Experimental Research Of Ni-NANO-La₂O₃ Composite Electroforming

Composite electroforming is the combination of composite electrodeposition and Electroforming, which is referred to the process that solid particles or fibers co-deposit with single metal or alloy in electrolyte. Composite electroformed deposit has a compact and uniform microstructure. Meanwhile, the nanocomposite deposit exhibits higher microhardness, and is greatly enhanced in wear resistance, corrosion resistance and high-temperature oxidation resistance.In this paper, Ni-nano-lanthanum oxide (La2O3) composite deposit was obtained by electroforming from a nickel sulfamate solution containing La2O3 nanoparticles. The effects of process parameters on the concentration of La2O3, morphology and microstructure of the nanocomposite deposit were studied. Furthermore, mechanism of wear was discussed. Microhardness measurement of composite layers was performed. The friction and wear tests of composite layers were also carried out.It is found that the concentration of embedded La2O3 particles reaches up to 3.1 wt% and the codeposited-La2O3 content in the composite deposit is markedly affected by the La2O3 particle concentration in the electrolyte and then the current density. The scanning electron microscopy (SEM) analysis shows that the electroformed deposit has a more smooth surface and a more compact microstructure with the increase of the concentration of La2O3. The electroformed deposit has the less codeposited-La2O3 content and the more rough crystals of Ni matrix under a high current density. X-ray Diffraction (XRD) analysis reveals that preferred crystallographic orientation of Ni electroformed deposit is changed by the codeposition of nanoparticles and Ni matrix, which leads to the diversity of performance among the electroformed deposit.According to the microhardness tests, the microhardness of the composite deposit can reach up to 520 HV, microhardness of composite deposit is increased by 80 %, compared with that of pure Ni deposit. Moreover, friction coefficient and wear rate of composite deposit notably reduces with the increase of the La2O3 concentration. The friction and wear properties of composite deposit are significantly improved. With the increment of the concentration of La2O3 particles, wear mode of composite deposit is gradually shifted from adhesion wear to abrasive wear. When the concentration of La2O3 nanoparticles reaches 3.1 wt%, composite deposit has a smooth surface and only exhibites slight abrasive wear.