Correlation between constitution, properties and machining performance of TiN/ZrN multilayers

A concept for wear protective coatings on saw blades for metal cutting applications based on nanoscale titanium nitride/zirconium nitride (TiN/ZrN) multilayers is presented, which comprises the adjustment of columnar morphology for the cavities between the columns being used as a reservoir of cooling lubricants. The challenge consisted in optimizing the deposition conditions such that adhesion is increased to values that are normally reached by a compact morphology only (critical load of failure in the scratch test >40 N). Nanoscale TiN/ZrN multilayer were deposited by reactive dc-magnetron sputtering of metallic titanium and zirconium targets in argon/nitrogen plasma. These multilayers are a model system for a comprehensive characterization of both multilayers and their interfaces from the micrometer down to the nanometer-scale to correlate their constitution (X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM)), their properties (hardness: 2000–2600 HV0.015, reduced elastic modulus: 330–420 GPa, internal stress <1 GPa, critical load of failure in the scratch test: 30–85 N) and their performance in cutting screws made of freecutting steel of quality 11SMnPb30 (AISI 12L13, DIN 1.0718) at a cutting speed of 125 mm/min with coated high speed steel (HSS) saw blades (AISI M2, DIN 1.3343). In addition, the small angle cross-section method was developed for use in depth-resolved investigations of mechanical properties of multilayers and first results will be presented.