TiN coated drill|right
Dark gray TiCN coating on a Gerber pocketknife|right
Titanium nitride (TiN) is an extremely hard (~85 Rockwell C Hardness or ~2500 Vickers Hardness)
[BryCoat Titanium Nitride.], ceramic material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve the substrate's surface properties.
TiN has excellent infrared (IR) reflectivity properties, reflecting in a spectrum similar to elemental gold (Au). Depending on the substrate material and surface finish, TiN will have a coefficient of friction ranging from 0.4 to 0.9 versus itself (non-lubricated). Typical formation is a face-centered cubic crystalline structure with a roughly 1:1 stoichiometry. TiN will oxidize at 600 °C (~1100 °F) at normal atmosphere, and has a melting point of 2930 °C.
Far and away the most common use for TiN coating is for edge retention and corrosion resistance on machine tooling, such as drill bits and milling cutters, often improving their lifetime by a factor of three or more.
Because of TiN's metallic gold color, it is used to coat costume jewelry and automotive trim for decorative purposes. TiN is also widely used as a top-layer coating, usually with nickel (Ni) or chromium (Cr) plated substrates, on consumer plumbing fixtures and door hardware. TiN is non-toxic, meets FDA guidelines and has seen use in medical devices and bio-implants, as well as aerospace and military applications.
Such coatings have also been used in implanted prostheses (especially hip replacement implants). Such films are usually applied by either reactive growth (for example, annealing a piece of titanium in nitrogen) or physical vapor deposition (PVD), with a depth of about 3 micrometers. Its high Young's modulus (600 GPa gigapascals)
[MatWeb.] relative to titanium alloys (100 GPa) means that thick coatings tend to flake away, making them much less durable than thin ones.
As a coating it is also used to protect the sliding surfaces of suspension forks of bicycles and motorcycles.
Though less visible, thin films of TiN are also used in the semiconductor industry. In copper-based chips, such films find use as a conductive barrier between a silicon device and the metal contacts used to operate it. While the film blocks diffusion of metal into the silicon, it is conductive enough (30–70 μΩ·cm) to allow a good electrical connection. In this context, TiN is classified as a "barrier metal", even though it is clearly a ceramic from the perspective of chemistry or mechanical behavior.
The most common methods of TiN thin film creation are PVD and chemical vapor deposition (CVD). In both methods, pure titanium is sublimated and reacted with nitrogen in a high-energy, vacuum environment.
Bulk ceramic objects can be fabricated by packing powdered metallic titanium into the desired shape, compressing it to the proper density, then igniting it in an atmosphere of pure nitrogen. The heat released by the chemical reaction between the metal and gas is sufficient to sinter the nitride reaction product into a hard, finished item. See powder metallurgy.
There are several commercially-used variants of TiN that have been developed in the past decade, such titanium carbon nitride (TiCN) and titanium aluminum nitride (TiAlN), which may be used individually or in alternating layers with TiN. These coatings offer similar or superior enhancements in corrosion resistance and hardness, and additional colors ranging from light gray to nearly black, to a dark iridescent bluish-purple depending on the exact process of application. These coatings are becoming common on sporting goods, particularly knives and handguns, where they are used for both cosmetic and functional reasons.