Theoretical modeling and finite element simulation of dilution in micro-plasma transferred arc additive manufacturing of metallic materials

Dilution in any additive layer manufacturing signifies fusion of a deposition layer with the substrate as well as
between the successive deposited layers. It assumes importance because it affects metallurgical bonding and properties of the deposited layers. Evaluation of dilution of a deposition by optical microscopy is more accurate but
it is destructive due to requirement of the sample preparation. Monitoring and control of the dilution is also very
difficult. Dilution can be predicted either by a theoretical model or finite element simulation (FES). This paper
presents development of a generic theoretical model and FES to predict dilution of depositions by micro-plasma
transferred arc additive manufacturing (MPTAAM) process. The model and FES predicted values were validated
by comparing them with the experimental results of single-layer single-track deposition of Ti-6Al-4V powder on
the substrate of the same material for the various parametric combinations of MPTAAM process. Results have
shown very good agreement between model and FES predicted values of dilution with the corresponding experimental values. The developed theoretical model is also generic because it depends only on the MPTAAM
process parameters and thermal properties of the deposition and substrate materials thus making it applicable
for any combination of deposition and substrate materials and for any form of the deposition material. The results
showed that dilution increases with increase in micro-plasma power and relative speed between the worktable
and deposition head whereas decreases with increase in volumetric feed rate of the deposition material.