Novel Etching Technique for Delineation of Prior-Austenite Grain Boundaries in Low, Medium and High Carbon Steels

Abstract

The etching of prior austenite grain boundaries in martensite for detailed quantitative metallography of low to high carbon steel has been carried out using aqueous solutions of picric acid containing different wetting agents. The choice of wetting agent was shown to be dependent on the carbon content of the steel, with sodium dodecyl sulfate (SDS) being more suitable for use with low and medium carbon steels, whereas sodium dodecylbenzene sulfonate (SDBS) was shown to be more appropriate for high carbon steels. It is also recommended that, for a particular steel, a variety of temper treatments should be carried out in order to reveal grain boundaries, particularly where more detailed results than simple grain size measurements are required. Finally, the use of dummy specimens prior to etching of the real samples was shown to reduce the need for re-polishing and re-etching of the samples.

A new approach to etching low‐carbon microalloyed steels to reveal prior austenite grain boundaries and the dual‐phase microstructure

“… 7 Sodium dodecyl sulphate (SDS) has been used as a wetting agent in previous studies, showing good results with low and medium carbon steels. 13 Other authors also reported that the addition of HCl increases the attack on the phosphorus‐rich regions, better outlining the prior‐austenite grain boundaries in steels. 14 , 15 , 16 …”

“…7 Sodium dodecyl sulphate (SDS) has been used as a wetting agent in previous studies, showing good results with low and medium carbon steels. 13 Other authors also reported that the addition of HCl increases the attack on the phosphorus-rich regions, better outlining the prior-austenite grain boundaries in steels. [14][15][16] In this research, chemical etching based on picric acid with additions of sodium dodecyl sulphate and some drops of hydrochloric acid (HCl) was investigated to reveal the prior-austenite grain boundaries in microalloyed steels at different normalisation temperatures after hot-rolling.…”

“…Wetting agents or surface‐active agents (surfactants) are added to etchants to improve grain boundary delineation in steels acting on the etching speed or selectivity modification 7 . Sodium dodecyl sulphate (SDS) has been used as a wetting agent in previous studies, showing good results with low and medium carbon steels 13 . Other authors also reported that the addition of HCl increases the attack on the phosphorus‐rich regions, better outlining the prior‐austenite grain boundaries in steels 14–16 …”

One-Step, Catalyst-Free Formation of Phenol from Benzoic Acid Using Water Microdroplets

“…14 Furthermore, phenols are common moieties in dyes, as evinced by picric acid, which is both a yellow dye and an important metal etchant. 15 Owing to their numerous applications, there is high commercial demand for phenol derivatives. Historically, phenol was extracted from coal tar, but at the present time most phenol is derived from petroleum.…”

“…Similarly, the penicillin drug amoxicillin contains a phenol core, as do propofol, which is used to induce general anesthesia, and tolcapone, which is used to treat Parkinson’s disease. , Many other bioactive moleculessuch as the flavoring agent vanillic acid and the antioxidant gallic acidalso contain phenols . Furthermore, phenols are common moieties in dyes, as evinced by picric acid, which is both a yellow dye and an important metal etchant …”