Synthesis of Nb₃Al high temperature intermetallic compound by laser deposition

Refractory intermetallic compound Nb₃Al is expected as a candidate for structural materials operated at much higher temperatures compared to conventional Ni superalloys. This paper presents research work on laser deposition of a powder blend of Nb, Ti, Al pure elements to form Nb₃Al intermetallic compound. The research focuses on an alloy composition of Nb-12Ti-22Al (at.%). The fine δ-Nb₃Al/β-Nb_ss intermetallic compound with a composition close to the atom ratios of the elemental powder blend was obtained by laser deposition in an argon atmosphere chamber. The microstructure characterization and phase identification were analyzed by XRD, SEM and TEM. The fine δ/β compound has an average microhardness up to HV_0.21022. Although Nb₃Al has a negative formation enthalpy, high laser energy density is needed for Nb₃Al formation by peritectic reaction. There is a critical crack-free height in laser deposition of Nb₃Al under appropriate processing parameters. Beyond the height, the sample cracks due to residual tensile stress induced during laser deposition.