Effect of carbon content on the mechanical behavior of MgO–C refractories characterized by Hertzian indentation

• Mechanical behaviors of MgO–C refractory materials have been investigated.
• The ball indentation tests were employed to evaluate the mechanical properties.
• The carbon content and indentation ball size strongly affected the mechanical behaviors.
• The ball indentation method was verified as an evaluation tool for MgO–C refractories.

The mechanical behavior of magnesia–carbon (MgO–C) refractory materials containing 4, 11, and 19 wt% carbon was investigated by Hertzian indentation tests. No microstructural changes were observed for the various carbon amounts. The slope during loading and the residual displacement after unloading were determined from indentation load–displacement curves. Indentation conditions were varied to study their influence on the mechanical behavior of the MgO–C. Repetitive contact fatigue tests were also conducted. The carbon content and indentation ball size ultimately affected the indentation mechanical behavior. The MgO–C containing 4 wt% carbon exhibited relatively hard and brittle behavior, while the MgO–C containing 19 wt% carbon exhibited a quasiplastic behavior, independent of ball radius indented on the MgO–C. Results indicated that carbon, in suitable amounts, provides the MgO–C with soft and ductile behavior in contact, wear, and impact environments.