Additive manufacturing through selective laser melting and directed energy deposition of 316L stainless steel: effect of process parameters on mechanical properties

• Grant number: 19/01829-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Effective date (Start): May 01, 2019
• Effective date (End): May 07, 2023
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Physical Metallurgy
• Principal Investigator: Piter Gargarella
• Grantee: Gustavo Figueira
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated research grant: 16/11309-0 - The study, development and application of a hybrid process: Additive Manufacturing (AM) plus High Speed Machining/Grinding (HSM/G), AP.TEM

Abstract

The manufacturing processes where the product is obtained layer by layer are called Additive Manufacturing (AM) processes. Among the AM processes for metallic materials, the Selective LASER Melting (SLM) may be highlighted, in which a LASER beam melts locally regions of a powder bed previously deposited. There are several parameters to control those processes, such as raw materials' properties, beam power, scanning speed and strategy, hatching and building direction. Any variation of those parameters can induce microstructural changes and modify the product properties, mainly the mechanical properties that are sensibly affected by the way the product is built. Among the most studied and accepted materials for those processes, one can find the 316L stainless steel. This steel generally forms a dendritic-like austenitic microstructure by conventional processes, but it has been observed the formation of a cellular biphasic (austenite and ferrite) microstructure for some AM processes. The 316L steel is widely used in furnace components, heat exchangers, jet engines, evaporators and other equipment for chemical, pharmaceutical and naval industries. Although this steel has been known by its noteworthy corrosion resistance, some industrial applications require a higher electrochemical response and a high wear resistance. The addition of boron to the stainless steel is a possible answer in order to obtain a higher wear resistance by the formation of hard borides such as M2B ou M3B2. However, the formation of such borides reduces the content of alloying elements which are responsible for conferring the high corrosion resistance to the alloy, such as Cr, Ni and Mo. Considering this scenario, the aim of the present project is to realize a systematic evaluation of the boron addition in the 316L stainless steel manufactured by SLM e its effects on the tribological and electrochemical properties of the alloy. Samples will be manufactured with different process parameters (beam power, scanning speed, and hatch spacing) using a commercial powder in order to evaluate the process parameters which lead to samples with high density. Samples will have their microstructure characterized through X-Rays Diffraction (XRD), Optical Microscopy (OM) and Scanning (SEM) Electron Microscopy, and chemical analysis by Energy-Dispersive X-Ray Spectroscopy (EDS). Once the samples are characterized, a set of process parameters which result in samples with low porosity will be selected. The 316L stainless steel will then be modified with small additions of boron, evaluating the possible phase formation through the ThermoCalc software and confirming the results by copper suction casting. After adjusting the chemical composition of the alloy aiming for the best results, the original and the modified alloys will be gas atomized to produce metallic powder. Samples for wear and corrosion tests will be manufactured by SLM with the process parameters initially selected, and the obtained results will be correlated with the respective microstructures. (AU)

Scientific publications

(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)

RODRIGUES, L. C. M.; KOGA, G. Y.; FREITAS, B. J. M.; FIGUEIRA, G.; GARGARELLA, P.; BOLFARINI, C.; KIMINAMI, C. S.; BOTTA, W. J.. Wear-resistant Fe68Cr8Mo4Nb4B16 glass former coatings-From powder production by gas atomization to coating build-up by Laser Powder Bed Fusion. SURFACE & COATINGS TECHNOLOGY, v. 441, p. 12-pg., 2022-07-15. (13/05987-8, 19/05885-7, 19/01829-5, 17/27031-4, 21/08514-0)

RICCARDO AUGUSTO MOREIRA MONTUORI; GUSTAVO FIGUEIRA; THIAGO PACAGNAN CATALDI; NELSON GUEDES DE ALCÂNTARA; CLAUDEMIRO BOLFARINI; REGINALDO TEIXEIRA COELHO; PITER GARGARELLA. Manufatura Aditiva de Aço Inoxidável 316L por Fusão Seletiva a Laser. Soldagem & Inspeção, v. 25, 2020-09-28. (18/06691-9, 16/11309-0, 18/16898-0, 19/01829-5, 17/27031-4)