Abstract:
The corrosion behaviour of the laser coatings was investigated in 3.65 % sodium chloride
solutions at 30o
C via potentiodynamic polarization technique. The composition of Zn50Ni-5Fe at parameters 900 W and 1.2 m/min exhibited enhanced electrochemical
performance in 3.65wt.% NaCl solution. Microstructures with unique characteristics and
refinement of grain size were observed. The fast solidification of the coating is accounted
for this unique features. In terms of corrosion performance, results revealed that increasing
the laser scanning speed was beneficial to the property, showing that the corrosion
performance became better at higher scanning speeds. At the set laser intensity of 900 W
and increased laser velocity, Zn-50Ni-5Fe coatings showed enhanced microstructure. The
multiple tracks applied in the direct laser metal deposition (DLMD) process had resulting
fields of residual stresses which attributed to the solid-state phase transformation that was
a repeated process. The study validated the reliability of optimizing DMLD set parameters
for metallurgical and mechanical considerations. These bring improvements in coatings
which were laser cladded in terms of their corrosion performance and the dimensional
accuracy, by optimizing the processing parameters. The only processing parameters which
were varied was the laser intensity and the scanning speed, which were employed to
numerically design the DLMD experiment. An empirical method was also developed and
was used to validate the results achieved experimentally. The Grey relational model (GRM)
used in this research described vividly the influence of optimized factors on the improved
corrosion resistance and compared reasonably with the experimental results. In addition,
the proposed model has the potential to provide induced corrosion rate predictions of
coatings fabrication that are additively manufactured.
