Abstract
The effect of laser power on the resulting
microstructure and microhardness of laser metal
deposited Ti6Al4V powder on Ti6Al4V substrate has
been investigated. The tracks were deposited using 99.6
% pure Ti6Al4V powder of particle size ranging
between 150 - 200 μm on 99.6% Ti6Al4V substrate. The
laser power was varied between 0.8 - 3.0 kW while the
scanning speed, powder flow rate and the gas flow rate
were kept at the values of 0.005 m/sec, 1.44 g/min and 4 l
/min respectively. The microstructure and the
microhardness were studied using the optical microscope
and the Vickers hardness tester respectively. Layer band
or macroscopic banding was observed in all the samples
which is phenomenon as it was only reported in the
literature for multi-layer deposits. The literature
attributed re-melting of the previous layers by the
succeeding layers as being responsible for their
formation. This study has revealed that this band could
be as a result of shrinkage happening in the fusion zone
as a result of the interaction of the deposited powder and
the melt pool created by the substrate material. This
study also reveals the relationship between the
microstructure, the average microhardness and the laser
power which are comprehensively discussed. The higher
the laser power, the lower the density of columnar prior
beta grain structure. Also the average microhardness
increases as the laser power increases.