Oerlikon Balzers Customer Magazine

Technology & Innovation

BEYOND SURFACES

Fall

A hard shell protects the sea turtle from its

enemies. Still, it is designed in such a way

that the animal can swim and manoeuvre

well underwater. The coatings made by

Oerlikon Surface Solutions are flexible in

a similar fashion: They protect turbines

in hydroelectric plants from wear and

erosion, for example, and at the same

time enable almost completely friction-free

movement of the turbine blades – and

that optimizes energy production.

Using nature’s strategies to make

better products

Surfaces in nature can help the tissue underneath

– and the organism – function well in an extreme

environment. Desert plants survive long periods of ex-

treme aridity with the help of waxy surfaces and adjust

able pores that control how much water escapes into

the air. Similarly, turbines in power plants work most

efficiently around hot gas at high pressure. But if it gets

too hot for too long, their blades, which are made from

superalloys, can react with oxygen, corrode and fail. A

protective coating that survives blast-furnace condi-

tions keeps oxygen from diffusing in and corroding the

turbine blades. This enables the turbine to last longer

and work better.

In some cases, surfaces can be designed through

biomimicry – by imitating the molecular strategies that

animals and plants employ. “If you wanted to make a

coating that repels water, you could investigate the lotus

plant,” says Helmut Rudigier, the Chief Technology Officer

of the Oerlikon Surface Solutions Segment. “Studying

how plants control gas flow into a leaf could help scien-

tists design new types of coatings that restrict the diffu-

sion of gases,” Dommann adds.

Changing how a material interacts with

its environment

Surface coatings can endow materials with proper-

ties the bulk material underneath does not possess.

Placing a silver-imbued coating on titanium bone-repair screws, for example, can prevent deep infections

after surgery because silver is a potent antibacterial

agent. “Coatings offer the possibility of changing how

a material interacts with its environment,” Dommann

says.

Most often, however, studying nature reveals

strategies that materials scientists can pursue to develop

new coatings. Synthetic surface coatings, unlike human

skin, have traditionally offered one function and one func-

tion only. “But in nature a coating has a lot of different

functionalities at the same time,” Dommann says.

Gear surfaces in a race car’s gearbox, for example,

should be hard to enable them to transfer force

efficiently and with the required durability. Building them

with tungsten carbide takes care of that. But they should

also slide off one another easily to reduce friction and

transfer maximal power to the drivetrain. Tribological

coatings – coatings that reduce friction – help. To make

gears slip, engineers layer in graphite, a softer, more

slippery material, into the gear’s surface coating. The

result is a stable but low-friction gearbox that’s used in

Formula 1 cars.

Vision for the future: smart coatings

Nature’s surfaces can often adapt to changing circum-

stances, making almost every coating on plants or

animals a smart coating. If you get a scratch on your

skin, your body activates wound-healing processes to

close up the scratch and replace the damaged tissue.

Industrial surface solutions traditionally have not been

so adaptable, but look for them to catch up in the

years to come. Just think of adaptive airplane wings

that shapeshift and become rougher to create the

drag needed during takeoff. The pilot would no longer

have to adjust flaps and winglets to get the plane off

the ground, and the wings would adjust during flight to

become smoother and aerodynamic.