A comparative study of high-temperature erosion wear of plasma-sprayed NiCrBSiFe and WC–NiCrBSiFe coatings under simulated coal-fired boiler conditions

A comparative study was carried out of the behaviour of plasma sprayed NiCrBSiFe and WC–NiCrBSiFe alloys subjected to conditions which simulate a post-combustion gas atmosphere from a coal-fired boiler combustor. The study first evaluates the effects of thermal exposure at high temperatures on the microstructure of the coatings and on the adherence between substrate (austenitic stainless steel) and coatings. The oxidation rates of these coatings in atmospheres with 3–3.5% of free oxygen at 773 and 1073 K were then evaluated. The effect of WC on the low-velocity corrosion–erosion behaviour produced by the impact of fly ashes in the gas stream at high temperatures (773 and 1073 K) was assessed under impact angles of 30° and 90°. Finally, the eroded surfaces were analysed using scanning electron microscopy in order to characterize the ash embedment phenomena and the operating erosive micromechanisms.