Influences of processing parameters on surface roughness of Hastelloy X produced by selective laser melting

Selective laser melting (SLM) technology is a layer-wise powder-based additive manufacturing method capable of building 3D components from their CAD models. This approach offers enormous benefits for generating objects with geometrical complexity. However, due to the layer-wise nature of the process, surface roughness is formed between layers, thus influenced by layer thickness and other processing parameters. In this study, systematic research has been carried out to study the influence of processing parameters on surface roughness in Hastelloy X alloy. All samples were manufactured using an EOSINT M 280 machine. Laser power, scan speed, layer thickness and sloping angle of a surface were systematically varied to understand their effects on surface roughness. The arithmetic average roughness, Ra, was measured using a surface roughness tester, and optimum conditions for achieving the lowest roughness for both up-skin surfaces and down-skin surfaces have been obtained. The formation mechanism for the roughness on these two types of surfaces has been studied. Computer simulation was also used to understand thermal profiles at those two surfaces and their resultant influence on surface roughness. The simulated result has been found to be consistent with the measured result. Contour scan and skywriting scan strategies were found to be helpful for reducing the surface roughness.