Ni/nano-TiO₂ Composite Electrocoatings: Correlation Between Structural Characteristics Microhardness and Wear Resistance

Abstract

Electrodeposition / Crystalline Orientation / Microharness / Wear Resistance / Grain SizeNanocomposite coatings were obtained by electrochemical codeposition of TiO 2 nano-particles (mean diameter 21 nm, Degussa P 25 ) with nickel, from an additive-free Watts type bath. Pure Ni and composite Ni-TiO 2 coatings were electrolytically deposited under both direct and pulse current conditions and an extended region of electrolysis conditions (pH, current density, TiO 2 loading in the bath). Pure Ni deposits were produced under the same experimental conditions for comparison. The aim of this study was to correlate the observed structural characteristics of the coatings (crystallographic orientation and grain size of nickel matrix,) and incorporation percentage with the resulting microhardness values and tribological behavior. Overall, the data have demonstrated that when attributing the observed strengthening effect of composites, not only grain refinement and dispersion strengthening mechanisms, but also preferred crystalline orientation should be taken into consideration. The variation of the wear rate is directly associated with the microhardness variations and consequently, governed by the same parameters that determine the synergistic strengthening mechanism proposed. Pure and composite coatings with [110] crystalline orientation exhibited the highest microhardness values and wear resistance.

Electrodeposition of Photocatalytic Sn–Ni Matrix Composite Coatings Embedded with Doped TiO2 Particles

“…Hence, the objective of this study is twofold: (a) estimate the optimum electrodeposition parameters by tuning applied current density and particles' loading in the bath that result to the production of composite Sn-Ni/doped-TiO 2 nano-coatings with high co-deposition percentage of particles dispersed into alloy metal matrix, and (b) investigate the correlation between compositional and morphological characteristics of the produced surfaces with the observed photocatalytic performance under visible light, taking into consideration that the proposed coatings should preserve attractive appearance, high hardness and wear resistance in comparison with pure Sn-Ni ones. It is worth mentioning that the electrodeposition of coatings reinforced by TiO 2 particles has been widely investigated in nickel matrix [6,7,14,16,17] and quite a few in alloy metal matrix [18][19][20]. Very limited studies appeared in literature concerning Sn-Ni/TiO 2 electrodeposition [21], while up to the knowledge of the authors no similar work regarding co-electrodeposition of chemically modified TiO 2 particles in Sn-Ni matrix, and the study of photocatalytic behavior and mechanical properties of this kind of electro-coatings exists.…”

Effects of SiC particles codeposition and ultrasound agitation on the electrocrystallisation of nickel-based composite coatings

“…Additionally, the material was also strengthened by the rise in internal stresses [41]. Furthermore, as demonstrated by Spanou and Pavlatou [45], the changes in the crystallographic orientation might have also influenced the final hardness of the deposits.…”

“…Furthermore, the hardness value of Ni/SiC50 was somewhat similar to Ni/SiC5k, despite the higher micro-SiC content of the latter, due to the presence of larger grains and a more dominant \ 100 [ texture. Spanou and Pavlatou [45] also observed a lower microhardness in Ni/nano-TiO 2 deposits with \ 100 [ texture compared to a Ni matrix with \ 110 [ texture, regardless of particles incorporation rate, highlighting the importance of considering the effects of a given preferred orientation in hardness. The use of US agitation promoted an increase in SiC50 content (2.8 vol.%), internal stress and grain refinement.…”