Sand Erosion of Alumina Ceramics at Elevated Temperatures.

Abstract

The sand erosion of alumina ceramics by the impingement of alumina abrasives with an average diameter of 363μm at a velocity of 65m/s has been investigated for temperatures ranging between room temperature and 919°C. Erosion rate, defined as the volume of the alumina ceramics removed by the unit mass of the impingement particles, increased both with an increase in temperature, and with the impact angle from 30 to 90°. Scanning electron microscopy (SEM) studies showed that intergranular microfracture was present on all of the eroded surfaces. Plastic cutting features were also observed in the specimens tested at the lower impact angles. At elevated temperatures, flow-like layers were observed together with features showing brittle fracture. From estimation of the ratios of brittle and ductile fracture, the amount of brittle fracture increased with an increase in temperature, while ductile damage was independent of temperature. A relationship between erosion rate and the mechanical properties of the alumina ceramics has been determined. It suggests that the temperature dependence of the erosion rate is related to both the hardness and the fracture toughness up to temperatures around 800°C. Above 800°C, and especially at the highest temperatures studied (919°C), the significant increase in the erosion rate may be due to grain boundary softening.