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

Abstract

This study analysed the influence of the codeposition of SiC particles with different sizes: 50 nm, 500 nm and 5 μm, and the type of bath agitation (stirring or ultrasonic) on the electrocrystallisation of nickel coatings. The composites matrix microstructure was analysed by means of SEM, EBSD and XRD, to evaluate the grain size, crystal orientation, and internal stresses and was benchmarked against pure nickel samples electrodeposited in equivalent conditions. The codeposition of nano- and microsize particles with an approximate content of 0.8 and 4 vol.%, respectively, caused only a minor grain refinement and did not vary the dominant < 100 > crystal orientation observed in pure Ni. The internal stress was, however, increased by particles codeposition, up to 104 MPa by nanoparticles and 57 MPa by microparticles, compared to the values observed in pure nickel (41 MPa). The higher codeposition rate (11 vol.%) obtained by the addition of submicron-size particles caused a change in the grain growth from columnar to equiaxial, resulting in deposits with a fully random crystal orientation and pronounced grain refinement. The internal stress was also increased by 800% compared to pure nickel. The ultrasound (US) agitation during the deposition caused grain refinement and a selective particle inclusion prompting a decrease in the content of the particles with the larger particles. The deposits produced under US agitation showed an increase in the internal stresses, with double values compared to stirring. The increase in the deposits microhardness, from 280 HV in pure Ni to 560 HV in Ni/SiC submicron-US, was linked to the microstructural changes and particles content. Graphical abstract

Strengthening mechanisms and wear behavior of electrodeposited Ni–SiC nanocomposite coatings

“…The samples from previous studies (Table 2) showed preferential crystal \100[ orientation growth independent of the current density and agitation type. They differed only in the composites containing SiC500, where random orientation growth was dominant instead of preferential crystal orientation growth [14]. The change in texture in the deposits led to a variation in the surface morphology, from a pyramidal-shaped surface observed in deposits dominated by the \100[ orientation to globularshaped structures in Ni/SiC500 composites.…”

“…Sanaty-Zadeh et al [4] also observed overestimation in the theoretical calculation, reporting an increase in discrepancy in the sums of contribution method compared to others methods. The US agitation caused selective entrapment of submicron particles [14]; only the smaller particles (245 ± 55 nm average diameter) codeposited in SiC500-DC4/US. The US caused a good and uniform dispersion of particles within the matrix, resulting in an interparticle spacing of 116 ± 57 nm (Figs.…”

“…SiC500 particles reported a high particle content of approximately 11 vol.% in the as-produced state; after surface treatment, the codeposition was improved up to 19.3 vol.% [15]. However, the US agitation negatively impacted the codeposition rate, provoking a decrease in the content [14] due to the bounce-off effect in the particles. Nonetheless, comparable to SiC60 particles, the US agitation provided better particle dispersion, from agglomerates (Fig.…”

“…The use of US agitation promoted an increase in the codeposition of nanoparticles. The US cavitation facilitated particle transport, aiding their movement through the diffusion layer, enriching the vicinity of the cathode, permitting a higher nanoparticles entrapment rate [14,17], and resulting in an increase in content for both SiC50 and SiC60. In addition, US agitation substantially improved particles dispersion (Fig.…”

“…In the present study, microindentation and advanced microstructural analyses were used to define the strengthening mechanisms present in electrodeposited nickel-based composite coatings produced under comparable conditions in previous studies [13][14][15][16][17]. Different pure nickel deposits electroplated under various current densities were used to establish a Hall-Petch relationship and define the contribution of the grain size hardening effect of the matrix in the electrodeposits [18] driven by electric currents: the finer the grains the harder is the resulting material due to the increase effect of grain boundaries as impediment to the dislocation movements.…”