Characterizing Additively Manufactured Metals From a Novel Laser Wire Metal Deposition Process

Abstract

Several tests were conducted on 316 stainless steel, and 17-4 PH stainless steel to understand the effect of additive manufacturing on their mechanical properties in general. The samples were produced via a custom-built laser wire metal deposition, with variable laser power of 3600W for 316 stainless, and 4000W for 17-4 PH, but all other printing parameters were kept same. Four different tests, Tensile, Rockwell hardness, Charpy impact, and optical microscopy were carried out to establish the material properties and surface characterization. Through our assessment, it was found that the properties of the laser-printed samples can be greatly varied by printing in an inert atmosphere, while the printing orientation and post-print heat treatment process also play a dominant role in determining the properties. This research showed that the properties of additively manufactured 316 stainless, and 17-4 PH have fared well when compared to ASTM standard values for annealed metals. Details of the results are presented. Inspecting the 316 stainless, the metal strength and hardness were high while being printed in x orientation, while the metal was much more ductile when printed in y orientation. The 316 stainless micro-structure contained no porosity or no anomalies from the samples tested. The results of 17-4 stainless samples matched the ASTM standard values for strength and hardness. But with Charpy impact tests, the results seemed slightly ductile as the values were slightly lower than the threshold. That brittle nature could have been a result of porosity that was visible under microscope. But the porosity levels decreased tremendously when the sample was once again printed in an inert environment. The results of this research have helped us understand the intricate nature of 316 and 17-4 PH stainless steels while being additively printed. The beneficial research experience of participating undergraduate students in collaboration with industry is a special feature of this project.