Hard and tough AlTiCrNiMo heterostructure high-entropy film deposited by arc ion plating method

Recently the heterostructure high-entropy alloy films (HEF), which normally exhibits better strength and ductility than single-phase HEF, have been paid much attention. In the present study, a heterogeneous-structure AlTiCrNiMo HEF was deposited on TC4 alloys by arc ion plating method. The advanced characterization techniques were utilized to investigate microstructure, mechanical performance and tribological properties of obtained HEF in very systematic manner to provide a comprehensive evaluation. Microstructural examination revealed that as-deposited film contained three types of structures: MoTi spherical compound covered with an amorphous layer and two kinds of disordered solid solutions (the laminar region and dark matrix). Meanwhile, the HEF showed excellent mechanical performance, including a high hardness of ∼11.2 GPa and a low wear rate of ∼1.2 × 10−5 mm3/(N m) against Al2O3 counterpart in open air conditions, which could be owing to the solution strengthening phenomena resulting from the severe-lattice-distortion effect of high-entropy alloy. Additionally, the HEF showed a good resistance to crack damage. The high fracture toughness was achieved because of heterogeneous structure having hard/soft phases present in the film, which exhibited an effective stress-shielding effect and suppressed the propagation of cracks. •A heterogeneous-structure AlTiCrNiMo film is prepared by arc ion plating.•The film shows high hardness, good toughness and excellent wear resistance.•Heterogeneous structure exhibits a stress-shielding effect against crack damage.