Microstructure And Properties Of Electro-Spark Surface Deposition FeCrAl And NiCr Coating

FeCrAl and NiCr alloys are widely used as coating materials in the industry.They have good mechanical properties,high temperature oxidation resistance and corrosion resistance.There are many ways to prepare coatings,but for some special-shaped parts,large-scale construction with complex structures.It is difficult to prepare the coating,and compared with other coating preparation techniques,the Electro-spark deposition technology has the advantages of small heat input,convenient operation,strong flexibility,small volume and convenient carrying.It can be used for preparation and repair of small space coatings in the field,and the substrate material does not deform and degrade.Therefore,the self-built automatic Electro-spark deposition platform is used to deposit FeCrAl and NiCr coatings on the surface of P92 steel to improve the oxidation resistance and corrosion resistance of P92 steel at high temperature.?1?The FeCrAl coating was deposited on the surface of P92 steel by the automatic deposition platform according to the process parameters designed by the orthogonal table.The influence of process parameters on the microstructure and properties of the coating was studied,and the transition law of coating quality was obtained.With the pulse energy increases,the coating quality increases,the coating hardness increases,the surface roughness decreases,and the bonding force becomes larger,but when the pulse energy reaches a critical value,micro-cracks appear on the surface of the coating.The quality of the coating is degraded.The voltage has a great influence on the mass transfer-coefficient of the deposited layer.Considering the deposition efficiency of the coating,microhardness,bonding force,surface roughness and microstructure of the coating,Process 3?2.1 J?,voltage 120V,capacitance 300 uF,discharge frequency 4KHz,prepared as a later FeCrAl and NiCr coating Preferred process.?2?Studying the high temperature cyclic oxidation resistance of FeCrAl coating and NiCr coating and matrix material at 750°C,measuring the cyclic oxidation kinetics curve,and detecting the microstructure and microstructure changes of coating and matrix materials before and after oxidation.The FeCrAl coating did not fall off after 100 h of cyclic oxidation.The oxidation kinetic curve followed the parabolic law.The oxidation rate constant K=4.58×10^-3 g²·m^-4·s^-1,and the surface of the coating formed Cr₂O₃ and Fe+2Al₂O₄ phase.The NiCr coating did not fall off after 100 h of cyclic oxidation.The oxidation kinetics followed a parabolic law.The oxidation rate constant K=4×10^-3 g²·m^-4·s^-1,and the surface formed Cr₂O₃ and Ni?Cr₂O₄?phases.The FeCrAl coating has better oxidation resistance than the NiCr coating.?3?The properties of high temperature cyclic hot corrosion?Na₂SO₄+K₂SO₄?of FeCrAl coating and NiCr coating and matrix material at 750°C were studied,and the hot corrosion kinetic curve was measured.The hot corrosion kinetics curve of FeCrAl coating follows the parabolic law,the corrosion rate constant K=9.1×10^-3 g²·m^-4·s^-1,and the hot corrosion layer is mainly composed of Fe₂O₃ and Cr₂O₃ phases.The hot corrosion kinetics curve of NiCr coating follows the parabolic regular,the hot corrosion rate constant K=1.43×10^-2 g²·m^-4·s^-1,and the hot corrosion layer is mainly composed of Ni?Cr₂O₄?,NiO and Cr₂Ni₃ phases.FeCrAl coating and NiCr coating have better thermal hot corrosion resistance than matrix material.