Unlocking potential: PEO coatings redefine durability in critical industries

Industries require lightweight, durable components with specific surface properties, yet current methods like plasma electrolytic oxidation (PEO) are limited by high costs and scalability issues. Existing surface modification processes hinder large-scale manufacturing due to cost and scalability limitations. Is there a solution for industrial surface modification that overcomes these challenges? Recent advancements in PEO technology, led by Dr Anna Buling, CEO of ELB Eloxalwerk Ludwigsburg in Germany, offer promising alternatives, including tailored adaptations for alloys, low-viscosity oil combinations, and laser structuring hybridisation, providing cost-effective and scalable solutions for critical industries.

Industries such as aerospace, automotive, and medical are under constant pressure to develop components that are not only lightweight but also possess specific surface properties to minimise wear and friction. Meeting these requirements is critical for enhancing performance, reducing energy consumption, and extending the lifespan of parts. Dr Anna Buling, CEO of ELB Eloxalwerk Ludwigsburg in Germany, focuses on surface technologies for lightweight metals, particularly environmentally friendly plasma electrolytic oxidation (PEO) technologies, renowned for its high corrosion and wear resistance.

Plasma electrolytic oxidation: an overview

PEO is a surface modification process that improves the surface hardness, corrosion resistance, and wear resistance of lightweight metals, making them suitable for various industrial applications. Specifically, PEO can act as a surface modification process that involves the formation of oxide ceramic coatings on metals like aluminium, magnesium, and titanium. This process is performed by subjecting the metal to high-voltage electrical discharges in an electrolyte solution, leading to the growth of a ceramic layer that is tightly bonded to the substrate. The resulting coatings offer excellent wear resistance, corrosion protection, and thermal stability, making PEO an attractive option for demanding applications.

Despite its potential, PEO has not been widely adopted in industrial applications. The primary reasons for this are its high costs and its current suitability mainly for small parts or limited production runs. This limits its use in large-scale manufacturing, where cost-effectiveness and scalability are crucial. However, companies like ELB have been offering PEO surfaces such as ULTRACERAMIC® for over two decades, particularly in environments where lightweight metals like aluminium and magnesium are exposed to harsh conditions. PEO applications include enhancing the durability of aircraft engine components, improving the corrosion resistance of automotive parts, increasing the longevity of medical implants, and enhancing the wear resistance of industrial machinery components. These PEO-treated surfaces have demonstrated significant improvements in terms of corrosion resistance and wear protection.

Recent developments in PEO technology

In recent years, there have been several advancements in PEO technology aimed at enhancing its applicability and performance. A remarkable development is the adaptation of the PEO process for aluminium casting alloys – tailored aluminium blends designed for casting processes. Aluminium, known for its lightweight and high strength-to-weight ratio, is widely used in various industries.

However, its relatively poor wear resistance can limit its application. By applying a specially adapted PEO process, researchers have been able to significantly improve the tribological properties – characteristics of materials that determine how well a material can withstand mechanical interaction over time without significant degradation – of aluminium casting alloys. This has opened new possibilities for using aluminium in components that require both light weight and high durability.

PEO is a surface modification process that improves the surface hardness, corrosion resistance, and wear resistance of lightweight metals, making them suitable for various industrial applications.

Another significant advancement is the combination of PEO coatings with new low-viscosity oils, led by Dr Buling’s research group. These oils can penetrate the nanoporous structure of the PEO coatings, providing additional lubrication and further reducing friction. This combination has shown enhanced positive effects, making it a promising solution for applications where both low friction and high wear resistance are critical.

To further improve the performance of PEO coatings, the team have explored the use of direct interference laser patterning and hybridisation techniques. Laser structuring involves creating micro- and nano-scale patterns on the PEO surface, which can enhance the coating’s mechanical and tribological properties. Additionally, incorporating a solid lubricating polymer into the PEO layer has been shown to further reduce friction and wear. This hybrid approach combines the benefits of hard ceramic coatings with the self-lubricating properties of polymers.

Testing and results

The advancements in PEO technology have been supported by extensive testing, demonstrating the potential of these coatings in various applications. Dr Buling’ team led a 1,000-hour tribological test to evaluate the performance of PEO-coated components. The results presented by the team were particularly promising, showing low friction and almost no wear over the extended test period. These results indicate that PEO coatings can provide long-lasting protection and maintain their performance even under prolonged use.

Additionally, the group investigated the combination of PEO with PEEK (polyether ether ketone), a high-performance engineering thermoplastic known for its excellent mechanical strength, chemical resistance, and thermal stability, making it ideal for demanding applications in industries such as aerospace, automotive, and medical devices. The group showed that PEO surfaces with high-performance polymers like doped PEEK exhibit excellent results in terms of friction and wear reduction. In particular, the combination of PEO and doped PEEK has been found to offer low friction and wear without the need for additional lubricants, making it a sustainable and efficient solution for various applications.

Advancements and innovations in PEO coatings

Looking ahead, Buling and her research team suggest there are several potential improvements and areas of research that could further enhance the performance and applicability of PEO coatings. Using laser radiation for patterning and selective laser sintering (a 3D-printing technique) of the polymer top coating can further improve the performance of PEO systems. Selective laser sintering allows for the controlled deposition of polymer materials, enabling the creation of tailored composite coatings with optimised properties. The development of advanced lubrication strategies, such as the use of nanolubricants or self-healing lubricants, can further enhance the tribological performance of PEO coatings.

PEO has the potential to become a more widely adopted solution for improving the durability and performance of lightweight metal components.

Nanolubricants contain nanoparticles that can fill in surface asperities and reduce friction at the micro-scale, while self-healing lubricants can repair minor damage to the coating, extending its lifespan. Integrating PEO coatings with smart coating technologies, such as those that can respond to environmental stimuli or self-monitor their condition, can provide additional benefits.

For example, coatings that can change their properties in response to temperature or load changes can optimise their performance in real-time, while self-monitoring coatings can provide valuable data on wear and degradation, enabling predictive maintenance and reducing downtime.

Future prospects and industry impact of PEO technology

The combination of PEO surfaces and advanced materials like high-performance polymers holds significant promise for creating sustainable and high-performance systems. These systems can provide excellent wear resistance and low friction, potentially without the need for additional lubricants, which can contribute to reduced maintenance costs and environmental impact. This makes them particularly attractive for applications in industries such as aerospace, automotive, and medical, where the demand for lightweight and durable components is ever-increasing. In aerospace, for instance, reducing component weight is crucial for fuel efficiency and overall performance, whereas in the automotive sector, it can lead to improved vehicle efficiency and reduced emissions. Medical devices also benefit from enhanced durability and biocompatibility, ensuring longer-lasting implants and instruments.

As research and development continue, Buling is hopeful that we can expect further improvements in the performance and cost-effectiveness of PEO coatings. The ongoing advancements in smart coating technologies are also promising. These technologies could lead to the creation of self-healing coatings that automatically repair minor damages, thereby further extending the lifespan of components and reducing the need for frequent replacements. Smart coatings can also adapt to changing environmental conditions, offering dynamic protection and performance enhancements.

By addressing the current limitations of PEO technology, such as high costs and scalability challenges, and leveraging new technological advancements, PEO has the potential to become a more widely adopted solution for improving the durability and performance of lightweight metal components. The continuous innovation in this field promises to expand the applicability of PEO coatings across a broader range of industrial applications, ultimately contributing to more sustainable and efficient manufacturing practices. The future of PEO technology looks bright, with the potential to revolutionise the way we approach surface protection and enhancement in critical industries.