Duralar innovates physical vapor deposition processes using mass flow control
While anodizing and bluing prevent corrosion, it doesn’t strengthen the surface much and can scratch off. Chrome plating has been an alternative, but chrome-6 is toxic, and can still wear, pit, and spall.
Vacuum deposition system manufacturer, Duralar, wanted to develop a fast, diamond-like coating process using physical vapor deposition that’s harder and more durable than either. It would have applications in the prevention of corrosion, erosion, and wear on metal parts.
Challenge 1: Practical innovation requires versatile flow control
R&D means testing, allowing for new formulations of barrier and reactive gases. This requires troubleshooting with different flow ratios and gas types. Duralar needed to find a way to maintain accurate, repeatable flow for changing flow ratios and gases while minimizing the need to recalibrate or purchase new controllers.
They started with a generic vacuum deposition system, but none of the six built-in thermal controllers were calibrated for tetramethylsilane (TMS), a vaporized liquid. The controllers were also unable to accurately flow different gas types without recalibration.
Solution: Anticorrosive mass flow controller with custom gas calibration
TMS isn’t on Alicat’s standard gas list, however, our engineers were able to provide Duralar with a custom solution. The mass flow controller was built as a drop-in replacement, with corrosion resistance and a custom TMS gas calibration.
Because Alicat devices operate using laminar differential pressure technology, they also provided Duralar with a few additional benefits over their old thermal controllers:
- Alicat devices are preloaded with complete performance curves for all preloaded gas calibrations, enabling high-accuracy flow control from 0.5% to 100% of full scale
- No inaccuracies due to changing temperature or pressure conditions, since the closed-loop sensor in the controller compensates for volumetric changes
Soon, Duralar was producing coated parts by pumping down the chamber to a vacuum, flowing in just the right amount of gases, adding material vapor, and turning it into a plasma that bonds to the parts.
Challenge 2: Developing a process to deposit thin coatings
Next, they wanted to develop a process to deposit this thin coating inside tubes and pipes so they could reduce abrasive wear and corrosion. The technique is clever: seal the ends of the tubes, effectively converting the interior of the tube into the vacuum chamber.
The challenge is being able to vary the location of the plasma-producing electrical discharge inside a narrow tube to get a complete coating. To find a solution, Duralar dove again into prototyping and further experimentation.
Solution: Two more mass flow controllers
By using an anticorrosive flow controller for the corrosive TMS and two additional Alicat mass flow controllers, they were able to switch between flowing up to 130 preloaded gases and 20 custom gas mixtures.
They also used our downloadable LabVIEW drivers to build the vacuum process steps so they could control the MFCs and their shut-off solenoids from a remote laptop.
In due time, they had perfected the physical vapor deposition process and began building coating systems to order. Now, you can order diamond-like coatings for your metal parts—or the systems to provide the service for others—and the vacuum coating is more durable than anodizing, while quicker and harder than chrome plating!