In this study, the effect of conventional plasma nitriding on chromised tool steel was investigated. The samples were chromised at 11008C for 12 h using thermoreactive diffusion/deposition (TRD). Subsequent tof TRD, specimens were nitrided at 6008C using a DC plasma set-up. Phase composition and surface morphology of the coatings were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) respectively. Corrosion resistance of the samples was investigated by polarisation corrosion test. X-ray diffraction analysis indicated that after chromising, the coating mainly consisted of Cr 7 C 3 , Cr 23 C 6 and Fe 3 C and surface hardness increased from 330 to 1400 HV 0.01 . However, after plasma nitriding, nanosized Cr 2 N, CrN, Fe 3 N and Fe 4 N phases with particle sizes ranging from 32 to 54 nm were formed. The results of polarisation corrosion tests showed that by applying duplex TRD and plasma nitriding, the corrosion resistance was improved.

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