Synthesis and Characterization of Nano-Al2O3 Enhanced Ni-P-Mo Composite Coatings on HSLA steel Substrates by Electro-deposition Method

Abstract

HSLA (AISI 4340 alloy) steel has applications in industries like auto-motives, military, nuclear, aeronautical field, oil and gas sector etc. where it is mostly exposed to extreme conditions i.e., humidity, stress and high temperature etc. making it vulnerable to corrosion and wear issues raising the demand for more robust and effective materials having good surface properties and stability for protection purposes. This research project encompasses the scope to develop and analyze the electro-deposited nickel alloy and composite coatings with good mechanical stability and properties like low degradation in highly corrosive or high temperature applications, as the potentail solution to the above mentioned problem when compared to bare HSLA steel. In this work, impact of different Al₂O₃ nano-particles (40~50nm in size) concentrations (i.e., 0.1, 0.3, 0.7, 1 g/L) on wear and corrosion resistive properties of Ni-P-Mo coatings on bare HSLA (AISI 4340) steel samples, was studied and analyzed via characterization techniques such as SEM, AFM, Micro-hardness, Nano-indentation, pin-on disk micro-testing for wear and potentiodynamic polarization method using 3.5 wt. % NaCl solution for corrosion testing. Electro-deposition technique was used to deposit Ni-P-Mo alloy and Ni-P-Mo/Al₂O₃ composite coatings on steel substrates. SEM and AFM results reveal homogeneous, compact, denser and rougher coatings as nano-particles were incorporated in Ni-P-Mo alloy comparatively. Hardness was enhanced and improvement in mechanical wear resistant properties were witnessed as well from 5.28E⁻⁸ mm3/mm (Ni-P-Mo) to 0.373E⁻⁸ mm3/mm (Ni-P-Mo /0.3g/l Al₂O₃). Corrosion rates in mils-per-year of Ni-P-Mo coatings were also reduced significantly from 4.8mpy (Ni-P-Mo) to 0.3mpy (Ni-P-Mo /0.3g/l Al₂O₃) by the addition of Al₂O₃ particles. Positive results obtained suggest the potential use of these composite coatings in various industrial sectors.

HSLA (AISI 4340 alloy) steel has applications in industries like auto-motives, military, nuclear, aeronautical field, oil and gas sector etc. where it is mostly exposed to extreme conditions i.e., humidity, stress and high temperature etc. making it vulnerable to corrosion and wear issues raising the demand for more robust and effective materials having good surface properties and stability for protection purposes. This research project encompasses the scope to develop and analyze the electro-deposited nickel alloy and composite coatings with good mechanical stability and properties like low degradation in highly corrosive or high temperature applications, as the potentail solution to the above mentioned problem when compared to bare HSLA steel. In this work, impact of different Al₂O₃ nano-particles (40~50nm in size) concentrations (i.e., 0.1, 0.3, 0.7, 1 g/L) on wear and corrosion resistive properties of Ni-P-Mo coatings on bare HSLA (AISI 4340) steel samples, was studied and analyzed via characterization techniques such as SEM, AFM, Micro-hardness, Nano-indentation, pin-on disk micro-testing for wear and potentiodynamic polarization method using 3.5 wt. % NaCl solution for corrosion testing. Electro-deposition technique was used to deposit Ni-P-Mo alloy and Ni-P-Mo/Al₂O₃ composite coatings on steel substrates. SEM and AFM results reveal homogeneous, compact, denser and rougher coatings as nano-particles were incorporated in Ni-P-Mo alloy comparatively. Hardness was enhanced and improvement in mechanical wear resistant properties were witnessed as well from 5.28E⁻⁸ mm3/mm (Ni-P-Mo) to 0.373E⁻⁸ mm3/mm (Ni-P-Mo /0.3g/l Al₂O₃). Corrosion rates in mils-per-year of Ni-P-Mo coatings were also reduced significantly from 4.8mpy (Ni-P-Mo) to 0.3mpy (Ni-P-Mo /0.3g/l Al₂O₃) by the addition of Al₂O₃ particles. Positive results obtained suggest the potential use of these composite coatings in various industrial sectors.