THE EFFECT OF PROCESSING PARAMETERS ON SURFACE FINISH OF HASTELLOY X PRODUCED BY SELECTIVE LASER MELTING

Selective laser melting (SLM) technology is an additive manufacturing method in which metallic powder is selectively melted to build 3D components in a layer-wise fashion. This process is increasingly employed in the production of aerospace, automotive and medical components. Despite significant progress in terms of material flexibility and mechanical performance, poor surface quality presents a major limitation to the widespread use of selective laser melting (SLM) technology. In this study, systematic research has been carried out to study the influences of different processing parameters (e.g. laser power, scan speed, hatch distance and inclination angles) and scanning strategies (e.g. number, type and sequence of contour scans) on surface roughness of SLMed Hastelloy X alloy and samples used were manufactured using EOSM280 SLM machine. Processing window is proposed which would provide support to identify appropriate processing conditions and meet specific demand. An optimum condition for achieving the lowest roughness for up-skin (slope angle<90^o) and down-skin surface (slope angle>90^o) has been obtained, respectively. Surface characterisations revealed that melt pool shape and the presence of partially melted particles are vital factors in determining the surface profile and resultant roughness in the final parts. Computer simulation was also used to investigate the heat conduction through powder (low thermal-conductivity) and solid (high thermal-conductivity) and their contributions to the roughness on these two types of surfaces. The simulated result has been found to be consistent with the measured. By understanding the surface roughness formation mechanism, optimal surface roughness of manufactured components can be achieved.