Electrodeposition Of Ni-W-Al 2 O 3 Composite Coating And Its Tribological And Corrosion Behaviors

Ni-W-Al₂O₃ composite coatings have high hardness,good wear resistance and corrosion resistance,which used in the field of electronics,machinery and chemical industry widely.However,the dispersibility of the enhanced phase particles?Al₂O₃?has been a bot tleneck problem that constrains the wide application and of the composite coating and technique development.Based on this,Ni-W-Al₂O₃ composite coating was successfully deposited on the surface of 45# steel substrate by DC electrodeposition in the optimized Ni-W bath with adding the enhanced phase Al₂O₃ particles.The effects of Al₂O₃ particle dispersion treatment on the wear resistance and corrosion resistance of the composite coating were investigated.The friction and wear properties and failure mechanism of the treated composite coating under atmospheric environment and deionized water environment were analyzed.Several conclusions were listed as follow:?1?The Ni-W-Al₂O₃ composite coating prepared by electrodeposition is a crystalline structure.Adding different contents of Al₂O₃ does not change the crystal structure of the coating,but can effectively enhance the cathodic polarization of the bath,provide the active deposition sites for the grain deposition,and refine the grain,thus improve the microhardness and thickness of the composite coatings.The wear resistance of the composite coatings increases and decrease with the Al₂O₃ content increases.When the addition amount is 5g/L,the wear resistance of composite coating is the best,and the wear rate is 4.33×10-6mm3/?N·m?.The wear failure mechanism is adhesive wear and abrasive wear.While the addition amount of Al₂O₃ is 20g/L,the coating subjects fatigue wear under the contact stress load.?2?The microstructure of the composite coatings prepared by chemical dispersion of Al₂O₃ particles are compact and uniform,the surface defects reduced obviously,and the Al₂O₃ is evenly dispersed on the surface of the matrix metal coating,and improved the wear resistance significantly.The wear resistance of the composite coatings under BOZ dispersion is the best in ultrasonic field and magnetic field,and the wear resistance under the ultrasonic field is better than that under the magnetic field,its volume wear rate is 2.51×10-6mm3/?N·m?,and the wear rate was reduced 23.71% compared with that of the same condition magnetic field,and decreased by 42.03% compared with the non-dispersed case under magnetic field.The wear mechanism is adhesive wear and abrasive wear,and also accompanied by fatigue wear with the enhanced phase particles not dispersed.?3?The corrosion resistance of the composite coatings is increased with the addition Al₂O₃ content increased.It mainly exhibits positive shift of corrosion potential and negative shift of self-corrosion current density.The corrosion current density decreased by 99.84% compared with Ni-W coating,and its self-corrosion current density is 2.286×10-8A/cm2.After the chemical dispersion treatment of Al₂O₃,the composite coating obtained by compound dispersed in the ultrasonic field exhibited the best corrosion resistance in 3.5% NaCl solution,which lower to 90.32% than that of un-dispersed case,and down to 92.63% in comparison with Ni-W coating,respectively.There is no obvious corrosion pits in the corroded surface of the composite coating,occurred uniform corrosion and pitting corrosion on partial.But the corrosion of the composite coating is apparent.?4?The wear resistance of the composite coating in the water environment is superior to that in the atmospheric environment with corresponding dispersion,and the wear environment does not change the influence on the tribological properties of the chemical dispersion process,but it greatly improves its wear performance.The wear rate of the composite coating under the BOZ dispersion is 1.44×10-6mm3/?N·m?,which is dropped to 42.63% lower than the atmospheric under the same conditions.The wear failure mechanism of composite coating under non-dispersed and SLS-dispersed are adhesive wear and abrasive wear,BOZ dispersion are adhesive wear under,adhesive wear and fatigue wear was produced in composite dispersion.