Research On The Surface Strengthening Technology Of High-temperature Molten Salt Corrosion Resistance Of Tantalum

In this paper, the high-temperature molten salt environment was simulated and theoptical microscopy, X-ray diffraction, scanning electron microscopy were used to researchon the mechanism of high-temperature molten salt corrosion of Tantalum. Diamondcoating and laser remelting surface strengthening technology was processed on the surfaceof Tantalum to improve the high-temperature molten salt corrosion resistance of Tantalum,the result was analyzed to find the mechanism of strengthening. The following resultshave been gotten:1. The surface phase produced by the high-temperature chloride salt corrosion weremostly the oxides of tantalum. The mechanism of high-temperature molten salt corrosionis the lost(evaporation or gasification) of the chlorid of tantalum and the"formation-dropping-formation" cyclic process. With the increasing of temperature, thespeed of corrosion was increased as well.2. In850℃molten salt, at the beginning, the mass of tantalum was increasedbecause of the formation of oxide coating of tantalum on the surface. Then the weight lossof tantalum has a positive correlation with time. However, in950℃molten salt, there’s nostratiform oxide coating formed on the surface of tantalum and the dropping of coatingwould occur, the weight loss of tantalum has a positive correlation with time as well.3. During the corrosion of molten salt, the annealing twin crystal was obtained on theboundary with time. Because of the increase of crystal boundaries of twin crystal and itsdefects, a rapid corrosion channel would formed among twin crystals which could increasethe speed of corrosion.4. The diamond coating on the surface of tantalum can improve the molten saltcorrosion resistance at the beginning because of the advanced performance of itself andthe more stable carbide of tantalum obtained in the process of plating diamond film. However, because of the thinness and the dropping of this film, the protecting effect wasdecreased with time.5. Laser remelting surface strengthening process could improve the molten saltcorrosion resistance of tantalum because of the elimination of the microdefect and theformation of a nanocrystal layer on the surface of tantalum. It improved the surfacedensity by increasing the resistance of initiation and propagation of crack and refined theoxides to improve the adhesion between the coating and substrate. In addition, theformation of oxides of tantalum in the crack could cause the self-healing effect of somecracks which could prevent crack deepening to improve the corrosion of tantalum.6. After contrast, the remelting layer has the best high-temperature molten saltcorrosion resistance, the resistance of high-temperature molten salt corrosion was1.1times than that of substrate. The resistance of high-temperature molten salt corrosion ofdiamond film was0.8times than that of substrate.