Effects of plasma nitriding on low alloy Cr-Mo-V steel

In this study the effects on resistance to corrosion of a low alloy steel after plasma nitriding has been reported. Nitriding was performed at a low temperature of 450 °C and also at 520 °C for the same duration of 10 h in the plasma of nitrogen and hydrogen (80:20) gas mixture. Sample holder was biased at -250 V and the working pressure was kept at around 500 Pa. After nitriding the steel samples along with the bare steel were exposed to X-ray diffraction (XRD) to understand the phase formation. For the assessment of corrosion resistance properties potentiodynamic polarization tests of the bare and plasma nitrided steels in 3.5% NaCl electrolyte were performed. Nitriding at 520 °C had shown the best corrosion resistance. However, broad passivation region had been shown after nitriding at 450 °C

Low Temperature Plasma Nitriding of Low Alloy Steel for the Enhancement of Hardness

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 oC. The maximum hardness at this lower temperature was found to be ∼1270 Hv after nitriding. At 550 oC though the hardness improvement near the surface region was similar but the core hardness was reduced. XRD studies revealed various nitrides of iron (γ′ (Fe4N) and ε (Fe2–3N)) 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 oC without any of risk of the loss of core hardness

Low-temperature plasma nitriding of martensitic stainless steel

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 N2 and H2 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 γ′- and ε-nitrides of iron, which were responsible for the improvement of corrosion resistance

Glow discharge plasma nitriding of low alloy steel

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 Hv. 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 co-efficient calculated to be 2.23 10 13 m2/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, c0 and e phases

Elevated temperature plasma nitriding and effects on electrochemical properties of steel

Surface modification of tool steel had been performed by utilizing plasma nitriding at elevated temperature by varying the exposure time. The nitrided steel had shown significantly enhanced corrosion resistance properties. X-ray diffraction (XRD) had revealed the presence of FexN (x = 2–3, 4) in the surface modified microstructure after nitriding. In an environment of NaCl potentiodynamic polarization and impedance (EIS) tests of steel with and without nitriding had been performed. Both these tests had shown the improved resistance to corrosion of the steel after nitriding

Plasma Nitriding of 90CrMoV8 Tool Steel for the Enhancement of Corrosion Resistance

In the present studies, efforts were made to improve corrosion resistance of 90CrMoV8 tool steel by following plasma nitriding. Plasma nitriding of this steel at 500 oC for6and 8 h significantly improved the corrosion resistance when compared to the as-received steel. X-ray diffraction reveals γ′ (Fe, Cr)4 N) and ε ((Fe, Cr) 2–3 N) phases formed after nitriding. Potentiodynamic polarization tests in 3.5% NaCl reveal that plasma nitriding significantly improved the corrosion resistance as compared to untreated steel. The improvement in corrosion resistance may be attributed to the N solid solution and the presence of Fe-nitrides formed in the compound laye

Electrochemical study on the corrosion resistance of surface modified Cr-Mo-V steel by elevated temperature plasma nitriding

This study presents the effect of plasma nitriding on corrosion resistance of low alloy 90CrMoV8 steel. At a selected temperature of 500 °C, nitriding was performed by varying the exposure time. X-ray diffraction of nitrided steel revealed the presence of Fe, γ′ (Fe, Cr)4Nand ε-(Fe, Cr)2–3N) phases. The cross section of the nitrided steel was analyzed by scanning electron microscope. To understand the effect on corrosion resistance, potentiodynamic polarization along with the electrochemical impedance spectroscopy (EIS) was performed in 3.5% NaCl. The corrosion resistance of the nitrided steel was found to be much higher than the as-received steel. It was also found that the steel nitrided for shorter duration of 6 h has better corrosion resistance than that for 8 h. This enhancement of corrosion resistance may be attributed to the presence of nitrogen in solid solution, γ′-(Fe, Cr)4Nand ε-(Fe, Cr)2–3Nphases