Evaluation of Etching Process Parameter Optimization in the Objective Specific Microstructural Characterization of As-Cast and Heat Treated HCCI Alloy

Abstract

Abstract The optimization of the etching process parameters in high chromium cast irons (HCCI) for general microstructural observation, eutectic and secondary carbide quantification and 3D analysis of the carbide network is indispensable for further microstructure-properties correlation. The main aim of the current work is to evaluate the efficacy of certain etchants to aid in ‘objective specific' microstructural characterization of a 26 % Cr HCCI alloy in the as-cast (AC) and heat treated (HT) state. Samples were etched with various solutions, including Vilella's reagent, Nital, Murakami's reagent and its modification, and two other etchants. It was seen that specific etchants are needed depending upon the final objective and the results are reliant on their selection and optimal usage. Etching the AC and HT samples with Vilella's reagent for 7 s was sufficient to develop a contrast between the phases which was observed both in confocal laser scanning microscope (CLSM) and scanning electron microscope (SEM). Murakami's reagent and a modification of the same, were used in successfully quantifying the eutectic and secondary carbide volume fraction (CVF) in the AC and HT samples, respectively. Consequently, the knowledge gained in this study will be used as a basis for further microstructural analyses of these alloys and be applied to other alloys in the family.