Thermal Spray Coated Alloys: Erosion and Corrosion Behavior

Erosion-corrosion of materials at elevated temperatures is a major problem in thermal power plant boilers due to severe operating conditions. The steels, which are commonly used in the manufacturing of conventional boilers experience accelerated erosion corrosion in high temperature boiler conditions. Although Chromium is expected to impart corrosion resistance to high temperature alloys but is not sufficient enough to form protective external scale. Currently, the superalloys are used to increase the service life of the boilers especially in the super-heater zones of the new generation ultra-supercritical boilers. These materials being developed with high strength at elevated temperatures are highly alloyed and thus very expensive and also prone to degradation to certain environments. So in search of cost effective solutions for erosion corrosion problems, various coating techniques like thermal spraying have become attractive. This study is an experimental investigation on the erosion corrosion behaviour of Detonation gun sprayed coatings on boiler steels and superalloys in air, molten salt and in actual working conditions of coal fired boilers.