Investigation of Adhesion and the Load Bearing of CrN-CrAlN Nanostructured Coating by Physical Vapor Deposition

Nitride coatings with excellent hardness and wear resistance have been deposited by physical vapor deposition (PVD) in recent years. For most applications, the load bearing and adhesion of coatings are very important and can determine the life and performance of the final components. In this study, CrN/CrAlN nanostructured coatings with different thicknesses and numberes of layers were deposited on the stainless steel AISI 420 and hot-work tool steel by cathodic arc evaporation. Nanoindentation, X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) were used for the structural characterization and estimation of stress in the coatings. Adhesion of coatings was evaluated by scratch adhesion and VDI 3198 Rockwell tests. The results revealed the high values of compressive residual stress in the physical vapor deposited coatings, in the range of 500 to 1800 MPa, with a detrimental effect on coating adhesion. Load bearing capacity was observed to be dependent on the thickness and adhesion of coating, reaching the maximum at an optimum thickness. Overall, the results proved that the type of steel substrate could have a significant influence on the coating adhesion.