Advanced studies of microstructure-property relationship of Cr-Al-N mono- and multilayers for improved tribological performance in combustion engines

Abstract

CrN and CrAlN films are widely used in piston rings in order to improve their working performance in combustion engines. This extensive use is corroborated by their good oxidation resistance, elevated hardness, chemical inertness and wear resistance. The combination of all of these properties is highly attractive for applications in tooling, automotive, aerospace and decorative industries. Nowadays, increased mechanical and thermal properties of monolithically grown CrN coatings can be achieved by solid solution with different elements, such as Al.PVD methods for the deposition of mono- and multi-layers of the Cr-Al-N allow for generating a variety of microstructures that are significant for the mechanical and tribological performance of coating systems. In particular, chemical compositional profiles, grain size distribution, coating architecture, residual/thermal stresses and crystallographic textures allow for optimizing the mechanical properties and the tribological performance of Cr-Al-N-based coatings. The aim of this project is therefore to contribute to the understanding of how specific DC-MS and HiPIMS deposition parameters determine selected microstructures and mechanical properties with special interest in the tribological performance/response of Cr-Al-N-based coatings. The Cr-Al-N-based mono- and multi-layers obtained by DC-MS and HiPIMS methods will be deposited on stainless steel substrates and compared. Stainless steels are chosen due to their diversity of applications such as dies, engines and cutting tools. The microstructures produced by distinct PVD routes will be characterized using advanced tools, such as GDOES, TKD, EBSD, STEM, FIB-SEM-EBSD-tomography and synchrotron XRD. For assessing the mechanical and tribological properties, stress analyses will be performed using XRD and ball-on-disc wear and friction tests will be conducted at room and high temperature as well as in erosive-corrosive environments.