Analysis of load-penetration depth data using Oliver-Pharr and Cheng-Cheng methods of SiAlON-ZrO2 ceramics

Depth sensing indentation tests were carried out to obtain load-penetration depth curves of SiAlON-ZrO2 ceramics under different peak loads ranging from 200 to 1800 mN. The values of indentation hardness (H-OP, H-CC) and reduced elastic modulus (E-OP, E-CC) were calculated by using Oliver-Pharr (OP) and Cheng-Cheng (CC) methods. The experimental results revealed that the indentation hardness and reduced elastic modulus exhibit peak-load dependence, i.e. indentation size effect. Both indentation hardness and reduced elastic modulus values were obtained by considering indenter tip roundness and machine compliance. These values obtained from the OP method are higher than from the CC method. On the other hand, h(f)/h(m) ratios were used to clarify the indentation deformation behaviour of the SiAlON-ZrO2 ceramic. The experimental h(f)/h(m) values were lower than the reported critical value (0.7) for all applied test loads, which is attributed to work-hardening behaviour of SiAlON-ZrO2 composites.