Abstract

A novel process comprising of aluminothermic co-reduction of mixed oxides followed by arc and electron beam melt refining was developed for preparation of Nb-1Zr-0.1C alloy. The parameters of the process were optimized by considering the thermodynamic (heat) and mass balance phenomenon. The ingots of the homogenized alloy produced after electron beam melt consolidation were further extruded into tubes. The alloy was vacuum annealed at 1350-1800°C to study the stability of Nb2C and Nb(Zr)C precipitates in the microstructure. The microstructures of the alloy at different stages of processing were characterized using SEM, EDS, EBSD, and HRTEM. Compression creep tests conducted at 900 and 1000°C revealed a stress exponent value of 2 and activation energy of 508 kJ/mol. NbSi2 based coatings were developed on the Nb-1Zr-0.1C alloy tubes using pack siliconizing process. The coated alloy was tested for oxidation at 1250°C, and corrosion in liquid lead-bismuth eutectic (LBE) alloy at 875°C for prolonged duration. The silicide coated alloy showed superior oxidation and LBE corrosion resistance at high temperatures. The alloy was found to be a promising material for coolant channels of high temperature reactors.

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