Top surface and side roughness of Inconel 625 parts processed using selective laser melting

Abstract

Purpose – Obtaining the required part top surface roughness and side roughness is critical in some applications. Each of these part properties can often be improved to the detriment of the other during selective laser melting (SLM). The purpose of this paper is to investigate the selective laser melting of Inconel 625 using an Nd:YAG pulsed laser to produce thin wall parts with an emphasis on attaining parts with minimum top surface and side surface roughness. Design/methodology/approach – A full factorial approach was used to vary process parameters and identify a usable Inconel 625 processing region. The effects laser process parameters had on the formation of part surface roughness for multi-layer parts were examined. Processing parameters that specifically affected top surface and side roughness were identified. Findings – Higher peak powers tended to reduce top surface roughness and reduce side roughness as recoil pressures flatten out the melt pool and reduce balling formation by increasing wettability of the melt. Increased repetition rate and reduced scan speed reduced top surface roughness but increased side roughness. A compromise between attaining a relatively low surface roughness and side roughness can be attained by comparing part surface roughness values and understanding the factors that affect them. A sample with 9?µm top surface roughness and 10?µm side roughness was produced. Originality/value – The research is the first of its kind directly processing Inconel 625 using SLM and investigating processing parameters that affect top surface and side roughness simultaneously. It is a useful aid in unveiling a relationship between process parameters and top/side roughness of thin walled parts.