composite layer-based analytical models for tool–chip

Journal of Materials Processing Technolog y 176 (2006) 102–110 Composite layer-based analytical models for tool–chip interface temperatures in machining medium carbon steels with multi-layer coated cutting tools W. Grzesik ∗ Department of Manufacturing Engineering and Production Automation, Technical University of Opole, P.O. Box 321,45-271 Opole, Poland Received 6 April 2004; accepted 20 February 2006 Abstract This investigation is devoted to the thermal problems in dry orthogonal turning of a C45 medium carbon steel with natural contact tools treated with multi-layer coatings with an intermediate Al 2 O 3 layer . New hybrid analytical models for estimating heat partition to the chip and the tool–chip interface temperatur es were proposed. Furthermore, the physics-based modelling concept, which applies composite layer approach was developed to estimate the average and maximum steady-state tool–chip interface temperatures in orthogonal turning. The model predictions were compared to appropriate experimental process data using natural tool-work thermocouples and other simulated and measured literature data. It was verified that the models proposed yield accurate average temperatures and estimate their maximum values for uncoated and two multi-layer coated tools for cutting speeds r anging from 90 to 240 m/min. © 2006 Elsevier B.V. All rights reserved. Keywords: Machining; Coated carbides; Interface temperature; Analytical modelling 1. Intro ductio n The often used combination of higher cutting speeds (HSC) with dry process conditions and demands on high performance cutting (HPC) require cutting tools with special heat-protected coatings due to severe tribological influences [1,2]. In order to improve the heat isolating effect multi-layer coatings have first been synthesized to combine the beneficial properties of various ceramic materials, such as TiC, TiN, TiCN and Al 2 O 3 [3,4]. Another trend observed is the transition to complex and more wear -resi stan ce CVD-A l 2 O 3 -based coati ngs with con- troll ed deposition of -Al 2 O 3 or -Al 2 O 3 . At present, TiAlN plays an increasingly important role in the design of advanced PVD coati ngs. The exce llent performanc e of commercial ly available TiAlN coated tools, confirmed by a great number of published experimental data, results from the higher hot hardness and oxidation resistance of these hard materials at elevated temperatures [3,5]. Moreover, improved TiAlCrN or TiAlCrYN coatings, including multi-layering with CrN and incorporation ∗ Tel.: +48 77 4006290; fax: +48 77 4006342. E-mail address: [email protected] . of yttrium, significantly outperform the commercial ones [6]. Recently, the metastable solution phase (Ti,Al)N in cubic NaCl (B1) structure, named as supernitrides, with a superior oxidation resistance and hardness under both dry and high speed (up to 600m/min) mac hin ing con ditions has been lau nch ed [7]. It is clear that the determination of the exact temperature rise in the tool–chip interface has been recognized as an important study in achieving the best cutting performance. For the above reason, an est ima tio n of the hea tin g and temperature his tor ies on the rake face of cutting tools is necessary. Another approach is to assess the steady-state temperatures (average and maximum temperature responses) developed rapidly at the first stage of machining. In this case study the steady-state temperature prob- le m was solv ed in su ch a wa y that heat flux co mpon ents an d he at par tit ion ing are estimated by minimi zin g the dif ferenc e betwee n the modelled and the corresponding measured temperatures. In particular, a few different formulae for the heat partition coef- ficient for sliding bodies with defined thermal properties and the composite (equivalent) layer concept are employed. In prac- tice, the two characteristic values of the interface temperature allow to evaluate prevailing sources of the tool failure, i.e. pre- sumable reduction of its hardness resulting from the thermal 0924-013 6/$ – see front matter © 2006 Elsevier B.V . All rights reserved. doi:10.1016/j.jmatprotec.2006.02.025

composite layer-based analytical models for tool–chip

Documents