Vacuum brazing of Inconel 600 sleeve to 316L stainless steel sheath of mineral insulated cable

In mineral insulated (MI) triaxial cables for detectors, the 200 μm thick zirconiated copper conductors are sheathed with 200 μm thick 316L stainless steel (SS). The process conditions for high-temperature vacuum brazing of Inconel 600 sleeves to 316L SS cable sheath, with a radial gap of 125–150 μm between them, has been optimised using 40 μm thick nickel-base BNi2 brazing alloy. The brazed joints, which were subjected to thermal cycling between 473 and 923 K over 50 thermal cycles to simulate the high-temperature operating conditions, was found to have adequate tensile strength similar to those in the as-brazed condition. During tensile testing, failure occurs in the cable sheath in all cases. The leak tightness of the brazed joints, in as-brazed and thermal-cycled conditions, both before and after tensile testing is also found to be satisfactory.