**3.5. ANOVA**

**Factors Code**

198 Electrodeposition of Composite Materials

**Table 5.** Level averages for each parameter.

**Figure 6.** Mean wear rate of each parameter level.

**Figure 7.** Mean hardness of each parameter level.

**Parameter levels(wear resistance test) × 10−7**

Current density 8.84 5.89 0 301.2 287 0 RPM A 8.12 7.73 6.25 255.3 339.5 287.6 pH B 7.55 5.88 8.67 260.3 306.2 264.8 Al2O3 concentration C 8.68 8.65 4.77 294.5 261.9 325.9 Bath temperature D 8.47 6.45 7.18 298.1 310.8 273.5

**1 2 3 1 2 3**

**Hardness HV0.2 kg**

The ANOVA separates the total variability of the response into percentage contribution (P) of each parameter. The higher the percentage contribution, the more important the parameter is to the wear resistance and hardness of the coating. Table 6 shows the ANOVA calculated values and indicates that the greatest contributing factor for wear was the Al2O3 particle concentration at 51.68% followed by bath temperature with a contribution of 32.41%, whereas bath pH and stir rate had the lowest impact on the wear resistance of the coating.


**Table 6.** ANOVA for wear.

#### **3.6. Selection of the optimum parameters**

To select the optimum parameter settings for improved wear resistance, the "smaller-is-better" characteristics were used to select the optimized parameter level, which are shown in Table 7. Table 7 indicates one conflict in the recommended optimized levels: factor A (stir rate). Analysis of the results for both S/N ratio averages and the level averages revealed that the stir rate greater than 630 rpm would result in minimum output; however, analysis of the levelaveraged wear rate indicated that a setting at level 2 would be more appropriate. The results suggest that within the parameter levels tested, pH and stir rate had the least effect on the wear rate.


**Table 7.** Summary of the factor analysis.

#### **3.7. Confirmation test**

Experimental validation of the Taguchi optimization process was necessary to confirm that the minimum wear rate can be achieved using the optimum coating parameters. A conforma‐ ptimization p

process. Tw

o wear rate v

from the op

tional experiment was conducted with the levels of the process parameters (A3, B2, C3, and D2), resulting from the optimization process. Two wear rate values were obtained (4.4E-07 kg/ s and 4.1E-07 kg/s), and the average of these values was found to be 4.25E-07 kg/s with an average hardness of 501.5 HV. and the ave An SEM m of surface d erage of thes micrograph o defects and i se values wa of the optimi interfacial v as found to b zed Ni/Al2O oids; howev be 4.25E-07 k O3 coating as ver, agglome kg/s with an s shown in Fi erate Al2O3 p n average har igure 8(a) re particles wer rdness of 50 evealed the a re present in 1.5 HV. absence the

he process p

arameters (A

A3, B2, C3, a

and D2), res

sulting

7 kg/s),

and 4.1E-07

ed samples.

.4E-07 kg/s

obtained (4.

values were

An SEM micrograph of the optimized Ni/Al2O3 coating as shown in Figure 8(a) revealed the absence of surface defects and interfacial voids; however, agglomerate Al2O3 particles were present in the coating. coating.

F igure 8. (a) S Surface of N Ni/Al2O3 coat ting and (b) XRD spectr rum of coate **Figure 8.** (a) Surface of Ni/Al2O3 coating and (b) XRD spectrum of coated samples.
