Fabrication And Properties Of Wear And Corrosion Resistant Coating On Q235 Steel

Q235 steel is one of the most commonly used engineering materials for equipment components in the petrochemical industry due to its good machinability,high plasticity and toughness,and low price.With the rapid development of petroleum and chemical industry,the problem of corrosion and safety of equipment is becoming more and more prominent,especially in the petrochemical industry.The preparation of composite coatings on Q235 steel can retain the mechanical properties of the base material,but also make its surface with excellent wear and corrosion resistance,delaying the premature failure of the Q235 steel surface due to wear and corrosion,thus improving the service life of the equipment components.In this work,Ni+WC and Ni+Al₂O₃ coatings were prepared on Q235 steel using atmospheric plasma spraying（APS）technology.The microstructure,interfacial bonding quality and microhardness of the coating were analysed,and the effects of various Ni60 additions on the wear and corrosion resistance of tungsten carbide and alumina-based composite coatings were researched.The surface modification of Ni+WC and Ni+Al₂O₃ coatings by（heptadecafluoro-1,1,2,2-tetrahydrodecyl）trimethoxysilane(C1₃H₁₃F₁₇O₃Si)further improves the hydrophobicity and corrosion resistance of the coatings,and the mechanism of wear and corrosion resistance of the composite coatings is explored.The prepared coatings were characterised for their microstructure.The results show that the surface of Ni+WC and Ni+Al₂O₃ coatings has a typical lamellar stacking structure,and the surface of the coatings is spread with defects such as molten particles,semi-molten and unfused particles and pores.When the Ni60 content is 10%and 20%,the Ni+Al₂O₃ coatings show poor deposition rate,more defects in the coatings and a coating thickness of 80±5μm.The bonding strength of the 10%Ni+Al₂O₃ coating to the substrate is only 25 MPa.The remaining six groups of composite coatings have a homogeneous composition and can reach a thickness of 125±10μm.The bond strength between these coatings and the substrate is rather high.The Ni+WC coating has the highest microhardness value when the Ni60content is 10%,with an average microhardness value of 925.48 HV_0.1.As the Ni60 content of the coating increases,the microhardness of the Ni+WC coating gradually decreases.When the Ni60 content is below 20%,the Ni+Al₂O₃coating has a non-uniform composition,many defects and low microhardness values.When the Ni60 content is 30%,the maximum microhardness value of Ni+Al₂O₃ coating is obtained,which is 627.34 HV_0.1.Sliding friction test is carried out with ball disc friction pair.The wear resistance of the coating was tested by coating-Si₃N₄ system.The results show that the friction coefficient and wear rate of the Ni+WC coating gradually decrease as the Ni60 content increases.The 10%Ni+WC coating has a friction coefficient of 0.302 and a wear rate of 3.03×10^-5 mm³/（N·m）.No significant pattern in the variation of friction coefficient and wear rate of Ni+Al₂O₃coatings.When the Ni60 content is 10%,the Ni+Al₂O₃ coating composition is not homogeneous and the friction coefficient curve fluctuates strongly.When the Ni60 content is 30%,the Ni+Al₂O₃ coating has the best wear resistance,with a coating friction coefficient of 0.401 and a wear rate of 9.67×10^-5mm³/（N·m）.The wear resistance of Ni+WC coating is better than that of Ni+Al₂O₃ coating.The electrochemical tests show that Ni+WC and Ni+Al₂O₃ coatings achieve the best corrosion resistance when the Ni60 content is 40%.The corrosion current density is 6.2645×10^-6 A/cm² for the 40%Ni+WC coating and 8.1184×10^-6 A/cm² for the 40%Al₂O₃ coating.After the chemical modification,the corrosion resistance of the coatings is all improved.The 30%Ni+Al₂O₃ coating shows the greatest improvement in chemical corrosion resistance,with corrosion current density values decreasing by two orders of magnitude after coating modification.