Grade 315 steel (Fe-2.9 Cr--1.7 W- 0.7 Mo -0.3 Mn-0.3 Si-0.2 V- 0.1 Ni-0.13 C-0.01 N) was
chromized by the halide-activated pack cementation (HAPC) process. Key process parameters, i.e.,
coating temperatures and pack compositions, were investigated. Ammonium chloride-activated packs
in the 700-1000°C range produced coatings nominally in the 1-8 µm range, as determined by optical
and scanning electron microscopy (SEM). Coatings applied in the 900-1000°C temperature range
resulted in Cr-rich coatings. The predominant phase in the coating was identified as Cr23C6 by X-ray
diffraction. In addition, the presence of chromium nitride, Cr2N, was observed in the coating.
Key words: Halide-activated pack cementation, grade 315 steel, coatings, chromizing, corrosion,
super-bainitic steel