Hydrothermal Corrosion of Pure, Hot Isostatically Pressed Silicon Nitride

Abstract

The aqueous corrosion behavior of hot isostatically pressed Si 3 N 4 (HIPed‐Si 3 N 4 ) without additives was studied under hydrothermal conditions at 300°C and 8.6 MPa (86 atm). The accelerated weight loss in the HIPed‐Si 3 N 4 was attributed to uniform thinning of the specimen accompanied by dislodgement of Si 3 N 4 grains from the substrate due to preferential attack at grain boundaries. Enhanced attack at grain boundaries was due to the presence of amorphous SiO 2 from impurities in the starting powder.