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

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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.
2009-04-01