Densification, microstructure, and mechanical properties of sintered TiAl-NbN composites

Abstract

Unlocking the full potential of intermetallic TiAl alloys in aerospace and automotive engines demands critical attention, as their limitations, particularly due to the room temperature brittle nature, inadequate oxidation and strength beyond 800 °C. Hence, the need to improve the mechanical properties is crucial to expanding their versatile applications. Herein, the effect of Niobium nitride (NbN) addition on the densification, microstructure, and mechanical characteristics of Titanium aluminide (TiAl) was studied. TiAl powders with various concentrations of NbN at 0, 2, 4, 6, 8, and 10 wt.% were synthesized through the spark plasma sintering technique. Each blended composite powder was measured according to stoichiometry into a 30 mm internal diameter graphite die and sintered at a temperature of 1150 °C, a pressure of 50 MPa, a heating rate of 100 °C/min, and a dwell time of 10 mins. The densification phenomenon, phase present, microstructure, and mechanical properties were investigated via Archimedes’ principle, X-ray diffraction (XRD), and Vickers hardness tester, respectively. Results shows that the addition of NbN to TiAl at constant sintering parameters enhanced the mechanical properties of TiAl. The microhardness of the composite material increases as the NbN addition increases, with maximum hardness of 467 HV, and ultimate tensile strength (UTS) up to 1458.9 MPa, attained at 10 wt.% NbN addition. Maximum porosity content of an impressive 1.6% was recorded at the addition of 10 wt.% NbN, which shows exceptional efficiency of spark plasma sintering technique. The results on densification and mechanical properties are presented and discussed with respect to the material composition and processing condition of the sintered materials.