Boron–aluminide coatings applied by pack cementation method on low-alloy steels

A simultaneous one-step boroaluminizing process has been performed on a 2.25Cr–Mo steel by means of pack cementation method using a B/Al boriding powder. Three distinct regions were found in the coatings consisting of an outer Al-rich layer, a transition region containing Al and Fe and an inner layer containing mostly B and Fe. The layers were characterized by means of optical and scanning electron microscopy (SEM) in terms of coatings morphology and thickness. X-ray diffraction (XRD) was used in order to detect the phases formed and the presence of iron aluminide and boride phases in the coating due to the boroaluminizing process.