## 3 Results and Discussion  
### Characterization of Coatings  
Figure 2 shows the panoramic view of the surface morphology from different samples. Back scattered mode was applied to highlight residual particles on the surface. The Ni-P coatings with no SiC additions exhibit a characteristic nodular cauliflower--like morphology. Nevertheless, all samples show a surface that is smooth, of limited defects, which, if present, are most likely located at  
the interception points of the spherical nodules. Additionally, no severe morphological alterations of the surface characteristics seem to be induced by the heat treatment of the plain Ni-P coatings, while the SiC particles introduction slightly affects the surface morphology. The SiC fraction was measured by EDS in different parts of the surface to assure a homogeneous deposition over the area, since the stirring conditions may affect the SiC particles incorporation. EDX's analyses confirmed that the codeposited fraction of SiC is about 3% vol. Figure 3 shows the XRD diagrams of the samples before heat treatment, while Figure 4 shows the similar analysis after heat treatment. Intensive SiC peaks can be distinguished. The XRD spectra of the non-treated specimens show the characteristic peak of the amorphous Ni-P structure that was also observed in other studies [1; 2; 3; 42; 43; 1; 5; 42]. It has been reported that the amorphisation of Ni due to the high amount of phosphorus is due to the fact that P presence within the lattice and the subsequent strain fields it causes, lead to primary grain growth inhibition that becomes so intensive, so that practically nanocrystallinity and eventually amorphisation is achieved [1; 2; 3; 4; 5; 6]. Figure 2: Scanning electron microscope pictures the different electrodeposited coating systems produced at 50% duty cycle, 100 Hz with and without heat treatment (HT) at 400 \({}^{\circ}\)C.  
However, the overall structure has been totally altered after the application of heat treatment, as it can be seen in Figure 4. Narrow intensive peaks in all cases declare the crystallization process taking place during this stage. Phase identification does verify the crystallization process, which is also observed in many other cases [1; 2; 3; 4; 5], as crystalline Ni FCC phase is distinguished in all samples along with the presence of the precipitated Ni\({}_{3}\)P intermetallic phase, which is also a classical outcome of the heat treatment and crystallization process [1; 2; 3; 4; 5]. XRD did not reveal the presence of SiC phase in the case of heat treated samples as compared to the as-coated samples. Figure 3: X-ray diffraction (XRD) spectra of the plain and SiC reinforced coatings developed at 50% duty cycle at 100 Hz prior to heat treatment. The surface topology of the resulted coatings is another very important parameter that it seems to be affected by the deposition process and its parameters. Figure 5 graphically shows the average surface roughness and the RMS roughness of the produced coatings before and after heat treatment, as measured from the profilometer. The introduction of reinforcing particles leads to an alteration of the coating surface smoothness. This effect is most likely associated with two combined mechanisms: 1) particle introduction leads to the appearance of surface imperfections, which make the surface landscape more intense and, as such, the roughness is increased, b) the particles themselves unsettle the continuity of the surface deposit and they consist site for deposition and nucleation of the metallic matrix. As particles perturb of the surface and since deposition follows the existed surface pattern and perturbation in electroplating, as the coating is built up, the initial perturbations due to particles become more intensive and, as such, the roughness may increase. Figure 4: XRD spectra of the plain and SiC reinforced coatings developed at 50% duty cycle at 100 Hz after heat treatment. High particle entrapment means that their spatial inter-particle distance is reduced if homogeneity is considered in their location.