Evaluation of Gamma Based Titanium Aluminide Wear Behavior Before and After of Plasma Nitriding and Physical Vapor Deposition Duplex Process

The aim of this study is the improvement of high temperature wear behavior of gamma-based titanium aluminide (Ti-48Al-2Cr-2Nb at.%) by duplex process of “plasma nitriding” and “physical vapor deposition”. Plasma nitriding processes were carried out at temperature of 800°C, duration of 9 hours and gas ratio of N2/H2:1 by amplified cathode method. Four alternative layers of TiN and Ti33Al67N were applied by PVD at temperature of 300 ˚C and duration of 2.5 hours. Characterization tests were conducted with the aid of scanning electron microscopes and X-ray diffractometer. The evaluations of surface properties were carried out by micro-hardness and scratch testers. Wear behavior was evaluated using pin on disk method at 25, 300 and 600°C. Combination of Ti2AlN, TiN and (TiAl)N after duplex treatment were confirmed by XRD results. The surface hardness of 2400 HV0.025 and critical adhesion loads of 24.1 ,60.1 and 77.6 N were reached for the first cohesive failure level (LC1), the first adhesive failure level (LC2) and the first interfacial spalling (LC3) by duplex treatment. The wear rate at temperatures of 25, 300 and 600 ˚C decreased in order of 20, 55 and 100 in comparison with substrate. The abrasion, delamination and oxidation were detected as the main active wear mechanism in this tribological system.