Deposition and characterization of nickel–niobium composite electrocoatings

Abstract

Ni-Nb composite electrocoatings were obtained on carbon steel from Watts bath, containing suspended 20 lm size niobium powders. The effect of cathodic current density, electrolyte stirring rate and concentration of Nb particles in the bath on the deposit morphology and texture, volume fraction of co-deposited Nb particles and microhardness was investigated. The Ni-Nb composite layers presented a rough morphology with randomly oriented Ni grains, whereas pure Ni coatings obtained under the same experimental conditions were smooth and showed highly preferred orientation in the [110] or [100] direction. Stirring rate of the electrolyte and concentration of Nb particles in the bath are the main parameters affecting the incorporation of Nb particles. The Nb incorporated volume fraction was 11-14%, 17-19%, 27-32% and 34-37% for the 20 g L -1 Nb/550 rpm, 20 g L -1 Nb/400 rpm, 40 g L -1 Nb/400 rpm and 40 g L -1 Nb/550 rpm conditions, respectively. The microhardness of the Ni-Nb composite coatings obtained at 20 and 40 mA cm -2 was higher than that of pure Ni layers, due to grain refining. Incorporation of Nb particles in Ni coatings improved the corrosion resistance of the deposits in NaCl and H 2 SO 4 solutions.

Effect of Nickel-Niobium Coating on Fatigue Resistance of SAE 1020 Carbon Steel

“…Coating compound only nickel tend to be less rough. The characteristics observed in nickel-niobium coatings in this work, are very similar morphologically to the results presented by Robin and Fratari [19]. They confirm that the increase in surface roughness and any formation of clusters on the surface of the coatings is due to the presence of niobium particles in the electrolytic bath.…”

Characterization of copper–silicon nitride composite electrocoatings

“…Thus, the incorporation of Si 3 N 4 particles to copper did not affect the orientation of copper grains. In other cases, such as TiO 2 in copper [9] and both WC and Nb in nickel [22,23], the incorporation of particles to the metallic electrocoating was shown to change the orientation of the matrix crystals. Figure 6 shows a typical SEM micrograph of the crosssection of composite coatings.…”

Efeito Da Eletrodeposição De Níquel-Nióbio No Comportamento Em Fadiga De Um Aço Sae 1020

“…Essa deposição não uniforme pode ter ocorrido devido à alta granulometria das partículas de nióbio, assim como a inexistência de rotação do corpo de prova durante o processo de eletrodeposição. Menores granulometrias de nióbio aplicadas por Robin e Fratari resultaram em camadas depositadas mais homogêneas [6].…”

“…Recobrimentos de Ni em aço carbono produzem considerável melhora do limite de fadiga, principalmente quando se tem algum tratamento posterior à eletrodeposição para a eliminação de eventuais tensões superficiais [2]. A adição de partículas de Nb ao banho eletrolítico de níquel Watts produz recobrimento de níquel metálico com a presença de particulados de nióbio que concorrem para aumento da dureza superficial [4][5][6]. Aumento de dureza superficial está correlacionado com aumento de resistência à fadiga [2], daí o recobrimento de Ni-Nb ser favorável à melhora dessa propriedade do aço [7,8].…”