The variety of small to large electric vehicles and their hybrid variants is constantly increasing, and vehicle manufacturers can no longer afford not to have electric vehicles in their range. But how can they optimise this technology? Are there other ways to improve efficiency and range, protect components from premature failure, and reduce maintenance costs for the end user as a result? Specialised PVD coatings are key design elements that reduce friction and wear, improving the efficiency of drivetrain technologies in electric vehicles. Dr. Mayumi Noto, Head of Global Business Development for E-Mobility, Oerlikon Balzers explains further.
Producing more efficient engines has become an important issue as the automotive industry seeks to reduce CO2 emissions from petrol and diesel engines. Specialised PVD coatings have become key design elements for reducing friction and wear in engine components and minimising mechanical loss, which boosts engine efficiency and performance. And as manufacturers develop increasingly advanced electric vehicles, Oerlikon Balzers one of the world’s leading suppliers of surface technologies has been working closely with leading technology companies to design and optimise components for electric drive systems.
A typical electric car is equipped with an electric motor with a maximum power of 30 to 70 KW, a maximum torque of 130 to 200 Nm and a maximum rotational speed of 7,000 to 20,000 rpm. Key adjacent components such as gears, bearings and shafts need to be optimised to satisfy various complex objectives such as noise reduction and efficiency during more demanding operating conditions. Gears in electric car transmissions experience higher rotational speeds and are subjected to various driving styles, increasing the chances of wear, pitting, tooth failure and scuffing due to repetitive friction at high speeds. Poor lubrication or the presence of contaminants can significantly reduce the service life of gears.
Specialised PVD coatings for the automotive industry
A coating with a thickness of just 0.5 to 4 micrometres considerably reduces friction and increases surface hardness to protect gears and reduce gear losses, thereby increasing the efficiency of electric drivetrains.
PVD is typically used to coat components at relatively low coating temperatures of 200-500 °C. These temperatures are ideal because they are below the tempering temperature of steels, which means that the fundamental material properties are not affected.
The BALINIT C coating from Oerlikon Balzers is a WC/C ductile carbide/carbon coating that offers particularly high resistance to adhesive wear (scuffing). It has a multi-layered structure where fine WC crystals are embedded into an amorphous carbon matrix (Image 1). This unique structure enhances the load-bearing capacity and ductility of the coating even when there is little or no lubrication.
The standard FZG C test shows that fatigue strength is increased by 10-15% over case-hardened but uncoated gears (Figure 1).
The low friction coefficient of BALINIT C contributes to lower local surface pressure (Hertzian pressure) and offers superior running-in characteristics. A scuffing test shows that gears coated with BALINIT C have a longer service life of over 2 million tooth contact cycles (Figure 2).
Another example is the BALINIT DLC coating, a metal-free, carbon-based coating that provides even higher hardness. Applied using Plasma-Assisted Chemical Vapour Deposition (PACVD), this coating is designed to withstand extremely high wear and allow high sliding speeds to protect against abrasion, scuffing and cold welding. The BALINIT DLC coating has been developed in order to improve the performance and service life of differential gear shafts in advanced electric drivetrain systems.
“By incorporating BALINIT coatings into component design, our partners have improved electric drivetrain performance without compromising other requirements, such as having a lightweight, compact design and reducing overall production costs”, explained Dr. Mayumi Noto, Head of Global Business Development for E-Mobility, Oerlikon Balzers.
Surface solutions for a wide range of automotive industry applications
Compact, lightweight and highly integrated design of electric car components requires production technologies which offer higher precision and quality despite low tolerances and highly complex production processes.
primeGear is a customised and highly integrated service which delivers unbeatable gear cutting tool performance. A team of experts at Oerlikon Balzers determines the critical improvements which can be made in the gear production chain by conducting detailed tool surface failure analyses and consulting with the customer. Improving the tool life cycle requires a holistic approach, whether in surface treatment, cutting processes, tool handling or reconditioning, and this can lead to more sustainable and higher-quality gear production processes. “This is possible due to our learning curve of 70 years as leading supplier for surface solutions, and the integral concept of primeGear”, Dr Mayumi continued.
For large battery boxes and electric motor housings, Oerlikon Balzers provides solutions to improve aluminium die casting and steel sheet forming tools. In high pressure die casting, BALINIT coatings reduce soldering, heat cracks, erosion and abrasion on moulds, mould inserts and cores. This results in a longer service life and reduced waste, giving manufacturers higher-quality cast parts and reduced costs. For large forming dies, Pulsed-Plasma Diffusion (PPD) technology helps tools last longer by hardening their surfaces and increasing their wear resistance. PPD means tools need to be maintained less frequently and is a more environmentally-friendly process than hard chrome coating.
Lightweight plastic parts are key components in car interior and exterior design. As plastics become stronger (higher glass fibre content), more functional (sensors and lighting) and more attractive in design (texture and colour), forming technologies to produce plastic parts need to overcome new challenges. BALINIT coatings can prevent corrosion and wear and reduce polymer sticking, enabling easy release and scratch-free products for injection moulding and extrusion.
Providing customised solutions to special requirements
We use our strong R&D capabilities to tailor coating solutions to meet customer requirements. In addition to coating thickness and hardness, properties such as structure, chemical and temperature resistance and adhesion can be optimised to suit individual needs.
With almost 75 years of expertise in coatings, we have customised pre- and post-surface treatments to produce the best possible surfaces in order to achieve optimum performance of coated parts and tools.
“Together with our automotive partners, Oerlikon Balzers will continue to provide solutions and innovation to support electric vehicles in order to give the automotive industry a more environmentally-friendly and sustainable future,” Dr Mayumi concluded.
Whether engines or drive trains, oil pumps or brakes, headlights or rims, bodywork or interior: in modern motor cars, motor cycles, trucks, ships and trains there is hardly anything, in manufacture or in operation, where Oerlikon Balzers coatings are not involved.
