In this study, several thermal spray coatings and reference materials were evaluated for potential use in biomass co-fired boilers. The coatings were applied to T92, A263, and X10Cr13 substrates by HVOF and wire-arc spraying using powder (IN625, FeCr, NiCr) and wire (NiCrTi) feedstocks. Coating samples were examined then tested for 5900 h in the superheater area of a fluidized bed boiler burning a mixture of wood, peat, and coal. The corrosion behavior of the coating and reference materials is reported in the paper and the underlying corrosion mechanisms are discussed.

This work assesses the effects of defects in thermally sprayed chromia via multiscale modeling and imaging techniques. Defect distributions in coating samples are identified by way of image processing and synthetic 3D microstructures are generated from extracted statistical information. The properties of the microstructures are determined by subjecting them to simulated tensile testing, and the significance of different types of defects is evaluated through defect-containing coating models. The approach is able to handle complex defect morphologies, including pore, crack, and splat boundary clusters, making it a versatile tool for assessing the influence of defects on component performance.

A multiscale model is being built in order to better understand and predict high-temperature corrosion and erosion properties of thermal spray coatings and materials in general. The approach uses molecular dynamics to predict diffusion kinetics, constrained free energy to determine reactions, and FEA to simulate structure. To obtain oxidation behavior data for validation, surface polished bulk materials and thermal spray coatings were exposed to various temperatures and exposure times. Oxidation depth and diffusion were assessed by optical emission spectroscopy and cross-sectional SEM examination and surface oxidation in grain and lamellae boundaries was characterized by 3D profilometry and SEM-EDS. Rough validation of the model was achieved using indentation test data, and a more complete validation will be done when high-temperature erosion test results are available.