Abstract: A systematic investigation was made on the corrosion behavior of MCPT-4 ceramets in high-temperature molten salts. A criterion is thus developed for the preparation and application of such ceramets’ protection tubes to thermocouples. Ceramets of ternary system MCPT-4 or of quarternary system in which other component is added are proved extraordinarily beneficial to the resistance to BaCl2 molten salt with a continuous service life not less than 1400h. Their corrosion losses are mainly due to the electrochemical corrosion to metallic molybdenum at a corrosion rate increasing with Mo content. Therefore, the molybdenum content in ceramet should be decreased as possible to provide it with enough resistance to corrosion, subject to satisfaction of the resistance to thermal shock given to ceramet protection tube. After sintered in H2 atmosphere at 1800℃, a part of Cr2O3 in MCPT-4 ceramets will be reduced to metallic chromium and then forming solid solution together with molybdenum. The additive Cr2O3 in Mo-Al2O3 system will serve the function of bridge or tie to strengthen the combination of metallic phase with ceramic phase, thus improving the properties of ceramets.

Key words: Ceramet, Corrosion, Molten salt