Investigations on temperature-activated coatings for friction reduction during turning of titanium alloys
The application of high performance titanium alloys enables great advancement in many sectors of the industry. These materials offer good mechanical, thermal and chemical properties. Application areas of the most widely used titanium alloy TiAl6V4 are in medical technology (implants) in the automotive sector (connecting rods, valves, turbocharger), in the plastic industry (nozzles for injection), in the chemical industry (stirring elements, valves), in power engineering (turbine blades) and in the aerospace industry (engine and suspension parts). The outstanding properties of this material difficult but at the same time its machining. Compared to steel materials, TiAl6V4 exhibits a high temperature resistance up to T = 550 ° C and low thermal conductivity (λ = 5.8 W/mK) as well as a pronounced tendency to strain hardening and an abrasive effect. The poor thermal conductivity leads to high chip temperatures und the process heat flows for the most part in the tools and is not transported through the chip. Another consequence is the development of chemical reactions at the tool surface due to the high process temperature. For the machining of these materials, this means that the tools are subject to a considerable thermal stress and a high mechanical load. Therefore, the production of complex components made of titanium alloys by cutting process is economically not possible due to the fact that this material causes high tool wear, which is associated with high costs. The use of hard coatings deposited by PVD (physical vapour deposition) process for tuning of titanium alloys are not established in the industry. The reason for this is that the corresponding load collective is so far insufficiently researched and the chemical and physical cause-effect relations between titanium and coated tools are not yet understood. The aim of this cooperation research project between IOT and IPMT is the production of temperature active (Cr,Al,V)N coating systems by a combination of dcMS (direct current magnetron sputtering) and HPPMS (high power pulsed magnetron sputtering) technology as well as the investigation of physical and chemical cause-effect relations between coatings and TiAl6V4 and the description of the thermal and mechanical loads during turning of titanium alloy with coated cemented carbide tools. The results of this research project will contribute to make an economical cutting process for titanium alloys possible.