Zhonghuai Wang, Michael Akkaoui, Tanury Industries, Lincoln, RI
This paper summarizes the growth defects in physical vapor deposition (PVD) coatings focusing on ceramic Titanium Nitride Oxide (TiN O_x) coatings by conventional cathodic arc vaporization technology relative to large amounts of microdroplets and macroparticles produced. TiNO_x exhibit many positive attributes such as wide color choices with different visible light wavelength ranging roughly from 400 nm (violet) to 700 nm (red), high heat resistance for tools or sharp blade applications. The films can be dielectric with high durability and improved scratch-resistance compared with pure metal. Certain films have anti-bacterial properties and can be biocompatible for medical applications. In our evaluation, cathodic arc deposition was utilized to deposit TiN O_x coating on a polished brass substrate plated with nickel and chrome. While the films are typically very brilliant in color and appearance, the film may exhibit particle size white spots roughly ~ 0.3 µm in diameter. We theorize that the coating defects are related to arc macro particles in the film that can be seen with the naked eye. We have empirical evidence that the white spot area has no coating or poor adhesion, and that the substrate was exposed. We utilized a scanning electron microscope (SEM) with Energy Dispersive X-ray analyzer (EDS) to evaluate the white spots. The SEM showed that the poor coating area contained foreign elements such as Fluorine, Aluminum, Silicon, Calcium, Potassium, Sodium and Chlorine. In order to solve this defect issue, we employed different types of plating or cleaning processes including post plating Argon or oxygen plasma pretreatment and several PVD coating parameters were modified to improve the coating quality. This paper will discuss these experiments and their results.