Indentation Load Effect on Young's Modulus and Hardness of Porous Sialon Ceramic by Depth Sensing Indentation Tests

Depth sensing indentation (DSI) tests at the range of 200--1800mN are
performed on porous sialon ceramic to determine the indentation load on
Young's modulus and hardness values. The Young modulus and hardness
(Dynamic and Martens) values are deduced by analysing the unloading
segments of the DSI test load-displacement curves using the Oliver--Pharr method. It is found that Young's modulus E_r, the dynamic hardness H_D and the Martens hardness H_M exhibit significant indentation load dependences. The values of Young's modulus and hardness decrease with the increasing indentation load, as a result of indentation load effect. The experimental h_f/h_m ratios lower than the critical value 0.7, with h_m being the maximum penetration depth during loading and h_f the final unloading depth, indicate that our sample shows the work hardening behaviour.