A detailed analysis of the structural, morphological characteristics and micro-abrasive wear behavior of nitrided layer produced in α (CP–Ti), α+β (Ti–6Al–4V), and β (TNZ33) type Ti alloys

The present work aimed to create a hard surface on a titanium surface via plasma nitriding to improve microhardness and wear properties of the as-cast (α-CP-Ti (CP-Ti), α+β-Ti6Al4V (Ti-Al-4V), and β-Ti-33Nb-33Zr (TNZ-33) samples. For the nitriding process, two temperature conditions (650ºC and 700ºC) were used. The presence of nitrides was evaluated by XRD. The microstructure and chemical composition were studied by electron microscopy and EDS. The roughness was evaluated by confocal microscopy. The microhardness and wear properties were analyzed using the Vickers microhardness and micro-abrasive wear test. Plasma nitriding led to the formation of TiN on CP-Ti, TiN, and Ti2N on Ti-6Al-4V, and TiN and ZrN on TNZ-33 samples. At 700°C, the TiN increased on CP-Ti, while the Ti2N increased for Ti-6Al-4V and the ZrN increased for TNZ-33. The length of the nitride layer decreased when the temperature increased for CP-Ti and Ti-6Al-4V samples. However, for the TNZ33 alloy, the layer increased from 6.3 to 7.6 μm. The chemical analyses confirmed the presence of nitrogen on the substrate surfaces. After the nitriding process, all materials significantly increased the hardness. The hardness after plasma nitriding can be followed by: CP-Ti>TNZ-33> Ti-6Al-4V (at 650°C); CP-Ti>Ti-6Al-4V>TNZ-33 (at 700ºC). The wear properties of all samples were improved after plasma nitriding treatment.