Effect of vanadic corrosion on creep-rupture properties of superni-600 at 650-750°c

The effect of vanadic corrosion on creep-rupture properties of a nickel base superalloy Superni-600, at 650-750°C, has been investigated. Sodium metavanadate and sodium metavanadate plus 15 wt% sodium sulphate were used as the corrodent salts. Weight change studies have also been made to understand the mechanism of corrosion. Both sodium metavanadate and the sodium metavanadate/sodium sulphate mixture are found to be aggressive and to reduce the creep-rupture life. The degradation of creep-rupture properties and possible hot corrosion reactions are discussed. Cracking and fluxing of the protective scales, together with easier crack nucléation and growth at grain boundaries in the presence of a liquid deposit accounts for the enhanced creep rates and reduced rupture lives. © 1992 Butterworth-Heinemann Ltd.