Microstructure of stainless steel produced by direct metal laser sintering

Abstract

Microstructure of stainless steel produced by direct metal laser sintering C. Labre1, 2, A. L. Pinto1, G. Solórzano2 1 Brazilian Center of Physics Research, Rio de Janeiro, Brazil. 2 Department of Chemical and Materials Engineering, PUC‐Rio de Janeiro, Brazil. Keywords: Additive manufacturing, direct metal laser sintering, 3D Additive manufacturing or rapid prototyping is a layer‐by‐layer fabrication technique based on selective fusing and consolidating thin layers of loose powders with a scanning laser beam, for building three‐dimensional (3D) objects [1]. Among the various methods of additive manufacturing the direct metal laser sintering (DMLS) had a big progress in the recent years and as an alternative manufacturing route to produce components, it attracted great attention due to the easy processing, high process speed and capability of producing complex shaped metallic objects. The present study focuses on the microstructural characteristics of the 15‐5 PH stainless steel powder and a component built by DMLS from the same powder (composition: Cr 16,4wt%, Ni 4wt%, Cu 3,7 wt%, Mn 1,3wt%, Si 0,045wt%, Mo 0,5wt%, Nb 0,35wt%, C 0,045wt% and Fe (bal.)). For this purpose, JEOL JSM 7100FT scanning electron microscope (SEM), LYRA3 FEG SEM and electron backscattered diffraction (EBSD) have been used at Brazilian Center of Physics Research (CBPF). Figure 1A shows that the 15‐5 PH powders are in spherical shape and the particle size are in the ranged of 20 to 50μm. Preliminary EBSD results of the slice view of Figure 1B show that the grains are randomly oriented (Figure 1C), each orientation is indicated by a specific color, and it has a higher concentration of grain size of up to 7μm (Figure 1D). Grain orientation map shows that there is not a preferential crystallographic orientation. Figure 2A shows a SEM image of the cross section of an object produced by DMLS. A laser scanning was repeated to build the subsequent layers until the objects is completed. Arrow indicates the building direction. The grain orientation map presents columnar grains randomly oriented melt pool boundaries (Figure 2B). The grain size distributions show a higher concentration of grain size below 5µm (Figure 1C). The grain size of the object is reduced comparing with the grain size of the original powder.