Coatings of 3 μm CrN and TiN were prepared by a magnetic filtered cathodic vacuum arc process (MFCVA) on Ti-6Al-4V substrates, respectively. Rotating bending tests and uniaxial tests were conducted for investigating the effect of the thin and uniformly distributed hard CrN and TiN coatings on the fatigue and mechanical properties of Ti-6Al-4V substrate. During both tests, no coating spallation phenomenon was observed, which indicated that the hard coating bound well with the substrate. The fatigue test results showed that the fatigue strength of the coated sample was decreased in both the low- and high-cycling fatigue regimes compared with the uncoated Ti-6Al-4V substrate. Compared with the TiN coating, the CrN coating caused a more significant reduction on the fatigue property of the uncoated Ti-6Al-4V substrate due to its inferior plastic deformation capacity. Furthermore, the tensile test results showed that the coated sample had a relative higher ultimate strength, yield strength, and lower elongation compared with the uncoated Ti-6Al-4V substrate. This may be due to the fact that the hard coating could suppress the initiation of cracks, and so higher stress was needed for crack initiating. During the crack propagation period, the hard coating cracked at a relative higher velocity, which led to cracking of the ductile substrate and elongation reduction.

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Atomic structure, adhesion energy, and electronic properties of the bonding nature at CrN(200)/Ni(111) interfacial region are studied by first‐principle calculations based on density functional theory (DFT). A new method for building the heterostructure of CrN(200)/Ni(111) is proposed to solve the large lattice mismatching between CrN(200) and Ni(111) slab. Three models (OT, ST, and TL) with different interface distance are built up, and the total energy for each of them is calculated. Comparing with other stacking sequence, TL sites with 1.9‐Å spacing at the interfacial region shows the biggest value of adhesion energy after geometry relaxation. Furthermore, the contour of charge density, partial charge density of states, and Bader charge values of the TL sites with 1.9‐Å spacing are plotted out and calculated. Results indicate that covalency bonding between Ni and N ions and metallic bonding between Ni and Cr atoms are formed at the interfacial region.