Effect of molybdenum and copper on S-phase layer thickness of low-temperature carburized austenitic stainless steel

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

“…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.…”

Novel Low-temperature Solid-carburizing Using C60 Fullerene for Austenitic Stainless Steel SUS316L

“…Recently, new carburizing techniques, including the socalled low-temperature gas or plasma-carburizing techniques, have been developed which make it possible to avoid the Cr depletion problem for austenitic stainless steels. [1][2][3][4][5][6][7][8][9][10][11] The carburizing process is done at around 450-500°C which is in the temperature range below the nose of the time-temperature-transformation (TTT) diagram. 12) In the temperature range, interstitial atoms such as C and N can diffuse in the parent lattice but the diffusion of substitutional atoms such as Cr is impeded, thus suppressing the formation of Cr carbides.…”

“…The supersaturated C atoms that penetrate from the surface into the interstitial sites expand the parent lattice with keeping it in the fcc structure. The carburized and/or nitrided layer is called as the S-phase, [9][10][11] where not only hardness is extremely increased but also resistance against fatigue and corrosion is further improved. [13][14][15][16] In order for this low-temperature carburizing to be done successfully, however, surface activation treatment is unavoidable for the stainless steels since the Cr 2 O 3 passive film that forms on the surface of the stainless steels, and plays a key role in their good corrosion resistance, effectively inhibits the carburization.…”