Wire Laser Metal Deposition Additive Manufacturing of Duplex Stainless Steel Components—Development of a Systematic Methodology

A systematic four-stage methodology was developed and applied to the Laser Metal Deposition with Wire (LMDw) of a duplex stainless steel (DSS) cylinder > 20 kg. In the four stages, single-bead passes, a single-bead wall, a block, and finally a cylinder were produced. This stepwise approach allowed the development of LMDw process parameters and control systems while the volume of deposited material and the geometrical complexity of components increased. The as-deposited microstructure was inhomogeneous and repetitive, consisting of highly ferritic regions with nitrides and regions with high fractions of austenite. However, there were no cracks or lack of fusion defects; there were only some small pores, and strength and toughness were comparable to those of the corresponding steel grade. A heat treatment for 1 h at 1100 °C was performed to homogenize the microstructure, remove nitrides, and balance the ferrite and austenite fractions compensating for nitrogen loss occurring during LMDw. The heat treatment increased toughness and ductility and decreased strength, but these still matched steel properties. It was concluded that implementing a systematic methodology with a stepwise increase in the deposited volume and geometrical complexity is a cost-effective way of developing additive manufacturing procedures for the production of significantly sized metallic components.

Download Full-text

Microstructure of laser metal deposited duplex stainless steel: Influence of shielding gas and heat treatment

Welding in the World ◽

10.1007/s40194-020-01036-5 ◽

2020 ◽

Author(s):

Maria Asuncion Valiente Bermejo ◽

Karthikeyan Thalavai Pandian ◽

Björn Axelsson ◽

Ebrahim Harati ◽

Agnieszka Kisielewicz ◽

...

Keyword(s):

Heat Treatment ◽

Stainless Steel ◽

Duplex Stainless Steel ◽

Nitrogen Loss ◽

Steel Wire ◽

Research Work ◽

Shielding Gas ◽

Austenite Content ◽

Heat Treated ◽

Phase Balance

AbstractThis research work is the first step in evaluating the feasibility of producing industrial components by using Laser Metal Deposition with duplex stainless steel Wire (LMDw). The influence of Ar and N2 shielding gases was investigated in terms of nitrogen loss and in the microstructure and austenite content of different deposited geometries. The evolution of the microstructure in the build-up direction of the Ar and N2-shielded blocks was compared in the heat-treated and as-deposited conditions. The susceptibility for oxygen pick-up in the LMDw deposits was also analyzed, and oxygen was found to be in the range of conventional gas-shielded weldments. Nitrogen loss occurred when Ar-shielding was used; however, the use of N2-shielding prevented nitrogen loss. Austenite content was nearly doubled by using N2-shielding instead of Ar-shielding. The heat treatment resulted in an increase of the austenite content and of the homogeneity in the microstructure regardless of the shielding gas used. The similarity in microstructure and the low spread in the phase balance for the as-deposited geometries is a sign of having achieved a stable and consistent LMDw process in order to proceed with the build-up of more complex geometries closer to industrial full-size components.

Download Full-text

Influence of Process Conditions on the Local Solidification and Microstructure During Laser Metal Deposition of an Intermetallic TiAl Alloy (GE4822)

Metallurgical and Materials Transactions A ◽

10.1007/s11661-021-06139-2 ◽

2021 ◽

Vol 52 (3) ◽

pp. 1106-1116

Author(s):

Silja-Katharina Rittinghaus ◽

Jonas Zielinski

Keyword(s):

Heat Treatment ◽

Additive Manufacturing ◽

Process Parameters ◽

Titanium Aluminides ◽

Metal Deposition ◽

Experimental Investigations ◽

Process Conditions ◽

Laser Metal Deposition ◽

Melt Pool ◽

Temperature Regimes

AbstractTemperature-time cycles are essential for the formation of microstructures and thus the mechanical properties of materials. In additive manufacturing, components undergo changing temperature regimes because of the track- and layer-wise build-up. Because of the high brittleness of titanium aluminides, preheating is used to prevent cracking. This also effects the thermal history. In the present study, local solidification conditions during the additive manufacturing process of Ti-48Al-2Cr-2Nb with laser metal deposition (LMD) are investigated by both simulation and experimental investigations. Dependencies of the build-up height, preheating temperatures, process parameters and effects on the resulting microstructure are considered, including the heat treatment. Solidification conditions are found to be dependent on the build height and thus actual preheating temperature, process parameters and location in the melt pool. Influences on both chemical composition and microstructure are observed. Resulting differences can almost be balanced through post heat treatment.

Download Full-text

Microbial-Induced Corrosion of 3D-Printed Stainless Steels: A Surface Science Investigation

Materials Proceedings ◽

10.3390/cmdwc2021-09973 ◽

2021 ◽

Vol 6 (1) ◽

pp. 9

Author(s):

Brianna L. Young ◽

Jamie S. Quinton ◽

Sarah L. Harmer

Keyword(s):

Stainless Steel ◽

Additive Manufacturing ◽

Metal Deposition ◽

Passivation Layer ◽

Manufacturing Processes ◽

Laser Metal Deposition ◽

Manufacturing Method ◽

316 Stainless Steel ◽

First Choice ◽

Corrosive Resistance

Stainless steel is a material manufactured for its high corrosive resistance and is the first choice of material in a range of applications. Microbial-induced corrosion can cause significant damage to metals and is responsible for approximately 20% of corrosive damage. The corrosive resistance of stainless steel is reduced during manufacturing processes, including welding or joining methods, as the connection points prevent the metal from reforming its passivation layer. Additive manufacturing processes allow for intricate designs to be produced without the need for welding or bolts. However, it is unknown how the layering method of additive manufacturing (AM) will affect stainless steel’s passivation layer and, in turn, its corrosive resistance. This research compares the corrosive resistance of 316L stainless steel produced using laser metal deposition and traditionally manufactured AISI 316 stainless steel to determine how the layering manufacturing method affects the corrosive resistance of the material. Samples are incubated over a 21-day period with Acidithiobacillus ferrooxidans (A.f) and Leptospirillum ferooxidans (L.f) in a modified HH medium with an approximate pH of 1.8 and kept at a constant temperature of 30 °C. Scanning electron microscopy and Auger electron spectroscopy surface analysis techniques are used to identify any corrosive processes on the surface of the samples. This research is an introductory analysis of the corrosive resistance of AM 316 stainless steel using the laser metal deposition technique. The results show how stainless steel produced using laser metal deposition will react in acidic environments and are used to determine if it could be used in conjunction with other materials in underground pipes for acidic soils.

Download Full-text