A diamond-like coating may not be forever, but it will make a significant contribution to increased mechanical life and efficiency.
So says Finish company DIARC-Technology, whose latest-generation system enables ta-C (tetrahedral amorphous carbon) structured diamond-like coatings to be volume-manufactured for applications in engines, hydraulic systems, and power transmissions, plus precision tools.
“On tools, the improvement in service life offered by the coating plays a particularly important role,” said DIARC-Technology Vice President Tapani Haikola.
The company’s latest technology is aimed at manufacturers needing a hard-wearing protective coating that can deliver increased efficiency and reliability of components operating in challenging environments. The new-generation coatings are said to offer “extremely” low friction in the presence of lubricants, leading to a reduction in energy consumption.
Haikola explained that DIARC-Technology is a pioneer of low-temperature vacuum plasma deposition technology. It allows for a thin, tough layer of diamond-like carbon to be laid down onto a range of materials from metals to plastics.
The process is based on a plasma accelerator technique to create highly ionized plasma of the coating material. The plasma is electromagnetically accelerated to a high velocity and directed at the workpiece. Typical deposition temperature is below 100°C (212°F), but this can be reduced significantly when necessary, and coating thickness can be varied to meet particular specifications.
The DIARC process has low energy and raw material demands, Haikola noted, and no hazardous chemicals or gases are used. Coating properties and performance can be optimized for specific applications.
“One micrometer layer of amorphous diamond wears out in the same time as one millimeter of hardened steel,” he said. “On modern machine constructions, the wear is in general well under control, and one of the main challenges is to prevent unexpected failures like seizure of moving parts, which may happen in overloading conditions when lubrication does not work properly or is ceased for some reason.”
With regard to efficiency, Haikola said, in power transmissions the friction coefficient has been reported to be 25-30% less when the gear wheels are coated with DIARC diamond compared to uncoated steel gear wheels.
The system has been designed to coat small parts in quantity. Maximum dimensions of parts are diameters of 660 mm (26 in), length of 700 mm (27.6 in), although in some cases this can reach 1000 mm (39.4 in), and weight of 250 kg (551 lb).
The coatings technology used by DIARC-Technology originates from the development in the late 1980s by researchers at Helsinki University. The work later was spun out as a separate company. DIARC-Technology is now engaged in an active research program, with collaboration in several EU projects plus companies, universities, and research institutions. The company typically develops solutions for customer applications via a joint R&D project. In the production phase, its Job Coating Service is adapted to serve customers for both small batches and larger series requirements.