Precipitation behavior on carbon steel modified by double glow plasma surface alloying with W and Mo

Many brittle precipitates appeared in the alloyed layers which were formed in surface modified carbon steel by DGPSA (Double Glow Plasma Surface Alloy ing) with W and Mo because of the slow cooling rate in the alloying furnace . As a result the mechanical properties of these alloys were significantly degraded by precipitation of the brittle phase. Phase analysis of the elect ro-extracted precipitates by X-ray diffraction (XRD) revealed that they wer e mainly composed of the p-phase and a small amount of carbide, M6C. In the present study, their microstructures were characterized by optical microsc opy (OM) and scanning electron microscopy (SEM). It was concluded that the chemical components, temperature and time were the main thermodynamic facto rs influencing their deposition. The isothermal transformation (IT) diagram of the precipitates showed that there were two transforming climaxes. Base d on the IT diagram, a technique was developed to depress die precipitate d eposition.