GLAM: transforming metal 3D printed titanium surfaces

From aircraft engines to life-saving medical implants, the future is being built one layer at a time. Metal 3D printing allows engineers to design and produce intricate weight-saving designs not previously possible with conventional manufacturing processes. One of its main drawbacks is that parts are left with a rough surface finish, often limiting part performance, particularly in applications involving cyclic loading or metal to metal contact.

The research team engaged in the GLAM (green laser post-processing in additive manufacturing) project has focused on titanium components produced by electron beam powder bed fusion, a process in which metal powders are melted layer by layer using a high-energy electron beam. While efficient, the process leaves surfaces rough, reducing the fatigue life of parts � an issue of critical importance in aerospace, automotive and biomedical applications.

To address this, the GLAM team looked at both printing strategies and post-processing methods. Replacing the common ‘multispot contouring’ technique with a ‘continuous contouring’ approach, where the beam melts the surface of parts in smooth lines instead of several small spots, yielded significantly improved surface textures.

Team also looked at turning a challenge into a potential advantage

Further improvements in roughness necessitated post processing, but this required selecting a process able to cater for complex geometries and internal features.

By submerging parts in a very dilute acid solution, researchers achieved a measurable 35% reduction in surface roughness compared to standard builds. The team also explored laser surface remelting as a safer, greener alternative.

Using laser remelting avoids the need for harmful chemicals but the technique is limited to line-of-sight surfaces, meaning it cannot reach hidden contours of complex 3D geometries. The GLAM team also looked at turning a challenge into a potential advantage: could the roughness of as-printed parts act as tiny lubricant reservoirs under certain conditions?

Experiments in both dry and lubricated wear tests suggest this could help reduce friction and damage in moving metal-to-metal contacts.

The GLAM project brought together expertise from the University of Malta, including Glenn Cassar who led the project, Arif Rochman, Ann Zammit, Andre Giordimaina, Danjel Grima and Bonnie Attard from the Malta College of Arts, Science and Technology. The Maltese team partnered with fellow academics from Shandong University, China. 

The work described in this article was carried out as part of the GLAM (Sino-Malta-2022-13) project which was financed by Xjenza Malta and the Ministry for Science and Technology of the People’s Republic of China (MOST), through the Sino-Malta Fund 2022 (Science and Technology Cooperation).

Kris Bajada is a researcher within the Department of Metallurgy and Materials Engineering. Following industrial experience, he returned to the University of Malta as a research support officer while also pursuing an MSc. He is a UM Council member and social activist.

Photo of the week

Photo: Stockcakehttps://doi.org/10.1002/nano.202100193

Water droplets sit perfectly on rose petals, yet strangely, they don’t roll off easily. This is an unusual combo of water resistance and stickiness. The petal’s surface is covered in a waxy layer and packed with microscopic bumps. Scientists studied both sides of rose petals and found that their surfaces are incredibly rough, even at the tiniest scale, thousands of times smaller than a human hair.

This extreme roughness changes how water behaves on the petals. Understanding this effect can trigger novel developments on nanoscale wetting and biologically inspired functional surfaces. 

DID YOU KNOW?

•         Human fingertips can detect surface features as small as 13 nanometres; that’s about 1/7,000th the width of a human hair. At that scale, you’re feeling something smaller than most viruses!

•         Gecko feet use nano-texture for adhesion: tiny hair-like structures (setae) on their toes allow geckos to stick to walls using van der Waals forces; no glue required.

•         Surface roughness plays a role in your hair too! Its surface roughness affects shine, softness and strength. Chemical treatments and heat styling increase roughness, making hair feel coarse and prone to breakage. Smoother (and often less-damaged) strands reflect light better, which is why conditioners and serums aim to reduce surface roughness for a healthier look.

For more trivia, see: www.um.edu.mt/think.