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

Abstract

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.

The Effect of Thermal Processing and Chemical Composition on Secondary Carbide Precipitation and Hardness in High-Chromium Cast Irons

“…Temperatures, heating/cooling rate and holding times used for the different HT steps, as described in ''Experimental'' section, are the same as previously applied for the HCCI_16%Cr. 9,21 Comparing the results corresponding to HCCI_26%Cr with the previously obtained in HCCI_16%Cr, 9,21 some differences can be appreciated, principally related to the precipitated SC. For instance, in HCCI_16%Cr only rounded M 7 C 3 carbides were observed after all the heat treatment steps, whereas for the HCCI_26%Cr, different types of carbides were identified depending on the thermal processing, as shown in Figure 1.…”

Complex Corrosion Properties of AISI 316L Steel Prepared by 3D Printing Technology for Possible Implant Applications

“…Due to the shape of the analyzed sample, the working distance was 11-12 mm. The metallography observations were performed on samples after mechanical polishing using equipment and diamond suspensions made by Struers (Roztoky, Czech Republic) with chemical etching ( 22• C/60s) in a modified Vilella's reagent [21] containing 10 parts 35%HCl, 10 parts distilled H 2 O and 1 part 65% HNO 3 . The image capturing and evaluation was performed by an Olympus IX70 inverted metallographic microscope (Olympus, Praque, Czech Republic)…”

Analysis of the carbide precipitation and microstructural evolution in HCCI as a function of the heating rate and destabilization temperature

“…Post HT, the samples were ground and polished following the procedure described in 17 , 18 to obtain a scratch free, mirror polished surface. For general microstructure revelation, the samples heated up to 800 °C were etched with Villella´s reagent (1 g picric acid + 5mLHCl + 95mLC 2 H 5 OH) 8 , 17 , whereas samples heated up to 900 and 980 °C were etched with Nital (98 mL ethanol + 2 mL nitric acid + 0.5 mL HCl) 17 . The microstructure was analysed using a FEI Helios Nanolab field emission scanning electron microscope (FE-SEM) working with an acceleration voltage of 5–15 kV and a beam current of 1.4 nA.…”