Wear Behavior and Microstructure Changes of a High Chromium Cast Iron: The Combined Effect of Heat Treatment and Alloying Elements

The microstructure and wear behavior of a manganese and niobium alloyed high chromium cast iron were examined and compared to an as-cast chromium cast iron. Three heat treatments were applied: quenching at 930, 980 and 1030 degrees C followed by tempering at 250 degrees C. The microstructures were characterized by optical and scanning electron microscopy equipped with an energy dispersive spectrometer. The Vickers microhardness (HV) were measured. X-ray diffraction tests were carried out in order to identify the nature of the existing crystallographic phases in each studied sample. The tribological behavior was studied in the dry state under a load of 10 N at room temperature. The friction coefficient was recorded. The wear mechanism of the investigated is observed by optical microscopy. The obtained results show that the as-cast microstructure of the studied chromium cast iron samples consists of an austenitic matrix and a complex eutectic carbide network of M7C3 type. The applied heat treatments have affected the microstructure and have promoted the formation of martensite, retained austenite and secondary precipitations. The addition of niobium and manganese also shows a refinement on the microstructure, this effect is observed on the dimensions of the dendrites which appear finer in the chromium cast iron alloyed with Mn and Nb.