Effect of gaseous environment on the corrosion of β-sialon materials

Abstract

This paper reports the effects of different gaseous environments on the corrosion behaviour of β-sialon materials. Six β-sialon materials with z-values of 0.2, 0.5, 1.0, 1.5, 2.0 and 3.0 were prepared by pressureless sintering. Corrosion results obtained at 1350 °C in environments comprising (i) Laboratory air; (ii) Argon — 20% oxygen — 2% chlorine; (iii) hydrogen — 10% hydrogen sulphide — 2% water vapour and (iv) nitrogen — 15% carbon dioxide — 4% oxygen — 0.2% sulphur dioxide showed that for each of the four environments the z = 3.0 material exhibited the best corrosion resistance. The mechanism of corrosion at 1350 °C in each of the four environments involves the formation of large volumes of low viscosity liquid phases. These large volumes of liquid enable the solution of β-sialon grains to occur and it is this process which is responsible for corrosion.