Study of surface hardness of Al-6063 under plasma nitridation

Nitriding is a process of introducing nitrogen in metals so as to modify the surface properties of the material, e.g. increase in hardness, wear resistance and corrosion resistance, etc. As the name infers, the process uses IONized nitrogen alone, or in combination with other gases to react with the work surface. The IONized nitrogen also provides the characteristic purple glow. The experimental set-up consists of a glass (discharge) tube, a high voltage D.C. power supply, a gas distribution system, and a pressure control system. In this system, the D.C. potential is applied between the hearth plate (on which the work piece is placed) and an electrode, which is grounded. The hearth plate is at negative potential. Nitriding takes place as current is increased into the abnormal glow discharge region. In this region current density is uniform around the entire cathode surface, which is indicated by uniform purple glow. Any increase in current within the abnormal region gives an increase in current density without affecting uniformity. The ASA-6063 aluminium alloy samples are chemically cleaned and treated for nitridation under different percentages of nitrogen with argon acting as a catalyst keeping all the other parameters constant. The hardness of the material surface can be measured using different methods. Here we have measured the hardness using Duro-meter.