Quantification of properties modification and cutting performance of (Ti1-xAlx)N coatings at elevated temperatures

Thill, hard, titanium- and aluminium-derived nitride coatings are usually o perated at elevated temperatures. Typical examples are coated tools, applie d in manufacturing especially at high cutting speeds. The operation of coat ings in high-temperature environments may modify their composition and thei r structure, and may negatively affect, among others, their bulk mechanical properties, such as Young's modulus, hardness, fatigue strength, etc. This paper presents a quantitative study of such phenomena, based on experiment al data, derived by the application of the indentation and impact tests, as well as cutting experiments with as-deposited and artificially oxidized co atings. To carry out these tasks, special experimental test rigs have been developed and SEM and EDX investigations have been conducted. Moreover, FEM models were established to support the evaluation of the experimental inve stigations. By means of the aforementioned procedures, a comprehensive stud y of the influence of hard metal (HM) insert coating specifications on the deterioration of their cutting performance was incorporated. Thereby, the e ffects of the film properties. of their oxidation mechanisms as well as of the mechanical stresses occurring during the cutting processes on the entir e film wear behaviour in milling operations were investigated. (C) 1999 Els evier Science S.A. All rights reserved.