Abbreviated Title: Thermal etching method

This paper reviews the method of thermal etching for revealing the prior austenite grain boundary in steels. This method involves preferential transfer of material away from grain boundaries, when the steel is exposed to a high temperature in an inert atmosphere. Thus, during austenitisation of a pre-polished sample, grooves are formed at the intersections of the austenite grain boundary with the polished surface. These grooves remain intact after cooling and are clearly visible at room temperature outlining the austenite grain boundaries. However, at very high austenitisation temperatures, those grooves might interfere with the own advance of the austenite grain boundary on the surface. In that case, this technique could lead to a wrong measurement of the austenite grain boundary. The aim of this work is to study the advantages and disadvantages of the technique to reveal the austenite grain boundary in microalloyed steels