Influence of normalized enthalpy on inconel 718 morphology in direct metal deposition

Abstract

Morphology of each layer contributes to the final shape of a component fabricated by direct metal deposition process, because of the layer-on-layer fabrication technique. Hence, it's a requisite to understand the layer morphology evolution and factors affecting it. The present work deposited single tracks of Inconel 718 at systematically varied process conditions, and investigated their effect on the track/deposit geometry. The various parameters considered for the study are laser power ( P), scan speed ( v), and powder feed rate ( ṁ). The measurements carried on the deposits cross-section using optical microscope are width ( w), height ( h), and depth of penetration ( b). Additionally, dilution ( D %), deposit area, fusion zone shape and area are measured. The change in layer morphology with input parameters either individually or coupled, is also investigated. The coupled parameters are derived from the simultaneous variation of two are more individual parameters, such as linear heat input, line mass, and normalized enthalpy. The results have shown a proper relationship between input parameters and output morphology. Coupled parameters are observed to be a more valid measure in predicting the deposition geometry, than individual parameters. The relations obtained are linear between width and normalized enthalpy, height and line mass respectively. The fusion zone shape is evolving from semicircular to a wavy (double parabolic) nature with increasing energy input. The microstructure observations resulted a scenario of rapid cooling, and dendritic grain morphology.