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Researchers Reveal New Deposition Process

Wednesday, June 14, 2017

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German researchers recently unveiled a new laser deposition process that they say poses economic and environmental advantages over common alternatives.

According to Fraunhofer’s Institute for Laser Technology (ILT), researchers from ILT and Aachen University have developed an ultra-high-speed laser deposition process, which is known by its German acronym, EHLA.

Volker Lannert, ILT, Aachen, Germany

According to ILT, researchers from ILT and Aachen University have developed an ultra-high-speed laser deposition process, which is known by its German acronym, EHLA.

Prior to the development of the EHLA, laser deposition welding could only be used in specific situations, therefore restricting its use for larger scale projects.

“We can now use EHLA to apply thin layers in the range of a tenth of a millimeter over large surfaces within a short time, while being resource-efficient and economical,” Andres Gasser, the ILT group manager, said.

Remedying Standard Process Pitfalls

Deposition welding processes are most often used for producing firmly bonded coatings to protect against corrosion. More conventional processes, such as chrome plating, thermal spraying or other deposition welding methods, have their downsides, often tied to high energy use, and in the case of chrome plating, the use of hexavalent chromium, which is restricted in many jurisdictions due to health concerns.

The development of the EHLA can address the drawbacks of standard deposition welding processes in a variety of ways.

Oftentimes, chrome plating can develop pores and cracks. The EHLA process produces non-porous layers and provides efficient long-term protection. EHLA metallurgically bonds the resulting layer to the base material and as a result, it does not delaminate, the ILT team says.

One drawback to thermal spraying is that only half of the material used winds up coating the surface of the component, the researchers say. As a result, layers bond very weakly with the substrate. This results in a very porous coating, which then requires an application of several layers each 25 to 50 micrometers thick. Alternatively, the EHLA process uses 90 percent of the material. The layers this process produces both bind firmly to the substrate and are nonporous, the group says.

When it comes to TIG welding and other conventional welding practices, the layers that are left behind are usually 2 to 3 millimeters thick, which both uses too much material and is far too thick. Laser material deposition, on the other hand, allows for layers that are 0.5 to 1 millimeters. This process requires a certain melt-pool size to create a defect-free layer. The component is melted locally, while a powder nozzle guides a powdery additive into the melt pool.

“With EHLA, the laser melts the powder particles while they are above the melt pool,” explained Gasser. From there, drops of liquid material fall into the weld pool, rather than the solid powder particles, which results in the layers becoming homogenous. On top of this, this means less base material needs to be melted. Only micrometers are needed, whereas previously it was up to a millimeter.

The EHLA process can also be used for new material combinations such as coatings on aluminum base alloys. The component can also be coated 100 to 250 times faster, which allows for treatment of heat-sensitive materials.

Prize-Winning Work

At the Fraunhofer General Assembly Meeting on May 30, Andres Gasser, Gerhard Maria Backes and Thomas Schopphoven received the Joseph von Fraunhofer prize for their work.

There will a presentation of the EHLA process at Laser World of Photonics, which is held in Munich, Germany from June 26-29.

According to ILT, the first EHLA system will be delivered to China in the near future. There, it will be used for research and industrial use at the Advanced Manufacture Technology Center of China Academy of Machinery Science & Technology CAMTC in Beijing.

   

Tagged categories: Asia Pacific; Coating Application; Corrosion protection; EMEA (Europe, Middle East and Africa); Latin America; North America; Protective Coatings; Research; Research and development

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