Mechanical properties and tribological performance of multilayered AlCrBN/AlTiBN coatings

Hard coatings have advanced considerably, especially with the development of multilayer and multicomponent systems, which have improved performance across various applications, notably in tribological settings. However, in demanding cutting, piercing, and stamping applications that experience intense, repetitive impacts, multicomponent nitride coatings often exhibit brittleness, leading to reduced service life. Adding a ductile layer such as a metal or soft nitride material within multilayer coatings is a common strategy. This approach improves impact resistance by leveraging the synergistic effects of multiple materials, which enhances overall performance, however, it may result in a decrease in hardness. Recent studies have demonstrated that coatings such as AlCrBN and AlTiBN exhibit high hardness and thermal stability compared to AlCrN and AlTiN. This study used a cathodic arc deposition technology to deposit the quaternary AlCrBN, AlTiBN, and multilayer nitride coatings of AlCrBN/AlTiBN. By controlling the cathode current of the evaporation targets and the substrate's rotation, multilayer coatings composed of alternating AlCrBN and AlTiBN layers were produced. This approach enhances adhesion strength between the coating and substrate, as well as improves mechanical properties and tribological performance. Cross-sectional observations using scanning electron microscopy and transmission electron microscopy revealed that the addition of boron in AlCrBN/AlTiBN coatings effectively suppressed grain growth, resulting in fine columnar structures and a nanolayered configuration. The layering technique enabled optimization of each layer's thickness and composition, allowing for tailored properties suited to specific impact fatigue applications. As a result, the AlCrBN/AlTiBN coating, with AlTiBN and AlCrBN layers measuring 6.5 nm and 16.7 nm respectively, achieved high hardness (37.9 GPa) and the lowest wear rate (8.7 +/- 2.3 x 10(-7) mm(3)/Nm). In addition, the multilayer AlCrBN/AlTiBN also demonstrated improved crack resistance and resistance to plastic deformation after undergoing 700,000 reciprocating impacts, and it showed to be advantageous impact fatigue resistance.