Scanning
speed is one of the critical process parameter in laser engineered net
shaping. For 304 stainless steel, Chai R, et al. studied, smooth laser
cladding surfaces with modest track widths/heights are produced at scan
speeds ranging from 4 to 16 mm/s. If the scan speed is too slow, the
material is exposed to the laser for a longer period of time, generating
more heat and expanding the heat affected zone. The metal will not melt
if the scan speed is too fast. Depending on the properties of the powder
material being used, the scan speed should be chosen to be within or
near the specified scan speed range. As shown in Fig. 3(b), scanning
speed has also a negative effect on the surface roughness.
(b)
Deposition Pattern
Xinlin W. et al. were investigated the effect of scanning parameter
(reciprocating and unidirectional deposition way) and z-increment on
overhang structure and accuracy in 3-axis LENS process. In
unidirectional deposition, the deposited overhang had uneven surfaces
and voids on the left side (end side of the path). The surface of the
overhang through the round-trip deposition path was flat and symmetrical
compared to the unidirectional path. The z-increment had a significant
effect on the angular accuracy of the deposited overhang. By optimizing
the z-increment, the discrepancy between the designed overhang tilt
angle and his experimental overhang tilt angle was greatly reduced. The
optimal z increment value depends on various process parameters (laser
power, scan speed, and powder feed rate).
Layer Thickness
Ronda N. et al. studied on M300 maraging steel parts the effect of layer
thickness on the microstructure, metallurgical quality and mechanical
properties . Microscopic observation of the structure of the samples
unconcealed a fine cellular structure. It had been noted that a decrease
within the layer thickness leads to a decrease within the cell size and
at the same time lowers the porosity of the fabric. A rise within the
layer thickness causes a little however noticeable deterioration of the
fabric properties between the 0.5 and 0.75 metric linear unit layer
thicknesses. While producing ceramic components, cracking is the main
challenge. Crack range of made-up specimens decreases clearly with the
rise of layer thickness, and crack direction step by step changes from
horizontal direction to transverse direction. Once the layer thickness
is zero.8mm and on top of, close to crack-free structures are often
obtained. Total energy consumption for every ceramic specimen deceases
clearly with increasing of layer thickness, that is helpful to reduce
the strain and therefore scale back the cracking behavior. Porosity
increased as layer thickness increased.