On the effect of sintering temperature on the fracture energy of an Alumina-Mullite-Zirconia castable at 600 °C

Abstract

Refractory castables are utilized in hazardous environments and thus their reliability should be accurately evaluated to avoid incidents. This work aims to measure the fracture energy of a high-alumina refractory with mullite-zirconia aggregates at 600°C. Wedge Splitting Tests were performed on 5 samples with different sintering temperatures. Images were acquired and analyzed via Digital Image Correlation (DIC). Notch Opening Displacements were used to evaluate the fracture energy at room and high tempartures. For the studied material, a 50°C increase in the sintering temperature increased about 30% the fracture energy of the material, which is also higher at 600°C when compared to room temperature measurements.

Fracture energy evaluation of refractories in wedge splitting tests from notch opening displacements

“…It is worth noting that the 1.57 factor depends on the NOD and CMOD gauge positioning. From a preliminary study [41], the proportionality coefficient was higher (i.e., 1.62) since the NOD gauge was not positioned at the same location as herein. Conversely, this factor is independent of the Young's modulus since any displacement is proportional to .…”

“…The following analysis deals with a WST that belongs to the category of experiments for which the NOD history could be measured but not the CMOD (Figure 1 ). The castable was fired at 1450°C and subsequently tested at room temperature [41]. Grooves were implemented on the front and back faces (Figure 1(b)) to prescribe the crack path to be straight with a slightly bigger thickness (i.e., 75 mm) in comparison to Figure 2(b) and a total thickness reduction of 20 mm instead of 7 mm.…”

“…The curves reported in Figure 18 were analyzed as previously to estimate the propagation energy by assuming that the fractured surface coincided with the central plane [41]. The results are shown in Table 5.…”

“…Another advantage of such measurement technique is that it can also be deployed when performing high temperature WSTs [12,40]. In one such application, an additional issue arose because standard furnaces may not allow front and/or back sample surfaces to be fully monitored by digital cameras [41]. Figure 1(b) illustrates that situation for which it was decided to focus image acquisitions along the propagation path.…”

“…The dark areas in the corners of Figure 1(b) are related to obscuration of the illumination setup of the furnace. The test related to Figure 1(b) was performed at room temperature (but inside the furnace) to prepare the following high-temperature tests [41] that are not discussed herein. The question to be addressed in the following analyses is how the NOD can be extrapolated to evaluate CMOD even though it may not be measurable in some instances.…”