Adhesive-deformation relationships and mechanical properties of nc-AlCrN/a-SiNx hard coatings deposited at different bias voltages

Abstract

A series of Al-Cr-SiN hard coatings were deposited on WC-Co substrates with a negative substrate bias voltage ranging from-50 to-200 V using cathodic arc evaporation system. A Rockwell-C adhesion test demonstrated that excellent adhesion was observed at lower bias voltages of-50 V and-80 V, while further increases in bias voltage up to-200 V led to severe delamination and worsening of the overall adhesion strength. X-ray diffraction and transmission electron microscopy analysis revealed a single phase cubic B1-structure identified as an AlCrN solid solution with a nanocomposite microstructure where cubic AlCrN nanocrystals were embedded in a thin continuous amorphous SiNx matrix. Coatings exhibited a 002-texture evolution that was more pronounced at higher bias voltages (≥-120 V). Stress-induced cracks were observed inside the coatings at high bias voltages (≥-150 V), which resulted in stress relaxation and a decline in the overall residual stresses.

Structure, Morphology, and Mechanical Properties of AlCrN Coatings Deposited by Cathodic Arc Evaporation

“…Many authors indicate that for AlCrN coatings with hexagonal phase of AlN the mechanical properties are deteriorated ( Ref 8,42,43,57). Indeed, hardness in investigated coatings is lower for about 50-100% compared to coatings with cubic AlN phase (Ref 9, 29).…”

Effect of Plasma Nitriding Pretreatment on the Mechanical Properties of AlCrSiN-Coated Tool Steels

“…Class 1 shows no adhesive delamination; adhesion is acceptable. In the cases of class 2 and class 3, adhesion is unacceptable [39]. Adhesive delamination is defined as a removal of the coating, whereby the underlying substrate can be clearly seen, or a removal of one or more sublayers in a multilayered or graded coating, whereby the substrate or an underlying sublayer can be clearly distinguished.…”

Comparative Investigations of AlCrN Coatings Formed by Cathodic Arc Evaporation under Different Nitrogen Pressure or Arc Current

“…The transformation of c-AlN → h-AlN occurs spontaneously and irreversibly. The coatings containing the AlN phase with a cubic structure (c-AlN) are characterized by better mechanical properties than the hexagonal AlN (h-AlN) phase [ 20 , 21 ]. Therefore, in order to obtain the coating with fcc structure and good mechanical properties, i.e., high hardness and good resistance to wear, the aluminum concentration in the coating ought to be attended to.…”