Dissolvable metal support enables Additive Manufacturing of complex metallic structures

News
July 13, 2016

July 13, 2016

Dissolvable metal support enables Additive Manufacturing of complex metallic structures

Researchers in America have fabricated dissolvable carbon steel structures using 3D printing technology that can provide temporary support for components of larger stainless steel structures made by Additive Manufacturing. Published in the journal 3D Printing and Additive Manufacturing, the article “Dissolvable Metal Supports for 3D Direct Metal Printing” demonstrates an application of this novel approach, in which the researchers printed and later dissolved a metal structure to support a 90° overhang.

Co-authors Owen Hildreth, Arizona State University (Tempe), Abdalla Nassar and Timothy Simpson, Pennsylvania State University (State College, PA), and Kevin Chasse, Naval Surface Warfare Center (W. Bethesda, MD), propose that this technique could dramatically reduce the amount of post-processing needed for metal AM components to remove support structures.

Dissolvable metal support enables Additive Manufacturing of complex metallic structures

Images of the sample taken before, during, and after etching. (a) Before etching, the red square roughly outlines where the carbon steel support layer was printed. (b) After 10 h of etching 1.4 mm of carbon steel was removed from each side. (c) After etching showing that the carbon steel was completely etched from the sample. (d) Images of sidewall and bottom with lines etched into a chromium-depleted layer of the component and stainless steel baseplate, where the carbon steel leeched the chromium during printing

Unlike polymer AM processes, soluble sacrificial support materials have not been identified and characterised for metallic materials and, as a result, support structures in metal Additive Manufacturing must be removed using additional machining operations. In this study, the authors demonstrated that sacrificial metal supports can be fabricated by taking advantage of differences in the chemical and electrochemical stability between different metals.

A stainless steel bridged structure with a 90° overhang was fabricated using a carbon steel sacrificial support that was later removed through electrochemical etching in 41 wt.% nitric acid with bubbling oxygen. Open circuit potentials and potentiodynamic polarisation curves were gathered to verify etch selectivity. No machining, grinding, or finishing operations were required to remove the metallic supports using this approach.

Fig. 2 shows the sample before, during, and after etching. In Fig. 2a, a red square roughly outlines the carbon steel section. Figure 2b shows the component after 1.4mm of carbon steel was removed with 6 h of etching with no oxygen bubbling. Adding oxygen bubbles increased the etch rate dramatically, and the rest of the carbon steel was dissolved in 6 h until the stainless steel bridge was the only structure remaining (Fig. 2c).

The inset in Fig. 2d shows the impact of using two materials with dramatically different chromium content. The authors stated that it is well known that stainless steel welds on carbon steel (and vice versa) offering reduced corrosion resistance near the carbon/stainless steel interface. This local reduction in resistance is attributed to the formation of a depleted chromium layer within the stainless steel as chromium at the interface diffuses into the chromium-deficient carbon steel.

The grooves etched into the stainless steel component sidewalls and into the stainless base verify that this phenomenon occurs in bimetallic DED printed components. It is important to account for this additional etching because, even though no observable etching of the overall stainless steel component was observed, some tens of microns of stainless steel will be removed at the stainless/carbon steel interface that authors added.

This novel approach introduces new capabilities to directed energy deposition (DED) AM and could drastically reduce the post-processing needed for these types of parts. For example, a carbon steel layer could be printed, deposited, or developed onto the stainless steel base and then used as a sacrificial support layer for the entire component so that the component can be removed from the build plate without any machining operations. The authors expect this process to be applicable to a wide range of metals and even oxides through selective chemical dissolution.

http://www.liebertpub.com/3dp

News
July 13, 2016

In the latest issue of Metal AM magazine

Download PDF
 

Extensive AM industry news coverage, as well as the following exclusive deep-dive articles:

  • Metal powders in Additive Manufacturing: An exploration of sustainable production, usage and recycling
  • Inside Wayland Additive: How innovation in electron beam PBF is opening new markets for AM
  • An end-to-end production case study: Leveraging data-driven machine learning and autonomous process control in AM
  • Consolidation, competition, and the cost of certification: Insight from New York’s AM Strategies 2024
  • Scandium’s impact on the Additive Manufacturing of aluminium alloys
  • AM for medical implants: An analysis of the impact of powder reuse in Powder Bed Fusion

The world of metal AM to your inbox

Don't miss any new issue of Metal AM magazine, and get the latest industry news. Sign up to our twice weekly newsletter.

Sign up

Discover our magazine archive…

The free to access Metal Additive Manufacturing magazine archive offers unparalleled insight into the world of metal Additive Manufacturing from a commercial and technological perspective through:

  • Reports on visits to leading metal AM part manufacturers and industry suppliers
  • Articles on technology and application trends
  • Information on materials developments
  • Reviews of key technical presentations from the international conference circuit
  • International industry news

All past issues are available to download as free PDFs or view in your browser.

Browse the archive

Looking for AM machines, metal powders or part manufacturing services?

Discover suppliers of these and more in our comprehensive advertisers’ index and buyer’s guide, available in the back of Metal AM magazine.

  • AM machines
  • Process monitoring & calibration
  • Heat treatment & sintering
  • HIP systems & services
  • Pre- & post-processing technology
  • Powders, powder production and analysis
  • Part manufacturers
  • Consulting, training & market data
View online
Share via
Copy link
Powered by Social Snap