How Does Ion Nitriding Improve Titanium Alloys?

Ion nitriding improves titanium alloys by increasing surface hardness, wear resistance, scuff resistance, and corrosion resistance in reducing environments while preserving core toughness and ductility. It addresses titanium’s poor wear and galling resistance and its limited corrosion resistance in reducing media. The process is used in petrochemical, defense, and medical-equipment applications.

Nitriding temperature and time control case hardness and depth. Properly treated surfaces are golden yellow.

Hydrogen embrittlement is an important concern. Nitrogen-argon mixtures or even pure nitrogen are commonly used. If a hydrogen-containing atmosphere is used, such as a nitrogen-hydrogen mixture or ammonia, stop the hydrogen supply when the part cools to 600°C after nitriding to reduce embrittlement risk.

Titanium ion nitriding is performed above 800°C. Equipment may use an externally heated ion-nitriding furnace or a conventional cold-wall furnace. To raise parts to the required temperature and maintain uniformity, a simple approach is to place an auxiliary cathode at the same potential around the workpiece. It acts as an additional peripheral heat source, reduces radiative heat loss, accelerates heating, and improves temperature uniformity.

Equipment designed for titanium must reach about 900°C while keeping every seal reliable. Install one or more all-metal radiation shields between the workpiece and furnace cover and between the cathode worktable and furnace baseplate.

Because titanium has a strong affinity for oxygen at 900°C, oxygen partial pressure must be kept as low as possible. Gas purity and furnace leak rate are the principal controls. A dedicated titanium ion-nitriding furnace is preferable so that substances adsorbed during treatment of other materials do not contaminate the titanium process.