Titanium Nitride is an extremely hard ceramic material and is often used as coating on steel, carbide and aluminium so as to improve its surface properties. When applied as a thin coating it can harden and protect cutting edges and sliding surfaces. It can also be used as a decorative covering due to its gold appearance. It is also non toxic which makes it a suitable option for medical implants. Normally when applied as a coating it is usually less than 5 micrometres thick. Probably the most widely used application is in the engineering sector where it is used to coat the edges of specialised machine tool cutters such as milling cutters and drill bits. It can also be used to improve the life of everyday cutting hardware like penknives and saws. The lifetime of tools with this coating can be lengthened by times three or more. It is used in the military sector and in the aerospace sector and can be found in use on such items as suspension forks and other sliding surfaces for improved protection.