No abstract

No abstract

both biomass generated fly ash and synthetic biomass ashes and has been monitored as a C. LIU function of reaction time for up to 1000 h. Detailed microstructral and compositional analy-J. A. LITTLE ses have been carried out to investigate the hot corrosion mechanism. Various micro-A. J. STURGEON structural defects and compositional inhomogeneities are found to play an important role in the initiation of hot corrosion. Deposition of molten reactants from the ashes creates the aggressive environment. Molten salts cause initial rapid hot corrosion via fluxing reactions between planar interlamellar porosity resulting in debonding of the surface lenticular splats followed by subsequent slow dissolution. Comparison between the performance of the coating in the fly ash and the synthetic ashes provides information for improved laboratory corrosion tests.

A reaction-formed NiAI intermetallic compound (IMC) powder has been deposited as a coating onto low carbon steel test coupons by the High Velocity Oxy-Fuel (HVOF) process using both gaseous and liquid fuels. The microstructure of this coating has been examined using scanning electron microscopy and x-ray diffraction and was found to depend on spraying conditions. Oxidation tests on the coating in air, between the temperatures of 800°C-1200°C, revealed that an a-alumina (Al2O3) scale formed on the coating's surface. At 1200°C, a nickel spinel (NiO/NiAl2O4) and haematite (Fe2O3) phases were observed. Diffusion studies were performed to calculate an activation energy for iron ion diffusion in NiAl.