Laser Processing
The samples were prepared by melting the HEA powder onto a mild steel
base plate using a 3 kW continuous wave ytterbium laser system (YLS),
with a fitted robotic arm that moves in a multi-axial direction to
control the process and a schematic representation of the laser-material
deposition process is shown in Figure 1. The HEAs powder was delivered
through a nozzle filled with argon as a carrier gas and fitted on the
laser delivery head. To prevent time lag between the molten pool and the
coating powder, the powder feeder was switched on for 5 s before the
deposition starts. The whole process considers the heat transferred to
the molten pool of the alloys. The rate of heat transfer to the molten
pool \(\dot{q}\)in per time is given by Eq. (3):
\(\dot{\text{\ \ \ \ \ }q}\)in\(=\alpha_{\lambda}Q_{\text{laser}}\)\(\left(3\right)\)
Where \(Q_{\text{laser}}\)the laser power in Watts (W)
and\(\text{\ α}_{\lambda}\)is the laser wavelength
absorptivity. The coatings were synthesized by keeping
the beam diameter and powder feed rate constant at 2 mm and 2 rpm
respectively while the laser power and scanning speed varied from
600-1600 W at 4-12 mm/s each with a 50 % overlap. The samples were
prepared at a pre-heat temperature of 400 °C.