Diffusion wearTi555.3 alloy Ti6Al4V alloy a b s t r a c t Near-beta titanium alloys like Ti555.3 are increasingly being used in aeronautics replacing in some critical applications the most common Ti6Al4V. However, these near-beta titanium alloys have a poor machinability rating which needs to be overcome so as to maintain at least the same productivity levels as in Ti6Al4V.This paper presents the machinability results carried out for Ti555.3 compared with the commonly used Ti6Al4V. The aim of this research work is to understand tool wear mechanisms when machining Ti555.3. Analysis of variables such as cutting forces, chip geometry and tool wear shows that: (I) greater difficulty is encounterd when machining Ti555.3 alloy compared with Ti6Al4V alloy which can be machined at higher speeds up to 90 m min −1 ; (II) there was a correlation between the mechanical properties of work material, tool wear, and component forces; (III) the occurrence of the diffusion process leads to the formation of a layer of adhered material composed of Ti and TiC on the tool's rake face for both Ti alloys.

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Nickel based alloys are extensively used in the aerospace industry due to the excellent corrosion resistance and high mechanical properties that are maintained up to elevated temperatures (600-800 °C). However, these superalloys are classified as difficult-to-cut and therefore modelling and simulation of the machining processes has become a key in the machinability assessment of nickel based alloys. The reliability of Finite Element Models (FEM) largely depends on the quality of input parameters, one of the most relevant being the constitutive material model representing work material behavior under high strain, strain rate and tempera-tures.In order to develop a reliable material model, the present work deals with a complete characterization of Inconel 718. Uniaxial compression tests at testing temperatures close to those found in machining (21-1050 °C) and high strain rates (10°−10 2 s −1 ) were performed on the Gleeble 3500 testing machine. Moreover, the microstructural analysis and microhardness measurements of the testing samples were performed, in order to correlate the microstructural state with the mechanical properties of the Inconel 718. Based on this experimental work, a new coupled empirical model is proposed to describe the particular behaviour of nickel based alloys at elevated temperatures and high strain rates. This material behaviour model introduces softening phenomena as well as the coupling between the temperature and the strain rate known to occur experimentally, for machining FEM simulations with Inconel 718 superalloy.

This is a repository copy of Ti6Al4V metal cutting chip formation experiments and modelling over a wide range of cutting speeds.

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