Study Of Nickel-based Alumina Nanoparticles Electroforming Layer Prepared In Supercritical Condition

This paper was supported by the National Natural Science Foundation of China (GrantNo.51275222), Natural Science Foundation of Jiangsu Province (BK2012585) andChangzhou Industry (CE20100045). The Ni-Al2O3composite materials electroformed insupercritical CO2microemulsion were mainly researched and analyzed. The superiority ofsupercritical electroforming was fully revealed by compared to electroforming in ultrasoniccondition.Ni-Al2O3composite materials were prepared in different process conditions undersupercritical and ultrasonic condition with orthogonal test method choosing four factorsand three levels. Then the microhardness, surface morphology, content of Al2O3and crosssection of the composite electroforming layers were tested by digital micro-hardness tester,SEM, EDS and metallographic analysis system.With standard analysis of the microhardness of electroforming layers, range analysis andvariance analysis were conducted to the result of the orthogonal test. The results show thatthe biggest impact factors are pressure, temperature, alumina content, current density, inthat order. In addition, pressure, alumina content, current density and temperature have asignificant effect on the microhardness value of electroforming layers. The results alsoshow that the best technological parameter were12~16MPa of pressure,60~80g·L–1ofalumina content,40℃of temperature and5A·dm-2of the current density.The influence of different factors under supercritical condition on microstructure andperformance of Ni-Al2O3composite electroforming layer were analyzed. The compositeelectroforming layers prepared under supercritical and ultrasonic condition were alsocompared. The microhardness of the coating prepared under the optimal process conditionsof supercritical electroforming reached to1354.52HV, and the alumina content inelectroforming layer was14.09％(weight percentage). Whereas the microhardness was just641.26HV and the alumina content was5.59％(weight percentage)to the latter. Comprehensive results show that the electroforming layers electroformed in supercriticalconditions has more smooth and dense surface, and better properties.