Influence of the Energy Density for Selective Laser Melting on the Microstructure and Mechanical Properties of Stainless Steel

Črtomir Donik,Irena Paulin,Matjaž Godec,Jakob Kraner

doi:10.3390/met10070919

Črtomir Donik, Irena Paulin + Show 2 more

Open Access

https://doi.org/10.3390/met10070919

Copy DOI

Journal: Metals	Publication Date: Jul 9, 2020
Citations: 40	License type: CC BY 4.0

Affiliation: Institute of Metals and Technology

Abstract

We have investigated the impact of the process parameters for the selective laser melting (SLM) of the stainless steel AISI 316L on its microstructure and mechanical properties. Properly selected SLM process parameters produce tailored material properties, by varying the laser’s power, scanning speed and beam diameter. We produced and systematically studied a matrix of samples with different porosities, microstructures, textures and mechanical properties. We identified a combination of process parameters that resulted in materials with tensile strengths up to 711 MPa, yield strengths up to 604 MPa and an elongation up to 31%, while the highest achieved hardness was 227 HV10. The correlation between the average single-cell diameter in the hierarchical structure and the laser’s input energy is systematically studied, discussed and explained. The same energy density with different SLM process parameters result in different material properties. The higher energy density of the SLM produces larger cellular structures and crystal grains. A different energy density produces different textures with only one predominant texture component, which was revealed by electron-backscatter diffraction. Furthermore, three possible explanations for the origin of the dislocations are proposed.

Highlights

Selective laser melting (SLM) is one of the most commonly used additive manufacturing (AM)processes used to obtain products with superior properties
Based on all of these findings, we propose an explanation for the origin of the dislocations during the SLM process
Low-magnification micrographs obtained with the light microscopy (LM) were used to determine the porosity, which was the basis for establishing the process windows

Summary

Introduction

Selective laser melting (SLM) is one of the most commonly used additive manufacturing (AM)processes used to obtain products with superior properties. AISI 316L is an extensively studied metallic material in SLM research [6,7], due to the simplicity of its single-phase (γFe -austenite) microstructure [8,9]. Despite AISI 316L’s single-phase microstructure, the SLM working parameters greatly influence the microstructure’s development. The process windows (known as process maps) that define the optimum working parameters for stable melting [13] include the laser power (P), scanning speed (v) and hatch spacing (h). Controlling these parameters results in a lower porosity and fewer defects [14], which impact the component’s density [15], mechanical and corrosion properties [16,17].

Methods

Results

Conclusion