Design of cycle structure on microstructure,mechanical properties and tribology behavior of AlCrN/AlCrSiN coatings

AlCrN/AlCrSiN coatings with cycle structure, composed of fcc-CrN, hcp-AlN and amorphous Si₃N₄ phases, were fabricated to protect high speed steel (HSS) tools by high energy ion source enhanced multi-arc ion plating technology with Al₇₀Cr₃₀ and Al₆₀Cr₃₀Si₁₀ alloying targets. With the increasing cycle structure, the crystal grains of AlCrN layers was refined from 60–110 nm to 8–15 nm, and the growth behavior transformed from (200)fcc to the coexistence of both (200)fcc and (111)fcc preferred orientation as demonstrated by GIXRD spectrum, calculated texture coefficient and HRTEM results. The HRTEM results investigated that the inter-planar spacing of CrN(111) was basically equal to that of AlN(0002) with parallel orientation relationship and the interface-1 between the substrate and adhesion layer with a semi-coherent appearance presented a specific orientation relationship. The coating with two cycle structure (Cycle 2) possessed better adhesion strength (HF1 grade, 62.7±1.3 N of Lc2), higher hardness (30.2±1.7 GPa), better fracture toughness (0.099 of H/E, 0.29 GPa of H³/E² and 9.8±0.3 MPa m^1/2 of K_IC under 20 kgf loading), lower friction coefficient (0.54), less wear rate (4.2 × 10^?16 m³/N·m) and longer service life (7.4 m).