Research On Corrosion Resistance Of Amorphous Coating In Simulated Flue Gas Environment For Power Plant Boiler

In the actual operation process,because of the coal and other reasons,the exhaust gas temperature is always higher than design value in many coal-fired power plants,which reduces the efficiency of the boiler.It is necessary to recycle flue gas waste heat so as to improve boiler efficiency.There is an amount of sulfur in the coal,in the process of flue gas waste heat utilization,steam and sulfuric acid vapor will flow through low temperature heating surface,and then condense in the wall.Corrosion will influence the safe operation of the equipment,in order to utilize exhaust gas waste heat,it is necessary to obstacle the limitation of the corrosion.Amorphous coating is a new kind of functional material,which have shown excellent properties,such as high strength,high hardness and great resistance of abrasion and corrosion,which makes it one of the possible solutions of the large-scale corrosion problem.In this paper,research will be carried out about the mechanism of low temperature sulfuric acid dew point corrosion.Fe-based amorphous composite coatings were prepared by laser-cladding method.The results of metallographic analysis,SEM,XRD and Vickers hardness analysis indicated that the coatings are metallurgically bonded to the substrate,which could be determined from the dense coating uniformity and less surface cracking.There was an obvious stratification phenomenon: coating layer,transition layer and substrate layer.The Vickers hardness of the coatings have increased by 2~3 times.H2SO4(0.5mol/l)and NaCl(3.5%)electrochemical tests were carried out,and the Tafel polarization curves of the three samples showed that the corrosion potential of amorphous composite coatings were higher than that of the substrate,the corrosion potential of amorphous composite coatings have increased by 0.1V~0.15 V.The simulated flue gas corrosion test showed that the resistance corrosion speed of amorphous coatings is 2~3 times faster than that of the substrate.The unique nano-crystalline/amorphous composite structure is the key reason for the enhancement of the hardness and corrosion resistance.This research will be an important theoretical basis for the optimization of corrosion resistant materials in low-temperature flue gas environment,and will contribute to the promotion of flue gas waste heat utilization from the theoretical analysis to the engineering practice.