The present concerns surface modification of low alloy CrMoV steel by following the route of plasma nitriding for the improvement of hardness. Plasma nitriding was performed at a low temperature of 450 o C. The maximum hardness at this lower temperature was found to be ~1270 Hv after nitriding. At 550 o C though the hardness improvement near the surface region was similar but the core hardness was reduced. XRD studies revealed various nitrides of iron (γ′ (Fe 4 N) and ε (Fe 2-3 N)) with the ε nitride as the dominant phase. SEM analyses revealed the surface microstructure with almost no white layer. EDS point analyses shown the signature of N on the surface layer. It has been concluded in this study that the hardness of 90CrMoV8 steel can be improved significantly even at a low temperature of 450 o C without any of risk of the loss of core hardness.

This study presents the plasma nitriding of Cr-Mo-V tool steel to protect it from environmental degradation. The steel samples after metallographic polishing were nitrided in the glow discharge plasma of N 2 and H 2 gas mixture (80:20). Nitriding was performed at two different temperatures, a lower temperature of 450°C and the higher temperature of 500°C. The potentiodynamic polarization tests in 3.5% NaCl electrolyte had shown the enhancement of corrosion resistance of steels after nitriding. X-ray diffraction (XRD) studies and scanning electron microscopic analysis coupled with energy dispersive spectroscopic analysis (SEM/EDS) was performed to understand the modification of surface microstructure. XRD analysis of the nitrided steels revealed the presence of c 0 -and e-nitrides of iron, which were responsible for the improvement of corrosion resistance.

No abstract

Present study concerns with the effect of plasma nitriding on hardness of low alloy steel. Plasma nitriding had been performed at elevated temperature of 500°C which improved the hardness to $1200 H v. The case depth was found to be $80 mm. With the variation of time the case depth also varied. The plot of the square of the case depth vs. nitriding time and the corresponding line drawn by a linear regression and extrapolation passes almost through the origin. From the plot the nitrogen diffusion coefficient calculated to be $2.23 Â 10 À13 m 2 /s. The structural and morphological studies have been made by following the X-ray diffraction (XRD) and scanning electron microscopic (SEM) and EDS analyses. XRD revealed the presence of a-Fe, c 0 and e phases.

No abstract