Studies of Porosity in Ceramic Titanium Nitride Oxide PVD Coatings
December 11, 2024 12:00 am
This paper summarizes a particular growth defect known as voids in physical vapor deposition (PVD) coatings. We focused on ceramic Titanium Nitride Oxide (TiNOx) exhibits many positive attributes:
- A wide color pallet with different visible light wavelengths ranging from 400 nm (violet) to 700 nm (red).
- High heat resistance for tools or sharp blades applications.
- These films can be dielectric with high durability with 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 TiNOx coating on a polished brass substrate plated with nickel and chrome. While the films are typically very brilliant in color and appearance, we sometimes see white spots (or voids) the size of ~ 0.3 μm in diameter. These coating defects are caused by arc macro particles in the film and can be seen by the naked eye. While it may be difficult to understand the direct cause, our investigation has shown that the white voids had no coating present and or poor adhesion exposing the substrate layer. We utilized a scanning electron microscope (SEM) with Energy Dispersive X-ray analyzer (EDS) to evaluate the voids. The SEM showed that the poor coating area had a variety of foreign elements such as Fluorine, Aluminum, Silicon, Calcium, Potassium, Sodium or Chlorine from spot to spot instead of elements from plating process or the PVD coating process. In order to investigate this problem, we employed different types of plating or cleaning processes including Argon or oxygen plasma pretreatment. Further, several PVD coating parameters were modified to improve the coating quality. This paper will discuss these experiments and their results.