Some aspects of the hot corrosion of nickel-based superalloys

The work is concerned with the investigation of the hot corrosion of a typical nickel-based superalloy Nimonic 105. The literature published up to the start of the present work has been reviewed to highlight areas in which research on this particular alloy should be focussed. To obtain hot corrosion under the carefully controlled conditions so essential for mechanistic diagnosis samples of Nimonic 105 have been exposed to pure Na2so4, Na2so4 with NaCl additions and pure NaCl at 1173K in flowing oxygen using a controlled potentiometric partial immersion crucible technique. After exposure the specimens were fully examined using metallography, electron probe microanalysis, scanning electronmicroscopy, X-ray diffraction and X-ray spectrometry to establish the morphological and scaling characteristics of corrosion. In addition a number of diagnostic experiments were devised to elucidate various points which emerged during the course of the work. [Continues.]