| 摘要 |
PROBLEM TO BE SOLVED: To provide a thermocouple protective tube which can prevent oxidation and corrosion caused by molten metal. SOLUTION: The outer surface of a protective tube 2 made of silicon nitride or a sialon system-based ceramic, of which the tip 6 is closed, is covered with a mixture or a compound of molybdenum Mo and Zirconium diboride ZrB2 as an undercoat layer 3, on which zirconia ZrO2 is coated as an outermost layer 5. A mixture or a compound of molybdenum Mo, zirconium diboride ZrB2 , and zirconia ZrO2 is arranged as an intermediate layer 4 between the undercoat layer 3 and the outermost layer 5. The intermediate layer 4 is configured so that the content of zirconia ZrO2 with respect to the mixture or the compound of molybdenum Mo and zirconium diboride ZrB2 increases stepwise from the undercoat layer 3 to the outermost layer 5.
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