Abstract
Thermally sprayed coatings are mechanically bonded to the substrate and present porosities and a lamellar microstructure that make them less attractive in applications requiring high coating toughness and impermeability to gas and liquids, these properties been obtained with more technically advanced overlaying processes. This paper presents the research work carried out to increase the erosion resistance of arc-sprayed coatings containing hard Fe2B crystals dispersed in mild and alloyed steel-based matrices. These arc-sprayed coatings were a) heat-treated in furnace up to 1000°C and b) fused with an oxy-acetylene torch. The sprayed specimens were tested in a particle erosion device at the impact angles of 25° and 90°. The evolution of microstructure was done by SEM and wear damage by Time- Domain Optical Coherence Tomography. It was shown that both the heat treatment and fusing processes considerably enhanced the erosion resistance of coatings particularly at the impact angle of 90°. This increase in erosion resistance is attributed to the disappearance of stringers between sprayed lamellae. Liquid phase sintering is the mechanism responsible for the homogenization of arc-sprayed coatings containing Fe2B. Grain growth observed in arc-sprayed coatings heat-treated up to 1000°C or fused with an oxyacetylene torch does not have a detrimental effect on erosion resistance.
