A technique for the removal of oxides from the fracture surfaces of HAYNES® 230® alloy

A technique has been developed for the removal of oxides that often cover fracture surfaces of Ni-Cr superalloys following high-temperature failures in air. The technique consists of two steps. The sample is first boiled in a potassium permanganate solution for 1 h and then electrolytically cleaned in an alkaline solution for 5 min with the sample as the cathode. An oxide-free fracture surface of the HAYNES® 230® alloy was prepared by tensile overload at room temperature. The fracture surface was then subjected to a thermal exposure at 927 °C in air. As the exposure time increased, a tenacious oxide film developed and became thicker, making it impossible to identify the mode of fracture. Except for dislodging the carbides, the technique developed was capable of removing the oxides completely without altering the fracture surface morphology.