New capabilities enable researchers to deposit gradient, multilayer, solid-lubricant coatings onto aerospace components.

AFRL materials scientists have acquired an automated deposition chamber (see figure on next page) that enables them to simultaneously or sequentially deposit solid-lubricant coatings onto target objectives from any of three deposition sources. The chamber also incorporates AFRLinvented technology entailing a hybrid, magnetron-assisted, pulsed-laser deposition (PLD) process. The scientists acquired the chamber to study protective solid-lubricant coatings capable of resisting wear and corrosion in (relatively) large friction components, including gears and bearings, and preventing static friction in microelectromechanical systems devices such as switches and connectors.

The new deposition chamber combines two existing deposition processes: magnetron sputtering (MS) and PLD. MS is a process that uses magnetic fields to increase the flux rate of energetic particles (ions) as they bombard a solid surface. This bombardment ejects atomic species from the surface for subsequent deposition onto the target objective. PLD is a method of thin-film growth that involves the evaporation of a solid target by means of short, highenergy laser pulses. A laser pulse of 1-10 J/cm2 vaporizes the surface of the target, and the resulting vapor condenses on a substrate or similar target objective. Combining MS and PLD creates a unique approach for depositing solid-lubricant coatings. The automated deposition chamber provides a 3 in. square target deposition area and can accommodate specimens up to 12 in. long via a linear sample manipulator. This capability allows a variety of components (e.g., bearings) to be coated with developmental lubricants.

The scientists equipped the new chamber with two, 2 in. targets for the direct current MS guns—one rotating, 4 in. diameter laser ablation target, and a galvanometer beam steering device for sweeping the laser beam across the rotating target. Researchers can manipulate the chamber pressure from 1 mTorr to 1 Torr with any combination of three gases, and can evacuate the chamber to 1 nTorr. Additionally, they can bias the substrate/target object voltage up to 1000 V and heat samples to more than 600°C. The new deposition chamber’s built-in oscilloscope and photomultiplier tube arrangement optically monitor process emissions, which are indicative of deposited species concentrations. The chamber thus enables closed-loop feedback control to regulate the deposition rate of a particular species over an extended period of time.