A Metallographic Display Method for Abnormal Microstructure of Super 13Cr Steel Billet

Abnormal microstructure was found in a batch of super 13Cr steel billet when metallographic examination, and it was unable to display the microstructure clearly with conventional etchant. By eroding the steel with various etchants alternately, it was found that using three etchants named nitrohydrochloric acid-alcohol solution, picric acid-hydrochloric acid-alcohol solution and potassium ferricyanide-potassium hydroxide aqueous solution to erode alternately could display the abnormal microstructure clearly. Nitrohydrochloric acid-alcohol solution and picric acid-hydrochloric acid-alcohol solution had similar eroding effect, all could display the martensite and ferrite in the billet clearly, but could not display the bainite clearly and ensure the streaky microstructure in the hot work way. Potassium ferricyanide-potassium hydroxide aqueous solution could display other microstructures except martensite, and the streaky microstructure in the hot work way was confirmed to be δ-ferrite.