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

Abstract

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. © 2019 Elsevier Ltd