FLUIDISED BED ON COATING FORMATION ON PRE-NITROCARBURISED PLAIN CARBON STEEL

摘要

CrN coatings were formed on plain carbon steel by pre-nitrocarburising, followed by Thermoreactive Deposition and Diffusion (TRD) in a fluidized bed furnace at 570℃. During TRD, chromium was transferred from chromium powder in the fluidized bed, to the nitrocarburised substrates by gas-phase reactions initiated by reaction of HCl gas with the chromium. The microstructural processes occurring in the white layer caused by nitrogen diffusion towards the surface during this stage, were studied. TRD atmospheres employing inert gas and HCl, or inert gas, H_2 and HCl were compared. Surface characterization was performed by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Glow Discharge Optical Emission Spectroscopy (GDOES).