Selection of Metallographic Erosion Agent for Invar Alloys

Different erosion agents were used to erode metallographic specimens of invar alloys. The erosion effect of different erosion agents on hot-rolled and aged invar alloy metallographic specimens was studied. The results show that the grain boundaries of hot-rolled and aged invar alloys were relatively shallow after eroded by hydrogen peroxide hydrofluoric acid solution, and the precipitate profile was not clear. The low magnification metallographic erosion agent and the ferric chloride alcohol saturated solution could clearly show the grain boundaries of the invar alloys, but the fine precipitates were easy to be eroded and spallated. Aqua regia solution could maintain the integrity and clear appearance of precipitates in the invar alloys, but the grain boundaries corrosion was not clear. Electrolytic corrosion could clearly show the grain boundaries and precipitates of the invar alloy and maintain the integrity of the precipitates.