Synthesis and characterization of Ni–Al2O3 composite coatings containing different forms of alumina

Abstract

Electrodeposited Ni-Al 2 O 3 composite coatings were prepared using alumina powders synthesized from solution combustion method, precipitation method and a commercial source. Solution combustion synthesized alumina powder yielded a-phase; precipitation method yielded purely c-phase; commercial alumina powder was a mixture of a-, d-and c-phases. A nickel sulfamate bath was used for electro-codeposition. The current densities (0.23 A dm -2 for 20 h, 0.77 A dm -2 for 6 h, 1.55 A dm -2 for 3 h and 3.1 A dm -2 for 1.5 h) and bath agitation speeds (100, 200, 600 and 1000 rpm) were varied. The pH variations of the bath were higher during the electrodeposition of combustion synthesized alumina. The effect of different forms of alumina particles on the microhardness and microstructure of the nickel composite coating was studied. Composite coating containing combustion synthesized alumina particles was found to have higher microhardness (550 HK). It was found that at lower agitation speed (100 rpm), bigger particles were incorporated and at higher agitation speed (1000 rpm), smaller particles were incorporated. The area fraction of alumina particles incorporated in nickel matrix was highest for commercial alumina (24%). This study shows that it is not suffice to take just the current density and stirring speeds into account to explain the properties of the coatings but also to take into account the source of particles and their properties.

Electro co-deposition of Ni–Al2O3 composite coatings

“…In fact, the effect of the concentration alone [12,17], the current density [4,11,27,[36][37][38]51] and the combined effects of concentration and current density [11,19,33,39,40], current density and particle size [20] and concentration and particle size [14,37] were reported by other research groups, often giving contradictory results. Aruna et al [41,42] have recently described the effect of different forms of Al 2 O 3 on the coatings produced by electro co-deposition; they found a variation in both the corrosion resistance and the hardness of coatings containing either alpha or gamma alumina phase particles. Furthermore they investigated the effect of stirring speeds (100-1000 rpm) on the coating composition showing that the speed affected the average size of particle in the deposit [42].…”

“…Aruna et al [41,42] have recently described the effect of different forms of Al 2 O 3 on the coatings produced by electro co-deposition; they found a variation in both the corrosion resistance and the hardness of coatings containing either alpha or gamma alumina phase particles. Furthermore they investigated the effect of stirring speeds (100-1000 rpm) on the coating composition showing that the speed affected the average size of particle in the deposit [42]. Similarly Badarulzaman et al [43] studied the effect of 'agitation rate' on the deposition process using a magnetic rotating bar with speed rates 50-250 rpm.…”

Corrosion- and wear-resistant properties of Ni–Al2O3 composite coatings containing various forms of alumina

“…Details regarding the preparation and characterization of alumina powders and Ni-alumina composite coatings have already been published [19]. The Ni-alumina composite coatings (i) Ni-Al 2 O 3 -1 (containing combustion synthesized alumina), (ii) Ni-Al 2 O 3 -2 (containing precipitation synthesized alumina), and (iii) NiAl 2 O 3 -3 (containing commercial alumina) were electrodeposited at 15.5 mA cm -2 for 36 min at 600 rpm (magnetic stirring).…”

“…Most of the reported literature have discussed the synthesis and properties of Ni-Al 2 O 3 composite coatings containing mostly a-alumina particles. In a recent article, we have reported the preparation of Ni-Al 2 O 3 composite coatings containing different crystallographic forms of alumina [19]. To the best of our knowledge, there are no reports on the comparative study on the corrosion-and wear-resistant properties of Ni-Al 2 O 3 composite coatings containing different phases of alumina.…”

The Effect of Dispersion Phases of SiC and Al2O3 on the Properties of Galvanic Nickel Coatings

“…Alumina (Al 2 O 3 ) has, in turn, satisfactory mechanical and physical properties, combined with good corrosion resistance. Its high hardness, high dielectric properties and thermal conductivity make it an excellent material for a wide range of applications [6].…”