Microstructure and Mechanical Properties of TiAlMoN Coatings Prepared by Arc Ion Plating

The TiAlMoN coatings were deposited by arc ion plating under different substrate bias voltages, and the effects of substrate bias on the composition, phase structure, microstructure, and mechanical properties of the coatings were systematically investigated. The results showed that, as the bias voltage increased from 0 V to −75 V, enhanced ion bombardment promoted coating densification, the N/(Ti + Al + Mo) atomic ratio decreased from 1.33 to 1.05, and the deposition rate increased from 124.7 nm/min to 138.2 nm/min. XRD peak fitting revealed that the TiAlMoN coatings may consist of three phases: c-TiN, fcc Mo-N, and c-AlN. With increasing negative bias voltage, the preferred (111) orientation became more pronounced, while the Mo-N phase gradually evolved from B1-MoN to γ-Mo2N. As the substrate bias voltage increased, the grain size initially reduced and then slightly increased, and the compressive residual stress sharply increased from 0.68 GPa to 2.21 GPa. Owing to coating densification, grain refinement, and increased compressive residual stress, the hardness increased from 16.7 GPa to 33.9 GPa. The adhesion strength reached a maximum of 59.7 N at −25 V and decreased at higher bias voltages because of excessive residual stress. Appropriate control of the substrate bias voltage enables the synergistic optimization of structural strengthening and interfacial stability in TiAlMoN coatings.