Evaluation of 316L Stainless Steel Part Fabrication Using Additive and Subtractive Manufacturing: A Guideline for Process Selection

Abstract

Due to its favorable mechanical properties and high corrosion resistance and high carbon content, Stainless steel 316L is widely used in many applications including marine, biomedical and aerospace industries. With additive manufacturing technologies for metallic parts have now reached a critical acceptance level, and the interest for metal parts printing has grown significantly, the absence of a clear process versus performance/properties and cost correlations makes it necessary to have a guideline framework for process selection. Such guideline is needed in order to help investors in the industry understand the performance difference between conventional and additive means of manufacturing. Also it helps to realize the feasibility of additive manufacturing technologies for printing metal parts and when actually these technologies become worth investing in; giving the presence of better cheaper alternatives. This thesis studies the mechanical performance, cost and dimensional quality of 3D printed (using Direct Metal laser sintering) 316L stainless steel metal parts in comparison with conventional means, and accordingly develops a guideline framework for process selection by evaluating process effectiveness and investigating performance and cost. The results showed that tensile ultimate and yield strengths for CNC machined 316L Stainless steel samples are more superior to those additively manufactured samples. Furthermore, impact toughness energy resulted very poor performance for as built AM samples, and better higher energy absorption with CNC iv and heat treated AM samples. SEM images also showed unmelt particles and pores on as built AM samples. Dimensional quality of 9 model parts with various sizes and complexities fabricated has shown 50 μm in overall dimensional variation making the technology suitable for most applications (dimensional accuracy wise). Cost results showed more complex small parts are cheaper to fabricate with AM, while simple larger parts are cheaper to fabricate with CNC machining. Based on the available experimental data for mechanical and dimensional performance and cost, a process selection guideline framework was developed by process overall evaluation. The guideline can be used as tool to help in process selection for investors and industries and helps in understanding when and why metal part printing becomes more feasible and economical than conventional means.