Dynamic Hardness Trend of Tribological Steels Used for Advanced Power Transmission Assembly

Prantik Mukhopadhyay; Rajnish Goyal; Manish Roy

Abstract

Gravity drop technique was used for measuring dynamic hardness trend of M50, 52100 and 4340 tribological steels. Work hardened state increased dynamic hardness, while shear bands and dynamic recovery of dislocations induced dynamic softening. Descending order of work hardening for the investigated steels is M50-52100-4340. The threshold strain to begin the softening gradually increases in the order M50-52100-4340 steels. Descending order of work softening beyond threshold strain for the investigated steels is M50-4340-52100. Softening is defined by heat capacity and stacking fault energy, which are governed by solute elements in solid solutions. Heat capacity has been defined by constitutive enthalpy and entropy constituents. Energy equilibrium of stacking fault energy, heat capacity and surface energy of elements has been formulated for variable processing temperature. Solutes of less atomic size with high electro-negativity have been found to reduce stacking fault energy. Low stacking fault energy and heat capacity inevitably induce greater flexible resilience and toughness, predominantly governed by matrix phases than precipitates and concerned material properties are required for advanced material design for aerospace power transmission assemblies.