Corrosion and oxidation behaviour of β-SiAlON ceramics via different processing route

Abstract

The corrosion resistance of β -SiAlON based advanced ceramic materials in molten aluminum, equimolar NaCl-KCl melt and also in the melted mixture of NaF and AlF3 (molar ratio 1 : 1.163) were investigated. Two kinds of β-SiAlONs were tested; β-SiAlON prepared from powder precursors produced by carbothermal reduction and nitridation (CRN) of pyrophyllite and β-SiAlON made from commercial powders (AlN, Al2O3 and Si3N4). Corrosion tests were realized at 760°C for 7, 36 and 72 h under nitrogen atmosphere by dip-finger test method. All types of β-SiAlONs have great corrosion resistance against molten aluminum and NaCl-KCl melt at these conditions. The results of corrosion test were different for the β-SiAlONs in molten fluorides. While the corroded zone was only about 100 μm deep after 72 h corrosion test in reference β-SiAlON prepared from synthetic powders (SiAlON-R), in sample prepared from CRN pyrophyllite (SiAlON-P) it was almost 230 μm thick. Additionally, the oxidation resistance of β -SiAlONs was tested. The results showed that both SiAlON-P and reference SiAlON-R have comparable good oxidation resistance. © 2009 The Ceramic Society of Japan.