High-temperature corrosion resistance of NiAl(Cr)-Al2O3 coating in N2+9%O2+0.2% HCl+0.08%SO2 atmosphere

Purpose: The aim of this study was to determine the resistance of nickel and aluminium intermetallic phase-based coatings, modified with chromium and aluminum oxides, and to determine the hypothetical mechanism of these materials’ corrosion. Design/methodology/approach: The selected results of high temperature corrosion resistance of HVOF sprayed coatings with NiAl intermetallic phases are presented. The aggressive corrosion gas included: N2+9%O2+0.2% HCl+0.08%SO2. The temperature of cyclic corrosion test was 927 K and the exposure time was 500 h. The macro and microstructure of coatings after and before corrosion test were analyzed by optics and scanning microscopy. The thermodynamically diagrams and phase diagrams of corrosion products after the test are presented. The phase composition of corrosion products was determined by X-ray analysys. Findings: The proposed mechanism and growth of corrosion products on the NiAl(Cr)-Al2O3coatings are shown. The carried out tests allow the characterisation of the properties of coatings with NiAl phase, and supplement the state of knowledge in the scope of their high temperature corrosion resistance. Practical implications: The new elaborated coating can be applied in elevated temperature and aggressive environments for protection of water walls boilers or waste combustors. Originality/value: The elaboration of proposed mechanism of growth corrosion products on the NiAl(Cr)-Al2O3coating and the presentation of reaction during the corrosion process and degradation of coating.