Load-dependent indentation behavior of β-SiAlON and α-silicon carbide

A comparative study was carried out on the load-dependent indentation behavior with respect to hardness and induced cracks of β-SiAlON and α-silicon carbide ceramics. It is observed that silicon carbide (SiC) exhibits lower transition load, early cracking and severely crushed indentation sites, whereas β-SiAlON shows higher transition load and damage-free indentation zone even at the maximum applied load (294.19 N). Crack density is higher for α-SiC with comparison to β-SiAlON at each load. SiC exhibits both main and secondary radial types of cracking from low indentation load (0.98 N). Cracks are often associated with branching at higher load (> 9.80 N) for α-SiC. β-SiAlON exhibits cracks which are mainly radial types initiated at 4.90 N load. These opposing behaviors of β-SiAlON and α-SiC are attributed to their difference in hardness, toughness, and brittleness index. Higher brittleness of α-SiC results in early and severe cracking around its indentations. β-SiAlON shows less cracking due to its lower brittleness and higher toughness. The increased size of indentation-induced cracks of α-SiC is higher than that of β-SiAlON due to the rapid crack propagation in α-SiC with transgranular fracture behavior.