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 m1/2 of KIC 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).