Corrosion of Hot Pressed Si3N4-TiN Composite in sulphuric acid aqueous solution

The corrosion behaviour of an electroconductive Si3N4 -35 vol % TiN composite, hot pressed with the addition of Al2O3 and Y2O3 as sintering aids, was studied in 1.8 M sulphuric acid aqueous solution at R.T., 40°C and 70°C up to 400 hours. The corrosion, that follows linear kinetics, at R.T. and at 40°C involves only the progressive chemical dissolution of grain boundary phases, in the system Al-Y-Si-Ti-O-N. The chemical attack of TiN occurs at 70°C, while Si3N4 is not affected by the selected corrosive environment. The effect of the corrosion on flexural strength, fracture toughness and electrical resistivity were investigated after a permanence of 400 h at each temperature in the corrosive solution.