Titanium nitride (TiN) (sometimes known as Tinite) is an extremely hard (~85 Rockwell C Hardness or ~2500 Vickers Hardness or 24.5 gigapascals), ceramic material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve the substrate's surface properties. 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 and in dental alloys (especially hip replacement implants).