Structure and wear mechanisms of nano-structured TiAlCN/VCN multilayer coatings

Dry sliding wear of transition metal nitride coatings usually results in a dense and strongly adhered tribofilm on the worn surface. This paper presents detailed electron microscopy and Raman spectroscopy characterizations of the microstructure, a newly developed multilayer coating TiAlCN/VCN and its worn surface after pin-on-disc sliding wear against an alumina ball. The friction coefficient in a range of 0.38–0.6 was determined to be related to the environmental humidity, which resulted in a wear coefficient of the coating varying between 1017 and 1016 m3 N1 m1. TEM observation of worn surfaces showed that, when carbon was incorporated in the nitride coating, the formation of dense tribofilm was inhibited

Inverse determination of constitutive equations and cutting force modelling for complex tools using oxley's predictive machining theory

In analysis of machining processes, finite element analysis is widely used to predict forces, stress distributions, temperatures and chip formation. However, constitutive models are not always available and simulation of cutting processes with complex tool geometries can lead to extensive computation time. This article presents an approach to determine constitutive parameters of the Johnson-Cook's flow stress model by inverse modelling as well as a methodology to predict process forces and temperatures for complex three-dimensional tools using Oxley's machining theory. In the first part of this study, an analytically based computer code combined with a particle swarm optimization (PSO) algorithm is used to identify constitutive models for 70MnVS4 and an aluminium-alloyed ultra-high-carbon steel (UHC-steel) from orthogonal milling experiments. In the second part, Oxley's predictive machining theory is coupled with a multi-dexel based material removal model. Contact zone information (width of cut, undeformed chip thickness, rake angle and cutting speed) are calculated for incremental segments on the cutting edge and used as input parameters for force and temperature calculations. Subsequently, process forces are predicted for machining using the inverse determined constitutive models and compared to actual force measurements. The suggested methodology has advantages regarding the computation time compared to finite element analyses.BMBF/02PN205

Performance of nano-structured multilayer PVD coating TiAlN/VN in dry high speed milling of aerospace aluminium 7010-T7651

A low-friction and wear resistant TiAlN/VN multilayer coating with TiAlN/VN bilayer thickness 3 nm has been grown by using the combined cathodic arc etching and unbalanced magnetron sputtering deposition on high speed steel tools for dry cutting of aluminium alloys. In this paper, in-lab and industrial high speed milling tests have been performed on an aerospace aluminium alloy 7010-T7651. The results show that the TiAlN/VN coated tools achieved lower cutting forces, lower metal surface roughness, and significantly longer tool lifetime by three times over the uncoated tools as a result of the low friction and eliminated tool-metal adhesion. Under the same conditions, a TiAlN based multicomponent coating TiAlCrYN also increased the tool lifetime by up to 100% despite the high cutting forces measured

FlexCAR – eine autonome Fahrzeugforschungsplattform der Zukunft

FlexCAR ist ein öffentlich gefördertes BMBF - Forschungsprojekt, in welchem zwölf Verbundpartner aus Industrie und Wissenschaft zusammenarbeiten. FlexCAR ist eines von vier Leitprojekten der ARENA 2036 und läuft bis 09/2023. Das FlexCAR mit seiner standardisierten, autonomen Fahrzeugplattform für die Mobilität von morgen fungiert als Forschungsdemonstrator. Neue Technologien können nach dem Plug-and-Play-Prinzip unmittelbar aus dem Forschungsstadium implementiert werden, was eine frühzeitige Validierung im Hinblick auf künftige Anwendungspotentiale ermöglicht. Offene Soft- und Hardwareschnittstellen sind hier berücksichtigt, beziehungsweise werden weiterentwickelt. Das FlexCAR besteht aus drei modularen Komponenten: zwei Drive-Module und eine Energy-Modul. Das Energy-Modul kann mit Batteriespeichern, oder wahlweise mit Brennstoffzellenstacks bestückt werden. Die wesentlichen Fahrfunktionen werden durch einen elektrischen Allradantrieb und zwei gelenkte Achsen ermöglicht. Verschiedenartige Sensoren sind am FlexCAR verbaut und dienen der Automatisierung, als auch der Steuerung via Smartphone. Eine Positionsbestimmung erfolgt beispielsweise über 5G-Lokalisierung bzw. Sattelitennavigationssysteme, oder der Anbindung von Infrastruktur-Sensoren. Ex- und Interieur der Fahrgastzelle werden im Projekt cyberphysisch in Mixed Reality (Virtual Reality + echte, physische Objekte) dargestellt. Zwei Bodenplattenaufbauten mit integrierten Schienen für Sitze können auf die Plattform aufgesetzt werden, um somit neue „Mobile Working“-, sowie „Private“- Konzepte (cyber-)physisch untersuchen zu können. Das FlexCAR ist von seinem Forschungsansatz als ein UseCase-gesteuerter, offener Demonstrator aufgebaut, an welchem je nach gewünschtem UseCase wettbewerbs- und baureihenunabhängig in einem sehr frühen Forschungsstadium flexibel Forschungsarbeiten und Validierungen durchgeführt werden können

Structure evolution and Properties of TiAlCN/VCN Coatings Deposited by Reactive HIPIMS

2.5 µm thick TiAlCN/VCN coatings were deposited by a reactive High Power Impulse Magnetron Sputtering (HIPIMS) process. Cross-sectional TEM showed gradual evolution of the structure of the coating with thickness. The initial structure is a nanoscale multilayer with sharp interlayer interfaces. This transforms to nanocomposite of TiAlCN and VCN nanocrystalline grains surrounded by a C-rich tissue phase and finally changes to an amorphous carbon rich Me-C phase. In contrast deposition in similar conditions using standard magnetron sputtering produces a well-defined nanoscale multilayer structure. Depth profiling by AES showed that the carbon content in the HIPIMS coating gradually increased from 25% at the coating substrate interface to 70% at the top thus supporting the TEM observations. Energy-resolved mass spectrometry revealed that HIPIMS plasma is a factor of 10 richer in C1+ ions, and therefore more reactive, as compared to the plasma generated by standard magnetron discharge at the same conditions. The peculiar structure evolution in HIPIMS is discussed in relation to target poisoning effect and carbon outward diffusion during coating growth. Highly abrasive AlSi9Cu1 alloy was dry machined using TiAlCN/VCN coated 25 mm diameter end mills to investigate the coating-work piece material interaction. Green (532nm excitation) and ultraviolet (325 nm excitation) Raman spectroscopy was employed to identify the phase composition of the built up material on the cutting edge and chip (swarf) surfaces produced during machining. These analyses revealed formation of lubricious Magnèli phases namely V2O5 and graphitic carbon as well as highly abrasive SiO2 and mixed (AlSi)O thus shedding light on the wear processes and coating tribological behaviour during machining