Interfacial phenomena and characteristics between the deposited material and substrate in selective laser melting Inconel 625

Selective laser melting (SLM) is widely used to process InConel 625 alloy powders to manufacture functional components. The SLM process parameters significantly affect the bonding of melting powders and the substrate or deposited layer, the geometry of melt pool, and the microstructure of end-use components. In this study, single track SLM experiments were carried out to investigate the melt pool geometry on a lab-made facility with a wide range of laser power and scan speed and the fixed laser beam diameter and layer thickness. A process map for SLM of Inconel 625 alloy was developed. Four types of single track formation have been identified and characterized. The contact angle of the melt pool tends to decrease with the increase of laser power. The track height, surface roughness, and contact angle were found to be independent of scan speed. Surface integrity of the tracks was also analyzed in terms of surface roughness, microstructure, grain size, and microhardness. In addition, the influence of process parameters on the microstructure in the tracks was investigated. A typical columnar dendrite microstructure was observed in the tracks due to the rapid cooling process. At high laser powers, larger primary dendritic arm spacing was formed in the tracks, which has higher hardness than that of the heat affected zone (HAZ). (C) 2016 Elsevier B.V. All rights reserved.