Wear Behavior of Iron Based Alloys with Different Entropy Extent Estimated by Miedema's Model

In most situations, predicting wear requires a variety of microstructural characterizations and experiments with contact surfaces. Based on physical principles, mathematical models might be of great assistance in understanding and thereby predicting this event. Considering the significance of heat generation in war, it appears that the parameters of thermodynamics are appropriate measurements for wear modelling. Entropy is among these parameters of thermodynamics. The Miedema model is a good method to predict the Gibbs free energy and entropy of solid solutions of binary and ternary systems. In this study, the wear behaviour of iron-based alloys according to their estimating values of Gibbs free energies and entropy was studied under lubricated conditions. The wear test was performed in accordance with ASTM-G99, utilizing the vertical universal friction testing machine MMW-1A and the pin-on-disk test methodology. Results show that the lowest negative value of Gibbs free energy was noted in the Fe-Al-Sn ternary system (-14.37 KJ/mol), while the highest negative value was found in the Fe-Al-V (-25.16 KJ/mol) binary system. It was also concluded that the wear rate decreased when the entropy estimate increased. The higher value of the wear rate was (6.935 mm³\N.m x10⁷) for Fe-Al binary alloy with an entropy value (1.717 J\k Mole). The lowest value of wear rate was (3.581 mm³\N.m *10⁷) for Fe-Al-Sn ternary alloy with an entropy of (2.71 J\k Mole). This is due to the micro-distortion that was mechanically indicated with the ternary alloys Fe-Al with V, Mn, Ga.B, and Sn additives that affected the wear mechanism and caused high values of wear.

Keywords:
Friction; lubricant; enthalpy; Gibbs free energy; severe lattice distortion