Hertzian Indentation Damage Behavior of Highly Porous Silicon Nitrides

Abstract

Highly porous Si3N4 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 Si3N4 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.