Wear Mechanisms of (Cr,Al,Y)N PVD Coatings at Elevated Temperatures

Abstract

Over the past years there have been developments in machining operations to replace the use of liquid cooling by dry cutting operations. This results in higher loads for the tools and therefore demands the continuous development of surface coatings. (Cr,Al,Y)N‐coatings designed at the Institute of Materials Technology in Darmstadt, Germany, show beneficial tribological properties especially at high loads and high temperatures. Samples of different yttrium content have been distinguished and compared to an industrial TiAlN coating. Even though the configuration of the (Cr,Al,Y)N coatings is not yet as optimised as that of the TiAlN, which leaves plenty of room for improvement, the (Cr,Al,Y)N shows comparable and partly superior properties to the TiAlN coating. An increasing yttrium content of the (Cr,Al,Y)N leads to a more amorphous microstructure and to finer and denser morphology with a smoother surface. The TiAlN, in contrast, exhibits a porous, columnar structure. This results in advantages in the wear behaviour as well as in the oxidation resistance. Furthermore, a distinct improvement of the adhesion of the layer to the carrier is determinable, which results in higher sustainable loads at the scratch test.

Modern materials for forming and cutting tools – overview

“…However, this reduced the use of cooling lubricants causes a strong increase in the forces applied to the cutting tool in operation. A very effective way to protect the cutting edge from thermal, abrasive and tribo-oxidative attack is by depositing PVD coatings to the tool surface [30,31,32]. As these only a few microns thick coatings significantly govern the effectiveness and productivity of the machining operation it is necessary to optimize these protective coatings.…”

Investigation of the Properties of Multilayer Nanostructured Coating Based on the (Ti,Y,Al)N System with High Content of Yttrium

“…The temperature of the onset of active oxidation of the (Nb,Y)N coating, which was 500 • C for a system without the addition of yttrium, increases to 760 • C at a Y content of 12.1 at.% [13]. An increase in the yttrium content in the nitride coating leads to the formation of an amorphous microstructure with a finer and denser morphology and a smoother surface [14].…”

Influence of the Ti-TiN-(Y,Ti,Al)N Nanolayer Coating Deposition Process Parameters on Cutting Tool Oxidative Wear during Steel Turning

“…As the Y content increases, an amorphous yttrium oxide phase also forms. With increasing yttrium content, hardness and fracture toughness increased and the friction coefficient decreased [23][24][25]. The (Al,Cr,Y)N coating provides tool cutting properties that are superior to those of tools with a commercial (Ti,Al)N coating [24,25].…”