Influence of the carburization time on the structural and mechanical properties of XC20 steel

This study focuses on the effect of carburization time on the structural and mechanical properties of low carbon XC20 mild steel (C. Wt.% <0.25). The XC20 steel was carburized with activated carbon with a carbon potential Cp₁ = 1.1%, at 910 °C at different carburization times of 2, 4 and 6 h. The results obtained show that XC20 steel (non-carburized) has a ferrite-pearlitic structure with a hardness and a Young's modulus of the order of (150 HV, 26 KN/mm²). After carburization, the structure of the carburized layer is transformed in martensite (Fe γ) in which cementite (Fe₃C) is imbricated. The depth of the carburized layer and the amount of carbon on the surface gradually increase with increasing carburization time. In addition, the carburized XC20 steel becomes hard and brittle where the hardness and Young's modulus have been increased for a high holding time until reaching maximum values(845 HV, 48 KN mm⁻²) after 6 h of carburization . However, the toughness of XC20 steel has been reduced from 163 to 40 J cm⁻². (paper)