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Materials Science and Engineering: A. Volume 597, 12 March 2014, Pages 331–341.
Saurav Goel, Suhas S. Joshi, Gasser Abdelal, Anupam Agrawal.
School of Mechanical and Aerospace Engineering, Queen’s University, Belfast BT95AH, UK &
Department of Mechanical Engineering, Indian Institute of Technology, Bombay 400076, India &
Department of Business Administration, University of Illinois at Urbana Champaign, IL 61820, USA.
Abstract
Study of nanomechanical response of iron carbides is important because presence of iron carbides greatly influences the performance and longevity of steel components. This work contributes to the literature by exploring nanoindentation of Fe3C and tetrahedral-Fe4C using molecular dynamics simulation. The chemical interactions of iron and carbon were described through an analytical bond order inter-atomic potential (ABOP) energy function. The indentations were performed at an indentation speed of 50 m/s and a repeat trial was performed at 5 m/s. Load–displacement (P–h) curve for both these carbides showed residual indentation depth and maximum indentation depth (hf/hmax) ratio to be higher than 0.7 i.e. a circumstance where Oliver and Pharr method was not appropriate to be applied to evaluate the material properties. Alternate evaluation revealed Fe3C to be much harder than Fe4C. Gibbs free energy of formation and radial distribution function, coupled with state of the average local temperature and von Mises stresses indicate the formation of a new phase of iron-carbide. Formation of this newer phase was found to be due to deviatoric strain rather than the high temperature induced in the substrate during nanoindentation.
