*3.2.3. Microhardness of Ni-P-SiC electrodeposits*

The microhardness of the Ni-P-SiC coatings with different SiC concentrations was measured. Figure 9 illustrates the surface microhardness of the electrodeposited Ni-P-SiC coatings as a function of the SiC concentration in the metallic matrix. As observed from the curve, the hardness of the coating increases to values in the range of 580 to 620 HV when SiC particles are dispersed in the metallic matrix. This behavior is associated with increased hard sites. Despite such increases, the obtained hardness was less than that of a hard Cr coating, which has a microhardness of 1020 HV [24].

#### *3.2.4. Wear resistance*

**Figure 6.** Typical GDS elemental composition profiles of Ni-P-SiC coatings electrodeposited at 0.042 mA/cm2

concentration values, the percentage of SiC in the coating matrix decreases.

mM DTAB + 0.02 g mL-1 SiC.

130 Electrodeposition of Composite Materials

solution. Coatings were obtained at 0.042 mA/cm2

min from solutions S (0.2 M NaCl + 0.65 M NiSO4⋅6H2O + 0.75 M NiCl2⋅6H2O + 0.1 M H3BO3 + 0.1 M H3PO3) + 0.084

Figure. 7 shows the variation of the SiC content in the coating matrix as a function of SiC concentration in the electrolytic bath. With an increase in SiC concentration in the solution, the concentration of SiC dispersed in the obtained coating increases until a maximum value of 0.6 at.% is reached when a solution with a SiC concentration of 0.015 g/mL is used. With higher

**Figure 7.** Change in the SiC concentration in the Ni-P-SiC coating matrix as a function of the SiC concentration in the

, *t* = 10 min.

, *t* = 10

To understand the wear mechanism of the electrodeposited Ni-P-SiC composite coatings, the wear track patterns were studied by SEM. As shown in Figure 10, there were many adhesive tearing and plough lines in the sliding direction. Compared to the other Ni-P-SiC coatings, the coating with 0.52 at.% SiC (Figure 10e) exhibited the narrowest and shallowest plough lines. These findings indicated that the coating with 0.52 at.% SiC had the best wear resistance.

**Figure 9.** Hardness of the electrodeposited Ni-P-SiC coatings depending on the concentration of SiC in the metallic ma‐ trix.

**Figure 10.** SEM images of wear track of Ni-P-SiC coatings, with different SiC at.% after sliding against AISI 8620 ball in air: (a) 0.0, (b) 0.13, (c) 0.24, (d) 0.46, (e) 0.52, (f) 0.60 at.% SiC.

Figure 11 shows the curves of the wear volume of the electrodeposited Ni-P-SiC coatings as a function of the content of SiC in the metal matrix. The presence of SiC in the metallic matrix of the coating decreases volume wear. The lowest wear volume value was obtained when the SiC concentration in the metallic matrix of the Ni-P-SiC coating was 0.52 at.%. Wear volume values for the other tested concentrations were in the range of 150 to 200 μm3 N-1m-1.

**Figure 11.** The wear volume of the Ni-P-SiC coatings as a function of the content of SiC in the metal matrix.

#### *3.2.5. Friction coefficients*

**Figure 10.** SEM images of wear track of Ni-P-SiC coatings, with different SiC at.% after sliding against AISI 8620 ball in

**Figure 9.** Hardness of the electrodeposited Ni-P-SiC coatings depending on the concentration of SiC in the metallic ma‐

Figure 11 shows the curves of the wear volume of the electrodeposited Ni-P-SiC coatings as a function of the content of SiC in the metal matrix. The presence of SiC in the metallic matrix of the coating decreases volume wear. The lowest wear volume value was obtained when the SiC concentration in the metallic matrix of the Ni-P-SiC coating was 0.52 at.%. Wear volume

N-1m-1.

values for the other tested concentrations were in the range of 150 to 200 μm3

air: (a) 0.0, (b) 0.13, (c) 0.24, (d) 0.46, (e) 0.52, (f) 0.60 at.% SiC.

trix.

132 Electrodeposition of Composite Materials

Figure 12 shows the behavior of the values of the friction coefficients of the Ni-P-SiC coatings obtained. After 5000 cycles, the coating Ni-P-SiC with 0.6 at.% had the lowest value of friction coefficient (0.12 μ), which is similar to the value measured for a hard Cr coating (0.11 μ).

**Figure 12.** Variation of friction coefficient values as a function of the SiC (at.%) concentration in Ni-P-SiC composite coatings.
