INVESTIGATION OF RHEOLOGICAL PROPERTIES OF STAINLESS-STEEL POWDER AND MECHANICAL PERFORMANCES OF SLM PRINTED PARTS.

Abstract

This study focuses on the rheological properties of the atomized stainless-steel powder and the mechanical performances of the specimens obtained by selective laser melting (SLM). Rheological properties of atomized stainless-steel powders provided by two suppliers were characterized using the FT4 Rheometer, scanning electron microscopy (SEM), Hall flowmeter, Tap density measurer, and the Mastersizer 3000. The mechanical performance of the SLM printed specimens was investigated with the help of tensile, fatigue, hardness, and corrosion tests. This study provides a characterization of the influence of the build orientation and heat treatment on mechanical properties of SLM printed parts. Additionally, a literature review was prepared for the current state of research on each of the relevant properties of SLM printed 316L stainless steel parts. These comprehensive quantitative and qualitative analyses are beneficial to anticipate the failure conditions of stainless-steel specimens. From the rheological analysis, it was observed that the atomized powder provided by supplier 1 had better flowability and rheological properties. However, it was found that both commercial powders were deemed free-flowing and sufficiently appropriate for 3D printing, which is why a mixture of both was used in this study. Build orientation was found to have an effect on fatigue, hardness, and corrosion properties, while tensile performance was not significantly affected. Additionally, SEM imaging revealed a presence of defects, such as lack of fusion, voids, and unmelted powder particles in as-built specimens. Heat treatment proved to mitigate the number of defects present, leading to noticeable improvements in the properties of SLM printed parts. However, a negative effect was noted for the corrosion resistance, stemming from the increase of the number of grain boundaries, which are most susceptible to corrosion.