Research On Properties Of Iron-based Protective Coatings By Supersonic Arc Spraying

As the backbone of current national economy,electrical power industry takes coal as main fuel and the coal-fired power plants share 75%of the domestic power generation.The problems,on heating surface of the "Four Tubes" such as abrasion,ash accumulation,slagging and corrosion,are aggravated.The stability and reliability of the thermal power generation system depend on the wear and corrosion resistance of the key components of the units.In view of the failure of the boilers,which mainly consists of erosion wear and corrosion,a set of equipment that can be used maturely in the boiler system protection technology is of great significance to improve the power generation capacity of coal-fired boilers and reduce the unit operating costs.The failure of boiler pipe often starts from the surface of the workpiece.Therefore,the surface "Four Tubes" can be strengthened to enhance the wear and corrosion resistance of the boiler without replacing a new one,so as to prolong the service life of the boiler system.The traditional means,such as brush anti-corrosion wear-resistant coating,hot-dip aluminizing and spraing welding alloy,showed no satisfactory results.With the development of surface engineering technology,thermal spraying has been developed and applied to provide reliable technical support for boiler pipe surface strengthening treatment.In this paper,the supersonic arc spraying technique was used to prepare the iron-based protective coatings resistant to high temperature erosion and corrosion on the substrates(20 steel,12CrMoV steel)using iron-based solid core and cored wires.The microstructure,constitution,hardness,thickness,porosity,bond strength and bending strength were characterized by field emission scanning electron microscopy(FESEM),X-ray diffraction,microhardness tester,porosity analyzer and universal tensile tester.By using box muffle furnace,photoelectric analytical balance,salt spray test machine,CHI660E electrochemical workstation,The high-temperayure oxidation resistance,corrosion resistance,salt-fog corrosion resistance,electrochemical stability,erosion resistance and thermal stability of substrate materials(20 steel,12CrMoV steel)and iron-based coatings was characterized and analyzed.The results are as follows.1.Coatings have high bond strength,FeCrAlNi and FeCrAIRE coating have stronger bonding strength than FeCr(Si,Mn,B4C)and FeCr(Si,Mn,C)coating.The bonding layer can obviously enhance the bond strength of composite coating;the ranked from strong to weak correlated with the bending strength were:FeCr(Si,Mn,B4C)-substrate>FeCrAlRE-substrate>FeCr(Si,Mn,C)-substrate>FeCrAlNi-substrate.The wear rate is ranked from largest to smallest:FeCr(Si,Mn,C)>FeCr(Si,Mn,B4C)>FeCrAlNi>FeCrAIRE.2.Sequence of mass gains and oxidation rates for substrates and coatings was as follow:12CrMoV steel>20 steel>FeCrAlNi coating>FeCr(Si,Mn,C)coating>FeCr(Si,Mn,B4C)coating>FeCrAlRE coating.FeCrAIRE coating exhibited a lower oxidation rate which meant FeCrAIRE coating had more excellent high-temperature oxidation resistance than others.FeCrAIRE coating also have superb properties in hot corrosion and neutral salt-fog environment.3.Sequence of thermal shock cyclic times was as follow:FeCrAIRE coating>FeCrAlNi coating>FeCr(Si,Mn,B4C)coating>FeCr(Si,Mn,C)coating.At room temperature and high temperature erosion experiments,FeCrAIRE coating have the lowest wear rate.At room temperature,the wear rate of the coating is the lowest at 45° and the maximum at 90°.At high temperatures,the wear rate is greatest at 90°,and the wear rate is not much different between the other two angles.