High temperature thermodynamics of spinodal decomposition in arc deposited TixNbyAlzN coatings

Abstract Using first principles calculations and experimental methods we show that B1 structured solid solution Ti x Nb y Al z N can be grown. The mixing free energy surface indicates that the alloys should decompose. Theoretical analysis of the thermodynamic driving force towards the spinodal decomposition shows that the force can be different in alloys with equally low thermodynamic stability but different Nb content, indicating that the detailed picture of the decomposition should also be different. Electron microscopy and nanoindentation underlines different age hardening of the samples. We demonstrate that an alloy with the optimized composition, Ti 0.42 Nb 0.17 Al 0.41 N combines high thermal stability and age hardening behavior.