Corrosion of hot pressed Si 3N 4–TiN composite in sulphuric acid aqueous solution

Abstract

The corrosion behaviour of an electroconductive Si 3N 4–35 vol% TiN composite, hot pressed with the addition of Al 2O 3 and Y 2O 3 as sintering aids, was studied in 1.8 M sulphuric acid aqueous solution at RT, 40 and 70 °C up to 400 h. The corrosion follows linear kinetics at RT and at 40 °C, involving only the progressive chemical dissolution of grain boundary phases, in the system Al–Y–Si–Ti–O–N. Chemical attack of TiN occurs at 70 °C, while Si 3N 4 is not affected by the selected corrosive environment. The effect of the corrosion on flexural strength, fracture toughness and electrical resistivity were investigated. Very high strength levels are maintained after corrosion for 400 h at room temperature, while the strength decreases of about 10% and 16% after the treatment at 40 and 70 °C, respectively. The electrical resistivity rises after corrosion at 40 and 70 °C, in line with the progressive chemical dissolution of the conductive TiN particles.