Study On Microstructure And Properties Of FeCrAl Coating Arc Sprayed On H13Steel

Mold is the foundation of industrial production technological equipment, and thedie life is an important symbol of the measurement of product manufacture level of acountry, it has a direct impact on product quality, cost and efficiency. Hot-work diesteel is one of most important material in the mold industry; the use of mold surfacetechnology improving the hot-work mold life is of great economic significance.In this paper, arc spraying technology is used on H13steel surface to prepareFeCrAl coating and its composite coatings. Metallographic microscope, scanningelectron microscopy （SEM, including EDS microanalysis）, X-ray diffraction instrumentand microhardness meter tester are used to test coating microstructure. The influence ofheat treatment on the microstructure and microhardness of the coating are studied, andthe high temperature oxidation resistance, thermal shock resistance and aluminumcorrosion resistance of coatings are tested, and other two kinds of FeCrAl-Al compositecoatings was studied. The results show that:1) Arc sprayed FeCrAl coating has typical lamellar structure, the microstructure iscompact, includes no obvious big pore, a small amount of oxide film and pore are foundbetween lamellar particles. FeCrAl coating mainly contains Fe-Cr solid solution andsmall amounts of Al₂O₃. The porosity of the coating is about10%, the thickness rangeof230⁵00μm, microhardness HV0.5270.2) Heat treatment has a significant impact on FeCrAl microstructure and porosity,microhardness of coatings. Fe₂O₃oxides and AlFe phase generated in the coatings, theporosity of coating decreases with the heat treatment temperature first and thenincreases. Annealing heat treatment can make the coating uniform, while coatingmicrohardness increases due to the higher degree of oxidation.3) High temperature oxidation resistance of the FeCrAl coating is better than thatof H13steel, because Cr₂O₃formed dense layer in the coating with Cr. The H13steeloxidation at680℃after100h products mainly Fe₂O₃on the surface, it’s loose andcannot hinder the rapid oxidation reaction.4) FeCrAl coating has good thermal shock resistance and the heat treatment canimprove this. Because of the difference of thermal physical properties between FeCrAlcoating and base metal, during the hot and cold cycle large thermal stress is generated inthe coating, and the oxidation increased at the same time, eventually led to the spalling of coating.5) When H13steel is in molten fluid of AC4C aluminum corrosion occurs, twolayers of Fe-Al intermetallic compound are generated on the surface, this corrosionprocess is dominated by diffusion. Under static melting condition, by avoiding thedirect contact of liquid aluminum and steel, FeCrAl layer slows down the formation ofintermetallic compounds and the diffusion process of Fe to the compound to improvecorrosion resistance of H13steel.6) Prepare FeCrAl/Al and FeCrAl/dipping Al composite coatings respectively.Both coatings contain Al and AlFe phase. FeCrAl/Al interlayer is mainly mechanicalbonded, heat treatment make Al diffuse to the inner layer, reaction to intermetalliccompound FeAl₃and close some pores. To FeCrAl/dipping Al coating, metallurgicalbonding occurs between the interlayer, heat treatment makes Al diffuse and theintermetallic compound layer expand. The high temperature oxidation resistance ofcoating is better because of the Al₂O₃generated.