Interaction at high temperature of Popocatépetl volcanic ash deposited on yttria-stabilized zirconia sintered coupons

Abstract

This work aims to study the interaction of sintered yttria-stabilized zirconia (7YSZ) ceramic under a volcanic ash mix at an engine representative temperature of 1350 °C. In this work, two different locations – distance from Mexico Popocatépetl Volcano were chosen to collect the ashes, and to perform their melting process with variable chemical composition. Afterward, each ash was deposited on the surface of 7YSZ ceramic coupons, then they were exposed at heating and cooling cycles at designed temperature equal to 1350 °C. After 8 cycles of thermal treatment testing of 8 h, the morphology and microstructure analysis of the 7YSZ coupons was carried out using microscopy and X-ray diffraction analysis techniques. The results showed that a molten ash layer, with smooth morphology of size of 60 μm of thick, was formed on the ceramic surface. Based on the observed degradation, the general status of the coupons after 8 cycles of thermal test, presented failure by growth of large cracks which were associated to the infiltration of melted ash through the thickness of ceramic coupon. This melted ash infiltrated trough the fine grain microstructure, promoted the development of a compose rich in silica, which is brittle and therefore promoted cracks initiation with subsequent propagation in the substrate.