Developing components that are lightweight and easy to produce is a key issue for many industries. Whether it’s reducing the weight of portable military equipment, aircraft or high-performance cars, weight reduction is at the top of many industry agendas. Advances in composite technologies mean plastics are increasingly being considered alongside traditional materials such as aluminium and titanium, but there is one material that, until recently, was perceived as being too volatile to offer a viable, lightweight solution for many mainstream applications: magnesium.
Weighing 30 percent less than aluminium by volume and being both stiffer and stronger weight for weight, magnesium has a reputation for being somewhat reactive. The development of more stable alloys, together with advances in surface technologies, mean that this is now changing and magnesium is becoming an exciting, viable option for many applications, particularly those where metallic components are preferred, for example, where components need to be strong, ductile, and have specific thermal or electrical properties as well as being easy to fabricate.
At Keronite, we’ve been working in conjunction with a number of businesses to develop technologies that will allow manufacturers to take advantage of the significant weight savings offered by magnesium. Magnesium Elektron, with its Elektron®43 alloy, has recently shown that magnesium alloys can meet tough flammability requirements, driving a change in the wording of SAE AS8049, the aerospace safety standard, that will allow magnesium components into passenger aircraft. But this is only part of the story. In reality, corrosion is the greatest enemy of magnesium, which is where specialised surface treatments come in.
Magnesium is extremely chemically active and protecting it presents its own challenges. However, at Keronite we have now commercialised the use of plasma electrolytic oxidation (PEO) to impart a highly abrasion and corrosion-resistant ceramic coating to magnesium alloys. This offers real performance improvements without adding significant weight.
PEO is an electrolytic immersion process that passes an electrical current through the surface of a light metal part, in this case magnesium. The surface of the metal oxidises, generating a plasma oxide layer that converts the surface into a hard, yet flexible, ceramic layer that grows into and outwards from the surface of the metal. This creates a strong bond and can be tailored to deliver a range of alloy performance improvements. The process can also be honed to offer bespoke solutions for different applications. Simply by making adjustments to a range of controllable parameters, the coating can be engineered to offer multi-functional performance on different parts of the same component. So, where one part of the component might need increased wear resistance, another may need better thermal or aesthetic qualities, all of which can be delivered in one, repeatable treatment process. The coating itself is derived from the original base metal, meaning the process doesn’t bulk out the component, which is a feature of many traditional coatings that ultimately undermines the whole lightweighting effort. Add to this the fact that the Keronite finish can remove the need for primers, and it’s clear that the potential weight savings on offer are significant.
These developments are exciting news for OEMs working across high-performance industries such as aerospace, automotive and motorsport, as it means they can now consider magnesium components as a genuine alternative to traditional materials such as aluminium and steel. From engine components and fuel systems to energy recovery systems and structural parts, OEMs in the motorsport sector are already exploring the benefits of magnesium and this is beginning to trickle down to the mainstream passenger car sector, where manufacturers are increasingly adopting magnesium for things like alternators, transmission casings, motor housings, and even body parts.
Finally, the recent change to AS8049 also opens up a raft of opportunities for aircraft and aerospace component designers due to the large volumes and repeatability of components required in this market. For example, we see an opportunity to use magnesium in aircraft seating that could offer potential weight savings of almost 20 percent per part; with hundreds of seats on a typical commercial aircraft, the overall savings would be huge, making a sizeable difference to the aircraft’s environmental impact as well as its running costs.
Steve Montisci – Keronite International
Article originally taken from Engineering Subcontractor Magazine – May 2016 Click here for Magazine