solutions, including Marble, Vilella, RNO and Murakami, used with the purpose of revealing secondary carbides precipitated in high chromium cast irons after heat treatments for their analysis with optical microscopy (OM) and confocal laser scanning microscopy (CLSM) and the posterior binarization of the obtained images. Etching with Marble and Murakami showed the best results for revealing secondary carbides when OM is used for the characterization. The etching parameters to reveal secondary carbides resulted to be different depending on the technique used for their evaluation, i. e. the etching time for a good phase contrast was not the same when an OM or a CLSM is used for the characterization. It was shown that the selection of the proper etchant and etching procedure is of utmost importance for the subsequent particle characterization by means of image analysis. Moreover, the results shown here intend to act as a guide for the optimization of etching parameters with the aim of finding the most suitable solution to reveal the carbides.