Design of Experiment
To achieve optimized process parameters, two stages of experiments were
carried out using design of experiment {D.O.E} approach to develop
different combinations of processing parameters as shown in Tables 3 and
4. Table 5 shows the optimized laser process parameters used in this
study as derived from the Design-Expert v11 software. The criteria for
selecting the optimized parameters were centered on homogeneity in clad
layer and defect-free microstructures using two factors namely [40,
41]; laser power (P) and scan speed (mm/s) at three levels
respectively. The optimization tests were carried out varying the laser
power from 600-1000 W at a scan speed from 4-12 mm/s for stage 1 of the
experiment and 1200-1600 W at a scan speed of 8-12 mm/s for stage 2,
while preheating the base plate at 40 °C and constant
powder feed rate of 2 rpm. .
The number of experiments is calculated by Eq. (2) [42] ;
\(N=L^{F}\) \(\left(2\right)\)
Where N is the number of experiments, F is the number of factors varied
and L is the number of level set for the experiment. The final sets of
18 parameters used are displayed in Table 5.
Table 3: Stage 1 of the experiment