Performance of cold sprayed Ni-20Cr and Ni-50Cr coatings on SA 516 steel in actual industrial environment of a coal fired boiler

摘要

Power plants are one of the major industries suffering from severe erosion-corrosion (E-C) problems resulting in substantial losses. One way of tackling this problem is by the use of thermal spray coatings. In the current investigation a new emerging technique i.e. cold spray coating process was used to deposit Ni-20Cr and Ni-50Cr powder on SA 516 (grade 70) boiler steel. The bare as well as the coated steels were subjected to cyclic experimental studies, in the superheater zone of a coal fired boiler. Weight change, thickness loss, XRD, FE-SEM/EDS and X-ray mapping techniques were used to analyse the eroded-corroded specimens. The uncoated steel showed weight gain after exposure in the actual boiler environment, whereas, for the coated steels there was initial weight loss followed by negligible weight change. Based upon thickness loss data the cold-sprayed Ni-50Cr coating was found to provide better E-C resistance than the Ni-20Cr coating.