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Materials matter: Super duplex in 3D printing explained
Published:  22 June, 2021
The past few years, super-duplex stainless steel has proved a challenge in 3D printing

Smart Machines & Factories spoke to Nikhil Dixit* to explore the potential benefits of using super-duplex stainless steel in additive manufacturing (AM).

While the interest of using iron-based and highly corrosion resistant materials in additive manufacturing has grown significantly the past few years, super-duplex stainless steel has proved a challenge in 3D printing. With its reliable characteristics and inherited suitability for corrosive environments, Sandvik’s super duplex is durable, corrosion resistant – and sworn by engineers across the offshore industry.

The recent announcement of Sandvik and part-subsidiary BEAMIT’s ability to additively manufacture super duplex has been a long time coming – as many have tried and failed to obtain the combination’s substantial benefits in terms of application performance and business optimisation.

Nikhil Dixit is an application engineer at Sandvik Additive Manufacturing and focuses specifically on Powder Bed Fusion (PBF) processes in AM. In terms of super duplex, Dixit has been heavily involved in the development of process parameters and the material qualification for our laser PBF.

Can you tell us about the process leading up to the point of Sandvik presenting the ability to successfully print super-duplex stainless steel to the market?

First of all, the suitability of super duplex in corrosive environments is already well known. Being a duplex materials authority, it made sense for us to leverage our profound experience and expertise to elevate the use of super-duplex stainless steel to the next level. I also want to stress that using super duplex in additive manufacturing is one thing – and printing it with great outcome is something entirely different. Thanks to Sandvik having been at the forefront of the duplex materials evolution for so long, we could leverage this unique position, and combine it with the additive know-how found within Sandvik and the BEAMIT Group, allowing for our joint capabilities to push this innovation through.

What kind of results have you seen in the printed super-duplex components, and how do they differ from those of conventionally manufactured parts?

Well, there’s more to additive manufacturing than printing alone. We take pride in using and manifesting our “Plan it, Print it, Perfect it” approach, stating that printing is just one of the seven steps you need to master in order to succeed in the industrialization of additive manufacturing. This philosophy, if you will, has been ever present in this process. Using premium raw materials is essential in order to obtain a high-quality, printed component and the super-duplex metal powder produced and optimised for 3D printing within Sandvik, definitely stands out in terms of powder characteristics and low oxygen levels. In terms of tensile impact and corrosion properties, additively manufactured super-duplex stainless steel doesn’t just meet the performance of conventionally manufactured components, but actually exceeds them. We have observed components that are near fully dense (>99.9%) and crack free – even before post processing.

We’ve already established super-duplex as a durable and corrosion resistant material. What does it take to optimise it for additive manufacturing, without compromising its highly valued properties

Again, it all comes down to the quality of your raw material – i.e. the super duplex metal powder. Since we atomise these powders in-house, we have the ability to control the full value chain, from raw material sourcing, to finished component. Every result is based on controlling the details, and from the get-go in our state-of-the-art powder plant, through the extensive additive machine park and post processing, we leave no stone unturned in order to safeguard the quality, continuity, and traceability along the additive value chain.

How would you describe the potential related to additively manufactured super-duplex, other than those of the material itself?

The industries where super-duplex stainless steel is the material of choice are also positioned to enjoy the benefits of implementing additive manufacturing. AM is seen as a disruptive technology across a variety of business segments, enabling revolutionary levels of performance optimization, reduced material waste and environmental impact, as well as on-demand production – just to name a few. In the offshore industries specifically, I would say the implementation of 3D printed super duplex, including on-demand production of spare parts, decreased stock keeping, and timely deliveries, could have a revolutionary impact on profitability and performance alike.

So, from the launch of this game-changing ability… Where do we go from here?

We are very excited to partner up and get down to business with customers across various offshore segments, to experience this in full effect. Apart from that, together with BEAMIT, we are already hard at work to develop print parameters for multiple-laser machines, in order to expand our offering to include even larger applications – which will allow for even more customers to implement AM into their operations. Acting on this rapidly expanding market, and in such an innovative environment, I feel confident to say this is only the beginning.

*Nikhil Dixit is application engineer at Sandvik Additive Manufacturing

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