Thermal stability and mechanical properties of (Al,Cr,Ti,Si,Y)N multielement nitride coatings after annealing

Although AlTiN is the preferred hard-coating material for cutting tools, its limited thermal stability causes problems at high cutting temperatures. Multielement nitride coatings such as AlCrN coatings doped with Si, W, and Y lead to the enhanced hardness and thermal stability of cutting tools. In this study, (Al,Cr,Ti,Si,Y)N multielement nitride coatings were fabricated via multiarc ion plating from an AlCrTiSiY alloy target and vacuum annealed at various temperatures. The surface morphologies, crystal structures, mechanical properties, and wear performances of the samples were analyzed. The number of surface defects on the (Al,Cr,Ti,Si,Y)N coatings reduced as the treatment temperature increased to 1000 °C, but the number of these defects increased at higher temperatures. X-ray diffraction revealed a phase transition from the face-centered cubic structure to wurtzite-AlN of the (Al,Cr,Ti,Si,Y)N coatings after annealing at 1100 °C; the same phase transition was observed at 900 °C in (Al,Ti)N coatings, which were prepared for comparison. Nanoindentation tests revealed that the hardness of the (Al,Cr,Ti,Si,Y)N coatings peaked at 40.81 GPa after annealing at 900 °C and remained high (33.73 GPa) even after annealing at 1100 °C. Meanwhile, the hardness of the (Al,Ti)N coatings markedly decreased after annealing at 800 °C. Friction tests revealed stable wear resistance of the (Al,Cr,Ti,Si,Y)N coatings with a wear rate of ∼2 × 10−6 mm3/N·m after annealing at 1000 °C. The wear rate nearly doubled to ∼3.75 × 10−6 mm3/N·m at 1100 °C. Overall, the (Al,Cr,Ti,Si,Y)N coatings demonstrated improved thermal stability than the (Al,Ti)N coatings, showing promising potential for demanding high-temperature applications.