A New Perspective on Alloy Surface Engineering by Infusing High Concentrations of Interstitial Atoms

Wednesday, September 15, 2021: 2:20 PM
227 (America's Center)
Prof. Frank Ernst , CASE WESTERN RESERVE UNIVERSITY, CLEVELAND, OH
Dr. Zhe Ren , CASE WESTERN RESERVE UNIVERSITY, CLEVELAND, OH
Alloy surface engineering by infusing high concentrations of interstitial atoms is an established technology, e.g. implemented as low-temperature carburization of austenitic stainless steel. This technology enables outstanding improvements in surface hardness, wear-, fatigue-, and corrosion resistance by generating a subsurface zone in which the fraction of interstitial atoms can approach 0.15, exceeding equilibrium typical solubility limits by several orders of magnitude. Hitherto, this condition and the resulting properties have been understood in terms of a solid solution of interstitial atoms (carbon). Howewer, various properties and their dependence on the level of interstitial atoms do not agree with predictions of solid solution theory. Rather, recent experimental observations related to processing and properties suggest the formation of a disordered compound with a variable fraction of the infused atoms. This model enables a deeper physical understanding, increasing the potential for intelligent alloy surface engineering.