Experimental investigation on the strength and stiffness of 3D printed stainless steel S/S-316L parts

Abstract

Additive Manufacturing (AM) has been gaining a lot of interest in industrial companies, as it is able to produce complex parts with ease. There is currently much research on the industrial applicability of AM parts. One such method, Direct Energy Deposition (DED) is known to produce complex three-Dimensional (3D) geometries via telescopic lasering. However, the vast number of permutations of methods and materials means that the knowledge of industrial applicability for many combinations is lacking. This project aims to examine the mechanical properties, i.e. strength and stiffness, of 316L stainless steel parts printed via DED to determine their industrial viability. Further study is also conducted on microstructure. For this task, a total of eight 316L stainless steel specimens (four tensile, four fatigue) were created to American Society for Testing Material (ASTM)’s dimensioning standards using a DED machine. The material properties of the specimens were tested using 3 standard forms of testing - fatigue testing, tensile testing, Rockwell Hardness testing. The data was then tabulated and analysed. Non-destructive testing which involves Ultrasonic testing and Scanning Electron Microscopy (SEM) was used to evaluate the microstructure of the parts and no visible, significant defects were found. When compared to Conventionally Manufactured (CM) specimens, DED specimens were found to have lower fatigue life cycle, Ultimate Tensile Strength (UTS), stiffness and ductility. Conversely, DED specimens have higher hardness and strength than CM. The DED specimens were also compared to specimens created using Selective Laser Melting (SLM). The SLM specimens had higher UTS, hardness and stiffness, whereas, DED had higher ductility and strength when compared to SLM.