Look Ahead: Hard and sticky

Hydrogen-free diamond-like coatings (tetrahedral-amorphous-carbon DLC) have traditionally had problems adhering to the tool substrate, according to Lucien Peeters, tool product manager for Hauzer Techno Coating BV. To overcome that, he noted that the manufacturer of vapor deposition coating equipment for cutting and forming tools, mold and dies conducted research and developed ta-C coatings that adhere better.

The coating is most effectively deposited with the company’s Flexicoat coating machines using circular arc technology, he added, but filtered arc and laser arc are alternatives when the posttreatment polishing step must be eliminated. “When looking at reproducibility, industrial-acceptable deposition rates and process stability, we see circular arc as a very good solution,” Peeters said.

Courtesy of Hauzer Techno Coating

Top: An impact fatigue test of a ta-C coating shows a high level of adhesion with only some small cracks. Below: Taps coated with ta-C.

In connection with the European Nanocoat project, several different DLCs deposited on automotive engine components (tappets) were tested at the Fiat Research Centre, Turin, Italy, and at Hauzer. The tests concluded the ta-C coating had the highest hardness of 40 to 70 Gpa, or up to 7,000 HV, and the lowest friction coefficient of 0.02 to 0.1, which was determined in a pin-on-disc test, according to Hauzer.