Session: MF-17-02 Advanced and Additive Manufacturing and Material Technologies (joint with D&A)

Paper Number: 84543

84543 - The Mechanical Performance of Additively Manufactured 316l Austenitic Stainless Steel 

Abstract

Additive manufacturing (AM) offers the potential for significantly reducing the time and cost of new nuclear components. This process may also permit unique design features, for example internal geometries. However, the limitations of the technology need to be better understood to enable implementation and accreditation.

Here a “blown powder” and laser melting process, within a helium shielded environment, was used to fabricate austenitic stainless steel 316L walls of ~2.4 mm thickness, with the deposition parameters minimizing the surface roughness.

A key aim was to evaluate the effect of the as-deposited surface finish and the bulk material on the tensile and fatigue properties. In addition, the effect of material orientation was also considered to be important.

Microstructural characterization demonstrated the complex nature of the grain morphology arising from the as-manufactured AM process, including elongated grains following the thermal gradients. However, areas of equiaxed grains were also observed at the sample surfaces. Si-Mn-O particles, up to ~20 µm in diameter, were noted throughout the samples produced. Residual strains have also been measured and correlated with microstructural features.

The tensile performance was generally similar to wrought 316L material but exhibited some anisotropy. The fatigue endurance of as-deposited AM 316L was significantly lower than wrought material. However, surface grinding of the AM 316L was shown to be beneficial. It was noted that in all cases examined, fatigue crack initiation was found to occur at the Si-Mn-O particles, in both surface finishes – clearly a performance limitation.

 

Keywords: additive manufacturing, austenitic stainless steel, fatigue, tensile.

Presenting Author: Andrew Wisbey Jacobs

Presenting Author Biography: Andrew Wisbey has over 12 years experience in the mechanical performance of nuclear structural materials, mainly in support of the plant life extension of the current UK fleet of Advanced Gas-cooled Reactors (AGRs). However, latterly Andrew has been engaged in the evaluation of materials and manufacturing technologies for advanced reactor systems. Prior to this he has 19 years experience in the aerospace industry, engaged in the research and development of manufacturing technologies and also the structural integrity of gas turbines.<br/><br/>For the past few years, Andrew has been the UK representative on the international Gen IV Forum (GIF) Very High Temperature Reactor (VHTR) Materials board.

Authors:

Andrew Wisbey Jacobs
David Coon Jacobs
Mark Chatterton Jacobs
Joshua Barras TWI
Da Guo The University of Manchester
Kun Yan The University of Manchester
Mark Callaghan Jacobs
Wajira Mirihanage The University of Manchester