ETCHING AND IMAGE-ANALYSIS OF PRIOR AUSTENITE GRAIN-BOUNDARIES IN HARDENED STEELS

Aqueous solutions saturated with picric acid and containing sodium trideylbenzene sulfonate and HCl effectively reveal prior austenite grain boundaries in hardened steel. Repolishing and re-etching increase grain boundary contrast relative to the matrix, and provide grain boundary networks that can be readily measured by an operator. However, not all boundaries are continuous, and, depending on the care and time available for etching, not all intragranular features can be removed. The latter features cause difficulty in image analysis, but we have found that they can be minimized by defocussing and examining the microstructure at low magnification. © 1991.