Study On Designand Heat Transfer Mechanism Of Fe-based Electric Arc Spray Coating

This thesis based on the improving the thermal conductivity of coating andenhancing energy efficiency as the background. FeCrSi and FeCrB series alloycoatings were designed to investigate the influence of element silicon and boroncontents on coatings’ phase components, microstructure, thermal conductivity, wearbehavior. Meanwhile, the thermal transport mechanism in iron-based alloy coatingwas explored. The major results are summarized as follows:The as-sprayed FeCrSi series alloy coatings exhibit a typically layered structure.With the increasement of element silicon content in cored wires, the iron-based oxidescontent in coating is gradually decreased, the porosity is greatly increased, at the sametime, the scattering effect of electron and phonon getting severe, the thermalconductivity of coating is reduced. Moreover, it is found that the microhardness of thecoatings are in range of467.5～573.0HV0.1. The coatings’ wear resistance was2.9～3.8times higher than Q235steel. With the decrease of oxides content and increase ofporosity in coating, the corrosion resistance is gradually declined., thermalconductivities and wear resistances of FeCrSi coatings are higher than1Cr17Mocoating, meanwhile its corrosion resistances is weaker than1Cr17Mo coating.The porosities of the designed FeCrB coatings are from3.3%to3.6%. With theincreasement of element boron content in cored wires, the iron-based oxides contentin coating is gradually decreased, the thermal conductivity shows a increasing trend.However, With the increasement of element boron content in cored wires, there ismore and more FeCrB phase generated in coating, the thermal conductivity is reduced;When the concentration of boron in cored wires is2wt.%, the thermal conductivity ofcoating is reached the highest value (8.99W/mK). It was researched that theperformance of different spraying distance in the thermal spraying experiment. Withthe increase of spraying distance, the porosity and oxides content in coating areincreased, and the thermal conductivity of coatings is decreased gradually. On theother hand, the microhardness of the coatings are in range of811.4～820.1HV0.1. The wear resistance of coatings are2.8～5.1times higher than Q235steel. With thedecrease of oxides content and increase of porosity, the weight gain of coating isincreased after Salt water immersion test. On the whole, thermal conductivities andwear resistances of FeCrB coatings are higher than3Cr13coating, but its corrosionresistance is better than FeCrB coatings.