Characterisation of 17-4PH metallic powder recycling to optimise the performance of the selective laser melting process

Comparative study of the microstructure between a laser beam melted 17-4PH stainless steel and its conventional counterpart

“…3b) suggested the presence of austenitic phase, even though it was not possible, with such an observation, to make a direct correlation between zones enriched with a specific element and the identification of an austenitic grain. The result should be in agreement with recent work done by Meredith et al [28] who observed a small proportion of austenite for a N 2 -atomised powder, and with work done by Zapico et al who showed that the austenite content of the powder increased with the number of cycles [27].…”

“…3a). However, some smaller powder grains were observed to be partially melted to bigger particles, as already reported by several authors [20,27,31].…”

“…Nevertheless, the possibility to have a small part of reversed austenite in the thermally affected zone due to the re-melting step could not be neglected. The austenite to martensite ratio in as-built AM samples could be related to the nature of the powder as proposed by various authors [4,6,15,[26][27][28]. In that sense, our result was in good agreement with those of Meredith et al [28] who showed that non-negligible austenite levels, reaching values as high as 81%, could be measured in the as-built parts for the N 2 -atomised powders: this was explained by considering the concentrations of austenite-stabilising elements, e.g.…”

“…This new process has aroused widespread interest https://doi.org/10.1016/j.msea.2021. 141718 A significant influence of the chemical composition and microstructure of the powder used, and of the nature of the vector gas used during the AM process, was evidenced on the resulting microstructure of 17-4PH MSS samples [4,6,15,[26][27][28]. In particular, Murr et al [6] highlighted that mostly martensitic microstructures were observed for the built parts when the AM process was performed under Ar, independently of the powder; when N 2 was used during the building process, mostly austenitic microstructures were obtained for N 2 -atomised powder, i.e.…”

Laser Defocusing Effect on the Microstructure and Defects of 17-4PH Parts Additively Manufactured by SLM at a Low Energy Input

“…The manufactured parts were separated from the build-up plate by wire electrical discharge machining (WEDM). Table 1 shows the composition of the nitrogen atomized 17-4PH powder [28,29]. The specimens named D 0 , D d1 , and D c1 were processed with the laser beam in focus, defocusing 1 mm above the focal plane (divergent beam through the powder bed) and defocusing 1 mm under the focal plane (convergent beam), respectively.…”