Metal Additive Manufacturing Conference 2018

In laser metal deposition (LMD) process, melt pool oxidation is inevitable due to its high temperature, which results in finely dispersed non-metallic inclusions in the steel matrix. These were found to strengthen the as-built AM alloy by the Orowan strengthening mechanism. Inclusion evolution in AM were also found to show strong dependency on process parameter, such as laser power, scan speed, powder chemistry and shielding gas flow rate. In this study, we systematically explore the effect of shielding gas flow rate on the mechanical property and inclusion characteristics. As shielding gas flow rate varies from 5L/min to 25L/min oxygen contents in the meltpool changed from 775ppm to 375ppm in low laser beam intensity situation and from 677ppm to 1470ppm in high laser beam intensity situation. It was found that only varying shielding gas flow rate could make a difference in tensile stress up to 90MPa.