Best Practice for Metallurgical Quality Evaluation of Nitrided Components

Surface hardening by nitriding is a commonly used heat treatment to enhance tribological characteristics, fatigue and corrosion resistance of ferrous components. Nitrided white layer is known for its high hardness but also for its brittle nature. It is not uncommon to see white layer chipping or breakaway during metallurgical sample preparation that may complicate the analysis of the ‘true’ white layer characteristics in the microstructure of the nitrided load. This paper discusses the results of the several studies performed to evaluate the effect of cutting and polishing operation, polishing pressure, use of foils, and Ni plating. Best practice procedure has been developed for metallurgical sample preparation to minimize uncertainty in parts quality evaluation.