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 NiCr BSiFe and WC-NiCrBSiFe alloys subjected to conditions which simulate a post -combustion gas atmosphere from a coal-fired boiler combustor. The study fi rst evaluates the effects of thermal exposure at high temperatures on the m icrostructure of the coatings and on the adherence between substrate (auste nitic 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 evalu ated. The effect of WC on the low-velocity corrosion-erosion behaviour prod uced by the impact of fly ashes in the gas stream at high temperatures (773 and 1073 K) was assessed under impact angles of 30 degrees and 90 degrees. Finally, the eroded surfaces were analysed using scanning electron microsc opy in order to characterize the ash embedment phenomena and the operating erosive micromechanisms. (C) 2001 Elsevier Science Ltd. All rights reserved .