Analysis on high-temperature corrosion characteristic of 0Cr18Ni9NbCu3BN steel

Abstract

The high-temperature corrosion characteristic of 0Cr18Ni9NbCu3BN steel was analysed in this paper. The samples were selected from a super-heater with service time of 34 696 h in an ultrasupercritical boiler in China. Scanning electron microscopy, energy spectrum analysis and energy dispersive X-ray spectroscopy were adopted to analyse the element constitute, morphology and phase structure of the corrosion scale. The results indicated that corrosion scale can be divided into three layers, and the middle layer of corrosion scale is enriched with Cr. The Cr-rich layer could not set an efficient barrier to prevent sulphur from penetrating to the matrix. It actually can prevent O from penetrating to metal base effectively. The main corrosion forms are high-temperature oxidation and sulphidation, while the sulphidation rate was greater than the oxidation rate. The sulphidation is the major type of corrosion attack. Oxidation and sulphidation interactively cause the corrosion progress consistently.