Development of a Surface Modification Procedure for Enhanced Hardness and Wear of Mild Steel

This study developed an effective heat treatment procedure aimed at conferring enhanced hardness and wear characteristics on mild steel. The methodology entailed thermo-carburisation of mild steel using charcoal and graphite alternately at varied particle sizes (60 µm, 80 µm and 100 µm). Carburisation of the mild steel samples was carried out in a muffle furnace at a constant temperature of 1000 oC, soaked for 4 hrs and characterised for wear and hardness. Furthermore, the carburised samples’ surface microstructural feature was analysed using scanning electron microscope (SEM). In comparison with charcoal-carburised samples performances, the 60 µm graphite-carburised samples had the highest hardness: (293.7 HV), wear resistance: (1.01 × 103 cm-2) and lowest wear rate: (0.78 × 10-3 cm2). These values translate to improvement in hardness, wear rate and wear resistance by 55%, 63.5% and 32.1% respectively. Contribution to these outcomes is attributed to the high carbon thermo-diffusivity of graphite resulting in inducement of fine cementite crystals which dispersed homogeneously in ferrite matrix. It is concluded that graphite is a better carburiser for improved mild steel hardness and wear characteristics. Aside other relevant stakeholders, the quest for improved surface quality of low carbon steels stands to benefit immensely from the outcomes of this work