Plasma Nitriding of 90CrMoV8 Tool Steel for the Enhancement of Hardness and Corrosion Resistance
TypeArticles dans des revues avec comité de lecture
The aim of the study is to apply a plasma nitriding process to the 90CrMoV8 steel commonly employed in wood machining, and to determine its efficiency to improve both mechanical and electrochemical properties of the surface. Treatments were performed at a constant N2:H2 gas mixture and by varying the temperature and process duration. The structural and morphological properties of nitrided layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS microanalyses. Surface hardening and hardness profiles were evaluated by micro hardness measurements. To simulate the woodmachining conditions, electrochemical tests were carried out with an oak wood electrolyte with the purpose of understanding the effects of the nitriding treatment on the corrosion resistance of the tool in operation. X-ray diffraction analyses revealed the presence of both γ′ (Fe4N) and ε (Fe2–3N) nitrides with a predominance of the ε phase. Moreover, α-Fe (110), γ′ and ε diffraction peaks were shifted to lower angles suggesting the development of compressive stresses in the post nitrided steel. As a result, it was shown that nitriding allowed a significant hardening of steel with hardness values higher than 1200 HV. The diffusion layers were always composed of an outer compound layer and a hardened bulk layer which thickness was half of the total diffusion layer one.No white layer was observed. Similarly, no traces of chromium nitrides were detected. The temperature seemed to be a parameter more influent than the process duration on the morphological properties of the nitrided layer, while it had no real influence on their crystallinity. Finally, the optimal nitriding conditions to obtain a thick and hard diffusion layer are 500 °C for 10 h. On the other hand, to verify the effect of these parameters on the corrosion resistance, potentiodynamic polarization tests were carried out in an original “wood juice” electrolyte. After corrosion, surface was then observed at the SEM scale. Electrochemical study indicated that the untreated steel behaved as a passive material. Although the very noble character of steel was somewhat mitigated and the corrosion propensity increased for nitrided steels, the passive-like nature of themodified surfacewas preserved. For the same optimized parameters as those deduced from the mechanical characterization (500 °C, 10 h), surface presented, in addition to a huge surface hardening, a high corrosion resistance.
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RAM MOHAN RAO, K.; NOUVEAU, Corinne; TRINADH, Kalimi (Elsevier BV, 2019)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 ...
RAM MOHAN RAO, K.; NOUVEAU, Corinne; KHANNA, A.S.; ANEJA, Karanveer S.; TRINADH, Kalimi (Elsevier BV, 2020)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 ...
Electrochemical study on the corrosion resistance of surface modified Cr-Mo-V steel by elevated temperature plasma nitriding TRINADH, Kalimi; NOUVEAU, Corinne; KHANNA, Anand Sawroop; ANEJA, Karanveer S; RAO, K Ram Mohan (IOP Publishing, 2019)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 ...
RAO, K. Ram Mohan; NOUVEAU, Corinne; TRINADH, Kalimi (Springer, 2020)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 ...
RAO, K. Ram Mohan; TRINADH, Kalimi; NOUVEAU, Corinne (Elsevier BV, 2019)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. ...