Benefits of PEO coatings on Additively Manufactured Magnesium

Anutsek Sharma1, Joerg Zerrer1, Anna Buling1*

1 ELB - Eloxalwerk Ludwigsburg Helmut Zerrer GmbH, Neckartalstrasse 33, DE-71642 Ludwigsburg – Neckarweihingen, Germany,

*buling@ceranod.de

Magnesium (Mg) and its alloys are one of the most promising materials in the field of structural lightweight applications. This can be attributed to their high strength to density ratio which can result in significant weight reduction and increased efficiency. However, with these unique possibilities, Magnesium is also highly corrosive in nature, tends to oxidize quickly and this, in turn, limits its applications. Hence, developing magnesium parts to be used in various environments, exploring its novel applications is extremely challenging and turns out to be unique milestone to be achieved in the field of lightweight materials.

In order to enhance the range of applications and precision in produced parts, Powder Bed Fusion- Laser Beam (PBF-LB) technology is used for producing Magnesium 3D printed components. Additive manufacturing has already resulted in highly dense alloyed Magnesium parts with density as high as 99%. With additive manufacturing, there is a possibility of manufacturing precise components with complex geometries which could not only result in material saving but also in energy efficiency.

An effort to solve the corrosion problem associated with Magnesium by using PEO (Plasma-Electrolytical Oxidation) coating is done in the current work. PEO is an environment friendly process, which is applicable to additively produced Magnesium substrates; providing not only corrosion but also wear resistance and allows mechanical deformation of substrate without damage to the coating. This unique property of PEO coatings combined with additively produced Magnesium components will be thoroughly examined in this work.

The CAMM project is a joint venture of Laserzentrum Hannover (LZH) and ELB, focused on investigating the combination of optimal process parameters of PBF-LB process in combination with PEO process, which can be adopted to any application.

The here presented work is focused on exploring the surface properties of the 3D printed Mg samples, enriched with PEO process. The exactly fitting parameters in PEO process significantly help in achieving optimum layer thickness and enhanced surface properties. Extensive tribological investigations are performed on the coated and uncoated samples with the help of Pin on Disc followed by microhardness testing to examine and compare the difference in mechanical properties. Initial tribological investigations have revealed very promising outcomes with approximately 1000x decrement in wear volume of coated samples than in uncoated samples. Tribological investigations are performed with various counter body materials so as to explore the potentials for a wide range of applications. Electrochemical tests are also performed in order to examine the corrosion protection. Resulting microstructure and corrosion sites are investigated with the help of SEM.