Hertzian Indentation Damage Behavior of Highly Porous Silicon Nitrides

摘要

Highly porous Si_3N_4 ceramics in service are usually subjected to continuous impact of solid particles which may give rise to localized damage and consequently to strength degradation. Hertzian indentation and three-point bending tests were conducted to investigate the contact damage behavior of highly porous Si_3N_4 ceramics in this paper. The Hertzian indentation damage morphologies were examined by using a bonded-interface technique. As a result of intragranular microfracture under Hertzian indentation, a distributed subsurface damage region is developed beneath the indenter. It was shown that, with increasing indentation load, the damage region extends progressively and a quasi-plastic stress-strain response exhibits. Failure sources were observed to be Hertzian indentation sites in three-point bending tests, leading to a gradual strength degradation.