Effect of molybdenum on hardness of low-temperature plasma carburized austenitic stainless steel

Martensitic Stainless Steels Low-temperature Nitriding: Dependence of Substrate Composition

“…Results clearly show that the hardening effect tends to be higher for the AISI 410NiMo steel, even for the treatment at 300°C, for which the layer thickness was about half than those obtained to the other studied steels. So, to finish the discussion on this point, lattice expansion effect due to the presence of Mo, as suggested by [15][16] , could also be responsible for the increase of the layer hardness. For technological purposes this aspect merits to be further studied, but it is out of the scope of the present work.…”

“…Comparing the bulk material microstructures it can be noticed that the AISI 410NiMo steel samples present relative coarser structure, which would reduce the role of high-diffusivity paths on the nitrided layer growth, in this case, to a level that it is not detectable with the applied measurement techniques. In addition, considering the well known effect of lattice expansion regarding the alloying element Mo in steel composition, according to 15,16 , a higher treatment kinetics should be expected for the AISI 410NiMo steel. Nevertheless, it seems that in our case, the effect of high-diffusivity paths overcomes the Mo effect, differently to the observed by 15,16 on the layer growth kinetics of austenitic stainless steels.…”

“…In addition, considering the well known effect of lattice expansion regarding the alloying element Mo in steel composition, according to 15,16 , a higher treatment kinetics should be expected for the AISI 410NiMo steel. Nevertheless, it seems that in our case, the effect of high-diffusivity paths overcomes the Mo effect, differently to the observed by 15,16 on the layer growth kinetics of austenitic stainless steels. Albeit the presence o Mo and Ni does not influence significantly the layer growth for the studied steels and treatment conditions, it is possible that the presence of large elements like molybdenum could improve the interstitial atoms content (in our case nitrogen) in solid solution, changing the nitrided layer characteristics and properties, as it will be presented in Figures 5 and 6.…”

“…On the other hand, studies for martensitic stainless steels have been less considered, and several opened questions remain to be answered. Among the several parameters to be chosen and controlled, it is well known that the substrate composition plays an important role on the low-temperature thermochemical treatment of austenitic stainless steels [15][16][17] . Those authors have shown that the presence of copper and molybdenum in solid solution allowed higher content of carbon/nitrogen in the layer of the supersaturated expanded austenite, at the treated surface, in the studied austenitic stainless steels.…”

Low Temperature Thermochemical Treatments of Austenitic Stainless Steel without Impairing its Corrosion Resistance

“…The most popular technology used to achieve the aforementioned low temperature thermochemical treatments of stainless steels is plasma technology, namely plasma nitriding (Rie & Broszeit, 1995;Stinville et al, 2010), plasma carburizing (Sun, 2005, Tsujikawa et al, 2007 and plasma hybrid treatments (Sun, 2008;Li et al, 2010). Due to the formation of a native oxide film stainless steel surface when exposed to air or residual oxygen before and during the treatment process, it is rather difficult to facilitate nitrogen and carbon mass transfer from the treatment media to the component surface.…”