Tuning bilayer period of AlN/CrN superlattice coatings deposited using cathodic arc technique for superior mechanical properties and thermal stability

Abstract

In the present work, a comprehensive study on the effect of the bilayer period on the mechanical properties of AlN/CrN superlattice coatings deposited using the cathodic arc technique is reported. AlN/CrN superlattice structures with different individual layer thicknesses (3.5/4.5, 3.5/3.5, 3.5/3.0, and 6.0/3.0 nm) were prepared by varying Cr and Al target currents. The total thickness of coatings was in the range of 2.00 to 2.55 μm. XRD, TEM, EDS, and SEM techniques were employed for structural, compositional, and morphology studies. Hardness (H) and Elastic Modulus (E) of the samples were determined using the nano-indentation method. It was observed that AlN3.5/CrN3.5 coating exhibit higher hardness and elastic modulus than other samples. Thickness and wear rate measurements were carried out using the micro-abrasion Calo-test. Thermal stability of the AlN/CrN coatings was studied by annealing at elevated temperatures ranging from 800 °C to 1000 °C in the air for 2 hrs. It has been concluded that 2 μm thick AlN/CrN superlattice coating with low surface roughness having bilayer period of 6.5 nm with AlN thickness of 3.5 nm, and overall Al concentration of 30 at% will display better wear resistance, plastic deformation resistance, adhesion, and thermal stability.

Keywords

• Bilayer period
• Superlattice coating
• AlN/CrN hard coating
• Cathodic arc technique
• Mechanical properties
• Thermal stability