Machining and forming tools exposed to challenging environments require protective coatings to extend their lifetime and reliability. Although transition metal nitrides possess excellent strength and resistance against chemical attacks, they lack ductility and are prone to premature failure. Here, by investigating structural and mechanical properties of MoN-TaN superlattices with different bilayer thickness, we develop coatings with high fracture toughness and hardness, stemming from the formation of a metastable tetragonally distorted phase of TaN up to layer thicknesses of 2.5 nm. Density functional theory calculations and experimental results further reveal a metal-vacancy stabilized cubic Ta_0.75N phase with an increased Young’s modulus but significantly lower fracture toughness. We further discuss the influence of coherency strains on the fracture properties of superlattice thin films. The close interplay between our experimental and ab initio data demonstrates the impact of phase formation and stabilization on the mechanical properties of MoN-TaN superlattices.

暴露于挑战性环境中的加工和成型工具需要保护涂层以延长其使用寿命和可靠性。尽管过渡金属氮化物具有出色的强度和抵抗化学侵蚀的能力，但它们缺乏延展性并且易于过早失效。在这里，通过研究具有不同双层厚度的MoN-TaN超晶格的结构和机械性能，我们开发出具有高断裂韧性和硬度的涂层，这是由于形成了TaN的亚稳态四方畸变相直至层厚为2.5 nm。密度泛函理论计算和实验结果进一步揭示了金属空位稳定的立方钽_0.75N相的杨氏模量增加，但断裂韧性明显降低。我们进一步讨论相干应变对超晶格薄膜断裂特性的影响。我们的实验数据和从头算数据之间的密切相互作用表明，相形成和稳定化对MoN-TaN超晶格的力学性能有影响。