An Empirical Model for Carbon Diffusion in Austenite Incorporating Alloying Element Effects

Abstract

The diffusion of carbon in austenite is important to the design and implementation of many steel heattreating processes. The present study proposes a simple and computationally efficient equation for the diffusion of carbon in austenite for iron-carbon alloys, as well as for steels alloyed with a variety of elements. The proposed empirical model provides a pragmatic engineering approach to this important diffusion process. The model is shown to better match the carbon diffusion profiles of several carburized steel alloys, as compared to other equations that have been reported in the literature. These other equations were primarily obtained from experiments on iron-carbon alloys, and it is not surprising that they are less accurate when compared to the proposed equation that takes the full range of alloy compositions into account.KEY WORDS: carbon diffusion; alloy effects on diffusion in austenite; empirical model; experimental data; steels.

Temperature effect on deformation mechanisms and mechanical properties of a high manganese C+N alloyed austenitic stainless steel

“…10, showing three SH-stages. The strain-hardening (SH) behavior of the Fe-14Cr-16Mn-0.3C-0.3N alloy is characterized by a single intermediate hardening stage associated with high SH, similar to Al-containing TWIP [68,91,92] and austenitic stainless steels [43,75,93]. The initial stage (I) hardening is characterized by a sharp drop of the SHR.…”

“…In Fe-Cr-Mn-C-N steels, Cr-N SRO is assumed to be the preferred ordered structure [88] rather than Mn-C SRO [89,90]. Furthermore, Cr additions, which significantly reduce the diffusivity of C in austenite [91], may also increase the activation energy of reorientation of the point defect complexes, similar to the effect of Al additions [81]. Therefore, the type of SRO and the activation energy for reorientation of Cr-C and Cr-N point defects, rather than the SFE may be the reason for the homogenous flow behavior in the present steel.…”

Metallurgical Characterization and Diffusion Studies of Successively Buttered Deposit of Ni–Fe Alloy and Inconel on SA508 Ferritic Steel

“…Bose 35) has reported on the diffusion of carbon in Nickel. Using the diffusion coefficient (Do) and activation energy (Q), 35,36) the diffusivity of carbon in Nickel at 330°C and 450°C was determined using the temperature dependence Eq. (6) Where the D is diffusivity of carbon, Do is the diffusion coefficient in m 2 /s, Q represents the activation energy in kJ/mol, R is the gas constant in J/Kmol, and T is the temperature in Kelvin.…”

Molybdenum alloying in high-performance flat-rolled steel grades

“…It has the tendency of segregating to grain boundaries or binding with other lattice defects such as vacancies or dislocations [7][8][9]. It also lowers the activity of carbon [10,11], thus slowing down processes that rely on carbon diffusion. Along the processing chain of flat rolled products molybdenum alloying: enhances the solubility of the micro-alloys Nb and Ti during slab reheating [10], supports recrystallization delay during austenite conditioning [12], retards precipitation of micro-alloys during austenite conditioning [13], delays phase transformation from fcc to bcc [14], promotes nonpolygonal ferrite formation with high dislocation density [15], controls micro-alloy precipitation in bcc to ultra-fine size and dense particle distribution [16].…”