An investigation of nitrided layer prepared by direct current nitrogen arc discharge

A simple direct current (DC) nitrogen arc discharge method is presented, which allows for in situ nitriding of titanium at atmospheric pressure. The microstructure and microhardness of the nitrided layer and effects of the arc discharge current were investigated. The nitrided layer was mainly composed of TiN dendrites and small amounts of TiN0.3. The density and size of the TiN dendrites gradually decreased from the surface towards the titanium substrate. The layer had a good adhesion with titanium. With an increase of the arc discharge current from 40 to 80 A, the TiN dendrites coarsened, the layer thickness and amount of TiN increased and the layer hardness enhanced. The nitrided layer with the highest hardness value of 1600 HV and thickness of 1800 μm was obtained for an arc discharge current of 80 A.